Energy’s Next Wave?

Energy’s Next Wave?

Fuel-cell technology catches the eye of managers looking for clean, cost-effective power. By David Kozlowski.

Right now, several hundred fuel cells might be blazing the trail toward the future of onsite power. Among alternative onsite power options, fuel cells are moving quickly to the top of the list. The technology remains immature, however, and poses some challenges. But it also offers significant benefits over its nearest onsite power competitors — microturbines and natural-gas-engine generators.

Reviewing some pros and cons of fuel cell technology will help maintenance and engineering managers prepare for future opportunities as fuel cell prices drop and grid power costs increase.

Kilowatts Without Combustion

Jim Cooke has two views of fuel cells. Cooke, national manager of real estate and energy for Toyota Corp., recognizes the cost benefit of and the quality of power from onsite fuel cells, but he is unsure about their reliability and maintenance needs.

As with other managers of large facilities, Cooke is confronting the next wave of onsite power technologies and the many options they offer. Manufacturers are incorporating improvements in these new technologies almost as quickly as they can add manufacturing capacity.

While fuel cells are on the crest of this new wave, they are also a technology with a long history. Developed in the 19th century, they have been used successfully by the National Aeronautics and Space Administration since the 1960s.

Fuel cell chemistry is well understood. The fuel cell electrochemical process begins with feeding hydrogen into the cells, where it is mixed with air. Hydrogen is stripped of some of its electrons, which flow as DC power, in a process that also releases heat. The hydrogen recombines with oxygen to form water, which the heat turns into steam.

Research efforts now focus on bringing down the cost of the units.

Fuel cells work much like batteries — using anodes, cathodes and electrolytes — but they can continue to produce electricity as long as fuel is fed to them.

A fuel cell has a leg up on a natural gas generator in that it doesn’t burn its fuel and, so, is more efficient. And it makes steam, rather than uses steam as a turbine might. And with no moving parts, fuel cells might require less maintenance than even a microturbine.

They have other advantages, as well. Because of their low emissions, they generally are easier to permit than an internal- combustion-engine generator or even a wind or photovoltaic system.

Fuel cells are considered clean sources because they produce practically no sulfur dioxide or nitric oxide — 0.003 and 0.0004 pounds per megawatt-hour, respectively. They produce carbon dioxide (CO2), but they produce less CO2 per given unit of power output than the average power source.

Fuel cells also are modular by design. Their power plants can be configured in a wide range of electrical capacities, from a few kilowatts to 100 megawatts. Also, they can use a variety of fuels and are very adaptable to combined heat and power or cogeneration systems.

A Cell Breakdown

Manufacturers are making and testing a half-dozen fuel cells, but the four most popular are proton exchange membrane (PEM) fuel cells, phosphoric acid fuel cells, molten carbonate fuel cells, and solid oxide fuel cells.

PEM cells have received the most attention because the automotive and residential building industries are interested in them. But they also can be used in commercial and institutional markets.

PEM cells use a solid polymer as the electrolyte. They are light, compact and durable, and they probably require less maintenance than the other cell types. They can use a variety of fuels, including natural gas, methane, propane and even gasoline.

But they require reformers, separate units that break fuel into hydrogen and carbon monoxide. Reformers have been the weak link in the PEM process, but technology is improving, according to Dan Rastler, area manager of distributed resources for the Electric Power Research Institute (EPRI).

As with all fuel cells, PEM cells produce DC power and require inverters. PEM units can be built to produce 250 kilowatts, but most units produce fewer than 10 kilowatts. They have a relatively high power density and can vary their output quickly, making them beneficial for automobiles, as well as peak shavers for facilities. They are 40-50 percent efficient.

PEM cells produce the least amount of heat of the major cells — about 200 degrees F — and because they run cooler, the stacks that make up a unit last longer — up to 20 years — and require less maintenance. PEM cells cost $3,000-4,000 per kilowatt. Mass production could drive down the price to $1,500 or less per kilowatt.

A More Mature Cell

Another fuel cell considered among the low-temperature cells is the phosphoric-acid fuel cell. This type of cell is relatively common, with more than 200 installed worldwide. It is arguably one of the most mature of the fuel cell technologies. The U.S. Department of Energy has been funding phosphoric-acid fuel cell research since the the 1970s. Phosphoric acid cells are 36-38 percent efficient, operate at about 400 degrees F and require a reformer. They vary in size, but one manufacturer makes a popular 200-kilowatt unit.

Because they operate at slightly higher temperatures, however, they require more maintenance. Stacks in the cell might need to be replaced every five to seven years.

These fuel cells cost about $4,000 per kilowatt, with an additional $100-200 per kilowatt for installation. This price could drop to about $2,000 per kilowatt if demand rises, but phosphoric-acid cells face stiff competition from the other three types, Rastler says.

Some manufacturers of these cells have begun to shift their focus to PEM cells. Concerns have arisen that phosphoric-acid fuel cells won’t be able to compete because they don’t produce high-quality steam. But there are rebate programs for phosphoric-acid cells, which are attracting managers’ interest.

The 400-degree F steam for domestic heat, along with generous subsidies, helped convince Cape Cod Community College in West Barnstable, Mass., that a phosphoric-acid fuel cell was a good idea. The college installed a 200-kilowatt phosphoric acid fuel cell several years ago and tied steam from the unit into the library’s hydronic system. The system cost about $700,000, and including domestic-heat savings and rebates, payback for the system dropped from 20 years to 10.

High-Temperature Cells

A big step up from the phosphoric-acid fuel cell is the molten-carbonate fuel cell, which facilities can use in combined heat and power systems for absorption cooling and as continuous base-load sources for facilities. For large stationary applications, they might offer the best deal.

Molten-carbonate cells have fuel-to-electricity efficiencies that approach 55-60 percent, and they operate at about 1,200 degrees F. When these cells are used in combined heat and power or when steam is used to generate additional power, efficiencies range from 60-85 percent. They can use natural gas, propane, methane, diesel and simulated coal gasification products. Units can range from 10 kilowatts to 2 megawatts.

They cost around $6,000 per kilowatt, but vendors project that price will drop to around $1,200 per kilowatt.

The Los Angeles Department of Water and Power is testing a number of fuel cells, including phosphoric-acid and molten-carbonate cells, and department officials hope the cells can generate up to 1 megawatt of power.

Because molten-carbonate fuel cells generate high temperatures, they can break down a fuel to extract hydrogen. But their higher operating temperature and efficient nature come at a cost: the diminished life of system components.

Solid-oxide fuel cells produce steam at an even higher temperature than molten-carbonate fuel cells. Solid-oxide cells operate at temperatures up to 1,800 degrees F and can provide high-quality heat for energy production or cooling.

The advantage of this cell over a molten-carbonate cell is that its electrolyte is solid rather than a liquid, making it easier to control. Nonetheless, the cell’s high operating temperature places stringent requirements on its materials. So far, these requirements are the biggest technological hurdle for solid-oxide cells.

The cells cost about the same as the other types — $4,000-5,000 per kilowatt, with another $100-200 per kilowatt added for installation. Manufacturers expect the price to drop to around $1,200.

Challenges Remain

Even though fuel cells have been around for four decades, challenges remain to using the technology.

One decision is whether to buy the physical asset or just the power. Despite many successful trials, no commercial stationary fuel cell has been field tested to the full extent of its life. And even though manufacturers are gearing up for mass production, maintenance and engineering managers are still justifiably unsure about the maintenance requirements of these units.

Some facilities have purchased them outright, with the aid of generous public subsidies. Utilities also are buying and operating the units for customers. But the future of fuel cell applications in facilities might lie in third-party ownership.

“We see third-party ownership with either a utility or an energy company owning the system,” says EPRI’s Rastler. “They will have the expertise to do the maintenance and other things to provide a facility with its energy needs at the lowest cost.”

Another major challenge for fuel cells is their size. PEM and phosphoric-acid cells offer fewer concerns in terms of weight and physical proportions, but molten-carbonate and solid-oxide units can be quite large and heavy.

Installation costs also are an issue with fuel cells, especially the larger ones and those integrated into a combined heat and power application, Rastler says. For this reason, fuel cells may make more sense when installed with new construction rather than as a retrofit.

Rastler says a well-engineered concrete pad and a crane are necessary for installing some fuel cells. A popular 250-kilowatt unit might weigh up to 80,000 pounds. The crane is necessary for removing stacks to perform maintenance.

And while high-temperature fuel cells — molten carbonate and solid oxide — do not require a reformer to break a fuel down to hydrogen, they do require desulfurized fuel, such as natural gas and even gasoline, both of which would have to be treated to remove the sulfur.

Most experts believe the groundwork has been laid for fuel cells. There are still some bugs to be worked out, but fuel cells offer reliable and clean power and can be cost effective for applications that require the highest level of reliable onsite power. The technology is still too expensive to compete on a simple base-load premise with grid power, but each day sees significant progress.

“The experience from phosphoric acid fuel-cell field applications suggests good availability and reliability for these systems, and this should translate to molten carbonate, PEM and solid oxide units,” Rastler says. “On top of it, all vendors are paying special attention to maintainability, meaning easy access to subsystems that are easily removable.”

By David Kozlowski, senior editor of Building Operating Management, a GreenBiz News Affiliate. © 2001 Trade Press Publishing Corporation.