Prepared by: Manjushree Sthapit
Building Science-II
LECTURE 1
Energy:
Energy is the potential or capacity for carrying out certain work. Energy can be observed in many
forms like heat or thermal, light, mechanical, electrical, chemical, and nuclear energy. There are two
types of energy: stored (potential) energy and working (kinetic) energy. All forms of energy are
stored in different ways, in the energy sources that we use every day. These sources are divided into
two groups: renewable and nonrenewable. Renewable and nonrenewable energy sources can be used
to produce secondary energy sources including electricity and hydrogen.
Renewable Energy
 It can be replenished in a short period of time
Non-renewable Energy
 It cannot recreate in a short period of time
 It is continuous or recurring in nature
 It is not continuous or recurring in nature
 It is secure and inexhaustible
 It is insecure source of energy
 It is locally available
 Maximum dependency on foreign resources
 It is environmentally friendly as it doesn’t  It releases harmful gas and pollutants during
release harmful gas and pollutants during
operation
operation
 Renewable energy sources include solar  Nonrenewable energy sources include the
energy, which comes from the sun and can be
fossil fuels like: oil, natural gas, and coal.
turned into electricity and heat. Wind,
Another nonrenewable energy source is the
geothermal energy from inside the earth,
element uranium, whose atoms we split
biomass from plants, and hydropower from
(through a process called nuclear fission) to
water are also renewable energy sources.
create heat and ultimately electricity.
Sources of energy:
1. Solar Energy
Solar energy refers to energy that is collected from sunlight.Solar Energy is the most inexhaustible,
cleanest and free source of energy. Solar radiation along with secondary solar resources such as wind
and wave power, hydroelectricity and biomass account for most of the available renewable energy
on Earth.
Solar power provides electrical generation by means of photovoltaics. Another applications includes
space heating and cooling through solar architecture, potable water through distillation and
disinfection, daylighting, hot water, thermal energy for cooking, and high temperature process heat
for industrial purposes.
Solar technologies are broadly characterized as either passive solar or active solar depending on the
way they capture, convert and distribute sunlight. Active solar techniques include the use of
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Prepared by: Manjushree Sthapit
Building Science-II
photovoltaic panels, solar thermal collectors, with electrical or mechanical equipment, to convert
sunlight into useful outputs. Passive solar techniques include orienting a building to the Sun,
selecting materials with favorable thermal mass or light dispersing properties, and designing spaces
that naturally circulate air.
2. Wind Power
Wind power is another ancient renewable energy source which produces no greenhouse gases during
operation, such as carbon dioxide and methane. Wind is a form of solar energy. About 2% of the
solar radiation that falls on the earth is converted to wind energy in the atmosphere. At any given
moment, half of the earth's atmosphere is exposed to the sun, and an equal amount is in shadow. The
cyclical heating and cooling transforms the biosphere into a huge heat engine, generating energy,
some of which is manifested as wind.
Mankind has been making use of wind power for centuries. One of the first known uses was to
propel sailing ships. This was followed, centuries later, by the development of windmills to generate
electricity.Wind can be used to generate electricity, but only if the winds constantly remain over 810 mph.
More than 20,000 wind turbines are used around the world for generating electricity. The optimum
size of wind turbines appears to be around 300 to 500 kilowatts.
3. Geothermal Energy
Geothermal energy is energy obtained by tapping the heat of the earth itself, usually from kilometers
deep into the Earth's crust.So, this energy derives from heat in the Earth's core.
There is also the potential to generate geothermal energy from hot dry rocks. Holes at least 3 km
deep are drilled into the earth. Some of these holes pump water into the earth, while other holes
pump hot water out. The heat resource consists of hot underground radiogenic granite rocks, which
heat up when there is enough sediment between the rock and the earths surface.Steam from hightemperature geothermal fluids can be used to drive turbines and generate electrical power, while
lower temperature fluids provide hot water for space-heating purpose, heat for greenhouses and
industrial uses, and hot or warm springs at resort spas.
4. Biomass Energy
Biomass describes all solid material of animal or vegetable origin from which energy may be
extracted. Plant products (such as corn husks, branches, or peanut shells), waste paper, and cow dung
are examples of biomass fuels. Biomass can be heated, burned, fermented, or treated chemically to
release energy. Solid biomass is mostly commonly used directly as a combustible fuel, producing
10-20 MJ/kg of heat.
Biomass energy, from plants, is a rich source of carbon and hydrogen, and one that can be used
within the natural carbon cycle. Fast-growing plants, such as switch grass and willow and poplar
trees, can be harvested as "power crops." Biomass wastes, including forest residues, lumber and
paper mill waste, crop wastes, garbage, and landfill and sewage gas, can be used to produce heat,
transportation fuels, and electricity, while at the same time reducing environmental burdens.
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Prepared by: Manjushree Sthapit
Building Science-II
5. Energy from wastes
Wastes are generally generated from domestic, commercial and industrial sectors which may be
paper, food wastes, sewage etc. this wastes is seen as a problem which may be solved by land filling.
Land filling may be useful in generation of energy in the form of methane gas.
6. Hydropower
Energy in water can be harnessed and used. Since water is about 800 times denser than air, even a
slow flowing stream of water can yield considerable amounts of energy. Hydroelectric power uses
the force of moving water to produce electricity. Hydropower is one of the main suppliers of
electricity in the world which produces about 20% of the world's electricity, but most often in the
form of large dams that disrupt habitats and displace people.
7. Wave Energy
Wave energy was recognized 800 years ago but work started for this technology was only in mid
17th. Various devices are developed for extracting energy. Several countries including the U.K have
significant potential for using wave energy.
For this energy, cyclone with very forceful air is utilized.
8. Tidal Energy
Tidal Energy is caused by Gravitational and Centrifugal force.The gravitational force results a tidal
buldge in the sea facing the moon whereas the centrifugal force result another tidal buldge on the
opposite side of the earth. Tidal buldges are also caused by the gravitational attraction between the
earth and the sun.
The solar and lunar effects may vary depending upon the relative position of the sun and moon,
causing the variation in height of the tides.
This type of energy can be used to move the turbine (due to flow of tides) for the generation of
electricity.
The largest tidal power station is at La Rance, in Britanny and has capacity of 240MW.
9. Fossil fuel
Fossil fuels were formed over millions and millions of years by the action of heat from the Earth's
core and pressure from rock and soil on the remains (or "fossils") of dead plants and animals.
Different types of fossil fuels were formed depending on what combination of animal and plant
debris was present, how long the material was buried, and what conditions of temperature and
pressure existed when they were decomposing. For example, oil and natural gas were created from
organisms that lived in the water and were buried under ocean or river sediments. Long after the
great prehistoric seas and rivers vanished, heat, pressure and bacteria combined to compress and
"cook" the organic material under layers of silt. In most areas, thick liquid called oil formed first, but
in deeper, hot regions underground, the cooking process continued until natural gas was formed.
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Prepared by: Manjushree Sthapit
Building Science-II
Coal formed from the dead remains of trees, ferns and other plants that lived 300 to 400 million
years ago. In some areas, coal was formed from swamps covered by seawater. The seawater
contained a large amount of sulfur, and as the seas dried up, the sulfur was left behind in the coal.
Some coal deposits, however, were formed from freshwater swamps, which had very little sulfur in
them.

Coal is a rock that burns as it releases energy. It is mostly made of the chemical element
carbon. Some coal is brown and crumbly, and some coal is hard, black, and glossy. It is
energy stored in dead plant matter from prehistoric times. Coal is extracted by heavy
equipment from large mines. Typically coal-bearing rock is extracted from a mine and
crushed and separated. Chunks of coal are then crushed into a fine powder. This powder is
then fed into a combustion unit where it is burned. Heat from the burning coal is used to
generate steam that used to spin one or more turbines which generates electricity. So, coal is
the largest source of fuel for electricity production, and also the largest source of
environmental harm.

Oil is used primarily for transportation fuels, but also for power production, heat and as a
feedstock for chemicals.
Crude oil is extracted from oilfields located on land or offshore in the ocean. Crude oil is
then converted to more refined products in large oil refineries. One product of this refinement
is fuel oil that can be burned in electricity power plants. Typically, oil is burned to heat a
boiler that produces steam. Once steam is produced it spins a turbine that generates
electricity.
Petroleum (oil) is formed from the decay of plants and animals that lived millions of years
ago. This process consumed most of the oxygen, nitrogen, phosphorus, and sulfur and left
behind deposits high in hydrogen and carbon. As the layers of sediment increased, so did the
pressure and temperature, creating fossil fuels. Higher temperatures produced lighter
petroleum, while lower temperatures produced thicker asphalt-type materials. Eventually the
petroleum migrated, or moved out of the source rock and into reservoir rocks where man
could extract the fuel for processing and use.

Natural gas is a relatively clean burning fossil fuel, used mostly for space and water heating
in buildings and running industrial processes. Increasingly, natural gas is used in turbines to
produce electricity.
Natural Gas is made up mostly of methane. Methane, a combination of hydrogen and carbon,
is formed when plants and animals (organic matter) are trapped beneath the sedimentary
layers of the earth. Millions of years ago these organisms died and were buried along with
mud and sand, usually on the floors of lakes, oceans and river beds. The organic matter was
slowly broken down by bacteria.
Typically, natural gas is burned to heat a boiler that produces steam. Once steam is produced
it spins a turbine that generates electricity. In recent years, natural gas-fired combustion
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Prepared by: Manjushree Sthapit
Building Science-II
turbines (CT) have become commonplace. CTs convert natural gas into electricity very
efficiently and produce far less air pollution than other fossil fuel-fired electricity generation
technology. In addition, CTs are relatively small and modular and so can be built quickly and
near to places where new electricity generation is needed to meet demand.
10. Nuclear Energy
The principle of producing electricity by heat is the same in nuclear power production as in coal or
oil based energy production. By heat, the water is boiled to high pressure steam. The steam rotates
the turbine. The generator attached to the turbine generates electricity. In a nuclear power plant the
heat needed for producing electricity is generated in a nuclear reactor by the fission of atomic nuclei.
This energy is "trapped" inside each atom. Atoms can be split apart. Doing so releases tremendous
energy. This process is called nuclear fission. This energy makes heat, which can be used to make
steam and turn the turbines to generate electricity.
The problem with nuclear power plants is the production of radioactive waste material, which must
be taken care of and disposed. However, nuclear power plants are non-polluting sources, unlike
other fossil-fired power plants.
World energy consumption by type
Fig: World energy consumption by type
(Source:http://en.wikipedia.org/wiki/File:World_energy_consumption_by_type_2006.png#filelinks)
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Prepared by: Manjushree Sthapit
Building Science-II
Renewable energy by the end of year 20006
Fig: Renewable energy by the end of year 20006
(Source: http://en.wikipedia.org/wiki/File:Ren2006.png)
A brief history of energy use:
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For half a million years, people have used wood fires to keep themselves warm, to provide light
and to cook their food. Later fires were used to extract and work metals, to fire clay pots and
bricks.
10,000 to 12,000 years ago, since the beginnings of agriculture, animals have been used for
traction (used for pulling heavy loads).
The wind has been used to power ships in the Mediterranean for between 5,000 and 6,000 years.
Mills powered by wind and water were used 2,000 to 3,000 years. Thus natural forces have been
used for many centuries for transport as well as production.
The change in present intensity of fuel use and dependence upon fossil fuels began with the
industrial revolution. At the industrial stage, fuels were seen as cheap and plentiful and the
environmental impacts were also ignored. Since the late 1960’s, there has been a growing
recognition of the environmental impact of industrial revolution, especially by burning of the
fossil fuels.
Due to the oil crisis of 1970’s, there has been a growth in understanding of more efficient use of
energy and also for the introduction of renewable energy sources.
In 1979 to 1980, when the world price of oil has decreased, the pressure to introduce energy
conservation measures has reduced.
At present, the large scale of fossil fuel is a dominant feature.
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Prepared by: Manjushree Sthapit
Building Science-II
Energy use in building:
Like transportation, manufacturing, and agriculture are heavily dependent on expensive fossil fuels,
the world’s buildings also have no exception. The heating, cooling, and lighting of buildings
consume nearly one-quarter of the world’s annual energy supplies, and directly or indirectly from oil
and natural gas.
In the building sector, the prevailing assumption was that efficiency of energy use was unimportant
because technological development would continue to keep fuel prices low. Throughout the 50’s and
60’s, the buildings in many countries were constructed with more energy use. Lighting levels were
increased, a.c systems were added, builders continued to use single pane windows and minimal
insulation. The result was predictable. Energy use in buildings increased more than 5% per year in
many countries.
Residential and commercial energy use in the U.S nearly tripled between 1950 and 1973. Later to
reduce such energy use in buildings, relatively simple changes in design and construction techniques
that could greatly lower the fuel requirements of buildings were introduced. In present context, in
many countries, well designed climate sensitive buildings that use the sun’s energy directly to heat
the interior and provide light and that use natural breezes for cooling are reducing fuel bills by 75%
to 100% depending on local climate. Many are called “Passive Solar” buildings since most heating,
cooling and lighting requirements are supplied by sun light, shading and natural ventilation. Like
that other relies on the conservation techniques of using very heavy insulation and is known as “Low
Energy” buildings.
Most of the energy used in buildings is focused on:
 construction phase
 daily use
 demolition phase
Though there is use of energy in construction and demolition phase, the greatest energy use
buildings over its life time is in daily use, especially for comfort.
In India, for construction phase, materials like cement, brick, iron and steel used up to 26% of coal
for their manufacture and rest of the energy used are electricity and oil.
EXAMPLES
 Residential buildings energy consumption in average
 Energy use in office buildings
 Energy use in commercial buildings
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Prepared by: Manjushree Sthapit
Building Science-II
ENERGY USE IN COMMERCIAL BUILDINGS
Commercial buildings include a wide variety of building types—offices, hospitals, schools, police
stations, places of worship, warehouses, hotels, barber shops, libraries, shopping malls—and that’s
just the beginning of the list. These different commercial activities all have unique energy needs but,
as a whole, commercial buildings use more than half their energy for heating and lighting.
TYPES OF ENERGY USED IN COMMERCIAL BUILDINGS
Electricity and natural gas are the most common energy sources used in commercial buildings.
Commercial buildings also use another source that you don’t usually find used in residential
buildings—district energy. When there are many buildings close together, like on a college campus
or in a big city, it is sometimes more efficient to have a central heating and cooling plant that
distributes steam, hot water, or chilled water to all of the different buildings. A district system can
reduce equipment and maintenance costs, as well as save energy.
ENERGY USE BY TYPE OF BUILDING
Retail and service buildings use the most total energy of all the commercial building types. This isn’t
too surprising when you think of all the stores and service businesses in most towns. Offices use a
large share of energy, too. Education buildings, like your school, use 13 percent of all total energy,
which is even more than all hospitals and other medical buildings combined! Lodging buildings (like
hotels or dormitories) use 8 percent of all energy. Warehouses and food service (like restaurants)
each use 7 percent. Public assembly buildings, which can be anything from libraries to sports arenas,
use 6 percent; food sales buildings (like grocery stores and convenience stores) use 4 percent. All
other types of buildings, like places of worship, fire stations, police stations, and laboratories,
account for the remaining 10 percent of commercial building energy.
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Prepared by: Manjushree Sthapit
Building Science-II
(Source:http://www.eia.doe.gov/kids/energyfacts/uses/commercial.html#BUILDING
S)
References:
1.
http://www.eia.doe.gov/kids/energyfa
cts/index.html
2. http://en.wikipedia.org/wiki/File:World_energy_consumption_by_type_2006.png#filelinks
3. http://en.wikipedia.org/wiki/File:Ren2006.png
4. http://www.daylighting.org/pubs/Building_Energy_V1_TWG.swf
5. http://www.eia.doe.gov/kids/energyfacts/uses/commercial.html#BUILDINGS
6. Godfrey, B.1996, “Renewable Energy: Power for Sustainable Future”, Oxford University in
association with Open University, UK.
7. Treese, D.1982,”Solar Energy and Architecture”, M.Arch.Dissertation, Department of
Architecture and Planning University of Roorkee
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Building Science-II
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