Results 1 - 10 of 370
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[en] This report details the results of a research conducted in 1998 and 1999 and outlines a marketing deployment plan designed for businesses interested in marketing solar water heaters in the new home industry
[en] The results of numerical research on the determination of the temperature value of the internal surface of the heat-removing channel (HRC) walls of the light-absorbing heat-exchange panels (LAHPs) with the tubeon- sheet and thin-parallelepiped form of flat-plate solar water-heating collectors (FPSWHCs) are presented. The research method is based on compilation of the system of the balance equations for the light-absorbing plate (LAP) and HRCs of the LAHPs of the studied types and their designs with respect to the desired parameter. A practical example of calculation of the determination of the temperature value of the internal surface of the HRC wall of the tube-on-sheet LAHP, where the results of experimental research on the determination of the specific thermal efficiency of the mean-quality FPSWHC in full-scale terms, as well as laboratory and numerical research on determination of the optical and thermotechnical indicators of the copper tube-on-sheet LAHP.
[en] The technology of solar water heating is simple and can be used for pre-heating of water entering a boiler. In this paper the economics of solar pre-heating of water was calculated. The calculations were based on the performance and cost of a locally-made flat plate collector, and the performance and fuel consumption of a boiler in a textile mill. The results showed that a collector area of about 800 meter square with initial cost of about LS 5,000,000, could save annually about 130 tons of furnace oil. ( Author )
[en] Seasonal solar energy yields for domestic hot water production are calculated across Estonia, based on the monthly distribution of temperatures and yearly distribution of global solar irradiation. A simplified pulse-mode simulation model was used to describe the processes in a stratified solar system. (author)
[en] Solar plants are increasingly used not only for hot tap water heating but also for the assistance of space heating. These plants produce much more energy in summer than needed, which often results in stagnation. Because of stagnation-temperatures of todays selective collectors up to 200 deg. C, the collector fluid evaporates. In several plants a high noise level and a vibration of the plant during this evaporation phase is reported. This is due to the occurrence of water hammers in the system, when liquid collector fluid passes areas where the fluid was already evaporated and superheated. The remaining vapor bubbles deflate rapidly and the liquid phases collide with high velocity, which results in a rapid pressure increase. This paper describes the theory of condensate-induced water hammers and conditions of solar plants, under which this can happen. A simulation model for the evaporation phase of the collector is presented to give a deeper understanding about the influences of solar radiation, the size of the tubing, and the size of the expansion device on the process of the evaporation. Three hydraulic layouts of the collector area are discussed for there possibilities producing water hammers. (au)
[en] A 'sunflower' system able to concentrate light from the Sun, storing it in a black body for energy application either for household or industrial use, is developed by means of basic physics concepts. A particular application to household water heating, called Planckon, is presented. Given its simplicity, the system can be realized and tested in any high-school or college laboratory, in order to stress the link existing between basic physics concepts and renewable energy resources
[en] Highlights: ► Simultaneous charging and discharging of an oil storage tank is investigated. ► Three different cases are studied and water is boiled in all cases. ► Thermal stratification is evident for all the three cases. ► Sufficient amount of energy is stored in the storage tank to cook low heat foods. - Abstract: An experimental setup for simultaneous charging and discharging experiments to be performed on an oil storage tank is presented. The experimental setup enables thermal energy to be stored in the storage tank as well as water to be heated up for a cooking application in a simultaneous charging and discharge cycle. Results of three different simultaneous charging and discharging cases are presented. The three different cases of simultaneous charging and discharging are; (i) an initially unstratified storage tank, (ii) an initially stratified storage tank, and (iii) an initially unstratified storage tank at the top and stratified at the bottom. The three different cases of simultaneous charging and discharging indicate that water can be boiled within 2 h of the charging/discharging cycle and a sufficient amount of energy can be stored in the storage tank. It is suggested that foods which take longer cooking times can be cooked with the boiling water. The energy stored can be used to heat up or cook foods that require lower cooking temperatures. Thermal stratification in the storage is evident for all of the three cases.
[en] We analysed the heating curve of water which is described in textbooks. An experiment combined with some simple heat transfer calculations is discussed. The theoretical behaviour can be altered by changing the conditions under which the experiment is modelled. By identifying and controlling the different parameters involved during the heating process, we calculated that radiation, convection and evaporation are the main processes in the heating curve
[en] The Caldes de Boí geothermal waters show important differences in pH (6.5–9.6) and temperature (15.9ºC–52ºC) despite they have a common origin and a very simple circuit at depth (4km below the recharge area level). Thes differences are the result of secondary processes such as conductive cooling, mixing with colder shallower waters, and input of external CO2, which affect each spring to a different extent in the terminal part of the thermal circuit. In this paper, the secondary processes that control the geochemical evolution of this system have been addressed using a geochemical dataset spanning over 20 years and combining different approaches: classical geochemical calculations and geochemical modelling. Mixing between a cold and a thermal end-member, cooling and CO2 exchange are the processes affecting the spring waters with different intensity over time. These differences in the intensity of the secondary processes could be controlled by the effect of climate and indirectly by the geomorphological and hydrogeological setting of the different springs. Infiltration recharging the shallow aquifer is dominant during the rainy seasons and the extent of the mixing process is greater, at least in some springs.Moreover, significant rainfall can produce a decrease in the ground temperature favouring the conductive cooling. Finally, the geomorphological settings of the springs determine the thickness and the hydraulic properties of the saturated layer below them and, therefore, they affect the extent of the mixing process between the deep thermal waters and the shallower cold waters. The understanding of the compositional changes in the thermal waters and the main factors that could affect them is a key issue to plan the future management of the geothermal resources of the Caldes de Boí system. Here, we propose to use a simple methodology to assess the effect of those factors, which could affect the quality of the thermal waters for balneotherapy at long-term scale. Furthermore, the methodology used in this study can be applied to other geothermal systems.