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With the development of technology, some important developments occur in electrical energy systems. Especially smart grids and micro grids will be an important part of energy systems in the following years. With the increasing use of micro grids, more renewable power plants will be included in the system. However, the production of renewable energy sources varies according to the weather conditions. Therefore, the generated energy is not known beforehand. Increasing single-phase loads (such as electric vehicle charging stations), unpredictable renewable generation and uncertainty of consumption can lead to problems of voltage unbalance in the micro grid. This problem can damage the network in many ways. In this study, the problem of voltage unbalance occurring in the microgrid was tried to be reduced by demand side management. The comfort of the customer should not be affected when demand side management is performed. For this reason, the most suitable load for demand side management is thermostatically controlled loads (TCL). An algorithm has been proposed to reduce voltage unbalance by using these loads. This algorithm was tested with the help of PSCAD/EMTDC program.

Significant amounts of nuclear wastes consisting of plutonium, minor actinides and long lived fission products are produced during the operation of commercial nuclear power plants. Therefore, the destruction of these wastes is very important with respect to public health, environment and also the future of nuclear energy. In this study, transmutation of minor actinides (MAs) discharged from LMFBR spent fuel in a high power density fusion reactor has been investigated under a neutron wall load of 10 MW/m2 for an operation period of 10 years. Also, the effect of MA percentage on the transmutation has been examined. The fuel zone, containing MAs as spheres cladded with W-5Re, has been located behind the first wall to utilize the high neutron flux for transmutation effectively. Helium at 40 atm has been used as an energy carrier. At the end of the operation period, the total burning and transmutation are greater than the total buildups in all investigated cases, and very high burnups (420–470 GWd/tHM) are reached, depending on the MA content. The total transmutation rate values are 906 and 979 kg/GWth year at startup and decrease to 140 and 178 kg/GWth year at the end of the operation for fuel with 10% and 20% MA, respectively. Over an operation period of 10 years, the effective half lives decrease from 2.38, 2.21 and 3.08 years to 1.95, 1.80 and 2.59 years for 237Np, 241Am and 243Am, respectively. Total atomic densities decrease exponentially during the operation period. The reductions in the total atomic densities with respect to the initial ones are 79%, 81%, 82%, 83%, 85% and 86% for 10%, 12%, 14%, 16%, 18% and 20% MAs, respectively.

Along with the growth and globalization of the whole world economy since the First Industrial Revolution, the production and use of fossil fuels have led to increased CO2 emissions and, ultimately, significant environmental degradation. The impact of globalization, economic growth, and renewable energy sources on CO2 may show trends with different turning points in developing countries, and estimations may need to follow Fourier-type functions to capture the frequency domain. Therefore, the aim of this study is to examine the effects of renewable energy production, economic globalization, and economic growth on CO2 emissions for Turkey in the period 1971-2006 with Fourier autoregressive distribution lag (ADL) cointegration, DOLS, and Fourier-Granger causality tests. The originality of this study is the estimation of a model of CO2 emissions with a Fourier-type function for the first time. The findings indicate a negative relationship between renewable energy production and CO2 emissions and a positive relationship between economic globalization and economic growth and CO2 emissions. In addition, according to the empirical results, there exists a one-way causality relationship between economic globalization to CO2 and economic globalization to renewable energy production, and there is evidence of a bidirectional causality relationship between economic globalization and economic growth in this study.

AbstractIn this study, a new perspective was introduced to conventional solar pond technology to spread its commercial application. In order to make it more useful with preserving energy efficiency, the brine layers were replaced with the normal freshwater by using a separated transparent partition. Structurally modified three different solar ponds were proposed and numerical investigations were conducted by using discrete ordinate method (DOM). For this, four types of solar ponds were modeled, the first one is the conventional salt‐gradient solar pond and three others are modified versions which are named as “Pure Water Solar Pond.” For all models, a comprehensive finite element method was developed to investigate the daily performance of solar ponds by using commercial software COMSOL. Salt‐gradient solar pond consists of seven layers where one layer is the heat storage zone, five layers are nonconvective zone, and one is the upper convective zone. However, in the modified models, solar ponds consist of two glass layers and one to three pure water zones depending on the model types. The numerical method includes a novel approach to calculate all the zone where absorption, emission, scattering, transmission, convection, and radiation are taken into account. Numerical results for all models were compared with an experiment to correlate the numerical accuracy of the DOM with anisotropic scattering phase function. Results indicate there is a good correlation between these four model approach and the experiment.

Abstract Conventional room air conditioners consume a significant amount of energy, and thereby negatively affect the environment. In this perspective, passive air conditioning systems using phase change material (PCM) are very promising and widely investigated recently. In this study, influence of a PCM-based passive air conditioner on temperature distribution was experimentally studied in a test room under the local tropical climatic conditions. Coconut oil and water were used for latent heat storage and sensible heat storage, respectively. A storage panel was constructed with two openings—an outlet for conditioned air and an inlet for indoor air, then filled with coconut oil or water to create an additional internal thermal mass (ITM) in the room. The storage material was discharged at night in the indoor or outdoor, and stratum air circulation was utilized to provide the conditioned air into the room during diurnal period. Temperature measurements were conducted at five vertical and five horizontal points. The gained results showed that employing ITM heat storage panel in the room reduced peak temperatures and enhanced the thermal environment. Coconut oil ITM provided 0.5 °C lower peak temperature in the occupant zone while greater temperature reductions were observed in the upper zone compared to the reference case. In addition, ITM panel significantly decreased the observed temperature fluctuations throughout a day. This study revealed that ITM-based stratum air circulation can be a profound solution to the existing high energy consumption problem of conventional air conditioners used in the small urban houses under tropical climate.

Abstract In this paper, energy and exergy analyses of the geothermal-based hydrogen production via thermochemical water decomposition using a new, four-step copper–chlorine (Cu–Cl) cycle are conducted, and the respective cycle energy and exergy efficiencies are examined. Also, a parametric study is performed to investigate how each step of the cycle and its overall cycle performance are affected by reference environment temperatures, reaction temperatures, as well as energy efficiency of the geothermal power plant itself. As a result, overall energy and exergy efficiencies of the cycle are found to be 21.67% and 19.35%, respectively, for a reference case.

It is well known that the energy consumption of refrigerating and air-conditioning units is as high as heating systems. It is also clear that cooling loads and availability of solar radiation are approximately in phase. Turkey is located in an ideal position to benefit from solar energy for not only water-heating but also cooling. The use of solar powered absorption refrigerating and air-conditioning systems will save energy, especially in the summer season. The contribution of these systems to the Turkish energy sector and, consequently, to the economy will be considerably high. In this study, a combined water-heating and cooling system based on absorption refrigeration was designed and constructed. The system consists of four flat plate collectors, an evaporator, an absorber, a generator, a condenser, a solution pump and two heat exchangers. Each part was custom designed to provide 4000 kcal/h cooling load. In this system, a mixture of R22 and DMETEG (DiMethyl Ether Tetra Ethylene Glycol) is used as the working fluid. The R22, which has a less damaging effect on the ozone layer compared to other CFCs, was employed as refrigerant. The thermodynamic results of the experimental system were compared with theoretical calculations, and a reasonably good agreement was found. The results show that the present system is efficient and effective.

The energy base of urban settlements requires greater integration of renewable energy sources. This study presents a “hydrogen city” model with two cycles at the district and building levels. The main cycle comprises of hydrogen gas production, hydrogen storage, and a hydrogen distribution network. The electrolysis of water is based on surplus power from wind turbines and third-generation solar photovoltaic thermal panels. Hydrogen is then used in central fuel cells to meet the power demand of urban infrastructure. Hydrogen-enriched biogas that is generated from city wastes supplements this approach. The second cycle is the hydrogen flow in each low-exergy building that is connected to the hydrogen distribution network to supply domestic fuel cells. Make-up water for fuel cells includes treated wastewater to complete an energy-water nexus. The analyses are supported by exergy-based evaluation metrics. The Rational Exergy Management Efficiency of the hydrogen city model can reach 0.80, which is above the value of conventional district energy systems, and represents related advantages for CO2 emission reductions. The option of incorporating low-enthalpy geothermal energy resources at about 80 °C to support the model is evaluated. The hydrogen city model is applied to a new settlement area with an expected 200,000 inhabitants to find that the proposed model can enable a nearly net-zero exergy district status. The results have implications for settlements using hydrogen energy towards meeting net-zero targets.