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Project Presentation Paper

  1. 1. The Potential Economic and Environmental Benefitsof Geothermal Energy to The Anchorage Area Harvey Brittain 2/23/2012 Email:
  2. 2. Abstract Diminishing oil resources are a major concern for the near future. With renewable energies emerging as a necessity for our persistence, geothermal energy surfaces as a potential replacement for carbon based fossil fuels as an energy resource. This project examines what geothermal energy is, what causes it, and what it can provide with the aid of a geothermal power plant to the city of Anchorage. Four Geothermal research drilling sites located in California will be studied in an attempt to assemble data for this evaluation. Geothermal energy is one of the renewable energy resources of the future; however, further research is still needed in the progression of its uses. This project will contribute to the understanding of geothermal processes for the general public not actively involved in the topic of renewable energies, and develop a thesis for the benefits of the utilization of geothermal energy. The overall goal of this project is to better understand geothermal processes, and to better inform the community of the potential environmental and economic benefits of utilizing geothermal processes in the Anchorage area. This will allow for the potential aid in development of geothermal resources surrounding the Anchorage area. Introduction In today’s society, renewable energies are currently a secondary importance with regard to overall energy generation. With the utilization of fossil fuels as our primary source of energy, there are some undesirable side effects that are becoming less and less tolerated by industrialized societies. These side effects would include, but are not limited to, undesired effects on the environment, our health, and the prospect of reducing availability within about 150 years (Ueckermann 2008). Due to these factors, and an increase in energy demands caused by an increasing population, the demand for the development of renewable energies to reduce our dependency on fossil fuels has significantly increased. A potential source of energy that, if advanced, could provide much of the world’s energy needs is geothermal energy.
  3. 3. However there are some factors influencing the utilizing of this resource. These factors include a lack of technology development, tectonic activity, access to the energy source, stable temperatures, and lack of “useable” (based on power plant use, a minimum of 72ᵒ C) temperatures (DiPippo 2008). The lack of technology could be considered the main inhibitor as other factors; such as accessibility to the energy source, stable temperatures, and an absence of useable temperatures, can be overcome providing some advancement. Volcanically active tectonic margins however cannot yet be overcome by technology, only avoided based on location. Despite these inhibiting factors, an increased drive to further development this energy source is leading to the progression of advanced technologies that will allow us to successfully utilize it. Project Goal What is geothermal energy and how might it benefit the city of Anchorage both economically and environmentally? Here, I answer these questions with a goal of providing the public with a better understanding of this potentially valuable resource. The economic evaluation compare 10 years of energy production and expense data (from 2001-2010) for the city of Anchorage with production and expense statistics from four operating geothermal power plants. I will use this comparison to evaluate the potential economic benefit to Anchorage of a binary geothermal power plant, using Mt. Spurr as a power source. The environmental evaluation will compare basic information, such as the annual weight of emissions, from geothermal power plants and petroleum oriented power plants, and then I describe the pros and cons of each. Below, I list specific objectives of this paper:  Geothermal Energy o Review of literature and case studies that summarize our current understanding of geothermal processes. This information will be used to gain a basic understanding of what geothermal processes are.  Geologic Summary of Alaska o Compiled evidence of the geology of Alaska will be used to describe the geologic evolution of Alaska. This evidence will be used to gain a basic understanding of the existing geologic structure of Alaska to better understand the origins of the geothermal potential of Alaska.
  4. 4. o Summary of Alaska’s geothermal formation will be provided to explain the basis for the geothermal potential near the Anchorage area.  Economic Evaluation o Evaluation of the economic effects to Anchorage if the potential utilization of geothermal energy is implemented.  Environmental Evaluation o Evaluation of the environmental effects on the utilization of geothermal energy. Geothermal Energy The word ‘geothermal’ comes from Greek roots; the combination of the words “geo” (earth), and “thermos” (hot) (DiPippo 2008). Geothermal energy has been in use in the form of hot springs as a form of bathing, and relaxation since before civilizations were conceived. It is a form of renewable energy derived from heat found within the earth’s crust, and resources vary widely from one location to the next, depending upon the temperature and depth of the resource, the rock chemistry and the abundance of groundwater. This source of heat is caused by thermal energy that is continuously generated by the decay of radioactive isotopes of underground rocks that are stored within the globes interior (Ueckermann 2008), or is created by the thermal conduction of magmatic intrusions. This heat source is as inexhaustible and renewable as solar energy. When it comes to comparing the two energy sources, solar energy is the cleanest and most efficient when available; however the fact that solar energy can only be utilized to its fullest extent when the solar panels are facing the sun gives rise to geothermal energies advantage in consistency. The always changing tilt of the earth’s axis can also have an effect on how efficient solar panels are. There are 4 types of known geothermal systems: hydrothermal, hot dry rock, geopressured, and magmatic systems; of which only one is being utilized due to technological restrictions. The system presently being exploited is the hydrothermal system. To become available for energy conversion, heat is brought to or near the crust’s surface by thermal conduction, and by intrusion into the earth’s crust by molten magma originating from below the crustal layer. When this heat source comes into contact with groundwater, the ground water becomes heated resulting in the production of geothermal energy produced in the form of hot water and steam. Figure 1 and Figure 2 depict this process:
  5. 5. Figure 1: Shows the approximate thicknes and structure of the earth’s lyers. Figure 2: Shows the process of geothermal activity. This heated ground water can be applied for the direct use of heating homes, greenhouses, public buildings, streets, sidewalks, and other structures or appliances that may require heat to be functional. These
  6. 6. are known as direct uses of geothermal energy (Huenges and Ledru 2010). Geothermal energy is also and in most cases a source for the production of electricity. Utilization of this heat source as a means of energy production has however only been engaged since the early 20th century. The first know occurrence of this energy conversion of geothermal heat to electricity occurred at Larderello, Italy in 1904 (Gupta and Roy 2007). With geothermal energy being a cleaner renewable energy source, the continually diminishing petroleum and fossil fuel reserves, has allowed for it to become sought after. Today more than 20 countries generate electricity, about 60 countries make direct use of geothermal energy, and about 15,000 GW are being deployed worldwide (Gupta and Roy 2007). With the utilization of geothermal energy on the rise, the search for this renewable energy source is also increasing. Since we know that geothermal energy is brought to or near the crust’s surface through thermal conduction by intrusion into the earth’s crust via molten magma, it can be assumed that geothermal potential exists near areas of active tectonic margins, and volcanic regions. As active tectonic margins and volcanic regions are highly correlated, and commonly share a link with the same aspects as occurrences of geothermal energy, this assumption can be deemed as an educated guess. This can also be backed by research that shows high correlations between tectonic activity and an increase in the sub-surface temperature gradients of the surrounding areas (Ueckermann 2008). An example of this can be found surrounding the pacific plate, commonly known as the ring of fire. With the presence of tectonic activity, the presence of volcanic activity is common dependent upon the intensity of said tectonic activity; the higher/more frequent the activity, the more probability of the presence of volcanic activity. When the temperature gradient averaging 30ᵒ C/1 K, or 3 C/100 m, becomes shallower closer to the crust’s surface (DiPippo 2008); depending upon the circumstances of the area, namely the structural formation of the rocks, water originating from the water table is heated through thermal conduction, and either stored underground or pushed toward the crust’s surface through cracks, fractures, or faults in the rock. When this hot water becomes exposed (depending upon the available pressure and flow of
  7. 7. the water, permeability of the ground structure, and other components), it is known as a hot spring, geyser, or fumarole. There are several methods that can be used to locate geothermal prospects, finding these prospects can be as easy as visually observing the activity; however not all such activity is located within the vicinity of a population. Other methods of finding the geothermal potential for economic utilization can be used. As mentioned, one of the most common methods is observation, but when that fails, the utilization of seismic, electrical surveys and test drilling in areas with known potential for geothermal activity is implemented. These methods are however only used to confirm the presence of geothermal activity, rather than a means of initial discovery. When seismic and electrical surveys are conducted, data can be collected by using the principles of seismology to estimate the earth’s sub-surface profile from reflected seismic waves, in other words, the way this technology is used to collect data is similar to that of sonar. When test drilling is conducted, a drill rig is placed at a desired location and used to cut into the earth’s surface to extract a sample. From this sample, information such as rock type, mineralization, depth, heat, bedding structure, bedding direction, bedding angle, and many other things depending on what the exploratory drilling is being conducted for, are used to determine the level of potential. When looking for geothermal activity, some common things that are looked for can and generally include temperature, hydrothermal alteration to the rocks, rock type, and geothermal- fluid (heated water with chemical alterations). In this process, the activity is either observed, or looked for in areas that generally correlate well with the occurrence of geothermal energy (Huenges and Ledru 2010). The last common method used for finding geothermal potential is through airborne surveys. There are two implemented methods to date, the first is thermal inferred imaging, and the second is aeromagnetic surveys. When using an inferred imaging systemas a means of surveying, you are using the technology to simply look for anomalous surface temperatures that would signify the occurrence of geothermal activity. When using an aeromagnetic systemas a means of surveying, the technology is similar to that of some seismic surveying in that it utilizes magnetics to recover data, and with high-precision, it in a sense accounts for
  8. 8. vegetation on the surface when taking a snapshot of the ground. This allows for the detection of geological features important in geothermal exploration. Both of these methods are highly accurate, and are very useful when trying to survey inaccessible areas (Gupta and Roy 2007). Once the geothermal energy is found, there are multiple ways that it can be harvested. To date, the available four known geothermal systems can be utilized by 4 types of plants: flash steam(single and double), dry-steam, binary cycle, and advanced geothermal energy conversion systems, that are able to effectively convert the heat energy into electrical or heating energy. The type of plant is determined by the nature of the geothermal resource at the site. The following will be a description of how each of these plants operates: In a flash steampower plant, a combination of steamand hot water is pumped into a flash tank from the well where steamis separated from a portion of the water in a separator. Steam is first utilized to power a turbine, the remaining water then flashes into steam due to high temperatures and pressures to power a turbine. The residual water is then re-injected back into the reservoir, or used in a condenser depending if the plant has a condenser. Depending upon the temperature levels of the resource, you can potentially use a second stage flash tank were the process is the same as the first flash tank. Known as a double-flash steam plant, it can only be used when high temperatures are present. A single-flash steamplant is normally utilized when temperatures of the reservoir are lower (in excess of 180ᵒ C) (DiPippo 2008). In a dry-steam power plant, steam(such as obtained from geysers) is piped directly in to the plant to provide power for the turbines. The used steam is then condensed and run through the plant’s cooling system before being injected back into the reservoir to replenish the water and pressure levels. Though higher temperatures are generally sought, utilization were water beings to turn to steamat 100ᵒ C (212ᵒ F), is possible (DiPippo 2008). In a binary power plant, lower temperatures may be used down to 85ᵒ C. Although this plant has the ability to use higher temperatures, it is normally used in the place of other plants that cannot utilize lower temperatures. Through this system, geothermal fluids are passed through a heat exchanger were the heat is transferred into a low-boiling point binary liquid such as propane, isobutene, isopentane, or ammonia. When
  9. 9. heated to a high enough temperature, the binary liquid flashes into vapor to power the turbines. The vapor is then re-condensed through the cooled geothermal fluids in the condenser, and used repeatedly (DiPippo 2008). Figure 3 depicts this process. Figure 3: Depicts the process of a binary geothermal power plant. In the final type of power plant known as advanced systems, a variant of the binary cycle technology is used to potentially yield higher thermal efficiency. The process of extracting the geothermal energy is the same as a binary plant, however the difference is that it uses a combination of 2 binary fluids rather than 1, this process is known as the Kalina thermodynamic cycle (Gupta and Roy 2007). There is also an integration of hybrid singe-flash and double-flash systems, a hybrid of flash and binary systems, a combination of fossil fuel and geothermal energy systems, and a combination of heat and power plant systems technology available that are in some cases currently being utilized. Today, there are about 25 countries that generate electricity from the use of geothermal energies, and about 72 countries that make direct use of available geothermal energy. In 2000, the geothermal electrical installed capacity of the world was 7,974 MW with an annual electrical generation of 49,300 GWh, representing 0.3% of the world’s total electrical power generated. Many of the geothermal power plants have been in operation since the 1970’s; however, due to an average life expectance of 22years, renovations have been necessary to maintain the plants in economic working order. Most plants are able to operate at an
  10. 10. efficiency rate between 5.5% and 12% when using geothermal fluid temperatures approximately between 80ᵒ C and 180ᵒ C. Up to about 135ᵒ C net power generation efficiencies are below 10%; however at about 200ᵒ C efficiencies amounts to between 13 and 14% depending upon if the geothermal fluid is exploited exhaustively and the desired cooling temperature is reached. In general, the higher the available temperature of the geothermal resource, the higher the efficiency rate of the plant. These percentages are high in comparison to older generation plants, although low when compared to conventional power plants and fossil fuel energy generation. The trade of is that this energy source is more environmentally friendly and renewable (Kaltschmitt, Streicher, and et al 2007). With the knowledge that geothermal power plants emit little to no harmful emissions such as CO, CO2, NO2, or SO2, it is easy to see why geothermal energy is cleaner than fossil fuels. To look at what is environmentally damaging by the presence of geothermal plants, we will look at the beginning. Before the actual construction of the plant occurs, exploration needs to happen. When geothermal exploration takes place, test drilling is almost always utilized as a means of confirmation that a geothermal resource is present, and when this process is completed, very few environmental effects remain, the only thing left is a well head (used to protect the chemistry and function of the water table, and to keep life forms from stepping into the hole), and effects comparable to those of natural gas exploration; it is also possible to re-cultivate the drill site, therefore little damage remains at the drill site. Under normal operation, due to the circulation of geothermal fluid within the heat exchanger, small concentrations of salts and minerals may be dissolved below the earth’s surface; this however has no known detrimental effects on the environment. Also during normal operations, it is known that a geothermal plant is not very efficient. This results in high quantities of waste heat to be released. From these factors current viewpoints suggest that no significant detrimental effects on humans and the natural environment are likely to occur. When compared to observed volcanic areas of the earth, malfunctions that result in the release of geothermal fluid onto the earth’s surface have a low environmental impact. In all, the most environmentally
  11. 11. harmful aspect of a geothermal plant is the disposal of the plant when operation ceases (Kaltschmitt, Streicher, and et al 2007). When considering the utilization of a geothermal power plant, it is safe to assume that it is one of the most environmentally friendly methods of producing energy effectively for the consumption of society. When economically considering the use of geothermal energy, there are many factors that need to be deliberated. Geologic Summary of Alaska Alaska’s Geologic history is very long, and complicated. To date there are many competing studies and theories that sometimes contradict one another, accompanied by a lack of data that leads to an unstable conclusion of the processes that formed Alaska’s current geologic structure. The following will be a short list of one theory that describes the overview of the geologic and tectonic evolution of Alaska. This process is stated in ‘The Geology of Alaska’ as a model for ‘Tectonic Evolution’ (Plafker and Berg 1994). This model is presented to try and map out the structure of Alaska in chronological order of formation. The dates of this model will be used to try and track this formation. Even though there are geologic processes known to have occurred before 570 Ma that formed parts of Alaska existing today, the evidence is too fragmented to try and map. The following is a list of major building events, in respect to the geologic time line, as similarly described in ‘The Geology of Alaska’ (Plafker and Berg 1994); followed by Figure 4 that depicts known magmatic belts:  Cambrian to late Devonian (570-360 Ma) - Inferred configuration of continental margin composition terranes (CT’s), ultramafic rocks of the Livengood terrane, and Wrangellia intra-oceanic CT’s.  Early Mississippian to Middle Triassic (360-230 Ma) - Passive margin sedimentation occurred on the Artic and central CT’s, opening of the Cache Creek sea, rifting of the continental fragment of the Yukon CT’s, magmatic arcs developed on the southern Yukon CT’s, and east(?) dipping subduction zones of the Wrangellia CT’s.
  12. 12.  Late Triassic to Late Jurassic (230-160 Ma) – Passive margin sedimentation on the Arctic CT, arc volcanism and subduction took place on the intra-oceanic Togiak-Koyukuk CT, Quesnellia arc and its accretionary prism (Cache Creek terrane) were active along the continental margin above an east dipping subduction zone, the Yukon CT closed the Cache Creek Sea during the time that Stikine arc was active above a probable west dipping subduction zone, the Yukon CT collapsed against inboard terrane that overrode part of the Central CT and North American craton margin, fragments of oceanic crust were obducted onto terranes along the eastern margin of the Yukon CT (Slide Mountain terrane) and were locally emplaced onto the Yukon CT in Alaska (Seventymile terrane), the Wrangellia CT was characterized by eruptions of tholeiitic basalt in the Wrangellia terrane, eruption of bimodal volcanic rocks in the Alexander and Peninsular terranes, arc volcanism and formation of the accretionary prism of the Southern Margin CT above an east dipping subduction zone, Limestone with Tethyan faunas was scraped into accretionary prisms of the Cache Creek terrane and Southern Margin CT, and probable major northward movement of Wrangellia CT.  Late Jurassic to Aptian (160-120 Ma) – Incipient rifting occurred in the Canadian basin, Togiak-Koyukuk CT collided with the Artic CT resulting in 150+ km overriding of the Artic CT by the oceanic crust of the closed Kobuk basin, major contractional deformation and regional high pressure metamorphism in lower plate rocks and probable flip in the subduction zone, arc magmatism and accretion occurred above the east dipping subduction zones in the Wrangellia and Southern margin CT’s, Wrangellia terrane in Alaska offset by 600+ km from Wrangellia in British Columbia, and deformation of flysch basins along the continent- ward margin of the Wrangellia CT.  Aptain to Campanian (120-84 Ma) – The Canada Basin opened driving counterclockwise rotation of the Arctic CT and attached parts of the Togiak-Koyukuk and Oceanic CT’s, clockwise rotation of the Ruby terrane and attached parts of the Oceanic CT, placement of the Wranellia CT against continental margin terranes with the collapse of flysch basins, a major magmatic belt overprinted all major terranes in Alaska and is inferred to be related to east dipping subduction along continental margin, and thermal metamorphism throughout much of Alaska.
  13. 13.  Campanian to Paleocene (84-66 Ma) – Dextral transpression along the continental margin resulted in northwest movement of the Yukon CT along the Tintina, further clockwise rotation of the Ruby terrane, attachment of Oceanic CT to close the Yukon-Koyukuk basin, Kluane arc magmatism was active above the landward dipping subduction zone, and large accretion of arc derived sediments in the Southern Margin.  Paleocene to M. Eocene (66-50 Ma) – Large scale counterclockwise rotation of western Alaska and displacement of the western Arctic CT (Seward Peninsula), dextral displacement on the Denali fault formed the proto-Yakutat terrane, continued Kluane arc magmatism above landward dipping subduction zones, major volumes of acr derived sediment were scrapped into western part of the Southern Margin CT accretionary prism, and wide spread anatectic magmatism along the southern Alaska margin.  Eocene to Present (50-0 Ma) - Onset of northward Pacific plate resulting in formation of the Aleutian- Alaskan Peninsula arc, displacements on the intra-plate faults, formation of basins on land and contiguous continental shelves, Fairweather-Queen Charlotte transform boundary stepped northward, and Yakutat combined western Yakutat terrane and Pacific plate resulted in arc volcanism in the Wrangell Mountains and major uplift of eastern Chugach and saint Elias mountains.
  14. 14. Figure 4: Shows the known locations of magmatic belts in Alaska. (Plafker and Berg 1994). The purpose of this overview was to not only understand the geologic formation of Alaska, but to also understand the background processes of Alaska’s geothermal resources. This is important when trying to understand the reasons for the location of geothermal processes at Mt. Spurr’s. The following will be an overview of the geothermal resources of Alaska, in effect explaining the reason for geothermal activity at Mt. Spurr. Today, there are 108 known geothermal hot springs throughout Alaska, and about half of these are located primarily along the Aleutian volcanic arc. The rest of these hot springs are located along the Wrangell Mountain’s volcanic pile, Southeastern, central, and Northern Alaska; sometimes referred to as the Central Alaskan Hot Springs Belt (CAHSB), as shown in Figure 5.
  15. 15. Figure 5: Shows the known locations of hot springs (Blue), volcanic vents (Red), and the geothermal potential (Purple) within Alaska. (Alaska energy inventory 2012). Geothermal activity found along the Aleutian volcanic arc is generally found to be highly variable. This is due to the recent (Quaternary) magmatic processes known to the area. However not all geothermal energy is found only within regions of recent shallow magmatic intrusions. As described in the above geologic overview, Central and Northern (interior Alaska) geological activity mostly stopped pre-Quaternary. This means as commonly known, that these geothermal processes are caused by isotopic decay from plutonic granite known to the area, and believed to have formed during the late Triassic, Jurassic Periods. This allows for respectively rare stable temperatures to occur with respect to the temperature gradient. With all the known active geothermal areas, Alaska probable has the greatest potential for large scale geothermal energy development out of any other single North American region. The majority of this energy potential is also located close to populated areas. This only provides a greater likelihood of potential utilization. When considering this information for the potential utilization for the Anchorage area, knowing that the Anchorage area is located near geothermal potential, though not on any, is important. Understanding this information allows us to know that the closest geothermal resource for potential utilization to the Anchorage area is Mt. Spurr.
  16. 16. Economic Evaluation In this economic evaluation, four cases studies located in California will be representative of a Proposed Binary Geothermal Power Plant (PBGPP) to be installed for the use of the two companies that supply energy to the city of Anchorage; Chugach electric and Municipality of Light & Power (ML&P). The purpose of choosing a Binary Geothermal Power Plant (BGPP) over another type of geothermal power plant is due to the temperatures available at Mt. Spurr. No useable temperatures have been found yet, however the potential for temperatures that could be used by a BGPP is relatively high. The purpose of choosing Mt. Spurr as a potential source of energy is that it is the closest known geothermal energy resource being explored for utilization near the Anchorage area. For the purpose of maintaining accuracy, I have inflated all currency values to 2011 USD currency values. Concerning the values from ML&P and Chugach electric power companies, they have been based on 10 year weighted averages calculated from data for 2001 to 2010. For the comparisons for the evaluation, I have used 4 sample case studies from California. The averages created represent a potential binary geothermal power plant. These averages were then compared to evaluate an economic potential for the Anchorage area. Standard Deviations were also calculated for my sample cases studies to show accuracy through the variability. With the accuracy of this evaluation defined, I will look next at the affordability of a PBGPP for the City of Anchorage based on the average overall operating revenue of Chugach electric and ML&P. This will be accomplished through a comparison of average investment costs of a PBGPP to a 10 year average of the overall operating revenue and expenses of Chugach and ML&P. Next I will compare the average operating costs of a PBGPP to a 10 year average of the overall operating revenue and expenses of Chugach and ML&P. This information will be used to evaluate if the two companies can afford a BGPP based on the 10 year average; the potential values of a BGPP are acquired through averages of the four case studies mentioned above, this will allow for the functionality of this economic evaluation.
  17. 17. Next a comparison of a PBGPP’s cost/KWh to the operating cost/KWh for Anchorage, based on weighted averages, will be used to determine economic competitiveness. This is very important to the evaluation as it determines whether or not a BGPP can compete with other power plants that service the Anchorage area, economically. Lastly a comparison will be conducted between a PBGPP’s rated energy output in MW’s to the residential power sales for the Anchorage area from Chugach and ML&P. This comparison will determine how much a BGPP will be able to add to the overall energy output, in effect measuring its level of benefit. As of 2010, the city of Anchorage was supplied energy through two companies; Chugach electric, and the Municipality of Light and Power. Chugach sold 2,594,493,383 KWh (2,594.49 MW), and ML&P sold 1,186,628,608 KWh (1,186.82 MW) of overall energy on average individually. This brought an average overall operating revenue of $260,372,065.4 to Chugach, and $108,867,087 to ML&P. With an overall average expense of $229,022,869.5 for Chugach and $66,658,840.98 for ML&P; a profit of $31,349,195.9 remains for Chugach and $42,208,246.02 for ML&P. Due to restrictions on accessibility to this profit margin, the majority of this profit is not available for the direct use by the companies; however there is more than enough available to each company for either company to be able to individually fund the construction of a BGPP that has an average investment (construction) cost of $2,636,089.13, and an average annual operating cost of $656,432.62. Now that the question of affordability has been answered, a determination of whether or not a BGPP will be economically competitive compared to other power plants, needs to be reached. On average when it comes to how much is financially gained and how much energy is utilized from the Anchorage area for each company, weighted averages need to be instituted to account for the percent difference in energy sales to the Anchorage area between the two companies Chugach and ML&P. A weighted 10 year average operating revenue of $17,784,348.60 for ML&P and $79,226,119.70 for Chugach, compared to the overall operating revenue average of $108,867,087 for ML&P and $260,372,065.4 for Chugach, yields that Anchorage accounts for 16.34% of the ML&P total operating revenue and 30.43% of the Chugach electric total operating revenue.
  18. 18. When considering the utilization of a BGPP for the Anchorage area, understanding the percent of the revenue that will be affected due to the implementation of the plant, is important. To compare the average operation costs/KWh of $0.073 for the Anchorage area; with respect to the percent of the average operating revenue, to the average cost/KWh of $0.27 for the PBGPP, the conclusion that the PBGPP is more expensive to run than the current methods of the two companies that provide energy to the Anchorage area is reached. This means that the PBGPP is not economically competitive with other types of power plants used by the two companies. This conclusion however is inaccurate as the values used to create an average cost/KWh for the PBGPP are to variable to be statistically accurate. Statistically looking at the sample size of the PBGPP, there are four samples/case studies. This is a low number when trying to get the most accurate numbers possible. In general the larger the sample size, the better the results are going to be. However in this case, only four samples are available, a statistically strong result is unlikely. Knowing that on average, a geothermal plant can produce energy at lower costs than other sources of energy like coal, oil and gas; than what was not represented in my findings, I calculated the Standard Deviations to measure the variability of my data to resolve this issue. My results are as shown in Figure 6, Figure 7, and Figure 8: Figure 6: Showsthe variabilityof the sample case studdiesbasedonthe cost/KWhthroguhthe standarddeviation when comparedto the average cost/KWh. 0 0.1 0.2 0.3 0.4 0.5 0.6 1 2 3 4 USD/KWh CaliforniaCase Studies SD = 0.208 Avg. = 0.267
  19. 19. Figure 7: Showsthe variabilityof the sample case studdiesbasedonthe ratedMWh throguhthe standard deviation whencomparedtothe average of the ratedMWh. Figure 8: Showsthe variabilityof the sample case studdiesbasedonthe average annual investmentandopperating costs throguhthe standarddeviationwhencomparedtothe average of these values. These standard deviation values mean that the data has a high variability, and are inconsistent with known averages. With the range between the cost/KWh of the PBGPP to significantly variable to be considered statistically strong when compared to the average cost/KWh of Anchorage. This means the null hypothesis that the data are highly variable is accepted, making the evaluation with the average PBGPP cost/KWh statistically weak when comparing it to the average cost/KWh of Anchorage. Finally we will look at what a BGPP can off in percent of MW compared to an existing average of MW available to the anchorage area. On average, Anchorage is supplied with 551,140,567.4 KWh (551.14MW) 0 10 20 30 40 50 1 2 3 4 5 6 7 8 RatedMWh CaliforniaCase Studies SD = 14.126 Avg. = 12.537 0 0.5 1 1.5 2 2.5 3 3.5 1 2 3 4 MillionUSD CaliforniaCase Studies Investment Cost Annual Operating Cost SD = 0.164 Avg. = 0.656
  20. 20. from Chugach and 147,764,346.6 KWh (147.76 MW) from ML&P; the combination these amounts, yields a residential average of 698,904,914 KWh (698.90 MW). The PBGPP on average produces a rated output of 5.7 MW, equaling 0.82% of the average power consumption for the Anchorage area. This is not a significant number, meaning that the PBGPP is not very beneficial when it comes to providing energy. With this knowledge based on the averaged values of the PBGPP compared to the 10 year averages of Chugach electric and ML&P; the installation of a BGPP at Mt. Spurr, while assuming an average temperature of 130ᵒ C (the average temperature utilized by the case studies used for the averages of a PBGPP), for the utilization of the Anchorage area would not be economically feasible. The PBGPP would however not be able to compete economically with other power plants based on cost/KWh, and energy output in MW. While this study showed that using the PBGPP averages was statistically strong, it also showed that the data is to variable. Taking into consideration that the bigger the geothermal power plant is, the more energy (MW) it is able to produce, and the cheaper it becomes to produce this energy; a bigger BGPP would be more economically competitive. Increasing the size of the plant dose in effect cost more; however, the revenue produced form the Anchorage area would still be able to cover a significant amount allowing for the PBGPP to be a reality. Environmental Evaluation In this environmental evaluation, a comparison of gaseous emissions evaluating a study conducted by Ronald DiPippo (2008) will be conducted between various binary geothermal, coal-fired, oil-fired power plants, and gas turbines. Emissions will include the following gases: CO2, SO2, and NO. Other environmental aspects described in this evaluation include: noise pollution in decibels, biological effects, thermal effects, and chemical pollution. These effects will represent the effects of binary geothermal power plant that could potential be utilized for the Anchorage area. In his study, DiPippo states that binary geothermal power plants emit zero CO2, SO2, or NO, as they are closed systems. In comparison coal-fired power plants emit 994 kg/MWh of CO2, 4.71 kg/MWh of SO2, and
  21. 21. 1.955 kg/MWh NO; oil-fired power plants emit 758 kg/MWh of CO2, 5.44 kg/MWh of SO2, and 1.814 kg/MWh of NO; and gas turbines emit 550 kg/MWh of CO2, 0.0998 kg/MWh of SO2, and 1.343 kg/MWh of NO. Other hydrothermal power plants emit either little or no emissions. This means that binary geothermal power plants are the most environmentally friendly concerning air pollutants (DiPippo 2008). Another environmental aspect that concerns air pollution is noise pollution. Depending upon the distance from the source and whether or not the source is muffled, a geothermal air drilling rig can produce 84 to 114 decibels (db); in comparison, free-way traffic is 90 db, and a vacuum cleaner is 70 db. The human threshold of pain is only 120 db, this means that the noise level is tolerable; however the range signifies that a geothermal power plant can be fairly noisy. Other environmental aspects are thermal effects, chemical pollution, and biological effects. Though no cases have occurred that would be considered significant, however the potential still exists. Thermal effects are caused by reinjection of brine from the geothermal plant into the reservoir. As the temperature of the brine is colder going in then when it was extracted, this can cause a decrease in the temperature of the reservoir. Reinjection of brine back into the reservoir leads to chemical pollution of the ground, and potentially the water table. In the brine, gases constitute primarily of CO2 (up to 90% by weight), H2S, and smaller amounts of NH3, CH4, N2, H2, Hg, B, and Rn; with the total accounting for only 5% of the brine (Gupta and Roy 2007). This application of chemical pollution can also be attributed to air pollution for flash-steamand dry-steam power plants. Concerning biological effects, no environmentally damaging effects have been observed. This can be seen in the following table.
  22. 22. CO2 kg/MWh SO2 kg/MWh NO kg/MWh Binary Power Plant 0 0 0 Coal Power Plant 994 4.71 1.955 Oil Power Plant 758 5.44 1.814 Gas Turbines 550 0.0998 1.343 Table 1: Compares the average annual emissions by kg/MWh of four types of power plants. In conclusion, there are some environmental effects from the utilization of binary geothermal power plants, though none are significant when compared to the environmental effects of other types of power plants. This includes other types of hydrothermal plants that are still less environmentally harmful than coal, gas, or other fossil fuel driven power plant. This means that if a binary geothermal power plant were to be installed within the Anchorage area, it would be environmentally beneficial if replacing an alternative fossil fuel power plant, as it provides cleaner effects from energy production. Summary After comparing the average investment and annual costs of the 4 samples case studies to the 10 year averages from the municipal light and power, and Chugach electric power companies for revenues and expenditures, I have determined that a Binary geothermal power plant can be easily invested in within the range of available profit margin from the Anchorage area. This can be seen through the comparisons in Figure 9 and Figure 10.
  23. 23. Figure 9: Shows the comparison of average expenses to operating revenues of the Anchorage area over a ten year period. Figure 10: Shows the comparison of the ten year average annual profit margin for the Anchorage area to the average investment and annual operating costs of a binary geothermal power plant.  In conclusion, a binary geothermal power plant, based off my averages, is affordable in comparison to the combined profit margin of the Anchorage area from the ML&P and Chugach electric power companies. From my results, even though a binary geothermal power plant cannot add much power to the Anchorage power grid, geothermal energy is a far cleaner energy source than fossil fuels. At this time, the investment in a binary geothermal power plant does not make economic sense, however geothermal energy will not go up in cost over time when compared to fossil fuels. This is something to keep in mind when considering alternative renewable energy resources. 0 50 100 150 200 250 300 350 400 450 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 MillionUSD 10 year average Expenses Operating Revenue 0 10 20 30 40 50 60 70 80 Investment costs Average Annual Profit Annual opperating costs MillionUSD Affordability
  24. 24. As shown earlier, my cost/KWh data for my sample case studies was to variable to provide an accurate representation. This was a result of inefficient sample plants. Newer technologies allow plants to be more efficient; however I was unable to attain the data that represented this due to proprietary reasons.
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