Showing papers on "Renewable energy published in 1999"

A realizable renewable energy future

Abstract: The ability of renewable resources to provide all of society's energy needs is shown by using the United States as an example. Various renewable systems are presented, and the issues of energy payback, carbon dioxide abatement, and energy storage are addressed. Pathways for renewable hydrogen generation are shown, and the implementation of hydrogen technologies into the energy infrastructure is presented. The question is asked, Should money and energy be spent on carbon dioxide sequestration, or should renewable resources be implemented instead.

Utilisation of biomass for the supply of energy carriers

Abstract: Because biomass is a widely available, renewable resource, its utilisation for the production of energy has great potential for reducing CO2 emissions and thereby preventing global warming. In this mini-review the `state of the art' of several fermentation processes is discussed, starting with the most advanced process of ethanol production. This is followed by methane production, an established process for waste water purification which is gaining more attention because of the inherent energy production. Subsequently ABE fermentation is discussed and finally the biological production of hydrogen. The last section proposes a new way to assess and compare the different processes by relating their merit to `work content' values and `lost work' instead of the combustion values of their products. It is argued that, especially when dealing with energy from biomass, the application of this methodology will provide a uniform valuation for different processes and products. The described fermentation processes enable the supply of pure energy carriers, either gaseous or liquid, from biomass, yet the introduction of these processes is hampered by two major problems. The first is related to technological shortcomings in the mobilisation of fermentable components from the biomass. The second, having a much greater impact, is linked with socio-economics: until full externality costs are attributed to fossil fuels, accounting for their role in pollution and global warming, the competitiveness of the processes described here will hardly stand a chance.

Prospects for building a hydrogen energy infrastructure

Abstract: ▪ Abstract About two-thirds of primary energy today is used directly as transportation and heating fuels. Any discussion of energy-related issues, such as air pollution, global climate change, and energy supply security, raises the issue of future use of alternative fuels. Hydrogen offers large potential benefits in terms of reduced emissions of pollutants and greenhouse gases and diversified primary energy supply. Like electricity, hydrogen is a premium-quality energy carrier, which can be used with high efficiency and zero emissions. Hydrogen can be made from a variety of feedstocks, including natural gas, coal, biomass, wastes, solar sources, wind, or nuclear sources. Hydrogen vehicles, heating, and power systems have been technically demonstrated. Key hydrogen end-use technologies such as fuel cells are making rapid progress toward commercialization. If hydrogen were made from renewable or decarbonized fossil sources, it would be possible to have a large-scale energy system with essentially no emissio...

Probabilistic performance assessment of autonomous solar-wind energy conversion systems

Abstract: This paper describes the development of a general probabilistic model of an autonomous solar-wind energy conversion system (SWECS) composed of several wind turbines (wind farm), several photovoltaic (PV) modules (solar park), and a battery storage feeding a load. The model takes into consideration outages due to the primary energy fluctuations and hardware failure. It allows the simulation of wind farms and solar parks containing either identical or different types of wind turbines and PV modules with the load being fed from either the renewable sources, or the battery storage, or both. A methodology is also presented to determine an upper limit on the size of the battery storage required to satisfy a given load profile taking into consideration the charging/discharging of the batteries.

The Viability of Thermal Energy Storage

Abstract: With rising energy costs and an increasing demand for renewable energy sources, thermal energy storage (TES) systems are becoming an interesting option. TES is a key component of any successful thermal system and a good TES should allow minimum thermal energy losses. In this study, various ways of thermal conservation are outlined and discussed, both theoretical and experimental. In this respect, the TES systems and their practical applications and some selection criteria have also been given.

Global CO2 recycling - Novel materials and prospect for prevention of global warming and abundant energy supply

Abstract: CO2 emissions which induce global warming, increase with the growth of the economic activity. It is, therefore, impossible to decrease emissions only by energy savings and by improvements of the energy efficiency. Global CO2 recycling can solve this problem and supply abundant renewable energy. Global CO2 recycling consists of three districts: (i) in deserts, all necessary electricities are generated by solar cells; (ii) on coasts close to the deserts, the electricity is used for production of H2 by seawater electrolysis, H2 is converted to CH4 by the reaction with CO2 and liquefied CH4 is transported to energy consuming districts; (iii) at energy consuming district, after CH4 is used as a fuel, CO2 is recovered, liquefied and transported to the coasts close to the deserts. A CO2 recycling plant for substantiation of our idea has been built on the roof of our Institute (IMR) in 1996, using key materials tailored by us. The key materials necessary for global CO2 recycling are the anode and cathode for seawater electrolysis and the catalyst for CO2 methanation. Since the quantities of CO2 to be converted far exceed an industrial level, the system must be very simple and the rate of conversion must be very fast. These requirements are satisfied in our global CO2 recycling system. When global CO2 recycling is conducted on a large scale, the energies and costs required to form liquefied CH4 in our global CO2 recycling system are almost the same as those for production of LNG from natural gas wells. A project for field experimenting the global CO2 recycling using pilot plants in Egypt has been planned in cooperation with Egyptian scientists, engineers and industries.

Probabilistic performance assessment of wind energy conversion systems

Abstract: This paper describes the development of a general probabilistic model of an autonomous wind energy conversion system (WECS) composed of several wind turbines (wind farm) connected to a load and a battery storage. The proposed technique allows the simulation of wind farms containing identical or different wind turbines types and considers a bidirectional flow of power in and out of the battery. The model is based upon a simple procedure to estimate the joint probability distribution function of the total available wind power and that of the turbines operating modes due to hardware failure. A methodology is also developed to use the proposed model to determine an upper limit on the size of the battery storage required for a given number of turbines to satisfy the load with a certain expected energy not supplied (EENS). The model can also be used to evaluate the energy purchased from or injected to the grid in the case of grid-connected systems.

Cumulative energy demand for selected renewable energy technologies

Abstract: Calculation of Cumulative Energy Demand (CED) of various energy systems and the computation of their Energy Yield Ratio (EYR) suggests that one single renewable energy technology cannot be said to be the best. Due to the difference in availability of renewable energy sources, their suitability varies from place to place. Wind energy converters, solar water heating systems and photovoltaic systems have been analysed for different types of locations. Comparing the general bandwidth of performance of these technologies, however, the wind energy converters tend to be better, followed by solar water heating systems and photovoltaic systems.

Renewable energy education for sustainable development

Abstract: Rising international concern about global warming and the rapid development of the renewable energy industry over recent years has led to a need for multidisciplinary programs in energy studies. We have developed a postgraduate program in energy studies, which is based on the principles of ecologically sustainable development. This program combines work in energy technology with energy policy, energy economics and environmental and social issues. The program is offered on campus at Murdoch U Diversity and by external study, via the internet, throughout Australia and overseas. It has attracted considerable interest from students seeking to find new opportunities within the renewable energy industry. This paper outlines the philosophy of the energy studies program, its implementation and outcomes.

A Strategy for the Hydrogen Transition

Abstract: A rapid, practical, and profitable commercialization path for fuel cells and H2 can be executed by coordinating convergent trends in several industries. This strategy relies on existing technologies, can begin immediately, and proceeds in a logical and viable sequence. It has two preconditions: uncompromised ultralight-hybrid vehicles whose inherently high efficiency permits their fuel-cell stacks to rely on conveniently compact onboard tanks of compressed gaseous H2, making onboard liquid-fuel reformers unnecessary and uncompetitive; and integration of fuel-cell market development between vehicles and buildings. As a first step, fuel-cell co- or trigeneration could currently compete in many buildings by virtue of its thermal credit. It could yield even greater economic value wherever electric distribution grids are old or congested, or where other “distributed benefits” are important and rewarded. Its H2 could be made in the building by a mass-produced “hydrogen appliance”—either an offpeak electrolyzer or a natural-gas steam reformer. Next, the huge fuel-cell market in buildings (which use two-thirds of all U.S. electricity), supplemented by industrial niche markets, would soon cut fuel-cell costs to levels competitive in vehicles. Low-tractive-load Hypercars™ could adopt fuel cells at severalfold higher prices, hence several years earlier, than conventional cars. The general-vehicle market could then be opened to hydrogen by first using the spare offpeak capacity of buildings’ H2 sources to serve vehicles too—particularly vehicles whose drivers work or live in or near the same buildings. Further, those vehicles’ daytime use as plug-in ~20+-kWe power plants could repay a significant fraction of their lease cost. This building/vehicle integration could make gaseous-H2 fueling practical without first building a new upstream bulk-supply and distribution infrastructure. It would work better and cost less than onboard liquid-hydrocarbon reforming. Ultimately it could provide more than 3 TWe of U.S. generating capacity, enough in principle to displace virtually all central thermal power stations. As both stationary and mobile applications for fuel cells built volume and cut cost for dispersed but stationary reformer and electrolyzer appliances, those H2 sources would also start to be installed freestanding outside buildings. Before long, the growing H2 market would then justify further competition from upstream bulk supply, especially from climatically benign sources. Such options include converting hydroelectric dams (or other renewables) to “Hydro-Gen” plants that earn far higher profit by shipping each electron with a proton attached, and R.H. Williams’s concept of wellhead reforming of natural gas with CO2 reinjection. The latter option’s three possible profit streams—high-value hydrogen-fuel sales, enhanced hydrocarbon recovery, and potential carbonsequestration credits—are already attracting large energy companies. Its ~200-year climate-safe CH4 reserves (at roughly current rates of consumption) could also provide a long bridge to a fully renewable energy system. The diverse and dynamic portfolio of hydrogen sources—up- and downstream; renewable and nonrenewable; based on electrolysis, reforming, or other methods; and with small to no net climatic effect—would ensure healthy price competition and robust policy choices.

Willingness to Pay for Renewable Electricity: A Review of Utility Market Research

Abstract: As competition in the electric utility industry has become more widespread and federal legislation deregulating the utility industry more likely, utilities have become more concerned about actions they can take to help ensure the loyalty of their customers. National polls have, for 20 years, found majority preferences for renewable energy over other energy sources. This issue brief compiles and analyzes recent market research conducted by utility companies on customer interest in and willingness to pay for renewable electricity. Findings in the areas examined in this review are: Customers are favorable toward renewable sources of electricity, although they know little about them; Solar and wind are the most favored sources of electricity generation; Majorities of 52% to nearly 100% of residential customers said they were willing to pay at least a modest amount more per month on their electric bills for green power; their responses follow a predictable curve showing that percentages willing to pay more decline as cost increases. The residential market for green pricing is approximately 2% near program rollout at a $5/month price increment, and should increase slowly but steadily over time; Customers may view with favor, and be more willing to purchase electricity from, utilities that provide green power.