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  • Articles  (50)
  • Other low-carbon energy technologies  (35)
  • Solar energy technologies  (15)
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  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (50)
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  • 1
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    Review of heat pipe heat exchangers for enhanced dehumidification and cooling in air conditioning systems (2016)
    Oxford University Press
    Details
    Publication Date: 2016-08-26
    Description: Heat pipe heat exchangers could be employed as run-around coils in air conditioning systems for enhanced dehumidification and cooling. This article reviews some of the works conducted on the cooling and dehumidification aspects in various air conditioning systems. They have been proved to be effective in enhancing dehumidification and reducing air conditioning costs especially in hot and humid tropical countries.
    Keywords: Other low-carbon energy technologies
    Print ISSN: 1748-1317
    Electronic ISSN: 1748-1325
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 2
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    Towards clean and sustainable distributed energy system: the potential of integrated PEMFC-CHP (2016)
    Oxford University Press
    Details
    Publication Date: 2016-08-26
    Description: The mitigation options to meet the ambitious carbon reduction targets set by the UK government are discussed in this paper, including the use of carbon capture and storage (CCS) technology, clean renewable energy integration and a proposed system of integrated fuel cell combined heat and power (FC-CHP) technology. Analysis shows that the use of CCS technology within the current infrastructure can abate half the electricity-associated CO 2 emissions; however, this comes at a high cost penalty. The emissions associated with domestic heat cannot be prevented without changes in the energy infrastructure. Hydrogen-powered fuel cells can provide clean energy at a range of scales and high efficiencies, especially when employed with a CHP system. However, production of CO 2 -free hydrogen is essential for fuel cell technology to contribute substantially to a low carbon economy globally. In this work, three methods were investigated for small-scale distributed hydrogen production, namely steam methane reforming, water electrolysis (WE) and cold plasma jet (CPJ). The criteria used for comparisons include the associated CO 2 emissions and the cost of energy production. CPJ decomposition of methane shows a high potential when combined with integrated FC-CHP technology for economically viable and CO 2 -free generation of energy, especially in comparison to WE. Including the value of the solid carbon product makes the plasma system most attractive economically.
    Keywords: Other low-carbon energy technologies
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 3
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    Endoreversible modeling and optimization of multistage isothermal chemical engines under linear mass transfer law via Hamilton-Jacobi-Bellman theory (2016)
    Oxford University Press
    Details
    Publication Date: 2016-08-26
    Description: A multistage continuous isothermal endoreversible chemical engine system with a finite driving fluid is investigated in this paper, and the mass transfer law obeys the linear mass transfer law [ $$g\propto \mathrm{\Delta }\mu $$ ]. Under the condition that both the initial time and the initial key component concentration in the driving fluid are fixed, the maximum power output of the multistage chemical engine system and the corresponding optimal concentration configuration of the key component in the driving fluid are derived by applying Hamilton–Jacobi–Bellman (HJB) theory, and numerical examples for three different boundary conditions are given. The results show that the difference between the chemical potential of the key component and the Carnot chemical potential for the maximum power output is a constant, and the key component concentration in the driving fluid decreases with the increase of time nonlinearly; when both the process period and the final concentration of the key component are fixed, there is an optimal control strategy for the maximum power output of the multistage chemical engine system, and the maximum power outputs of the system and the corresponding optimal control strategies are different for different final concentrations. The obtained results can provide some theoretical guidelines for the optimal designs and operations of practical energy conversion systems.
    Keywords: Other low-carbon energy technologies
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 4
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    Alternative coating technologies for metal-ceramic nanocomposite films: potential application for solar thermal absorber (2016)
    Oxford University Press
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    Publication Date: 2016-08-26
    Description: Metal–ceramic nanocomposite films for solar absorbers have been obtained by electro-deposition. This coating technique uses a mixed solution of nickel nanoparticles and sub-micron alumina particles. The relative ratio of Ni-to-Al in these films is varied by tuning the concentration of nickel and alumina particles in the starting solution. Three films with different Ni/Al ratio have been prepared and characterized with X-ray photo-electron spectroscopy and scanning electron microscope. Even in absence of any heat treatment, significant amount of nickel in metallic state has been found in all three samples.
    Keywords: Solar energy technologies
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 5
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    Performance study of a static low-concentration evacuated tube solar collector for medium-temperature applications (2016)
    Oxford University Press
    Details
    Publication Date: 2016-08-26
    Description: With the development of the energy demands, solar energy medium-temperature applications (〉80°C) for refrigeration, building heating, seawater desalination, thermal power generation etc. has become popular research fields. The article presents an investigation on a static low-concentration evacuated tube (LCET) solar collector for medium-temperature applications. Ray trace outcome at the incident angles between 0 and 60° shows that the average optical efficiency can reach 76.9%. The experimental testing was conducted in the medium temperature range of 80 and 140°C which indicates the instantaneous thermal efficiency is still larger than about 30.0%, and the instantaneous exergetic efficiency is 〉5.92%. The results comprehensively indicate the good performance of LCET solar collector for medium-temperature applications.
    Keywords: Solar energy technologies
    Print ISSN: 1748-1317
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 6
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    Thermodynamic analysis and optimization of the Atkinson engine by using NSGA-II (2016)
    Oxford University Press
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    Publication Date: 2016-08-26
    Description: Recently, several studies have been conducted regarding the Atkinson cycle and Atkinson engine which have resulted in various thermal efficiency and output power analysis. In the present study, output power and engine thermal efficiency are maximized via employing the NSGA-II approach and thermodynamic analysis. The multi-objective evolutionary approach on the basis of the NSGA-II method is implemented throughout this work for optimizing the above-mentioned variables. To evaluate the aforementioned goal, two objective functions which comprises the power output ( W ) and cycle efficiency ( ) have been included in the optimization process simultaneously.
    Keywords: Other low-carbon energy technologies
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 7
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    Numerical assessment of energy contribution by building integrated photovoltaics in a commercial/office building refurbishment in UK (2016)
    Oxford University Press
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    Publication Date: 2016-08-26
    Description: The generation and supply of electricity to residential and commercial/office buildings has been well established in different parts of the world for some decades now. However, sources like coal, nuclear and gas turbine electric generators which constitute most of the technologies applied in grid power stations usually involve fossil fuels and carbon dioxide emissions which are not environmentally friendly. As a solution to reduce the global carbon footprint and provide sustainable source of electricity, building-integrated photovoltaics (BIPV) or solar electricity has been identified as one of the most attractive sustainable energy technologies in the building sectors. This research work aims at assessing the energy impact of a grid connected solar electric system integrated in a commercial/office high-rise building in UK for a period of 1 year, by carrying out a numerical evaluation based on measured daily BIPV system energy outputs and the overall electrical energy demand of the applied building before and after the installation of the BIPV system. The results of the assessment showed that BIPV has the capacity to provide ~0.4% of the total electrical energy required in applied building.
    Keywords: Solar energy technologies
    Print ISSN: 1748-1317
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 8
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    Control of micro-CHP and thermal energy storage for minimising electrical grid utilisation (2016)
    Oxford University Press
    Details
    Publication Date: 2016-02-05
    Description: The efficient use of combined heat and power (CHP) systems in buildings presents a control challenge due to their simultaneous production of thermal and electrical energy. The use of thermal energy storage coupled with a CHP engine provides an interesting solution to the problem—the electrical demands of the building can be matched by the CHP engine, while the resulting thermal energy can be regulated by the thermal energy store. Based on the thermal energy demands of the building the thermal store can provide extra thermal energy or absorb surplus thermal energy production. This paper presents a multi-input multi-output inverse-dynamics-based control strategy that will minimise the electrical grid utilisation of a building, while simultaneously maintaining a defined operative temperature. Electrical demands from lighting and appliances within the building are considered. In order to assess the performance of the control strategy, a European Standard validated simplified dynamic building physics model is presented that provides verified heating demands. Internal heat gains from solar radiation and internal loads are included within the model. Results indicate the control strategy is effective in minimising the electrical grid use and maximising the utilisation of the available energy when compared with conventional heating systems.
    Keywords: Other low-carbon energy technologies
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 9
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    Energy performance of a residential building-integrated micro-cogeneration system upon varying thermal load and control logic (2016)
    Oxford University Press
    Details
    Publication Date: 2016-02-05
    Description: This work investigated the energy performance of a 6.0 kW el micro-cogeneration device integrated with a multi-family house by using a dynamic simulation software. The analyses were performed upon varying the climatic conditions, the control logic of the cogeneration unit, the number of flats composing the building and the target temperature of hot water produced for heating purposes. The simulation data were used to compare the performance of the proposed system with those of a conventional system composed of a natural gas-fired boiler and a power plant mix connected to the electric grid from an energy point of view.
    Keywords: Solar energy technologies
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 10
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    Thermodynamic optimization of a triple-shaft open intercooled, recuperated gas turbine cycle. Part 2: power and efficiency optimization (2016)
    Oxford University Press
    Details
    Publication Date: 2016-02-05
    Description: The power and the efficiency of a triple-shaft open intercooled, recuperated gas turbine cycle are analyzed and optimized based on the model established using thermodynamic optimization theory in Part 1 of this paper by adjusting the low-pressure compressor inlet relative pressure drop, the mass flow rate and the distribution of pressure losses along the flow path. First, the power output is optimized by adjusting the intercooling pressure ratio, the air mass flow rate or the distribution of pressure losses along the flow path. Second, the thermodynamic first-law efficiency is optimized subject to a fixed fuel flow rate and a fixed overall size by seeking the optimal intercooling pressure ratio, the compressor inlet pressure drop and optimal flow area allocation ratio between the low-pressure compressor inlet and the power turbine outlet. The numerical examples show that increase in effectiveness of intercooler increases power output and its corresponding efficiency and increase in effectiveness of recuperator decreases power output appreciably but increases its corresponding efficiency; there exist an optimal low-pressure compressor inlet relative pressure drop and an optimal intercooling pressure ratio, which lead to a maximum power. For a fixed fuel mass rate and a fixed overall area of low-pressure compressor inlet and power turbine outlet, maximum thermodynamic first-law efficiency is obtained by optimizing low-pressure compressor inlet relative pressure drop and intercooling pressure ratio. The double-maximum thermodynamic first-law efficiency is obtained by searching optimal flow area allocation between low-pressure compressor inlet and power turbine outlet.
    Keywords: Other low-carbon energy technologies
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 11
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    Transient simulation of a solar absorption cooling system (2016)
    Oxford University Press
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    Publication Date: 2016-02-05
    Description: With non-renewable energy sources depleting quickly, solar energy could prove a viable option owing to its abundance and eco-friendliness. Modeling and simulation of a solar energy-driven single-stage absorption chiller was carried out using the transient simulation software ‘TRNSYS’. An evacuated tube collector coupled with an insulated tank served as heat source for the absorption chiller. Experiments were conducted to evaluate the efficiency parameters of the collector as well as the loss coefficient for the storage tank. These parameters along with standard chiller performance data were used to model the system. The influence of climatic conditions, storage capacity and various control schemes with and without auxiliary heating on the output of the system is analyzed and presented in the paper.
    Keywords: Other low-carbon energy technologies
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 12
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    Thermochemical cooling system based on adsorption pumping pipe (2016)
    Oxford University Press
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    Publication Date: 2016-02-05
    Description: Based upon the theoretical principle of the thermochemical energy storage pumping pipe system, a new cooling system has been presented. In order to analyse the performance and design of the system based on adsorption pumping pipe process, a simplified mathematical model is developed. Both simulation and experimental results are given and discussed. The comparison of various methods (ammonium dissolves, evaporation of CO 2 , etc.) showed that it is the simplest and most reliable to use adsorbents such as zeolite in this cooling system. A total of 250 g zeolite 13X could reduce the temperature of 330 ml by 15°C in 2–3 min (for beverage self-cooling applications). For future work, a large scale demonstration system is required to prove the viability and long term performance of thermochemical cooling/energy storage system.
    Keywords: Other low-carbon energy technologies
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 13
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    Thermal modeling and experimental validation of solar tunnel dryer: a clean energy option for drying surgical cotton (2016)
    Oxford University Press
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    Publication Date: 2016-02-05
    Description: A battery of three walk-in-type solar tunnel dryers was commissioned at M/s Cotton Product of India, Udaipur (27' 42°N, 75' 33°E), for drying surgical cotton. Each dryer has a drying capacity of 600 kg of surgical cotton, with moisture content reduction averaging 40 to 5% (wb) in a single solar day. This investigation presents thermal modeling, energy and exergy analyses for a walk-in-type solar tunnel dryer. The predicted drying air temperature was 2–3°C higher than experimental values. The experimental and predicted values for energy efficiency of the drying process were found to vary from 1.051–1.793% and 1.298–2.224%, respectively, whereas those of exergy efficiency were found to vary from 0.039–0.072% and 0.030–0.058%, respectively. An economic analysis of the tunnel dryer under consideration has also been completed, and its greenhouse-gas mitigation potential has been calculated to better determine its usefulness as a replacement for light diesel oil (LDO) and liquefied petroleum gas (LPG) drying units. It was found that the payback periods of the solar tunnel dryer, when replacing LDO and LPG units, were 3.03 and 2.26 years, respectively whereas the benefit–cost ratio was 2.12 with respect to LDO units and 3.03 with respect to LPG units. Additionally, it was determined that a single unit of a tunnel dryer can reduce CO 2 emissions by 12.15 tons per year when replacing an LDO unit, and by 6.72 tons per year when replacing an LPG unit.
    Keywords: Solar energy technologies
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 14
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    Thermodynamic optimization of a triple-shaft open intercooled-recuperated gas turbine cycle. Part 1: description and modeling (2016)
    Oxford University Press
    Details
    Publication Date: 2016-02-05
    Description: Considering the flow processes of the working fluid with the pressure drops, a thermodynamic model for a triple-shaft open intercooled-recuperated gas turbine cycle is established using thermodynamic optimization theory in Part 1 of this paper. The relative pressure drops associated with the flow through various cross-sectional areas are derived as functions of the low-pressure compressor inlet relative pressure drop. The analytical formulae of the cycle's power and efficiency are derived. The performance of the model cycle is optimized by adjusting the compressor inlet pressure, the mass flow rate and the distribution of pressure losses along the flow path in Part 2 of this paper.
    Keywords: Other low-carbon energy technologies
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 15
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    Economic feasibility evaluation of solar distillation systems based on the equivalent cost of environmental degradation and high-grade energy savings (2016)
    Oxford University Press
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    Publication Date: 2016-02-05
    Description: Solar distillation systems have been found economically feasible in desalination of saline water. It is a simple and cost-effective low-carbon technology. Free of cost, non-polluting, non-exhaustible solar energy is used to produce distilled water inside a solar still. In this article, the usual economic analysis model has been modified by incorporating the factor of equivalent cost of environmental degradation and high-grade energy savings for solar stills. The unit cost of desalination of saline water is estimated to be US$ 0.034/L corresponding to 30.42% energy efficiency of a passive solar still. It decreases to US$ 0.024/L using the modified model. Double-slope passive solar stills desalinate at a lowest cost of US$ 0.007/L. Due to higher capital cost of active solar stills, the unit cost of desalination of saline water is higher even if productivity is more. Effects of variation of energy efficiency, useful life, capital cost, etc. are also studied. The payback periods of the passive solar still are found to be in the range of 1.1 to 7.6 years if the selling price of distilled water decreases from US$ 0.18 to 0.04/L.
    Keywords: Solar energy technologies
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 16
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    Power and power density analyzes of an endoreversible modified variable-temperature reservoir Brayton cycle with isothermal heat addition (2016)
    Oxford University Press
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    Publication Date: 2016-02-05
    Description: The mistakes in recent literatures are analyzed, and a new model for an endoreversible closed modified Brayton cycle with isothermal heat addition coupled to variable-temperature reservoirs is established using finite-time thermodynamics in this paper. The range of isothermal heat addition modification is determined, and the analytical formulae of the dimensionless power output, thermal efficiency and dimensionless power density of the cycle are derived. The effects of the cycle parameters on the global performances of power output and power density and the performances at maximum power design and maximum power density are analyzed by numerical calculations. The results show that there exist optimal compressor pressure ratios, respectively, which lead to maximum dimensionless power output and maximum dimensionless power density, that the optimal compressor pressure ratio and the thermal efficiency at maximum power design are always smaller than the corresponding ones at maximum power density design, and that dimensionless power output and maximum specific volume at maximum power design are always bigger than the corresponding ones at maximum power density design. The results imply that the power density design possesses the advantages such as smaller equipment volume and higher thermal efficiency at the cost of disadvantages such as bigger compressor pressure ratio and power output loss. Maximizing the power density gives a compromise between power and the size of the engine. The calculations also show that an endoreversible closed modified Brayton cycle with isothermal heat addition cannot work at the maximum thermal efficiency design point.
    Keywords: Other low-carbon energy technologies
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 17
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    Effects of thermocouples physical size on the performance of the TEG-TEH system (2016)
    Oxford University Press
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    Publication Date: 2016-08-26
    Description: The effects of thermocouples physical size on the performance of a thermoelectric heat pump (TEH) driven by a thermoelectric generator (TEG) device are investigated in this article. The physical size refers to the length and the cross-sectional area of the thermocouples. The performance analysis is multiobjective, including stable electrical current, heating load, coefficient of performance, maximum heating load and maximum heating temperature difference. A characteristic parameter, i.e. area–length ratio, is defined to describe the thermocouples physical size. The influences of the parameter are analyzed by detailed numerical examples. A practical example is proposed to show how to select appropriate thermoelectric modules (TEMs) to construct a high-performance TEG–TEH system satisfying different requirements. The results show that an improvement in its performance is possible by optimizing internal physical size of thermocouples. The conclusion obtained could be used for the selection of TEMs and the design of the TEG–TEH system.
    Keywords: Other low-carbon energy technologies
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 18
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    Effect of the working liquid to the capillary pumped loop performance (2016)
    Oxford University Press
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    Publication Date: 2016-08-26
    Description: The purpose of this paper is to present a theoretical analysis of the capillary pumped loop (CPL) performance using different working liquids. CPL is a passive heat transfer device, using no mechanical pump to circulate the working liquid, usually composed of a liquid tank, an evaporator, a condenser, a liquid and a vapor line. Heat load is applied on the external surface of the evaporator, partially transferred to the wick inside. Because of this heat load capillary forces are developed inside the porous structure, due to meniscus formation between liquid and vapor surface of the liquid, causing a pressure oscillation capable to pump the flow out of the evaporator. In this paper CPL performance is evaluated using different working liquids, such as water, ammonia, acetone and freon-134. These have different thermophysical properties such as latent heat, viscosity and density, causing different behavior when used as working liquid. Water was found more stable for higher temperature differences, due to higher latent heat of vaporization, while ammonia could take advantage of its viscosity for small temperature differences.
    Keywords: Other low-carbon energy technologies
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  • 19
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    Design and optimization of a thermoacoustic heat engine using reinforcement learning (2016)
    Oxford University Press
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    Publication Date: 2016-08-26
    Description: The thermoacoustic heat engine (TAHE) is a type of prime mover that converts thermal power to acoustic power. It is composed of two heat exchangers (the devices heat source and sink), some kind of porous medium where the conversion of power takes place and a tube that houses the acoustic wave produced. Its simple design and the fact that it is one of a few prime movers that do not require moving parts make such a device an attractive alternative for many practical applications. The acoustic power produced by the TAHE can be used to generate electricity, drive a heat pump or a refrigeration system. Although the geometry of the TAHE is simple, the behavior of the engine is complex with 30+ design parameters that affect the performance of the device; therefore, designing such a device remains a significant challenge. In this work, a radical design methodology using reinforcement learning (RL) is employed for the design and optimization of a TAHE for the first time. Reinforcement learning is a machine learning technique that allows optimization by specifying ‘good’ and ‘bad’ behavior using a simple reward scheme r . Although its framework is simple, it has proved to be a very powerful tool in solving a wide range of complex decision-making/optimization problems. The RL technique employed by the agent in this work is known as Q-learning. Preliminary results have shown the potential of the RL technique to solve this type of complex design problem, as the RL agent was able to figure out the correct configuration of components that would create positive acoustic power output. The learning agent was able to create a design that yielded an acoustic power output of 643.31 W with a thermal efficiency of 3.29%. It is eventually hoped that with increased understanding of the design problem, in terms of the RL framework, it will be possible to ultimately create an autonomous RL agent for the design and optimization of complex TAHEs with minimal predefined conditions/restrictions.
    Keywords: Other low-carbon energy technologies
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 20
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    Calculations of effectiveness factors and the criteria of mass transfer effect for high-temperature methanation (HTM) catalyst (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: Natural gas is an extremely important bridge fuel to a low-carbon energy economy for improving local air quality. Coal to synthetic natural gas (SNG) is an effective way to convert the high-carbon energy (coal) into the low-carbon energy with rich hydrogen (natural gas). For the modern coal to SNG industry, the high-temperature methanation (HTM) catalyst plays an important role, and the advanced evaluation process should necessitate the elimination of mass transfer effect. Some simple but effective model catalysts, such as slab and sphere, can be very helpful in defining the reaction conditions, and thus facilitating the evaluation process for real HTM catalysts. In this work, slab and sphere model catalysts were adopted to derive mass transfer and reaction-coupled equations, the numerical methods were used to solve the coupled equations for the concentration profiles in catalysts, and the effectiveness factors were accordingly calculated. By taking advantage of the Thiele module and the Weisz–Prater module , the criteria for the elimination of mass transfer effect in the HTM catalyst evaluation process were successfully defined. This work also complements the Weisz–Prater criterion by incorporating ‘negative reaction orders’.
    Keywords: Other low-carbon energy technologies
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 21
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    A novel low-carbon space conditioning system incorporating phase-change materials and earth-air heat exchangers (2015)
    Oxford University Press
    Details
    Publication Date: 2015-08-16
    Description: The energy expended for conditioning buildings around the world is worryingly large and increasing every year. Currently, almost half of houses around the world use some type of energy-expensive conventional air-conditioning system. These systems are high emitters of gases such as carbon dioxide and so high contributors to climate change. Consequently, alternatives must be considered. Earth–air heat exchangers (EAHEs) and phase-change materials (PCMs) may be options; they have, however, limitations. This paper proposes a novel hybrid space-conditioning system combining EAHEs with PCMs, which uses surfaces as sources of heating or cooling to provide better temperature distribution across a space and comfort enhancement with low energy use. The idea is to use an EAHE to provide cool air to discharge the PCM, consequently helping to overcome most of the limitations of both strategies. Two of a series of experiments undertaken to test the proposed system are reported in this article. The EAHE + PCM system compared with a reference room could decrease temperature swings by up to 47%. The system was proved to work although further work is required to make it commercially viable.
    Keywords: Other low-carbon energy technologies
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    Towards the generation of distributed electric power: self-consumption with net balance (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: The results and considerations on one self-consumption photovoltaic installation with net balance in Granada (South of Spain) are presented and discussed in this paper. The use of the building (one faculty) makes it optimal for this kind of consumption. Finally, the potential benefits and problems of self-consumption with net balance are presented.
    Keywords: Solar energy technologies
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    Numerical investigation of turbulent flow heat transfer and pressure drop of AL2O3/water nanofluid in helically coiled tubes (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: Passive convective heat transfer enhancement can be achieved by improving the thermo-physical properties of the working fluid, changing flow geometry or both. This work presents a numerical study to investigate the combined effect of using helical coils and nanofluids on the heat transfer characteristics and pressure losses in turbulent flow regime. The developed computational fluid dynamics models were validated against published experimental data and empirical correlations. Results have shown that combining the effects of alumina (Al 2 O 3 ) nanoparticles and tube coiling could enhance the heat transfer coefficient by up to 60% compared with that of pure water in straight tube at the same Reynolds number. Also, results showed that the pressure drop in helical coils using Al 2 O 3 nanofluid for volume fraction of 3% was six times that of water in straight tubes (80% of the pressure drop increase is due to nanoparticles addition), while the effect of Reynolds number on the pressure drop penalty factor was found to be insignificant.
    Keywords: Other low-carbon energy technologies
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    Readdressing working fluid selection with a view to designing a variable geometry ejector (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: A number of factors influence the performance of an ejector, e.g. working fluid, geometry and operating conditions. In the present work, six low-environmental-impact working fluids were evaluated for their use in an ejector cooling system running on low-temperature thermal energy. The numerical analysis was based on a model applying the 1D constant-pressure mixing theory. Ejector performance was assessed for the temperatures of the generator, evaporator and condenser in the range of 80–120°C, 5–15°C and 25–40°C, respectively. The results indicated that owing to its high coefficient of performance and moderate operating pressures throughout the entire ejector cycle, isobutane is a good choice for a refrigerant. The area ratio required for running the ejector in critical mode, under changing operating conditions, varied in a significant range regardless of the selected refrigerant. This clearly indicates the importance of a variable geometry ejector design to strengthen the position of ejector cooling systems among other refrigeration technologies.
    Keywords: Other low-carbon energy technologies
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    Constructal optimization of a disc-shaped body with cooling channels for specified power pumping (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: The thermal performance of a disc-shaped heat generation body with cooling channels is investigated by using constructal theory based on previous model of heat convection on a disc and previous analytical method of heat conduction on a disc. By taking minimum dimensionless maximum thermal resistance as optimization objective, the optimal aspect ratio of the elemental sector in the radial-pattern disc is obtained for the specified power pumping of the elemental sector; the optimal width ratio of the first-order and elemental cooling channels and the optimal dimensionless radius of the elemental sector are obtained for the specified power pumping of the disc. There exists a critical radius of the disc to determine whether the radial-pattern design and branched-pattern design should be adopted. These conclusions are different from those obtained by Wechsatol et al. 's model, and the essential reason for these differences is that the power pumping is specified in this article, but not the specified flow rate number in Wechsatol et al. 's model. Finally, the assumption about the heat capacity of the coolant and the thermal conductivity of the disc is validated. An analytical method is introduced in this article, which can provide another thought for the constructal optimization of disc with heat convection. The optimal constructs of the discs are obtained for the specified power pumping, which provides some different guidelines for the design of disc with heat convection.
    Keywords: Other low-carbon energy technologies
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    Theoretical investigation of hot box solar cookers having conventional and finned absorber plates (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: In this paper, solar box cookers with ordinary and finned absorber plates are theoretically investigated in terms of thermodynamic performance parameters. For a typical summer and winter day, temperatures of solar cooker components such as glass cover, internal air, absorber plate, cooking vessel and the liquid are determined theoretically versus time. The analysis is carried out for conventional and finned absorber plates, and accuracy of the results is verified by a previously published experimental work. Energy and exergy efficiencies of box-type solar cookers are plotted versus time for various cases. The methodology presented in this paper enables to make a preliminary evaluation of ordinary and modified solar box cookers with respect to changes in main environmental parameters such as temperature and illumination intensity. Some recommendations are also made to enhance the power outputs of the aforementioned solar cookers.
    Keywords: Solar energy technologies
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    Design of a celestial vault image capture device for its application in the solar radiation field (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: The sun is the more plentiful source of natural power that we have in the Earth. However, the amount of radiation reaching the Earth's surface depends on astronomical and climatic factors. One of the factors exerting a greater influence is cloudiness. For that reason, it is important to quantify its influence on solar radiation. According to that, in this work, a prototype to capture images of the celestial vault is designed and implemented to be able to measure parameters related to the cloud properties and, later, to determine their influence on solar radiation.
    Keywords: Solar energy technologies
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    Investigation of concentrating and nonconcentrating evacuated tube solar water heaters using 2D particle imaging velocimetry (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: Under transient climatic conditions, solar water heaters using heat pipes are more effective at capturing incident solar radiation than other equivalent sized solar water heaters. The cost must be reduced to improve uptake of such systems. To investigate two methods were considered by this study: thermosyphon fluid flow and reflective concentrators. A physical reconfigurable laboratory model of the manifold and associated condensers of a heat-pipe-evacuated tube system were fabricated; fluid circulation was via thermosyphonic action, particle imaging velocimetry derived velocity maps and the use of concentrators was simulated. When condenser spacing was doubled, the Nusselt number increased by 43%, the velocity by 55% but the heat transfer efficiency of the model manifold decreased by 9%. Potential annual energy savings of 10 207 GWh could be realized if such systems could be successfully fabricated.
    Keywords: Solar energy technologies
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    Computational study of a 2D capillary pump evaporator (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: Capillary pump loop (CPL) is a two-phase heat transfer device considered as a useful solution for thermal control applications in spacecrafts, satellites and electronic components. The purpose of this paper is to study various aspects of the working state of the CPL evaporator. A two-dimensional computational model was developed in order to analyze the flow and the phase transformation inside a cylindrical evaporator. At the present analysis, different cases were studied by changing liquid saturation temperature, inclination angle of the evaporator and the length of the porous heated wick. Water, ammonia, acetone and freon-134 were used as working liquids for numerical experiments. Results present the evaporator capability to vaporize each working liquid and find out its possibility of dry-out causing failure. This information is useful in choosing the best working liquid for an evaporator, enabling bigger amounts of heat to be transferred.
    Keywords: Other low-carbon energy technologies
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    Design guideline for application of earth-to-air heat exchanger coupled with solar chimney as a natural heating system (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: In the present paper, design of solar chimney (SC) and earth-to-air heat exchanger (EAHE) to meet the thermal need of flat buildings are studied regarding adaptive thermal comfort criteria. Investigation on the effects of geometric features shows that the design of SC with the air gap and outlet sizes of 0.2 m and also EAHE with the diameter and length of 0.5 and 25.0 m reveals better performance. Thermal comfort analysis shows that the SC is capable to power the underground heating system during few hours of the sunny days even at the ambient temperature as low as 0°C and the heating demand of 1000 W without needing the auxiliary devices. In addition, the required numbers of SCs and the underground air channels are strongly influenced by environmental outdoor conditions and heating demand of building and are approximately calculated by: $$\hbox{ room }\phantom{\rule{0.08em}{0ex}}\hbox{ volume/50 }\phantom{\rule{0.08em}{0ex}}\hbox{ and }\phantom{\rule{0.08em}{0ex}}\hbox{ 2 }\times (\hbox{ room }\phantom{\rule{0.08em}{0ex}}\hbox{ volume/50 })+\hbox{ 1, }$$ respectively.
    Keywords: Other low-carbon energy technologies
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    Numerical analysis of solar-assisted seasonal 'open' thermochemical heat storage (2015)
    Oxford University Press
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    Publication Date: 2015-05-13
    Description: In the last decade, interest in heat storage systems has been increasing. These systems will have increasing importance for utilization of solar energy in domestic heating systems. As solar energy is a diurnal cyclic resource, storing excess solar energy for long- or short-term periods will both increase the utilization of solar energy systems and decrease fossil fuel consumption. The relatively new heat storage method using thermochemical storage has shown some significant advantages such as low heat loss (-〉 zero), high heat storage density and low space requirement. These important properties make thermochemical storage a promising alternative for long-term energy storage. In the present study, a numerical investigation on ‘open’ seasonal thermochemical storage has been undertaken. The simulation results show that the volume/mass of the absorbent, mass flow rate and relative humidity of air have significant importance on the reaction kinetics and system performance during the system discharging process. Conversely, total collector area, solar radiation and mass flow rate of air are important parameters during the charging process. The results conclude that, overall, reactor design is the most important factor for storage performance. In addition, reaction advancement ( X ) has a significant importance on process efficiency.
    Keywords: Other low-carbon energy technologies
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    Solar low-pressure turbo-ejector Maisotsenko cycle-based power system for electricity, heating, cooling and distillation (2015)
    Oxford University Press
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    Publication Date: 2015-05-13
    Description: The article describes the innovative solutions of power, heating and cooling generation utilizing low- or medium-grade heat sources. The proposed technology based on the well-known irreversible Brayton cycle and the revolutionary Maisotsenko cycle (M-cycle) operates at atmospheric or sub-atmospheric pressures. Such energetic systems are simple and reliable and utilize moisture-saturated air as a working fluid. The ejector replacing the mechanical compressor in the Brayton cycle system allows increasing the cycle work by three to five times at the constant airflow. At the same time, the utilized heat serves for simultaneous heating and cooling production that makes the system economically viable and environmentally friendly with the increased integral performance. For system's performance improvement, the schematic and the cycle were upgraded allowing the off-the-shelf components to be employed and replace the electrically driven fan with fluidic jet-fan that served for energy saving of the innovative turbo-ejector system operation.
    Keywords: Solar energy technologies
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    Optimization of building-integrated photovoltaic thermal air system combined with thermal storage (2015)
    Oxford University Press
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    Publication Date: 2015-05-13
    Description: Photovoltaic (PV) combined with phase change material (PV/PCM) system is a hybrid solar system that uses a PCM to reduce the PV temperature and to store energy for other applications. This study aims to increase the integrated PV efficiency of buildings by incorporating PCM while utilizing the stored heat in PCM for controlling indoor conditions. Experiments have been carried out on a prototype PV/PCM air system using monocrystalline PV modules. Transient simulations of the system performance have also been performed using a commercial computational fluid dynamics package based on the finite volume method. The results from simulation were validated by comparing it with experimental results. The results indicate that PCM is effective in limiting temperature rise in PV device and the heat from PCM can enhance night ventilation and decrease the building energy consumption to achieve indoor thermal comfort for certain periods of time.
    Keywords: Other low-carbon energy technologies
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    Thermal energy storage: the role of the heat pipe in performance enhancement (2015)
    Oxford University Press
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    Publication Date: 2015-05-13
    Description: Heat pipes and thermosyphons—devices of high effective thermal conductivity—have been studied for many years for enhancing the performance of solid, liquid and phase change material (PCM) heat stores. However, as the applications of heat storage widen, from micro-electronics thermal control to concentrated solar heat storage and vehicle thermal management, and even for chemical reactor isothermalization, the challenges facing heat storage increasingly are moving from those associated with the ‘standard’ diurnal storage, in itself a problem for low thermal conductivity materials, to response times measured in a few hours or even minutes. While high thermal conductivity metals such as foams can be impregnated with a PCM, for example, to increase local conductivity, the rapid heat input and removal necessitates a more radical approach—heat pipes, possibly with feedback control, with innovative PCM interfaces. This paper reviews the use of heat pipes in conventional and rapid response PCM and liquid or cold storage applications and introduces some novel concepts that might overcome current limitations.
    Keywords: Other low-carbon energy technologies
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    Identifying bottlenecks in charging infrastructure of plug-in hybrid electric vehicles through agent-based traffic simulation (2015)
    Oxford University Press
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    Publication Date: 2015-05-13
    Description: The effect of different charging infrastructure configurations on the electric-driven distance of plug-in hybrid electric vehicles (e-mileage) has been investigated, using an agent-based traffic simulation. Our findings suggest that the same e-mileage can be achieved with fewer charging poles if the poles support charging from several parking slots around them, and the charging cable is switched from one vehicle to the next. We also find that the charging power supported by most Finnish charging stations, 3.7 kW, and the cable switching delay of 1 h seem to be sufficient for effective workplace charging.
    Keywords: Other low-carbon energy technologies
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    Mitigation countermeasures to face urban warming (2015)
    Oxford University Press
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    Publication Date: 2015-02-12
    Keywords: Other low-carbon energy technologies
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    Urban forests and solar power generation: partners in urban heat island mitigation (2015)
    Oxford University Press
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    Publication Date: 2015-02-12
    Description: The urban forest is generally decreasing in areal extent. At the same time, human population is urbanizing and urban areal extent per capita is increasing. Eighty percent of North Americans are now living in urbanized areas. Urban forests directly affect quality of life for residents of cities via the ecosystem services and psychosocial restoration they provide. The urban forest canopy is a key component of reducing the urban heat island, slowing stormwater runoff and making urban environments more efficient and livable. Municipalities in North America are reacting to concerns about urbanization and economic trends by permitting an increasing number of compact developments that may conflict with beneficial Green Infrastructure. Compact development may also present challenges to solar access for solar power generation. This paper identifies and illustrates key strategies to increase urban forest cover and decrease infrastructure conflicts by implementing given innovative design details, detailing specific zoning and code language, and providing best practices from multiple disciplines. These strategies to increase urban forest canopy cover frame a coherent set of ideas to decrease the effects of the urban heat island, increase solar power generation and improve urban quality of life in cities.
    Keywords: Solar energy technologies
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    Analysis of a SrCl2-NH3 solid sorption refrigeration system (2015)
    Oxford University Press
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    Publication Date: 2015-11-07
    Description: The performance of a solid sorption refrigeration system that uses SrCl 2 and NH 3 as the working pair is analysed based on the heat and mass transfer aspects of the solid sorbent reactors (absorber/generator). The transient, heat and mass transfer model duly considers the effects of reactor wall mass and contact conductance between the reactor wall and the bed. A decent comparison is obtained between the theoretical results and published experimental results on a reactor. The complete system consisting of two absorber/generators, condenser, expansion valve and evaporator is then analysed using the heat and mass transfer model of the reactors. Results are obtained in terms of the coefficient of performance (COP) and specific cooling power (SCP). Results show the possibility of optimizing the bed and operating parameters so as to obtain high COP and/or SCP. The bed thickness, sink temperature and the global reaction advancement are found to affect the performance of the system significantly.
    Keywords: Other low-carbon energy technologies
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    Experimental analysis of an unconventional desiccant-based air-conditioning system: the influence of cooling air flow and chiller on the energy and environmental performance (2015)
    Oxford University Press
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    Publication Date: 2015-11-07
    Description: Nowadays, the increasing demand of summer cooling is typically covered by electric chillers, often determining electric peak loads and black-outs. Thus, a wide interest is spreading in small scale natural gas-fired cogenerators driving desiccant-based air-conditioning systems, which represent interesting alternatives to conventional systems based on vapor compression cooling only. In this article, experimental tests performed on an air handling unit (AHU) equipped with a desiccant wheel (DW), coupled to a small scale cogenerator and an electric chiller are described. A new layout of the desiccant-based AHU is investigated, considering a third flow (the cooling air), besides the process air flow and the regeneration one. A cross-flow heat exchanger between process air and cooling air is used; the cooling air, cooled by an adiabatic humidifier, is aimed to precool the process air exiting the DW. The relevant influence of the heat exchanger and of the humidifier, as well as that of the chiller performance, on global primary energy requirements, water consumption and CO 2 equivalent emissions of the system is experimentally evaluated.
    Keywords: Other low-carbon energy technologies
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    A sustainable transport solution for a Slovenia town (2015)
    Oxford University Press
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    Publication Date: 2015-11-07
    Description: Authorities in Slovenia and other EU member states are confronted with problems of city transportation. Fossil-fuel-based transport poses two chief problems—local and global pollution, and dwindling supplies and ever-increasing costs. An elegant solution is to gradually replace the present automobile fleet with electric vehicles (EVs). This article explores the economics and practical viability of the provision of solar electricity for the charging of EVs by installation of economical available Photovoltaic modules. A steep decline in the module, inverter and installation costs is reported herein. Present estimates indicate that for the prevailing solar climate of Celje—a medium-sized Slovenian town—the cost would be only 2 euros and 11 cents per kWh of generated solar electricity.
    Keywords: Other low-carbon energy technologies
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    Study into solar-still performance under sealed and unsealed conditions (2015)
    Oxford University Press
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    Publication Date: 2015-11-07
    Description: Safe water is fundamental to life and sustainable development. Despite modern civilization pacing into the 21st century, global access to safe water is disparate and inadequate particularly in south Asia and Africa. The need of the hour is to promote appropriate technologies, such as desalination, which are economically viable and environmentally conducive. With increasing stress on renewable energy use, technologies based on effectively harnessing solar energy would prove sustainable. Solar-still is a desalination technology that effectively harnesses solar energy. Solar-stills generate safe water from either contaminated and/or brackish water. They are an enabling domestic technology that can suit de-centralized operation and maintenance. Their fundamental dependence on solar energy and relatively low yield has thus far impeded wide-spread adoption. The current article discusses the prospects of solar-stills as a safe-water technology. Subsequently, an innovative low internal-volume stepped solar-still has been commissioned and tested for its productivity under sealed and unsealed conditions. The results of the experimental investigation have been discussed in this article. The salient contribution in this article pertains to the performance of a stepped solar-still under sealed and unsealed conditions. Such an investigation has been found to be crucial, but hitherto unattended to.
    Keywords: Solar energy technologies
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    Reverse flow in natural convection heat pipe solar water heater (2015)
    Oxford University Press
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    Publication Date: 2015-11-07
    Description: System performance of a natural convection (thermosyphon) solar water heater depends on design and setup of collector and storage tank as well as environmental factors such as solar intensity, ambient temperature and wind conditions. The relative height separating the tank and collector mainly influences the magnitude of the thermosyphon flow rates, including both forward and reverse flow at night. In this experimental investigation, an array of evacuated tube heat pipe solar collectors was connected to an insulated hot water storage tank. The effect of the separation height between tank and collectors was investigated and reported. Thermosyphon water flow rates were measured using a dye-injection procedure in both forward and reverse flow directions. The results showed that reverse flow always occurred in the evenings and was about 5–11 times less than forward flow. The overnight mean water temperature drop was independent of the height separating the collectors and storage tank and ranged between 2 and 10°C. The temperature drop was greater when the night was cooler.
    Keywords: Other low-carbon energy technologies
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    Catalytic CO2 conversion via solar-driven fluidized bed reactors (2014)
    Oxford University Press
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    Publication Date: 2014-05-15
    Description: Converting CO 2 and steam (H 2 O) into synthesis gas is a new route to recycle them to fuels. Conversions are performed via a two-step conversion method in which catalysts are heated up and cooled down repeatedly with CO and H 2 as the products. To make the method economic, solar energy is employed to drive conversion systems. A solar-driven system with fluidized bed reactors is proposed for CO 2 conversion in this paper, and numerical models are built to study its performance and find out the optimum working condition. The investigation proves that system is a competent candidate to power the two-step conversion of CO 2 for the carbon recycle and the syngas production.
    Keywords: Other low-carbon energy technologies
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    Micro-scale ORC-based combined heat and power system using a novel scroll expander (2014)
    Oxford University Press
    Details
    Publication Date: 2014-05-15
    Description: Micro-combined heat and power generation (micro-CHP) based on the organic Rankine cycle (ORC) is a flexible technology that allows saving the environment and promoting the economic growth. However, ORC expanders employed recently suffer from key problems including excessive fluid leakage, thermal losses and low isentropic efficiency, and no commercial micro-scale expanders are available in the market and applicable for ORC applications. The possibility of driving a micro-CHP system by solar thermal energy, biomass combustion, waste heat or other clean energy sources allows attaining diversity and security in energy supply as well as decreasing pollutants and gas emissions. In the current work, a solar-biomass-driven micro-CHP system based on the ORC technology is theoretically and experimentally investigated to provide the thermal and electrical needs for residential applications. The micro-CHP system employs an innovative micro-expander utilizing an environmentally friendly working fluid. A numerical model was developed using the Engineering Equation Solver (EES) software to simulate the thermal and electrical performance of the overall CHP system. A parametric study was conducted to investigate the effect of different operational parameters on the CHP system performance. In addition, an experimental set-up was built to test micro-scale ORC-CHP system performance under different conditions using hydrofluoroether (HFE)-7100 fluid. The maximum electric power generated by the expander was in the range of 500 W under a pressure differential of ~4.5 bars. The expander isentropic efficiency has exceeded 80% at its peak operating conditions with no working fluid leakage.
    Keywords: Solar energy technologies
    Print ISSN: 1748-1317
    Electronic ISSN: 1748-1325
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Oxford University Press
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    Passive cooling technology for photovoltaic panels for domestic houses (2014)
    Oxford University Press
    Details
    Publication Date: 2014-05-15
    Description: The efficiency of photovoltaic panels decreases as the panels' temperature increases, which results in deduction of electricity generation. In order to reduce this effect, different cooling methods were proposed and investigated. This paper reviews the previous work on cooling PV cells and concludes that the cost-effectiveness, design feasibility and minimal energy consumption are the important design consideration for cooling systems. Based on these considerations, this paper reports a passive cooling method that utilizes rainwater as cooling media and a gas expansion device to distribute the rainwater. The gas is thermally expanded from receiving solar radiation as such the amount of water it pushes to flow over the PV cells is proportional with the solar radiation it received. The paper reports a design and simulation of such a system for a domestic house application. In the paper, a relationship of the gas chamber size, solar radiation and gas expansion volume was established for evaluation with respect to the variation of gas temperature and the amount of rainwater used for cooling. A heat transfer model was used to evaluate the performance of the cells by cooling with this passive device. The results show that on a design day, the passive cooling system reduces the temperature of the cells and increases electrical efficiency of the PV panel by 8.3%. The payback period of this system is 〈14 years.
    Keywords: Solar energy technologies
    Print ISSN: 1748-1317
    Electronic ISSN: 1748-1325
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 46
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    Performance and defrosting effect study on the air-to-water heat pump with heat storage device (2014)
    Oxford University Press
    Details
    Publication Date: 2014-05-15
    Description: The heat storage device is proposed to avoid the frequent on–off state under partial load, large variation of the supply and return water temperature and long defrosting time of air-to-water heat pump with plate heat exchanger for heating. The heat storage device is composed of a water tank, the inner double-pipe heat exchanger, appendages and the electric heater. The energy storage can reduce on–off times of the compressor. The energy storage and the electric heater can make up the shortage of heating during defrosting. Performance test shows that on–off times for the heat storage device unit compressor under partial load is about four times per hour compared six times per hour for the plate heat exchange unit. Defrosting time is reduced by 78 s by heat storage device unit and 84 s by heat storage device with electric heater unit. More steady running parameters, inlet heating water temperature of heat storage device or heat storage device with electric heater unit is about 35°C, while that of plate heat exchanger reduces to 30.73°C. Therefore, the designed heat storage device can improve the unit performance and is suitable for the new projects with air-to-water heat pumps.
    Keywords: Other low-carbon energy technologies
    Print ISSN: 1748-1317
    Electronic ISSN: 1748-1325
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Oxford University Press
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  • 47
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    Multisource heat pump system from design to operation: the case study of a new school building (2013)
    Oxford University Press
    Details
    Publication Date: 2013-05-09
    Description: Heat pump features can take advantage of better sources than air, for instance the ground heat, solar heat and heat recovery. A multisource system aims to enhance the performances of the heat pump, leading to a significant amount of primary energy being saved. The present work shows data monitoring and analysis for a real working application in northern Italy, for 12 months. The energy balance indicates that the integration of different sources not only increases the thermal performance of the system as a whole but also optimizes the use of each source.
    Keywords: Other low-carbon energy technologies
    Print ISSN: 1748-1317
    Electronic ISSN: 1748-1325
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 48
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    A preliminary testing of a flat panel ground heat exchanger (2013)
    Oxford University Press
    Details
    Publication Date: 2013-05-09
    Description: An experimental setup is devised to investigate the behaviour of a novel type of a horizontal ground heat exchanger (HGHE). The prototype is named ‘flat panel’ and is coupled with a hydraulic closed loop in which warm water is circulating to express the cooling mode from a reversible-cycle heat pump. Several thermal sensors are employed in the experimental field to monitor the ground temperature distribution and the fluid. The behaviour was tested during the summer of 2011, in the continuous and discontinuous operating mode. The HGHE behaviour was monitored in dry and wet conditions; the latter were induced with a dedicated irrigation system. The heat power for the unit exchanging surface dropped down from 140 to 40 W per metre of trench, moving from the start-up to the last period, late in the summer. The minimum was achieved in very hot conditions after long time in the continuous operating mode. When the working mode was switched to discontinuous, the power increased quickly over 50 W/m. Finally, the soil temperature was significantly altered up to 3 m far from the exchanger, and without over-heating conditions at the soil surface. The flat panel was able to involve a large soil volume, and this behaviour in turn enables high-energy performance, at least in the cooling mode.
    Keywords: Other low-carbon energy technologies
    Print ISSN: 1748-1317
    Electronic ISSN: 1748-1325
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Oxford University Press
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  • 49
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    Dynamic thermal modelling of horizontal ground-source heat pumps (2013)
    Oxford University Press
    Details
    Publication Date: 2013-05-09
    Description: A computer program has been developed for numerical simulation of the dynamic thermal performance of horizontally coupled heat exchangers for ground-source heat pumps, taking account of dynamic variations of climatic, load and soil conditions. The program was used to investigate the effects of operating and start times, installation depth and soil freezing on the heat exchanger performance. It is shown that the rate of heat extraction decreases with increasing operating time. Operating a heat pump with an earlier start date in autumn would give rise to a higher amount of cumulative heat extraction. Also, a heat exchanger installed at a shallower depth can provide a larger heat extraction rate at the early stage of heating operation. In addition, soil freezing enhances heat extraction.
    Keywords: Other low-carbon energy technologies
    Print ISSN: 1748-1317
    Electronic ISSN: 1748-1325
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 50
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    Characterization of heat transport processes in geothermal systems (2013)
    Oxford University Press
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    Publication Date: 2013-05-09
    Description: Experimental field tests as well as laboratory tests have been conducted. In addition to field tests, a geothermal laboratory device has been developed. With the help of this device, the heat transport processes in different geological and hydrogeological conditions can be simulated. The different types of heat transport mechanisms in geothermal systems can be characterized clearly. Furthermore, it is possible to determine the increase of the effective thermal conductivity of a line source with rising groundwater flow velocities. With the geothermal data gathered, common numerical programs are verified and optimized. Therefore, all measured data are reconsidered by numerical back analysis.
    Keywords: Other low-carbon energy technologies
    Print ISSN: 1748-1317
    Electronic ISSN: 1748-1325
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Oxford University Press
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