Showing papers on "Renewable energy published in 1991"

Fuel ethanol from cellulosic biomass.

Abstract: Ethanol produced from cellulosic biomass is examined as a large-scale transportation fuel. Desirable features include ethanol's fuel properties as well as benefits with respect to urban air quality, global climate change, balance of trade, and energy security. Energy balance, feedstock supply, and environmental impact considerations are not seen as significant barriers to the widespread use of fuel ethanol derived from cellulosic biomass. Conversion economics is the key obstacle to be overcome. In light of past progress and future prospects for research-driven improvements, a cost-competitive process appears possible in a decade.

Ethanol fuels: Energy security, economics, and the environment

Abstract: Problems of fuel ethanol production have been the subject of numerous reports, including this analysis. The conclusions are that ethanol: does not improve U.S. energy security; is uneconomical; is not a renewable energy source; and increases environmental degradation. Ethanol production is wasteful of energy resources and does not increase energy security. Considerably more energy, much of it high- grade fossil fuels, is required to produce ethanol than is available in the energy output. About 72% more energy is used to ‘produce a gallon of ethanol than the energy in a gallon of ethanol. Ethanol production from corn is not renewable energy. Its production uses more non- renewable fossil energy resources in growing the corn and in the fermentation/distillation process than is produced as ethanol energy. Ethanol produced from corn and other food crops is also an unreliable and therefore a non-secure source of energy, because of the likelihood of uncontrollable climatic fluctuations, particularly droughts which reduce crop yields. The expected priority for corn and other food crops would be for food and feed. Increasing ethanol production would increase degradation of agricultural land and water and pollute the environment. In U.S. corn production, soil erodes some 18- times faster than soil is reformed, and, where irrigated, corn production mines water faster than recharge of aquifers. Increasing the cost of food and diverting human food resources to the costly and inefficient production of ethanol fuel raise major ethical questions. These occur at a time when more food is needed to meet the basic needs of a rapidly growing world population.

A Review of Biomass Pyrolysis and Pyrolysis Technologies

Abstract: Biomass, as the only renewable source of fixed carbon, has attracted considerable attention as a renewable energy resource after the oil crises of the last 15 years. Of the variety of technologies available for converting biomass into more useful and valuable energy products, thermochemical processing and particularly pyrolysis have been investigated for the economic production of liquid fuels. The characteristics of pyrolysis processes, upgrading technologies and products are summarised in this overview paper in order to focus on the opportunities, constraints and requirements for successful implementation of these technologies in Europe.

An assessment of the available windy land area and wind energy potential in the contiguous United States

Abstract: Estimates of land areas with various levels of wind energy resource and resultant wind energy potential have been developed for each state in the contiguous United States. The estimates are based on published wind resource data and account for the exclusion of some windy lands as a result of environmental and land-use considerations. Despite these exclusions, the amount of wind resource estimated over the contiguous United States is surprisingly large and has the potential to supply a substantial fraction of the nation's energy needs, even with the use of today's wind turbine technology. Although this study shows that, after exclusions, only about 0.6% of the land area in the contiguous United States is characterized by high wind resource (comparable to that found in windy areas of California where wind energy is being cost-effectively developed), the wind electric potential that could be extracted with today's technology from these areas across the United States is equivalent to about 20% of the current US electric consumption. Future advances in wind turbine technology will further enhance the potential of wind energy. As advances in turbine technology allow areas of moderate wind resource to be developed, more than a tenfold increase in the wind energymore » potential is possible. These areas, which cover large sections of the Great Plains and are widely distributed throughout many other sections of the country, have the potential of producing more than three times the nation's current electric consumption. 9 refs., 12 figs., 13 tabs.« less

Introduction to materials science for solar energy conversion systems

Abstract: Several pathways for renewable energy conversion are introduced. Materials for specific solar energy applications have optical properties tailored to the requirements set by the radiation in our surroundings. This “natural” radiation is outlined, and the goals of materials science for several solar energy conversion systems are discussed.

Solar-hydrogen energy system : The choice of the future

Abstract: As a result of the foregoing study, the following conclusions are reached: (A) The solar–hydrogen energy system is environmentally far more compatible than the fossil-fuel system; it is actually the only solution for the carbon-dioxide-induced ‘greenhouse’ effect and its threatening consequences. (B) The utilization efficiencies of hydrogen are greater than those of fossil and synthetic fossil fuels; therefore, in the hydrogen-energy system, less energy will be required to perform the same services. (C) The solar-hydrogen energy system is the most cost-effective system if effective costs (the costs which society pays for the energy services) are taken into account. It is not only more cost-effective than the synthetic fossil-fuel system—it is even more cost-effective than the present fossil-fuel system. (D) Clean coal technologies could be used for thermal-energy generation, satisfying approximately 30% of the world's total energy needs. Such a system, which employs coal for thermal-energy generation, and hydrogen from renewable energy sources in electricity generation and transportation sectors, would be the least-cost energy system for the transition period. (E) Transition to the solar–hydrogen energy system could help to save our economy and our planet.The fuels that are being most favourably considered for the post-petroleum and natural-gas era, namely hydrogen (both gaseous and liquid) and coal and coal-derived synthetic fluid fossil-fuels, have been compared in this paper by taking into account production costs, external costs, and utilization efficiencies. The results show that hydrogen is a much more cost-effective energy carrier than coal or synthetic fossil-fuels. At the same time, and most importantly by far from our viewpoint, it is the most environmentally compatible of all.

Augmentation of thermal power stations with solar energy

Abstract: A new concept of integration of a solar concentrator field with a modern thermal power station is proposed. Such a configuration would utilise the existing equipment and infrastructure as a base load facility and solar energy to reduce the fuel consumption during periods of insolation. The methodology suggested involves feed water heating using a solar concentrator field and consequent reduction of steam extraction presently used for the purpose. Study of retrofit to a 210-MW coal-fired plant indicates that saving of fuel upto 24·5% during periods of insolation can be achieved for feed water heating upto the present level, which is to a temperature of 241°C. The annual saving in coal would be around 47,000 tons at an estimated cost of about Rs. 3 crores. A doubling of the savings, by heating to a higher temperature level of 330°C, is feasible with presently available solar technology. Areas needing detailed study for achieving such an integration are indicated. The control system required to allow for fluctuations in the solar output is outlined. It is felt that the proposed system, where solar energy contributes a small but significant fraction of the total output of the plant, would be easier to control than one where the total energy is provided by solar radiation. A preliminary estimate indicates that the proposed system may cost about half of a stand-alone solar plant with back-up fuel and with the same solar input. However site-specific studies need to be carried out to confirm these figures.

Assessment of research needs for wind turbine rotor materials technology

Abstract: Wind-driven power systems represent a renewable technology that is still in the early stages of its development and maturation. It is a renewable power technology that, during the course of its rapid evolution over the last decade, has accumulated significant, large-scale, utility-connected experience. The focus is on the need for improved knowledge of materials properties and advanced, economical, high volume manufacturing processes. The first chapter: (1) traces the evolution of wind power systems in the United States; (2) identifies the principle components of a power-generating wind turbine; and (3) presents a simplified description of the relationship between the power in the wind and the power flow through the turbine drive train, and describes the characteristics of the wind environment that impact both the short and long term structural integrity of wind turbines. The remaining chapters of this report explore and further define the need for improved materials properties, manufacturing processes, and control systems.

World potential of renewable energies

Abstract: A comprehensive analysis, region by region, of the actually accessible renewable energies at a given horizon, is presented. The same methodology as the one employed to derive ``proven fossil energy reserves`` from ``energy resources`` is adopted, in which resources are defined by quantitative information on physical potential, while reserves take into account technical and economical accessibility. As renewable resources are fluctuating with time and are diluted in space and not readily transportable or storeable, it is necessary to consider the presence of populations or activities near enough to be able to profit by these diluted and volatile energies.

Development of hot dry rock geothermal energy.

Abstract: Hot dry rock (HDR) geothermal energy, which utilizes the natural heat contained in low permeable rock mass, could be estimated to provide a great amount of energy for electricity. NEDO has been concentrating research efforts on developing HDR geothermal energy from 1985 under a renewable energy development program, named the Sunshine project. Required technology for developing HDR energy is summa-rized in this paper.This report will also focus on the results obtained in 1989 as well as a brief histry of the Hijiori project and recent R&D situation in America and Europe.

Indirect steam gasification of paper mill sludge waste

Abstract: The potential for recovering energy from renewable sources and organic waste products has been recognized for many years. In recent years, we have been confronted with the realization that fossil fuels--oil and gas in particular---are unrenewable and being depleted at an accelerated rate. Thus the need for an effective technology for utilizing renewable organic sources of energy is a prime consideration for U.S. energy policy. Paper mill biomass waste is representative of materials discharged from virgin pulp mills and recycle mills located throughout the United State. This paper reports that Manufacturing and Technology Conversion International (MTCI) has developed a unique process that reduces the volume of the solid wastes, destroys the chlorinated organics such as dioxins, and produces clean fuel gas for use in the mill as a replacement for natural gas.

Solar energy collection, concentration, and thermal conversion; A review

Abstract: The efficiency with which solar energy can be converted into more useful forms is one of the most important parameters concerning its utilization as a viable alternate source of energy. High efficiencies can be obtained by utilizing higher temperature working fluids. This in turn implies concentrating the intensity of sunlight using focussing type collectors. A review of the history of solar energy conversion and the types of collectors, particularly those which use concentrating techniques, is presented. The amount of solar energy available for focussing type collector systems is discussed. Potential applications of concentrated solar intensity are presented in this article. A description of a new and potentially highly efficient solar thermal to electric converter based on a solar sustained cesium plasma is presented. Photovoltaics are not discussed in any detail in this article.

Long-Term Potentials of Rational Energy use - The Unknown Possibilities of Reducing Greenhouse Gas Emissions:

Abstract: Many energy economists expect a further increase in energy demand of industrialized countries and, hence, a substantial shift to natural gas, nuclear power, and renewables to avoid climatic changes due to energy-related greenhouse gases. The judgement that feasible improvements of energy efficiency are limited to 30 to 40% is questioned by the author. The paper that argues the potentials of rational energy use are higher than 80% in the long term by improving the exergy efficiency (which is today less than 10%) and by decreasing the level of useful energy by reduced losses, substitution of energy-intensive processes, applying new materials, and intensified recycling of energy-intensive materials. Because of the unbalanced perception of the future potentials of rational energy use and of energy conversion technologies it is very likely that the high potentials for reducing the greenhouse gas emissions by improved energy efficiency will be underestimated.

Energy analysis and solar energy development in Cyprus

Abstract: This article reviews the application of solar energy technology in Cyprus and presents an energy analysis, including the use of solar energy, in the island. Cyprus has no conventional sources of energy and is dependent on imported oil. However, its geographical position is such that it is one of the countries where the potential for solar energy utilisation is very high. Cyprus began manufacturing solar water heaters in the early 1960s and today it produces more than 30 000 m2 of solar collectors yearly. It is estimated that more than 130 000 solar water heaters are in operation, which provide the equivalent of 9% of the total electricity consumption in the island, and corresponds, approximately, to 4% of the national energy consumption. However, the use of solar energy for space heating and cooling provides a further challenge because it does not appear to be economic under the climatic conditions and system design practices currently prevailing in Cyprus. The article provides a statistical analysis of the energy demand and identifies areas of further growth for solar energy technology.