By John Gibson, P.Eng.
The fuel cell is an environmentalist's dream. With changes going on in the power industry, these zero-emission engines might eventually heat and light your house.Political power grows out the barrel o...
The fuel cell is an environmentalist’s dream. With changes going on in the power industry, these zero-emission engines might eventually heat and light your house.
Political power grows out the barrel of a gun.” Mao said that. Most will agree that the pursuit of electrical power tends to be slightly more gentile; it is only very rarely that anyone gets shot. But as in politics, the pursuit of electrical power often stirs up strong emotion — fervent anti-nuclear protests in the 1960s and Native opposition in James Bay, to name just two examples.
One of the most intriguing changes to take place in the electric power industry recently is the trend towards deregulation. This devolution of control means that electricity is no longer being produced solely by large, and government-backed, utilities. Consulting engineers who design power plants and transmission systems are facing a radically different client environment as they work with independent power producers. As well, in response to the growing influence of market force the technology of power production is undergoing change.
The electrochemical fuel cell, for example, has had a lot of publicity recently as an exciting alternative means of generating electricity. The cost of this technology, first discovered in the 19th century and later used by NASA for space exploration, has decreased significantly over the past decade.
Many are aware of fuels cells as a means of producing emission-free vehicles. But fuel cells could also have a major role in the future in stationary electrical power generation, especially in applications requiring 250 kW or less.
Traditional approaches to power generation face a number of challenges. Sir Adam Beck met relatively little resistance when attempting to use the natural tendency of water to flow down a hill to spin generators at Niagara Falls. However, today such large-scale hydroelectric projects are often considered environmental, as well as political, nightmares. Most naturally occurring waterfalls are already in use. Any attempt to dam a river for the purposes of power generation often meets with stiff resistance. Then there is the nuclear alternative. Even nuclear supporters start to look a little sheepish when the conversation turns to deadly substances kicking around well into the next four or five millennia. Today, then, perhaps more than ever before, environmental pressures are forcing power producers to consider alternative means of generation.
Aside from their environmental problems, the traditional approaches to electricity have another, more direct, challenge: cost effectiveness. Oliver Yu, director of energy and utility systems at SRI International, a large California based energy consulting firm, says that when large utilities were “operating as regional monopolies earning a fixed income on their investments, it used to make sense to have central power stations.” In the past, with a captive audience, it was possible to offset the costs of building a massive and expensive power station and a large high voltage distribution network over a long term.
Industry experts suggest that in the future power utilities will have to be more nimble to stay in business. During periods of peak demand, the need for additional electricity could likely be met by several smaller power sources. These sources could be incorporated directly into the low voltage lines found in congested and power-starved urban areas. The approach saves money in two ways. First, there is no need for high voltage transmission lines. Second, large power plants do not operate efficiently when there are large fluctuations in demand. With small local power generation, sometimes called “distributed power generation,” costs per kilowatt are relatively low and it is easier to react effectively to changes in usage.
Nuclear power is too dangerous for small distributed systems, and hydroelectric power is simply not available in most locations. However at smaller scales fossil fuel-based systems have some advantages. The tried and true diesel-electric generator is tough to beat in terms of cost and reliability. Unfortunately Herr Diesel does not get good marks for efficiency or environmental impact. These motors convert chemical energy in the fuel, to mechanical energy in the motor, which eventually gets converted to electrical energy in the generator. At each step along the way, energy is lost. Also, diesel motors tend to produce large numbers of particles which end up in people’s noses and lungs..
Now fossil fuels come from fossils, right? Ancient plants, having had their day in the sun, promptly die and become coal mines or tar sands. But why not harness electricity directly from sunlight? This would seem more agreeable than all that noise and soot. Though producing electricity from sunlight through photoelectric cells is promising, the approach has historically been limited by cost. Solar power equipment typically costs $5,000 per kilowatt of generating capacity. Also solar power generation tends to be difficult in northern climates that receive little sunlight throughout much of the year. Oil or natural gas represent the sum total of perhaps millions of days of sunlight shining on trillions of plants, distilled down to a liquid or gas form. Fossil fuels are an energy form with which it is tough to compete.
In a fuel cell, electricity is produced directly form the energy stored in the fuel but without moving parts or combustion (in the traditional sense). Take two gasses, hydrogen (H) and oxygen (O) for example. Anthropomorphically speaking, the molecules in these gases would be much happier if they could get together to form a molecule of water (H2O). What a fuel cell does is divert electrons temporarily as the gas molecules follow their natural progression towards water, without combustion.
Herein lie the advantages. Electricity (the diverted electrons) is generated from the chemical reaction directly. This means there is a more efficient use of the fuel — whether it is natural gas, methanol or hydrogen. No moving parts means little maintenance, and little energy lost as friction. A number of smog producing gases such as nitrous oxide generated in the combustion of fossil fuels at high temperatures — in your car’s engine for example — are not produced in fuel cells. Also the quantity of greenhouses gases generated per kilowatt is reduced. Fuel cells are an inherently clean and efficient source of electrical energy. This makes them ideal power systems for congested urban environments.
It is for their environmental advantages that so much fuss is being made about fuel cells in general, and a Canadian company called Ballard Power Systems in particular. To automotive types the fuel cell is seen almost as a panacea. Electric cars powered by fuel cells have curried favour with such disparate interests as the Chicago Transit Authority, Daimler Chrysler, and the fastidious State of California (Globe and Mail Report on Business, April 17.) Vancouver transit has also tested fuel-cell powered buses.
In terms of distributed power generation, however, the fuel cell will have to compete with a number of other technologies in the 100-500 kW range.
As mentioned previously, diesel-electric generators will undoubtedly take a slice of the pie. From the point of view of many engineers, diesel electric power is an ideal solution. Many thousands of machines have produced millions of kilowatts over the last century. The infrastructure for parts, fuel, technical support and so on is well established so there is little technical risk involved.
Another promising small and responsive source of electricity is the microturbine. These devices operate in a way that is similar to jet engines. Fuel combustion in the turbine produces rotation that powers the generator. Microturbines tend to be more efficient than diesel motors and can use a variety of fuels including hydrogen gas, methane, and even gasoline. Their costs have decreased recently making them strong contenders for distributed power generation.
However, both diesel electric
and microturbines have an attribute which fuel cells do not: they generate noise. The microturbine is about as loud as a vacuum cleaner. Because the fuel cell has no combustion and no moving parts, it operates almost silently. It was its quietness that helped Ballard power systems get its start in the fuel cell game.
It is only natural that military types put a lot of emphasis on the ability to sneak up on things. This goal is difficult to achieve with a diesel generator chugging away to keep the lights lit (just watch the movie Das Boot.) The Canadian military approached the flagging Ballard organization in the 1980s in the hope of developing a source of electrical power that was, to use the military term, more stealthy. (The Germans had also had a crack at it late in WW II, but that is another story.)
Initially supported by the Canadian military, Geoffrey Ballard a geophysicist by trade, successfully produced an economical alternative fuel cell design. The result was the patented Proton Exchange Membrane (PEM). The proton exchange membrane is the hallmark of the Ballard device. Each “cell” in a fuel cell device contains one of these membranes that are coated with a small amount of platinum catalyst. The membrane facilitates the movement of protons which makes the whole thing go. On either side of the membrane are graphite electrodes for collecting and distributing electrons. Through the clever use of relatively inexpensive materials and manufacturing methods borrowed from the chemical and automotive industries, the cost of fuel cells has been drastically reduced.
One limitation of fuel cells in stationary applications is their size. Since the chemical potential that exists between the hydrogen, oxygen and water is finite, each individual “cell” can only produce a less than single volt. In order to get a substantial voltage across a fuel cell device, it is necessary to combine numerous cells together in a stack. The number of cells in the stack determines the power output of the device. At present, a single stationary power system has a maximum practical generating capacity of around 250 kW.
Costs are another factor. The fuel cell, like digital watches or Model A Fords, must make that difficult transition from what seems like a good idea to something that people can actually afford to purchase. Historically fuel cells have been very expensive but costs are coming down. The device used in the Apollo (number 13 included) and Gemini spacecraft cost $400,000-$500,000 per kilowatt of generating capacity. Ballard Generation Systems’ 250 kW stationary fuel cell currently costs approximately $500,000 in total, or about $2,000 per kW.
Ballard is researching fuel cell systems using methane from sewage treatment facilities or landfills. It has also been linking up with other environmental engineering firms around the world to develop new applications. In 1998 EBARA Corporation of Tokyo obtained the rights to market and manufacture Ballard’s fuel cell stationary power plants in Japan, and will using them in cogeneration facilities using methane gas from water in waste treatment facilities. Later that year GEC Alsthom of France bought four 250 kW natural gas fuel cell power plants for field trials.
Will the environmental advantages of the fuel cell eventually see it become a standard for distributed power generation? A lot depends on what happens in the automotive industry. The challenges are related to infrastructure and cost. But if the automotive fuel cell takes off in a way that many predict, the appropriate fuels, parts, and servicing are bound to become more readily available. Second, if the large automakers begin building PEM fuel cells by the thousands, the resulting economies of scale will take costs even lower.
Ballard is quoted as saying, “the internal-combustion engine will go the way of the horse. It will be a curiosity to my grandchildren.” If this happens, it is possible that 10 years hence a fuel cell quietly steering electrons in your direction could be as common as a household furnace.
John Gibson, P.Eng. is a writer based in Guelph, Ontario.