Sci, Tech, Env Exam 2
17. What are the Geysers?
The largest geothermal system now in operation is a steam-driven plant in an area called the Geysers, north of San Francisco, California. Despite the name, there are actually no geysers there, and the heat that is used for energy is all steam, not hot water. Although the area was known for its hot springs as far back as the mid-1800s, the first well for power production was not drilled until 1924. Deeper wells were drilled in the 1950s, but real development didn't occur until the 1970s and 1980s. By 1990, 26 power plants had been built, for a capacity of more than 2,000 MW.
26. What are the various types of home geothermal systems?
There are four basic types of ground loop systems. Three of these -- horizontal, vertical, and pond/lake -- are closed-loop systems. The fourth type of system is the open-loop option. Which one of these is best depends on the climate, soil conditions, available land, and local installation costs at the site. All of these approaches can be used for residential and commercial building applications. CLOSED-LOOP SYSTEMS Most closed-loop geothermal heat pumps circulate an antifreeze solution through a closed loop -- usually made of plastic tubing -- that is buried in the ground or submerged in water. A heat exchanger transfers heat between the refrigerant in the heat pump and the antifreeze solution in the closed loop. The loop can be in a horizontal, vertical, or pond/lake configuration. One variant of this approach, called direct exchange, does not use a heat exchanger and instead pumps the refrigerant through copper tubing that is buried in the ground in a horizontal or vertical configuration. Direct exchange systems require a larger compressor and work best in moist soils (sometimes requiring additional irrigation to keep the soil moist), but you should avoid installing in soils corrosive to the copper tubing. Because these systems circulate refrigerant through the ground, local environmental regulations may prohibit their use in some locations. HORIZONTAL This type of installation is generally most cost-effective for residential installations, particularly for new construction where sufficient land is available. It requires trenches at least four feet deep. The most common layouts either use two pipes, one buried at six feet, and the other at four feet, or two pipes placed side-by-side at five feet in the ground in a two-foot wide trench. The Slinky™ method of looping pipe allows more pipe in a shorter trench, which cuts down on installation costs and makes horizontal installation possible in areas it would not be with conventional horizontal applications. Illustration of a horizontal closed loop system shows the tubing leaving the house and entering the ground, then branching into three rows in the ground, with each row consisting of six overlapping vertical loops of tubing. At the end of the rows, the tubes are routed back to the start of the rows and combined into one tube that runs back to the house. VERTICAL Large commercial buildings and schools often use vertical systems because the land area required for horizontal loops would be prohibitive. Vertical loops are also used where the soil is too shallow for trenching, and they minimize the disturbance to existing landscaping. For a vertical system, holes (approximately four inches in diameter) are drilled about 20 feet apart and 100 to 400 feet deep. Into these holes go two pipes that are connected at the bottom with a U-bend to form a loop. The vertical loops are connected with horizontal pipe (i.e., manifold), placed in trenches, and connected to the heat pump in the building. Illustration of a vertical closed loop system shows the tubing leaving a building and entering the ground, then branching off into four rows in the ground. In each row, the tubing stays horizontal except for departing on three deep vertical loops. At the end of the row, the tubing loops back to the start of the row and combines into one tube that runs back to the building. POND/LAKE If the site has an adequate water body, this may be the lowest cost option. A supply line pipe is run underground from the building to the water and coiled into circles at least eight feet under the surface to prevent freezing. The coils should only be placed in a water source that meets minimum volume, depth, and quality criteria. Illustration of a pond or lake closed loop system shows the tubing leaving the house and entering the ground, then extending to a pond or lake. The tubing drops deep into the pond or lake and then loops horizontally in seven large overlapping loops, then returns to the water's edge, extends up near the surface, and returns back to the house.
14. Why is the size of the turbine blade important?
Simply put: Longer wind turbine blade length means greater power production. Blades capture the wind which forces the rotation of the rotor; longer blades means more area for the wind to push against, which means greater force and rotational power.
25. Why must DC be converted to AC in alternative energy systems?
Solar cells produce Direct Current (DC) as they react to the solar energy radiation. Solar energy is stored in batteries which can only store DC power. However, most home appliances are AC powered, as they are designed to work on the AC grid. Most of the off-grid population that uses solar energy doesn't have DC supported devices, hence the need to convert this energy into AC. Bridging this gap is done with DC to AC converters. For instance, Lumos Global, a company that' producing a solar system for off-grid homes, is equipping its system with DC to AC converter which enables users to power their TVs and other AC appliances. To learn more about it visit www.lumos-global.com
15. What are the three primary methods of producing geothermal energy?
dry steam, flash steam, and binary cycle
20. What are the major types of water wheels?
horizontal waterwheel, the undershot vertical waterwheel, and the overshot vertical waterwheel
11. Why is placement of wind turbines important?
When deciding where wind turbines should be placed, there are many concerns including, the best location, the optimal height, environmental concerns, and cost. Even though wind energy is clean, renewable energy resource there are still environmental concerns. Wind turbines have been known to kill birds. Also they make irritating noise when spinning. These problems can be reduced however if a location relatively far from popular areas is chosen. Also wind energy is significantly more expensive than fossil fuels. With time and development in the technology the cost could be reduced.
23. How was the Hoover Dam constructed? What were some of the problems associated with its construction?
4.4 million cubic yards of concrete 88 million pounds of plate steel and outlet pipes 6.7 million pounds of pipe and fittings 45 million pounds of reinforced steel The first difficult step of construction involved blasting the canyon walls to create four diversion tunnels for the water. Facing strict time deadlines, workers toiled in 140-degree tunnels choked with carbon monoxide and dust, conditions that prompted a six-day strike in August 1931. When two of the tunnels were complete, the excavated rock was used to form a temporary coffer dam that successfully rechanneled the river's path in November 1932. The second step of involved the clearing of the walls that would contain the dam. Suspended from heights of up to 800 feet above the canyon floor, high scalers wielded 44-pound jackhammers and metal poles to knock loose material, a treacherous task that resulted in casualties from falling workers, equipment and rocks.
1. What are the three major types of solar hot water systems?
ACTIVE SOLAR WATER HEATING SYSTEMS There are two types of active solar water heating systems: Direct circulation systems Pumps circulate household water through the collectors and into the home. They work well in climates where it rarely freezes. Indirect circulation systems Pumps circulate a non-freezing, heat-transfer fluid through the collectors and a heat exchanger. This heats the water that then flows into the home. They are popular in climates prone to freezing temperatures. PASSIVE SOLAR WATER HEATING SYSTEMS Passive solar water heating systems are typically less expensive than active systems, but they're usually not as efficient. However, passive systems can be more reliable and may last longer. There are two basic types of passive systems: Integral collector-storage passive systems These work best in areas where temperatures rarely fall below freezing. They also work well in households with significant daytime and evening hot-water needs. Thermosyphon systems Water flows through the system when warm water rises as cooler water sinks. The collector must be installed below the storage tank so that warm water will rise into the tank. These systems are reliable, but contractors must pay careful attention to the roof design because of the heavy storage tank. They are usually more expensive than integral collector-storage passive systems.
8. What advantages are associated with wind turbines?
ADVANTAGES OF WIND POWER Wind energy is a clean fuel source. Wind energy doesn't pollute the air like power plants that rely on combustion of fossil fuels, such as coal or natural gas. Wind turbines don't produce atmospheric emissions that increase health problems like asthma or create acid rain or greenhouse gases. According to the Wind Vision Report, wind has the potential to reduce cumulative greenhouse gas emissions by 14%, saving $400 billion in avoided global damage by 2050. Wind power does not use water, unlike conventional electricity sources. Producing nuclear, coal, or gas-fired power uses water for cooling. Water is becoming a scarce resource all over the country. Wind power uses zero water in its energy generation. Wind is a domestic source of energy. The nation's wind supply is abundant. Over the past 10 years, wind capacity increased an average of 31% per year, reaching a cumulative capacity of over 75,000 MW in 2016, enough to power over 20 million homes. Wind power is the largest source of annual new generating capacity, well ahead of the next two leading sources, solar power and natural gas. Wind power is inexhaustible. Wind is actually a form of solar energy. Winds are caused by the heating of the atmosphere by the sun, the rotation of the Earth, and the Earth's surface irregularities. For as long as the sun shines and the wind blows, the energy produced can be harnessed to send power across the grid. Wind power is cost-effective. It is one of the lowest-cost renewable energy technologies available today, with power prices offered by newly built wind farms averaging 2 cents per kilowatt-hour, depending on the wind resource and the particular project's financing. Even without government subsidies, wind power is a low-cost fuel in many areas of the country. Wind turbines can be built on existing farms or ranches. This greatly benefits the economy in rural areas, where most of the best wind sites are found. Farmers and ranchers can continue to work the land because the wind turbines use only a fraction of the acreage. Wind power plant owners make rent payments to the farmer or rancher for the use of the land, providing landowners with additional income. In 2015, annual land lease payments in the United States were estimated to total $222 million. This additional income provides the agricultural community an avenue to diversify revenue and reduce reliance on uncertain commodity prices. According to the Wind Vision Report, annual land lease income for rural American landowners could increase to $1 billion by 2050. Wind creates jobs. In 2016, the wind energy sector invested more than $8.8 billion of private capital in the U.S. economy to build projects and employed more than 101,000 workers (approximately 30% women, 11% veterans, and 25% minorities), according to the 2017 U.S. Energy and Employment Report. More than 8,800 technicians were employed in 2015 to monitor and maintain wind turbines, and this profession is expected to grow by 108% in the next decade, making it the country's fastest-growing occupation (according to the Bureau of Labor Statistics). According to the Wind Vision Report, wind has the potential to support more than 600,000 jobs in manufacturing, installation, maintenance, and supporting services by 2050.
19. What problems are caused by geothermal energy production?
Cons of Geothermal Energy There are some minor environmental issues associated with geothermal power. Geothermal power plants can in extreme cases cause earthquakes. There are heavy upfront costs associated with both geothermal power plants and geothermal heating/cooling systems. Very location specific (most resources are simply not cost-competitive). Geothermal power is only sustainable (renewable) if the reservoirs are properly managed.
7. What disadvantages are associated with photovoltaic systems?
Disadvantages Some toxic chemicals, like cadmium and arsenic, are used in the PV production process. These environmental impacts are minor and can be easily controlled through recycling and proper disposal. Solar energy is somewhat more expensive to produce than conventional sources of energy due in part to the cost of manufacturing PV devices and in part to the conversion efficiencies of the equipment. As the conversion efficiencies continue to increase and the manufacturing costs continue to come down, PV will become increasingly cost competitive with conventional fuels. Solar power is a variable energy source, with energy production dependent on the sun. Solar facilities may produce no power at all some of the time, which could lead to an energy shortage if too much of a region's power comes from solar power.
4. What disadvantages are associated with solar hot water systems?
Disadvantages of Solar Water Heating Solar thermal panels can only heat water. Solar PV panels, however, generate electricity and some of this electricity can also be used to heat water. So there is more flexibility with solar PV. Annual maintenance is recommended. This is because there are a few parts to the system like the pump and antifreeze which need to be checked to ensure that they are performing optimally. Usually a new hot water cylinder will need to be installed so space is required to house this. - The main disadvantage of solar water heating systems is relatively high upfront costs. - In most areas they will require electrical or gas or other fuel backup during the winter period. - Payback times can vary greatly mostly due to regional sun (the more insolation, the shorter payback period). - Relatively low efficiency of passive solar water heating systems. - They require excellent overheating and freeze protection.
18. What advantages does geothermal energy have over other forms of energy production?
Geothermal energy is generally considered environmentally friendly and does not cause significant amounts of pollution. Geothermal reservoirs are naturally replenished and therefore renewable (it is not possible to exhaust the resources). Massive potential - upper estimates show a worldwide potential of 2 terawatts (TW). Excellent for meeting the base load energy demand (as opposed to other renewables such as wind and solar). Great for heating and cooling - even small households can benefit. Harnessing geothermal energy does not involve any fuels, which means less cost fluctuations and stable electricity prices. Small footprint on land - can be built partially underground. Geothermal energy is available everywhere, although only some resources are profitably exploitable. Recent technological advancements (e.g. enhanced geothermal systems) have made more resources exploitable and lowered costs.
3. How are flat panel solar hot water panels constructed?
Glazed flat-plate collectors are insulated, weatherproofed boxes that contain a dark absorber plate under one or more glass or plastic (polymer) covers. Unglazed flat-plate collectors -- typically used for solar pool heating -- have a dark absorber plate, made of metal or polymer, without a cover or enclosure.
16. What parts of the United States are most favorable for geothermal energy production?
In the United States, most geothermal reservoirs of hot water are located in the western states, Alaska, and Hawaii
22. Where was the Niagara power station reviewed in class located?
Lewiston, New York, near Niagara Falls.
12. Which locations best support wind turbine energy in the United States?
North Dakota Texas Kansas South Dakota Montana Nebraska Wyoming Oklahoma Minnesota Iowa
2. How do active and solar passive heating differ?
Passive solar water heating systems are typically less expensive than active systems, but they're usually not as efficient. However, passive systems can be more reliable and may last longer. There are two basic types of passive systems:
6. What materials are used in photovoltaic systems?
Photovoltaic power generation employs solar panels composed of a number of solar cells containing a photovoltaic material. Materials presently used for photovoltaics include monocrystalline silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, and copper indium gallium selenide/sulfide.
5. Why is placement of hot water or photovoltaic systems important?
Away from trees, tall buildings and be in a position to face the sun well. Location is important Improper placement or the use of low-quality sensors can lead to their failure to detect freezing conditions. The controller may not drain the system, and expensive freeze damage may occur.
10. What is the difference between vertical and horizontal axis turbines?
Axis of rotation It is the main and biggest difference they have. As the name say horizontal axis wind turbine have axis of rotation parallel to the ground and vertical axis wind turbine have axis of rotation perpendicular to ground Number of blades working at a time If we take 3 blades wind turbine then in horizontal axis wind turbine all three blades work at a time while in vertical axis wind turbine one blade work at a time. Working wind direction Vertical axis wind turbine work in all wind directions while horizontal axis wind turbine only works in a specific wind direction, when wind direction change horizontal axis wind turbine have to move itself in the direction Efficiency at a given wind speed Because all blades of horizontal axis wind turbine work ata time so its efficiency is much more than the vertical axis wind turbine. Area needed for installation Because of the axis of rotation area need for the horizontal axis wind turbine is much more than needed for vertical axis wind turbine. Height is also a concern for horizontal axis wind turbine but not for vertical axis wind turbine Location of installation Because of area needed and protection precision horizontal axis wind turbine cannot installed near population whereas vertical axis wind turbine is designed for installation in urban areas
24. What are two types of wave energy systems?
Ocean wave energy technologies are still in the early development and demonstration phase. There are four predominant wave energy technologies: point absorbers, attenuators, terminators, and overtopping devices. These four technologies are classified according to their size and orientation. Point absorbers have a small horizontal dimension compared with the vertical dimension. Attenuators are elongated floating structures whose length, which is about one wavelength or longer, is aligned in the direction of the wave propagation. Terminator devices are aligned perpendicular to the direction of wave propagation. Overtopping devices are reservoirs that are filled by incoming waves to levels above the average surrounding ocean.
13. Why is the height of the turbine important?
Standard turbine height is 50 m. Since there's more wind at higher altitudes the wind turbine height ranges from 50 m to about 100 m. But how does height impact the power output? The following equation shows the relationship between tower height and velocity. (V/Vo) = (H/Ho)^a where a is coefficient of friction is the turbine, Ho is the height from the bottom of the turbine to ground, H is the height from the center of the turbine to ground, V is wind speed at H, and Vo is wind speed at Ho. Since P is proportional to v^3 the resulting equation is (H/Ho)^3a=(P/Po). The coefficient of friction increases with rougher terrain and which in turn increase the power significantly. Therefore, higher turbines are ideal. The trade of is the higher turbine is more expensive.
21. What are the disadvantages or advantages of each type?
The horizontal waterwheel is the only one that rotates around a vertical axle (confusing!). The undershot and overshot waterwheels rotate around a horizontal axle, like a car tire, but as you can see, receive their driving force from the water at the bottom and top, respectively. A hybrid of the over- and undershot wheels developed some time in the later Middle Ages or colonial period as well, but it used the basic principles of the other two. This was known as the breastshot wheel that worked somewhat like the undershot wheel, but the water came into contact with the breastshot wheel at mid-height (i.e., as if it were hitting us at breast/chest height), and flows down a closely-fitting housing around the wheel. The wheel therefore partially gets the advantage of the moving water like the undershot and also the weight of the falling water, partially like the overshot.
9. What disadvantages are associated with wind turbines?
Wind power must compete with conventional generation sources on a cost basis. Depending on how energetic a wind site is, the wind farm might not be cost competitive in less windy areas of the country. Even though the cost of wind power has decreased dramatically in the past 10 years, the technology requires a higher initial investment than fossil-fueled generators. Good wind sites are often located in remote locations, far from cities where the electricity is needed. Transmission lines must be built to bring the electricity from the wind farm to the city. According to the American Wind Energy Association, approximately 51,000 MW of new wind capacity could be added if near-term transmission projects in advanced development are completed. The Energy Department released a report which confirms that adding even limited electricity transmission can significantly reduce the costs of expanding wind energy to supply 35% of U.S. electricity by 2050. Turbines might cause noise and change the viewshed. Although wind power plants have relatively little impact on the environment and communities compared to conventional power plants, concern exists over the sound sometimes produced by the turbine blades and visual impacts to the landscape. Though wind turbines harm wildlife less than some conventional sources of electricity, turbine blades could damage local wildlife. Electricity generation that pollutes the air and water causes wildlife fatalities through acid rain, mercury poisoning, habitat disruption due to warming temperatures, and more. However, birds have been killed by flying into spinning turbine blades. Blade strikes have been greatly reduced through technological development or by properly siting wind plants. Currently, the National Renewable Energy Laboratory's National Wind Technology Center (NWTC) is supporting wildlife technology research validation designed to reduce bird and bat fatalities at wind energy projects. The research provided at the NWTC will serve as a pipeline to the American Wind Wildlife Institute's technology verification program and similar efforts aimed at supporting commercialization of these products.
