At wastewater treatment facilities, microturbines are turning the gases emitted by waste into electricity. Dairy farms are powering their own facilities with methane gas from cattle waste. Such microturbine uses get the most attention, but they have little to do with commonplace construction or the power supply at industrial, commercial or residential sites. But are these gas-fueled generators on their way to the mainstream? The answer may be yes if the United States follows a trend taking place in other parts of the world, such as Europe and Asia.

A microturbine generator, using natural gas or in some cases other liquid fuels, creates power parallel to—or sometimes independent of—the power grid. In Europe and Southeast Asia, the cost of power has risen high enough that the payoff for this kind of distributed generation is clear. In the United States, where coal burning and nuclear power plants can still provide power at lower cost, there seems little incentive to spend money to generate your own power. But that is changing for several reasons. Power costs in the United States are rising, and political pressure to reduce carbon footprints is rising with it. Furthermore, some states are making it easier for users to install their own distributed power generators.

Then there is the energy reliability concern. As the world depends increasingly on digital information, data center facility managers and operators have less tolerance for power sputters and burps, not to mention power outages caused by the grid. A microturbine generator may offset some of these power quality disturbances, reducing downtime.

For all these reasons, thousands of microturbines are in use today, while eight or 10 years ago, they were almost nonexistent.

What a gas!

Capstone Microturbine, Chatsworth, Calif., and Ingersoll-Rand, Montvale, N.J., which has teamed up with United Technologies Co. (UTC) Power, South Windsor, Conn., are just two of many manufacturers that now produce microturbine generators. Both offer a combined heat and power (CHP) product that uses waste heat to heat buildings and water, and two such large competing manufacturers are good for the microturbine market.

“A market badly needs at least two major manufacturers to help [it] develop,” said Scott Samuelsen, director of the Advanced Power and Energy Program, (APEP), at the University of California, Irvine. Thus far, Ingersoll-Rand has more than a million operational hours. But, there are other forces at work that are propelling growth in microturbine usage.

In areas of the country where, today, utility cap rates are expiring, microturbine interest is on the rise—primarily in the Northeast and California as well as some Midwestern states such as Illinois. These are the only places, thus far, with a combination of high energy rates and government regulations that put caps on grid usage. They also may have a greater need than average for uninterruptible power.

To make microturbines a commonplace energy option, more states need to have policies that accommodate the power source, and there also needs to be more demonstration of successful usage in highly visible buildings such as office complexes, Samuelsen said. Better education of architects and developers will help draw microturbine technology into the planning phases of buildings. At the same time, on the vendors’ side, he said, further development of waste heat usage is essential.

The direct current (DC) production by microturbines, fuel cells and photovoltaic power create another advantage in the long run. It takes additional power to convert DC to AC, so eliminating that step would be beneficial. And since fluorescent lighting can run directly off DC, according to Samuelsen, that AC/DC conversion is not necessary.

Cogeneration also is making the technology more desirable said Jim Watts, Ingersoll-Rand product manager. And climate change regulations can expect to make microturbines more common, said Joe Catina, manager of projects at Ingersoll-Rand.

It may be the regulations that will have the greatest impact. The California Air Resources Board issued strict air emission requirements in 2007, but according to Watts, Ingersoll-Rand’s MT250 is on par with all those regulations. In fact, thus far, Ingersoll-Rand is the only major manufacturer of microturbines that has met California’s requirements. That is because, Watts said, of the product’s ability to produce low emissions with tighter regulations. They can do so in non-attainment areas, he said, making microturbines the most attractive option.

Among the environmental benefits in using this technology are the reduction of emissions of sulfur dioxide, nitrogen oxides, carbon dioxide and carbon monoxide resulting from coal combustion. To accomplish this, you don’t want to chase the single-digit nitrogen dioxide (NOx) emission level. Otherwise, you have added complexity to the design and, in some cases, additional equipment. To achieve the ultra-low NOx, some manufacturers use a type of combustion system that limits the operating load range and the transient response to changes in load. The tradeoff is that the system cannot operate at very low loads without risk of flameout. A company called Elliott makes a microturbine system that doesn’t require additional equipment; the system can be used in a stand-alone application without difficulty,” said John D. Holbrook Sr., Elliott Microturbine’s marketing manager.

Where and how?

When it comes to the kind of application, opportunities are across the board, Catina said. But, contractors need to know how and when to install a microturbine.

The installation consists of usually five outputs, which is pretty straightforward according to those who have done it. And for those who haven’t, there are comprehensive training programs available on the market.

The more complex installations are those involving synthetic gas such as from biomass, animal or vegetable waste. One example of that is Emery Station in Emeryville, Calif., with a 750 kW solution that hedges the rising utility costs.

In most cases, microturbine-generated electricity is used to base load the facility while the electric utility fills in when the generator runs short. The hot water is used to preheat return or makeup water for a boiler. In some cases, the hot water is generated and stored without the use of a boiler.

For installations such as data centers, the primary focus has been on combined heat and power working parallel to the grid to ensure clean and reliable power, Holbrook said. “I think contractors are going to see more of these bid out,” he said.

Elliot has a half-dozen microturbine installations in Manhattan and others scattered throughout the northeast, but it still sells more of its product in Europe. However, it is becoming more popular in the United States.

“They’re quite popular at sewage treatment, farm applications. Certainly they may not be universally acceptable since it is very hard to complete with bulk power from coal burning and nuclear plants,” Samuelsen said.

Cost effective?

Because the technology is still new, costs can vary widely, Catina said. “It’s not so much the installation itself as the project cost,” Catina said. “A lot of contractors haven’t seen a microturbine before. As they get more experienced, more knowledgeable, they will be easier to install.”

“Architects are beginning to specify them; governments are [offering incentives]; and we’re trying to get contractors up to speed with that,” Catina said.

In Europe and Asia, Samuelsen said, microturbine growth is years ahead of the same technology in the United States. “They have greater incentive,” Samuelsen said. “Distributed generation offers energy efficiency when the waste heat is used.”

The financial basis for installing a microturbine CHP system is measured by the amount paid for energy today, in electrical and gas, and the amount that will be paid after the CHP system is installed. If there are net savings, they are combined in an economic project and viewed over 10 years. If the project has a positive net present value (NPV), then there are benefits to installing the CHP system. If the NPV is negative, there is no benefit, Holbrook said.

“When one wants to identify a good market, the first thing to consider is the cost of gas versus the cost of electricity,” Holbrook said. “This cost differential is referred to as the spark-spread.”

“The customer should be anticipating base loading their facility,” Holbrook said. “With each installation, you have to look at the economics. You have to ask, ‘Will there be an economic payback with the combined heat and power feature?’”

“I think there is a 70 to 80 percent chance the microturbine market will take off,” Samuelsen said, and he expects that to happen in the next year. “I believe the market is getting over the hump.”

Others are more conservative in their estimation. At the Electric Power Research Institute, an independent, nonprofit center for public interest energy and environmental research, Clark Gellings, vice president of innovation, said his group is taking a wait-and-see stance. He pointed out, however, that with over 4,000 units in the 30 to 65 kW range sold worldwide, it’s hard to ignore the impact of microturbines. EC

SWEDBERG is a freelance writer based in western Washington. She can be reached at [email protected].