INSIGHTCORE ® -
College of Architecture and Planning, University of Colorado at Denver, United States
Energy generation is directly related to human needs, and energy consumption can be correlated with a society's economic growth and development (Chevalier, 2007). Today, the amount of energy needed is greater than ever. Unfortunately, more than 80% of our energy generation today is through fossil-
Keywords: buildings, green technology, energy generation
Technology is defined as a practical application of (technical) knowledge, which requires the use of tools and crafts to control and adapt our environment. The term originates from the Greek "techne" (craft) and "logia" (saying); however, its current use is inherently broad and elusive. It can refer to material objects (such as machines) or to broader knowledge areas (such as systems and methods). Today, most dictionaries define technology as an "applied science," assuming the two terms have a causal relationship. Although these terms often seem to overlap (especially since the Industrial Revolution), there is actually a clear distinction between them and in how they have progressed throughout history (McClellan and Dorn, 2006).
Practical knowledge is a key component within technology. Although knowledge is a prerequisite for developing technologies, it is not necessary for that knowledge to be either scientific or systematic. In fact, there is a clear distinction between the terms "knowledge," "science," and "technology." "Knowledge" is a state or fact of knowing. The American Heritage Dictionary defines the term as "familiarity, awareness, or understanding gained through experience or study." (4th Edition, 2004). As stated earlier, 'technology' is the use of that knowledge to solve practical problems. Like technology, "science" also uses knowledge but in a systematic manner. Accordingly, "science" is defined as the systematic knowledge of the physical or material world gained through observation and experimentation. In short, science is an organized knowledge, and technology is a practical application of that knowledge (Spencer, 1897; Francis, 2007).
The history of architectural technology follows more or less the same path as the overall history of technology, but with additional elements. Knowledge, technology, and science are incorporated with art and materials to define 'architectural technology.' However, as in other fields, these terms have different meanings when applied to architecture. Parallel to the original definition of 'technology,' this paper defines 'green technology' as: (a) sustainable, ecological, and performative methods and tools; (b) an efficient means to an end; and/or (c) as an ensemble of green buildings. But green technology also needs green architectural practices, like the creation, fabrication and the use of green concepts. This includes non-
2. Energy Generation
In brief, energy generation depends on resources capable of producing energy, and related extraction methods necessary to utilize these resources. Energy generation is directly related to human needs, and energy consumption can be correlated with a society's economic growth and development (Chevalier, 2007). Today, the amount of energy needed is greater than ever. Unfortunately, more than 80% of our energy generation today is through fossil-
Therefore, it is daily becoming more critical to develop new energy generation resources, technologies, and methods. Interest in generating green energy, because of its sustainable and ecological nature, has increased dramatically within the last couple of years. Mandates for energy sustainability (recommended by federal and state governments) have particularly facilitated this increase. Although currently these mandates are voluntary, twenty-
The following energy resources do not depend on fossil-
3. Bio Energy
Figure 1. Bio Energy Cycle
Throughout history, biomass had been the primary fuel source for all civilizations. But as the Industrial Revolution progressed, especially in Europe, forests were severely depleted and coal was gradually introduced as a replacement fuel. In the United States, biomass was a primary source of energy up until the 19th century. However, by 1885 its use was being outpaced by coal, and by 1915, by oil and gas (Hottel & Howard, 1971; Tester, Drake, Golay, Driscoll, & Peters, 2005). Today, many developing countries still use biomass for 90% of their energy source, especially for daily activities such as heating and cooking. Although biomass is an excellent green energy source, the current method of collection, production, and processing creates harmful effects. Primitive processing techniques and inadequate devices for energy conversion waste most of the biomass and create unhealthy living environments for people (e.g., massive indoor pollution). In addition, uncontrolled overpopulation places an overwhelming demand on indigenous biomass, causing land depletion and even desertification, as seen in some parts of Africa today (Hottel & Howard, 1971).
There are primarily two types of bio-
4.1 Solid Bio-
o Wood pellets
o Bagasse (fibers left after sugarcane or sorghum stalks are crushed in juice extraction)
o Construction waste
o Municipal byproducts
Figure 2. Wood pellets made from compacted sawdust have high combustion efficiency and are used as bio-
4.2 Liquid Bio-
o Made from sugar and starches
o Made from plant oils and animal fats
4.3 Gas Bio-
" Synthetic Natural Gas (SNG)
Advantages of Bio-
" Directly extracted from biomass
" Renewability and domestic availability
" Evenly distributed energy source
" Biomass utilization diverts landfill accumulation
" Potential to prevent CO2 buildup in the atmosphere
Disadvantages of Bio-
" Low energy density (compared to coal, liquid petroleum, or other petroleum-
" May contribute to environmental pollution
" Contributes to the depletion of Earth's resources (land, water, plants, forest, food)
" High embodied energy (transportation costs do not justify the energy savings)
5. Biomass Conversion Processes
To generate clean bio-
Although this process does not produce bio-
This process uses micro-
This process is used for direct power generation. It is one of the most efficient conversion technologies today with 30% efficiency in electricity generation and more than 75% in cogeneration of electricity and heat. For more information about the combustion process, see "The Handbook of Biomass Combustion and Co-
6. Solar Energy
The second type of green energy generation is solar energy. Solar energy is gained directly from the sun, our most abundant source of energy. The sun emits radiation during the fusion process, which produces various wavelengths of electromagnetic radiation. The earth captures only a small fraction of that energy from the interstellar void (Kambezidis & Gueymard, 2004; Vita-
Figure 3. Solar Radiation Distribution. The earth and the atmosphere absorb approximately 70% of the solar radiation. 30% of the incoming radiation is reflected.
Consequently, the amount of solar energy the earth receives in a year is approximately 3.1 million exajoules (EJ) (Houghton et al., 2001). According to the 2008 International Energy Outlook Report, our global energy consumption is 462 EJ/year (2005) and is expected to double by the year 2030 (DOE, 2008). The vast discrepancy between these production and consumption statistics clearly show that the earth receives approximately 6,900 times more energy from the sun than we consume globally. If harvested correctly, even a small fraction of the sun's tremendous energy output could provide more than we need.
Existing solar technologies convert solar energy into other forms of energy, namely electricity and heat. Although there are numerous ways to convert solar energy into usable energy (Sark, Patel, Faaij, & Hoogwijk, 2006), three primary conversion technologies are used: (1) Greenhouse, (2) Solar Thermal, and (3) Solar Electricity.
The passive Greenhouse technology is the oldest and simplest way to harvest solar energy, wherein the heat of the sun penetrates a special window system and is trapped inside. This system has been primarily used to provide adequate temperature control for plants in cold weather and climates (Hanan, 1997; Marshall, 2006; McCullagh, 1978).
6.2 Solar Thermal
Solar Thermal technology uses the same principle as the greenhouse technique (i.e., using sunlight to create heat) but is more advanced and needs water to operate. It was originally developed to pump water in the nineteenth century. Once solar-
Figure 4. Parabolic trough collectors
Figure 5. Dish power plant
Figure 6. Power tower plant
The parabolic trough is the most established low-
7. Solar Electric (Photovoltaic)
Of the solar electric systems currently available, photovoltaic (PV) technology is the most advanced and mature. The material used in this technology will be covered in the next chapter, but briefly, PV technologies are non-
A photovoltaic system consists of: PV cells, mounting hardware, electrical connections, power conditioning equipment, and an energy storage device. Individual PV cells, which can be as small as a dime, can generate between 0.5 to 1.2 volts of electricity. Individual cells can be grouped into modules to form larger collectors, which can in turn be further grouped into PV arrays, necessary for industrial-
Figure 7. Photovoltaic systems
A majority of PV cells are made of silicon, and there are three main PV technologies used commercially in the market today: (1) Single Crystalline, (2) Polycrystalline, and (3) Thin Film.
7.1 Single Crystalline PV-
Single Crystalline is a first-
7.2 Polycrystalline PV-
Polycrystalline cells are made of silicon that is cast into cylinders, and then sliced into wafers. Since this process is less precise than SCPV fabrication, it has lower manufacturing costs. PCPV's conversion efficiency is slightly lower (10-
7.3 Thin Film
Thin film is a low-
Advantages of Solar-
" Free energy with unlimited supplies
" Environmentally safe (produces no pollution)
Disadvantages of Solar-
" High initial cost
" Inconsistent delivery of energy (the amount of sunlight is not constant, depending on location, time, and weather conditions)
" Large surface area installation is required to produce sufficient energy
" Indirect high embodied energy (production of solar energy technologies)
8. Geothermal Energy
A third method of 'green' generation of energy is geothermal. Geothermal energy is produced by using the heat below the earth's surface. This heat originates from the earth's core 4,000 miles below the surface, where temperatures can reach up to 9,000° F. Although most geothermal basins are deeply rooted underground and are, therefore, unseen, they occasionally burst forth in the form of hot springs, geysers, volcanoes, and fumaroles. In addition to the earth's core, geothermal energy may emerge from other sources, such as from continental plate frictions and the decay of naturally-
There are various ways to extract geothermal energy. The simplest is to drill into geothermal reservoirs in order to bring the heat source (steam or hot water) to the surface. Geothermal heat pumps are necessary for residential use, and, for commercial use, power plants are built on the surface to convert geothermal energy into electricity. There are three main types of power plants: (1) Dry Steam, (2) Flash Steam, and (3) Binary Power.
8.1 Dry Steam Plants (DSP)
DSPs are the most widely used geothermal energy power plant today. They must be located near accessible steam reservoirs, where the steam is tapped and piped directly to the plant in order to power the generator's turbines.
8.2 Flash Steam Plants (FSP)
FSPs convert high pressure hot water into steam, which powers the generator's turbines. Their efficiency is 50% lower than for DSPs because of energy losses during the water to steam conversion (Berinstein, 2001). However, the condensed water can be recycled and reused.
8.3 Binary Power Plants (BPP)
BPPs are complex versions of flash steam plants and are especially useful in that they allow cooler geothermal reservoirs to be tapped. The cooler reservoir water is pumped into a heat exchanger and then back down into the reservoir. Then another liquid with a lower boiling point is rapidly pumped in. The heat is sufficient to vaporize the second liquid, and the steam that is produced powers the turbines. As in FSPs, the second liquid is condensed and reused.
8.4 Geothermal Heat Pumps (GHP)
Geothermal heat pumps are used to heat or cool residences, rather than relying on fossil fuels. They run on the same principle as commercial power plants, utilizing the constant heat source of the earth's interior. The Environmental Protection Agency (EPA) states that a geothermal system can save between 30-
A geothermal heat exchanger system consists of indoor pump equipment, a ground loop, and a flow center to connect the indoor and outdoor equipment. The ground loop uses the temperature of the earth or water, several feet underground, to heat or cool the dwelling. A pump circulates a temperature-
Advantages of Geothermal Energy
" Clean, No polluting emissions
" Regional (contributes to local economy)
" Resource availability
Disadvantages of Geothermal Energy
" Not a renewable resource like sunlight and wind
" Problems with accessibility
" Potential Environmental Damage (e.g., erosion, sedimentation, toxic antifreeze solutions in heat pump systems)
" Residential heat pump systems are expensive
9. Wind Energy
Wind energy is yet a fourth form of green energy, related to solar energy, as wind is generated by solar patterns and their influence on the earth's topography. The planet's rotation, climate, and topography contribute to the speed and direction of the wind that will be harnessed. However, wind energy provides a significantly smaller amount of energy than solar energy. The global theoretical wind energy potential is only 2% of the amount of solar energy that reaches our atmosphere (Hubert, 1971; Sark et al., 2006).
Wind energy turns a windmill's blades on a rotor that is connected to a main shaft. The main shaft spins a generator, producing energy. The amount of energy generated depends on various factors, such as the speed and the direction of the wind. Even though strong winds can produce more energy, it is difficult to design and maintain windmills that can withstand such force. Another problem is proximity of the wind generation facilities to the distribution centers and/or to the homes. The farther the distance, the more distribution lines that need to be extended. This affects the quality and cost of the energy transmission.
There are three types of wind machines used today: (1) Horizontal-
Wind Amplified Rotor Platform (WARP): WARP is a completely different wind machine design, as it does not have blades. Instead, independent modules are stacked on top of each other with small high-
Advantages of Wind Energy
" Clean, No emissions
" Regional (contributes to local economy)
" Resource availability
Disadvantages of Wind Energy
" Problems with accessibility
" Requires land allocation and wind farming
" Potentially dangerous for birds
10. Hydro Energy
Hydro (water) energy, generated from the force of moving water, is a fifth ecologically-
Figure 8. Renewable Energy Added and Existing Capacities, 2008 (estimated). Sources: Renewables: Global Status Report, 2009 Update (REN21, 2009).
Although hydro energy is primarily generated by large installations, there are smaller, mobile hydro-
11. Blue Energy
Yet another source of clean energy is Blue Energy, also called osmotic energy. It is generated from a chemical reaction between fresh water and sea water. Energy is retrieved from a dilution process, designed to balance the salt concentration differences between the two solutions, in a process called 'pressure osmosis' or 'reverse electro dialysis.'
Figure 9. Osmotic pressure difference sea water and fresh water creates Blue Energy
This is a new, promising, renewable clean energy source with no harmful environmental effects. It can either be installed near a salt water resource (i.e., at the mouth of a river) or operated independently using stored water. Although the technology has been developed, there are no commercial applications available today. This is primarily because its complexity requires operational expertise to run, and the costs associated with its installment and use, are high.
12. Fuel Cell Energy
Fuel cell energy is a sixth promising method of generating energy. A fuel cell is a kind of battery that produces electricity from the reaction between an externally supplied fuel and an oxidant, in the presence of an electrolyte. There are different fuel cell combinations, depending on the type of fuel and/or oxidant. For example, a hydrogen fuel cell uses hydrogen as the fuel and oxygen as its oxidant. Other fuels may include (but are not limited to) methane, ethanol, bio-
Fuel cells are manufactured in different sizes and capacities, and can be used for products ranging from small consumer electronics to energy generators for large buildings. For home use, fuel cells are currently being developed by various manufacturers, such as General Electric Fuel Cell Home Power Plant (HomoGen, 7000), Tokyo Gas with Ballard Power Systems and Matsushita Electric (1 kilowatt combined heat and power fuel cell generator), and Astris Energy of Canada with Alternate Energy Corp (4-
Fuel cells provide clean, renewable energy and do not need distribution lines. Small-
Figure 10. Fuel cells provide clean, renewable energy without distribution lines
13. Hydro Systems
The eighth and last source of energy generation with no damaging environmental impact is the hybrid system. This is a method that uses two or more distinct power sources to run a device. Examples could include: an on-
Figure 11. Hybrid power systems
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