Showing papers on "Renewable energy published in 1997"

Renewable methane from anaerobic digestion of biomass.

Abstract: Production of methane via anaerobic digestion of energy crops and organic wastes would benefit society by providing a clean fuel from renewable feedstocks. This would replace fossil fuel-derived energy and reduce environmental impacts including global warming and acid rain. Although biomass energy is more costly than fossil fuel-derived energy, trends to limit carbon dioxide and other emissions through emission regulations, carbon taxes, and subsidies of biomass energy would make it cost competitive. Methane derived from anaerobic digestion is competitive in eAciencies and costs to other biomass energy forms including heat, synthesis gases, and ethanol. 7 2000 Elsevier Science Ltd. All rights reserved.

Unit sizing and control of hybrid wind-solar power systems

Abstract: The aim of this paper is to provide the core of a CAD/CAA tool that can help designers determine the optimal design of a hybrid wind-solar power system for either autonomous or grid-linked applications. The proposed analysis employs linear programming techniques to minimize the average production cost of electricity while meeting the load requirements in a reliable manner, and takes environmental factors into consideration both in the design and operation phases. While in autonomous systems, the environmental credit gained as compared to diesel alternatives can be obtained through direct optimization, in grid-linked systems emission is another variable to be minimized such that the use of renewable energy can be justified. A controller that monitors the operation of the autonomous/grid-linked systems is designed. Such a controller determines the energy available from each of the system components and the environmental credit of the system. It then gives details related to cost, unmet and spilled energies, and battery charge and discharge losses.

Towards a Standard Methodology for Greenhouse Gas Balances of Bioenergy Systems in Comparison with Fossil Energy Systems

Abstract: In this paper, which was prepared as part of IEA Bioenergy Task XV (“Greenhouse Gas Balances of Bioenergy Systems”), we outline a standard methodology for comparing the greenhouse gas balances of bioenergy systems with those of fossil energy systems. Emphasis is on a careful definition of system boundaries. The following issues are dealt with in detail: time interval analysed and changes of carbon stocks; reference energy systems; energy inputs required to produce, process and transport fuels; mass and energy losses along the entire fuel chain; energy embodied in facility infrastructure; distribution systems; cogeneration systems; by-products; waste wood and other biomass waste for energy; reference land use; and other environmental issues. For each of these areas recommendations are given on how analyses of greenhouse gas balances should be performed. In some cases we also point out alternative ways of doing the greenhouse gas accounting. Finally, the paper gives some recommendations on how bioenergy systems should be optimized from a greenhouse-gas-emissions point of view.

Energy After Rio: Prospects and Challenges

Abstract: The document presents a review of international progress made in sustainable development as a result of the UN Conference on Environment and Development held in June 1992 in Rio de Janeiro and other major UN conferences since. Subject headings are: energy and major global issues (poverty, gender disparity, population; undernutrition and food; health; acidification; climate change land degradation; energy and the economy; energy and security; UN conferences on small island development states and Habitat II; global implications for energy); new opportunities in energy demand, supply and systems (energy efficiency and materials efficiency; renewable and clean fossil fuel technologies; fuels and stoves for cooking); sustainable strategies (global energy strategies and their implications); making it happen: energy for sustainable development (policy considerations, improving the economic framework; prospects for energy technology market leadership in the developing world; the time for sustainable energy has come). 440 refs., 34 figs., 14 tabs., 1 app.

PV-diesel hybrid energy systems for remote area power generation — A review of current practice and future developments

Abstract: The continuous decline of costs for renewable energy technology, together with the establishment of a mature alternative energy industry, has led to the increased utilisation of renewable energy sources for remote area power generation. Rural households in industrialised and less developed countries attach high value to a reliable supply of electricity even if its capacity is limited. The paper reviews the current state of the design and operation of stand-alone PV-diesel hybrid energy systems. It highlights future developments, which have the potential to increase the economic competitiveness of such systems and their acceptance by the user.

Sizing and techno-economical optimization for hybrid solar photovoltaic/wind power systems with battery storage

Abstract: A general methodology is presented for the sizing and optimization of renewable power supply systems, including hybrids such as those with solar photovoltaic and wind power components. The technical and economic optimum configurations are found by reference to periods over which the average resource (e.g. wind/solar) is least or the average load demand is greatest. For stand-alone systems, the annual autonomy is an important further design factor. This is the fraction of time for which the specified load can be met. The optimization seeks the least expensive system configuration which achieves the required autonomy level. It is the autonomy level which largely determines the size of battery storage capacity required. A system performance simulation procedure, with an hourly time-step, is used to obtain the autonomy levels of potentially optimum arrangements as the battery size is varied. Illustrative examples of the use of the method employ annual and monthly averaging periods, although any other period may be used. Data refer to the particular location and load pattern for an existing hybrid system, but the method is quite generally applicable. © 1997 by John Wiley & Sons, Ltd.

Measuring the long-run fuel demand of cars: separate estimations of vehicle stock, mean fuel intensity, and mean annual driving distance.

Abstract: 1. The Car Energy-Use Problem Since the first so-called "oil crisis" in the early 1970s, a large number of energy demand studies have been carried out (see Dahl and Sterner, 1991a,b, or Goodwin, 1992, for surveys of petrol demand studies). In the 1970s oil imports per se were, both in the USA and Europe, perceived as a major externality, and energy prices were designed to restrain oil use; environmental problems, including the greenhouse effect, are perceived as major problems for all energy-using sectors in the 1990s (see, for example, Barker ?i a/., 1995). As is well known, C02 is considered the most important greenhouse gas, and C02 emissions from the transport sector are approximately proportional to fossil fuel use. Since the transport sector accounts for as much as 35 per cent of fossil fuel use, emissions from this sector are obviously important. However, it is not possible to control C02 using catalytic converters or other available techniques. Alternatives for decreasing traffic related C02 emissions are to decrease overall travel (by reducing the number of cars or the average driving distance per car), increase fuel efficiency, or change to a fuel based on renewable energy resources (or to a hydrogen or electricity system with low reliance on fossil fuels). In this study, we examine aspects of car fuel use that bear on the first two alternatives. We consider primarily long-run estimates, because of inertia in the size and characteristics of the vehicle stock.

Nature and technology of geothermal energy: A review

Abstract: Geothermal energy is the energy contained as heat in the Earth's interior. The paper describes the internal structure of the Earth together with the heat transfer mechanisms inside the mantle and crust. It also shows the location of geothermal fields on specific areas of the Earth. The Earth's heat flow and geothermal gradient are defined, as well as the types of geothermal fields, the geologic environment of geothermal energy, and the methods for geothermal exploration Geothermal energy, as natural steam and hot water, has been exploited for decades to generate electricity, both in space heating and industrial processes. The geothermal electrical installed capacity in the world is 7173.5 MWe (December 1996), and the electrical energy generated is 38 billion kW h/year, representing 0.4% of the world total electrical energy which was 13,267 billion kWh in 1995. The thermal capacity in non-electrical uses (greenhouses, aquaculture, district heating, industrial processes) is 8664 MW1 (end of 1994). Electricity is produced with an efficiency of 10–17%, and the geothermal kWh is generally cost-competitive with conventional sources of energy, in the range 3–12 US cents/kWh. The geothermal electrical capacity installed in the world is probably comparable with that from biomass. but almost twice that from solar or wind sources summed together. In developing countries, where total installed electrical power is still low, geothermal energy can play a significant role: in El Salvador 15% of electricity comes from geothermal steam, 15% in Nicaragua. 21% in the Philippines, and 6% in Kenya and Costa Rica. Financial investments in geothermal electrical and non-electrical uses worldwide are summarised. Present technology makes it possible to control the environmental impact of geothermal exploitation. The future use of the geothermal energy from advanced technologies such as the exploitation of geopressured reservoirs, hot dry rock systems and magma bodies is briefly discussed. While the viability of hot dry rock technology has been proved., research and development are still necessary for the other two sources. Finally, a brief discussion follows on training of specialists, geothermal literature, on-line information, and geothermal associations. © 1997 Published by Elsevier Science Ltd

Renewable energy technologies in Africa

Abstract: * Contents * Introduction * PART I: The Background * 1. The Energy Sector in its Geo-Political and Socio-Economic Setting * PART II: The Development and Role of Renewable Energy Technologies in Africa * 2. Bio-energy * 3. Solar Energy * 4. Wind Energy * 5. Small Hydro Technologies * PART III: Factors influencing the Dissemination of Renewable Energy Technologies and Strategies for Future Development * 6. Institutional Development * 7. Financial and Economic Issues * 8. Organization, Management and Maintenance * 9. Human Resource Development and Retention * 10. Equity * 11. Environment * PART IV: Policy Recommendations

Integrated power source layered with all polymer rechargeable batteries, solar cells, rf charger, charge control and indicator

Abstract: A self-contained, small, lightweight, portable, renewable, modular integrated power source (10) The power source consists of solar cells (18, 20) that are laminated onto a solid state polymer battery (12) which in turn is laminated onto a substrate containing circuits (26) which manage the polymer battery charging Charging of the battery can occur via solar energy or, alternatively, via RF coupling using external RF charging equipment (3O) or a hand held generator For added support, the integrated power source is then bonded to an applications housing or structure This integrated power source can independently power the electronic application It can also serve as casing or housing by taking the shape of the application enclosure

Photovoltaic Conversion of Concentrated Sunlight

Abstract: The potential of solar power as a viable source of renewable energy has been expanded by the recent achievements in sunlight concentration techniques described in this book, which provides a comprehensive treatment of the issues involved in this new efficient and cost-effective sustainable power resource. Fabrication problems for terrestrial and space photovoltaic installations and ohmic losses in solar cells are discussed, as are the semiconductor physics underlying photovoltaics. Concentrator solar cell structures and performance are noted. The book closes with a discussion on the optimization of solar photovoltaic power plants with concentrators. (UK)

Geothermal energy from the earth : Its potential impact as an environmentally sustainable resource

Abstract: ▪ Abstract Geothermal energy technology is reviewed in terms of its current impact and future potential as an energy source. In general, the geothermal energy resource base is large and well distributed globally. Geothermal systems have a number of positive social characteristics (they are simple, safe, and adaptable systems with modular 1–50 MW [thermal (t) or electric (e)] plants capable of providing continuous baseload, load following, or peaking capacity) and benign environmental attributes (negligible emissions of CO2, SOx, NOx, and particulates, and modest land and water use). Because these features are compatible with sustainable growth of global energy supplies in both developed and developing countries, geothermal energy is an attractive option to replace fossil and fissile fuels. In 1997, about 7,000 MWe of base-load generating capacity and over 15,000 MWt of heating capacity from high-grade geothermal resources are in commercial use worldwide. A key question is whether these levels can grow to ...

Integrated power source layered with thin film rechargeable batteries, charger, and charge-control

Abstract: A self-contained, small, lightweight, portable, renewable, modular integrated power source. The power source consists of a recharging means such as solar cells that are laminated onto a rechargeable energy source such as a solid state polymer battery which in turn is laminated onto a substrate containing circuits which manage the polymer battery charging. Charging of the battery can occur via solar energy or, alternatively, via RF coupling using external RF charging equipment or a hand held generator. For added support, the integrated power source is then bonded to an applications housing or structure. This integrated power source can independently power the electronic application. It can also serve as casing or housing by taking the shape of the application enclosure.

Future production and utilisation of biomass in Sweden: potentials and CO2 mitigation

Abstract: Swedish biomass production potential could be increased significantly if new production methods, such as optimised fertilisation, were to be used. Optimised fertilisation on 25% of Swedish forest land and the use of stem wood could almost double the biomass potential from forestry compared with no fertilisation, as both logging residues and large quantities of excess stem wood not needed for industrial purposes could be used for energy purposes. Together with energy crops and straw from agriculture, the total Swedish biomass potential would be about 230 TWh/yr or half the current Swedish energy supply if the demand for stem wood for building and industrial purposes were the same as today. The new production methods are assumed not to cause any significant negative impact on the local environment. The cost of utilising stem wood produced with optimised fertilisation for energy purposes has not been analysed and needs further investigation. Besides replacing fossil fuels and, thus, reducing current Swedish CO2 emissions by about 65%, this amount of biomass is enough to produce electricity equivalent to 20% of current power production. Biomass-based electricity is produced preferably through co-generation using district heating systems in densely populated regions, and pulp industries in forest regions. Alcohols for transportation and stand-alone power production are preferably produced in less densely populated regions with excess biomass. A high intensity in biomass production would reduce biomass transportation demands. There are uncertainties regarding the future demand for stem wood for building and industrial purposes, the amount of arable land available for energy crop production and future yields. These factors will influence Swedish biomass potential and earlier estimates of the potential vary from 15 to 125 TWh/yr.

Financing investments in renewable energy: The role of policy design and restructuring

Abstract: The costs of electric power projects utilizing renewable energy technologies are highly sensitive to financing terms. Consequently, as the electricity industry is restructured and new renewables policies are created, it is important for policymakers to consider the impacts of renewables policy design on project financing. This report describes the power plant financing process and provides insights to policymakers on the important nexus between renewables policy design and finance. A cash-flow model is used to estimate the impact of various financing variables on renewable energy costs. Past and current renewable energy policies are then evaluated to demonstrate the influence of policy design on the financing process and on financing costs. The possible impacts of electricity restructuring on power plant financing are discussed and key design issues are identified for three specific renewable energy programs being considered in the restructuring process: (1) surcharge-funded policies; (2) renewables portfolio standards; and (3) green marketing programs. Finally, several policies that are intended to directly reduce financing costs and barriers are analyzed. The authors find that one of the key reasons that renewables policies are not more effective is that project development and financing processes are frequently ignored or misunderstood when designing and implementing renewable energy incentives. A policy that is carefully designed can reduce renewable energy costs dramatically by providing revenue certainty that will, in turn, reduce financing risk premiums.

Green marketing, renewables, and free riders: increasing customer demand for a public good

Abstract: Retail electricity competition will allow customers to select their own power suppliers and some customers will make purchase decisions based, in part, on their concern for the environment. Green power marketing targets these customers under the assumption that they will pay a premium for ``green`` energy products such as renewable power generation. But renewable energy is not a traditional product because it supplies public goods; for example, a customer supporting renewable energy is unable to capture the environmental benefits that their investment provides to non-participating customers. As with all public goods, there is a risk that few customers will purchase ``green`` power and that many will instead ``free ride`` on others` participation. By free riding, an individual is able to enjoy the benefits of the public good while avoiding payment. This report reviews current green power marketing activities in the electric industry, introduces the extensive academic literature on public goods, free riders, and collective action problems, and explores in detail the implications of this literature for the green marketing of renewable energy. Specifically, the authors highlight the implications of the public goods literature for green power product design and marketing communications strategies. They emphasize four mechanisms that marketers can use to increase customer demand for renewable energy. Though the public goods literature can also contribute insights into the potential rationale for renewable energy policies, they leave most of these implications for future work (see Appendix A for a possible research agenda).

Energy from biomass and waste

Abstract: This publication has been published in the form of a website. To consult the publication you should unpack the complete zip-file first and next open the file inhoud.htm in a browser.

Crude Oil and Alternate Energy Production Forecasts for the Twenty-First Century: The End of the Hydrocarbon Era

Abstract: Predictions of production rates and ultimate recovery of crude oil are needed for intelligent planning and timely action to ensure the continuous flow of energy required by the world's increasing population and expanding economies. Crude oil will be able to supply increasing demand until peak world production is reached. The energy gap caused by declining conventional oil production must then be filled by expanding production of coal, natural gas, unconventional oil from tar sands, heavy oil and oil shales, nuclear and hydroelectric power, and renewable energy sources (solar, wind, and geothermal). Declining oil production forecasts are based on current estimated ultimate recoverable conventional crude oil resources of 329 billion barrels for the United States and close to 3 trillion barrels for the world. Peak world crude oil production is forecast to occur in 2020 at 90 million barrels per day. Conventional crude oil production in the United States is forecast to terminate by about 2090, and world production will be close to exhaustion by 2100.