Rabco Solutions | Solar and Geothermal Energy

1. What are the benefits of using geothermal energy?
Answer: Several attributes make it a good source of energy.
• First, it's clean. Energy can be extracted without burning a fossil fuel such as coal, gas, or oil. Geothermal fields produce only about one-sixth of the carbon dioxide that a relatively clean natural-gas-fueled power plant produces, and very little if any, of the nitrous oxide or sulfur-bearing gases. Binary plants, which are closed cycle operations, release essentially no emissions.
• Geothermal energy is available 24 hours a day, 365 days a year. Geothermal power plants have average availabilities of 90% or higher, compared to about 75% for coal plants.
• Geothermal power is homegrown, reducing our dependence on foreign oil.

geothermal energy2. Why is geothermal energy a renewable resource?
: Because its source is the almost unlimited amount of heat generated by the Earth's core. Even in geothermal areas dependent on a reservoir of hot water, the volume taken out can be re-injected, making it a sustainable energy source.

3. Where is geothermal energy available?
Hydrothermal resources - reservoirs of steam or hot water - are available primarily in the western states, Alaska, and Hawaii. However, Earth energy can be tapped almost anywhere with geothermal heat pumps and direct-use applications. Other enormous and world-wide geothermal resources - hot dry rock and magma, for example - are awaiting further technology development.

4. What are the environmental impacts of using geothermal energy?
Geothermal technologies offer many environmental advantages over conventional power generation:
• Emissions are low. Only excess steam is emitted by geothermal flash plants. No air emissions or liquids are discharged by binary geothermal plants, which are projected to become the dominant technology in the near future.
• Salts and dissolved minerals contained in geothermal fluids are usually re-injected with excess water back into the reservoir at a depth well below groundwater aquifers. This recycles the geothermal water and replenishes the reservoir. The City of Santa Rosa, California, pipes the city's treated wastewater up to The Geysers power plants to be used for reinjection fluid. This system will prolong the life of the reservoir as it recycles the treated wastewater.
• Some geothermal plants do produce some solid materials, or sludges, that require disposal in approved sites. Some of these solids are now being extracted for sale (zinc, silica, and sulfur, for example), making the resource even more valuable and environmentally friendly.

Geothermal power plants5. What is the visual impact of geothermal technologies?
District heating systems and geothermal heat pumps are easily integrated into communities with almost no visual impact. Geothermal power plants use relatively small acreages, and don't require storage, transportation, or combustion of fuels. Either no emissions or just steam are visible. These qualities reduce the overall visual impact of power plants in scenic regions.

6. Is it possible to deplete geothermal reservoirs?
The long-term sustainability of geothermal energy production has been demonstrated at the Lardarello field in Italy since 1913, at the Wairakei field in New Zealand since 1958, and at The Geysers field in California since 1960. Pressure and production declines have been experienced at some plants, and operators have begun reinjecting water to maintain reservoir pressure. The City of Santa Rosa, California, pipes its treated wastewater up to The Geysers to be used as reinjection fluid, thereby prolonging the life of the reservoir while recycling the treated wastewater.

7. How much does geothermal energy cost per kilowatt-hour (kWh)?
At The Geysers, power is sold at $0.03 to $0.035 per kWh. A power plant built today would probably require about $0.05 per kWh. Some plants can charge more during peak demand periods.

8. What are the different types of geothermal power plants?
There are three geothermal power plant technologies being used to convert hydrothermal fluids to electricity: dry steam, flash steam and binary cycle. The type of conversion used (selected in development) depends on the state of the fluid (steam or water) and its temperature.

9. What does it cost to develop a geothermal power plant?
Costs of a geothermal plant are heavily weighted toward early expenses, rather than fuel to keep them running. Well drilling and pipeline construction occur first, followed by resource analysis of the drilling information. Next is design of the actual plant. Power plant construction is usually completed concurrent with final field development. The initial cost for the field and power plant is around $2500 per installed kW in the U.S., probably $3000 to $5000/kWe for a small (<1Mwe) power plant. Operating and maintenance costs range from $0.01 to $0.03 per kWh. Most geothermal power plants can run at greater than 90% availability (i.e., producing more than 90% of the time), but running at 97% or 98% can increase maintenance costs. Higher-priced electricity justifies running the plant 98% of the time because the resulting higher maintenance costs are recovered.

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10. What makes a site good for geothermal electric development?
Hot geothermal fluid with low mineral and gas content, shallow aquifers for producing and re-injecting the fluid, location on private land to simplify permitting, proximity to existing transmission lines or load, and availability of make-up water for evaporative cooling. Geothermal fluid temperature should be at least 300º F, although plants are operating on fluid temperatures as low as 210º F.

11. What is an Enhanced Geothermal System (EGS)?
An Enhanced Geothermal System (EGS) is a man-made reservoir, created where there is hot rock but insufficient or little natural permeability or fluid saturation. In an EGS, fluid is injected into the subsurface under carefully controlled conditions, which cause pre-existing fractures to re-open, creating permeability.

12. What is geothermal energy?
Geothermal energy is heat ("thermal") derived from the earth ("geo"). It is the thermal energy contained in the rock and fluids, that fill the fractures and pores in the rocks that form the earth's crust.

13. How can geothermal resources be used?
High and Moderate temperature geothermal resources can be used to generate electricity. Low temperature geothermal resources can be used for a wide range of direct uses, e.g. district and space heating, industrial processes, greenhouses, aquaculture and spas.

14. Where can I find more information on geothermal resources, specifically electrical generation?
Answer: Some excellent sources of information include:
• Office of Energy Efficiency and Renewable Energy, www.eren.doe.gov
• Geothermal Resource Council, www.geothermal.org
• Geothermal Energy Association, www.geo-energy.org

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15. Why is geothermal energy "environmentally friendly"?
Unlike coal fired and natural gas fired power generation plants, the state of the art geothermal binary cycle plant produces virtually no emissions. When compared to natural gas, a 100 MW geothermal power generator offsets 190,000 pounds of NoX and SoX (nitrogen dioxide and sulfur dioxide) per year. Additionally, it eliminates 780 million pounds of CO2 emissions. The reduction in emissions, when compared to coal fired plants, is even greater. The binary cycle technology was pioneered at Raft River, Idaho in the early 1980s.

16: Why is geothermal considered a renewable energy resource?
All types of geothermal energy are renewable as long as the rate of heat extraction does not exceed the rate at which the thermal reservoir it depends upon is renewed by heat from the earth's magna. Geothermal reservoirs that tap the earth's heat for energy production typically have 30 to 50 year life as the plant's equipment wears out. Indeed the world's first geothermal power plant at Larderello, Italy was commissioned in 1913 and is still producing. The Geysers, California facility has been in production since the early 1960s.

17. Does technology exist to extend reservoir life?
Yes, in particular with binary plants since the water produced from the fracture system can be re-injected back into the fracture system and reheated by the source rock. Currently, Calpines, the owner of Geysers, is constructing a $163 million, 41-mile pipeline to move the effluent water from the City of Santa Rosa's sewage system for injection into the geothermal reservoir. The Raft River property of US Geothermal Inc. ("USGEO") will involve a binary system to save and re-inject water back into the fractures for reheating. The scheduled reservoir modelling will identify where to position injectors for the maximum benefit.

18. What is the geothermal power capability in the United States and how does it compare to the overall electrical power generation capacity?
In 1999, geothermal energy provided 0.4 % of US electricity generation, 14.3 million Megawatts hours (MWhr), enough electricity to service 1,400,000 average households. US geothermal capacity was 2,850 MW located primarily in California and Nevada.
19. Why has there not been greater development of US geothermal capacity?
Answer: The development of geothermal power thorough the 1990s has been impeded by two factors: location and cost. In respect of location, most geothermal reservoirs are located in the Western States and specifically in areas which enjoyed excess electrical capacity. For example, Raft River in Idaho and the Newberry Caldera in Oregon are within the Bonneville Power Authority (BPA) system, which distributes hydropower from the Columbia River dams. Local electrical distributors like Idaho Power, and Pacific Power could service their clients by purchasing from the BPA the lowest cost electricity in the USA.

In respect of costs, prior to recent technological advances, the cost of developing geothermal reservoirs, building generators and operating them was between 6 cents and 8 cents per kilowatt hour (Kwh). The major sources of new electrical power generation in the 1990s and until recently was coal and natural gas. These sources were competitive in the 4 to 6 cent per Kwh range.

20. What has changed over the last five years to make geothermal energy a financially attractive source of electricity?
Four factors have contributed to the current focus on geothermal energy:
1. Advancements in technology, which have improved the efficiency and reduced the cost of geothermal power generation.
2. Growth in electricity demand in the Western States.
3. The Green Power movement.
4. Volatility in natural gas markets.

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21. Please identify the improvements in geothermal power generation.
Technology has led to greater efficiencies in geothermal power generation due to (a) improvements in submersible pumps, (b) improvements in turbine efficiency (c) 3-D reservoir modeling techniques.

When the Department of Energy (DOE) tested one of the world's first binary power plant at Raft River in the early 1980s, the highest volume pump they could use was a 600 gallons per minute (gpm) line shaft unit. Today, submersible pumps are utilized that exceed 2,800 gpm with greater energy efficiency and less maintenance. New turbine technology, like the GE Rotoflow Expansion Turbine delivers 20% and greater output. Additionally, the application of 3-D reservoir models, using tracer elements to map the fracture system will ensure that development wells are located for maximum productivity.

Preliminary engineering at Raft River indicates that by applying these new technologies, wells that produced 1.3 net MW are now capable of approximately 3.4 net MW.

22. What has given rise to growth in the demand for electricity?
Simply, the Western States in which the geothermal reservoirs are located have the greatest increase in population in the USA over the last decade. More households mean more electricity is consumed. For example, the combined population of Idaho, Washington and Oregon in 1960 was 5,289,000. This reference year is important because, with the exception of the Hungry Horse dam, in Northwest Montana, the Columbia River hydro-dams, which the Army Corps of Engineers had commenced in the early 1940s, had been completed. The US Census Bureau population estimate for the same three states on June 1, 2001 was 10,782,000. The projection for 2010 is 12,018,000. Additionally, the state of Utah, which borders the Raft River location, grew from 891,000 in 1960 to 2,270,000 in 2001 and is projected to have a population of 2,551,000 in the year 2010.

23. What do you mean by Green Power?
Green Power represents sources of power that are non-polluting. These sources include solar, wind, geothermal as well as run-of the-stream hydro. Currently, the Green Power movement is gaining momentum from three initiatives, (a) voluntary green power purchases where consumers pay a premium to their local utility to in-turn purchase green power, (b) state and federal government departments being mandated to purchase green power, (c) state legislated renewable energy portfolio standards (RPS) which set targets for utilities to ensure that a minimum percentage of their supply is from green power. Nevada has instituted a RPS, which requires a minimum 15% green power component by the year 2013 scaled from 5% in 2003. New Mexico has adopted a 10% RPS, and California adopted a 20% RPS. Arizona, Oregon and Idaho are also in various stages of discussion, adoption or implementation of a RPS.

24. What is the implication of natural gas supply on geothermal power?
The growth of electrical demand, in the Western States, has been met through the 1990s and early in this decade by the construction and commissioning of combined cycle natural gas powered generators. These facilities meet current federal emission requirements, can be constructed in a short timeframe, and if scaled in the 250 MW size and greater, they cost approximately $850,000 to $900,000 per MW of capacity. However, in comparison to geothermal and wind power, they have higher operating costs due to the purchase price of natural gas.

The Energy Information Agency, in a report to Secretary Spencer Abraham, in December 2001 (entitled US Natural Gas Markets: Mid-Term Prospects for Natural Gas Supply), has determined that the reserve/life index of new gas reservoirs has fallen to 3.9 years. Additionally, in order to maintain deliverability at current levels, the rate of well drilling must be maintained. Accordingly, the wellhead price of natural gas must be high enough to generate new activity. Since mid-2000, wellhead prices have varied from $1.80 per MCF to over $9.00 per MCF. One-megawatt hour (MWhr) requires approximately 5.5 MCF of natural gas. The cost to deliver gas from the wellhead, depending upon your location in the USA, varies between $1.50 and $3.00 per MCF. Therefore delivered prices in the $5.00 to $6.00 range are not unusual. At $6.00 per MCF, the feedstock price is 3.3 cents per Kwh upon which you must add operating costs and recovery of capital. During the winter of 2001, delivered gas prices achieved $12.00 per MCF in California and the Pacific Northwest. Whereas well drilling activity for 2002 is 60% to 65% of 2001 activity, history is likely to be repeated. Geothermal energy has no feedstock cost.

25. Please explain the difference between gross and base load (net power) production.
Binary power plants have a very high utilization rate. The US industry average over 98% operating efficiency. The binary fluid, isobutene, must be cooled down before it is recycled for vaporization in order to run the turbines. When the atmospheric temperature is high, power is used to run large fans in order to move the ambient heat from the binary fluid. Therefore the amount of deliverable electricity on a hot August day can be as much as 30% to 35% lower than in mid-February. Additionally, the well pumps and other mechanical systems in the plant consume electricity. New technology, referred as the Kalina cycle, has been developed to significantly reduce this differential.

26. How does Geothermal compare with Wind Power?
Wind Power has been the most successful source of Green Power to date, with 4,261 MW of capacity. The reasons include a very successful political lobby, the existence of a federal Production Tax Credit, and that wind generation can be installed in all 50 states. (The credit will be available to Geothermal retroactive to January 1, 2002 upon the Senate/ House Conference on the Energy Bill is completed).
Geothermal, because of its high efficiency, is more competitive in the long-term.

27. Are there any other considerations when comparing the two alternatives?
Yes, the ambient heat given off from a geothermal facility can be used as a heat source for hothouses, aquaculture or central heating. A second consideration is that as explained in Question #18, geothermal plants, at certain times in the year will produce electricity significantly higher than the base load.

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