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[en] Today it is common to evaluate and compare energy systems in terms of emission of greenhouse gases. However, energy systems should not only reduce their pollution but also give a large energy return. One method used to measure energy efficiency is emergy (embodied energy, energy memory) evaluation, which was developed by the system ecologist Howard T. Odum. Odum defines emergy as the available energy of one kind previously used up directly and indirectly to make a service or product. Both work of nature and work of human economy in generating products and services are calculated in terms of emergy. Work of nature takes the form of natural resources and work of human economy includes labour, services and products used to transform natural resources into something of value to the economy. The quotient between work of nature and work of human economy gives the emergy return on investment of the investigated product. With this in mind the present work is an attempt to make an emergy evaluation of a Swedish nuclear power plant to estimate its emergy return on investment. The emergy return on investment ratio of a Swedish nuclear power plant is calculated to approximately 11 in this diploma thesis. This means that for all emergy the Swedish economy has invested in the nuclear power plant it gets 11 times more emergy in return in the form of electricity generated by nuclear power. The method used in this work may facilitate future emergy evaluations of other energy systems
[en] The current Laser Electron Acceleration Program (LEAP) seeks to modulate the energy of an electron bunch by interaction of the electrons with a copropagating pair of crossed laser beams at 800 nm. We present an optical injector design for a LEAP cell so that it can be used to give net energy gain to an electron bunch. Unique features of the design are discussed which will allow this net energy gain and which will also provide a robust signature for the LEAP interaction
[en] In a Fermi-degenerate plasma, the electronic stopping of a slow ion is smaller than that given by the classical formula, because some transitions between the electron states are forbidden. The bremsstrahlung losses are then smaller, so that the nuclear burning of an aneutronic fuel is more efficient. Consequently, there occurs a parameter regime in which self-burning is possible. Practical obstacles in this regime that must be overcome before net energy can be realized include the compression of the fuel to an ultra dense state and the creation of a hot spot
[en] We estimate the energy content, the operational energy inputs, and the net energy ratio (NER) of an industrial tubular photo-bioreactor used for the photosynthetic production of H2 by micro-algae. The calculated H2 output of the photo-bioreactor is based on a range of algal photosynthetic H2 generation efficiencies, and on the application of standard theory for tubular solar collectors. Small diameter reactors have a low NER as the mixing energy becomes large. For a tubular photo-bioreactor, low density polyethylene (LDPE) film and glass have significantly higher NERs than rigid polymers such as poly-methyl methyl-acrylate (acrylic). Using a hypothetical improved micro-algal H2 generation efficiency of 5 %, a NER ∼ 6 can be obtained for LDPE film and for glass. For mechanical and assembly reasons LDPE film is the material of choice. These results show that photo-bio-hydrogen could be a viable H2 generation technology. (authors)
[en] Research highlights: → Combined absorption heat pump - methanol steam reforming system. → Determine optimum absorption heat pump (AHP) step number. → Decrease of GHSV caused increase of feasibility criterion up to AHP step number 3. → Increase of S/C shifted feasibility criterion peak from AHP step number 3 to 2. -- Abstract: This paper presents an evaluation of combined absorption heat pump (AHP) and methanol steam reforming (MSR) system. To measure the effectiveness of this combined system, a feasibility criterion was proposed, which measured the ratio between net energy gain obtained by MSR reaction over energy required by AHP system. By using the proposed feasibility criterion, optimum AHP step number could be determined. Other parameters pertaining to both AHP and MSR system were also determined and calculated. In particular, discussions would focus on the effects of steam-carbon molar ratio (S/C) and gas hourly space velocity (GHSV) of experimental MSR upon feasibility criterion of combined system. It was shown that the decrease of GHSV caused the increase of feasibility criterion up to the AHP step number 3; meanwhile, the increase of S/C resulted in the shifting of feasibility criterion peak from AHP step number 3 to 2.
[en] We estimate the energy content, the operational energy inputs, and the net energy ratio (NER) of an industrial tubular photo bioreactor used for the photosynthetic production of H2 by micro-algae. The calculated H2 output of the photo bioreactor is based on a range of algal photosynthetic H2 generation efficiencies, and on the application of standard theory for tubular solar collectors. Small diameter reactors have a low NER as the mixing energy becomes large. For a tubular photo bioreactor, low density polyethylene (LDPE) film and glass have significantly higher NERs than rigid polymers such as poly-methyl methyl-acrylate (acrylic). Using a hypothetical improved micro-algal H2 generation efficiency of 5 %, a NER ∼ 6 can be obtained for LDPE film and for glass. For mechanical and assembly reasons LDPE film is the material of choice. These results show that photo bio-hydrogen could be a viable H2 generation technology. (authors)
[en] Highlights: • High biomethane potential of slaughterhouse waste (SHW) in the US is calculated. • Technical challenges in using SHW in anaerobic digestion (AD) have been addressed. • Co-digestions of SHW with other wastes in AD are presented and discussed. • AD systems treating SHW from typical slaughterhouses have been proposed. - Abstract: Anaerobic Digestion (AD) is a promising technology to treat slaughterhouse waste (SHW) for the bioenergy production, nutrient recovery, and pathogen reduction. Three scenarios of estimating the biomethane potential from SHW of the US and the individual States have been conducted in this study. The US meat producers discharged 18.4 million metric ton (MT) SHW in 2016, which can potentially generate 22.7 × 109 kWh of biomethane. In Texas State, up to 2.3 × 109 kWh year−1 of energy can be potentially produced from AD of SHW and up to 106.3% of natural gas currently used in the Nebraska State for electricity generation can potentially be replaced with biomethane produced from the AD of its SHW. The technical challenges using SHW as the feedstock of AD process in the US have been summarized, including nitrogen and sulfur inhibition, foaming, sterilization, digestate disposal, supply chain etc. In addition, case studies were conducted by proposing an AD plant treating SHW from a typical slaughterhouse in a U.S. State that mostly processes the broiler, swine, and bovine. In our case studies, a net energy of 17,009–85,278 kWh d−1 is estimated to be generated from such AD plant. Therefore, producing biomethane from SHW can significantly promote bioenergy production in the US, thus enhancing the quick reach of bioenergy development targets set at the Federal and State levels, while overcoming the technical and management barriers of using SHW.
[en] Surface polaritons related to a chiral medium which supports backward waves are considered. The conditions for the existence of surface polariton modes on the surface of a half-space or slab of such a chiral medium are studied. Numerical results for pure and quasi surface polariton modes are given for three typical chiral slabs. The net energy flux of the guided waves related to these surface polaritons may flow forward, backward or even be stopped. Surface polaritons of such a chiral slab can be used to slow down the light effectively
[en] In this paper, we propose an electron acceleration by using an intense short pulse laser and a thin slab plasma separator. When an intense short pulse laser illuminates electrons in vacuum, the electrons are accelerated by the ponderomotive force at the front of laser pulse and the electrons accelerated loose their energies at the tail of laser pulse. This is one of serious problems in the ponderomotive electron acceleration. In order to suppress the energy loss, we propose an overdense plasma separator to extract the electrons before entering the deceleration region of laser pulse. In our electron acceleration mechanism, only the laser is reflected by the overdense plasma separator and the electrons pass through the plasma separator. Consequently, the electrons can obtain a net energy after the interaction with the laser pulse
[en] Exergy analysis is important for energy resource utilization, because exergy, which is a way to a sustainable future, is a part of the energy analysis. Exergy analysis starts to play a role in several countries in developing energy policy. This paper deals with the exergetic assessment of the cotton stalk (CS) production. In this regard, Turkey, which is one of the eight countries producing 85% of the world's cotton, is given as an application country first. Energy and exergy relations used in the analysis are then presented. Finally, the Turkish CS production in 2003 is evaluated using energy and exergy analyses method, while the results obtained are discussed. The values for the net energy and exergy gained are obtained to be about 49,146 and 59,395 MJ/ha, respectively. Turkey's total energy and exergy are estimated to be 75.45 and 81.87 PJ. It may be concluded that this amount of energy is equal to 7.77% and 2.38% of Turkey's primary energy production and consumption in the same year, respectively. The overall mean energy and exergy efficiencies of the cotton production in the year studied are found to be 33.06% and 33.12%, respectively. It is also expected that the results of this study will be helpful in developing highly applicable and productive planning for energy policies