Energy Efficiency of Buildings

8/9/2019 Energy Efficiency of Buildings

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2003

Energy Efficiency of

BuildingsMeasures to make Buildings Green

Ashutosh Agrawal

The following paper was submitted and presented at IIT, Madras during my Build

India Scholarship Training program with Larsen & Toubro, ECC Division.

Ashutosh Agrawal

Email: [email protected], Blog: www.frontiers2explore.blogspot.com, LinkedIn: www.linkedin.com/in/itsmeashu/


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BUILDING TECHNOLOGY

AND

CONSTRUCTION MANAGEMENT DIVISION

DEPARTMENT OF CIVIL ENGG, IIT MADRAS

CE506: Industrial Seminar

Course Faculty: Dr. K. Ramamurthy

Report on

ENERGY EFFICIENCY OF BUILDINGS

By:

Ashutosh Agrawal

M.Tech, CT&M

CE02M086


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ENERGY EFFICIENCY OF BUILDINGS

Ashutosh Agrawal (CE02M086)

ABSTRACT

After oil crisis of 1973, ways to limit energy usage were looked for. Buildings

turned out to be a viable candidate. Currently buildings amount to 20% of total

energy consumption. This report discusses various measures, which can be

taken to improve energy efficiency of buildings. To justify the implementation of

these measures, cost and savings associated with it has been discussed.

INTRODUCTION

In buildings, energy efficiency means using minimum energy to provide

appropriate internal environment without sacrificing the quality of that

environment. It implies, using less energy for heating, cooling, and lighting. It

also means buying energy-saving appliances and equipment for use in abuilding.

Energy efficiency first gathered importance after oil embargo of 1973. Since

then significant improvements have been made in this field.

Used energy results in

Global warming. Depletion of finite fossil fuels. Air pollution and environmental damage. Costs money.Hence, improving efficiency of energy use has its social, economic and environmental

benefits.


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BUILDING ENVELOPE

Walls, roofs, floors, windows, and doors constitute the envelope of a building.Various measures can be applied to envelope of a building to improve energy

efficiency. Some commonly recommended measures are:

a. Addition of thermal insulationAddition of thermal insulation reduces transmission losses. This results in

reduction in heating and cooling loads.

b. Replacement of windowsWhen windows represent a significant portion of exposed building surfaces,

energy efficient windows should be opted for.

Energy efficiency of window can be increased by [1]:

1. Insulating the spacers between glass panes to reduce conductionheat transfer.

2. Installing multiple coating to reduce heat transfer by radiation.3. Inserting argon or krypton gas between the panes can decrease the

convection heat transfer.

4. Providing exterior shading devices.Some new technologies in this area are [1]:

Chromogenic Glazings which change properties automatically, depending

on temperature or light level (similar to photochromatic glasses).

Integrated Photovoltaic Panels that can generate electricity while absorbing

solar radiation and reducing heat gain (typically used in roofs).

c. Reduction of air leakageLeaks in walls through frames of windows, electrical outlets, plumbing operations

etc constitute major source of air leakage. Some techniques to improve air

tightness of a building are [1 ]:

1. Caulking: Caulking materials like urethane, latex and polyvinyl can beapplied to seal various leak sources, like around window, door frame,

holes for pipes etc.

2. Weather Stripping: By applying foam rubber with adhesive backing,windows and doors can be air sealed.


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3. Landscaping: This consists of planting shrubs and/or trees around thebuilding.

4. Air Retarders: These can be applied around the building exterior shell toform a continuous wrap around the building walls. Some air retarder

types are liquid applied bituminous, liquid applied rubber, sheet

bituminous, and sheet plastic.

ELECTRICAL SYSTEMS

Electrical systems consume major part of energy in buildings:

a.LightingLighting constitutes on average 40% of total electrical energy use in a typical

office building [1].

Some advances in this area are:

1. High efficiency fluorescent lamps I" 11: Their efficacy is about 70-80lumens/watt. These have diffuse light distribution, and long operating life.

2. Compact halogen lamps f l ] : These are used as direct replacements ofincandescent lamps. These produce white light, last longer and are 30%

more efficient.

3. Electronic Ballasts [T1: Ballasts provide the voltage level required to startelectric arc and regulate the intensity of the arc.

4. Electronic Ballasts use so-lid state technology and produce high frequency(20-60 MHz) current. As a result light is cycling more quickly and appears

brighter. These Ballasts have high power factor, less flicker and less noise.

5. Automatic light controls HI: These controls and operate lighting system inaccordance with required illumination.

Occupancy sensors: These sensors save light by automatically turningoff lights in spaces that are not occupied. Currently two types of

motion sensing technologies are available in market, which are

Infrared sensors and Ultrasound sensors.


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Light Dimming Systems: Dimming controls allow the variation ofintensity of lighting system output based on natural lighting level,

manual adjustments and occupancy.

b. Electrical Appliances1. Office Equipment: almost all office equipment have power management

systems integrated in them. For instance, computer can enter low-power

"sleep" mode when idle for a specific period of time. Copiers can go in low

power mode of 15-45 Watts after 30-90 minutes of inactivity.

2. Residential Appliances: Minimum energy efficiency standards have beenset for various appliances in various countries. The energy standards are in

terms of maximum allowable energy consumption in a year for an

appliance. US have come up with these standards for every appliance and

compliance to them is mandatory [1]. In India, energy-efficiency standards

are available for Refrigerators. Room Air conditioners and Central Air

Conditioning. The compliance status is voluntary in India.

c. MotorsThe energy cost to operate motors is significant for any commercial or

industrial building. Energy efficiency in motors can be improved by [1]:

1. Reducing operating time. Turning it off when not in use.2. Better design and use of better materials to reduce losses.3. Adjustable Speed Drives: ASD's can change speed of AC motors with no

moving parts. ASD's are electronic solid state devices, which convert the

fixed-frequency AC power supply (50-60 Hz) first to a DC power and then

to a desired variable frequency AC power.


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HVAC SYSTEMS

The energy use due to HVAC systems are up to 40% of total energy consumed

by a typical commercial building [1].

Some measures to increase energy efficiency of HVAC systems are [1]:

a. Changing thermostat temperatures: During unoccupied periods,thermostat temperature can be lowered in case of heating and can be

increased in case of cooling.

b. Variable Air Volume Systems: Existing systems use constant air volumesystems. In these systems the cooled air is heated at end, to meet requiredthermal loads.

On other hand variable air volume systems reduce the amount of air supplied

as cooling load decrease, eliminating the energy consuming reheating

systems.

c. Retrofit of Central Heating Plants: Energy efficient boilers can replace oldboilers. The efficiency of a boiler can be drastically improved by adjusting

the fuel-air ratio for proper combustion.

d. Retrofit of Central Cooling Plants: Chillers, that are energy efficient andeasy to control to operate can be retrofitted.

e. Heat Recovery Systems: In heating systems the exhaust hot air, or heatfrom boiler stacks can be used to heat up outdoor intake air through a heat

exchanger.

Similarly, in cooling systems the exhaust air (relatively cooler than outdoor air) can

be used to cool the outdoor intake air.

f. Thermal Energy Storage (TES) Systems use less expensive off-peakpower to recharge a storage system. For instance, operating refrigerating

plant in off-peak hours to convert water into ice and storing it. The storage

system is discharged during on-peak hours. As a result a significant portion

of on-peak demand is shifted to off-peak demand. Cost savings are realized

because utility rates favour levelled energy consumption.


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COMPRESSED AIR SYSTEMS

Compressed air has become an indispensable tool for most manufacturing

facilities. It is estimated that only 20-25% of input electrical energy is delivered

as useful compressed air energy. Leaks accounts for 10-15% of waste and

misapplication accounts for 5-40% [1].

Some energy conservation measures for compressor systems are:

a. Reduction of inlet air temperature.b. Reduction of discharge pressure. When the maximum pressure required by all

end use equipment is noticeably less than air pressure developed bycompressor system, the discharge pressure of the compressor must be

reduced to reduce its energy use.

c. Repair of air leaks. Leaks result in unnecessary waste of compressed air.

ENERGY MANAGEMENT CONTROL SYSTEM (EMCS)

With the constant decrease in the cost of computer technology, automated control of a

wide range of energy systems within commercial and industrial buildings is becomingincreasingly popular and cost-effective. An energy management and control system

(EMCS) can be designed to control and reduce the building energy consumption within

a facility by continuously monitoring the energy use of various equipment and making

constant adjustments.

Two approaches for EMCS are typically applied [1]:

a. Load Tracking: The actual need of a facility is determined by continuouslymonitoring it through sensors. Then operation of equipment is modulated in

respond to actual needs in the facility.

b. Load Anticipation: Here the needs of facility are predicted by analyzinghistorical pattern of load variations. Then the operation of equipment is

modulated accordingly.


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COGENERATION [1]

The process of generating both electrical and thermal energy is generally

referred as cogeneration. Electricity is produced from fuel and waste thermal

energy is recovered in form of hot water or steam, which is then used to meet the

heating load in a building.

WATER MANAGEMENT

In recent years, the cost of water usage has increased significantly and represents

an important fraction of total utility bills.

Water conservation strategies are grouped in three main categories[1]:

a. Indoor Water Management: Use of water efficient plumbing systems likewater-saving showerheads, water-saving toilets and water-saving faucets.

Repair of water leaks and use of water efficient appliances (clothes washer,

dishwashers etc.).

b. Outdoor Water Management: Use of low flow sprinkler heads. Replacingall or part of a landscape with less water dependent components such as

rocks and indigenous vegetation, known as Xeriscaping. Use of drip system

to water plants etc.

c. Waste Water Reuse: Gray water is a form of waste water with lesser quality thanpotable water but higher quality than black water (which contains significant

concentration of organic waste from toilets and kitchen). Gray water comes from

washingmachines, baths and showers and is suitable for reuse in toilet

flushing. In addition, it can be used to supply of some irrigation needs, as it

contains nitrogen and phosphorus, which are essential plant nutrients.

Rainwater of which much is wasted can be can be conserved by wide range

of harvesting systems to collect and distribute water.


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LANDSCAPING AND ORIENTATION

Landscaping implies controlling surrounding landscape by planting trees,

shrubs, vines, grasses, and hedges. A well-designed landscape will:

Cut your summer and winter energy costs dramatically. Protect your home from winter wind and summer sun. Reduce consumption of water, pesticides, and fuel for

landscaping and lawn maintenance.

Help control noise and air pollution.Shading and Evapotranspiration (the process by which a plant actively movesand releases water vapour) from trees can reduce surrounding air temperatures

as much as 9 F (5C) [6].

Proper orientation and landscaping can boost up energy efficiency considerably.

In the northern hemisphere, it is usually best to align the home's long axis in an

east-west direction. The home's longest wall, with the most window area, should

face south or southeast. The home's north-facing and west-facing walls should

have fewer windows because these walls generally face winter's prevailing

winds. North-facing windows receive little direct sunlight [6].

Solar heat passing through windows and being absorbed through the roof is the major

reason for air-conditioner use. Shading is the most cost-effective way to reduce solar

heat gain and cut air conditioning costs.

Trees can be selected with appropriate sizes, densities, and shapes for almost any

shading application. To block solar heat in the summer but let much of it in

during the winter, use deciduous trees [6]. To provide continuous shade or to

block heavy winds, use evergreen trees or shrubs. Deciduous trees with high,

spreading crowns (i.e., leaves and branches) can be planted to the south of your

home to provide maximum summertime roof shading. Trees with crowns lower

to the ground are more appropriate to the west, where shade is needed from

lower afternoon sun angles [6].

During the summer, tall spreading trees planted close to the home shade the roof.

Broad, shorter trees on the west side block afternoon solar heat. A windbreak on


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the northwest side can shield the home from prevailing winter winds [6].

Trees, shrubs, and groundcover plants can also shade the ground and pavement

around the home. This reduces heat radiation and cools the air before it reaches

your home's walls and windows.

Wind Protection

The best windbreaks block wind close to the ground by using trees and shrubs

that have low crowns. For maximum protection, plant your windbreak at a

distance from your home of two to five times the mature height of the trees [1],

If snow tends to drift in your area, plant low shrubs on the windward side of yourwindbreak. The shrubs will trap snow before it blows next to your home.

During the summer, tall spreading trees planted close to the home shade the roof.Broad shorter trees on the west side block afternoon solar heat. A windbreak on thenorthwest side can shield the home from revailin winter winds.


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COST FACTOR

Everybody loves energy-efficient homes. There is clear evidence that energy

efficiency is a great long-term investment, and requires initial additional

construction cost.

Various programs already underway are listed below. An effort called "Building

America" is now underway to find ways to cut energy use by 50 percent

compared to current practice without increasing overall construction cost [5].

The State of Iowa's Department of Natural Resources (DNR), established an

ambitious Building Energy Management Program to install all energy

management improvements with an average payback of 6 years in all public and

non-profit facilities statewide by

1995. The DNR predicted such a program would require a $300 million

investment, create energy savings of $50 to $60 million a year, i.e. around 16%

overall improvement in energy efficiency [3].

State Committee of Ukraine for Energy Conservation, U.S. Department of

Energy has implemented a program for more than 1,300 educational, healthcare

and cultural buildings. Payback period is about 7 years. Recommended measures

lower energy consumption by about 27% of baseline consumption [4].

A program called Energy Bank in U.S. has improved energy efficiency of

various official and unofficial buildings, puts it like this. For every $1 million

To cool the south and west sides of the home,reduce paved areas, plant shade trees, or add atrellis


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investment in energy efficiency, $167,000 is saved in energy costs annually. In

six years, that initial investment is repaid [5].

CONCLUSION

Now one can appreciate that there is a wide scope for improvement in energy

efficiency of a building. Some of the measures are for free and some call for

initial investment. But with payback periods ranging from 3-12 years, they are

worth investing. With depleting resources, its imperative to concentrate on

reducing energy cost. No other area could be better than buildings, which

currently account for 20% of total energy consumption and also provide a goodscope to control its energy consumption.


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REFERENCES

1. Krarti Moncef, "Energy Audit Of Building Systems", Florida, CRC Press2000.

2. "Energy Bank",http://www.state.ia.us/dnr/energy/pubs/bem/EnergyBank.pdf, (12 Feb 2003).

3. "The Building Energy Management Program",http://www.iclei.org/cases/e006-bem.htm, (12 Feb 2003).

4. "Agency For Rational Energy Use And Ecology ",http://www.arena-eco.kiev.ua/en/project/building.htm, (21 Mar 2003).

5. "Rebuild America", http://www. rebuild.org, (21 Mar 2003).6. "Landscape For Energy Efficiency",

www.eere.enerqy.gov/erec/factsheets/landscape.pdf. (10 Mar 2003).

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Energy Efficiency of Buildings