Basic Study of Renewable Energy Alternatives for Electricity Generation in Dillingham/Aleknagik Region

Transcription

1 Basic Study of Renewable Energy Alternatives for Electricity Generation in Dillingham/Aleknagik Region Prepared for: Nushagak Electric and Telephone Cooperative, Inc. Prepared by: Tom Marsik Bristol Bay Environmental Science Lab University of Alaska Fairbanks Bristol Bay Campus October 2009

2 Table of Contents Table of Contents Introduction Wind Conventional Hydro Solar Biomass Wood, Fish Byproducts, Municipal Waste Hydrokinetic/Tidal Geothermal Acknowledgments Introduction Nushagak Electric and Telephone Cooperative (NETC) is a small utility that provides electric power via an electric grid for the Dillingham/Aleknagik area. The average load is about 2.1 MW, with the maximum of about 3.4 MW and minimum of about 1.4 MW. Except for a couple of non utility renewable energy systems (less than 20 kw), all electric power is currently produced via diesel generators. Because of the high cost of diesel and concerns about the sustainability of the current practice, Nushagak Cooperative is looking for alternatives for electric power generation. The purpose of this report is to outline many of the pros and cons of several renewable energy alternatives for power generation in the Dillingham/Aleknagik area. The alternatives considered are wind, conventional hydro, solar, biomass (wood, fish byproducts, municipal waste), hydrokinetic/tidal, and geothermal. These alternatives are evaluated from the perspective of existence of the resource in the region, quantity and resulting basic economic feasibility, stability and predictability of the source, and other factors impacting the feasibility. The purpose of this baseline study is NOT to determine which option is best; for many of these alternatives to diesel there is not enough data to make such an informed decision. Rather, the purpose of this report is to compile basic existing information that can be used to determine what further studies need to be done in order to determine the best alternative to diesel. Even though this report offers a basic economic analysis for several alternatives, the numbers presented are very broad estimates and further studies need to be done to refine the numbers. The broad estimates in this study are presented only for the purpose of prioritizing these future studies. 2

3 2. Wind 2.1 Existence Wind is an existing resource in the Dillingham/Aleknagik area and was once (before inexpensive diesel) used as the primary power source for the region. 2.2 Quantity and Resulting Economics Figure 2.1 maps the wind resource for the Dillingham/Aleknagik area and illustrates that the wind quantity varies widely. The flat topography around Dillingham is generally shown as Class 2 (or marginal ) wind resource, however, the tops of some mountains (e.g. Snake Lake Mountain or Cinnabar Mountain) are shown as Class 7 (or superb ). Because the wind resource map is largely based on modeling, more accurate wind data sources are needed. Some of these data needs are met by three studies that were performed in the region and were based on actual wind measurements. The first study, which involved erecting a meteorological tower close to the Dillingham hospital (site referred to as Kanakanak Site ), indicated a Class 3 (or fair ) wind resource [1]. A second study, which involved erecting a meteorological tower at the Wood River Road in Dillingham, indicated also a Class 3 wind resource [2]. The third study, which involved analyzing wind data from the Automated Weather Observing System (AWOS) at the Dillingham airport, indicated a Class 2 wind resource [3]. All three of these local studies are in a reasonable agreement with the wind resource map, which indicates Class 2 to Class 3 wind resource for these locations. The three Dillingham wind studies also included the energy production estimates for various wind turbines. The following data is for the Kanakanak Site. The gross capacity factor was estimated to be 31.1% for Vestas V27 turbines with 50m hub height. Vestas V27 is rated at 225 kw and up until 2009, it was the largest wind turbine operating in rural Alaska. Alaska Energy Authority s (AEA s) practice is to use an 80% factor to account for losses from icing, array losses (due to a cluster of turbines in one location), turbine down time, and blade soiling (bugs). Using this practice would result in 24.9% net capacity factor for the Vestas V27. For GE 1.5 turbines with 65m hub height, the gross capacity factor was estimated to be 37.0%. GE 1.5 is rated at 1.5 MW and three of these turbines were installed in 2009 on Kodiak Island. Using again the 80% factor to account for losses, the net capacity factor would be 29.6%. Taking 27% as an approximate number for the capacity factor for large installations using large turbines, and taking 2.1 MW as the approximate average load for the Nushagak Cooperative, an 8 MW wind installation would be needed to fully cover the load. Alaska Energy Authority (AEA) developed the following formula as a very rough estimate of the cost per installed kw based on existing installations in Alaska: Y = 24998X 0.197, where Y represents the total cost per installed kw of capacity to construct and integrate the wind project, and X represents the installed wind capacity in kw. For an 8 MW installation, this formula would result in about $4,300 per kw installed, which is about $34 million total for the 8 MW installation. It should be pointed out, though, that this total cost for a large installation covering all demand is presented here just for theoretical purposes because in order to cover all demand by wind, one would also need an energy storage facility, which can be very expensive and is not included in the $34 million. However, one can use these data as a baseline to, for example, estimate the cost of smaller wind installations integrated with another system (see Stability and Predictability section). No wind studies involving actual wind measurements have been done in the mountainous region near Dillingham/Aleknagik, where the wind resource map shows up to Class 7 wind resource (see Figure 2.1). The capacity factor for such a wind resource would be significantly higher, thus, the required installed capacity significantly lower than in the previous case discussed for the flat topography where Class 3 was assumed. The cost per kw of installed capacity could be higher, though, because of the need for longer transmission lines coupled with a more difficult 3

4 access in a mountainous terrain. Such a wind installation in the Dillingham/Aleknagik area can be compared to the 4.5 MW wind installation on Pillar Mountain on Kodiak Island in certain aspects (e.g. size of the system, mountain installation). The total cost of the Kodiak project including roads, transmission and connection to their system was $21.4 million, i.e. about $4,800 per kw installed. Figure 2.1 Wind resource map (source: Alaska Energy Authority) 4

5 2.3 Stability and Predictability Wind is an unstable energy resource. Even though the wind speed fluctuations on a semi long term scale (hours to days) can be partially predicted using weather forecasting methods, the fluctuations on a short term scale (seconds to minutes) are highly unpredictable. This variability and low predictability of wind pose great challenges for its use for electricity generation. One of possible solutions is the integration of wind with more controllable power sources, such as diesel generators or a hydro system. With such installations, though, there can be issues with power quality, especially with high penetration systems (i.e. systems with a large portion of the total energy supplied from wind). These power quality issues can be partially solved via using short term energy storage devices (such as fly wheels) and sophisticated control systems, which can be very expensive. Another solution is the combination of the wind system with an energy storage system, such as a battery facility or a pumped hydro system. A battery facility can be very expensive, partly due to the hazardous nature of common battery types requiring special measures (electrolyte spill containment, etc.), and maintenance intensive due to the limited lifetime of batteries. A pumped hydro system can be also expensive, depending on natural topographical features that are available for operating two pools of water at different elevations. Another problem with pumped hydro systems can be their impact on fish and other life forms. This problem can be reduced if water source with little or no anadromous fish in it is used, such as Snake Lake, which is in proximity of the Snake Lake Mountain mentioned earlier as a potential site for wind installation. Instability is one of the biggest drawbacks of wind compared to some other sources (diesel, hydro). A chart summarizing basic solutions to the instability problem is shown in Figure Other Factors There are many other factors that need to be considered when evaluating wind as an alternative for electricity generation. Important factors to consider are for example: effect on birds and bats, land ownership, aesthetics, technology readiness for northern climates (icing issues, etc.), soils and their effect on foundation costs (can be significant), acceptance of the technology by local culture. Another thing to take into account is the fact that the current diesel generation system operates in winter as a combined heat and power plant. It means that the byproduct heat from the diesel generators is utilized for heating municipal buildings. If the diesel generation system is replaced by a wind system, this byproduct heat will not be available and the needed heat will have to be supplied from other sources. 2.5 References 1 Vaught D: Dillingham, Alaska Wind Resource Report Kanakanak Site, prepared for: Alaska Energy Authority, V3 Energy, Vaught D: Dillingham, Alaska Wind Resource Report Woodriver Road Site, prepared for: Alaska Energy Authority, V3 Energy, Szymoniak N, Devine M: Wind Resource Assessment for Dillingham, Alaska, prepared for: Alaska Energy Authority,

6 Problem Wind instability Energy storage Integration with other sources Solutions Battery Pumped hydro Diesel Hydro Potential problems Initial and operating costs Environmental impact Initial cost Environmental impact Cost of integration Not eliminating (only reducing) fossil fuel use Initial cost Environmental impact Figure 2.2 Basic solutions to the instability problem of wind

7 3. Conventional Hydro 3.1 Existence Even though water resources are abundant in Bristol Bay, the immediate Dillingham/Aleknagik area does not have lakes/rivers with topographical features suitable for conventional hydro power. However to the north and west in the extended Dillingham/Aleknagik area such topographical features do exist. 3.2 Quantity and Resulting Economics In the 1970 s and 1980 s the Dillingham/Aleknagik/Manokotak region was investigated for sites that had potential for hydropower. Two locations were selected and quantified in a greater detail Lake Elva and Grant Lake. This was done in two major studies completed in 1980 [1] and 1981 [2]. These past studies were then reviewed in 2009 [3] for feasibility using updated information. For each site, two alternatives were considered a storage system and a runof river system. A storage system has a big dam that allows a large storage of water, the outflow of which can be well controlled based on the electricity demand. Storage systems are generally more expensive than run of river systems, which only have a small dam with very limited storage, and the electricity generation pattern is mainly determined by the natural water flow pattern. The summary of annual generation and construction cost for each alternative, as estimated in the 2009 study [3], is shown in Table 3.1. Table 3.1 Estimates for generation and construction costs for Lake Elva and Grant Lake (source: [3]) Installed capacity Annual generation Construction cost Lake Elva storage 1 MW 5,746 MWh $64 million Lake Elva run of river 1.5 MW 4,833 MWh $48 million Grant Lake storage 1.7 MW 13,240 MWh $50 million Grant Lake run of river 3 MW 12,629 MWh $49 million Large portions of the total construction costs are due to the remote locations of Lake Elva and Grant Lake in relation to the Dillingham/Aleknagik grid, resulting in significant logistic difficulties and long transmission lines. The Lake Elva outlet is about 40 miles northwest of Dillingham and the Grant Lake outlet is about 50 miles north of Dillingham, both of which are in a protected area (Wood Tikchik State Park). The total production of Nushagak Electric in 2008 was nearly 19,000 MWh. It means that if all demand (or almost all demand) were to be covered by hydro, both Lake Elva and Grant Lake would have to be developed. Since run ofriver projects generate in response to available stream flows, there would be little or no generation in winter months. Therefore, in order to cover all demand (or almost all demand), at least one of the projects would have to be a storage project. In this case of covering almost all demand by hydro, from an economic perspective (based on Table 3.1), the best alternative would be Grant Lake storage and Lake Elva run of river alternatives with the total estimated cost of about $100 million. In this combination, Grant Lake generation would be controlled in such a way that would make up for the natural fluctuations of the Lake Elva generation. This Grant Lake storage and Lake Elva run of river scenario would result in the generation of about 18,000 MWh in an average year. Since the demand is currently slightly higher than that, some amount of electricity would have to be produced from other sources or the demand would have to be decreased via energy efficiency measures. 7

8 Another possibility might be to develop only one project in the storage version while supplying the rest of needed electricity from other renewable sources, such as wind. The output of the storage hydro would be controlled in such a way that would make up for the fluctuations of the renewable source. In this scenario, from an economic perspective, it would be best to develop Grant Lake storage hydro for $50 million. This would produce 13,240 MWh on an average year and the remaining approximately 6,000 MWh would have to be produced from a different source. 6,000 MWh per year corresponds to about 680 kw of average power. If that were to be supplied by wind, assuming 27% capacity factor (see Wind chapter), a wind installation of about 2.5 MW would be needed. Using the same formula as in the Wind chapter (Y = 24998X ), the cost of such an installation can be very roughly estimated to be about $5,400 per kw installed, i.e. the total cost of the 2.5 MW system would be about $13.5 million. The total cost of the hydro/wind system would be about $64 million based on these very broad estimates. The total cost might be reduced if one of the mountain sites with higher wind class were found to be viable since a smaller installation would then be sufficient due to a higher capacity factor (see Wind chapter). 3.3 Stability and Predictability The stability and predictability of conventional hydro systems depends on whether it is a storage or run of river alternative. The storage alternative provides a very stable energy source and a good control on an annual scale. The run of river alternative, due to limited storage capacity, is stable and controllable on a short term scale, but not on an annual scale. As mentioned earlier, run of river alternatives have little or no generation in winter. For both the storage and run of river alternatives, there is a certain unpredictability in the total amount of annual electricity generation. The data presented in Table 3.1 is the estimate for an average year, however, the total amount of generated electricity would be lower in a dry year and higher in a wet year. The 2009 review study [3] presents data for both dry and wet years. For example, the combination of Grant Lake storage and Lake Elva run of river would result in the generation of about 12,000 MWh in a dry year, 18,000 MWh in an average year, and about 20,000 MWh in a wet year. Thanks to a storage hydro system being able to store energy from summer till winter, in a year with production higher than the demand, the excess energy could be used for heating. The same is true for other combinations of systems using storage hydro, such as the earlier mentioned hydro/wind. 3.4 Other Factors Run of river hydro electric alternatives result in slightly modified streams where water flows are similar to the baseline hydrological conditions, however, storage hydro electric alternatives result in stream flows that are strongly altered from the baseline hydrological conditions. Therefore, for storage alternatives, their potential impacts on downstream aquatic ecosystems need to be evaluated. If the environmental impacts are too large and prohibit the use of the storage systems, a run of river hydro system alone may still be considered. However, it would have to be used in combination with another electricity generation system, in this case most likely diesel, that would be able to moderate the fluctuations. The summary of basic hydro alternatives is shown in Figure 3.1. Another important factor to mention is the fact that conventional hydro is a very mature technology compared to other renewable energy technologies, such as wind. Therefore, a conventional hydro system has a higher potential for a reliable operation. There are many other factors that need to be considered when evaluating hydro as an alternative for electricity generation. Important factors to consider include: land ownership and public use issues (both Lake Elva and Grant Lake project sites are inside the Wood Tikchik State Park), aesthetics, accumulation of silt (resulting in a reduced lifetime of the system), risk of dam failure, loss of by product heat from current diesel generators, acceptance of the project by local culture. 8

9 3.5 References 1 Reconnaissance Study of the Lake Elva and Other Hydroelectric Power Potentials in the Dillingham Area, prepared for: Alaska Power Authority, Robert W. Retherford Associates, Lake Elva Project Detailed Feasibility Analysis, prepared for: Alaska Power Authority, R. W. Beck and Associates, Review of Dillingham Area Hydro Projects, prepared for: Nushagak Electric and Telephone Cooperative, EES Consulting,

10 Hydro alternatives Hydro and its combinations with other sources Hydro storage + hydro run of river Hydro storage + wind Hydro run of river + diesel Potential problems Initial cost Altered water flow Initial cost Altered water flow Initial cost Not eliminating (only reducing) fossil fuel use Figure 3.1 Basic hydro alternatives

11 4. Solar 4.1 Existence Solar radiation is an existing resource in the Dillingham/Aleknagik area. 4.2 Quantity and Resulting Economics The National Renewable Energy Laboratory (NREL) published solar radiation data for various locations for a typical meteorological year (TMY). The published data are results of measurements combined with modeling. TMY data, version 3 (TMY3) includes solar radiation data for Dillingham. The following calculations use a vertical south facing orientation of photovoltaic panels as a baseline. Even though vertical orientation doesn t maximize the energy production potential, it provides a relatively maintenance free operation because of low susceptibility to snow and dust accumulation. Using TMY3 data for Dillingham, the average insolation on a vertical south facing surface is about 725 Btu/ft 2 day, assuming a full exposure with no obstructions. After a unit conversion (1 Btu/ft 2 day = W/m 2 ), this average insolation is 95 W/m 2, which is 9.5% of the standard insolation used for rating the power output of photovoltaic panels (1000 W/m2). It means that vertical south facing photovoltaic panels in Dillingham would operate with about a 9.5% capacity factor, it s because the power output of photovoltaic panels is approximately proportional to the insolation. Using this 9.5% capacity factor, and taking 2.1 MW as the approximate average load for the Nushagak Cooperative, a 22 MW photovoltaic installation would be needed to fully cover the load. Using $9 per watt installed as a typical cost of photovoltaic systems [2], the 22 MW installation would cost about $200 million. Since the vertical south facing configuration seems like a very expensive alternative, it is worthwhile to investigate the potential of a 2 axis tracking system, despite the issues with maintenance and snow accumulation mentioned earlier. For the latitude of the Dillingham region, based on NREL data [1], 2 axis tracking systems produce (assuming they are clear of snow) about 60% more energy than vertical south facing systems. Neglecting the fact that the cost per watt installed for a tracking system would be higher than for a fixed system, the total cost would be reduced from $200 million to $125 million, which is still much too expensive. It should be pointed out that these total costs for large installations covering all demand are presented here just for theoretical purposes because in order to cover all demand by solar, one would also need an energy storage facility, which can be very expensive and is not included in the above presented costs. However, one can use these data as a baseline to, for example, estimate the cost of smaller solar installations integrated with another system. 4.3 Stability and Predictability Solar radiation is an unstable resource with limited predictability. Basic solutions to these problems are similar to those discussed in the Wind chapter. 4.4 Other Factors There are many other factors that need to be considered when evaluating solar as an alternative for electricity generation. Important factors to consider are for example: space needs and land ownership, environmental impact of manufacturing (high energy needs, pollution), aesthetics, loss of by product heat from current diesel generators, acceptance of the project by local culture. 11

12 4.5 References 1 National Solar Radiation Data Base, Update: Typical Meteorological Year 3, /tmy3/, accessed 10/1/09. 2 Wiser, R, Bolinger, M, Cappers, P, Margolis, R: Letting the Sun Shine on Solar Costs: An Empirical Investigation of Photovoltaic Cost Trends in California, 2006, NREL Report No. TP

13 5. Biomass Wood, Fish Byproducts, Municipal Waste 5.1 Existence Wood, fish byproducts, and municipal waste are existing resources in the Dillingham/Aleknagik area. 5.2 Quantity and Resulting Economics Wood is a resource existing in a moderate amount in the Dillingham/Aleknagik area; however, no detailed studies have been done to determine the potential wood quantities that could be harvested in a sustainable way. A 2007 study suggested that at $ /gal diesel fuel prices, Dillingham is a potential candidate for an economically viable combined heat and power (CHP) system [1]. However, small wood fired CHP technology is generally considered pre commercial in the U.S., and requires more development to perform reliably [1]. Small, wood fired CHP demonstration systems in Alaska are planned by Chena Power (400 kw) and by the Alaska Cold Climate Housing Research Center (CCHRC) in Fairbanks (25 kw). The Chena plant, budgeted at $5 million, will use wood waste and waste paper to heat an organic working fluid, the vapors of which will pass through a turbine (Organic Rankine Cycle). The heat to electricity conversion is expected to be at the efficiency of about 20%. The CCHRC plant will use a wood gasifier and the first phase of the project is budgeted at $300,000 [1]. In Alaska, an estimated 13 million gallons of potential fish oil are returned to the ocean each year as fish industry processing waste [2], however no detailed study has been done for Dillingham specifically. In comparison, Nushagak Electric imports about 1.2 million gallons of diesel annually for electricity generation. A successful example of fish oil use is Unalaska, where fish oil/diesel blends have been used for power generation since 2001 [2]. Other groups, such as the University of Alaska Fairbanks, have been testing fish oil biodiesel (as opposed to raw fish oil) for power generation. Municipal waste can be converted to energy either via waste to energy incineration plants, or via harvesting landfill methane. Estimated 2200 lbs of municipal waste per person are generated each year in the U.S. [3]. This corresponds to about 5.3 million lbs for the Dillingham population of about 2,400. With the energy content of about 9 GJ per tonne [4], 5.3 million lbs of municipal waste per year corresponds to about 22 TJ of energy. Assuming that this is converted to electricity with a 20% efficiency, it will produce about 4.4 TJ of electricity per year, which (1 Wh = 3600 J) equals about 1,200 MWh per year. The total production of Nushagak Electric in 2008 was nearly 19,000 MWh, which means that the municipal waste would be able to cover about 6% of the demand. 5.3 Stability and Predictability Biomass energy is considered demand energy, which means it is typically available as needed. For raw fish oil and fish oil biodiesel obtained during the fishing season, the storage time might be limited by certain issues (oxidation, biological growth). 5.4 Other Factors A positive aspect related to using biomass for electricity generation is the availability of the byproduct heat, which in winter can be used to heat municipal buildings, similarly to how byproduct heat is presently used in the diesel generation system. One of the negative aspects of using biomass is the limited quantity. Diesel is the primary energy source for heating buildings in Dillingham and lot more diesel is used for heating than electricity generation. Since it is unlikely that enough biomass would be available to cover both heating and electricity needs of Dillingham/Aleknagik, the question that should be asked is: Wouldn t it be technologically easier and cheaper to use the available biomass to substitute 13

14 some of the diesel used for heating, as opposed to trying to substitute the diesel used for electricity generation? Technologies that use biomass for heating (such as wood fired boilers, waste oil burners) are typically lot more mature than technologies that use biomass for electricity production. There are many other factors that need to be considered when evaluating biomass as an alternative for electricity generation. Important factors to consider include: land ownership, air pollution, space for biomass storage, odors, labor, acceptance of the project by local culture. 5.5 References 1 A Guide for Alaskan Communities to Utilize Local Energy Resources, Alaska Energy Authority (AEA) and Alaska Center for Energy and Power (ACEP), Renewable Energy Atlas of Alaska A Guide to Alaska s Clean, Local and Inexhaustible Energy Resources, Alaska Energy Authority (AEA) and Renewable Energy Alaska Project (REAP), Turner W, Doty S: Energy Management Handbook, Sixth Edition, CRC Press, Boyle G: Renewable Energy Power for a Sustainable Future, Second Edition, Oxford,

15 6. Hydrokinetic/Tidal 6.1 Existence Hydrokinetic devices, as opposed to conventional hydro plants, do not require any dams; they are placed directly in river or tidal currents and powered by moving water. River currents in the immediate Dillingham/Aleknagik area don t reach significant speeds to be considered for hydrokinetic power. However, tidal currents seem to be significant enough to be considered for hydrokinetic power. 6.2 Quantity and Resulting Economics The potential for tidal current power generation in the Nushagak Bay was estimated to be 1.3 to 25 MW [1]. UAF Bristol Bay Campus is currently collecting more tidal current data using an Acoustic Doppler Current Profiler (ADCP). Insufficient tidal current data coupled with the fact that there is presently little third party testing of hydrokinetic devices pose high challenges to performing an economic estimate. As no economic analysis is available for the Dillingham area, it might be worthwhile to present data for Cairn Point located about two miles north of Anchorage in Knik Arm for comparison. At this location, the tidal currents average 2.0 knots with peaks up to 7.5 knots, and the Electric Power Research Institute (EPRI) estimated that a 17 MW plant could produce, assuming the use of government incentives, electricity for about 10 cents per kwh [2]. However, large uncertainties exist in this estimate. 6.3 Stability and Predictability Tidal currents are an unstable resource as the currents stop and change direction with every tide. However, tidal currents occur regularly, four times a day (with various magnitude), and can be predicted years in advance. The predictability of tidal energy makes it easier to integrate it with other systems, such as diesel. The predictability also makes it easier to design an energy storage system, which would be needed if all electrical demand were to be covered by tidal power. 6.4 Other Factors A very important factor to consider with hydrokinetic devices is that is a new technology and has been mostly used in demonstration projects, not in permanent installations. The first tidal current devices, six 34 kw turbines, were installed in the East River of New York City in late 2006 [2]. The world s first commercial scale tidal generator, a 1.2 MW underwater turbine, was installed in Northern Ireland in 2008 [1]. There are many environmental and technical challenges related to the deployment of hydrokinetic devices in Alaska that still need to be overcome. The main ones include the impact on aquatic life and resistance of the technology to debris and ice. 6.5 References 1 Renewable Energy Atlas of Alaska A Guide to Alaska s Clean, Local and Inexhaustible Energy Resources, Alaska Energy Authority (AEA) and Renewable Energy Alaska Project (REAP), A Guide for Alaskan Communities to Utilize Local Energy Resources, Alaska Energy Authority (AEA) and Alaska Center for Energy and Power (ACEP),

16 7. Geothermal 7.1 Existence The Dillingham/Aleknagik area is not known to have a shallow geothermal resource [1]. 7.2 Quantity and Resulting Economics Usable heat exists within drillable depths in most areas of the earth, the question that needs to be answered, though, is how economical it would be to transfer the heat to the surface to be used for a geothermal plant. Deep explorations need to be done to answer that question, which can be very expensive. For example, Naknek area does not have a known shallow geothermal resource, and currently, Naknek Electric Association is drilling an exploratory drilling well to reach from 8,000 to as much as 12,000 feet deep [2] in a $12 million drilling program [1]. 7.3 Stability and Predictability If developed and operated right, geothermal energy is a relatively stable long term resource. An important problem to mention is that in almost all geothermal installations in the world, heat is being removed faster than it is replaced, which means the available output power is gradually dropping [3]. 7.4 Other Factors There are many other factors that need to be considered when evaluating geothermal energy as an alternative for electricity generation. Important factors to consider include: potential for simultaneous use for other purposes (heating, food production in greenhouses, etc.), land ownership, acceptance of the project by local culture. 7.5 References 1 Renewable Energy Atlas of Alaska A Guide to Alaska s Clean, Local and Inexhaustible Energy Resources, Alaska Energy Authority (AEA) and Renewable Energy Alaska Project (REAP), Legislative Update from Representative Bryce Edgmon: Naknek Electric Breaks Ground in a Big Way on Geothermal Exploration, Volume 3, Issue 19, Boyle G: Renewable Energy Power for a Sustainable Future, Second Edition, Oxford, Acknowledgments I would like to acknowledge the following people for cooperating on this study and providing valuable information: Frank Corbin with NETC, Michael Favors with NETC, Mark Newson with BBAHC, James Jensen with AEA, Kat Keith with ACEP, Todd Radenbaugh with UAF BBC. 16