Showing papers on "Renewable energy published in 2009"
TL;DR: In this article, the open-circuit voltage of polymer solar cells constructed based on the structure of a low-bandgap polymer, PBDTTT, can be tuned, step by step, using different functional groups.
Abstract: Following the development of the bulk heterojunction1 structure, recent years have seen a dramatic improvement in the efficiency of polymer solar cells. Maximizing the open-circuit voltage in a low-bandgap polymer is one of the critical factors towards enabling high-efficiency solar cells. Study of the relation between open-circuit voltage and the energy levels of the donor/acceptor2 in bulk heterojunction polymer solar cells has stimulated interest in modifying the open-circuit voltage by tuning the energy levels of polymers3. Here, we show that the open-circuit voltage of polymer solar cells constructed based on the structure of a low-bandgap polymer, PBDTTT4, can be tuned, step by step, using different functional groups, to achieve values as high as 0.76 V. This increased open-circuit voltage combined with a high short-circuit current density results in a polymer solar cell with a power conversion efficiency as high as 6.77%, as certified by the National Renewable Energy Laboratory. Adding electron-withdrawing groups to the backbone of the polymer PBDTTT is shown to increase the open-circuit voltage of photovoltaic cells, resulting in a polymer solar-cell that has a certified power-conversion efficiency of 6.77%.
3,029 citations
TL;DR: In this paper, the authors provide an up-to-date review of the various modeling techniques used for modeling residential sector energy consumption, focusing on the strengths, shortcomings and purposes.
Abstract: There is a growing interest in reducing energy consumption and the associated greenhouse gas emissions in every sector of the economy. The residential sector is a substantial consumer of energy in every country, and therefore a focus for energy consumption efforts. Since the energy consumption characteristics of the residential sector are complex and inter-related, comprehensive models are needed to assess the technoeconomic impacts of adopting energy efficiency and renewable energy technologies suitable for residential applications. The aim of this paper is to provide an up-to-date review of the various modeling techniques used for modeling residential sector energy consumption. Two distinct approaches are identified: top-down and bottom-up. The top-down approach treats the residential sector as an energy sink and is not concerned with individual end-uses. It utilizes historic aggregate energy values and regresses the energy consumption of the housing stock as a function of top-level variables such as macroeconomic indicators (e.g. gross domestic product, unemployment, and inflation), energy price, and general climate. The bottom-up approach extrapolates the estimated energy consumption of a representative set of individual houses to regional and national levels, and consists of two distinct methodologies: the statistical method and the engineering method. Each technique relies on different levels of input information, different calculation or simulation techniques, and provides results with different applicability. A critical review of each technique, focusing on the strengths, shortcomings and purposes, is provided along with a review of models reported in the literature.
1,748 citations
TL;DR: In this paper, the authors discuss the present status of battery energy storage technology and methods of assessing their economic viability and impact on power system operation and suggest a likely future outlook for the battery technologies and the electric hybrid vehicles in the context of power system applications.
1,627 citations
TL;DR: Intensive animal production areas need suitable manure management, aiming to export and to redistribute the excess of nutrients from manure and to optimize their recycling, to avoid over-fertilization.
1,466 citations
TL;DR: An overview of the current and future energy storage technologies used for electric power applications is carried out in this paper, where a comparison between the various technologies is presented in terms of the most important technological characteristics of each technology.
Abstract: In today's world, there is a continuous global need for more energy which, at the same time, has to be cleaner than the energy produced from the traditional generation technologies. This need has facilitated the increasing penetration of distributed generation (DG) technologies and primarily of renewable energy sources (RES). The extensive use of such energy sources in today's electricity networks can indisputably minimize the threat of global warming and climate change. However, the power output of these energy sources is not as reliable and as easy to adjust to changing demand cycles as the output from the traditional power sources. This disadvantage can only be effectively overcome by the storing of the excess power produced by DG-RES. Therefore, in order for these new sources to become completely reliable as primary sources of energy, energy storage is a crucial factor. In this work, an overview of the current and future energy storage technologies used for electric power applications is carried out. Most of the technologies are in use today while others are still under intensive research and development. A comparison between the various technologies is presented in terms of the most important technological characteristics of each technology. The comparison shows that each storage technology is different in terms of its ideal network application environment and energy storage scale. This means that in order to achieve optimum results, the unique network environment and the specifications of the storage device have to be studied thoroughly, before a decision for the ideal storage technology to be selected is taken.
1,265 citations
TL;DR: In this paper, the authors present the methodology and results of the overall energy system analysis of a 100% renewable energy system, which includes hour by hour computer simulations leading to the design of flexible energy systems with the ability to balance the electricity supply and demand.
1,032 citations
01 Dec 2009
TL;DR: In this paper, a review of wave energy converter (WEC) technology is presented, focusing on work being undertaken within the United Kingdom, and some of the control strategies to enhance the efficiency of point absorber-type WECs.
Abstract: Ocean waves are a huge, largely untapped energy resource, and the potential for extracting energy from waves is considerable. Research in this area is driven by the need to meet renewable energy targets, but is relatively immature compared to other renewable energy technologies. This review introduces the general status of wave energy and evaluates the device types that represent current wave energy converter (WEC) technology, particularly focusing on work being undertaken within the United Kingdom. The possible power take-off systems are identified, followed by a consideration of some of the control strategies to enhance the efficiency of point absorber-type WECs. There is a lack of convergence on the best method of extracting energy from the waves and, although previous innovation has generally focused on the concept and design of the primary interface, questions arise concerning how best to optimize the powertrain. This article concludes with some suggestions of future developments.
992 citations
TL;DR: In this article, the authors reviewed different techniques, methodologies and algorithms developed to monitor the performance of wind turbine as well as for an early fault detection to keep away the wind turbines from catastrophic conditions due to sudden breakdowns.
Abstract: Renewable energy sources like wind energy are copiously available without any limitation. Wind turbines are used to tap the potential of wind energy, which is available in millions of MW. Reliability of wind turbine is critical to extract this maximum amount of energy from the wind. We reviewed different techniques, methodologies and algorithms developed to monitor the performance of wind turbine as well as for an early fault detection to keep away the wind turbines from catastrophic conditions due to sudden breakdowns. To keep the wind turbine in operation, implementation of condition monitoring system (CMS) and fault detection system (FDS) is paramount and for this purpose ample knowledge of these two types of systems is mandatory. So, an attempt has been made in this direction to review maximum approaches related to CMS and FDS in this piece of writing.
982 citations
TL;DR: The biofuel policy aims to promote the use in transport of fuels made from biomass, as well as other renewable fuels as mentioned in this paper, which provides the prospect of new economic opportunities for people in rural areas in oil importer and developing countries.
981 citations
TL;DR: In this paper, the authors assessed the non-combustion based renewable electricity generation technologies against a range of sustainability indicators and using data obtained from the literature, they found that wind power is the most sustainable, followed by hydropower, photovoltaic and then geothermal.
Abstract: The non-combustion based renewable electricity generation technologies were assessed against a range of sustainability indicators and using data obtained from the literature. The indicators used to assess each technology were price of generated electricity, greenhouse gas emissions during full life cycle of the technology, availability of renewable sources, efficiency of energy conversion, land requirements, water consumption and social impacts. The cost of electricity, greenhouse gas emissions and the efficiency of electricity generation were found to have a very wide range for each technology, mainly due to variations in technological options as well as geographical dependence of each renewable energy source. The social impacts were assessed qualitatively based on the major individual impacts discussed in literature. Renewable energy technologies were then ranked against each indicator assuming that indicators have equal importance for sustainable development. It was found that wind power is the most sustainable, followed by hydropower, photovoltaic and then geothermal. Wind power was identified with the lowest relative greenhouse gas emissions, the least water consumption demands and with the most favourable social impacts comparing to other technologies, but requires larger land and has high relative capital costs.
896 citations
TL;DR: In this article, a comprehensive review of different fuel cell technologies with their working principle, advantages, disadvantages and suitability of applications for residential/grid-connected system, transportation, industries and commercial applications is discussed.
Abstract: The issue of renewable energy is becoming significant due to increasing power demand, instability of the rising oil prices and environmental problems. Among the various renewable energy sources, fuel cell is gaining more popularity due to their higher efficiency, cleanliness and cost-effective supply of power demanded by the consumers. This paper presents a comprehensive review of different fuel cell technologies with their working principle, advantages, disadvantages and suitability of applications for residential/grid-connected system, transportation, industries and commercial applications. Development of mathematical model of fuel cell required for simulation study is discussed. This paper also focuses on the necessity of a suitable power-conditioning unit required to interface the fuel cell system with standalone/grid applications.
TL;DR: In this article, the authors present and estimate two empirical models of renewable energy consumption and income for a panel of emerging economies, and show that increases in real per capita income have a positive and statistically significant impact on per capita renewable energy usage.
TL;DR: In this article, the authors examined the use of fractional-ARIMA or f-ARAMA models to model, and forecast wind speeds on the day-ahead and two-day-ahead (48 h) horizons.
TL;DR: There are several thermo-chemical routes for biomass-based energy production, such as direct combustion, liquefaction, pyrolysis, supercritical water extraction, gasification, air-steam gasification and so on.
TL;DR: In this article, a detailed overview on tar chemical and physical properties, reforming mechanism and reaction kinetic model are summarized in a detail overview on coal-to-tar conversion process is presented.
Abstract: Biomass becomes an important primary energy source as well as renewable energy source. As the most promising biomass utilization method, biomass gasification is gaining attention as a route for biomass energy production, but producer gas from this process usually contains unacceptable levels of tar. The tar control and convert is a key issue for a successful application of biomass-derived producer gas. A detail overview on tar chemical and physical properties, reforming mechanism and reaction kinetic model are summarized in this paper.
TL;DR: In this article, the authors present and estimate an empirical model of renewable energy consumption for the G7 countries and show that in the long term, increases in real GDP per capita and CO2 per capita are major drivers behind per capita renewable energy usage.
TL;DR: In this paper, the authors present the main aspects of the DMG framework, illustrating its characteristics and summarizing the relevant DMG structures, backed by an extended review of the most recent journal publications and reports.
Abstract: The recent development of efficient thermal prime movers for distributed generation is changing the focus of the production of electricity from large centralized power plants to local generation units scattered over the territory. The scientific community is addressing the analysis and planning of distributed energy resources with widespread approaches, taking into account technical, environmental, economic and social issues. The coupling of cogeneration systems to absorption/electric chillers or heat pumps, as well as the interactions with renewable sources, allow for setting up multi-generation systems for combined local production of different energy vectors such as electricity, heat (at different enthalpy levels), cooling power, hydrogen, various chemical substances, and so forth. Adoption of composite multi-generation systems may lead to significant benefits in terms of higher energy efficiency, reduced CO2 emissions, and enhanced economy. In this light, a key direction for improving the characteristics of the local energy production concerns the integration of the concepts of distributed energy resources and combined production of different energy vectors into a comprehensive distributed multi-generation (DMG) framework that entails various approaches to energy planning currently available in the literature. This paper outlines the main aspects of the DMG framework, illustrating its characteristics and summarizing the relevant DMG structures. The presentation is backed by an extended review of the most recent journal publications and reports.
TL;DR: In this article, an optimal design model for designing hybrid solar-wind systems employing battery banks for calculating the system optimum configurations and ensuring that the annualized cost of the systems is minimized while satisfying the custom required loss of power supply probability (LPSP).
TL;DR: In this article, the current state of the design, operation and control requirement of the stand-alone PV solar-wind hybrid energy systems with conventional backup source i.e. diesel or grid.
Abstract: The wind and solar energy are omnipresent, freely available, and environmental friendly. The wind energy systems may not be technically viable at all sites because of low wind speeds and being more unpredictable than solar energy. The combined utilization of these renewable energy sources are therefore becoming increasingly attractive and are being widely used as alternative of oil-produced energy. Economic aspects of these renewable energy technologies are sufficiently promising to include them for rising power generation capability in developing countries. A renewable hybrid energy system consists of two or more energy sources, a power conditioning equipment, a controller and an optional energy storage system. These hybrid energy systems are becoming popular in remote area power generation applications due to advancements in renewable energy technologies and substantial rise in prices of petroleum products. Research and development efforts in solar, wind, and other renewable energy technologies are required to continue for, improving their performance, establishing techniques for accurately predicting their output and reliably integrating them with other conventional generating sources. The aim of this paper is to review the current state of the design, operation and control requirement of the stand-alone PV solar–wind hybrid energy systems with conventional backup source i.e. diesel or grid. This Paper also highlights the future developments, which have the potential to increase the economic attractiveness of such systems and their acceptance by the user.
TL;DR: It is demonstrated how properly controlling the "nanomorphology", which is critically dependent on minute experimental details at every step, provides a clear path to >10% PCE BHJ cells, which can be fabricated at a fraction of the cost of conventional solar cells.
Abstract: As the global demand for low-cost renewable energy sources intensifies, interest in new routes for converting solar energy to electricity is rapidly increasing. Although photovoltaic cells have been commercially available for more than 50 years, only 0.1% of the total electricity generated in the United States comes directly from sunlight. The earliest commercial solar technology remains the basis for the most prevalent devices in current use, namely, highly-ordered crystalline, inorganic solar cells, commonly referred to as silicon cells. Another class of solar cells that has recently inspired significant academic and industrial excitement is the bulk heterojunction (BHJ) “plastic” solar cell. Research by a rapidly growing community of scientists across the globe is generating a steady stream of new insights into the fundamental physics, the materials design and synthesis, the film processing and morphology, and the device science and architecture of BHJ technology. Future progress in the fabrication of ...
TL;DR: In this article, the authors evaluate the effectiveness of state energy programs with an empirical investigation of the linkage between state RPS policy implementation and the percentage of renewable energy electricity generation across states.
TL;DR: In this article, the potential of microalgal biodiesel in comparison to the agricultural crops and its prospects in India is reviewed, and the authors propose a microalgae-based carbon sequestration technology to cover the cost of carbon capture and sequestration.
Abstract: Energy is essential and vital for development, and the global economy literally runs on energy. The use of fossil fuels as energy is now widely accepted as unsustainable due to depleting resources and also due to the accumulation of greenhouse gases in the environment. Renewable and carbon neutral biodiesel are necessary for environmental and economic sustainability. Biodiesel demand is constantly increasing as the reservoir of fossil fuel are depleting. Unfortunately biodiesel produced from oil crop, waste cooking oil and animal fats are not able to replace fossil fuel. The viability of the first generation biofuels production is however questionable because of the conflict with food supply. Production of biodiesel using microalgae biomass appears to be a viable alternative. The oil productivity of many microalgae exceeds the best producing oil crops. Microalgae are photosynthetic microorganisms which convert sunlight, water and CO2 to sugars, from which macromolecules, such as lipids and triacylglycerols (TAGs) can be obtained. These TAGs are the promising and sustainable feedstock for biodiesel production. Microalgal biorefinery approach can be used to reduce the cost of making microalgal biodiesel. Microalgal-based carbon sequestration technologies cover the cost of carbon capture and sequestration. The present paper is an attempt to review the potential of microalgal biodiesel in comparison to the agricultural crops and its prospects in India.
TL;DR: In this paper, the importance of solar cell/module operating temperature for the electrical performance of silicon-based photovoltaic installations is briefly discussed, and the explicit and implicit correlations found in the literature which link this temperature with standard weather variables and material/systemdependent properties, in an effort to facilitate the modeling/design process in this very promising area of renewable energy applications.
TL;DR: In this paper, the authors investigated the global potential and use of biomass energy and its contribution to the sustainable energy development by presenting its historical development, and the main objective of the present study is to investigate global potential, use, and contribution of the biomass energy.
TL;DR: In this article, the social, economical and environmental effects of renewable energy system have been discussed in the remote areas of the world, and the results show that the trends of total emission reduction in different years, which is exponentially increasing after the installation of renewable energies system in remote areas.
TL;DR: In this article, a 6.6-kV battery energy storage system based on a cascade PWM converter with focus on a control method for state-of-charge (SOC) balancing of the battery units is described.
Abstract: Renewable energy sources such as wind turbine generators and photovoltaics produce fluctuating electric power. The fluctuating power can be compensated by installing an energy storage system in the vicinity of these sources. This paper describes a 6.6-kV battery energy storage system based on a cascade pulsewidth-modulation (PWM) converter with focus on a control method for state-of-charge (SOC) balancing of the battery units. A 200-V, 10-kW, 3.6-kWh (13-MJ) laboratory system combining a cascade PWM converter with nine nickel metal hydride (NiMH) battery units is designed, constructed, and tested to verify the validity and effectiveness of the proposed balancing control.
TL;DR: In this paper, the authors review existing energy and CO2 life cycle analyses of renewable sources based electricity generation systems and point out that carbon emission from renewable energy (RE) systems are not nil, as is generally assumed while evaluating carbon credits.
Abstract: Sustainable development requires methods and tools to measure and compare the environmental impacts of human activities for various products (goods and services). Providing society with goods and services contributes to a wide range of environmental impacts. Environmental impacts include emissions into the environment and the consumption of resources as well as other interventions such as land use, etc. Life cycle assessment (LCA) is a technique for assessing environmental loads of a product or a system. The aim of this paper is to review existing energy and CO2 life cycle analyses of renewable sources based electricity generation systems. The paper points out that carbon emission from renewable energy (RE) systems are not nil, as is generally assumed while evaluating carbon credits. Further the range of carbon emissions from RE systems have been found out from existing literature and compared with those from fossil fuel based systems, so as to assist in a rational choice of energy supply systems.
TL;DR: The conversion of woody-wastes by pyrolysis to produce biochar (biologically derived charcoal) is one potential option that can enhance natural rates of carbon sequestration in soils, reduce farm waste, and substitute renewable energy sources for fossil-derived fuel inputs as mentioned in this paper.
TL;DR: In this paper, a review is addressed to various aspects of biodiesel production and the latest literature has been critically reviewed and consulted, which seems to be an ideal solution for global energy demands including India as well.
Abstract: Fuels are inevitable for industrial development and growth of any country. The life span of fossil fuel resources has always been terrifying. Biodiesel, a renewable source of energy seems to be an ideal solution for global energy demands including India as well. The current review is addressed to various aspects of biodiesel production. Latest literature has been critically reviewed and consulted.
TL;DR: In this article, the authors present current scenario of biomass in Malaysia and discuss feasibility of some biomass conversion technologies and some ongoing projects in Malaysia related to utilization of oil palm biomass as a source of renewable energy.