Five Ways to Green Existing Power Plants

By: Thomas Blakeslee, The Clearlight Foundation

Our existing fleet of fossil-fueled power plants represents a massive investment. With permits and infrastructure already in place, conversion upgrades can produce fast results at greatly reduced cost compared to new construction. Here are some ideas:

1. Cofire Biomass with Coal
Biomass and wood waste from the local area can be mixed in with coal up to 10 or 20 percent. Since the next crop of biomass will take in as much CO2 as was emitted, it is considered carbon neutral. Biomass also has very low sulfur and mercury content and reduces NOx, so cofiring can help meet emissions limits. Fuel and maintenance costs are often significantly lowered. Georgia Power’s conversion of its Mitchel Plant, for example, is expected to lower fuel and maintenance costs by 30 percent.

2. Use Biocoal
Biomass is more expensive to ship than coal because of its 30 percent lower energy density. It also must be protected from rain and cannot be easily pulverized like coal. Torrefaction, a process similar to coffee roasting, can convert biomass into biocoal, which can be shipped, stored, pulverized and burned just like coal. Torrefaction plants along the train tracks or rivers normally used to supply coal can convert locally grown biomass to biocoal and fill the same vehicles now used to deliver coal. Plant modifications are therefore unnecessary. Torrefaction can increase the energy density of biomass to about 11,000 Btu/lb while making it waterproof and friable.

3. Install Biomass Gasifiers
Biomass gasifiers can be located anywhere on the property to produce syngas, which is then piped to burners installed in the coal boilers. As with natural gas conversion, only a brief shutdown is required for installation. Direct coal firing is still possible if desired. Fluidized bed gasifiers are extremely efficient and can work with a wide variety of feedstocks including biomass and municipal waste.

4. Solar Preheating of Boiler Water
Solar thermal preheating of boiler water efficiently captures the energy of the sun and reduces fuel consumption. Solar heating peaks in the middle of the day but is ineffective at night. By using the sun to preheat water, fuel requirements are reduced by an amount equal to the heat captured. It is particularly effective on the same bright sunny days that maximize air conditioning loads. Carbon credits and investment credits are available. Parabolic troughs that track the sun can increase the efficiency of energy capture.

5. Sell waste energy
Combined Heat and Power (CHP) plants achieve up to 90 percent overall efficiency by selling waste power instead of disposing of it in cooling towers or streams. Existing plants can be modified to do the same thing. Hot steam can be sold to nearby Kilns, ethanol and drying plants and then passed on as hot water to lower temperature applications like Cold storage, greenhouses and fishponds. In Denmark 53 percent of the power plants also sell their waste heat. Many towns have a hot water or steam loop that distributes heat and returns the preheated water to the boiler Recent improvements in insulation and leak detection have made long distance heat delivery practical. In one installation in Denmark hot water is sent through insulated pipes 30 miles with only 10 percent loss.

After serving for three years in the U.S. Navy, Thomas R Blakeslee earned a degree from the California Institute of Technology in Pasadena, California in 1962. After working for IT&T in Antwerp, Belgium, he moved to Silicon Valley in California where he helped found several startup companies as Engineering Vice President. In 1980 he used founded Orion Instruments Inc., where he served as President and then Chairman of the Board until he retired in 1998. A prolific inventor, he holds patents in such diverse fields as photography, hydraulics, electronic circuits, information display, digital telephony, instrumentation and vehicle guidance.

 The Clearlight Foundation is a non-profit organization that invests in alternative energy and other socially useful companies and issues cash grants to individuals who are working effectively for change. Global warming and pollution caused by fossil fuel burning are a particular focus. The Clearlight Foundation seeks to encourage development of sustainable energy technologies and policies and is especially interested in the environmental effects of the emerging economies of China and India.

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