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Energies, Volume 2, Issue 1 (March 2009), Pages 1-179

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Research

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Open AccessArticle Energy Inputs in Food Crop Production in Developing and Developed Nations
Energies 2009, 2(1), 1-24; doi:10.3390/en20100001
Received: 18 November 2008 / Revised: 5 January 2009 / Accepted: 13 January 2009 / Published: 16 January 2009
Cited by 31 | PDF Full-text (118 KB) | HTML Full-text | XML Full-text
Abstract Detailed energy outputs and inputs were assessed for the following crops, cultured in the U.S. and developing countries: corn, wheat, rice, soy, potato, cassava, tomato, citrus and apple. In addition, the labor input for each crop was analyzed. Full article
Open AccessArticle Microalgal and Terrestrial Transport Biofuels to Displace Fossil Fuels
Energies 2009, 2(1), 48-56; doi:10.3390/en20100048
Received: 19 November 2008 / Revised: 17 February 2009 / Accepted: 18 February 2009 / Published: 19 February 2009
Cited by 12 | PDF Full-text (56 KB) | HTML Full-text | XML Full-text
Abstract
Terrestrial transport biofuels differ in their ability to replace fossil fuels. When both the conversion of solar energy into biomass and the life cycle inputs of fossil fuels are considered, ethanol from sugarcane and biodiesel from palm oil do relatively well, if [...] Read more.
Terrestrial transport biofuels differ in their ability to replace fossil fuels. When both the conversion of solar energy into biomass and the life cycle inputs of fossil fuels are considered, ethanol from sugarcane and biodiesel from palm oil do relatively well, if compared with ethanol from corn, sugar beet or wheat and biodiesel from rapeseed. When terrestrial biofuels are to replace mineral oil-derived transport fuels, large areas of good agricultural land are needed: about 5x108 ha in the case of biofuels from sugarcane or oil palm, and at least 1.8-3.6x109 ha in the case of ethanol from wheat, corn or sugar beet, as produced in industrialized countries. Biofuels from microalgae which are commercially produced with current technologies do not appear to outperform terrestrial plants such as sugarcane in their ability to displace fossil fuels. Whether they will able to do so on a commercial scale in the future, is uncertain. Full article
Open AccessArticle Experimental Investigations of Extracted Rapeseed Combustion Emissions in a Small Scale Stationary Fluidized Bed Combustor
Energies 2009, 2(1), 57-70; doi:10.3390/en20100057
Received: 21 December 2008 / Revised: 16 February 2009 / Accepted: 18 February 2009 / Published: 19 February 2009
Cited by 2 | PDF Full-text (294 KB) | HTML Full-text | XML Full-text
Abstract
The objective of this study was to observe the combustion process of extracted rapeseed (ER) grist in a stationary fluidized bed combustor (SFBC) and evaluate the chemical compositions of the flue gas emissions. The experimental tests of ER combustion in the 90 [...] Read more.
The objective of this study was to observe the combustion process of extracted rapeseed (ER) grist in a stationary fluidized bed combustor (SFBC) and evaluate the chemical compositions of the flue gas emissions. The experimental tests of ER combustion in the 90 to 200 kW (Kilowatt) SFB combustion test facility show that the optimal ER combustion temperature is within the range from 850 to 880° C. Temperature and the concentration of exhausted emissions (e.g. O2, CO, CO2, NO, NO2, SO2, Corg) were measured with dedicated sensors distributed within the combustor, along its height and in the flue gas duct. The experimental results showed that with respect to German emission limits the concentration of SO2 and NOx in the flue gas were high whereas that of CO was low. This study furthermore is applicable for the abundant biomass residue resources in Vietnam (rice husk, rice straw, bagasse, cassava residues, coconut shell etc.), which have similar chemical compositions to ER. Full article
Open AccessArticle Analysis of the Coupling Behavior of PEM Fuel Cells and DC-DC Converters
Energies 2009, 2(1), 71-96; doi:10.3390/en2010071
Received: 8 January 2009 / Accepted: 19 February 2009 / Published: 4 March 2009
Cited by 3 | PDF Full-text (1543 KB) | HTML Full-text | XML Full-text
Abstract
The connection between PEM fuel cells and common DC-DC converters is examined. The analysis is model-based and done for boost, buck and buck-boost converters. In a first step, the effect of the converter ripples upon the PEM fuel cell is shown. They [...] Read more.
The connection between PEM fuel cells and common DC-DC converters is examined. The analysis is model-based and done for boost, buck and buck-boost converters. In a first step, the effect of the converter ripples upon the PEM fuel cell is shown. They introduce oscillations in the fuel cell. Their appearance is explained, discussed and possibilities for their suppression are given. After that, the overall behaviors of the coupled fuel cell-converter systems are analyzed. It is shown, that neither stationary multiplicities nor oscillations can be introduced by the couplings and therefore separate control approaches for both the PEMFC and the DC-DC converters are applicable. Full article
(This article belongs to the Special Issue Fuel Cells)
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Open AccessArticle Experimental Study on Forced Convective Heat Transfer with Low Volume Fraction of CuO/Water Nanofluid
Energies 2009, 2(1), 97-119; doi:10.3390/en20100097
Received: 30 October 2008 / Revised: 27 February 2009 / Accepted: 4 March 2009 / Published: 6 March 2009
Cited by 28 | PDF Full-text (1188 KB) | HTML Full-text | XML Full-text
Abstract
The present work is an experimental study of steady state convective heat transfer of de-ionized water with a low volume fraction (0.003% by volume) of copper oxide (CuO) nanoparticles dispersed to form a nanofluid that flows through a copper tube. The effect [...] Read more.
The present work is an experimental study of steady state convective heat transfer of de-ionized water with a low volume fraction (0.003% by volume) of copper oxide (CuO) nanoparticles dispersed to form a nanofluid that flows through a copper tube. The effect of mass flow rate ranging from (0.0113 kg/s to 0.0139 kg/s) and the effect of inlet temperatures at 100C and 17 0C on the heat transfer coefficient are studied on the entry region under laminar flow condition. The results have shown 8% enhancement of the convective heat transfer coefficient of the nanofluid even with a low volume concentration of CuO nanoparticles. The heat transfer enhancement was increased considerably as the Reynolds number increased. Possible reasons for the enhancement are discussed. Nanofluid thermo-physical properties and chaotic movement of ultrafine particles which accelerate the energy exchange process are proposed to be the main reasons for the observed heat transfer enhancement. A correlation for convective heat transfer coefficient of nanofluids, based on transport property and D/x for 8 mm tube has been evolved. The correlation predicts variation in the local Nusselt number along the flow direction of the nanofluid. A good agreement (±10%) is seen between the experimental and predicted results. Full article
Open AccessArticle Potential Bioethanol Feedstock Availability Around Nine Locations in the Republic of Ireland
Energies 2009, 2(1), 120-133; doi:10.3390/en20100120
Received: 14 February 2009 / Revised: 4 March 2009 / Accepted: 5 March 2009 / Published: 9 March 2009
Cited by 3 | PDF Full-text (137 KB)
Abstract
The Republic of Ireland, like many other countries is trying to diversify energy sources to counteract environmental, political and social concerns. Bioethanol from domestically grown agricultural crops is an indigenously produced alternative fuel that can potentially go towards meeting the goal of [...] Read more.
The Republic of Ireland, like many other countries is trying to diversify energy sources to counteract environmental, political and social concerns. Bioethanol from domestically grown agricultural crops is an indigenously produced alternative fuel that can potentially go towards meeting the goal of diversified energy supply. The Republic of Ireland’s distribution of existing soils and agricultural land-uses limit arable crop land to around 10% of total agricultural area. Demand for land to produce arable crops is expected to decrease, which could open the opportunity for bioethanol production. Bioethanol production plants are required to be of a sufficient scale in order to compete economically with other fuel sources, it is important therefore to determine if enough land exists around potential ethanol plant locations to meet the potential demands for feedstock. This study determines, through the use of a developed GIS based model, the potential quantities of feedstock that is available in the hinterlands of nine locations in the Republic of Ireland. The results indicate that three locations can meet all its feedstock demands using indigenously grown sugarbeet, while only one location can meet its demands using a combination of indigenous wheat and straw as the two locally sourced feedstocks. Full article
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Open AccessArticle Energy Utilization and Environmental Aspects of Rice Processing Industries in Bangladesh
Energies 2009, 2(1), 134-149; doi:10.3390/en20100134
Received: 23 January 2009 / Revised: 6 March 2009 / Accepted: 10 March 2009 / Published: 12 March 2009
Cited by 10 | PDF Full-text (326 KB) | HTML Full-text | XML Full-text
Abstract
In this study, the energy utilization and environmental aspects of the rice processing industries in Bangladesh was analyzed. Rice husk, a milling by-product of rice, is used as a source of thermal energy to produce steam for parboiling of raw rice. The [...] Read more.
In this study, the energy utilization and environmental aspects of the rice processing industries in Bangladesh was analyzed. Rice husk, a milling by-product of rice, is used as a source of thermal energy to produce steam for parboiling of raw rice. The rice is mostly dried on a concrete floor under the sunshine. In mechanical drying, rice husks are used as a source of primary energy. In Bangladesh, the annual estimated energy used in 2000 for the drying of rice by sunshine was 10.7 million GJ and for drying and parboiling by rice husks it was 48.2 million GJ. These amounts will increase to 20.5 and 92.5 million GJ in 2030, respectively. Electrical energy consumption for mechanical drying and milling of rice was calculated as 1.83 million GJe and 3.51 million GJe in 2000 and in 2030, respectively. Biogenic carbon dioxide emission from burning of rice husk is renewed every year by the rice plant. Both the biogenic and non-biogenic carbon dioxide emissions in 2000 were calculated as 5.7 and 0.4 million tonnes, respectively, which will increase to 10.9 and 0.7 million tonnes in 2030. The demand of energy for rice processing increases every year, therefore, energy conservation in rice processing industries would be a viable option to reduce the intensity of energy by increasing the efficiency of rice processing systems which leads to a reduction in emissions and an increased supply of rice husk energy to other sectors as well. Full article
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Open AccessArticle Hydrogen as Future Energy Carrier: The ENEA Point of View on Technology and Application Prospects
Energies 2009, 2(1), 150-179; doi:10.3390/en20100150
Received: 16 February 2009 / Revised: 16 March 2009 / Accepted: 18 March 2009 / Published: 24 March 2009
Cited by 10 | PDF Full-text (1239 KB) | HTML Full-text | XML Full-text
Abstract
Hydrogen and fuel cells should reduce costs and increase reliability and durability to compete in the energy market. A considerable long term effort is necessary for research, development and demonstration of adequate solutions; important programs in this sense are carried out in [...] Read more.
Hydrogen and fuel cells should reduce costs and increase reliability and durability to compete in the energy market. A considerable long term effort is necessary for research, development and demonstration of adequate solutions; important programs in this sense are carried out in the main industrialized countries, with the involvement of many industries, research structures and stakeholders. In such framework a relevant role is played in Italy by ENEA (Italian Agency for New Technologies, Energy and Environment). In the paper the main aspects related to the possible hydrogen role in the future society are addressed, according to ENEA perspectives. Full article
(This article belongs to the Special Issue Energy Policy)

Review

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Open AccessReview What is the Minimum EROI that a Sustainable Society Must Have?
Energies 2009, 2(1), 25-47; doi:10.3390/en20100025
Received: 12 December 2008 / Revised: 10 January 2009 / Accepted: 13 January 2009 / Published: 23 January 2009
Cited by 152 | PDF Full-text (725 KB) | HTML Full-text | XML Full-text
Abstract
Economic production and, more generally, most global societies, are overwhelmingly dependant upon depleting supplies of fossil fuels. There is considerable concern amongst resource scientists, if not most economists, as to whether market signals or cost benefit analysis based on today’s prices are [...] Read more.
Economic production and, more generally, most global societies, are overwhelmingly dependant upon depleting supplies of fossil fuels. There is considerable concern amongst resource scientists, if not most economists, as to whether market signals or cost benefit analysis based on today’s prices are sufficient to guide our decisions about our energy future. These suspicions and concerns were escalated during the oil price increase from 2005 – 2008 and the subsequent but probably related market collapse of 2008. We believe that Energy Return On Investment (EROI) analysis provides a useful approach for examining disadvantages and advantages of different fuels and also offers the possibility to look into the future in ways that markets seem unable to do. The goal of this paper is to review the application of EROI theory to both natural and economic realms, and to assess preliminarily the minimum EROI that a society must attain from its energy exploitation to support continued economic activity and social function. In doing so we calculate herein a basic first attempt at the minimum EROI for current society and some of the consequences when that minimum is approached. The theory of the minimum EROI discussed here, which describes the somewhat obvious but nonetheless important idea that for any being or system to survive or grow it must gain substantially more energy than it uses in obtaining that energy, may be especially important. Thus any particular being or system must abide by a “Law of Minimum EROI”, which we calculate for both oil and corn-based ethanol as about 3:1 at the mine-mouth/farm-gate. Since most biofuels have EROI’s of less than 3:1 they must be subsidized by fossil fuels to be useful. Full article

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