WELCOME to PRESENTATION on SOLAR THERMAL ENERGY

byRAKTIM SAIKIA

Department of EnergyB.Voc 1st semester (2016)

TEZPUR UNIVERSITY

Solar thermal energy (STE) is a form of energy and a technology for harnessing solar energy to generate thermal energy or electrical energy for use in industry, and in the residential and commercial sectors.

What is it?

At FirstAt first AUGUSTIN MOUCHOT in 1878 UNIVERSAL EXHIBITION in PARIS demonstrated a solar collector with a cooling engine making ice cream.

Electricity is genearted from solar thermal energySolar thermal power plants use the sun's rays to heat a fluid to high temperatures. The fluid is then circulated through pipes so that it can transfer its heat to water and produce steam. The steam is converted into mechanical energy in a turbine, which powers a generator to produce electricity.

SOLAR THERMAL ENERGY STORAGEThermal energy storage (TES) TES are high-pressure liquid storage tanks used along with a solar thermal system to allow plants to bank several hours of potential electricity.

1.Two-tank direct system: solar thermal energy is stored right in the same heat-transfer fluid that collected it.

2.Two-tank indirect system: functions basically the same as the direct system except it works with different types of heat-transfer fluids

3.Single-tank thermocline system: stores thermal energy as a solid, usually silica sand.

Types of solar thermal power plants

A. Parabolic trough

B .Solar Dish

C .Solar Power tower

A

B

C

PARABOLIC TROUGHA parabolic trough is a type of SOLAR THERMAL COLLECTOR that is straight in one dimension and curved as a parabola in the other two, lined with a polished metal mirror. The energy of sunlight which enters the mirror parallel to its plane of symmetry is focused along the focal line, where objects are positioned that are intended to be heated.

PARABOLIC TROUGH EFFICIANCYIt is used to predict the performance of a given parabolic trough and compare competing technologies. NREL tests show the Sky Trough's thermal efficiency at 350 °C (662 °F) to be over 73%, meaning that nearly three quarters of the solar radiation striking the trough surface is converted into thermal energy. 

Parabolic Trough DesignA parabolic trough is made of a number of solar collector modules (SCM) fixed together to move as one solar collector assembly (SCA). A SCM could have a length up to 15 metres (49 ft) or more. About a dozen or more of SCM make each SCA up to 200 metres (660 ft) length. Each SCA is an independently tracking parabolic trough.

SOLAR DISHA solar thermal DISHcollector collects heat by absorbing sunlight. A collector is a device for capturing solar radiation. Solar radiation is energy in the form of electromagnetic radiation from the infrared(long) to the ultraviolet (short) wavelengths. The quantity of solar energy striking the Earth's surface (solar constant) averages about 1,000 watts per square meter under clear skies, depending upon weather conditions, location and orientation.

SOLAR DISH MECHANISMSolar Dish engine systems use mirrored dishes (about 10 times larger than a backyard satellite dish) to focus and concentrate sunlight onto a receiver. As shown in Figure 5, the receiver is mounted at the focal point of the dish. To capture the maximum amount of solar energy, the dish assembly tracks the sun across the sky. The receiver is integrated into a high-efficiency "external" combustion engine. 

Contd.

The engine has thin tubes containing hydrogen or helium gas that run along the outside of the engine's four piston cylinders and open into the cylinders. As concentrated sunlight falls on the receiver, it heats the gas in the tubes to very high temperatures, which causes hot gas to expand inside the cylinders. The expanding gas drives the pistons. The pistons turn a crankshaft, which drives an electric generator. The receiver, engine, and generator comprise a single, integrated assembly mounted at the focus of the mirrored dish.

SOLAR POWER TOWER

The solar power tower, also known as 'central tower' power plants or 'heliostat' power plants or power towers, is a type of solar furnace using a tower to receive the focused sunlight. It uses an array of flat, movable mirrors (called heliostats) to focus the sun's rays upon a collector tower (the target).

SOLAR POWER TOWER MECHANISM

The technology uses many large, sun-tracking mirrors commonly referred to as heliostats to focus sunlight on a receiver at the top of a tower. A heat transfer fluid heated in the receiver is used to generate steam, which, in turn, is used in a conventional turbine-generator to produce electricity.

ADVANTAGES of SOLAR THERMAL ENERGYNo Fuel Cost – Solar Thermal Energy does not require any fuel like most other sources of renewable energy. This is a huge advantage over other fossil fuels whose costs are increasing at a drastic  rate every year. Electricity prices are increasingly rapidly in most parts of  the world much faster than general inflation. Price shocks due to high fuel costs are a big risk with fossil fuel energy these days.Predictable, 24/7 Power -Solar Thermal Energy can generate power 24 hours a day. This is made possible as solar thermal power plants store the energy in the form of molten salts etc. Other forms of Renewable Energy like Solar PV and Wind Energy are intermittent in nature. The electricity supply is much more uniform and reliable.

 No Pollution and Global Warming Effects – Solar Thermal Energy does not cause pollution which is one of the biggest advantages. Note there are costs associated with the equipment used to build and transport Solar Thermal Energy Equipment.

 Using Existing Industrial Base – Solar Thermal Energy uses equipment like solar thermal mirrors and turbines which is made in large scale at low cost by the existing Industrial Base and requires no major changes in equipment and materials unlike new technologies such as CIGs Panels.

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DISADVANTAGES of SOLAR THERMAL ENERGY High Costs – Solar Thermal Energy costs at least Euro 3.5/watt and has not declined too much in the last 3-4 years. However these costs are too high  as Solar PV already costs Euro 2.5/watt and even on a conservative basis will have its costs reduced by 5% in the next 10 years making it attain half the cost of Solar Thermal Technology by 2020.Water Issue – Solar Thermal Plants use lots of Water which is Major Problem in Desert Areas. Using non-water cooling raises the cost of CSP projects too much. While using Sea Water has been proposed it remains to be seen if it possible to implement this solution as this would imply building Plants very near the Coastline.

 Ecological and Cultural Issues – The Usage of Massive Arrays of Mirrors is noted to heavily impact the Desert  Wildlife endangering the endangered species. California has already seen a massive fight on this issue with Project Developers curtailing the size of their Plants and spending money to move the wildlife.

Contd.

Limited Locations and Size Limitations – Solar Thermal  Energy can only be built in places which have the high amount of solar radiation. They can be built in deserts mostly and require a large land area. This means its not possible to build them in populated areas. Solar Thermal Energy also can only be built in large sizes which are at least 50 MW in size to be economical. This contrasts to Solar PV which is sold in sizes as low as 5 Watts.

LOAD by DEMANDThis load curve diagram shows that much of the electricity demand is in fact for continuous 24/7 supply (base-load), while some is for a lesser amount of predictable supply for about three quarters of the day, and less still for variable peak demand up to half of the time; Some of the overnight demand is for domestic hot water systems on cheap tariff. With overnight charging of electric vehicles it is easy to see how the base-load proportion would grow, increasing the scope for nuclear and other plants which produce it. Source: Vencorp

ROADMAP to 2050The roadmap emphasises that solar thermal cooling technology can fully or partially replace conventional electrically powered air conditioners in buildings.  As well as this, there are several industry sectors requiring significant energy demand for low- and medium-temperature heat in such processes as washing, drying agricultural products, pasteurisation and cooking.

Contribution of SOLAR THERMAL ENERGY

  Solar Thermal power has grown at a similarly impressive rate

SOLAR THERMAL ENERGY IN INDIA

India is densely populated and has high solar insolation, an ideal combination for using solar thermal power in India. One of the first applications of solar power has been for water pumping, to begin replacing India's four to five million diesel powered water pumps, each consuming about 3.5 kilowatts, and off-grid lighting.Graph show solar thermal resources in india.

SOLAR THERMAL CAPACITY in INDIA

According to GOVT. record 3743.97 MW solar power in india till Mar-2015

FURTHER DEVLOPMENT-THERMAL CHIMNEYS

Thermal chimneys are passive solar ventilation systems, which means they are non-mechanical.

Typically made of a black, hollow thermal mass with an opening at the top for hot air to exhaust. 

Inlet openings are smaller than exhaust outlets and are placed at low to medium height in a room. When hot air rises, it escapes through

the exterior exhaust outlet, either to the outside or into an open stairwell or atria.

• Turbines similar to those used in hydroelectric power plants convert the air flow into mechanical energy.

CONCLUSION In the face of global warming, rising fuel costs and an ever-growing demand for energy, energy needs are expected to increase by nearly the equivalent of 335 million barrels of oil per day, mostly for electricity. By concentrating solar energy with reflective materials and converting it into electricity, modern solar thermal power plants, if adopted today as an indispensable part of energy generation, may be capable of sourcing electricity to more than 100 million people in the next 20 years.In caes of economical point of view , intitial costs are very high, but for UNDEVLOPED and DEVLOPING countries it creates a avenue to EMPLOYBILITY. All from one big renewable resource: THE SUN.

REFERENCEShttps://en.wikipedia.org/wiki/Solar_power_in_Indiahttp://www.greenworldinvestor.com/2011/07/07/advantages-and-disadvantages-of-solar-thermal-energy-power-towersparabolic-troughs/

https://cleantechnica.com/2013/11/07/renewable-energy-charts-renewable-energy-facts/

http://www.green-peninsula.com/2012/08/use-of-solar-energy-hotting-up/

http://www.greenmatch.co.uk/blog/2014/08/5-advantages-and-5-disadvantages-of-solar-energy

http://www.unsam.edu.ar/tss-eng/advantages-of-solar-thermal-energy/

http://solareis.anl.gov/guide/solar/csp/