- Email: [email protected]
Hydrogen energy systems
Hydrogen
HYDROGEN ENERGY SYSTEMS
Concepts and practical applications
In an ideal world we might envisage a future where electricity, renewable energy sources alone to electrolyse heat and motive power are derived from renewable energy water and break it down into its components sources. Hydrogen could be a key player in certain applications of hydrogen and oxygen. The hydrogen component can be stored until needed to produce in this future world as an energy storage medium. Daniel Berndt, electricity, heat or motive power. Carter Burgess, Inc. USA provides an overview of some of the technologies and processes that might play a part in a future Hydrogen storage systems The density of hydrogen is so low at ambient hydrogen economy.
B
ecause of issues such as energy security and global warming, numerous organizations and governments have contributed vast resources towards the development of what has been coined the hydrogen economy. Basically the hydrogen economy is where the petroleum infrastructure is replaced by a hydrogen infrastructure. The oil companies themselves have seen the writing on the wall and are also contributing resources towards the development of a hydrogen infrastructure.
A key question remains: where will the hydrogen come from? Wind, solar, nuclear, hydroelectric, wave & tidal, geothermal, biomass and petrochemical products, are all energy sources that can be used for the generation of hydrogen (Figures 1 & 2). Many proponents of the hydrogen economy generally discount petroleum products and nuclear energy for the generation of hydrogen due to environmental and sociological concerns. In a hydrogen economy, an ideal concept would be to use electricity from
temperatures and pressures that it is not practical to store it under these conditions. Ambient temperatures are well above the hydrogen critical temperature so hydrogen can’t be liquified like propane. Selecting a storage system can be one of the most challenging tasks in designing a hydrogen energy system. There are several different ways to store hydrogen. It can be stored as a compressed gas the way natural gas is stored, it can be stored at temperatures low enough to liquefy the gas, or it can be absorbed into a solid. Since space is typically not a premium for fixed installations, compressed gas storage is the most appropriate hydrogen storage method for user based hydrogen energy storage systems.
End user energy conversion There is also a number of ways hydrogen can be used once it has been produced and stored. Hydrogen can be used to make
Figure 1: Solar to Hydrogen Facility, Neunburg vorn Wald, Germany. Photo: EON
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Further information Contact: Daniel W. Berndt, P.E., C.E.M., Senior Engineer, Carter Burgess, Inc., 777 Main Street, Suite 2900, Fort Worth, TX 76102, USA. Tel: +1(817) 2228561; Fax: +1 (817) 222-8550; [email protected]
1471 0846/04 ©2004 Elsevier Ltd. All rights reserved.
Hydrogen
electricity through fuel cells, engine generator sets or gas fired steam turbines. Hydrogen fired engines and steam turbines can also be used to perform work, such as in automobiles, trains, boats and airplanes. And hydrogen can also be used in devices that make steam, hot water or heat just like natural gas. The primary goal of the user based hydrogen energy storage system, as discussed in this article, is storing energy acquired through renewable energy sources and using that energy to create electricity when economically practical. Although the other uses are not discussed here, careful consideration of the alternative uses of hydrogen could identify additional significant cost savings for the project. For example, when coupling a hydrogen energy storage system with a solar thermal power plant, it is possible to use the waste heat from a thermal engine or a fuel cell in a feed water heater. Since this waste heat would be used in the production of electricity, the overall electrical efficiency of the hydrogen energy storage system is increased during peak demand periods. Hydrogen fuel cells Fuel cells combine hydrogen and oxygen to make water and produce electricity in the process. Only 40% of the energy released in the recombining process is used to make electricity. The other 60% is lost as waste heat. With co-generation, as much as 90% of the energy released can be recovered. Fuel cells need to warm up to be able to produce their rated capacity. This warm up time can make them an inappropriate application for on demand power. Fuel cells require much more space than thermal engines for the same given capacity. Despite the limitations of fuel cells, most proponents of hydrogen energy storage systems favour them as the end user energy conversion devise of choice. This area, however, is not the main focus of this article. Hydrogen thermal engines (naturally aspirated) There are engine generators being manufactured specifically designed to run on hydrogen and there are hydrogen conversion kits for existing internal combustion engines. Hydrogen engine generator sets function the
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Figure 2: Aerial view of a solar-hydrogen facility. Photo: EON
same as natural gas engine generator sets and have similar operating characteristics. The efficiency of hydrogen engine-generator sets range from 30 to 35 percent without cogeneration. HyOx Technology There is a different way to use hydrogen in a thermal engine. A way that shows great potential but has not received much press attention as yet is HyOx Technology. In the electrolysis process in the conventional hydrogen energy storage system, the oxygen generated is either vented to the atmosphere or directed to other uses, and new treated water has to be continuously fed to the electrolyzer to make up the water used to make hydrogen. What if instead of wasting off the oxygen it was fed back into the system to reproduce water at the end user energy conversion device? Make-up water would no longer be required, but what would be the characteristics of oxygen aspirated hydrogen engines and heating devices? The engines that run on HyOx have tremendous potential but only a limited amount of research is being done in this field. To evaluate the potential of HyOx engines a comparison needs to be made to naturally aspirated engines. Although this comparison centres on internal combustion engines, the comparison, in many ways, is applicable to other types of fuel burning devices. This includes devices such as turbines, boilers, furnaces, and heaters. In regards to engine emissions, the exhaust of a naturally aspirated hydrocarbon engine produces mostly nitrogen, carbon dioxide, H2O
in the form of steam, and oxides of nitrogen. Since the air that the engine “breathes” is mostly nitrogen, the exhaust coming from the engine is also mostly nitrogen. The exhaust of a naturally aspirated hydrogen engine produces nitrogen, H2O again in the form of steam, and oxides of nitrogen. The HyOx engine is designed to exhaust only H2O. Thermal efficiency of an engine is basically a function of combustion temperatures and pressures and exhaust temperatures and pressures. If the combustion temperature and pressure are allowed to increase, the efficiency of the engine increases. Inversely if it is possible to reduce the exhaust temperature and pressure the efficiency also increases. Some of the ways engine manufacturers reduce oxides of nitrogen emissions in engines is to reduce compression ratios, retard ignition timing or recycle exhaust gases. All of these techniques reduce combustion temperature and pressure and therefore reduce engine efficiency. Since oxides of nitrogen are not an issue with the HyOx engine the only things limiting the combustion temperature and pressure of
Hydrogen, Oxygen, Nitrogen storage tank farm
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Hydrogen
Table 1: Total Renewable Project Costs System Component
Est. Cost
3500 kW STPP
$12,250,000
Hydrogen Energy Storage Electrolyzers (3,500kW) Hydrogen Storage (1,950 cu.ft.) Oxygen Storage (975 cu.ft.) Water Storage (125,000 gal.) Engine Generators (4,000 kVA) Miscellaneous Project Total
the HyOx engine are the materials of the engine and how those materials are put together. A naturally aspirated engine has to exhaust its combustion products directly into the atmosphere. In doing so the engine has to work against the backpressure imposed on it by the atmosphere. The H2O exhaust of the oxygen aspirated hydrogen engine can be condensed into water creating a negative pressure at the exhaust and further increasing the efficiency and power. HyOx engines have theoretical efficiencies in excess of 90%. Practical efficiencies of the HyOx engines can be in excess 70%. By contrast naturally aspirated engines achieve efficiencies of 30% to 35%. Thermal engine power is a function of oxygen volumetric flow percentage, efficiency and manifold pressure. Oxygen volumetric flow percentage of a naturally aspirated hydrogen engine is 14% where the oxygen volumetric flow percentage of a HyOx engine is 33%. Because of the high oxygen volumetric percentage and the higher manifold pressures available from the hydrogen and oxygen tanks, a high
Pressure-Type Alkaline Electrolyzer
50 reFOCUS
November/December 2004
$1,050,000 $1,200,000 $600,000 $200,000 $800,000 $1,000,000 $17,100,000
efficiency HyOx Engine operating at 2 atmospheres could produce over six times as much power as a naturally aspirated engine. In regards to engine noise, the exhaust of naturally aspirated engines must be muffled, which also reduces engine efficiency and power. With the HyOx engine, the exhaust can be condensed, eliminating exhaust noise. As mentioned previously, condensing the exhaust gases also increases power and efficiency of the engine (Figure 3).
Practical applications The practical application of hydrogen energy installations to obtain viable energy cost savings is dependent on careful consideration of current economic conditions. Installations that may be able to achieve viable energy cost savings include renewable energy installations in remote or undeveloped areas and installations where there are high “on-peak” energy costs. A typical automated merchandise distribution centre in the United States may
range from 500,000 to 1,000,000 square feet. Many of these facilities are fully air-conditioned or have refrigerated storage. The energy budgets for these types of facilities run into the millions of dollars per year. Alternative forms of energy often look attractive for these types of facilities. Depending on the conventional energy cost structure and the project location, it may be possible to reduce the overall energy costs by providing a renewable energy system coupled with a hydrogen energy storage system. This example is intended to show techniques for identifying the economic viability of a renewable energy project, but is not intended to show viability of any particular project. The goal of this particular example project is to provide power generation, from renewable energy generated on site, during onpeak rate structure hours. The goal of the hydrogen energy storage system is to time shift solar energy availability from all offpeak rate hours for an entire week, including weekend hours, to on-peak hours. The assumptions of the project are that it is located in California and that it will use Southern California Edison electricity rates. The renewable energy system will only provide power during on-peak hours in summer months and mid-peak hours in non-summer months. The facility has a maximum 7000 kW on-peak electricity demand and has a yearly electricity demand during the hours specified of 10 800 MWhr. The renewable energy system for this example project will have a solar trough solar thermal power plant, a electrolysed hydrogen generation system, 5000 psi pressurized oxygen and hydrogen storage, and high efficiency HyOx engines. There are 84 available solar hours per week, but the utility rate structure identifies only 30 on-peak rate hours per week. A renewable energy installation with no storage will have to have a peak capacity of 7000 kW. If the assumption is made that the energy storage systems have no efficiency losses, the whole 84 available solar hours could be used creating a solar field capacity requirement of 2500 kW. With a more realistic 60% efficient storage system, the solar field capacity would have to have a 3365 kW peak capacity to provide the required 7000 kW capacity during onpeak hours.
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Hydrogen
Based on a cost per kilowatt for solar trough solar thermal power plants of $3500, the renewable energy power plant would cost $24,500,000 with no storage and $11,777,500 with a 60% efficient energy storage system. This analysis illustrates the importance of the hydrogen energy storage system efficiency. A small change in the efficiency of the energy storage system could easily make or break a renewable energy project. A 3500 kW solar thermal power plant at an estimated cost of $12,250,000 is planned for this example project. The hydrogen energy storage system will include electrolyzers rated at a peak capacity of 3500 kW, 1950 cubic feet of hydrogen storage, 975 cubic feet of oxygen storage, 125 000 gallons of water storage, HyOx engine-generators rated at a peak capacity of 4000 KW and associated structures and hardware for a cost of approximately $4,850,000. The combined cost of the power plant and the energy storage system comes to around $17,100,000. (Tables 1 & 2) Assuming a 12 percent cost of capital and using 10,800 Megawatt-hours of energy production per year, the cost of capital portion of the project levilised energy cost (LEC) comes to $190/MWh. There is no fuel cost component of the LEC for renewable energy projects but it is assumed that the operational and maintenance costs are $10/MWh. This gives a total LEC for the project of $200/MWh. It is estimated that the average cost for commercial electricity for the hours of operation identified in the assumptions for this project will be
Table 2: Practical Example Initial Assumptions Category
Assumption
Electric Utility Rates Summer months operation Non-Summer Months Peak Electricity Demand Annual Electricity Consumption
Southern California Edison On-Peak hours only Mid-Peak hours only 7000 kW 10,800 MWh/yr
$229/MWh. Calculating the difference between the LEC of the example project and cost of the commercial electricity and multiplying that difference by the 10,800 MWh/yr of power generation gives a $313,200/yr energy cost saving. Dividing the project cost of $17,100,000 by the average commercial electricity cost of $229/MWh and the renewable energy power plant generation of 10,800MWh/yr yields a simple pay back period of 6.9 years.
HyOx vs. Gasoline In most cases when HyOx is generated from renewable energy, the current cost of renewable energy is too high to make HyOx cost competitive with gasoline. But there are cases where certain types of renewable energy can produce HyOx at a cost that is very competitive with gasoline. One of those cases happens to be wind energy. The maximum allowable LEC for a HyOx that costs less than $1.45/gal gasoline energy (assuming that the HyOx engine is twice as efficient as the naturally aspirated engine) is $78/MWh. Since the LEC for wind turbine energy can be as low as $46/MWh, there is potential for HyOx ener-
gy to be near parity with the cost of gasoline. With careful control of HyOx storage and distribution costs and HyOx generation efficiencies competitive fueling of vehicles using renewable energy could be achieved. As diminishing oil supplies and environmental controls drive up the cost of fossil fuels the economic viability of HyOx technology will only improve.
Hydrogen economy Proponents of the hydrogen economy affirm that, in order for the hydrogen economy to become a reality, hydrogen energy has to be successful in niche markets first. Perhaps hydrogen energy storage and HyOx generation coupled with wind energy will be the catalysts that bring about the transformation to the hydrogen economy. A hydrogen economy based on renewable energy sources would provide energy security for the World not just for the next decade or the next century, but, for the next millennium. Or as Buzz Lightyear of Disney’s Toy Story fame would say, “To Infinity and Beyond”.
Hydrogen Storage
Renewable Energy
Electricity Generation
Electrolyzer
Electricity Generation
Energy Consumption
Oxygen Storage
Water Storage
Figure 3: HyOx energy system diagram
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November/December 2004
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HYDROGEN ENERGY SYSTEMS
Concepts and practical applications
In an ideal world we might envisage a future where electricity, renewable energy sources alone to electrolyse heat and motive power are derived from renewable energy water and break it down into its components sources. Hydrogen could be a key player in certain applications of hydrogen and oxygen. The hydrogen component can be stored until needed to produce in this future world as an energy storage medium. Daniel Berndt, electricity, heat or motive power. Carter Burgess, Inc. USA provides an overview of some of the technologies and processes that might play a part in a future Hydrogen storage systems The density of hydrogen is so low at ambient hydrogen economy.
B
ecause of issues such as energy security and global warming, numerous organizations and governments have contributed vast resources towards the development of what has been coined the hydrogen economy. Basically the hydrogen economy is where the petroleum infrastructure is replaced by a hydrogen infrastructure. The oil companies themselves have seen the writing on the wall and are also contributing resources towards the development of a hydrogen infrastructure.
A key question remains: where will the hydrogen come from? Wind, solar, nuclear, hydroelectric, wave & tidal, geothermal, biomass and petrochemical products, are all energy sources that can be used for the generation of hydrogen (Figures 1 & 2). Many proponents of the hydrogen economy generally discount petroleum products and nuclear energy for the generation of hydrogen due to environmental and sociological concerns. In a hydrogen economy, an ideal concept would be to use electricity from
temperatures and pressures that it is not practical to store it under these conditions. Ambient temperatures are well above the hydrogen critical temperature so hydrogen can’t be liquified like propane. Selecting a storage system can be one of the most challenging tasks in designing a hydrogen energy system. There are several different ways to store hydrogen. It can be stored as a compressed gas the way natural gas is stored, it can be stored at temperatures low enough to liquefy the gas, or it can be absorbed into a solid. Since space is typically not a premium for fixed installations, compressed gas storage is the most appropriate hydrogen storage method for user based hydrogen energy storage systems.
End user energy conversion There is also a number of ways hydrogen can be used once it has been produced and stored. Hydrogen can be used to make
Figure 1: Solar to Hydrogen Facility, Neunburg vorn Wald, Germany. Photo: EON
48 reFOCUS
November/December 2004
Further information Contact: Daniel W. Berndt, P.E., C.E.M., Senior Engineer, Carter Burgess, Inc., 777 Main Street, Suite 2900, Fort Worth, TX 76102, USA. Tel: +1(817) 2228561; Fax: +1 (817) 222-8550; [email protected]
1471 0846/04 ©2004 Elsevier Ltd. All rights reserved.
Hydrogen
electricity through fuel cells, engine generator sets or gas fired steam turbines. Hydrogen fired engines and steam turbines can also be used to perform work, such as in automobiles, trains, boats and airplanes. And hydrogen can also be used in devices that make steam, hot water or heat just like natural gas. The primary goal of the user based hydrogen energy storage system, as discussed in this article, is storing energy acquired through renewable energy sources and using that energy to create electricity when economically practical. Although the other uses are not discussed here, careful consideration of the alternative uses of hydrogen could identify additional significant cost savings for the project. For example, when coupling a hydrogen energy storage system with a solar thermal power plant, it is possible to use the waste heat from a thermal engine or a fuel cell in a feed water heater. Since this waste heat would be used in the production of electricity, the overall electrical efficiency of the hydrogen energy storage system is increased during peak demand periods. Hydrogen fuel cells Fuel cells combine hydrogen and oxygen to make water and produce electricity in the process. Only 40% of the energy released in the recombining process is used to make electricity. The other 60% is lost as waste heat. With co-generation, as much as 90% of the energy released can be recovered. Fuel cells need to warm up to be able to produce their rated capacity. This warm up time can make them an inappropriate application for on demand power. Fuel cells require much more space than thermal engines for the same given capacity. Despite the limitations of fuel cells, most proponents of hydrogen energy storage systems favour them as the end user energy conversion devise of choice. This area, however, is not the main focus of this article. Hydrogen thermal engines (naturally aspirated) There are engine generators being manufactured specifically designed to run on hydrogen and there are hydrogen conversion kits for existing internal combustion engines. Hydrogen engine generator sets function the
www.re-focus.net
Figure 2: Aerial view of a solar-hydrogen facility. Photo: EON
same as natural gas engine generator sets and have similar operating characteristics. The efficiency of hydrogen engine-generator sets range from 30 to 35 percent without cogeneration. HyOx Technology There is a different way to use hydrogen in a thermal engine. A way that shows great potential but has not received much press attention as yet is HyOx Technology. In the electrolysis process in the conventional hydrogen energy storage system, the oxygen generated is either vented to the atmosphere or directed to other uses, and new treated water has to be continuously fed to the electrolyzer to make up the water used to make hydrogen. What if instead of wasting off the oxygen it was fed back into the system to reproduce water at the end user energy conversion device? Make-up water would no longer be required, but what would be the characteristics of oxygen aspirated hydrogen engines and heating devices? The engines that run on HyOx have tremendous potential but only a limited amount of research is being done in this field. To evaluate the potential of HyOx engines a comparison needs to be made to naturally aspirated engines. Although this comparison centres on internal combustion engines, the comparison, in many ways, is applicable to other types of fuel burning devices. This includes devices such as turbines, boilers, furnaces, and heaters. In regards to engine emissions, the exhaust of a naturally aspirated hydrocarbon engine produces mostly nitrogen, carbon dioxide, H2O
in the form of steam, and oxides of nitrogen. Since the air that the engine “breathes” is mostly nitrogen, the exhaust coming from the engine is also mostly nitrogen. The exhaust of a naturally aspirated hydrogen engine produces nitrogen, H2O again in the form of steam, and oxides of nitrogen. The HyOx engine is designed to exhaust only H2O. Thermal efficiency of an engine is basically a function of combustion temperatures and pressures and exhaust temperatures and pressures. If the combustion temperature and pressure are allowed to increase, the efficiency of the engine increases. Inversely if it is possible to reduce the exhaust temperature and pressure the efficiency also increases. Some of the ways engine manufacturers reduce oxides of nitrogen emissions in engines is to reduce compression ratios, retard ignition timing or recycle exhaust gases. All of these techniques reduce combustion temperature and pressure and therefore reduce engine efficiency. Since oxides of nitrogen are not an issue with the HyOx engine the only things limiting the combustion temperature and pressure of
Hydrogen, Oxygen, Nitrogen storage tank farm
November/December 2004
reFOCUS 49
Hydrogen
Table 1: Total Renewable Project Costs System Component
Est. Cost
3500 kW STPP
$12,250,000
Hydrogen Energy Storage Electrolyzers (3,500kW) Hydrogen Storage (1,950 cu.ft.) Oxygen Storage (975 cu.ft.) Water Storage (125,000 gal.) Engine Generators (4,000 kVA) Miscellaneous Project Total
the HyOx engine are the materials of the engine and how those materials are put together. A naturally aspirated engine has to exhaust its combustion products directly into the atmosphere. In doing so the engine has to work against the backpressure imposed on it by the atmosphere. The H2O exhaust of the oxygen aspirated hydrogen engine can be condensed into water creating a negative pressure at the exhaust and further increasing the efficiency and power. HyOx engines have theoretical efficiencies in excess of 90%. Practical efficiencies of the HyOx engines can be in excess 70%. By contrast naturally aspirated engines achieve efficiencies of 30% to 35%. Thermal engine power is a function of oxygen volumetric flow percentage, efficiency and manifold pressure. Oxygen volumetric flow percentage of a naturally aspirated hydrogen engine is 14% where the oxygen volumetric flow percentage of a HyOx engine is 33%. Because of the high oxygen volumetric percentage and the higher manifold pressures available from the hydrogen and oxygen tanks, a high
Pressure-Type Alkaline Electrolyzer
50 reFOCUS
November/December 2004
$1,050,000 $1,200,000 $600,000 $200,000 $800,000 $1,000,000 $17,100,000
efficiency HyOx Engine operating at 2 atmospheres could produce over six times as much power as a naturally aspirated engine. In regards to engine noise, the exhaust of naturally aspirated engines must be muffled, which also reduces engine efficiency and power. With the HyOx engine, the exhaust can be condensed, eliminating exhaust noise. As mentioned previously, condensing the exhaust gases also increases power and efficiency of the engine (Figure 3).
Practical applications The practical application of hydrogen energy installations to obtain viable energy cost savings is dependent on careful consideration of current economic conditions. Installations that may be able to achieve viable energy cost savings include renewable energy installations in remote or undeveloped areas and installations where there are high “on-peak” energy costs. A typical automated merchandise distribution centre in the United States may
range from 500,000 to 1,000,000 square feet. Many of these facilities are fully air-conditioned or have refrigerated storage. The energy budgets for these types of facilities run into the millions of dollars per year. Alternative forms of energy often look attractive for these types of facilities. Depending on the conventional energy cost structure and the project location, it may be possible to reduce the overall energy costs by providing a renewable energy system coupled with a hydrogen energy storage system. This example is intended to show techniques for identifying the economic viability of a renewable energy project, but is not intended to show viability of any particular project. The goal of this particular example project is to provide power generation, from renewable energy generated on site, during onpeak rate structure hours. The goal of the hydrogen energy storage system is to time shift solar energy availability from all offpeak rate hours for an entire week, including weekend hours, to on-peak hours. The assumptions of the project are that it is located in California and that it will use Southern California Edison electricity rates. The renewable energy system will only provide power during on-peak hours in summer months and mid-peak hours in non-summer months. The facility has a maximum 7000 kW on-peak electricity demand and has a yearly electricity demand during the hours specified of 10 800 MWhr. The renewable energy system for this example project will have a solar trough solar thermal power plant, a electrolysed hydrogen generation system, 5000 psi pressurized oxygen and hydrogen storage, and high efficiency HyOx engines. There are 84 available solar hours per week, but the utility rate structure identifies only 30 on-peak rate hours per week. A renewable energy installation with no storage will have to have a peak capacity of 7000 kW. If the assumption is made that the energy storage systems have no efficiency losses, the whole 84 available solar hours could be used creating a solar field capacity requirement of 2500 kW. With a more realistic 60% efficient storage system, the solar field capacity would have to have a 3365 kW peak capacity to provide the required 7000 kW capacity during onpeak hours.
www.re-focus.net
Hydrogen
Based on a cost per kilowatt for solar trough solar thermal power plants of $3500, the renewable energy power plant would cost $24,500,000 with no storage and $11,777,500 with a 60% efficient energy storage system. This analysis illustrates the importance of the hydrogen energy storage system efficiency. A small change in the efficiency of the energy storage system could easily make or break a renewable energy project. A 3500 kW solar thermal power plant at an estimated cost of $12,250,000 is planned for this example project. The hydrogen energy storage system will include electrolyzers rated at a peak capacity of 3500 kW, 1950 cubic feet of hydrogen storage, 975 cubic feet of oxygen storage, 125 000 gallons of water storage, HyOx engine-generators rated at a peak capacity of 4000 KW and associated structures and hardware for a cost of approximately $4,850,000. The combined cost of the power plant and the energy storage system comes to around $17,100,000. (Tables 1 & 2) Assuming a 12 percent cost of capital and using 10,800 Megawatt-hours of energy production per year, the cost of capital portion of the project levilised energy cost (LEC) comes to $190/MWh. There is no fuel cost component of the LEC for renewable energy projects but it is assumed that the operational and maintenance costs are $10/MWh. This gives a total LEC for the project of $200/MWh. It is estimated that the average cost for commercial electricity for the hours of operation identified in the assumptions for this project will be
Table 2: Practical Example Initial Assumptions Category
Assumption
Electric Utility Rates Summer months operation Non-Summer Months Peak Electricity Demand Annual Electricity Consumption
Southern California Edison On-Peak hours only Mid-Peak hours only 7000 kW 10,800 MWh/yr
$229/MWh. Calculating the difference between the LEC of the example project and cost of the commercial electricity and multiplying that difference by the 10,800 MWh/yr of power generation gives a $313,200/yr energy cost saving. Dividing the project cost of $17,100,000 by the average commercial electricity cost of $229/MWh and the renewable energy power plant generation of 10,800MWh/yr yields a simple pay back period of 6.9 years.
HyOx vs. Gasoline In most cases when HyOx is generated from renewable energy, the current cost of renewable energy is too high to make HyOx cost competitive with gasoline. But there are cases where certain types of renewable energy can produce HyOx at a cost that is very competitive with gasoline. One of those cases happens to be wind energy. The maximum allowable LEC for a HyOx that costs less than $1.45/gal gasoline energy (assuming that the HyOx engine is twice as efficient as the naturally aspirated engine) is $78/MWh. Since the LEC for wind turbine energy can be as low as $46/MWh, there is potential for HyOx ener-
gy to be near parity with the cost of gasoline. With careful control of HyOx storage and distribution costs and HyOx generation efficiencies competitive fueling of vehicles using renewable energy could be achieved. As diminishing oil supplies and environmental controls drive up the cost of fossil fuels the economic viability of HyOx technology will only improve.
Hydrogen economy Proponents of the hydrogen economy affirm that, in order for the hydrogen economy to become a reality, hydrogen energy has to be successful in niche markets first. Perhaps hydrogen energy storage and HyOx generation coupled with wind energy will be the catalysts that bring about the transformation to the hydrogen economy. A hydrogen economy based on renewable energy sources would provide energy security for the World not just for the next decade or the next century, but, for the next millennium. Or as Buzz Lightyear of Disney’s Toy Story fame would say, “To Infinity and Beyond”.
Hydrogen Storage
Renewable Energy
Electricity Generation
Electrolyzer
Electricity Generation
Energy Consumption
Oxygen Storage
Water Storage
Figure 3: HyOx energy system diagram
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November/December 2004
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