暖通空调文献翻译.doc

Development and Encouragement of renewable energy technologies1.1Project BackgroundSince its inception in the 1970s, the U.S. Department of Energy (DOE) has operated a substantial program in the development and encouragement of renewable energy technologies. As part of its ongoing effort to document the status and potential of these technologies, DOE, along with its national laboratories and support organizations, developed the first set of Renewable Energy Technology Characterizations (TCs) in 1989. The TCs were designed to respond to DOEs need for a set of consistent cost and performance data to support the development of the biennial National Energy Policy Plans. That first set of TCs was subsequently used to support the analyses that were performed in 1991 by DOE for the National Energy Strategy. The TCs were updated in 1993, but until now had not been formally published and existed only in draft form.The Electric Power Research Institute (EPRI), operating on behalf of its member utilities, has conducted a program in the assessment, evaluation and advancement of renewable power technologies since the mid-1970s. In that role, EPRI has been called upon by its members, and often by the energy community in general, to provide objective information on the status and outlook for renewables in prospective electric-power applications. Toward that aim, EPRI has joined with DOE to produce this set of Renewable Energy Technology Characterizations.This joint project is one of a number of activities that DOE and EPRI are conducting under the joint DOE-EPRI Sustainable Electric Partnership entered into formally by both organizations in October 1994. It builds upon a number of activities conducted jointly by DOE and EPRI over the past two decades.1.2Objectives, Approach and ScopePurpose and Audience: In response to growing interest in renewable power technologies and the need for consistent, objective assessments of technology performance and costs, DOE and EPRI collaborated to prepare the Renewable Energy Technology Characterizations (TCs) presented in this document. Together, through this document, DOE and EPRI aim to provide for the energy community and the general public an objective picture of the status and expectations for the renewable power technologies in electric-power applications in the United States. These TCs represent a consensus between DOE and EPRI on the current status and projected development path of five renewable electricity generating technologies: biomass, geothermal, photovoltaics, solar thermal and wind. In addition, recognizing the role that storage can play in enhancing the value of some renewable power plants, a TC for storage technologies, with a strong emphasis on batteries, is included in an appendix. The TCs can serve two distinct purposes. First, they are designed to be a reference tool for energy-policy analysts and power-system planners seeking objective cost and performance data. Second, the extensive discussions of the assumptions that underlie the data provide valuable insights for R&D program planners as they strive to prioritize future R&D efforts.Approach: Building on the best available information and experience from many years of direct involvement in the development and assessment of renewable energy technologies, experts from DOE, its national laboratories and support organizations prepared characterizations of the major renewable technologies. These were subjected to in-depth review by EPRI technical staff in renewables and selected outside reviewers, and then discussed at length in two technical workshops involving the writers and the reviewers. The characterizations were then revised, reflecting discussions at and subsequent to the workshops, resulting in this consensus document. In some cases, EPRI staff participated in preparation of overview sections.Document Scope: The TCs do not describe specific products or hardware configurations. They describe typical system configurations at five year increments through the year 2030, based on a projected evolution of the technologies during 1-2 that timeframe. They often portray changes in expected technology configuration over time. Allowing a changing configuration ensures that, in each timeframe discussed, the TC represents the most cost-effective configuration projected to be available in that timeframe. For example, the solar thermal power tower evolves from a hybrid plant with a conventional receiver to a solar-only plant with an advanced receiver. The TCs do not attempt to pick winners among a variety of choices. In that spirit, thin film PV systems are, for example, described only in a generic way, not specifying any particular thin film technology in any given timeframe. This view of the technology future mirrors the R&D portfolio approach that DOE takes, allowing the technology itself and the marketplace to determine winners and losers.Each TC should be thought of as a description of that technology in a particular application, typically as a gridconnected system for bulk power supply. However, some TCs do briefly describe other applications that could use substantially the same technology configuration.These TCs differ from EPRIs Technical Assessment Guide (TAG) in that they provide more extensive discussions of the expected technology evolution through 2030. However, the cost and performance data presented here are being used as a basis for TAG revisions that are currently in progress.Similar to the TAG, these TCs do not describe a recommended economic analysis methodology, but instead describe various approaches that could be taken to calculate levelized cost of energy or other appropriate financial figures of merit. These approaches span a range of possible ownership scenarios in a deregulated utility environment.Cautionary Note: The cost and performance information presented represent the best judgments of the individuals involved in the preparation and review of this document. As these technologies enter the commercial marketplace, normal competitive forces and commercial experience may have impacts that are difficult to predict at this time. For example, there are indications that prices for some conventional power-plant components and associated engineering services are dropping as competition in power generation becomes more widespread. Based on very recent commercial experience, this trend is already reflected in the geothermal-hydrothermal flash-steam plant costs presented in this document. Similar cost impacts may be observed in other renewable power plants employing conventional thermal generation components once the technologies become established sufficiently to attract multiple commercial suppliers. Readers are urged to use caution in applying numerical data from this document in commercial situations without consulting engineering firms actively involved in the commercial marketplace.Relationship to Ongoing Renewables Programs at DOE and EPRIThe technologies discussed in this document are considered by the renewables community, and by the managements of the DOE and EPRI renewables programs, to have good potential for contributing significantly to the U.S. electrical energy supply. Consequently, these technologies continue to receive technical and market-development support within the programs of DOE and EPRI. Of course, there is no guarantee that all of these technologies will develop and contribute as projected in this document. Rather, their individual prospects and roles will depend not only on the degree of support received, but also on the pace of progress and on societal needs and priorities. Ultimately, the marketplace, reflecting both commercial and societal forces, will decide.Development-Support AssumptionThe projected progress for these technologies is based on the assumption that robust programs continue in both technology and market development. In general, these programs need both public and private sector support, with the balance shifting more toward the commercial sector as technical maturity is approached. If support for a particular technology is curtailed, then the projected progress almost certainly will not occur.1.3Generic Benefits and IssuesThe benefits of using renewable energy resources are many. Most of these benefits arise from their virtually inexhaustible nature. Solar and wind resources are replenished on a daily basis. Biomass can be grown through managed agricultural programs to provide continuous sources of fuel. Geothermal power is extracted from the virtually unlimited thermal energy in the earths crust. Renewable energy resources are broadly available across the U.S. Certain regions, however, tend to have more accessible resource of one type than another. Figure 1 illustrates this diversity. For example, in the Midwest, biomass and wind resources are excellent, as is the solar radiation needed for flat-plate photovoltaics. In the Southwest, high levels of direct normal insolation are ideally suited to solar thermal and sunlight-concentration photovoltaic technologies. Geothermal resources are concentrated in the western parts of the U.S. The availability of each of the renewable resources is explored further in the technology overviews in this document.The benefits of renewable energy extend beyond abundance and diversity. As indigenous resources, they foster both local control and economic growth. An investment in renewable energy contributes to local economic security. In addition, the incorporation of renewables in a generation portfolio may reduce the risks associated with fluctuating fossil-fuel prices and supplies.As renewable energy technologies become more cost-competitive, their true economic benefits are being realized. Since many renewable energy plants do not need to be built in large scale to achieve the lowest possible plant costs, they can be built in size increments proportionate to load growth patterns and local needs. This is often referred to as their modularity. Given their smaller size, they can also be located closer to the customer load, reducing infrastructure costs for transmission and distribution, and helping to guarantee local power reliability and quality. Such “distributed” applications appear to have a potentially high economic value beyond just the value of the electricity generated.Several of the renewable energy technologies, namely photovoltaics, solar-thermal and wind, produce no emissions during power generation. Biomass plants, with a properly managed fuel cycle and modern emission controls, produce zero net carbon emissions and minimal amounts of other atmospheric effluents. The situation is much the same for geothermal plants. When these technologies displace fossil fuels, they avoid emissions that would otherwise be generated. With the growing concern about climate change and carbon emissions, renewable energy technologies can be significant contributors to global efforts to reduce greenhouse-gas emissions.The value of renewable-generated electricity is determined in part by the time of day at which the electricity is delivered to the grid and also by the probability that it will be available when needed. For example, solar output tends to follow utility summer-peak loads in many locations. Because power delivered during peak periods is more valuable to the utility system, renewable energy technologies can provide high value electricity and can be significant contributors to a reliable power supply system at critical times in those regions. Biomass, geothermal and fossil-hybrid renewable systems are fully dispatchable and compete most closely with conventional fuel-based systems. In some cases, such as the solar-thermal power tower with hot salt storage, energy-storage capability may be included economically. In these cases, the degree of dispatchability achieved depends on the amount of storage included. Intermittent systems, such as wind and solar without storage, will have value as determined primarily by the time of day and year at which electricity output is available.Further discussions of the issue of value are contained throughout this document. It is important to realize that the proper use of financial models to determine project attractiveness requires accurate projections about the value to customers of the power from that system. In most cases, the relative merit of a particular renewable power technology is not determined solely by a levelized cost of energy.Overall Perspectives on the Renewable TechnologiesWhile each of the characterized renewable technologies is discussed in detail in this document, the following summary presents an overview of current status and applications for each.Biomass: The use of forestry and agricultural residues and wastes in direct-combustion systems for cogeneration of electricity and process heat has been a well-established practice in the forest-products industry for many years. Useof these feed stocks in utility electric power plants has also been demonstrated in several areas of the country with access to appropriate fuels, in general with acceptable technical performance and marginal economics. The marginal economics are due to the small size of many of the existing plants and the consequent high operating costs and low efficiencies. Also, fuel shortages have often driven fuel prices up and made operation too expensive. The larger-sized plants, in the 50 MW range rather than the 10-to-25 MW size range of many projects built in the 1980s, have e e economics that are acceptable when fuel costs are close to $1/MMBtu, or when steam or heat from the direct combustion biomass boiler is also a valued product. In addition to activity with current technology, development is proceeding on advanced direct-combustion systems.One technology can use direct combustion of biomass fuels today without incurring the capital expense of a new boiler or a gasification combined-cycle system. This technology is biomass co-firing, wherein biomass is co-fired, or burned together, with coal in existing power plants. Though it does not increase total power generation, this mode of operation can reduce power-plant emissions and serve as a productive use for a waste stream that requires disposal in some way. Co-firing can be carried out as a retrofit, often with very low incremental capital and O&M costs. Biomass co-firing has been successfully demonstrated in a number of utility power plants, and is a commercially available option in locations where appropriate feed stocks are available. 1-5 Biomass gasification and subsequent electricity generation in combustion-turbine or combined-cycle plants is also being pursued. This mode of operation can be more attractive than direct combustion because of (a) potentially higher thermal efficiency, (b) the ability to maintain high performance in systems over a wide range of si