June 10, 2004		2004-R-0475
FUEL CELLS AND BIOMASS
By: Kevin E. McCarthy, Principal Analyst

You asked for background information on fuel cells. You were interested in the status of the market for this technology, particularly for use in power plants, the technology’s costs compared to traditional power plant technologies, and the feasibility of using biomass gasification in conjunction with fuel cells.

SUMMARY

Fuel cells operate like a battery, turning oxygen and hydrogen into electricity in the presence of a material called an electrolyte. Fuel cells have significant environmental advantages over traditional power generation technologies, which use combustion to generate electricity. Fuel cells are also highly reliable and produce high quality power (for example, the power they produce has very little variation in voltage). On the other hand, fuel cells are far more expensive than traditional generation technologies.

Fuel cells have been on the commercial market since 1991. There have been approximately 650 stationary fuel cells installed worldwide, with approximately half installed in North America. We were unable to determine how many have been installed in New England, although there are several installations in Connecticut. Most fuel cells generate power for on-site use, rather than for sale over the transmission grid. Historically, most fuel cells have used phosphoric acid as an electrolyte.

The number of installed fuel cells has grown steadily in recent years and several new electrolyte technologies are approaching commercial status. However, fuel cells represent a very small fraction of installed generation capacity. While their costs are decreasing, it appears that they will be used primarily in niche markets, such as high technology manufacturing, for the foreseeable future. In these markets the fuel cells’ advantages in reliability and power quality outweigh their cost disadvantage.

Currently, the vast majority of fuel cells use natural gas as their source of hydrogen. Biomass, such as wood or crop wastes, could also be used as a feedstock, but research is in its early stages. One research project will develop a gasification facility at a sawmill in North Canaan, Connecticut. Eventually, the gas will be used in a fuel cell as a hydrogen source.

Connecticut is home to several companies involved in fuel cell research and development. They include UTC Fuel Cells in South Windsor, Fuel Cell Energy in Danbury and Torrington, Proton Energy Systems in Wallingford, and Southbury-based GenCell. In addition, the Global Fuel Cell Center at the University of Connecticut (http: //www. ctfuelcell. uconn. edu) is conducting basic research on several fuel cell technologies and the Connecticut Clean Energy Fund (http: //www. ctcleanenergy. com) has financed several fuel cell projects.

While this memo focuses on the use of fuel cells in power plants, there is also a great deal of research and development being conducted in Connecticut and elsewhere on using fuel cells in vehicles and in portable consumer electronics.

FUEL CELL TECHNOLOGIES

A fuel cell is like a large, continuously operating battery that produces power from an electrochemical reaction of hydrogen and oxygen. The oxygen comes from the air and the hydrogen from fuels such as natural gas. Unlike a battery, a fuel cell does not run down, so long as it is supplied with hydrogen and oxygen.

Like a battery, a fuel cell has an anode (a negative electrode that repels electrons), a cathode (a positive electrode that attracts electrons), and an electrolyte in the center. Hydrogen is fed into the anode side of the fuel cell and oxygen into the cathode side. A platinum coating on the anode helps separate the hydrogen into protons and electrons. The electrolyte in the center allows only the protons to pass through to the cathode side of the fuel cell. The electrons cannot pass through the electrolyte. Instead, the electrons flow through an external circuit in the form of direct current, which can be converted into the alternating current that is used in most applications. At the cathode, another catalyst rejoins the electrons and protons of the hydrogen atoms, which then combines with oxygen to create water. Individual fuel cells can be combined into a fuel cell “stack”. The number of fuel cells in the stack determines the total voltage, and the surface area of each cell determines the total current. Multiplying the voltage by the current yields the total electrical power generated.

In general, fuel cell technologies differ in the electrolytes they contain. The most commercially developed type of fuel cell uses phosphoric acid. This type of fuel cell is most appropriate for larger scale applications. Phosphoric acid fuel cells achieve very high conversion efficiencies, approximately 40% of the energy contained in the fuel is converted to electricity, compared to approximately 15% for combustion technologies. Efficiencies are even higher when the waste heat produced by a fuel cell is used to heat water or living spaces. However, power plants using these fuel cells are usually large, heavy and require warm-up time.

Another type of fuel cell contains a proton exchange membrane, a thin plastic membrane used as the electrolyte. These fuel cells operate at relatively low temperatures of around 175°. This allows them to start quickly. They also are relatively light and small, making them particularly suited for use in vehicles.

The electrolyte in molten carbonate fuel cells consists of a molten carbonate salt mixture suspended in a porous, chemically inert ceramic lithium aluminum oxide matrix. These systems are large and operate at temperatures around 1,200ºF. These fuel cells are very efficient when the heat produced is used for co-generation. However, because these fuel cells use a corrosive electrolyte, their durability is limited.

Solid oxide is another very promising fuel cell technology. A hard ceramic material is used instead of a liquid electrolyte. Solid oxide fuel cells operate at temperatures around 1,800ºF. As a result they are highly efficient and heat can be recaptured for co-generation purposes, resulting in efficiencies of 80 to 85%. Size, heat output and a long start-up time make this fuel cell more suitable for stationary rather than vehicle applications. This technology is at a relatively early stage of development compared to the other fuel cell technologies.

A 2003 report by the Connecticut Academy of Sciences and Engineering (CASE) discusses these technologies and factors affecting the development of the fuel cell industry. The report is available online at http: //www. ctcase. org/bulletin/fuelcells. html.

ADVANTAGES AND DISADVANTAGES OF FUEL CELLS

Fuel cells have significant environmental advantages over traditional power generation technologies. Fuel cells create few traditional emissions, such as sulfur oxides, because they produce power without combustion, although some pollution is created in extracting the hydrogen from the feedstock. Fuel cells also produce less than half of the carbon dioxide (which is implicated in climate change) compared to combustion technologies. Because fuel cells contain no moving parts, they are also very quiet.

Fuel cells can be very reliable (functioning as much as 99. 9999% of the time), and have been used in settings such as hospitals, where power outages are unacceptable. Fuel cells also produce high quality power. For example, there is very little variation in the voltage of the power produced. This is particularly important in high technology manufacturing, where even minor variations in power quality can impose substantial financial costs.

The principal disadvantage of fuels cells is their cost. Fuel cells cost at least $ 4,000 per installed kilowatt (kW-the amount of power used by ten 100-watt lightbulbs). This is more than seven times the cost of a combined cycle natural gas plant (the type of technology used in most new power plants). While fuel cells are more fuel efficient than traditional technologies, this does not offset the higher capital costs. In addition, there has been little operating experience with electrolytes other than phosphoric acid.

market status

Fuel cells have been on the commercial market since 1991. According to a September 2003 survey by Fuel Cell Today, a trade journal, there have been about 650 large stationary fuel cells (those with a capacity of 10 kW or more) installed worldwide. The number of installed fuel cells has increased steadily in recent years, with a noticeable upturn since 2001. The survey notes that the phosphoric acid electrolyte technology is beginning to be overtaken by molten carbonate, proton exchange membrane, and solid oxide fuel cells.

Although the costs of fuel cells have been falling steadily, it does not appear that they will be able to compete with traditional technologies in most applications, including power plants, in the foreseeable future. There is a consensus in the industry that fuel cells will be able to compete in niche markets where their advantages outweigh their higher costs. Among these markets are applications, such as financial institutions, on-line commerce, and hospitals, where reliability is a vital concern, and in applications where the customer can use the heat generated as well as the power produced by the system (cogeneration). According to the CASE report, two Connecticut companies, UTC Fuel Cells and Fuel Cell Energy, are nationally competitive in these markets, with even greater market penetration anticipated as production volume increases and prices drop.

Fuel cells have installed in several locations across New England, primarily for on-site generation of power at institutions and businesses. The Connecticut Clean Energy Fund, administered by Connecticut Innovations, Inc. has funded several fuel cell projects. These include installations at Saint Francis Hospital in Hartford, Yale University, the New Haven Water Pollution Control Authority, and South Windsor High School. The projects produce a total of 850 kW of electricity, or about the mount of power used by 750 average homes. Two 200-kW systems have been installed at the Mohegan Sun casino, and a 40 kW molten carbonate system is being installed at the UConn Global Fuel Cell Center. In contrast, an average power plant using traditional technologies produces 600 megawatts, i. e. nearly 500 times the combined capacity of the fuel cells in the state (a megawatt is 1,000 kilowatts).

USING BIOMASS IN FUEL CELLS

Although the overwhelming majority of existing fuel cells use natural gas as their source of hydrogen, other fuels including gas from biomass can be used. Biomass includes a wide variety of organic materials including wood waste; paper trash; yard clippings; agricultural residues, like wheat straw or used vegetable oils; and fast-growing trees and grasses. Gasification uses a process known as pyrolysis, which differs from combustion in that it has virtually no emissions. The biogas produced by gasification has a substantially lower energy content than pipeline gas and requires some cleanup before it can be used. Biogas can also be produced at sewage treatment plants and landfills.

A few fuel cells already have been built that use biogas. A 100 kW plant in Kobe, Japan, generates power using food waste collected from hotels that is broken down in a methane fermentation system. The Connecticut Clean Energy Fund is sponsoring research at a sawmill in North Canaan where woodchips will be gasified and used in a 288 kw reciprocating engine generator. This phase of the project will go into service in July. In the second phase of the project, which is in design, a 10 kw fuel cell will be installed to use part of the gas produced by the gasifier.

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