Showing papers on "Renewable energy published in 2007"
TL;DR: In this article, three major ways to utilize nanostructures for the design of solar energy conversion devices are discussed: (i) mimicking photosynthesis with donor−acceptor molecular assemblies or clusters, (ii) semiconductor assisted photocatalysis to produce fuels such as hydrogen, and (iii) nanostructure semiconductor based solar cells.
Abstract: The increasing energy demand in the near future will force us to seek environmentally clean alternative energy resources. The emergence of nanomaterials as the new building blocks to construct light energy harvesting assemblies has opened up new ways to utilize renewable energy sources. This article discusses three major ways to utilize nanostructures for the design of solar energy conversion devices: (i) Mimicking photosynthesis with donor−acceptor molecular assemblies or clusters, (ii) semiconductor assisted photocatalysis to produce fuels such as hydrogen, and (iii) nanostructure semiconductor based solar cells. This account further highlights some of the recent developments in these areas and points out the factors that limit the efficiency optimization. Strategies to employ ordered assemblies of semiconductor and metal nanoparticles, inorganic-organic hybrid assemblies, and carbon nanostructures in the energy conversion schemes are also discussed. Directing the future research efforts toward utiliza...
2,119 citations
TL;DR: This catalytic strategy for the production of 2,5-dimethylfuran from fructose (a carbohydrate obtained directly from biomass or by the isomerization of glucose) for use as a liquid transportation fuel may diminish the authors' reliance on petroleum.
Abstract: With petrol prices on the rise, biofuels are big news these days. For applications in the transportation sector, perhaps the best known liquid biofuel is biomass-derived ethanol. But ethanol has its limitations: it is highly volatile, absorbs water and has a low energy density. A team from the University of Wisconsin-Madison has developed a two-step catalytic process that can convert fructose into a potentially better liquid biofuel, 2,5-dimethylfuran (DMF). This has 40%-higher energy density and a higher boiling point than ethanol, and is not water soluble. Fructose can be made directly from biomass or from glucose and although there's some work needed before DMF production can be made commercially viable, this new catalytic process looks promising. Diminishing fossil fuel reserves and growing concerns about global warming indicate that sustainable sources of energy are needed in the near future. For fuels to be useful in the transportation sector, they must have specific physical properties that allow for efficient distribution, storage and combustion; these properties are currently fulfilled by non-renewable petroleum-derived liquid fuels. Ethanol, the only renewable liquid fuel currently produced in large quantities, suffers from several limitations, including low energy density, high volatility, and contamination by the absorption of water from the atmosphere. Here we present a catalytic strategy for the production of 2,5-dimethylfuran from fructose (a carbohydrate obtained directly from biomass or by the isomerization of glucose) for use as a liquid transportation fuel. Compared to ethanol, 2,5-dimethylfuran has a higher energy density (by 40 per cent), a higher boiling point (by 20 K), and is not soluble in water. This catalytic strategy creates a route for transforming abundant renewable biomass resources1,2 into a liquid fuel suitable for the transportation sector, and may diminish our reliance on petroleum.
2,033 citations
TL;DR: A review of modern biomass-based transportation fuels such as fuels from Fischer-Tropsch synthesis, bioethanol, fatty acid (m)ethylester, biomethanol, and biohydrogen are briefly reviewed in this paper.
1,505 citations
TL;DR: In this paper, the authors discuss the problems and perspectives of converting present energy systems into a 100% renewable energy system based on the case of Denmark, and the conclusion is that such development is possible.
1,274 citations
TL;DR: Most of the “new renewable energy sources” are still undergoing large-scale commercial development, but some technologies are already well established and fully competitive with motor gasoline and appropriate for replication in many countries.
Abstract: Renewable energy is one of the most efficient ways to achieve sustainable development. Increasing its share in the world matrix will help prolong the existence of fossil fuel reserves, address the threats posed by climate change, and enable better security of the energy supply on a global scale. Most of the "new renewable energy sources" are still undergoing large-scale commercial development, but some technologies are already well established. These include Brazilian sugarcane ethanol, which, after 30 years of production, is a global energy commodity that is fully competitive with motor gasoline and appropriate for replication in many countries.
1,234 citations
TL;DR: In this paper, the state of the art of phase change materials (PCMs) for storing solar energy is discussed. But, prior to the large-scale practical application of this technology, it is necessary to resolve numerous problems at the research and development stage.
Abstract: The continuous increase in the level of greenhouse gas emissions and the climb in fuel prices are the main driving forces behind efforts to more effectively utilise various sources of renewable energy. In many parts of the world, direct solar radiation is considered to be one of the most prospective sources of energy. However, the large-scale utilisation of this form of energy is possible only if the effective technology for its storage can be developed with acceptable capital and running costs. One of prospective techniques of storing solar energy is the application of phase change materials (PCMs). Unfortunately, prior to the large-scale practical application of this technology, it is necessary to resolve numerous problems at the research and development stage. This paper looks at the current state of research in this particular field, with the main focus being on the assessment of the thermal properties of various PCMs, methods of heat transfer enhancement and design configurations of heat storage facilities to be used as a part of solar passive and active space heating systems, greenhouses and solar cooking.
1,173 citations
TL;DR: In this article, the authors presented an overview of the current and projected energy scene and presented the size of respective wind and solar farms that would be required for each of the five countries under discussion to meet their year 2020 energy demands.
Abstract: Energy is inevitable for human life and a secure and accessible supply of energy is crucial for the sustainability of modern societies. Continuation of the use of fossil fuels is set to face multiple challenges: depletion of fossil fuel reserves, global warming and other environmental concerns, geopolitical and military conflicts and of late, continued and significant fuel price rise. These problems indicate an unsustainable situation. Renewable energy is the solution to the growing energy challenges. Renewable energy resources such as solar, wind, biomass, and wave and tidal energy, are abundant, inexhaustible and environmentally friendly. This article provides an overview of the current and projected energy scene. Five countries, that presently have a significant impact on global energy situation, have been studied in this work. These include China, India, Russia, UK and USA. Together the present energy budget of these countries is roughly half that of the globe. Four of the above five countries that are discussed in this work—China, India, UK and USA are all net importers of energy and are heavily dependent on imports of fuel to sustain their energy demands. Their respective local oil reserves will only last 9, 6, 7 and 4 years, respectively. China, the emerging economy in the world, is however making exemplary development in renewable energy—in 2004 renewable energy in China grew by 25% against 7–9% growth in electricity demand. While in the same year, wind energy in China saw a growth of 35%. China is also leading the global solar thermal market as it has already installed solar collectors over 65 million square meters, accounting for more than 40% of the world's total collector area. This article quantifies the period of exhaustion of the current major energy sources, i.e. coal, oil, gas and nuclear fissile material. Projected demand for energy is also presented and a feasibility of switch over to renewable energy is discussed. The article also presents the size of respective wind- and solar farms that would be required for each of the five countries under discussion to meet their year 2020 energy demands. It has been found that to meet 50% of the total energy demands the proposed area for collection of solar and wind energy by means of ultra-large scale farms in fact will occupy a mere fraction of the available land and near-offshore area for the respective countries, e.g. a solar PV electricity farm of 61 km 2 for China represents 0.005% of the Gobi desert. Likewise, the 26 and 36 km 2 PV farm area, respectively, required for India and the US represents 0.01% and 0.014% land area of Rajasthan and Baja deserts. The above areas required for the farms may be further split to form a cluster of smaller energy farms.
1,082 citations
TL;DR: In this article, the wind resources assessment models, site selection models and aerodynamic models including wake effect are reviewed and different performance and reliability evaluation models, various problems related to wind turbine components (blade, gearbox, generator and transformer) and grid for wind energy system have been discussed.
Abstract: Energy is an essential ingredient of socio-economic development and economic growth. Renewable energy sources like wind energy is indigenous and can help in reducing the dependency on fossil fuels. Wind is the indirect form of solar energy and is always being replenished by the sun. Wind is caused by differential heating of the earth's surface by the sun. It has been estimated that roughly 10 million MW of energy are continuously available in the earth's wind. Wind energy provides a variable and environmental friendly option and national energy security at a time when decreasing global reserves of fossil fuels threatens the long-term sustainability of global economy. This paper reviews the wind resources assessment models, site selection models and aerodynamic models including wake effect. The different existing performance and reliability evaluation models, various problems related to wind turbine components (blade, gearbox, generator and transformer) and grid for wind energy system have been discussed. This paper also reviews different techniques and loads for design, control systems and economics of wind energy conversion system.
908 citations
TL;DR: In this paper, a socio-technical and multi-level theory on transitions is used to analyse the Dutch electricity system and find that an energy transition is already occurring, with roots in the 1960s and 1970s, but driven mainly by liberalisation and Europeanisation.
737 citations
Book•
20 Dec 2007
TL;DR: In this paper, the authors present an overview of the current technologies in Biodiesel production engine performance tests and future renewable energy and biofuel scenarios, as well as a discussion of biofuel economy and policies.
Abstract: Introduction to Energy Sources Biofuels Vegetable Oils and Animal Fats Biodiesel Biodiesel from Triglycerides via Transesterification Fuel Properties of Biodiesels Current Technologies in Biodiesel Production Engine Performance Tests Global Renewable Energy and Biofuel Scenarios Biodiesel Economy and Biodiesel Policy
701 citations
TL;DR: In this article, a European solar radiation database was developed using a solar radiation model and climatic data integrated within the Photovoltaic Geographic Information System (PVGIS) during the years 2001-2005, which consists of monthly and yearly averages of global irradiation and related climatic parameters, representing the period 1981-1990.
TL;DR: In this paper, the authors highlight on major agricultural, industrial and urban waste, which could be used for ethanol production in an ecofriendly and profitable manner, which will reduce dependency on foreign oil and remove disposal problem of wastes and make environment safe from pollution.
Abstract: With world reserves of petroleum fast depleting, in recent years ethanol has emerged as most important alternative resource for liquid fuel and has generated a great deal of research interest in ethanol fermentation. Research on improving ethanol production has been accelerating for both ecological and economical reasons, primarily for its use as an alternative to petroleum based fuels. Field crops offer potential source of fuel, offering promise as large-scale energy and based on its genetic diversity, climatic adaptation, biomass and sugar production. Lignocellulosic biomass is the most abundant organic raw material in the world. Production of ethanol from renewable lignocellulosic resources may improve energy availability, decrease air pollution and diminish atmospheric CO2 accumulation. The aim of the present review is to highlight on major agricultural, industrial and urban waste, which could be used for ethanol production in an ecofriendly and profitable manner. Primarily, the utilization of these wastes for ethanol production will reduce dependency on foreign oil and secondly, this will remove disposal problem of wastes and make environment safe from pollution.
TL;DR: In this paper, the authors compare the results of recent greenhouse gas (GHG) emission life-cycle analyses, focusing on fossil energy technologies, nuclear and renewable energy technologies (RETs), as well as carbon capture and storage and energy storage systems.
TL;DR: Sorghum is a highly productive, drought-tolerant species with a history of improvement and production of lignocellulose, sugar and starch as discussed by the authors.
Abstract: The increasing cost of energy and finite oil and gas reserves has created a need to develop alternative fuels from renewable sources Currently, the development of a renewable transportation fuel is ethanol based Ethanol production is now sugar/starch based, but use of these carbohydrates is limited; they are also required as a food and feed source The need to generate a large and sustainable supply of biomass to make biofuels generation from lignocellulose profitable will require the development of crops grown specifically for bioenergy production There will be several different species used as dedicated bioenergy crops, and for several reasons; it is expected that sorghum (Sorghum bicolor L Moench) will be one of these species Sorghum is a highly productive, drought-tolerant species with a history of improvement and production of lignocellulose, sugar and starch Given this history and the existing genetic improvement infrastructure available for the species, it is logical to expect that sorghum hybrids for dedicated bioenergy production can be developed in the near-term future and will be grown and used for bioenergy production © 2007 Society of Chemical Industry and John Wiley & Sons, Ltd
TL;DR: In this article, the need for better conversion technologies is a driving force behind many recent developments in biology, materials, and especially nanoscience, and they must have efficient ways to convert photons into electricity, fuel, and heat.
Abstract: If solar energy is to become a practical alternative to fossil fuels, we must have efficient ways to convert photons into electricity, fuel, and heat. The need for better conversion technologies is a driving force behind many recent developments in biology, materials, and especially nanoscience.
TL;DR: In this paper, a comprehensive review of past and present converter topologies applicable to permanent magnet generators, induction generators, synchronous generators and doubly fed induction generators is presented and compared on the basis of topology, cost, efficiency, power consumption and control complexity.
TL;DR: The main issues related to successful implementation policies concern the socio-economic institutions that are conditional to planning in the energy policy domain, but also in the domain of spatial planning as discussed by the authors.
TL;DR: Microbially made biofuels which have potential to replace the authors' present day fuels, either alone, by blending, or by chemical conversion are reviewed.
Abstract: Today, biomass covers about 10% of the world's primary energy demand. Against a backdrop of rising crude oil prices, depletion of resources, political instability in producing countries and environmental challenges, besides efficiency and intelligent use, only biomass has the potential to replace the supply of an energy hungry civilisation. Plant biomass is an abundant and renewable source of energy-rich carbohydrates which can be efficiently converted by microbes into biofuels, of which, only bioethanol is produced on an industrial scale today. Biomethane is produced on a large scale, but is not yet utilised for transportation. Biobutanol is on the agenda of several companies and may be used in the near future as a supplement for gasoline, diesel and kerosene, as well as contributing to the partially biological production of butyl-t-butylether, BTBE as does bioethanol today with ETBE. Biohydrogen, biomethanol and microbially made biodiesel still require further development. This paper reviews microbially made biofuels which have potential to replace our present day fuels, either alone, by blending, or by chemical conversion. It also summarises the history of biofuels and provides insight into the actual production in various countries, reviewing their policies and adaptivity to the energy challenges of foreseeable future.
TL;DR: In this article, the sizing and techno-economic optimisation of a stand-alone hybrid PV/wind system with battery storage is presented, where the main objective of the present study is to find the optimum size of system (optimum system configurations), able to fulfil the energy requirements of a given load distribution, for three sites located at Corsica island (at three sites in Corsica, Italy).
TL;DR: In this paper, the potential for wind, solar-PV and biomass (WSB) technologies to deliver energy is investigated in the context of the IPCC SRES scenarios as simulated with the IMAGE 2.2 model.
TL;DR: In this article, a general model was developed to find an optimal combination of energy components for a typical rural community minimizing the life cycle cost of a hybrid energy system, which is an excellent solution for electrification of remote rural areas where the grid extension and not economical.
TL;DR: In this article, the authors evaluate selected hydrogen production processes based on natural gas steam reforming, coal and biomass gasification and water electrolysis and conclude that these options are expected to play a significant role in the short to medium term.
TL;DR: In this article, the authors used a face-to-face questionnaire to determine energy consumption of input and output used in sugar beet production, and to make a cost analysis in Tokat, Turkey.
TL;DR: The results obtained show the successful implementation of HFAC Microgrid with adequate power flow and power quality control, as well as the optimization of operation cost by the DIEMS with Fuzzy ARTMAP-based day-type forecasting.
Abstract: In this paper, a single-phase high-frequency AC (HFAC) microgrid is shown as a novel solution towards integrating renewable energy sources in a distributed generation system. Better utilization of the Microgrid is achieved by solving power flow and power quality issues using p-q theory-based active filtering called universal active power line conditioner and unified power quality conditioner, respectively. A distributed intelligent energy management system (DIEMS) is implemented to optimize operating costs. As the optimization greatly depends on the power generation and the power output from renewable sources strongly depends on the weather, the forecast of power generation is required for DIEMS. A Fuzzy ARTMAP neural network is used to predict hourly day-type outputs based on which generation can be forecasted. Depending on the forecast, an optimization scheme is developed utilizing linear programming along with heuristics. The results obtained show the successful implementation of HFAC Microgrid with adequate power flow and power quality control, as well as the optimization of operation cost by the DIEMS with Fuzzy ARTMAP-based day-type forecasting. The improvement in the battery life is also achieved due to optimization of storage charge states using the proposed DIEMS
TL;DR: In this article, the authors present the findings of a choice experiment designed to estimate consumer preferences and willingness-to-pay (WTP) for voluntary participation in green energy electricity programs.
TL;DR: In this paper, a genetic algorithm is used to optimize the control of a stand-alone hybrid renewable electrical system with hydrogen storage, which can be composed of renewable sources (wind, PV and hydro), batteries, fuel cell, AC generator and electrolyzer.
07 May 2007
TL;DR: In this article, the authors present an analysis of the U.S. energy consumption and prices in the midterm and forecast for the next five years, focusing on renewable energy technologies.
Abstract: Global energy system / D. Yogi Goswami, Frank Kreith -- Energy policy -- Economics methods / Rosalie Ruegg, Walter Short -- Environmental impacts and costs of energy / Ari Rabl, Joseph V. Spadaro -- Distributed generation and demand-side management -- Generation technologies through the year 2025 -- Outlook for U.S. energy consumption and prices in the midterm / Andy S. Kydes -- Transportation systems / Beth Isler -- Infrastructure risk analysis and security -- Electrical energy management in buildings / Craig B. Smith, Kelly E. Parmenter -- Heating, ventilating, and air conditioning control systems / Jan F. Kreider, David E. Claridge, Charles H. Culp -- Energy efficient technologies -- Compact heat exchangers : recuperators and regenerators / Ramesh K. Shah -- Industrial energy efficiency and energy management / Craig B. Smith, Barney L. Capehart, Wesley M. Rohrer Jr. -- Process energy efficiency : pinch technology -- Energy audits for buildings / Moncef Krarti -- Cogeneration / W. Dan Turner -- Energy storage, transmission, and distribution -- Availability of renewable resources -- Solar thermal energy conversion -- Concentrating solar thermal power / Manuel Romero-Alvarez, Eduardo Zarza -- Wind energy conversion / Dale E. Berg -- Photovoltaics fundamentals, technology, and application -- Waste-to-energy combustion / Charles O. Velzy, Leonard M. Grillo -- Biomass conversion processes for energy recovery -- Geothermal power generation / Kevin Kitz -- Hydrogen energy technologies / S.A. Sherif, F. Barbir, T.N. Veziroglu, M. Mahishi, S.S. Srinivasan -- Fuel cells / Xianguo Li -- Appendices / Nitin Goel.
TL;DR: A review of the highlights that have been achieved during the recent years and the state-of-the-art for most important efforts in the field of desalination by renewable energies, with emphasis on solar energy applications is presented in this paper.
TL;DR: In this article, a fuzzy-optimization approach for solving the generation scheduling problem with consideration of wind and solar energy systems is presented, where the forecast hourly load, available water, wind speed, solar radiation, spinning reserve and total fuel cost are taken into account using fuzzy sets.
Abstract: This paper presents a fuzzy-optimization approach for solving the generation scheduling problem with consideration of wind and solar energy systems. Wind and solar energy are being considered in the power system to schedule unit power output to minimize the total thermal unit fuel cost. When performing the generation scheduling problem in conventional methods, the hourly load, available water, wind speed, solar radiation must be forecasted to prevent errors. However, actually there are always errors in these forecasted values. A characteristic feature of the proposed fuzzy-optimization approach is that the forecast hourly load, available water, wind speed and solar radiation errors can be taken into account using fuzzy sets. Fuzzy set notations in the hourly load, available water, wind speed, solar radiation, spinning reserve and total fuel cost are developed to obtain the optimal generation schedule under an uncertain environment. To demonstrate the effectiveness of the proposed method, the generation scheduling problem is performed in a simplified generation system. The results show that a proper generating schedule for each unit can be reached using the proposed method.