Pictures of the Future      Fall 2008

How to Own a Power Plant

Innovative heating systems not only provide warmth but also satisfy two thirds of the electricity demand of an average four-person household.

Demand for resource-saving heat generation systems is growing. One driver of this development is the fact that well-insulated new buildings and renovated older structures have lower heating demand. In addition, high energy prices as well as insecurity on the part of consumers regarding the reliability of gas and oil supplies are also prompting researchers and developers to consider new heating methods.

One such method is the simultaneous generation of heat and electricity by so-called CHP (combined heat and power) systems. These are among the most efficient methods of energy generation, because the fuel they use is transformed into electrical energy as well as heat—usually in the form of steam and hot water. More than 90 % of the energy contained in fuel can be utilized by these systems, compared with only about 38 % for electrical generation by a conventional power plant. This high thermodynamic efficiency can make a major contribution to operating economy as well as environmental protection. Simultaneously, emissions of carbon dioxide and nitrogen oxides are reduced.

Until now, CHP technology has been limited to large installations. Although the idea of applying it to single and multi-family homes is new; many manufacturers are already excited about exploiting this potential. Siemens Building Technologies (BT), for instance, has developed the electronics for a gas-fired micro heat and power cogeneration device (microCHP). "We see a clear line of development toward the use of personal small power plants in single-family homes in place of oil or gas-fired boilers," says Georges Van Puyenbroeck, director of sales and marketing at BT’s OEM Boiler & Burner Equipment. With this goal in mind, BT specialists are working together with manufacturers of condensing boilers, including Viessmann, Vaillant, Remeha B.V., and the Baxi Group.

How to Generate a Kilowatt. Until now, condensing boilers have produced only heat, but no electricity. MicroCHP devices, on the other hand, can do both. They work as follows: A gas-fired Stirling engine is integrated into a wall-mounted boiler. The temperature difference between the cold water and the heat provided is used to generate electricity. Current implementations permit the generation of a maximum of one kilowatt of electrical energy, of which about 900 W can be used directly in the home or fed back into the energy supplier’s grid. The device itself uses 100 W.

For consumers, this means that they have at their disposal their very own miniature cogeneration power plant, which provides not only heat but also two thirds of an average four-person household’s electricity requirements. The remaining electricity is provided by the power grid to which the microCHP device is normally connected. Operation with liquefied petroleum gas (LPG) is also possible after appropriate readjustment of the device.

Siemens electronics control the heat output to keep the Stirling engine within its permissible operating range and provide the desired temperatures for home heating and hot water at the proper times. In addition, the electronics monitor the feeding of surplus electricity back into the power utility’s grid.

Control technology from Siemens ensures that the device, which operates in parallel to the power grid, is able to switch on and off at the proper times. The burner for the Stirling engine alone produces five kilowatts of heat. An auxiliary burner can add between 10 and 30 kW, depending on its size.

As a special feature, the microCHP device can also operate independently of the grid. In this case, it disconnects itself from the grid and produces up to 1 kW of emergency power for specially vetted emergency power groups such as refrigerators, freezers, and emergency lighting. "That is a key differentiating feature of our device," says Wolfgang Huber, who is responsible for development at Siemens BT.

Huge European Market. Even if its advantages aren’t obvious at first glance, the microCHP device is a significant innovation. Paul Gelderloos, manager of technical innovation at Remeha B.V., is certain that "the device is one of the most promising successors in the condensing boiler area," he says. Georges Van Puyenbroeck adds that, "It offers simple access to alternative energy; installers know about boilers, only the electrical generation is new."

He sees great potential for the new product. "According to our market data, seven million wall-mounted boilers are sold in Europe every year," he says. Product manager Markus Herger estimates that in its the first three years on the market, between 50,000 and 100,000 microCHP devices could be sold—and that sales will continue to grow after that. This depends on how energy suppliers respond and on political decisions.

In countries where sales operations are about to be launched—the Netherlands, then England and Germany—there are so-called electricity buyback laws, which promote microCHP devices. "Other countries are not yet as advanced," laments Herger.

After about four years of development, Siemens’ development partners are currently testing the new microCHP devices in about 400 households in Great Britain, the Netherlands, and Germany. Experience has shown that the added cost of a microCHP device can be amortized within five years—but its price can be established only after the partners bring the device to market.

Siemens intends to launch production of the control technology in the fall of 2008. Remeha B.V. plans to enter the Dutch market in the winter of 2009. And specialists are already working on developing the next generation of microCHP devices. These will be even smaller, lighter, and more powerful than their predecessors, and can be fired by a variety of primary energy sources such as oil or various gaseous fuels from biomass.
                                                                                                                  Gitta Rohling