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[en] This paper deals with a numerical and experimental investigation of a daily solar storage system conceived and built in Laboratoire de Maitrise des Technologies de l Energie (LMTE, Borj Cedria). This system consists mainly of the storage unit connected to a solar collector unit. The storage unit consists of a wooden case with dimension of 5 m3 (5 m x 1m x 1m) filed with fin sand. Inside the wooden case was buried a network of a polypropylene capillary heat exchanger with an aperture area equal to 5 m2. The heat collection unit consisted of 5 m2 of south-facing solar collector mounted at a 37 degree tilt angle. In order to evaluate the system efficiency during the charging period (during the day) and discharging period (during the night) an energy and exergy analyses were applied. Outdoor experiments were also carried out under varied environmental conditions for several consecutive days. Results showed that during the charging period, the average daily rates of thermal energy and exergy stored in the heat storage unit were 400 and 2.6 W, respectively. It was found that the net energy and exergy efficiencies in the charging period were 32 pour cent and 22 pour cent, respectively. During the discharging period, the average daily rates of the thermal energy and exergy recovered from the heat storage unit were 2 kW and 2.5 kW, respectively. The recovered heat from the heat storage unit was used for the air-heating of a tested room (4 m x 3 m x 3 m). The results showed that 30 pour cent of the total heating requirement of the tested room was obtained from the heat storage system during the whole night in cold seasons
[en] In order to increase energy security, production of renewable energies has been highly promoted by governments around the world in recent years. The typical base of various policy instruments used for this purpose is gross energy output of renewable energy. However, we show that basing policy instruments on gross energy output will result in problems associated with energy waste, economic inefficiency, and negative environmental effects. We recommend using net energy output as the base to apply price or quantity measures because it is net energy output, not gross energy output, which contributes to energy security. The promotion of gross energy output does not guarantee a positive amount of net energy output. By basing policy instruments on net energy output, energy security can be enhanced and the above mentioned problems can be avoided.
[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] 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] Nature has been providing us energy from the beginning of the world. However human has hardly used it wisely. Solar energy is a kind of renewable energy from the nature. This study has been carried out to study the use of solar energy as it is harnessed in the form of thermal energy. Solar energy is one of the most promising energy resources such as hydrogen, biomass, wind and geothermal energy, because it is clean and inexhaustible. Space heating in buildings can be provided from solar energy by systems that are similar in many respects to water heater systems. By tapping into solar energy, we can not only solve the problem of energy shortage, but also can protect the environment and benefit the human beings. There are currently two types of evacuated tube; a single glass tube and a double glass tube. The former consists of a single glass tube which contains a flat or curved aluminium plate attached to a copper heat pipe or water flow pipe. The latter consists of rows of parallel transparent glass tubes, each of which contains an absorber tube. Evacuated tube collectors introduced above, however, pose some problems as they break rather easily under mechanical stresses. This paper introduces some preliminary results in design and fabrication of a non-glass solar vacuum tube collector in which the thermosyphon(heat pipe)made of copper is used as a heat transfer device. A series of tests have been performed to assess the ability of a non-glass solar vacuum tube collector. The series of experiments are as follows: 1)Vacuum level inside a vacuum tube. 2)Effects of the air remaining inside a vacuum tube on the temperature on the absorber plate. 3)Comparison of a non-glass vacuum solar collector with a single glass evacuated tube(SEIDO 5). Different vacuum levels inside non-glass vacuum tubes were applied to check any leakage or unexpected physical or chemical developments with time. The vacuum level changed from 10-2torr to 5torr in 5 days due to air infiltration from the ambient and gas emissions from the materials they were made of. The effect of vacuum levels inside a vacuum tube on the absorber plate were investigated in different conditions. Due to less heat losses to the ambient, the non-glass vacuum tube at vacuum level 10-2 torr kept more heat at higher temperatures compared to the non-glass vacuum tube collectors whose vacuum levels were at 5 torr. However, the temperature was not linearly proportional to the vacuum level. Two types of solar collectors were used to investigate the ability of non-glass solar vacuum tube: one single glass evacuated tube and one non-glass vacuum tubes(10-2torr). The efficiency of a non-glass vacuum tube with 10-2torr was different from that of a single glass evacuated tube in which vacuum level is 10-4∼10-5torr due to the transmittance of ZnO. Unlike glass evacuated tubes, non-glass solar vacuum tubes generally require some measures to prevent air infiltration through invisible pores of the tube wall and gas emission from the materials. If the problems related with vacuum inside a tube are solved, the non-glass vacuum collector will work more efficiently
[en] The adoption of an innovation is partly dependent on the consumers' perception of the product attributes, starting with the 'relative advantage' a product may have over another existing product, and also include issues of compatibility, complexity, observability and trialability. Using diffusion of innovations theory as a conceptual framework, this paper describes a case study that investigated the innovation adoption process that a group of identified potential adopters of domestic solar thermal systems stated they would follow. Data was generated from the results of a postal survey to a group of 43 defined innovators and a group of 350 assumed 'early majority', pragmatic consumers. The survey results showed that while the pragmatic customers did follow the process as theorised in diffusion theory, the innovators disregarded the observability attributes of the innovation and went ahead with implementation without having seen the products beforehand. The group of innovators was also split in their opinion that 'complexity' may be a limiting factor. There were differences in the pragmatic group between certain demographic sub groups. Conclusions are drawn on how the findings may impact marketing activities
[en] In today's electricity generation system, different resources make different contributions to the electricity grid. This fact sheet illustrates the roles of distributed and centralized renewable energy technologies, particularly solar power, and how they will contribute to the future electricity system. The advantages of a diversified mix of power generation systems are highlighted.
[en] A novel nuclear astrophysics facility, CLAIRE (Center for Low Energy Astrophysics and Interdisciplinary REsearch), is being designed at Lawrence Berkeley National Laboratory to address the need for precise fusion cross section measurements at near-solar energies (∼20 keV). At these low energies, fusion cross sections decrease exponentially with energy and are expected to approach femtobarn levels or less. In order to measure such small cross sections, the CLAIRE facility will incorporate a versatile accelerator capable of transporting high current (>100 mA), low energy (50-300 keV) ion beams with a tight focus (<1 cm) to a cooled, dense gas-jet target. The conceptual design for this accelerator is discussed, and simulations of both beam extraction and transport are presented
[en] About 20 years ago, we decided to make our house. Being working on the utilization of solar energy and with the objective of saving maximum conventional fuel and some family budget, we dicided to make use of maximum this free and clean fuel. After buying the land with proper orientation, we installed different cheap devices and left the proper provision for another devices to installed in future. At present we solar energy mainly for cooking, water heating for bath and dish washing, drying clothes/fruits/vegetables, purification (pasteurization) of water. In addition. we also use solar cells for some electrical devices like solar radio, solar lamp for emergency, charging batteries and mobile phone etc. For our family of five persons, having 3 coloured TV, 2 computers using many hours of Internet, without any use of fuel other than electricity and sun, our electricity consumption is of the order of 270 (dry/summer)-350 (wet/rainy) kWh/month, depending on the season (US$16-21/month). This is roughly 40-50% of the electricity consumed by my other colleagues who do not use solar energy. With this saving, the initial cost of solar devices (US$1200-1400) is already recovered. In this presentation, construction and results of working of these solar thermal, electrical devices and other energy saving means at our house are mentioned.(Author)