Resource Issues

Nationally, there appears to be a generous fuel supply. However, the lack of an infrastructure to obtain fuels and th e current lack of demonstrated technology to combust or gasify new fuels currently prevents utilization of much of thi s supply. According to researchers at Princeton University, of the total U.S. biomass residues available, half could b e economically used as fuel. They estimate that of the 5 exajoules (4.75 quads) of recoverable residues per year, on e third are made up of agricultural wastes and two thirds composed of forestry products industry residues (60% of which are mill residues). Urban wood and paper waste, recoverable in the amount of 0.56 EJ per year, will also be an important source. Pre-consumer biomass waste is also of increasing interest to urban utilities seeking fuels for co -firing, and such use also provides a useful service to the waste producer.

In the Southeast, biomass resources are plentiful, with 91.8 Tg of biomass fuel produced annually according to a study done in the mid-1980s by the Southeast Regional Biomass Energy Program. This translates to an estimated potentia l of 2.3 EJ of annual energy. North Carolina and Virginia are the biggest wood fuel producers (10.4 and 10.1 Tg, respectively). These residues come primarily from logging applications, culls and surplus growth, and are in the form of whole tree chips. In the western U.S., California is another major user of biomass energy. The California biomas s market grew from about 0.45 Tg in 1980 to about 5 Tg in the early 1990s. Feedstocks include mill residues, in-forest residues, agricultural wastes and urban wood waste.

Worldwide, biomass ranks fourth as an energy resource, providing approximately 14% of the world's energy needs . In developing countries, biomass accounts for approximately 35% of the energy used, and in the rural areas of thes e nations, biomass is often the only accessible and affordable source of energy [1,2]. There is much optimism tha t biomass will continue to play a significant, and probably increasing, role in the world's future energy mix. The basi s for this optimism stems from: (1) the photosynthetic productivity of biomass (conservatively an order of magnitud e greater than the world's total energy consumption); (2) the fact that bioenergy can be produced and used in a clean and sustainable manner; and (3) continuing advancements in biomass conversion technologies along several fronts . Increased bioenergy use, especially in industrialized countries, will depend on greater exploitation of existing biomass stocks (particularly residues) and the development of dedicated feedstock supply systems.

Because the future supply of biomass fuels and their prices can be volatile, many believe that the best way to ensur e future fuel supply is through the development of dedicated feedstocks. Large-scale dedicated feedstock supply systems designed solely for use in biomass power plants do not exist in the U.S. today on a commercial basis. The DO E Biomass Power Program (BPP) recognizes this fact, and a major part of the commercial demonstration program directly addresses dedicated feedstock supply issues. The 'Biomass Power for Rural Development' projects in New Yoik (willow), Iowa (switchgrass), and Minnesota (alfalfa) are developing the commercial feedstock infrastructure fo r dedicated feedstocks. The Minnesota Valley alfalfa producers project will involve the production of 700,000 tons/y r of alfalfa on 101,000 hectares (250,000 acres) of land. Unused agricultural lands in the U.S. (31.6 million ha in 1988) are primary candidates for tree plantations or herbaceous energy crops. About 4% of the land within an 80 km radius could supply a 100 MW plant operating at 70% capacity. Although, there are requirements for water, soil type and climate that will restrict certain species to certain areas, an assured regional fuel supply can reduce variability in prices.

Oak Ridge National Laboratory also has an extensive feedstock development and resource assessment program tha t is closely integrated with the DOE BPP. ORNL is responsible for development and testing of the switchgrass an d hybrid poplar species that are receiving intense interest by not only the commercial power project developers, but also the forest products industry.

Although not directly applicable, there are numerous examples in the agriculture and pulp and paper industries tha t serve to illustrate the feasible size of sustainable commercial biomass operations. There are over fifty pulp and paper mills in the U.S. that produce more than 500,000 tons/yr of product [3]. The feed into such plants is at least one third higher than the product output, with the additional increment being used for internal power and heat generation. Th e sugarcane industry also routinely harvests, transports, and processes large quantities of biomass. In the U.S. alone , more than a dozen sugar mills each process more than 1.3 million tons of cane per year, including four plants in Florida that process more than 2.25 million tons/yr [4]. Sweden and the other Scandinavian countries have long been leader s in the biomass energy arena. Currently, Sweden has over 16,500 hectares of farmland planted in willow for energ y use. The market for woody biomass for energy in Sweden has experienced strong growth, with a steady increas e equivalent to 3-4 TWh extra each year for the last five years. This equals one nuclear power station in aggregate every two years. Additionally, Denmark annually produces roughly 7 million tons of wheat straw that cannot, by law, b e burned in-field. This straw is increasingly being used for energy production. Thus, there is ample evidence that agricultural, harvest, transport, and management technologies exist to support power plants of the size contemplated.

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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