by Sandra Curtin
A new approach to power generation is on the horizon. Research, development and demonstration (RD&D) efforts are facilitating the deployment of microgrids, allowing multiple consumers to become connected microsource power suppliers that serve a network’s aggregate power and thermal demands. Microgrids are ideal for incorporating alternative energy sources and can be made highly efficient through recovery of waste heat to provide heat, cooling or hot water (cogeneration).
Microgrids are poised to offer tremendous benefits to business operations, providing a level of quality and reliability that surpasses the conventional power grid, making them ideal for critical applications. According to the National Power Laboratory, American businesses suffer losses of $29 billion annually from computer failure during power outages. In addition, computer locations typically experience 289 power disturbances each year outside of equipment voltage limits. Microgrids will help to remedy these situations. Using a single point of connection to the main grid, the system will seamlessly disconnect during power outages or voltage sags to operate in “island” mode, protecting mission-critical power electronics from damage and ensuring ongoing operation.
Fuel cells—devices that convert chemical energy to electricity without combustion—are an ideal generating source for microgrids, besting alternative technologies like wind and solar because of their ability to produce round-the-clock, disturbance-free, computer-grade power. All that’s required for an extended operating period is a steady supply of hydrogen. Fuel cells also surpass internal and external combustion engines since they are silent and emissions-free, permitting placement indoors. Fuel cell efficiencies are high at 40 percent to 60 percent, increasing to 80 percent to 95 percent with cogeneration.
U.S. 1, Japan 3
Presently, one U.S. microgrid uses fuel cells. NextEnergy Center, a business convergence facility in Detroit, features a Microgrid Power Pavilion offering integration, testing and validation platforms for alternative energy technologies. Most electricity produced by clients is used to power the NEC building, with thermal energy captured to produce hot and chilled water. Power production is not static and depends upon demonstrations underway: sometimes, the facility draws power from the local DTE Energy grid, at other times it sends power to the grid from the technologies being tested. Since the Center’s opening in 2005, the Pavilion has featured a periodic power generation by four 5-kW proton exchange membrane (PEM) fuel cells.
The Next Energy Center is a Federal Energy Regulatory Commission-qualified generation facility that can operate in either grid-tied or island mode. Interconnection provisions are in place (though not completed) to allow the Center to provide power to two nearby buildings, one within the technology park and the other at nearby Wayne State University. NextEnergy officials believe that these interconnections will be valuable as distributed generation becomes more prevalent, moving the facility beyond its current RD&D role.
One of the ongoing projects at the Center is the deployable Mobile Electric MicroGrid Power System for the U.S. Department of Defense. The project focuses on development of an electronic power control and conditioning system that will accept diverse generating assets, including renewable technologies like fuel cells. This microgrid will be able to deliver clean and stable power equal to, or better than, the quality of the North American grid, and will reduce consumption of conventional generation fuels.
Fuel cell microgrid RD&D has progressed further in Japan, where the New Energy and Industrial Technology Development Organization (NEDO) has funded development of several microgrids incorporating the technology. The first debuted at the Aichi 2005 World Exposition, composed of four 200-kW phosphoric acid fuel cells, a 25-kW solid oxide fuel celL, 270-kW and 300-kW molten carbonate fuel cells (MCFCs), 330-kW of photovoltaic generation, and a 500-kW NaS (sodium sulfur) battery system to control power supply and demand. Waste heat was cogenerated to drive an air conditioning system and provide cold water. Several sources were used for hydrogen fuel, including city gas, methane fermentation of organics, and gasification of the Expo’s plastic bottle and wood waste. The microgrid operated successfully during the entire six months of the Expo, including experimental operation in grid-isolated island mode, meeting all power needs of one pavilion and sending additional power to another. It has subsequently been moved near Nagoya to power a city hall and water treatment plant.
In late 2005, a virtual microgrid was started in Kyotango City, linking an energy control center to grid-tied distributed resources. Supply and demand are controlled through internet protocol communication, with imbalances resolved within five minutes. The distributed generation network includes a 250-kW MCFC, a 50-kW photovoltaic system, 50-kW of wind turbines, five 80-kW biogas engines and 100-kW of battery backup.
In 2006, NTT Facilities (an arm of telecom giant NTT) established a microgrid at Sendai’s Tohoku Fukushi University, featuring a 250-kW MCFC, two 350-kW natural gas-fired gensets, 50-kW of photovoltaic cells, and battery backup. The system supplies power and heat to five university buildings and, via a 5-km private transmission line, to a rest home, high school, and water treatment plant in Sendai City. Both AC and high voltage DC power are offered to meet customer requirements. The local grid provides supplemental power during peak periods.
Given the growing need for improved power quality and concern about overburdened grids and harmful emissions, these demonstrations offer valuable insight into the fuel cell’s ability to provide solid generating performance within a microgrid. Fuel cells deliver consistent, reliable, high quality power, high operating efficiencies, and clean and silent operation, making them an ideal microgrid generating technology.
Sandra Curtin is research director at Breakthrough Technologies Institute, an independent, Washington, D.C.-based educational organization that strives to identify and promote environmental and energy technologies. BTI’s program focus is on air quality, climate change, energy efficiency and energy independence. For more information, visit www.btionline.org or www.fuelcells.org.