Situation Analysis

Biopower (biomass-to-electricity power generation) is a proven electricity-generating option in the United States. With about 10 GW of installed capacity, biopower is the single largest source of non-hydro renewable electricity. Thi s installed capacity consists of about 7 GW derived from forest-product-industry and agricultural-industry residues, about 2.5 GW of municipal solid waste (MSW) generating capacity, and 0.5 GW of other capacity such as landfill gas-based production. The electricity production from biomass is being used, and is expected to continue to be used, as base load power in the existing electric-power system.

In the U.S., biopower experienced dramatic growth after the Public Utilities Regulatory Policy Act (PURPA) of 197 8 guaranteed small electricity producers (less than 80 MW) that utilities would purchase their surplus electricity at a price equal to the utilities' avoided-cost of producing electricity. From less than 200 MW in 1979, biopower capacity grew to 6 GW in 1989 and to today's capacity of 7 GW. In 1989 alone, 1.84 GW of capacity was added. The present low buyback rates from utilities, combined with uncertainties about industry restructuring, have slowed industry growt h and led to the closure of a number of facilities in recent years.

The 7 GW of traditional biomass capacity represents about 1% of total electricity generating capacity and about 8 % of all non-utility generating capacity. More than 500 facilities around the country are currently using wood or woo d waste to generate electricity. Fewer than 20 facilities are owned and operated by investor-owned or publicly-owne d electric utilities. The majority of the capacity is produced in Combined Heat and Power (CHP) facilities in th e industrial sector, primarily in pulp and paper mills and paperboard manufacturers. Some of these CHP facilities hav e buyback agreements with local utilities to purchase net excess generation. Additionally, a moderate percentage o f biomass power facilities are owned and operated by non-utility generators, such as independent power producers, tha t have power purchase agreements with local utilities. The number of such facilities is decreasing somewhat as utilities buy back existing contracts. To generate electricity, the stand-alone power production facilities largely use non-captive residues, including wood waste purchased from forest products industries and urban wood waste streams, used woo d pallets, some waste wood from construction and demolition, and some agricultural residues from pruning, harvesting , and processing. In most instances, the generation of biomass power by these facilities also reduces local and regiona l waste streams.

All of today's capacity is based on mature, direct-combustion boiler/steam turbine technology. The average size o f existing biopower plants is 20 MW (the largest approaches 75 MW) and the average biomass-to-electricity efficienc y of the industry is 20%. These small plant sizes lead to higher capital cost per kilowatt of installed capacity and to high operating costs as fewer kilowatt-hours are produced per employee. These factors, combined with low efficiencie s which increase sensitivity to fluctuations in feedstock price, have led to electricity costs in the 8-120/kWh range.

The next generation of stand-alone biopower production will substantially reduce the high costs and efficienc y disadvantages of today's industry. The industry is expected to dramatically improve process efficiency through the use of co-firing of biomass in existing coal-fired power stations, through the introduction of high-efficiency gasification -combined-cycle systems, and through efficiency improvements in direct-combustion systems made possible by th e addition of fuel drying and higher performance steam cycles at larger scales of operation. Technologies presently a t the research and development stage, such as Whole Tree Energy™integrated gasification fuel cell systems, an d modular systems, are expected to be competitive in the future.

Solar Stirling Engine Basics Explained

Solar Stirling Engine Basics Explained

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.

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