project_final 6.1

Bachelor of Engineering in Mechanical Engineering and Renewable Energy, Year 3

Laboratory Analysis of a Flat-Plate Solar Thermal Collector

By

GROUP PLATINUM

Comprising of:

Antonio Escrivá Salvador

Alexander Ivanov

Alejandro Blay Orenga

Barry Beglan

DR. Niall Burke, Advisor


Athlone Institute of Technology

June 2014


AcknowledgmentsAs a project team, we would like to thank all the people who helped us during the project. Our supervisor, Niall Burke, was of great help throughout the project and his help and guidance was greatly appreciated. The next group of people that helped us a great deal during the course of the project were the technicians in the trades building located in the east campus. The next group of people whose help was greatly appreciated was the staff at Heavins Hardware Store. The technicians here in the engineering building were also very helpful in helping the group complete the project.

AbstractThis project has been focused on flat-plate collectors in the solar thermal sector. The price of the electricity and fuels has been rising in the few last years and it this will continue to happen. For example, the electricity price increased by 17% in Ireland or by 56% in Spain since 2005 (Sustainable Energy Authority ofIreland , 2013).

Figure 1 Household Electricity Price (Sustainable Energy Authority of Ireland , 2013)

The electricity or fuel needed to obtain hot water is relatively big so it is a good idea to use the solar water heating systems to effectively obtain “free” hot water.

The project consists of the efficiency of the solar flat-plate panel in different conditions. An auxiliary system simulating a real circuit used in homes has been built. It consists of two different circuits, the first one will be heated by the solar thermal collector and the second one will supply this heat to a copper cylinder

i


which will heat the water inside. During the course of the project different elements of flat-plate solar collectors will be studied. In the literature review about this topic, the efficiency, the temperature in the different parts of the circuit and the time needed for the tank to arrive at the required temperatures will be obtained for the flat-plate collector and the results will be collected and analyzed.

ContentsAcknowledgments................................................................................................ i

Abstract................................................................................................................ i

Nomenclature.....................................................................................................vii

Chapter 1: Introduction........................................................................................1

1.1: European Solar Thermal Sector................................................................2

1.2: Irish Solar Thermal Sector:.......................................................................2

1.3: Project Aims..............................................................................................3

1.4: Project Objectives.....................................................................................3

1.5: Project scope............................................................................................3

1.6: Project budget...........................................................................................4

1.7: Project methodology.................................................................................4

Chapter 2: Literature Review...............................................................................5

2.1: Weather in Ireland........................................................................................5

2.2: Strengths and weaknesses of solar systems............................................8

2.2.1: Strengths............................................................................................8

2.2.2: Weaknesses.......................................................................................8

2.4: Feasibility of installing solar thermal panels in Ireland..............................9

2.8: Natural circulation and forced circulation................................................10

2.5: Selection of the Solar Collector Type......................................................10

2.5.1: Flat plate solar collectors..................................................................10

2.5.2: Evacuated tube solar collectors:.......................................................13

ii


2.5.3: Cost:.................................................................................................14

2.5.4: Size:..................................................................................................14

2.5.5: Life Spam:.........................................................................................14

2.5.6: Payback Periods:..............................................................................15

2.5.7: Installation:........................................................................................15

2.5.8: Useful Climates.................................................................................15

2.5.9: Orientation........................................................................................15

2.5.10: Efficiency:.......................................................................................16

2.5.11: Conclusion:.....................................................................................16

2.6: Calibration for the project........................................................................16

2.6.1: Thermocouple......................................................................................16

2.7.4: Flow meter...........................................................................................20

2.7.1: Circulating pump..................................................................................23

2.7.6: Radiometer...........................................................................................26

Chapter 3: Materials & Methods:.......................................................................27

3.1.2: Circulating pump...............................................................................28

3.1.3: Thermocouple...................................................................................29

3.1.4: Hot water tank...................................................................................30

3.1.5: Flow meter........................................................................................31

3.1.6: Copper and plastic pipes..................................................................32

3.1.7: Valves...............................................................................................33

3.1.8: Pressure Valves................................................................................33

3.1.9: Insulation..........................................................................................34

3.1.10: Expansion tank vessel....................................................................34

3.1.11: Panel with the lights........................................................................35

3.1.12: Radiometer.....................................................................................36

3.2: Methods..................................................................................................37

3.2.1: Procedure: for original system.........................................................37

3.2.2: Analysis For the original system.......................................................37

3.2.3: Procedure: for the new system.........................................................39

Chapter 4: Results.............................................................................................40

4.2: Original system.....................................................................................41

4.2.1 Results...............................................................................................41

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4.2.2 Calculation of thermal efficiency for the original system....................43

4.2.3: Conclusion for the Original System...................................................46

4.3 External System Built............................................................................46

4.3.1 Results...............................................................................................46

4.2.2 Calculation of thermal efficiency for the External System Built..........49

4.2.3: Conclusion for the External System Built..........................................52

Chapter 5: Conclusion.......................................................................................52

5.1 Key findings:...............................................Error! Bookmark not defined.5.2 Conclusion..............................................Error! Bookmark not defined.5.3 Future recommendations.........................................................................54

Chapter 6: Bibliography.....................................................................................55

Bibliography.......................................................................................................55

4.3: Experimental results for the old system (Test 2) Error! Bookmark not defined.

4.3.1 Calculation of efficiency for the second experiment (test 2)........Error! Bookmark not defined.4.3.2 Conclusion for the second experiment (Test 2). Error! Bookmark not defined.

Table of figures

Figure 1 Household Electricity Price (Sustainable Energy Authority of Ireland , 2013).................................................................................................................... iFigure 2 This is the total Primary Energy Requirement Ireland (Sustainable Energy Authority of Ireland , 2013)......................................................................1Figure 3: Map of Ireland showing by the sunlight distribution of the sun during the summer (Walsh S, 2012)...............................................................................6Figure 4: Map of Ireland showing the sunlight distribution of the sun during winter (Walsh S, 2012) .......................................................................................6Figure 5: Map of Ireland showing the sunlight distribution of the sun during in spring (Walsh S, 2012) .......................................................................................7Figure 6: Map of Ireland showing the sunlight distribution of the sun during autumn (Walsh S, 2012) .....................................................................................7Figure 7: Graph showing the overall sunshine hours in Ireland along the year (Weather and Climate, 2013) .............................................................................7Figure 8: Flat-Plate Collector (The Worlds of David Darling, 2009)...................11

iv


Figure 9: selective coatings applied to transparent covers on flat plate collectors (Vettrivel H.V, Dr. Mathiaragan, 2013) ............................................................13Figure 10: Schematic for Evacuated-Tube Collector (The Worlds of David Darling, 2009)....................................................................................................14Figure 11: Schematic showing thermocouple calibration (Facstaff, 2014)........18Figure 12: Tolerance classes for k type thermocouples (Omega, 2014)...........19Figure 13: Tolerance classes for k type thermocouple (Uteco, 2014)...............19Figure 14: The above is thermocouple calibration (Marineinsight, 2014)..........19Figure 15: Thermo well diagram (blogspot, 2014).............................................20Figure 16: Picture showing the acrylic flow meter (Inds, 2014).........................21Figure 17: the volumetric calibration method for variable area flow meter (ISA, 1961).................................................................................................................22Figure 18: the gravimetric calibration method (ISA, 1961)................................23Figure 19: the comparison calibration method (ISA, 1961)...............................23Figure 20: pressure calibration pump (Magnumpropumps, 2014).....................24Figure 21 Pump Wilo-Star-RS 25/4 (Valgroup, 2014).......................................24Figure 22: Pump Wilo-Star-RS 25/4 impulse and power absorbed (Valgroup, 2014).................................................................................................................26Figure 23: Original system to evaluate the efficiency of the solar thermal panel..........................................................................................................................27Figure 24: New system to evaluate the efficiency of the solar thermal panel....28Figure 25: Circulating Pump..............................................................................29Figure 26: Thermocouple..................................................................................30Figure 27: Copper cylinder used in the external circuit.....................................31Figure 28: Flow meter used in the external circuit.............................................32Figure 29: Copper and plastic pipes..................................................................32Figure 30: Valve on the hot return in the primary circuit....................................33Figure 31: Pressure valves on the copper cylinder...........................................33Figure 32: Insulation..........................................................................................34Figure 33: the expansion tank vessel................................................................35Figure 34: the high intensity lamps used during the experiments......................36Figure 35: Radiometer.......................................................................................36Figure 36: Return reverse header design in evacuated tube panel...................38Figure 37: steady state diagram........................................................................38Figure 38: Variation of temperature along time in the Original System.............43Figure 39 System efficiency over the temperature difference in the Original System..............................................................................................................46Figure 40: Temperatures measured at different parts of the circuit...................49Figure 41: System efficiency over the temperature difference in the External System Built......................................................................................................52Figure 42: Second experiment graph result (old system)....................................2Figure 43: Temperatures measured at the closed circuit along the time with 10 litres of water inside the tank and no flow rate in the second circuit....................4

v


Figure 44: Temperatures measured at the closed circuit along the time with no water inside the tank and no flow rate in the second circuit................................5

Table of tables

Table 1: Safe temperature ranges for solar thermal panels (Kalogirou, Soteris A., 2004)............................................................................................................11Table 2: Usefull pump information (Valgroup, 2014).........................................25Table 3: Radiation along the surface measured twice in the solar flat panel during the experiments......................................................................................40Table 4: Average irradiance at each part of the solar flat panel........................41Table 5: Temperatures measured in the original system the first 10 minutes.. .42Table 6: Temperatures measured in the original system between first 10 and 20 minutes..............................................................................................................42Table 7: Temperatures measured in the original system between first 20 and 30 minutes..............................................................................................................42Table 8: Useful data for the original system......................................................43Table 9: experimental data................................................................................44Table 10: experimental data..............................................................................44Table 11: Temperatures measured in the first experiment along the first 90 min...........................................................................................................................47Table 12: Temperatures measured in the first experiment between min 100 and 180....................................................................................................................48Table 13: Temperatures measured in the first experiment between min 190 and 280....................................................................................................................48Table 14: Temperatures measured in the first experiment between min 290 and 340s...................................................................................................................49Table 15: Useful data for the External System Built..........................................49Table 16: Useful data for the External System Built..........................................50Table 17: Useful data for the External System Built..........................................50Table 18: Experimental data results (test 2)........................................................2Table 19 Temperatures measured in the second experiment along the first hour.............................................................................................................................3Table 20 Temperatures measured in the second experiment along the second hour.....................................................................................................................3Table 21: Temperatures measured in the second experiment from the second hour till the stabilization of T2..............................................................................3Table 22: Temperatures measured in the third experiment along the first hour. .4Table 23: Temperatures measured in the third experiment from the first hour till the stabilization of T2..........................................................................................5

Table of equations

vi


Equation 1 Triple E eligibility criterion................................................................12Equation 2: The equation used for liquid calibration volumetric method (ISA, 1961).................................................................................................................21Equation 3: The equation used for liquid calibration gravimetric method (ISA, 1961).................................................................................................................22Equation 4: Solar Thermal Effciency.................................................................44Equation 5: quantity of heat absorbed by the water..........................................44Equation 6: Incident light radiation....................................................................45Equation 7: Pump power...................................................................................45Equation 8: quantity of heat output out of the system due to the water flow.....45Equation 9 Solar Thermal Effciency final calculation.........................................45Equation 10: Mass flow rate..............................................................................47Equation 11: Solar Thermal Effciency...............................................................50Equation 12: quantity of heat absorbed by the water in the tank.......................50Equation 13: Incident light radiation..................................................................51Equation 14: Pump power.................................................................................51Equation 15: quantity of heat output out of the system due to the water flow. . .51Equation 16: Solar Thermal Efficiency final calculation.....................................51

NomenclatureASHRAE American Society of

Heating Refrigerating and Air Conditioning

-

EU European Union -

ESTIF European Solar Thermal Industry

Federation

-

FPC Flat Plate Collector -

Sec Collection time in seconds

[s]

SWG Standard Wire Gauge -

SPRT Standard Platinum Resistance

-

vii


Thermometer

TC Thermocouple -

A Collector area corresponding to the

performance parameters

[m2]

CP Specific heat capacity of water

[J . kg−1 .K−1]

T Time [s]

T Temperature [℃]

V c Volume of calibrating liquid collected in units

consistent with Qm

ρ f Density of liquid to be metering float in

grams/cc

[g /cc ]

ρm Density of liquid to be metered in grams/cc

[g /cc ]

ρc Density of calibrating liquid in grams/cc

[g /cc ]

Q Heat [W ]

˙QRadlightIncident radiation from

lamps[W ]

Qwater Energy transferred to the water

[W ]

viii


Qloss Losses in the system -

Qm Volumetric flow rate of liquid to be metered in

units per minute

-

Wm Mass flow rate of fluid to be metered in

pounds per minute

-

W c Weight of calibrating fluid collected in

pounds

-

ρ f Density of metering float

[g /cc ]

ρm Density of liquid to be metered

[g /cc ]

ρc Density of calibrating liquid

[g /cc ]

q Power output ¿]

G Solar irradiance on collector plane

[w /m2¿

a1 1st order heat loss coefficient (heat loss coefficient at collector

fluid temperature equal to the ambient temperature)

[W /K ]

a2 2nd order heat loss coefficient(temperature dependant term of heat

loss coefficient)

[W /K2]

dT Temperature difference between the collector

mean fluid temperature and ambient air

temperature

[K ]

n0 Optical efficiency (combined efficiency of the transparent cover

and the absorber

-

η Thermal efficiency of a [% ¿

ix


solar collector

x


Chapter 1: IntroductionThere is a global need for efficient use of fossil fuels for the provision of energy and also the use of renewable energy sources to reduce the dependence of the country’s energy supply to reduce energy bills, reduce greenhouse gas emissions, increase the number of jobs in the renewable energy industry, and reduce the price of fossils fuel.

Figure 2 This is the total Primary Energy Requirement Ireland (Sustainable Energy Authority of Ireland , 2013).

In developed countries most of the fuel consumption is used for heating, cooling, ventilation and sanitary hot water. The potential of solar water heaters is huge because all homes, commercial buildings and industrial facilities require hot water. This type of technology is feasible and an economic attraction compared with other kinds of solar energy utilization.

The Solar panels transform the solar radiation into hot water. It is stored in a hot water cylinder during the day and it can be used when the heat is needed. They are generally located on a south-facing roof. When the demand for hot water rises it will be more beneficial to install a solar thermal collector since the payback period will be short.

Almost all solar water heating systems used in temperate climates use flat plate or evacuated tube collectors, which absorb both diffuse and direct solar radiation and function even under clouded sky. In Northern Europe, solar domestic water heating systems can meet up to 60-70% of the water heating

Group Platinum 1 28/04/2014


needs of a typical house and in southern Europe up to 90% so the evaluation of solar thermal systems is very important (Elementary Energy Ireland, 2009).

1.1: European Solar Thermal SectorThe effects of the financial crisis in 2008-2009 are still being felt and it is blocking the solar thermal sector from taking full advantage of the European trend.

The promotion of the use of energy from Renewable Energy Sources was adopted by the European Parliament and Council in 2009. Their treaty incorporated an act which encouraged that all the state members incorporate a share of renewable in their total energy mix and the EU is aiming for a 20% cut in Europe's annual primary energy consumption by 2020. The Commission has proposed several measures to increase efficiency at all stages of the energy chain: generation, transformation, distribution and final consumption (EuropeanSolar Thermal Industry Federation, 2012 ) .

Despite that, the National Renewable Energy Plan shows that there are a lot of countries where the solar thermal market is very low or they do not have markets like Estonia or Romania. The major markets would be Italy, Germany, France, Spain and Poland.

1.2: Irish Solar Thermal Sector:To develop the Irish market for solar thermal heating, it will be important for an EU wide implementation of standards and a general promotion of this type of technology.

The Irish Government has promised to guarantee a sustainable development. They have also agreed to increase the contribution to the renewable energy market and deliver a sustainable energy future central policy in Ireland. With other EU Member States, Ireland has agreed a legally binding objective for 20% of our total energy (heat, transport and electricity) to come from renewable sources by 2020 (European Comission, 2009) .

The Government has set an objective for 12% of heat to come from renewable sources by 2020. Moreover, the Government has made solar thermal more attractive providing incentives which continue to increase the market (SEAI,2014) .

The Solar thermal sector in Ireland is relatively undeveloped compared to other European countries. The total number of installed solar thermal collectors in 2003 is around to 5000 [m2¿ producing more or less 2500 [MW /h¿ of heat, and



saving more than 700 tons of [CO2¿ per year. The majority of the installations are air-collectors followed by flat plate and evacuated collectors (EuropeanSolar Thermal Industry Federation, 2012 ).

As it is not possible to depend on solar energy at all time in Ireland, a solar water heater or a solar combo-system needs the support of a heating system such as a boiler, a heat pump or an electric heater.

1.3: Project AimsThe aim of this project is the construction of one external circuit simulating one real installation of a solar thermal panel and to evaluate the efficiency of the flat-plate collector under laboratory conditions. Another important outcome is to find out which type of solar collector is the best to install in Ireland. The last outcome is to improve the group’s knowledge of the renewable energy sector in Ireland and in Europe.

1.4: Project Objectives Perform a Literature review about the Renewable and sustainable forms of

energy production, especially into solar energy (the solar thermal panels). Evaluated the differences between evacuated tube collector and flat-plate

collector. Design and build one external circuit simulating a real system in a house to

obtain hot water with a solar thermal panel. Determine the efficiency under laboratory conditions of the flat-plate

collector and understand the relevant mathematics associated with it. Identify which collector will work better in Ireland´s climate. Work as a team during all the process.

1.5: Project scopeThe project scope was to improve the system and to test the efficiency of solar thermal panels. Time was a major constraint for this project since the external circuit took longer than predicted to make. If there was more time more experimental elements of the project could have been done like the comparison between evacuated tube collector and flat-plate collector. Another such element was to test the effect wind has on solar thermal collectors. All the laboratory experiments were carried out inside the solar lab but a fan could have been used to simulate wind just as the high intensity lamps were used to simulate the sun.

The collector was not tested outside because of unstable conditions. The ambient air temperature is one of the key factors in solar thermal collector efficiency as was discussed in the literature review. The ambient air



temperature is one of three factors that govern the efficiency of the solar thermal collector.

At the beginning of the project a risk assessment was done. This looked at any possible risks that could occur during the course of the experiments. When the project was being built all the work was carried out in workshop where again there was a safety element involved. Within the circuit there was safety features attached such as an expansion vessel for the primary circuit which was heated by the solar thermal collector. There was also a safety valve put on that same primary circuit which was a three bar expansion valve. The secondary circuit was left open to the atmosphere so that a pressure would not build up in the copper cylinder. The copper cylinder that was used was bigger than the one originally planned but this meant that the water inside would take longer to heat and thus the experiment would be finished as the max temperature of the panel would be obtained before the tank would heat fully.

The safe operating temperature for the collector was researched as part of the literature review. For the flat plate collector the maximum operating temperature is 80 degrees Celsius. Once the operating temperature is reached the experiments are were stopped for safety reasons.

1.6: Project budgetFor each group doing the final year project there is a fund of €300 allocated to each group. For the project there were a number of items purchased. The first item was to buy a copper cylinder that cost €150. The next items that were purchased were connections for the secondary circuit for the copper cylinder. They cost €20. The last item that was bought was a lagging jacket for the expansion cylinder and the pump. This was purchased and was used to insulate the expansion cylinder and the pump. This small lagging jacket cost €9.99. After all the items were bought there was €119 left from the budget.

1.7: Project methodologyThe external circuit that was built for the project was built for a number of reasons. The first reason was to improve the efficiency of the system that is used to test the solar thermal collector because the original circuit that was installed was inefficient.

On the original circuit, the pump was installed at the bottom of the collector. This caused inefficiency within the system because it was adding heat while it was running. Also, the bottom rows of the high intensity lights caused the components to heat up.



As mentioned in the literature review, the incident radiation is one of three key factors that govern solar thermal collector efficiency. Since only half of the panel was used, the efficiency of the system was hampered.

To solve these problems the external circuit was built. The external circuit consists of a pump, flow meter, expansion cylinder and the copper tank. This was all connected using 22¿] copper pipe and 13[mm] copper pipe. There were also a number of valves that were attached at various different points to control and regulate the flow of water.

The experimental procedures were to the standard that was mentioned in the literature review. In the literature review previous solar thermal experiments were looked at. The laboratory experiments that were researched included the flat-plate and evacuated tube collectors in a controlled laboratory experiment as well as in outside conditions.

The experiments in the laboratory were carried out exactly as the one that was done in semester one for the module Solar Energy. In that class the group learned how to run the solar collector experiment. There was slight variation in the tests that included the external circuit, as the external circuit contained a slightly different set up than that which was found in the original circuit.

During the building of the external circuit a number of plumbers were consulted. They informed us on all the safety aspects of such as the expansion vessel and the expansion valve and their suitable location.

Chapter 2: Literature ReviewThe literature review is a collection of research and findings that were found from internet sources and books related to the solar thermal sector. Through this section we will look at at solar sources and their data, the history of solar technology and the various options on the market and their components that make the system work.

2.1: Weather in IrelandIreland usually gets between 1100 and 1600 hours of sunshine per year, provided by both types of sunlight: direct sunlight (40%) and indirect sunlight (60%).

According to the geographical area the average hours of sunshine varies slightly. For instance, on the south of the country, at Roche’s Point’s Weather Station, an average of 3.9 hours of sunlight per day during the course of the



year (Met Eireann , 2014) while the north of the country at Belmullet Weather Station receives an average of 3.5 hours of sunlight per day during the course of the year (Walsh S, 2012).

Regarding the majority of areas in the country, they get an average of between 3.25 hours and 3.75 hours of sunshine per day. (Walsh S, 2012).

The sunniest part is the south-east coast, where Rosslare, County Wexford is the sunniest area, receiving on average 4.38 hours of sunshine per day. On the contrary, the dullest town is Birr, County Offaly, receiving an average 3.2 hours of sunshine per day.

Logically, hours of sun varies depending on the season. In summer months, May and June are the sunniest months receiving between 5 and 6.5 hours of sun each day over most of Ireland.

On the contrary December is the worst month, with an average daily sunshine of about 1 hour in the north and almost 2 hours in the south-east

In terms of sunshine hours during spring and Autumn periods, in spring the country receives an average of 4.5 hours while in autumn the average of sunshine hours is just around 3 hours.


Figure 3: Map of Ireland showing by the sunlight distribution of the sun during the summer (Walsh S, 2012)

Figure 4: Map of Ireland showing the sunlight distribution of the sun during winter (Walsh S, 2012) .

http://en.wikipedia.org/wiki/County_Offaly

http://en.wikipedia.org/wiki/Birr

http://en.wikipedia.org/wiki/County_Wexford

http://en.wikipedia.org/wiki/Rosslare_Strand


Figure 7: Graph showing the overall sunshine hours in Ireland along the year (Weather and Climate, 2013) .

We can now conclude that the solar climate of Ireland varies greatly throughout the year which makes us question the use of solar thermal panels in countries such as our own. However, it can be seen in the next section that all is not lost when analyzing the strengths and weaknesses involved.

2.2: Strengths and weaknesses of solar systems

2.2.1: Strengths

Renewable energy solar energy is clean, inexhaustible and environmentally friendly.


Figure 5: Map of Ireland showing the sunlight distribution of the sun during in spring (Walsh S, 2012) .

Figure 6: Map of Ireland showing the sunlight distribution of the sun during autumn (Walsh S, 2012) .


Clean energy production this reduces the home´s carbon footprint because It is carbon-free. However, there are some emissions associated with the manufacturing, transport and installation of solar power systems.

Installation initiatives the government offer grants or discount for the installation of renewable energy products. This means that the real cost of solar panels is less than what they used to be.

Abundant The surface of the earth receives 20,000 times more solar power than what the entire world need.

Operating costs are low Solar energy is free and the solar water heaters require little maintenance. Therefore the operating costs are lower compared to those of fossil fuels.

Good availability solar energy is available all over the world. Reduced dependency you can generate your own heat and use

it when you need. High efficiency the technology in the solar power industry is

constantly improving. Silent There are not moving parts involved, so there is no

noise associated.

2.2.2: Weaknesses

Intermittent Solar energy is an intermittent energy source because the sun does not shine brightly 24 hours a day.

Low energy density the mean of power density for solar radiation is 170 W/m². This is a good value if we compare with other renewable energy source, but not if we compare to oil, gas and nuclear power.

Expensive Construction and installation costs can be relatively high. Even with the installation initiatives, a solar system has a high initial cost. Therefore, it is hard to compete against very cheap natural gas.

Relatively new technology involvedsometimes it requires materials that are expensive and rare in nature.

Site preparation they require a considerable amount of space and to alter some of the home´s infrastructure systems.

Some people find them unattractivethe solar panels are placed on the roof of the property.

Pollution Some manufacturing processes often are associated with greenhouse gas emissions.



Efficiency is dependent on sunlight resourcesin cold climates the efficiency is smaller and it cannot work if they are covered by snow.

2.4: Feasibility of installing solar thermal panels in Ireland. The feasibility of installing solar thermal panels is determined by the radiation level that would be achieved.

The sun's radiation levels of Ireland would be able to heat as much hot water in one year using only about 450 units of electricity. Even on cloudy days in winter and summer the sun´s heat can still supply hot water providing on average up to 70% of the annual hot water demand (Elementary Energy Ireland, 2009) .

Solar evacuated tubes have benefits over solar flat plates in Ireland, due to the fact that they don’t have heat losses because they are vacuum insulated and on an average day, the air temperature might be 10 º C so the panel at 70 ºC will lose lots of heat to the outside air. (Elementary Energy Ireland, 2009)

In addition, solar flat plate collectors work properly when the sun is overhead but they cannot take advantage of the energy at 4 p.m. in the afternoon when the sun is facing the side of the flat surface, thus solar evacuated tubes work better in Ireland conditions.

The cost of installation and supply of an entire solar water heating system in a dwelling with a 3 m² solar collector tubes in Ireland start from 3900 € and there is a SEAI grant of up 800€ (SEAI, 2014) .

Grants are available from the SEAI for some renewable energy projects which will help decrease the capital cost involved.

Approximately it can be expected that the electricity usage for hot water will be decreased by between 1200 and 1500 kWh per year with a 3 m² solar collector tube installed. This is equivalent to between €192 and €240 every year according to the Standard Tariff rate (Alternative energy ireland, 2014)

2.5: Natural circulation and forced circulationThere are two choices for circulation; natural circulation and forced circulation. Natural circulation is called thermo siphon. This type of circulation uses the thermodynamic properties and gravity to move the fluid in the solar panel. Water rises when heated hence the name thermo siphon circulation. The water rises, circulates and comes back down and the cycle begins again. These systems are sometimes used on houses where the thermo siphon tank is mounted above the solar collector.

At the start of the project this type of circulation was considered but after doing the calculations it was found that there would not be enough gravity to push the



water up the proposed height difference. There was also a safety element within this circulation, as the tank height was proposed to be over 2 meters tall and the tank had the capacity of 18 litres. This was a hazard, especially since the tank would collect the hot water from the solar thermal panel.

The other type of circulation is the forced circulation. This is where the pump is used to circulate the water around the entire circuit. This method was used in the project to run the solar collector.

The equation to determine solar collector efficiency takes into account the electrical power supplied by the pump.

2.5: Selection of the Solar Collector TypeEach type of collector has its advantages and disadvantages, and in many cases both can work for the same application and situation. It is very important that your selection is the proper design, sizing, components and installation otherwise the collector will not obtain the efficiency required.

In the market, there different types of solar thermal collectors but this report has been focused on Flat-plate collectors.

2.5.1: Flat plate solar collectors

The main components of a flat-plate collector are: an insulated metal box with a glass or plastic cover and a dark-colored absorber plate. Solar radiation is absorbed by the absorber plate and transferred to a fluid that circulates through the collector and into the copper pipes. The heat transfer fluid is pumped from the hot water storage tank. If it is a direct system a heat exchanger is used. If it is an indirect system, a copper storage vessel is used. (The Worlds of DavidDarling, 2009) .



Figure 8: Flat-Plate Collector (The Worlds of David Darling, 2009).

2.5.2: Flat-plate collectors under laboratory conditions and solar collector standards.

The picture below is from a report that was published by mechanical engineers in Cyprus. In that report they mention the maximum temperature that FPC should go to. This guideline was followed during the experiments that were done for the project.

Solar energy collectorsMotion Collector type Absorber type Concentration ratio Indicative

temperature range [ºC]

Stationary Flat plate collector (FPC)

Flat 1 30-80

Evacuated tube collector (ETC)

Flat 1 50-200

Table 1: Safe temperature ranges for solar thermal panels (Kalogirou, Soteris A., 2004).

The picture includes the temperature range for evacuated tubes but they were not part of the experiments as only the flat-plate collector was used during the experiments.There are also standards that are used when caring out laboratory experiments involving solar thermal collectors. The standard that is used more often is the ASHRAE standard 93: 1986 (ASHRAE, 2003). In this standard there is three elements that are analyzed. They are incident radiation, ambient temperature



and inlet fluid temperature. There is an also triple E eligibility criterion that is used in Europe. For the solar collectors there are two standards the EN12975-1 (Part 1 General Requirements) and EN12975-2 (Part 2 Test Methods). The other standard is for factory made systems and they are EN12976-1 (Part 1 General Requirements) and EN12975-2 (Part 2 Test Methods). They also mention that the following standards should be used when comparing to other products. G: 900 W/m2,dT 50K and A: 1m2 CITATION Cha03 \l 6153 (ASHRAE, 2003).

Equation 1 Triple E eligibility criterion

q=A(n0G−a2dT−a2dT2)[W ] CITATION SEA \l 6153 (SEAI, 2012)

The experiment that was carried out for the project was run to this standard. The standard has the following criteria; rate of incident radiation falling on the solar thermal collector was measured as well as the rate of heat transfer to the fluid that is used during the experiment all of these were analyzed under steady state or quasi-equilibrium conditions. Quasi-equilibrium can be defined as” A quasi-equilibrium process can be viewed as a sufficiently slow process that allows the system to adjust itself internally so that properties in one part of the system do not change any faster than those at other parts” (Yunus A.C, JohnM.C, Robert H.T , 2012).

In some of the laboratory reports that were published on this topic they look at different types of absorber used when making flat plate solar thermal panels and also look at the materials that the transparent cover is made of. There is a number of absorber materials that where looked at as part of that report. That report was written by mechanical engineers in India. They found that the efficiency of the flat plate collector is increased with ambient temperature as the heat loss was reduced (Vettrivel H.V, Dr. Mathiaragan, 2013) .

The other element of the experiment that was found was that the emissivity of the plate had significant impacts on the system efficiency. The element that was found during that particular experiment was that “It can be observed increase in pε is to dissipate more heat to atmosphere and consequent reduction in efficiency of the system”. So the transparent cover that the flat plate collector is made of is a very important factor when determining efficiency of the system. In a different report that was written by mechanical engineers in India from a different technical institute they conducted their research into the different coatings that are applied onto the transparent cover. The picture below shows all the coatings that are applied on flat plate collector panels at present (Sunil.K.Amrutkar, Satyshree Gholdke,Dr.K.N.Patil, 2012) .



Figure 9: selective coatings applied to transparent covers on flat plate collectors (Vettrivel H.V, Dr.Mathiaragan, 2013) .

In this report there were a number of findings. These standards were the ones used for solar thermal collectors when running experiments on them. Also, how the emissivity of the coating applied to the transparent cover can affect the efficiency of the solar collector.

2.5.2: Evacuated tube solar collectors:

Evacuated tubes consist into two concentric glass tubes fused together; the inner absorbs the radiation while the outer is transparent and create the vacuum between them. In this way it is possible to isolate the hot water from the outer reducing heat dispersion outwards and therefore gets a much higher efficiency than the solar flat panels. The copper pipe located in the center of the tube connects with the collector and with the pump that circulates the water into the storage tank (University of Strathclyde Glasgow, 2005).



Figure 10: Schematic for Evacuated-Tube Collector (The Worlds of David Darling, 2009).

2.5.3: Cost:One of the primary considerations for the selection of the collector type is the cost. Usually, evacuated tubes collectors may cost between 1.2 and 2 times more but this can be interoperated in the different ways. However, in cold climates the additional cost is easily recouped by increased performance.

For example, in the case of Dublin Institute of Technology to run an experiment to compare the Flat Plate and Heat Pipe Evacuated Tube Collectors for Domestic Water Heating Systems in a Temperate Climate and using one evacuated tube collector of 3 m2 and one flat plate collector of 4m2 the price of the first one was the double of the second one (L.M. Ayompe, A. Duffy, S.J.McCormack, M. Conlon, M.Mc Keever, 2011) .

2.5.4: Size:The typical domestic installations for families of 4-6 persons in temperate climates consist of 4-6 m2 flat plate solar collectors or 3-4 m2 evacuated tubes collectors connected to a 200-300 liters hot water tank (L.M. Ayompe, A. Duffy,S.J. McCormack, M. Conlon, M.Mc Keever, 2011) .

2.5.5: Life Spam:Generally both types of collectors are designed to last 20 years or more and they are sold with 10 years limited warranty.

However, evacuated tubes need more maintenance and repair because:

Flat plate collectors will use thick (usually 4 millimeters), the tempered glass can support without breaking under harsh weather conditions such as hail storms. On the other hand, evacuated tubes use thinner glass (usually 1.6



millimeters) which is more susceptible to breaking and needing to be replaced. This is one of the reasons that flat-plate collectors are considered the most durable collector type.

Evacuated tubes rely on a vacuum seal to prevent heat loss. Over time this seal can be lost and the tube will required to be replaced.

The main problem of flat plate is that if something does break (such as the glass), the installer will usually need to replace the entire collector. Though evacuated tube collectors, due to the modular design, if an individual tube is damaged no fluid enters the tube anyway so the system does not need to be drained and it can be easily replaced (Heliodyne, 2010) .

2.5.6: Payback Periods:Payback periods vary, depending on a number of factors: the cost of the fuel displaced the amount of hot water used and the initial cost of the solar thermal system.

A typical payback time for a household of 5 people who normally use oil or gas to heat their hot water would be about 6 to 8 years or 4 to 5 years if they use electricity.

2.5.7: Installation:Both collectors have their advantages and drawbacks in terms of installation.

Supporters of evacuated tube said that because they come unassembled, is easy to easily carry the evacuated tube components onto the roof without needing any special equipment.

Proponents of flat plate argue that because they are fully assembled, once hoisted onto the roof, no assembly is required so the installation time is reduced (Heliodyne, 2010) .

2.5.8: Useful ClimatesEvacuated tubes collector, can be used in any climate, from extremely hot to extremely cold.

Flat Plate collector, should only be used in warm climates where freezing temperatures rarely occur (T. Christoph, W. Zörner, C. Alt, C. Stadler,, 2005) .

2.5.9: OrientationThrough their circular design evacuated tubes are less sensitive to sun angle and orientation than flat-plate collectors. The total efficiency in all areas is higher and there's better performance when the sun is not at an optimum angle (when it’s early in the morning or in the late afternoon).



2.5.10: Efficiency:Flat plate collectors aren’t as efficient as the evacuated tubes but as technology is rapidly improving certain flat plate solar collectors have become just as efficient as evacuated tubes.

The efficiencies of flat plate collectors make them very suitable for domestic installations or for installations that don’t require very high temperatures.

Evacuated tubes collectors are generally less efficient than flat-plate collectors in full sunshine conditions. However evacuated tubes collectors perform better under cloudy windy conditions or extremely cold conditions. Due to the fact that the heat loss to the environment has been reducing because the heat loss due to convection cannot cross a vacuum of the evacuated tube collector but sealing and maintaining a vacuum is difficult and an evacuated tube without a vacuum performs very poorly (Kingspan Renewables Ltd, 2011) .

2.5.11: Conclusion:Summarizing, after study all the information founded we can conclude that:

On one hand, evacuated tube collectors based systems, capture sunlight better as they have a greater surface area exposed to the sun at any time so they have a higher solar yield than flat plate with the same absorber area, are more efficient in transferring heat (30%more) because they have a little thermal loss, work in cold, windy and humid conditions , are durable and if a tube should be broken, it can be easily and cheaply replaced, provide excellent performance in overcast conditions, require a smaller roof area than comparable flat plate collectors, do not have the same level of corrosion problems as flat plate.

On the other hand, flat plate collectors are cheaper, can be easy integrate into the roof of the building but they need higher wind load.

2.6: Calibration for the projectIn the project there are a lot of elements that require calibration. The various measuring elements are the thermocouples, the flow meter, radiometer and the pump is calibrated also. All these measuring instruments are calibrated in different ways.

2.6.1: ThermocoupleCalibration insures that the measurements are in good working order and that the result obtained using these instruments are very accurate. For thermocouples there are a lot of methods for calibration. In a laboratory report written by G.W Burns and M.G Scroger who work in the National Institute of



Standards and Technology that is part of U.S Department of Commerce, they mention that during calibration thermocouples where put into ice baths as reference points. The report also mentions that thermocouple must be calibrated but how depends on the application the results of calibration should be compared to other published figured that can be got from platinum resistance thermometers (G.W Burns and M.G Scroger, 1989).

In the document for calibration they mention three methods for calibration of one of which I mentioned up above. The first method is to compare the result to the “calibrated reference thermocouple in an electric tube-type furnace”. The second method is where a platinum resistance thermometer is put into cryostat (which is a device that is used to keep low cryogenic temperatures of samples or devices mounted within the cryostat itself) or into stirred liquid water and the third method is “at certain thermometric fixed points of the IPTS-68 as realized in metal freezing cells” (G.W Burns and M.G Scroger, 1989) .

In that document the calibration procedure is explained in detail, the SPRT (Standard Platinum Resistance Thermometer) must be connected to a Rubicon six dial potentiometer. The potentiometer is used to measure the emf produced by thermocouple during calibration. Before the calibration the thermocouple must be examined if the measuring junction is not made the must be silver soldered together. If the thermocouple is bare wire and is not insulated then a fiberglass sleeving can be used to insulate it. The test thermocouple is then placed into a glass tube before being placed into the stirred liquid bath (G.WBurns and M.G Scroger, 1989) .

The report suggests that the thermocouples depth of immersion should be 12 inches or 30.48cm in the bath that contains the stirred liquid. The 12 inches or 30.48cm should be below the surface of the stirred liquid. The actual thermocouple is put into the sample that it’s measuring and a copper extension wire is connected to the thermocouple and this copper extension wire connection will go to the stirred liquid bath. The reason this is done is so when the results of the calibration are done the thermocouple will have a reference junction to compare against (G.W Burns and M.G Scroger, 1989) .

The results are recorded by the Rubicon six-dial potentiometer and an automatic bridge. There is a sequence that the potentiometer follows is this SPRT, TC, SPRT, TC and SPRT. The reason the SPRT reading is done three times is that is the bath temperature can be determined from these results. The thermocouple measurement is averaged between the two results. The potentiometer applies correction and the data is normalized to desired temperature. The bath temperature should be carefully monitored if it changes by more than 0.05° C during the three readings then measurement at this temperature is repeated (G.W Burns and M.G Scroger, 1989) .



The stirred liquid bath or calibration bath is a cell that contains the thermocouple. The cell can be inserted into a Dewar flask that is full of liquid. The actual liquid depends on the application itself. The cells are made of highest purity material available and are insulated to minimize the result derivation. The Dewar flask is used to maintain a temperature required for the test. The liquid in the Dewar flask is usually 100 litres liquid nitrogen (LN2). But for tests that require the temperature to remain constant for very long periods of time 40 litres of ethanol is used. The system uses two-stage compression system and temperatures up to -80 can be maintained (G.W Burns and M.GScroger, 1989) .

The main function of a thermocouple is to measure the temperature difference between two metals to form an EMF. It is a pair of junctions, one at a reference temperature (eg 00C) and the other junction at an unknown temperature. The temperature difference will cause a voltage commonly known as the Seed beck effect.

Figure 11: Schematic showing thermocouple calibration (Facstaff, 2014)

The thermocouples that are used in the project were k type thermocouples. The accuracy of thermocouples is determined by the temperature that will operate in. There are two tolerance classes for the k type thermocouple they are shown on the table below. This class different to the other classes but operates on the same principle as the other tolerance classes. The two classes are called Standard Limits of Error and Special Limits of error.



Figure 12: Tolerance classes for k type thermocouples (Omega, 2014)

There is another chart that shows all the tolerance classes for the k type thermocouple and is shown below. These classes are similar to the Standard Limits of Error and Special Limits of error.

Figure 13: Tolerance classes for k type thermocouple (Uteco, 2014)

All the classes made choosing an accuracy tolerance very difficult so a way around that was to find out if the thermocouple operated within the Standard Limits of Error or within Special Limits of error. The thermocouple that was used in the project was a nickel-chromium/nickel-aluminum. The tolerance class for this particular thermocouple is class 2 or using the other tolerance classification it’s Standard Limits of Error which is +/-2.5% or 0.0075×T. The first chart mentioned Standard Limits of Error for k type thermocouples as +/-2.2% or 0.0075% but is dependent on the material composition of the wire so the figure varies slightly. The thermocouples used in the project where calibrated as mentioned in the report. The way the thermocouples were calibrated is shown below in the illustration.

Figure 14: The above is thermocouple calibration (Marineinsight, 2014)



The thermocouple wires used had the two wires for plus and minus and an additional wire for to create a reference junction in the report it was mentioned that a copper wire was used for this extension into the ice bath. This calibration was mentioned in the report. Another way to improve the thermocouple reading is to place the thermocouple wire directly into the water flow. This can be done two ways one is a thermo well or a binder point. Here is a simple diagram below showing a thermo well.

Figure 15: Thermo well diagram (blogspot, 2014)

The problem with the thermo well is that the response time is very long as the heat must travel through the thermo well wall in order to reach the thermocouple inside. This can be prevented by reducing the amount space that the heat has to travel to the thermocouple inside.

Binder points are similar to thermo wells but they have a smaller area for the heat to travel. Here is a picture of the binder point below.

2.7.4: Flow meterA flow meter is a device used for measuring the flow rate of a liquid in a pipe. Using a flow meter allows for optimal balance across the system, ensuring peak energy distribution which gives us more efficient operation as well as greater performance.

An acrylic flow meter is sufficient for most solar thermal arrays, capable of operating under temperatures of up to 650 C and maximum pressure of 6.9 bar pressure.



Figure 16: Picture showing the acrylic flow meter (Inds, 2014)

The flow meter also requires calibration this can be done by the company that manufactures the flow meter. When a variable area flow meter is calibrated there is different number of ways it can be done. It also depends what type of fluid is used during the calibration as results can vary. The ISA has recommended practice when it comes to the calibration of variable area flow meter both for gas and fluid. Also there are three basic methods when it comes to variable area flow meter calibration, these are volumetric, gravimetric and comparison (ISA 1961). In volumetric method “the volume of fluid flowing is accurately measured and timed as it passes through the Rota meter into the collecting chamber at a controlled rate” (ISA 1961). These are the variable area flow meter used during the project contained water as the fluid. The equation that is used for volumetric liquid calibration is this.

Equation 2: The equation used for liquid calibration volumetric method (ISA, 1961)

Qm=V c

Sec×60×√ (ρf−ρm ) ρo

(ρ f−ρ c) ρm

The gravimetric method involves using a very accurate scale to measure the fluid that passes through the flow meter. The equation that is used in the gravimetric method is this one below.



Equation 3: The equation used for liquid calibration gravimetric method (ISA, 1961)

Wm=W c

Sec×60×√ (ρ f−ρm ) ρm

( ρf−ρc ) ρc

The comparison method involves using another accurately calibrated flow meter to use as a comparison to the one being tested. The accuracy of this method depends on the accuracy of the second flow meter. The next page shows the schematic for all of the methods.

Figure 17: the volumetric calibration method for variable area flow meter (ISA, 1961)



Figure 18: the gravimetric calibration method (ISA, 1961)

Figure 19: the comparison calibration method (ISA, 1961)

2.7.1: Circulating pumpThe nominal flow rate of a small solar heating system is 30 to 50 litres per square metre of collector surface. This circulation pump has to be able to



guarantee this flow rate. Conventional pumps with an electric input between 40W and 80W are sufficient for most solar system arrays.

When a pump is calibrated the water flow is measured against back pressure. This is done using a flow meter. There is also calibration devices that are used one such device is below. This device is used to create a pressure so that it can be measured. Some pumps can be calibrated digitally using various software programs.

Figure 20: pressure calibration pump (Magnumpropumps, 2014)

There is also digital calibrator that can be linked into computers and can analyze the pump and its performance.

.


Figure 21 Pump Wilo-Star-RS 25/4 (Valgroup, 2014)

http://productfinder.wilo.com/repo/media/previews/00504124_0.jpg


Table 2: Usefull pump information (Valgroup, 2014)


Material

Pump housing: Grey cast iron (EN-GJL-200)Impeller: Plastic (PP - 40% GF)

Pump shaft: Stainless steel (X40Cr13)Bearing: Carbon, metal impregnated

Approved fluids (other fluids on request) Max. Volume flow: 4 m3/hMax. delivery head: 4 m

Pipe connectionsThreaded pipe union: Rp 1

Overall length: 180 mm

Motor/electronics

Electromagnetic compatibility: EN 61800-3Emitted interference: EN 61000-6-3

Interference resistance: EN 61000-6-2Protection class: IP 44

Insulation class: FMains connection: 1~230 V , 50 Hz

Speed: 2350 / 2630 / 2720 rpmNominal motor power: 15.5 / W9.5 / W5.5 W

Power consumption 1~230 V : 28 / 38 / 48 WCurrent at 1~230V : 0.13 / 0.17 / 0.21 A

Max. Current: 0.21 / 0.17 / 0.13 AMotor protection: Not required (blocking-

current proof)Threaded cable connection: 1x11

Information for order placements

Art no.: 4032954EAN number: 4016322364191

Weight approx.: 2 kgMake: Wilo

Designation: Wilo-Star-RS 25/4


Figure 22: Pump Wilo-Star-RS 25/4 impulse and power absorbed (Valgroup, 2014)

2.7.6: RadiometerThe last element in the project that required calibration was the radiometer. The radiometer that was used during the project was calibrated by a technician when the project was started so it didn’t require calibration. When a radiometer is calibrated the following factors are taken into account.

Direct normal ("beam") solar irradiance (Watts/square meter)

Diffuse horizontal ("sky") solar irradiance (Watts/square meter)

Radiometer body temperature (Degrees Celsius)

Pyrometer dome temperature (Degrees Celsius)

Air temperature near calibration tables (Degrees Celsius)

Relative Humidity near calibration tables (Percent)

The calibration standard for shortwave radiometer is governed by the World Radiometric Reference. All their data is compiled from “seven self-calibrating absolute cavity radiometers”. Every five years reference radiometers around the world are brought to the World Radiation Centre in Switzerland and are compared against the seven self-calibrating absolute cavity radiometers. These



radiometers are used in other laboratories and in industry to set a working standard.

Chapter 3: Materials & Methods:As we have seen, the aim of this project is to evaluate the efficiency of the flat-plate collector under laboratory conditions. To do that, had been decided the construction of one external circuit simulating one real installation for a solar thermal panel because with the actual method there are some problems and it is very far from the real system.

Figure 23: Original system to evaluate the efficiency of the solar thermal panel



Figure 24: New system to evaluate the efficiency of the solar thermal panel

The new system is more similar to the system of a typical house, it will be tested and the results obtained will be commented.

3.1: Materials:

There was a number of Materials that were used during the course of the Project

3.1.2: Circulating pumpA circulating pump works by pumping the liquid in a loop or closed circuit. In a closed loop system, little energy is needed as the liquid travels around the loop and returns to its original position. The pump only needs enough power to counteract the drag or inertia in pipes to propel the water forward efficiently.

An electric motor powers an impeller, which sends the water forward or upward. The motor is sealed in a waterproof casing and is connected to the impeller.

In the case of the Solar Thermal system in question, water is pumped to the solar collector where it will be heated. That water then moves its way to the



water tank, where the heat is dissipated to the water. The pump then sends the cooler water in the tank back to the collector and the process is repeated until all water is heated and set at a cut of point.

Figure 25: Circulating Pump

3.1.3: ThermocoupleThe main function of a thermocouple is to measure the temperature difference.



Figure 26: Thermocouple

3.1.4: Hot water tankThe hot water tank consist is a cylinder that contains a coil. This coil connected to the solar thermal panel “primary circuit” transferred the heat into the water of the tank it does not mix with the stored water in the cylinder. The “secondary” circuit refers to the stored water in the hot water cylinder which is used for domestic use. In the primary circuit the same water continuously circulates.

The characteristics of the tank are:

Height 36¿ = 91.440cm Diameter 15¿ = 38.100cm Capacity 94 liters Date of Manufacture 13/12/13 Type Open Expansion Reservoir Supply Max Static Head 10metres Company LB Cylinders



Figure 27: Copper cylinder used in the external circuit

3.1.5: Flow meterA flow meter is a device used for measuring the flow rate of a liquid in a pipe.

One will be installed into the close circuit and the flow rate of the open circuit will be measured filling one pipette and measuring the time.



Figure 28: Flow meter used in the external circuit

3.1.6: Copper and plastic pipesCopper and plastic pipes are used for supply of hot and cold water systems.

Copper offers a high level of resistance to corrosion and the plastic is a good insulation to avoid the losses of heat and with its flexibility facilitates the connections of the circuit.

Figure 29: Copper and plastic pipes



3.1.7: ValvesValves are used to regulate the flow rate for both circuits and to facilitate the connection and disconnection of the system.

Figure 30: Valve on the hot return in the primary circuit

3.1.8: Pressure ValvesUsing this type of valve, the security of the system is guaranteed because if in some moment the pressure is too high the valves will be open before discharging it.

Figure 31: Pressure valves on the copper cylinder



3.1.9: InsulationThe insulation is used to recoat as many parts of the circuit as is possible to avoid the heat losses.

Figure 32: Insulation

3.1.10: Expansion tank vesselThe expansion tanks ensure that the system pressure does not exceed or drop below the limits obtained in the design of the system. The design of the expansion tank divides the air space inside the tank occupied by the pre-charged gas and the solar liquid. As the liquid expands due to heat, the diaphragm stretches into the gas chamber.

The idea of the expansion tank allows for your solar heating system to operate at optimal pressures without activating the safety relief valve. The size of the tank is chosen depending on the solar loop requirements

The expansion tanks are an essential component in the steam-back solar design, allowing for high pressure performances, resulting in a long lasting and high performing solar thermal system.



Figure 33: the expansion tank vessel

3.1.11: Panel with the lightsAll the light will be turn on to simulate the light intensity of the sun.



Figure 34: the high intensity lamps used during the experiments.

3.1.12: RadiometerThis device was used for measure the incidence light radiation.

Figure 35: Radiometer



3.2: Methods

3.2.1: Procedure: for original system1. Turn on the three rows up of lights (we do not turn on all the lights

because if we will do we would interfere in the measures of the sensors).2. Measure the radiation flux that arrives at the solar thermal panel:3. The solar thermal panel will be divided into two rows and five columns.4. With the lux meter will be measured the W/m-2 that arrives to the panel5. Make the average of the data and use it for make our calculations.6. Obtain the mass flow of water that pass through the solar thermal panel.

To calculate it will be needed some test tube to measure the millilitres per second and will be able to calculate to mass flow that go out from the panel.

7. Collect the data of the temperature sensors (water from the tap (T1), water to panel (T2), water out (T3), ambient air (T4)) approximately every ten minutes to show the progression of the experiment until it arrives to the steady state.

8. Finally, the efficiency of the solar thermal panel will be calculated.

3.2.2: Analysis For the original systemAnalysing the circulation system of the solar vacuum tubes to know its performance characteristics, the path the water takes would be:

The water comes from the tap and enters the circuit. A pump drives water to fill the vacuum tubes. The water passes through the flow meter and you can then measure the

water flow. Vacuum tubes are filled with water and the water is heated. Finally the water exits the tube to finish the circuit in the sink, thus the

flow rate can be regulated by the valve.

First of all, the temperature sensor T1 give us the temperature of water from the tap. Next, the water pass through the pump and the flow meter and with the temperature sensor T2 we can obtain the temperature of water just before the solar thermal panel.

After this, the sensor T3 show us the temperature of the flow out (hot water), we will assume that the temperature of the water that go out from the system is T3 too.

Finally, in the temperature sensor T4 we will see the temperature of the ambient air.



It is important to know that the inputs of the system are the QRadlight (from the lights that heat the solar thermal panel) and the W elec (that need the pump for work) and the output are the QwaterandQloss.

In the next picture, we can show a schematic diagram of the experiment.

Balance equation:

+QRadlight−Qw−QCond−QConv−QRadlight=EST

Start = fixed – zero – zero – zero – zero = high

Later = fixed – increased – increased – up – up = lower

End = fixed – high – high – high – high = very lower

Steady State = fixed – max – max – max – max = zero

Analysing the balance equation we can see that when we start the experiment all the components of the equations are negligible except QRadlight that it’s a fix value, so the temperature will increase very fast at the beginning.

Next, the other components start to increase and the temperature raise up but lower than at the beginning and finally these components get their maximum


Figure 36: Return reverse header design in evacuated tube panel

Figure 37: steady state diagram


value and the temperature remain stable. The system is now in the steady state.

3.2.3: Procedure: for the new systemWith the new system the method of operation will be: The system is divided into two circuits, the first one is a closed pressurized circuit with a pump that must be capable of establishing a flow and overcome the load losses of the circuit.

1. The direction followed by the water through the primary circuit elements is described below:

2. The water pressurized to 2 bars, is boosted by the pump and goes to the solar panel passing through the flow meter before.

3. On the solar panel, water is heated by the spot lights.4. Then water comes from the solar panel and passes through the coil

inside the tank heating the water of the tank.5. Finally water goes out of the coil and goes to the pump, starting the cycle

again.The second one is an open circuit that run with the pressure obtained from the tap. The direction followed by the water through elements is described below:

1. The cold water goes out from the tap with a pressure of 2 bars and enters to the tank.

2. In the tank the water is heated by the coil inside it due to the temperature of the water that pass through it is higher because the solar thermal collector heated it.

3. After that, the hot water goes out from the top of the tank obtain the hot water that can be used for the house demand. The flow rate is regulated by the valves.



Chapter 4: ResultsThe behavior of a solar flat thermal panel is going to be analyzed making several experiments in the lab, with the purpose of finding the thermal efficiency for the original and new system through data collected.

The first experiment was to test the efficiency of the solar flat thermal panel with the “original system” to know how it could be improved later. After that, the “new system” was built and tested comparing both results obtained, and reaching a conclusion.

Before starting the experiments, the solar radiation was measured as explained below.

4.1 Radiation:

The high intensity lights were put as close to the panel as possible, to maximize the radiation absorbed. The panel was inclined at 80º allowing the whole front surface to absorb heat from the high intensity lights and therefore all the water collector inside was heated.

The radiation that arrives to the solar thermal panel is shown on the tables below.

Table 3: Radiation along the front of the collector during the experiment.


Solar flat plate (W/m2)

460 460 470

580 560 520

620 680 690

660 730 730

660 720 670

560 650 540

380 390 430

190 200 170


510 510 490

540 560 540

650 700 640

650 710 600

580 600 580

560 610 550

360 400 350

180 200 160


The values given by radiometer oscillated a lot and therefore writing down the exact amount of radiation reached in each value so an average was taken, we did an average of the tables above to make the calculations for the next experiments.


485 485 480

560 560 530

635 690 665

655 720 665

620 660 625

560 630 545

370 395 390

185 200 165Table 4: Average irradiance at each part of the solar flat panel.

The average irradiance along the surface knowing its dimensions can be calculated as follows:

Height=1.92m

Width=0.98m

Areaof the panel=1.90×0.95=1.80m2

Averageirradiance=519.79W /m2

4.2: Original systemDuring this experiment, the flat plate solar thermal panel was tested with the original system to calculate its efficiency.

The different components of the balance equation were studied until the system reached steady state.

4.2.1 ResultsAs a result the flat-plate solar thermal collector received 519.79 W/m2, the following data was obtained:



Time of sample in [min] 0 1 2 3 4 5 6 7 8 9 10

Water from the tap T1

[ºc] 13.7 13.9 14.1 14.2 14.4 14.6 14.2 14.1 14.0 14.3 14.5

Water entering into the panel T2 [ºc] 27.7 28.0 28.4 28.9 29.2 29.5 29.9 30.2 30.6 31.1 31.6

Water leaving the panel (T3) [ºc] 28.0 29.5 34.3 37.4 40.9 43.5 45.4 47.1 49.2 53.0 55.5

Ambient air room temperature (T4) [ºc] 17.0 16.8 16.7 16.9 16.5 16.6 16.7 16.8 17.0 16.9 17.0

Table 5: Temperatures measured in the original system the first 10 minutes.

Time of sample in [min]11 12 13 14 15 16 17 18 19 20


[ºc]14.4 14.5 14.6 14.6 14.7 14.8 14.9 14.8 15.0 15.0

Water entering into the panel T2 [ºc]

31.9 32.2 32.4 32.6 32.7 32.9 33.2 33.6 33.9 34.2

Water leaving the panel (T3) [ºc]

56.9 58.2 59.4 60.5 61.4 62.3 63.7 65.0 67.0 68.5

Ambient air room temperature (T4) [ºc]

17.1 17.0 17.0 17.2 17.2 17.2 17.3 17.5 17.6 17.7

Table 6: Temperatures measured in the original system between first 10 and 20 minutes.

Time of sample in [min]

21 22 23 24 25 26 27 28 29 30


[ºc]14.9 14.7 14.6 14.9 15.1 15.0 15.3 15.2 15.1 15.2


34.6 34.9 35.5 36.1 36.6 37.0 37.2 37.5 37.8 38.1


70.0 71.4 72.6 74.0 75.5 76.5 77.4 78.4 79.2 80.0


17.9 17.8 17.9 18.0 18.1 18.0 18.1 18.2 18.1 18.0

Table 7: Temperatures measured in the original system between first 20 and 30 minutes.

It is observed that the results for the different temperatures from the tap T1 and the temperature of the ambient air T4 remain stable. However, the temperature of the water to panel T2 and the temperature of the water out T3 are increasing along the time as is expected.

The next graph represents the variation of each temperature measured along the time during the experiment.



0 5 10 15 20 25 300

10

20

30

40

50

60

70

80

90

Original System

Water from the tap T1 [ºc]




Time [min]

Tem

pera

ture

[ºC]

Figure 38: Variation of temperature along time in the Original System.

As we can see on the graph above the water leaving the panel (T3) had not arrived to a steady state yet. When the experiment was carried out the safe operating temperature had to be observed and therefore once the panel reached 80°C it was stopped in order to prevent damage to the equipment and to the people doing the experiments.

4.2.2 Calculation of thermal efficiency for the original system.

The thermal efficiency of a solar panel varies along time depending on the temperature difference between the system temperature and the room temperature.

To make the calculations the following data was taken:

Pump [W] 87

Flow rate water out of the circuit [kg s-1] 0.0038

Mass flow water out of the circuit [kg] 0.2280

Specific heat capacity of water [Jkg-1K-1] 4180

Area of the panel [m2] 1.80

Average Irradiance [W m-2] 519.79

Flow rate into the panel [kg s-1] 0.05

Mass flow into the panel [kg] 3.00Table 8: Useful data for the original system.

The instantaneous efficiency represents the efficiency of the solar panel at one precise moment of time during the experiment.



Equation 4: Solar Thermal Efficiency

η= Q¿

QRad+W pump−Qout

As an example for knowing how to calculate this value, we have taken the temperatures obtained with 4 minutes after starting the experiment shown below in table 9.

As well as the temperature increases at different parts of the circuit.

The temperature inside the panel (T5) was taken making an average between the water temperature entering into the panel (T2) and the water temperature leaving the panel (T3). Thus the amount of heat produced by the panel can be calculated as follows:

Equation 5: quantity of heat absorbed by the water

Q¿=m×Cp× ( ΔT5 )

¿0.05 [kg s−1 ] x 4180 [J kg−1K−1 ] x (1.45 [ºC ] )

= 303.05 [W]


Table 9: experimental data

Table 10: experimental data

Time of sample [min] 4

Water from the tap T1 [ºc] 14.4

Water entering into the panel T2 [ºc] 29.2

Water leaving the panel (T3) [ºc] 40.9

Ambient air room temperature (T4) [ºc] 16.5

Time of sample [min]4

ΔT leaving the panel (ΔT3) [ºC]2.60

ΔT leaving the panel, room (T4-T3)[ºC]24.40

Average entering and leaving the panel (T5) [ºC]35.05

ΔT entering and leaving the panel (ΔT5 ) [ºC]1.45


On the other hand, the amount of heat absorbed by the high intensity lights is calculated taking into account the solar flat panel area, and its incident radiation which is in m2 is measured in the equation below. Thus:

Equation 6: Incident light radiation

QRad=A x I

¿1.8 [m2 ] x519.79 [Wm−2]

= 935.62 [W]

The pump was running at its higher power, i.e.:

Equation 7: Pump power

W pump=87W

The solar flat panel was transferring heat to the water in the tank. There was a water flow rate from the tap connecting to the panel; this amount of heat can be obtained in the following way:

Equation 8: quantity of heat output out of the system due to the water flow

Qout=¿ m×Cp×(ΔT 3)

¿0.0038 [kg s−1 ] x 4180 [J kg−1K−1 ] x (2.6 [ºC ] )

= 41.29 [W]

Once all different energies which enter and leave the panel are known the instantaneous efficiency at that precise moment of time is:

Equation 9 Solar Thermal Efficiency final calculation

η= Q¿

QRad+W pump−Qout= 303.05935.62+87−41.29

=0.3088=30.88%

Repeating the calculations above for each minute along the experiment, the next graph was obtained:



10 20 30 40 50 60 70 800

0.10.20.30.40.50.60.7

Original System

Temperature difference [ºC]

Efficie

ncy

[%]

Figure 39 System efficiency over the temperature difference in the Original System.

4.2.3: Conclusion for the Original System.

As we can see on the graph above, the instantaneous efficiency of the panel fell down as the temperature difference between the panel and the ambient temperature increase due to the higher heat losses. At the end of the experiment the temperature of the system must be steady since the solar thermal panel cannot get more energy due to all the energy input is lose with the environment. This can be seen with the decreasing shape of the graph showing an efficiency of 0% when the temperature difference is very high, in other words when all the energy input is lost.

4.3 External System BuiltDuring this experiment, the flat plate solar thermal panel was tested with the External System Built to calculate its efficiency.

The different components of the balance equation were studied until the system reached steady state.

In the experiment the tank was filled full of water and there was a low flow rate in the open circuit.

4.3.1 Results

A pipette and a timer were used to measure the flow rate of the open circuit. The amount of water came out from the tap during a controlled time of 1 minute was 95 ml.

The flow rate was therefore:



Equation 10: Mass flow rate

˙mtap=95ml60 s

=1.583 mls

=0.00158 ls

The pressure inside the close circuit was measured by the manometer giving a value of 2 bars.

As a result the flat-plate solar thermal collector received 519.79 W/m2, the following data was obtained:

The results of this experiment are given below:

Time of sample [min]

0 10 20 30 40 50 60 70 80 90

Closed circuit. Water entering

into the panel T1

[ºC]

25.2 26.2 27.2 28 28.6 29.4 29.8 30.5 31.1 31.7

Closed circuit. Water leaving the

panel T2 [ºC]27.4 28.6 29.5 30.3 31 31.8 32.5 33.1 33.7 34.3

Open circuit. Water entering into the tank T3

[ºC]

15.9 17.5 18.3 18.7 18.3 18.3 18 18.2 18.4 18.5

Open circuit. Water leaving the

tank T4 [ºC]16.8 18.2 19 19.8 20.7 21.6 22.6 23.3 24 24.6

Ambient air room temperature T5

[ºC]16.8 16.9 17.2 17.9 18.3 18.4 18.9 18.9 19.3 19.7

Table 11: Temperatures measured in the first experiment along the first 90 min.


100 110 120 130 140 150 160 170 180

Closed circuit. Water entering into

the panel T1 [ºC]32.2 32.6 33.1 33.5 34 34.3 34.8 35.1 35.7


panel T2 [ºC]34.9 35.5 35.9 36.5 37 37.5 38 38.6 39

Open circuit. Water entering into the

18.7 18.6 18.4 18.5 18 18 17.6 18.3 18.8



tank (T3) [ºC]

Open circuit. Water leaving the tank T4

[ºC]25.4 26.2 27 27.5 27.8 28.7 29.4 29.6 30.5


[ºC]18.9 19 18.6 18.7 18.4 18.5 18.9 18.6 19.6

Table 12: Temperatures measured in the first experiment between min 100 and 180.


190 200 210 220 230 240 250 260 270 280


into the panel T1

[ºC]

36.2 36.7 36.9 37.2 37.5 38 38.3 38.8 38.9 39.2


panel T2 [ºC]39.4 39.9 40.2 40.7 41.2 41.4 41.9 42.3 42.5 42.8


[ºC]

18 18.6 18 18.5 18 18.1 17.8 17.9 18.4 18.8


tank T4 [ºC]30.9 31.3 31.7 32.3 32.8 33.1 33.4 33.8 34.2 34.7


[ºC]19.2 19.1 19.2 19 19.1 19.4 19.2 19.1 19.5 19.4

Table 13: Temperatures measured in the first experiment between min 190 and 280.


290 300 310 320 330 340


into the panel T1

[ºC]

39.5 39.6 39.7 39.9 40 40


panel T2 [ºC]43 43.2 43.4 43.5 43.6 43.7


18.8 19.2 19 19.1 19 18.8



[ºC]


tank T4 [ºC]35.1 35.4 35.7 36 36.4 36.6


[ºC]19.4 18.8 19 19.5 19 19

Table 14: Temperatures measured in the first experiment between min 290 and 340s

Values obtained are represented on the following graph:

0 50 100 150 200 250 300 350 4000

5

10

15

20

25

30

35

40

45

50Closed circuit. Water entering into the panel (T1)

Closed circuit. Water leaving the panel (T2)

Open circuit. Water entering into the tank (T3)

Open circuit. Water leaving the tank (T4)

Ambient air room temperature (T5)

Average tempera-ture of the tank (T6)

Time (min)

Tem

pera

ture

s ºC

Figure 40: Temperatures measured at different parts of the circuit

As we can see at the end of the experiment the temperature of the close circuit is stabilized in around 45ºC.

4.2.2 Calculation of thermal efficiency for the External System Built.

To make the calculations the following data was taken:

Pump [W] 48

V tank [l] 90

M tank [kg] 90

Specific heat capacity of water [Jkg-1K-1] 4180

Area of the panel [m2] 1.80

Average Irradiance [W m-2] 519.79

Flow rate out of the tank [kgs-1] 0.00158Table 15: Useful data for the External System Built.

The instantaneous efficiency represents the efficiency of the solar panel at one precise moment of time during the experiment.



Equation 11: Solar Thermal Efficiency

η= Q¿

QRad+W pump−Qout

As an example for knowing how to calculate this value, we have taken the temperatures obtained with 150 minutes after starting the experiment shown on the table 1.

Time of sample [min] 150

Closed circuit. Water entering into the panel T1 [ºC] 34.3

Closed circuit. Water leaving the panel T2 [ºC] 37.5

Open circuit. Water entering into the tank T3 [ºC] 18.0

Open circuit. Water leaving the tank T4 [ºC] 28.7

Ambient air room temperature T5 [ºC] 18.5

Table 16: Useful data for the External System Built.

As well as the temperature increases at different parts of the circuit.

The temperature inside the tank (T6) was taken and an average between the water temperature of the close circuit entering into the tank (T1) and leaving the tank (T2). Thus the amount of heat that arrives into to the tank can be calculated as follows:

Equation 12: quantity of heat absorbed by the water in the tank

Qtank=mtank×Cp× ( ΔT6 )

¿ 9010×60

[kg s−1 ]×4180 [J kg−1K−1 ]× (0.5 [ ºC ])

= 313.5[W]


Table 17: Useful data for the External System Built.

Time of sample [min]150

Average temperature of the tank T6 [ºC] 35.9

Temperature difference (T6 – T5) [ºC] 17.4


On the other hand, the amount of heat absorbed by the light sources is calculated taking into account the solar flat panel area, and its incident radiation by m2.Thus:

Equation 13: Incident light radiation

QRad=A x I

¿1.8 [m2 ] x519.79 [Wm−2]

= 935.62 [W]

The pump was running at its higher power, i.e.:

Equation 14: Pump power

W pump=48W

The tank was exchanging heat due to there was a water flow from the tap connecting to the tank, this amount of heat can be obtained in the following way:

Equation 15: quantity of heat output out of the system due to the water flow

Qout=¿ mtap×C p×(T 4−T 3)

¿0.00158∗[kg s−1 ] x 4180 [ J kg−1K−1 ] x (28.7−18.0)[ ºC ]

= 70.66 [W]

Once all different energies which enter and leave the system are known the instantaneous efficiency at that precise moment of time is:

η

Equation 16: Solar Thermal Efficiency final calculation

¿Qtank

QRad+W pump−Qout= 313.50935.62+48−70.66

=0.3434=34.34 %

Repeating the calculations above for each minute along the experiment, the next graph was obtained:



10 12 14 16 18 20 22 24 26 28 300

10

20

30

40

50

60

70

80

34.34

External System Built

Temperature difference [ºC]

Efficie

ncy

[%]

Figure 41: System efficiency over the temperature difference in the External System Built.

4.2.3: Conclusion for the External System Built.

As we can see on the graph above, the instantaneous efficiency of the system fell down as the temperature difference between the system and the ambient temperature increase due the higher heat losses. At the end of the experiment the temperature of the system must be stable because all the energy input (high intensity lights and pump) is equal to the energy output (heat loses and mass flow going out from the system), that is all of the energy input is lost thus the solar panel does not increase its temperature any more.

Chapter 5: Conclusion In this last chapter of the project the literature review and results obtained were analysed. Most of the project objectives were achieved.

First of all, a literature review about the solar thermal panels was done. Secondly, an evaluation of the differences between evacuated tube collector and flat-plate collector to know which panel works better in a climate like Ireland was done. After that, the external circuit for the solar thermal panel to simulate a real system in a house was built and tested.

5.1 Key findings:Analysing the results of the experiments the following outcomes were found out.



• The flow rate of the system had a big impact on the efficiency of both systems due to the more flow rate the more loses had the panel and therefore if the flow rate was too big then the efficiency would go down.

• The measuring apparatus such as the thermocouples, radiometer or the flow meter had to be calibrated in order to achieve good readings.

• When the difference of the ambient room temperature and the temperature of the system increased, the efficiency goes down due to more energy input is lose with the environment, thus when this temperature difference is so high the system becomes stable and all the energy input (high intensity lights and pump) becomes equal to the energy output (heat loses and mass flow going out from the system).

• In order to achieve good solar thermal efficiency, the losses in the system had to be minimised, insolating thermally circuit elements such as the pump, the pipes and their connections.

5.2 ConclusionAfter the study all the information we can conclude that:

On one hand, evacuated tube collectors capture sunlight better and they are less sensitive to sun orientation and angle than solar flat plates. They are more efficient in transferring heat because they have less thermal loss and they work without problems in cold, windy and humid conditions.

On the other hand, flat plate collectors are cheaper and they can be easy integrated into the roof of the building but they need higher wind load. They are more sensitive to sun angle, and their angle needs to be changed to maximize their production.

About the cost, that is typically the primary consideration. Evacuated tubes can cost around 20% to 40% more than solar flat plates, although shipping costs can be more with solar flat plates than with solar evacuated tubes, especially when ordering a package system. Another item that affects the cost is the geographic location due to the fees that change for each country.

In places where heavy snowfall can be a problem, solar evacuated tubes will not leak heat from the collector, so will not melt snow as quickly as solar flat panels. However, solar flat panels will collect heat through the reflected sunlight off snow & ice, and melt the snow much quicker.

Both collectors can have a long life span (approx. 25 years) they work in an efficient way and obtain heat energy from the sun.



Due to the solar climate weather in Ireland, and knowing the behaviour that a solar thermal evacuated and flat plate collector offers, it can be concluded that their installation on dwellings in Ireland is viable.

Analysing the results of the experiments the following outcomes were found.

• The flow rate from the tap entering into the panel had a big impact on the efficiency of both systems due to the more flow rate the more loses had the panel and therefore if the flow rate was too big then the efficiency would go down.

• The measuring apparatus such as the thermocouples, radiometer or the flow meter had to be calibrated in order to achieve good readings.

• When the difference of the ambient room temperature and the temperature of the system increased, the efficiency goes down due to more energy input is lose with the environment, thus when this temperature difference is so high the system becomes stable and all the energy input (high intensity lights and pump) becomes equal to the energy output (heat loses and mass flow going out from the system).

• In order to achieve good solar thermal efficiency, the losses in the system had to be minimised, insolating thermally circuit elements such as the pump, the pipes and their connections.

5.3 Future recommendationsIf this particular project will be continued to be studied in the next few years, the next steps will be:

Use a fan to simulate the wind across the panel. Try to build a device to focus the light uniformly onto the panel. Improve the insulation of the system. Repeat the same experiments with the evacuated tube collector and

analyse the differences.

Chapter 6: Bibliography

Bibliography



Alternative energy ireland, 2014. Alternative energy ireland. [Online] Available at: http://www.aei.ie/solar-panels[Accessed 24 febrary 2014].

Anon., n.d. do it yourself. [Online] Available at: http://www.doityourself.com/stry/how-a-circulating-pump-works#b

Anon., n.d. facstaff. [Online] Available at: http://www.facstaff.bucknell.edu/mastascu/elessonshtml/Sensors/TempThermCpl.html

Anon., n.d. seai. [Online] Available at: http://www.seai.ie/Schools/Post_Primary/Subjects/Architectural_Technology/Domestic_Heating/

Anon., n.d. solar panles plus. [Online] Available at: http://www.solarpanelsplus.com/products/solar-thermal-components/[Accessed 24 04 2014].

ASHRAE, 2003. Chapter 33. [Online] Available at: https://cours.etsmtl.ca/mec735/.../Notes.../solar_energy_ASHRAE.pdf[Accessed 6 march 2014].

blogspot, 2014. thermowell. [Online] Available at: http://2.bp.blogspot.com/_ZNZ7m9tKOBk/TT_J15ARKKI/AAAAAAAAAD8/zJG25-GOOPY/s640/A%2BThermowell.jpg[Accessed 24 febrary 2014].

Dorfling C.D, Hornung C.H.H,Hallmark B.H, Beamount R.J.J.B,Fovargue H.F, Macklley M.R.M, 2010. The experimental response and modelling of a solar heat collector fabricated from plastic films. Solar Energy Materials and Solar Cells (Elsevier), Issue 94, pp. 1207-1221.

Elementary Energy Ireland, 2009. Elementary Energy Ireland. [Online] Available at: www.elementaryenergy.ie[Accessed 24 febrary 2014].

European Comission, 2009. National Action Renewable Energy Action Plan For Ireland. [Online] Available at: http://ec.europa.eu/energy/renewables/action_plan_en.htm[Accessed febrary 24 2014].



European Solar Thermal Industry Federation, 2012 . Solar Thermal Markets in Europe, Brussels: European Solar Thermal Industry Federation.

Facstaff, 2014. Temperature Sensor - The Thermocouple. [Online] Available at: http://www.facstaff.bucknell.edu/mastascu/elessonshtml/Sensors/SensorTCVM.gif[Accessed 24 febrary 2014].

G.W Burns and M.G Scroger, 1989. The Calibration of Thermocouples and Thermocouple Materials. [Online] Available at: www.nist.gov/calibrations/upload/sp250-35.pdf[Accessed 24 febrary 2014].

Heliodyne, 2010. Solar Flat Plate vs Evacuated Tube Collectors. [Online] Available at: http://wwheliodyne.com/industry_professionals/downloads/Evacuated%20Tube%20Comp.pdf[Accessed 24 febrary 2014].

Inds, 2014. Series_FR4500_Acrylic_Flowmeter. [Online] Available at: http://www.inds.co.uk/flow/flow_images/Series_FR4500_Acrylic_Flowmeter_large.jpg[Accessed 28 april 2014].

ISA, 1961. www.automationfederation.org. [Online] Available at: www.automationfederation.org/Content/.../Standards.../RP_166.pdf[Accessed 24 febrary 2014].

Kalogirou, Soteris A., 2004. Process In Energy And Combustion Science. Solar thermal collectors and applications, Volume 30, pp. 231-295.

Kingspan Renewables Ltd, 2011. Dispelling the Solar Myth – Evacuated Tube vs Flat Plate Panels. [Online] Available at: http://www.seai.ie/Renewables/REIO/SEAI_REIO_2011_Events/EU_Solar_Days,_Wexford,_11_May_2011/William_Comerford,_Kingspan_Renewables_EU_Solar_Days_Presentation.pdf[Accessed 24 febrary 2014].

L.M. Ayompe, A. Duffy, S.J. McCormack, M. Conlon, M.Mc Keever, 2011. Comparitive Field Performance Study of Flat Plate and Heat Pipe Evacuated Tube Collectors for Domestics Water Heating Systems in a Temperature Climate, Dublin: Elsevier .



Magnumpropumps, 2014. http://marineinsight.com. [Online] Available at: http://www.magnumpropumps.com/wp-content/uploads/2011/10/m-10_2-500x300.jpg[Accessed 24 febrary 2014].

Marineinsight, 2014. Thermocouple-Circuit. [Online] Available at: http://marineinsight.com/wp-content/uploads/2011/03/Thermocouple-Circuit.jpg[Accessed 24 febrary 2014].

Met Eireann , 2014. Met Eireann. [Online] Available at: http://www.met.ie[Accessed 24 Febrary 2014].

Omega, 2014. Introduction to Thermocouples. [Online] Available at: http://www.omega.com/prodinfo/images/TC_CommonTempRanges_Long.gif [Accessed 24 febrary 2014].

Pure Energy Technology Ltd., 2014. Pure Energy Technology Ltd.. [Online] Available at: http://www.pet.ie/solar-faqs[Accessed 24 febrary 2014].

SEAI, 2012. Triple E Eligibility Criteria. [Online] Available at: www.seai.ie/.../Triple_E.../Triple_E...Criteria/Solar_Thermal_Collectors[Accessed 28 march 2014].

SEAI, 2014. seai. [Online] Available at: http://www.seai.ie [Accessed 24 Febrary 2014].

Solar Server , 2014. Solar server. [Online] Available at: http://www.solarserver.com/uploads/pics/flachkollektor-e.gif[Accessed 28 febrary 2014].

Sunil.K.Amrutkar, Satyshree Gholdke,Dr.K.N.Patil, 2012. Solar Flat Plate Collector Analysis. IOSR Journal of Engineering, 2(2), pp. 207-213.

Sustainable Energy Authority of Ireland , 2013. Energy in Ireland 1990-2012, Dublin : Sustainable Energy Authority of Ireland .

T. Christoph, W. Zörner, C. Alt, C. Stadler,, 2005. Performance of Vacuum Tube and Flat Plate Collectors Concerning Domestic Hot Water Preparation and Room Heating. [Online] Available at:



http://www.thermo-dynamics.com/pdfiles/technical/Solar_Performane_VTvsLFP.pdf[Accessed 24 febrary 2014].

The Worlds of David Darling, 2009. Encyclopedia of Alternative Energy. [Online]

Available at: http://www.daviddarling.info/encyclopedia/F/AE_flat_plate_solar_thermal_collector.html[Accessed 24 febrary 2014].

University of Strathclyde Glasgow, 2014. Domestic Solar Water Heating. [Online] Available at: http://www.esru.strath.ac.uk/EandE/Web_sites/09-10/Hybrid_systems/solar-thermal.htm[Accessed 24 febrary 2014].

Uteco, 2014. Tolerance Classes for Thermocouple. [Online] Available at: http://www.uteco.eu/1.7/images/tolerance_Classes_for_thermocouples_1.jpg[Accessed 24 febrary 2014].

Valgroup, 2014. www.valgroup.es. [Online] Available at: http://www.valgroup.es/carac/91403601.pdf[Accessed 24 febrary 2014].

Vettrivel H.V, Dr. Mathiaragan, 2013. Experimental Study on a Flat Plate Solar Collector. International Journal ofg Merchanical Engineering and Research (ISSN), Issue 3, pp. 641-646.

Walsh S, 2012. A Summarry of Climate Averages for Ireland. Climatological Note No.14 , p. 412.

Weather and Climate, 2013. Average Sunshine in Dublin, Ireland. [Online] Available at: http://www.weather-and-climate.com/[Accessed 24 febrary 2014].

Yunus A.C, John M.C, Robert H.T , 2012. Fundemantals of Thermal-Fluid Sciences. 4th ed. New York: McGraw-Hill .


Appendix

Chapter 7: Appendix

7.1 Experimental results for the original system (Test 2)

Test 2 flat plate old system

Sample No. 1 2 3 4 5 6

Time of sample 0 5 10 15 20 25

Water coming from the tap (T1) 10.2 10.4 10.7 10.5 11.4 11

Water coming from the tapinto the panel (T2)

23.6 25.2 25.6 26 26.5 26.8

Water coming outfrom the panel (T3)

32.3 50.3 58.6 64.7 73.1 79.6

Ambient roomair temperature (T4)

16.8 19.2 19.3 20.1 20.1 19.9

Flow rate (kg/s) 0.025 0.025 0.025 0.025 0.025 0.025

Table 18: Experimental data results (test 2)

0 5 10 15 20 25 300

10

20

30

40

50

60

70

80

90

Water form tap (T1)Linear (Water form tap (T1))Water to panel (T2)Linear (Water to panel (T2))Water out (T3)

Time (in minutes)

Tem

pera

ture

in d

egre

es(°C

)

Figure 42: Second experiment graph result (old system)

7.2 Experiment result External System Built: tank filled with 10 litters of water and no flow rate in the second circuit:

Time (min) 0 5 10 15 20 25 30 35 40 45 50 55 60

Cold close circuit T1 19,5 24,4 27,8 30,7 32,7 34,5 36,2 37,3 38,3 39,6 40,2 40,9 41,9

Hot close circuit T2 19,5 25,9 29,5 32,9 35,3 37,3 39,1 40,4 41,7 43 44,1 44,8 46

T room 15,5 15,2 16 16,9 17,2 17,9 18,3 18,4 18,9 18,9 19,3 19,7 18,9Table 19 Temperatures measured in the second experiment along the first hour.

Time (min) 65 70 75 80 85 90 95 100 105 110 115 120

Cold close circuit T1 42,4 43 43,3 44 44,6 45,2 45,6 46,2 46,3 46,6 46,8 47

Hot closecircuit T2 46,8 47,2 47,8 48,3 49,1 49,7 50,4 50,9 51,3 51,7 51,8 52

T room 19 18,6 18,7 18,4 18,5 18,9 18,6 19,6 19,2 19,1 19,2 19

Time (min) 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200

Cold close circuit

T1

47,4 47,6 48 48,4 48,5 48,8 49,3 49,4 49,6 49,6 49,8 50 51,4 51,6 51,8 52

Hot close circuit

T2

52,1 52,3 52,6 53,2 53,7 54,2 54,5 54,7 55,2 55,3 55,3 55,4 56 56,3 56,5 56,5

T room 19,1 19,4 19,2 19,1 19,5 19,4 19,4 18,8 19 19,5 19,4 19,5 19,4 19,3 19,6 19,4

Table 20 Temperatures measured in the second experiment along the second hour.

Table 21: Temperatures measured in the second experiment from the second hour till the stabilization of T2.


0 50 100 150 200 2500

10

20

30

40

50

60

Cold close circuit T1 Hot close circuit T2 T room

Time (min)

Tem

pera

ture

(ºC

)

Figure 43: Temperatures measured at the closed circuit along the time with 10 litres of water inside the tank and no flow rate in the second circuit.

7.3 Experiment result External System Built: Tank empty of water and no flow rate in the second circuit:

Time (min) 0 5 10 15 20 25 30 35 40 45 50 55 60

Cold close circuit T1 17,6 22,5 27,2 29,8 33,3 35.5 37.5 39,3 41,8 42,7 43,5 44,6 45,6

Hot close circuit T2 18,3 23,1 28,7 32,2 36 38,9 41,2 43,5 45,4 46,5 47,7 49,3 49,8

T room 14,4 14,8 15,4 16,2 17,2 17.4 18 19 19,3 19,2 19,3 20,2 19,4Table 22: Temperatures measured in the third experiment along the first hour

Time (min) 65 70 75 80 85 90 95 100 105 110 115 120 125 130

Cold close circuit T1 46.5 47,6 48,3 48,9 49,7 50,5 51,2 52,1 52,3 52,7 52,7 52,6 52,5 52,6

Hot close circuit T2 50.9 51,2 52,5 53,3 54,2 55 55,7 56,4 56,5 56,7 57,2 57,4 57,5 57,4

T room 19.5 19,3 20,6 20,5 20,5 20,4 19,9 20 20,2 19,5 20 19 19,5 18,5Table 23: Temperatures measured in the third experiment from the first hour till the stabilization of T2.


0 20 40 60 80 100 120 1400

10

20

30

40

50

60

70

Cold close circuit T1 Hot close circuit T2 T room

Time (min)

Tem

pera

ture

(ºC

Figure 44: Temperatures measured at the closed circuit along the time with no water inside the tank and no flow rate in the second circuit.

Documents

project_final 6.1