Thursday, May 7, 2009
The use of renewable energy sources to replace coal, oil and natural gas is one of the primary methods for achieving a more sustainable future. Renewable energy sources include biofuels, solar energy, wind energy, and geothermal energy. Below is a discussion of each of these sources as community or regional energy sources. The use of these renewable energy sources on individual buildings is later in this blog under the section dealing with sustainable building design.
Monday, May 4, 2009
Biofuels refers to renewable plant matter that is used as a replacement for coal, oil or natural gas to produce energy. This can either be through direct combustion or through the conversion of the plant matter to synthetic fuels such as biodiesel. Biofuels become even more efficient when the plant is harvested for food and only the waste materials from the plant is converted to energy.
Geothermal energy production is a renewable energy source that extracts the heat from the earth's interior. The cost of geothermal energy production is greatly dependent upon how close to the earth's surface are located geothermal vents. In locations such as Iceland and Hawaii where there exists active volcanic activity, geothermal energy is an attractive source of renewable energy. Pictured above is a geothermal power plant built in Iceland.
Solar power, or energy from the sun, is by the earth's most abundant renewable energy source. Unfortunately, while having great potential, last year solar energy production accounted for only 0.02 percent of the world's energy consumption. With concern about global warming, however, governments are providing financial incentives for solar energy production, which helps to create demand and bring down the cost of solar energy technologies. Also, new approaches for solar energy production are being developed, such as that illustrated above where solar rays are concentrated in a single collecting mirror that allows for the building of large solar energy power plants. Examples of such solar energy power plants include the 46 MW Moura solar power plant in Portugal, the 40 MW Waldpolenz solar power plant in Germany, and the 11 MW PS10 solar power plant (illustrated above) in Seville, Spain.
Wind energy is another form of renewable energy. Modern wind turbines have become very efficient at transferring the energy of the wind to electricity. To demonstrate the potential of wind energy, electrical generation from wind turbines grew by 28.8 percent world-wide last year. Two innovative new uses of wind energy are: (1) specially designed new wind turbines that can be mounted on the roofs of urban buildings; and (2) the idea of creating a smart grid where wind energy can be exported from areas of high winds to urban areas needing the energy. Another innovative proposal is to build a grid of wind turbines in the upper midwest of the U.S. to provide cheap energy to extract natural gas from lands containing oil shale.
The heating, cooling and lighting of our buildings accounts for 48 percent of all U.S. energy consumption. As such, building energy usage is the greatest contributor to green house gases and global warming. This will only increase as the world becomes more urbanized and the built environment represents a greater and greater portion of our environment. Stormwater runoff from buildings is also one of the greatest non-point sources of water pollution, while the manufacturer of synthetic materials used in the construction of buildings leads to hazardous waste and an increasing number of "sick" buildings. Following is a discussion of methods of constructing "green" buildings so as to promote a more sustainable environment.
Green roofs are one of the most visible ways to build more sustainable, "green" buildings. A study conducted for Toronto, Canada estimated that the installation of green roofs on buildings could: reduce the heat island effect of urban areas by 1 to 2 degrees C, reduce smog alerts in cities by 5 to 10 percent, absorb CO2 emissions from automobiles and thus reduce green house gases, reduce the energy needs of buildings for heating and air conditioning, filter storm run-off and thus reduce water pollution, and expand recreational and open space in urban areas by creating roof-top gardens.
Solar photovoltaic panels are used to convert the sun's energy into electricity. A converter is used to convert the electricity from DC to AC electricity. Any excess electricity can be stored in batteries or exported to the electrical grid and sold to the local electrical utility.
Passive solar is any means to use the heat from the sun to provide for the heating or energy needs of a building without any means of mechanical assistance. The easiest method of passive solar involves the proper siting of a building to take advantage of the sun when it is at a low horizon or angle, but to provide shading when the sun is at its highest during the hottest part of the day. Another means of passive solar design is to build the floor of a building with some type of thermal mass such as concrete that absorbs the heat - and releases the heat at night when it is cooler.
Previously, wind turbines as an energy source were typically not located on building or within urban areas. With the concern about green energy and global warming, however, new technologies have recently been developed to allow wind turbines to be built on top of buildings -- and be able to deal with the shifting wind directions typical of urban areas. As such, wind turbines are increasingly a part of sustainable green buildings.
Traditional fiberglass insulation is harmful to the environment both in its manufacturer and in its use. A more eco-friendly type of insulation is recycled cellulose insulation. The cellulose can come from such diverse sources as recycled newspapers or recycled blue jeans.
Geothermal heating and cooling involves the use of ground source heat pumps to take advantage of the fairly constant ground temperature to reduce the cost of normal heat pumps to provide for heating and cooling. Wells are dug to a depth of typically 200 feet to obtain a source of air that is approximately 55 degrees year around. This reduces the need for cooling the outside air for air conditioning in the summer and for heating the outside air in the winter, and thus provides for a more efficient form of heating and air conditioning of buildings.
Another method of sustainable green building design is to incorporate means of natural ventilation and lighting into a building, and thus reduce the need for energy use. Innovative new methods of accomplishing this are solar tubes mounted on the roof of buildings that bring concentrated sunlight into buildings and often replace the need for daylight lighting within the building. Also, buildings are increasingly being built with vents on the roof that can be opened to suck the hot air out of buildings and with windows that open that can draw fresh air into buildings.
One example of a proposed sustainable "green" building is the Ecolaboratory building to be built on the 7,200 square foot P-patch in the Belltown neighborhood of downtown Seattle. Conceived by Weber Thompson, it is proposed that the main living units of the building be constructed of recycled shipping containers. All water, including black and gray water, is to be recycled for the use of residents and landscaping water needs. Residents will be able to individually control the amount of their natural ventilation by the design of what are referred to as "earth tubes." Solar hot waters panels will provide for the heating of hot water. Also providing energy for the building will be photovoltaic solar panels, biomass conversion, and even hydrogen fuel cells - to generate electricity.
To demonstrate how a sustainable home can be constructed, Duke University in conjunction with Home Depot has built a sustainable "smart home" demonstration. It has received a LEED (Leadership in Energy and Environmental Design) platinum rating, the highest level rating. It includes solar water panels for hot water heating, 18 photovoltaic solar panels that generate 3 kW of electricity, a vegetated green roof planted with sedums that are drought tolerant and capture and filter rainwater while providing roof insulation, rainwater collection for irrigation of the grass of the site, Energy Star appliances, and recycling of construction waste materials.
An example of a sustainable green building that takes advantage of natural ventilation is the Environmental Nature Center in Orange County, California.
Sunday, May 3, 2009
The proposed Independence Station building claims that, when constructed, it will be the highest rated Platinum LEED (Leadership in Energy and Environmental Design) building in the world. It will include almost all of the various approaches to green building design (green roof, photovoltaic solar panels to generate electricity, passive solar hot water heating, geothermal heating and cooling, rainwater harvesting, etc.)
The Clinton Presidential Library in Little Rock, Arkansas is the first presidential library to be designed green. When it opened, it received a silver LEED (Leadership in Energy and Environmental Design) award, but has since been upgraded to the highest award level -- i.e. a platinum award. It has a green roof with approximately 90 different types of plants, solar panels, and includes a wetlands next to it that is protected as part of the library.
One of the best examples of a building design with a green roof is the "living roof" of the newly constructed California Academy of Science in San Francisco.
The BedZED Eco-Village located in Wallington, South London, England is intended to be a zero-energy, carbon neutral community development. Opened since 2002, it is designed to house 100 families, community facilities, and office space for 100 workers. Developed by Peabody Trust in conjunction with Bioregional Development Corporation and designed by architect Bill Dunster, its homes are designed to use only 10 percent of the energy of a typical home.
The Brighton Earthship is an experimental sustainable building near Stamner Park, Brighton, East Sussex, England. Its walls are made from recycled tires and it is built semi-underground to use the insulation properties of the earth itself. It includes a windmill and passive and active solar heating, as well as geothermal heating and cooling.