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[en] An investigation of estimating clear sky insolation has been conducted. Some discrepancies have been found between the conventional method of estimation and the data. It has been noticed that the conventional method underestimates the insolation. A simpler, more elegant and more accurate 'universal' relationship has been derived for estimating the annual mean daily clear sky insolation as a function of the latitude and altitude of a given location. As part of this derivation, two simple and accurate correlations have been obtained, i.e. for extraterrestrial insolation and for atmospheric attenuation
[en] Geothermal energy is a varied discipline that challenges many separate scientific domains. Geological constraints limit access to thermal reservoirs, strength of materials limits the ability to drill into hot strata, mechanical constraints limit the extraction of energy from fluid at a small temperature difference and environmental concerns restrict the fluids production because of the gases released. These problems are all being investigated, and progress is constant and hopeful. The uses of geothermal energy are varied. They range from direct use in space heating to using geothermal steam to power turbines. Ground source heat pumps are a popular alternative to conventional air conditioning systems, and water source heat pumps are another proven alternative. Many other applications are on the horizon, including absorption chillers able to operate at a small temperature difference, higher tonnage ground source equipment and new approaches to hot dry rock power production
[en] Highlights: • A solar thermoelectric with micro-channel heat pipe system was presented. • Mathematical model of the system was built. • Experiment and the simulation were compared to verify the model. • Performance of the system with different factors was analyzed. - Abstract: Micro-channel heat pipe can convert the low heat flux to the high heat flux by changing the ratio of the evaporator area to the condenser area and has a higher heat transfer performance than the common heat pipe. Combining the solar concentrating thermoelectric generation with micro-channel heat pipe can save the quantity of thermoelectric generation and reduce the cost significantly. In this paper, a solar concentrating thermoelectric generator using the micro-channel heat pipe array was designed, and the mathematical model was built. Furthermore, the comparison of the experiment and the simulation between the solar concentrating thermoelectric generator using the micro-channel heat pipe array and the thermoelectric generations in series was made. In addition, the performance on the different areas of selective absorbing coating, different concentration ratios, different ambient temperatures, different wind speed all were analyzed. The outcomes showed the overall performance of the solar concentrating thermoelectric generator using the micro-channel heat pipe array system.
[en] Highlights: • A technical solution to the power supply of wireless sensor networks is presented. • The low voltage produced by TEG is boosted from less than 1 V to more than 4 V. • An output current and voltage of TEG device is acquired as 21.47 mA and 221 mV. • The device successfully provides output power 4.7 mW in no electricity conditions. • The thermo-economic value of TEG device is demonstrated. - Abstract: Motivated by the limited power supply of wireless sensors used to monitor the natural environment, for example, in forests, this study presents a technical solution by recycling solar irradiation heat using thermoelectric generators. Based on solar irradiation and the earth’s surface-air temperature difference, a new type of thermoelectric power generation device has been devised, the distinguishing features of which include the application of an all-glass heat-tube-type vacuum solar heat collection pipe to absorb and transfer solar energy without a water medium and the use of a thin heat dissipation tube to cool the earth surface air temperature. The effects of key parameters such as solar illumination, air temperature, load resistance, the proportional coefficient, output power and power generation efficiency for thermoelectric energy conversion are analyzed. The results of realistic outdoor experiments show that under a state of regular illumination at 3.75 × 10"4 lx, using one TEG module, the thermoelectric device is able to boost the voltage obtained from the natural solar irradiation from 221 mV to 4.41 V, with an output power of 4.7 mW. This means that the electrical energy generated can provide the power supply for low power consumption components, such as low power wireless sensors, ZigBee modules and other low power loads
[en] A district space heating and cooling system using geothermal energy from bearing piles was designed in Shanghai and will be installed in two years before 2010. This paper describes the pile-foundation heat exchangers applied in an energy pile system for an actual architectural complex in Shanghai, 30% of whose cooling/heating load was designed to be provided by a ground-source heat pump (GSHP) system using the energy piles. In situ performance tests of heat transfer are carried out to figure out the most efficient type of energy pile and to specify the design of energy pile system. Numerical investigation is also performed to confirm the test results and to demonstrate the medium temperature variations along the pipes. The averaged heat resistance and heat injection rate of different types of energy piles are calculated from the test and numerical results. The effect of pile type, medium flow rate and inlet temperature on thermal performance is separately discussed. From the viewpoint of energy efficiency and adjustability, the W-shaped underground heat exchanger with moderate medium flow rate is finally adopted for the energy pile system
[en] The development of microsatellites requires the development of engines to modify their orbit. It is natural to use solar energy to drive such engines. For an unlimited energy source the optimal thruster must use a minimal amount of expendable material to minimize launch costs. This requires the ejected material to have the maximal velocity and, hence, the ejected atoms must be as light as possible and be ejected by as high an energy density source as possible. Such a propulsion can be induced by pulses from an ultra-short laser. The ultra-short laser provides the high-energy concentration and high-ejected velocity. We suggest a microthruster system comprised of an inflatable solar concentrator, a solar panel, and a diode-pumped fiber laser. We will describe the system design and give weight estimates.
[en] Province Balochistan is largest province of Pakistan with smallest density of population with little or no development. In Balochistan bulk is rural located and devoid of lives basic ingredients. In remote rural areas of Balochistan because of high cost and problems associated with grid extension or diesel power generation, solar electricity is viable alternate. Energy generated from the sun is world's most abundant and in-exhaustible source of energy PV cells sun light is converted directly in to electricity called solar PV energy. Solar energy through photovoltaic cells can be tapped to supply electricity to remote rural areas of Balochistan. In this paper author has examined the problems in more detail, showing by simple calculation of cost economics that solar PV systems are viable. (author)
[en] Highlights: • A new method for design of segmented TEG is proposed. • Optimal length ratios for output power and efficiency are different. • Material properties, geometry and heat transfer all need to be considered. • This method is approved to be accurate and time-efficient. - Abstract: A comprehensive method for indicating the length ratio of segmented thermoelectric generator (TEG) is proposed to increase the output power and thermoelectric conversion efficiency. It is found that for a segmented TEG, there is an optimal length ratio corresponding to the highest maximum output power or thermoelectric conversion efficiency, which is not only dependent on the material properties but also the heat transfer conditions and geometry structure. The optimal length ratios corresponding to the output power and thermoelectric conversion efficiency are different. This method is also validated, and the error is within a reasonable range, indicating that this method can be used accurately and time-efficiently for the design of segmented TEGs.
[en] Highlights: • Thermodynamic analysis is presented for a LAES system combined with packed bed units. • The LAES system round-trip efficiency is in the range 50–62%. • Cold box inlet temperature and discharge pressure have significant influence on system performance. • LAES system has smaller air storage volume and higher ASED compared with A-CAES system. - Abstract: Energy storage is a key technology required to manage intermittent or variable renewable energy, such as wind or solar energy. In this paper a concept of an energy storage based on liquid air energy storage (LAES) with packed bed units is introduced. First, the system thermodynamic performance of a typical cycle is investigated and temperature distribution in cold boxes is discussed. Then, the effects of inlet temperature of cold boxes, charge and discharge pressures on thermal behaviors of LAES system are analyzed, as well as the system round-trip efficiency. Finally, an overall comparison between this LAES system and an adiabatic compressed air energy storage (A-CAES) system is conducted. The system could achieve a round-trip efficiency in the range 50–62% depending on the values of process conditions. The system round-trip efficiency decreases with the increase of cold box inlet temperature, and increases with the rise of charge and discharge pressures. Although the round-trip efficiency of the present LAES system is a bit lower than the A-CAES system, however, the air storage volume decreases and the air storage energy density (ASED) increases remarkably for the same operational conditions. The main conclusions draw from this work is beneficial for future LAES development in particular the combination with the packed bed units and the fit with the requirements for large-scale energy storage.
[en] Here we present the different aspects of the EUROSUNMED project. The scientific targets of EUROSUNMED are the development of new technologies in three energy field areas, namely photovoltaics (PV), concentrated solar power (CSP) and grid integration (GI), in strong collaboration with research institutes, universities and SMSs from Europe in the north side of the Mediterranean sea and from Morocco and Egypt from the south of the sea. the focus in PV will be on thin film (Si, CZTS) based solar cells and modules while the goal in CSP field is to design and test new heliostats as well as novel solutions for energy storage compatible with these technologies. The project aims at producing components that will be tested under specific conditions of MPC (hot climate, absence of water, etc.). Such investigations are complemented with studies on grid integration of energy sources from PV and CSP in Morocco and Egypt context. Additionally, the consortium envisages training PhD students and post-docs in these interdisciplinary fields (chemistry, physics, materials science) in a close and fruitful collaboration between academic institutions and industry from EU and MPCs. The consortium is well placed around leading academic groups in materials science and engineering devices and equipments for the development of PV and CSP, and also in the promotion of the renewable energies in general. Moreover, technology transfer and research infrastructure development in the targeted areas will be provided. Disseminating the results of the projects will be done through the organization of summer schools and stakeholders involved in the 3 selected energy area and beyond. Another outreach of the project will be the proposal for a roadmap on the technological aspects (research, industry, implementation) of the PV, CSP and grid area as well as on the best practice for the continuation of strong collaboration between the EU and MPCS partners and beyond for mutual interest. (author)