Introduction:
Biopower technologies are proven electricity generation options in the United States, with 10 gigawatts of installed capacity. All of today's capacity is based on mature, direct-combustion technology.
Future efficiency improvements will include co-firing of biomass in existing coal fired boilers and the introduction of high-efficiency gasification combined-cycle systems, fuel cell systems, and modular systems.
A. Technologies:
Direct Combustion:
Direct combustion involves the burning of biomass with excess air, producing hot flue gases that are used to produce steam in the heat exchange sections of boilers. The steam is used to produce electricity in steam turbine generators.
Co-firing:
Co-firing refers to the practice of introducing biomass in high-efficiency coal fired boilers as a supplementary energy source.
Co-firing has been evaluated for a variety of boiler technologies including pulverized coal, cyclone, fluidized bed and spreader stokers.
For utilities and power generating companies with coal-fired capacity, co-firing with biomass may represent one of the least-cost renewable energy options.
Gasification:
Biomass gasification for power production involves heating biomass in an oxygen-starved environment to produce a medium or low calorific gas.
This "biogas" is then used as fuel in a combined cycle power generation plant that includes a gas turbine topping cycle and a steam turbine bottoming cycle.
Pyrolysis:
Biomass pyrolysis refers to a process where biomass is exposed to high temperatures in the absence of air, causing the biomass to decompose.
The end product of pyrolysis is a mixture of solids (char), liquids (oxygenated oils), and gases (methane, carbon monoxide, and carbon dioxide).
Anaerobic Digestion:
Anaerobic digestion is a process by which organic matter is decomposed by bacteria in the absence of oxygen to produce methane and other byproducts. The primary energy product is a low to medium calorific gas, normally consisting of 50 to 60 percent methane.
B. Market Issues:
Green Power Marketing:
Green power marketing provides choices in restructured electricity markets for electricity consumers to purchase power from renewable or environmentally preferred sources, such as biomass.
Green pricing allows customers to support a greater level of investment in renewable energy technologies by paying a premium on their electric bill to cover the incremental cost of the additional renewable energy. Both approaches can contribute to the growth of the biopower industry.
Combined Heat and Power (CHP):
Much of today's biopower is provided by CHP facilities located at forest product industry sites. CHP, also called cogeneration, achieves high efficiencies by using both the power and the excess heat from burning the biomass.
Modular Power Systems:
These small energy systems can be used in farm systems and, more generally, to provide power at or near a customer's site — a concept known as distributed generation.
Source:ONRL.GOV
© 2001 Mena Report (www.menareport.com)
