Energy and its Sources: • Energy is the Ability To Do Work • It comes in different forms -- heat (thermal), light (radiant), mechanical, electrical, chemical, and nuclear energy. • sources of Energy: • Renewable (an energy source that can be replenished in a short period of time) • Renewable energy sources include solar energy, which comes from the sun and can be turned into electricity and heat. Wind, geothermal energy from inside the earth, biomass from plants, and hydropower and ocean energy from water are also renewable energy sources. • Non renewable (an energy source that we are using up and cannot recreate in a short period of time). Fossil fuels including Oil, Coal an Natural gas
Renewable Form of Energy • Solar • There are two main ways of using solar energy to produce electricity. • Use of solar cells and • Solar thermal technology. • Solar cells are photovoltaic cells that turn light into electricity. • They are used in small electrical items, like calculators, • Remote area power supplies, like telephones and space satellites. • They are also used on a larger scale to supply electricity through energy authorities. • Solar cells are used to a limited extent in the development of solar-powered vehicles. • Solar thermal technology uses heat gained directly from sunlight. • The best known use of this technology is in solar water heating. • Solar thermal electric generating plants use reflectors to collect heat energy to make steam which drives a turbine that produces electricity.
Energy efficient house; wind power on roof. Solar panels for heat and electricity.
Solar water heating solar air heating
Solar house economics • Add $16,000 to price of house • Pay back - $1500 per year in energy costs • 15 years to break even
Geothermal Heat near surface of the earth = geysers, volcanoes, hot springs
Use heat to make steam to turn turbine for electrical generation Note: deep hot waters are corrosive to best to inject clean water in a closed system and bring it back to the surface as steam.
Although hot areas near surface are limited, the earth is hot everywhere if you go down far enough.
Biomass • All plant and animal matter is called biomass. It is the mass of biological matter on earth. We can get (biomass) energy: • Directly from plants, for example burning wood for cooking and heating. • Indirectly from plants, for example turning it into a liquid (alcohol such as ethanol) or gas (biogas) fuel. • Indirectly from animal waste, for example biogas (mainly methane gas) from sewage and manure.
Hydroelectricity • Hydroelectricity is produced from falling water. The movement of the water spins turbines which generate electricity. • Places with high rainfall and steep mountains are ideal for hydroelectricity. Kohistan, Gilgit, Swat and Dir valleys. • Most hydroelectricity projects require the building of large dams on rivers, which can be very expensive. When large dams are built the flow of the dammed river is changed radically and large areas of land are flooded, including wildlife habitats and farming land. • Run-of-river hydroelectric schemes cause less environmental damage. Large dams do not need to be built, as the run-of-river schemes divert only part of the river through a turbine.
Hydropower Not much used in world, why??
Problems with hydroelectric • Location = unused rivers are in extreme north or low population areas • Competition with recreational uses and environmental concerns. • Hard to build dams in populated river valleys • Siltation of dams – limited life. • Geo-Political issues. • High capital cost.
Wind • Wind power refers to useful energy extracted from wind. An estimated 1 to 3 % of the energy from the Sun that hits the earth is converted into wind energy. • Eventually, the wind energy is converted through friction into diffuse heat all through the earth's surface and atmosphere. • The power in the wind can be extracted by having it act on moving wings that exert torque on a rotor. • The amount of power transferred depends on the wind speed (cubed), the swept area (linearly), and the density of the air (linearly).
Impacts of Use of Non Renewable Energy on Environment: • Coal • Coal is a fossil fuel formed over millions of years from decomposing plants. • Coal is mainly burned in power stations to make electricity and as a source of heat for industry. • Most of the electricity generated in the world comes from burning coal. • When coal is burned it produces large amounts of carbon dioxide, one of the gases responsible for the enhanced greenhouse effect (the increase in the world's temperature due to the increased insulating effect of the earth's atmosphere).
Petroleum • Petroleum, or crude oil, is formed in a similar way to coal. • But instead of becoming a rock, it became a liquid trapped between layers of rocks. • It can be made into gas, petrol, kerosene, diesel fuel, oils and bitumen. • These products are used in houses for heating and cooking and in factories as a source of heat energy. • They are also used in power stations and to provide fuel for transport. • However their use, especially petrol and diesel, produces large amounts of carbon dioxide emissions. • It also produces other poisonous gases that may harm the environment and people's health. Another common use for petroleum is in producing petrochemicals such as plastics.
Gas • Gas is made in the same way as petroleum and is also trapped between layers of rock. • Natural gas is tapped, compressed and piped into homes to be used in stoves and hot water systems. • LPG (Liquefied Petroleum Gas) is made from crude oil. It is used for cooking and heating in homes, industrial heating in boilers, kilns and furnaces, and for camping and caravanning appliances. • LPG can also be used as an alternative to petrol as an engine and transport fuel. Using LPG reduces greenhouse gas emissions from a vehicle by up to 20 per cent.
Nuclear Energy • Nuclear energy is the energy released when atoms are either split or joined together. • A mineral called uranium is needed for this process. Heat energy and steam produced can drive an electricity generator in a power station, or provide direct mechanical power in a ship or submarine. • At each stage of the process various types of radioactive waste are produced. This waste is poisonous and can cause harm to people and the environment coming into contact with it.
Impact of uses of Non Renewable Energy: • Green House Effect: • Greenhouses are used to provide warm places for fruit, vegetables and flowers to grow • Human activities are changing the greenhouse effect. • Using coal-fired power plants releases large amounts of carbon dioxide into the atmosphere. • Driving cars that run on petrol also puts more carbon dioxide into the air. Keeping large numbers of livestock, such as cattle, can also be harmful because they release lots of extra methane gas into the atmosphere. • All these extra greenhouse gases result in more heat being trapped around the earth. We call this process the enhanced greenhouse effect. • These greenhouse gases stop some of the heat from escaping back out into space, making it warm enough for plants, animals and humans to live on earth.
GLOBAL WARMING • Some scientists believe an enhanced greenhouse effect has been created by large increases of greenhouse gases in the atmosphere. • This increase may have been caused by human activities, especially the burning of fossil fuels. • Every year billions of tones of greenhouse gases are released into the air. • These include carbon dioxide (CO2), and methane (CH4). Besides gases that may cause global warming, other hazardous pollutants created by human activity include sulpur dioxide (SOx), nitrogen dioxide (NOx) and particulates. • However the natural rhythm of the water cycle may be being disturbed by global warming because: • It has increased the amount of water vapour in the atmosphere. • It has increased the extent of cloud formation. • It has produced higher rainfall in many areas.
Climate Change: • Changing climatic patterns that are caused by global warming include: • Some areas receiving much higher rainfall than at present, resulting in greater flooding. • Other areas receiving much less rainfall than at present, resulting in drought. • Changes in the distribution of plants and animals around the world, with changing habitats. • Changes to patterns of agriculture around the world. • More severe storms. • More violent cyclones resulting from increasing sea surface temperatures. • The increasing of sea levels, due to thermal expansion of the oceans. This could result in the flooding of low-lying coastal areas. • The melting of glaciers and polar icecaps.
Wise energy uses. • We must understand ecological processes and the interconnections in nature. • We must ‘think globally but act locally’ as responsible energy users. • We need to take the long-term view and think about the consequences of what we do. • We must look for alternative ways to meet human needs: sustainable ways. • We must not forget the connections between the environmental, social and economic factors involved in development. • Making a difference through... • Cutting down use of electricity from coal-fired power stations • Being more energy-efficient with electricity you do use • Using more energy-efficient appliances • Using or increasing your use of renewable sources of energy
Energy Conservation in buildings • Energy Conservation • After construction, a building requires a constant flow of energy input during its operation. • The environmental impacts of energy consumption by buildings occur primarily away from the building site, through mining or harvesting energy sources and generating power. • The energy consumed by a building in the process of heating, cooling, lighting, and equipment operation cannot be recovered. • The type, location, and magnitude of environmental impacts of energy consumptions in buildings differ depending on the type of energy delivered.
Energy Conservation in built Environment • Energy-Conscious Urban Planning • Cities and neighborhoods that are energy-conscious are not planned around the automobile, but around public transportation and pedestrian walkways. These cities have zoning laws favorable to mixed-use developments, allowing people to live near their workplaces. • Urban sprawl is avoided by encouraging redevelopment of existing sites and the adaptive reuse of old buildings. • Climatic conditions determine orientation and clustering. • For example, a very cold or very hot and dry climate might require buildings sharing walls to reduce exposed surface area; a hot, humid climate would require widely spaced structures to
Passive Heating and Cooling • Insulation • Alternate Sources of Energy • Day lighting • Energy-Efficient Equipment & Appliances • Choose Materials with Low Embodied Energy
Wind energy problems • Location – near population center • Bird migration – • Visual • Must be coupled with other sources of electricity. (intermittent supply)
Natural Ventilation • Taking advantage of natural wind currents and convection to cool spaces are very effective ways of reducing the cooling load. • Operable windows, fans and corridors are some of the design strategies that help to direct air flow using natural ventilation principles.
Principles of Natural Ventilation • Natural Ventilation systems rely on natural driving forces, such as wind and temperature difference between a building and its environment, to drive the flow of fresh air through a building. Both work on the principle of air moving from a high pressure to a low pressure zone. • Natural ventilation can be an appropriate choice when compared to air conditioning in the temperate climate particularly as the nights are cool and this can be used to pre-cool the building. • There are two fundamental approaches to designing for natural ventilation that will be effective in most situations: • Cross ventilation which uses air-pressure differentials caused by wind. • Stack ventilation which uses the increased buoyancy of air as it warms up
Benefits of Natural ventilation • The main savings are due to cooling energy reduction (roughly equivalent to an economy cycle), not needing to run HVAC fans and increased occupant satisfaction. • 25 – 33% reduction of energy use in a naturally ventilated mixed mode building with high occupant comfort satisfaction . • International studies in similar climatic regions using natural ventilation only (not mixed mode), show capital costs savings in the region of 10 – 15% and energy costs that are 40% lower than air-conditioned equivalents. • Increased fresh air supply to a space may result in higher thermal comfort levels and increased productivity. • Natural ventilation systems may have an increased robustness, flexibility and adaptability.
Cross ventilation • Cross ventilation depends on two continuously changing factors: wind availability and wind direction. Consequently, it is a somewhat unreliable source for providing air flow and thermal comfort. • In cross ventilation the wind creates a high pressure zone where it impacts the building and a low pressure zone on the leeward side, drawing air through the building See Figure 1 .
Pressure is highest near the centre of the windward wall diminishing to the edges as the wind findsother ways to move around the building so airintakes are preferable near the centre or the highpressure zones. • The flow through a building is related to the size of the openings (both inlets and outlets), restrictions along the flow path, furnishings and the distance between openings. • Basic principles for sizing and placing openings are: • The area of the opening at intake must be equal to or 25% smaller than the area of opening for exhaust. • Air flow will take the line of least resistance so follow the flow line to check for dead spots (areas where fresh air does not go). • Consider security, privacy and noise transfer.
Design issues to consider • Using cross ventilation will have a strong influence on building aesthetics and site planning. • To maximize the effectiveness of openings, narrow buildings with open plans and well placed openings work best (particularly if the longest faces of the building are perpendicular to the typical wind direction). • Furthermore, single-loaded corridors (rooms only on one side of a corridor) will provide better airflow than double-loaded ones as it makes it easier to provide openings on opposite walls. • Building elements like fins, wing walls, parapets and balconies may be designed to enhance wind speeds and should be an integral part of cross-ventilation design though caution needs to be taken that they do not cause turbulence and block air flow . • Below are some considerations that should be made when designing for cross ventilation. • Will work well if the room is up to 5 times the width of the ceiling height.
If cross ventilation is not possible placing windows on adjacent walls, at 90 degrees to each other, will work but limit room size to 4.5 m x 4.5 m. • In a standard office, partitions should not be higher than 1200mm, but this will depend on opening sizes. • Partitions should not obstruct air path. Design spaces so that they are parallel to main ventilation path.
Integration with windows: • The apertures for cross ventilation can also serve as windows for views and day lighting. • All architectural elements intended to enhance one strategy should also work for the other. • However, an orientation that works for ventilation (the windward side) may not be ideal for day lighting for which north-and south-facing are best. • Priorities the needs of the space based on function and climate
Recommendations for openings. • Openings should not be obstructed. • Openings should be staggered and the maximum vertical distance apart possible to increase pressure differences – this will depend on ceiling height but research shows 1.5 m or more is best. • Openings should be fully operable by occupants if a manual operational strategy is chosen. This requires easy access to opening mechanisms as well as training and appropriate information to work well. • Provide inlet openings on the windward side (pressure zone) and outlets on the leeward side (suction zone). • The inlet location affects airflow patterns far more significantly than outlet location. • Inlet location should be a higher priority (if faced with a choice) as a high inlet will direct air toward the ceiling and may bypass the occupied level.
Ensure windows have effective seals to avoid unwanted infiltration. • Orient the building and openings to maximize exposure to prevailing winds. • Consider designing cross-ventilation openings that are secure enough to be left open at night, so that natural ventilation can provide additional night time cooling benefits. • Concentrate ventilation openings in spaces most likely to require cooling. • Minimize solar gain use shading devices like overhangs, awnings and fins to control solar gain. • Only the clear opening area of a window can be used to calculate capacity.
Shading devices should be sized using the above graphic method. To aid in natural ventilation, during summer use high ceiling vaults, and thermal chimneys to promote rapid air changes. By using under grade air chambers, significant sensible cooling can be obtained.
Solar Heating an Cooling. • Passive Solar Heating presents the most cost effective means of providing heat to buildings. Generally, the amount of solar energy that falls on the roof of a house is more than the total energy consumed within the house. • In passive building designs the system is integrated into the building elements and materials - the windows, walls, floors, and roof are used as the heat collecting, storing, releasing, and distributing system. These very same elements are also a major element in passive cooling design but in a very different manner.
The walls and floor are used for solar collection and thermal storage by intercepting radiation directly, and/or by absorbing reflected or reradiated energy. DIRECT SLOAR GAIN Direct gain interior - A direct gain design with an interior water wall for heat storage. Heat stored in the water wall is radiated into the living space at night. Diffusing glazing materials. Translucent glazing scatters sunlight to all storage surfaces. Direct gain design - A direct gain design collects and stores heat during the day. At night stored heat is radiated into the living spaces.
Indirect Heating • This passive solar design approach uses the basic elements of collection and storage of heat in combination with the convection process. In this approach, thermal storage materials are placed between the interior habitable space and the sun so there is no direct heating. Instead a dark colored thermal storage wall is placed just behind a south facing glazing (windows). indirect gain Trombe wall stores heat during the day. Excess heat is vented to the interior space. At night Trombe wall vents are closed and the storage wall radiates heat into the interior space.