Distributed Energy Systems have the capability to provide both combined heat and electrical power at one time. Overall Energy Efficiency usage is much higher with systems that implement CHP (combined heat & power). For example, an electrical coal power plant may be able to convert 30 - 50 % of the heat provided by coal into electrical energy, whereas a CHP power plant converts the majority or around 80 % into combined heating and electrical power [ 1. Lyons ]. Heating capabilities of value include space heating (or cooling), hot water production and industrial process heat from pressurized steam. However, much of the electrical power systems available to provide these additional heating capabilities are smaller in overall power capacity than regular sized electrical power plants ie coal, nuclear, etc. In general, three types of power technologies exist that provide the above mentioned heating and electrical power, those being Combustion Turbines, Reciprocating Engines & Fuel Cells. These 'mini power stations' are applicable in four different market areas - 1) Residential power & heating, 2) Small Commercial & Institutional Power, 3) Small - Large sized Industrial Systems and 4) Smaller Distributed electrical power for Electrical Utility Company. These systems operate at power capacities from several kW to 25 MW [ 2. The California Energy Commission ]. Fuel cell power systems include molten carbonate (MCFC) or solid soxide (SOFC) fuel cells that are made to mostly run off of natural gas (or related gases) whereas Microturbines & Reciprocating Engines can operate on a variety of fuels including natural gas, diesel or gasoline. Reciprocating Engines are similar in technology and comparable to vehicle engines that are spark or compression ignited. Both Microturbines and Reciprocating Engines provide additional heat provided as combustion waste gas streams that can be controlled with an additional Waste Heat Boiler or Duct Burner. Much of the energy in the combustion flue gases can also be reapplied toward energy (recombustion heating) using a system called a Recuperator. MCFC or SOFC Fuel Cell systems generate additional heat as well because they require that the natural gas be heated to temperatures from 650 - 1000 celcius. A Heat Recovery Steam Generator (HRSG) system is used to recover the heat used to convert the natural gas into hydrogen. The waste heat steam from these systems can also be used for room cooling using an Absorption Chilling System.
Commercial or institutional businesses usually prefer the ability to have heated water for various purposes such as what would fill the needs for a prison or hospital. Waste heat in this case must be cooled down to around 250 degrees Fahrenheit and then used to heat water, instead of directly being utilized by a Boiler or Heat Recovery system. One popular domestic fuel cell company called FuelCell Energy constructs larger sized fuel cells that are specially used to operate a hospital or prison. FuelCell Energy also assists in marketing fuel cells for the food and beverage industry such as breweries or bakeries, where not only hot water but process steam could be used for manufacturing purposes. In fact, there are a number of different manufacturing industries that already implement one of CHP power systems to use both for electricity and process steam. Some of these industries include Food Processing, Chemical/Pharmaceutical, Ceramic, Pulp & Paper, Mining and Textiles, just to name a few [ 3. Lyons ]. These types of industries already require heat for purposes such as distillation or drying, and since CHP systems are very energy efficient they are already used in hundreds if not thousands ofmanufacturing plants. More prevalent and widespread use of these power systems may help to create more jobs as well as save companies money on overall operating costs. These type of power systems, in addition, can provide additional savings in operation by using waste sources of gases such as from landfills, municipal sewage or biogas created from sources such as Anaerobic Digestors. Some companies even provide consulting services or related software to evaluate the use of equipment such as reciprocating engines using a defined amount and source of biogas or landfill gas. It is estimated that landfill gas would most likely provide 10 times or more the amount of power than from other biogas sources. Efforts by the government are being made to also help produce cleaner based CHP power from systems such as Reciprocating Engines by using cleaner burning fuels such as hydrogen, ethanol or by implementing cleaner technologies such as laser spark ignition or partial oxidation engines. In summary, drastic improvements in manufacturing efficiency as well as redudant - backup utility power can be realized with combined heat and power systems such as microturbines, reciprocating engines and fuel cells.
REFERENCES
1. "Combined Heat and Power Using Combustion Turbines" - Solar Turbines Inc. by Chris Lyons - 2006 or later
2. California Distributed Energy Resource Guide - DER Equipment - Combined Heat and Power
3. Same as Reference 1
Photos provided by the Picassa Web Album
KEYWORDS: Distributed Energy, Combined Heat and Power, Microturbines, Reciprocating Engines, Molten Carbonate Fuel Cells, Solid Oxide Fuel Cells, Industrial Process Steam Heat, Heat Recovery Steam Generator, Absorption Chillers, Distillation, Drying, Biogas, Landfill Gas, Wastewater Treatment Gas, Waste Heat Steam, National Fuel Cell Research Center
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