A Discussion of PEM Fuel Cell Systems and Distributed Generation

Transcription

1 A Discussion of PEM Fuel Cell Systems and Distributed Generation Jeffrey D. Glandt, M. Eng. Principal Engineer, Solutions Engineering May 2011 The information contained in this document is derived from selected public sources. Ballard does not guarantee the accuracy or completeness of the information and nothing shall be construed as a representation of such a guarantee. Ballard accepts no responsibility for any liability arising from use of this document or its contents. Nothing in this document constitutes or should be construed to constitute investment advice. Any opinions presented are subject to change without notice.

2 THE TREND TOWARD DISTRIBUTED GENERATION The global grid-connected electricity market grows in capacity by approximately one hundred gigawatts annually 1. In the past, this demand would have been met through the continued development of centralized power plants, with extensive transmission lines to distribute the power. Power distribution based on this centralized grid structure features high emissions and poor efficiency, as a result of mainly fossil-based primary energy sources and power-line losses during transmission. Now, with concerns regarding the shortage of fossil fuels, global warming due to greenhouse gas emissions, and energy security, users are turning to alternative energy sources to meet this growing demand for electricity. Distributed generation using renewable energy sources is seen as the best means of meeting such increased demand while simultaneously increasing efficiency, reducing emissions and reducing the burden on the existing grid. Smaller scale power plants (from the low kilowatts to multi-megawatts) are located closer to the point of demand, allowing users to control their production and demand, and improving efficiency by reducing losses through transmission and distribution. Energy security is enhanced through lessened dependence on a single source of power, with diversified mix of sources dispersed throughout a region. In addition, distributed power generation provides more opportunities for cogeneration, with heat generated by power plants captured and used for industrial and district heating applications. This reduces the total amount of energy required for electricity and heating purposes, improving overall system efficiency. FUEL CELLS FOR DISTRIBUTED GENERATION Fuel cell and hydrogen technology are important components of the evolving distributed power generation landscape. Fuel cells, combined with hydrogen storage, have the potential to save energy and reduce emissions when compared to other conventional systems. Fuel cell systems are two to three times more efficient than internal combustion engines and can be scaled in power output to match the fuel supply. Fuel cells also maintain a very high efficiency at all power levels whereas diesel and gas turbine generators have very poor efficiency when turned down in power level. When operated on pure hydrogen, fuel cells do not emit carbon dioxide, carbon monoxide, particulate matter, or other emissions at the point of use. This zero emission technology can greatly facilitate siting relative to conventional distributed generation power systems. In addition, fuel cells are quieter, more reliable and have lower maintenance costs than most technologies used for distributed generation. Proton exchange membrane (PEM) fuel cells, in particular, have the unique ability to meet the power demands of distributed generation. In comparison to other types of fuel cells, PEM fuel cells are one of the few capable of providing both base load power and load following capabilities. As a result of many years of focused development for transportation applications, PEM fuel cells feature the capacity for fast startup and dynamic operation. This allows the systems to closely follow electricity demand, further heightening efficiency. A Discussion of PEM Fuel Cell Systems and Distributed Generation 1

3 MARKET APPLICATIONS Market analysis has identified potential distributed generation applications for PEM fuel cell systems, including: Industries generating by-product hydrogen - the system provides base load power, using by-product hydrogen to produce electricity that is either sold back to the grid through the electricity utility or used to offset power demand on site. Remote communities - off-grid communities in remote locations can be served through a combination of hydrogen production using renewable energy and fuel cell power, displacing diesel generator noise and emissions. Renewable energy producers - when coupled with a wind or PV system, the fuel cell system can provide large-scale energy storage using hydrogen produced during offpeak times. Industrial Processes Generating By-Product Hydrogen Certain chemical processes, such as chlorine and sodium chlorate production, generate hydrogen as a by-product. In cases where this by-product hydrogen is flared (vented) or burned for its heating value, the chemical producer is failing to maximize the full value of this hydrogen. There is an opportunity to produce clean, zero-emission electricity that is either sold back to the grid, through the electricity utility, or used to offset power demand on site. Because the hydrogen is a by-product of another process, the economics of using the hydrogen with a PEM fuel cell system is quite attractive. For example, a one-megawatt system utilizing hydrogen from a nonrenewable source will qualify under California s Self-Generation Incentive Program (SGIP) for funding of $2,500 per kilowatt. Federal incentives of up to 30% of capital expenditures are also available. These incentives, coupled with the high base electricity rate of $0.12/kWh and a hydrogen opportunity cost of $0.60/kg (natural gas equivalent lower heating value price), drive an internal rate of return of approximately 20% over fifteen years. ASSUMPTIONS:* Power output 1 MW Hydrogen source By-product hydrogen California s Self-Generation Incentive $2500/kW up to 1 MW Program (SGIP) Federal stimulus 30% of capital expenditures, less SGIP grant Kilowatt hours generated 8,320 MW hours per year, per MW installed Amount of H2 consumed 63kg/hour Up-time >95% *California s SGIP requires that power be used on-site, not sold to the grid. An estimated 1,000 MW of this by-product hydrogen is available globally, sufficient to power up to one million homes a year. In addition, industries that utilize hydrogen in their processes, such as refineries and ammonia production plants, could capture excess hydrogen that is flared or vented for pressure control and use it instead in a PEM fuel cell system for onsite power generation. A Discussion of PEM Fuel Cell Systems and Distributed Generation 2

4 In addition, approximately 700 miles of hydrogen pipelines are currently operating in the United States 2 and over 900 miles in Europe 3. Owned by merchant hydrogen producers, these pipelines are located where large hydrogen users, such as petroleum refineries and chemical plants, are concentrated (for example, in the Gulf Coast region). Other industries located near hydrogen pipelines can take advantage of easy access to this hydrogen, installing a PEM fuel cell system to generate lower cost power during times of peak demand and high electricity prices. Renewable Power Systems for Remote Communities Around the world there are many remote communities not connected to a large, stable electrical grid. Canada, for example, has approximately 300 of these remote communities 4 and it is estimated there are up to 4,000 such communities globally. Typically, these small, isolated communities, having (at best) unstable grid connectivity, generate much or all of their electricity using diesel generators. While diesel generators have a relatively favourable capital cost, they have exceptionally high operating costs due to their low efficiency combined with the high cost of transporting diesel fuel to these remote sites, often under very difficult circumstances. Furthermore, diesel fuel prices are expected to increase further in the coming years. In addition, diesel generators emit harmful greenhouse gas emissions. Remote communities are interested in improving utility service to support social well-being and, at the same time, reducing their dependence on diesel-powered electricity for social and environmental reasons. In addition, governments are looking at ways to create job opportunities in these remote communities, leveraging alternative energy as a job creator. Renewable sources of electricity, such as wind, hydropower and solar are particularly attractive for remote communities since they offer a clean source of power in locations that cannot be economically served by means of a grid extension. A significant issue in relation to renewable power systems, however, is their intermittency and unpredictability. Often they cannot be relied upon to meet 100% of power demand, particularly during peak usage periods, but also relative to base power requirements. These issues of intermittency and reliability can be effectively addressed by storing surplus off-peak power for use during peak power periods. Off-peak energy can be stored in the form of hydrogen (produced using renewable energy and electrolysers), which will produce power during peak times by means of a PEM fuel cell system. While renewable power systems typically have relatively high capital cost, their operating costs are very low in comparison to diesel generators. Therefore, they have lower life-cycle cost and associated levelized cost of energy. Short term payback periods for renewable power systems relative to diesel systems are achievable, when combined with fuel cells. For an in-depth economic analysis, see Ballard s white paper entitled Fuel Cell Power as a Primary Energy Source for Remote Communities. Energy storage in the form of hydrogen (using renewable sources and electrolyser technology) combined with power production using a fuel cell system can enable remote communities to meet all or a significant proportion of their power needs in a highly economical manner. A Discussion of PEM Fuel Cell Systems and Distributed Generation 3

5 Energy Storage for Renewable Power Systems The evolution of the smart grid is facilitating distributed generation, providing an advanced management system that has the capability to balance electrical loads from diverse, and often intermittent, alternative generation sources. Prior to the integration of renewable energy sources like wind and solar to the electrical grid, the task of load-balancing was simpler, with conventional centralized power plants producing a predictable amount of energy on demand. Renewable energy sources, however, are subject to the natural conditions they encounter. Wind, solar and wave energy may only produce power during certain times, often not timed to match peak energy demand. A key component of the smart grid is the capacity to store electrical energy and to draw upon it when needed. Fuel cells coupled with electrolysers can offer a cost competitive grid scale energy storage solution. An economic analysis comparing the capital cost of a hydrogen energy storage system (electrolysers, compressors, storage tanks, and fuel cells) to a sodium sulfur (NaS) energy storage system for which off-peak electricity price is assumed to be $0.04/kWh. The results of this analysis are shown in Figure 1. Figure 1: Cost of hydrogen versus NaS energy storage system. Beginning at approximately nine hours of energy storage required, hydrogen systems can offer both a lower capital cost and lower levelized cost of energy compared to NaS systems. This is mainly due to the fact that in order to increase energy storage duration of NaS systems, additional (and expensive) batteries must be added. However, to increase the energy storage duration of hydrogen systems, only additional storage tanks (which are inexpensive) need be added. Additional electrolysers and fuel cells, the highest cost components, are not required to increase the energy storage duration. A Discussion of PEM Fuel Cell Systems and Distributed Generation 4

6 CONCLUSIONS When used in distributed generation applications, PEM fuel cell systems have the potential to save energy and reduce emissions over conventional power generation technologies. Compared to diesel and gas turbine generators, PEM fuel cell systems are more efficient, have lower greenhouse gas emissions, are readily scalable to meet power requirements and maintain high efficiency at all power levels during turn down. PEM fuel cell systems are a better choice for distributed power generation than other fuel cell technologies because they are capable of both load following and fast startup, at the lowest capital and operating cost. Market analysis has identified key distributed generation applications for PEM fuel cell systems. For industries that vent or burn by-product hydrogen, more value can be extracted using a PEM fuel cell system for electricity and heat. In remote communities, hydrogen powered PEM fuel cell systems can offer cleaner, more reliable source of energy than diesel and gas turbine generators. And, for grid scale energy storage applications that require significant durations of energy storage, hydrogen systems can offer a lower capital cost and levelized cost of energy than battery systems. REFERENCES 1 Sustainable Development Technology Canada ( 2 U.S. Department of Energy ( 3 Hydrogen Fuel Cars & Vehicles ( 4 Renewable Energy in Canada s Remote Communities, Kim Ah-You and Greg Leng, Renewable Energy for Remote Communities, Natural Resources Canada ( 27/ e.pdf) A Discussion of PEM Fuel Cell Systems and Distributed Generation 5