Experimental investigation on a thermochemical seasonal sorption energy storage battery utilizing MgSO4-H2O.

Thermochemical sorption energy storage (TSES) is the most recent thermal energy storage technology and has been proposed as a promising solution to reduce the mismatch between the energy supply and demand by storing energy for months in form of chemical bonds and restore it in form of synthesis chemical reaction. Compared with sensible/latent thermal energy processes, TSES system has major advantages, including a high energy storage capacity/density and the possibility of long-term energy retention with negligible heat loss. Therefore, a solid-gas thermochemical sorption battery is established and investigated utilizing a composite working pair of MgSO4-H2O based on room temperature expanded graphite (RTEG), treated with sulfuric acid (H2SO4) and ammonium persulfate ((NH4)2S2O8) as a porous additive. The experimental results showed that energy storage density and sorption efficiency increase with the increment of charging temperature or decreasing of discharging temperature at a certain ambient temperature. Under experimental conditions, energy density ranged from 31.7 to 908.8 kJ/kg (corresponding to volume energy density from 11.7 to 335.8 MJ/m3), while sorption energy efficiency ranged from 28.3 to 79.1%. The highest values were obtained when charging, condensation, and discharging temperatures were 95, 20, and 15 °C, respectively. The maximum thermal efficiency was 21.1% at charging/discharging temperature of 95/15 °C with sensible to sorption heat ratio of 3:1.

Comparative study on the performance of solar still equipped with local clay as an energy storage material.

The paucity of freshwater is very dangerous in the coming years. Many coastal countries suffer from a scarcity of freshwater. Solar desalination is the cheapest way to produce freshwater from any type of non-drinkable water (brackish water and seawater). In this work, single-slope single-basin solar still for seawater desalination was examined under Upper Egyptian weather conditions of Qena City (latitude 26.16°, longitude 32.71°). The main goal of the work is to compare the performance of conventional solar still, solar still supported with PCM, and solar still supported with local clay material to augment the solar still yield during both daytime and nighttime periods of operation. The results demonstrated that the total production of desalinated water from the simple conventional solar still, the solar still with PCM, and the solar still with local clay reached about 3885, 4704, and 5388.6 ml/m2, respectively. Moreover, compared to the conventional solar still, the yield was increased by about 21% when using the PCM, and about 38.7% when using the local clay material. Furthermore, it can be observed that the daytime productivity in the case of solar still supported with local clay was higher than that for the solar still supported with PCM, while the nighttime productivity was higher in the case of solar still supported with PCM compared with solar still supported with local clay. Moreover, the average daily efficiency of conventional solar still, solar still with PCM, and solar still with local clay reached about 34, 41.2, and 47%, respectively. Therefore, it is recommended to use the solar still with local clay for seawater desalination in such arid and hot climate of Qena City.

Comparison of different adsorption pairs based on zeotropic and azeotropic mixture refrigerants for solar adsorption ice maker.

One of the important ways to the efficiently use of low-grade thermal energy is the adsorption refrigeration technology. However, it has some drawbacks such as low specific cooling power and coefficient of performance, especially under using the conventional adsorption pairs. Therefore, new adsorption pairs are tested in solar adsorption ice-maker and compared with other conventional pairs data from open literature to find the tendency of improving the solar adsorption ice-maker performance. The experimental test rig has been built in Upper Egypt in Qena City. Four different new adsorption pairs of granular activated carbon/R-410A, granular activated carbon/R-511A, Maxsorb III/R-410A, and Maxsorb III/R-511A are used. It is demonstrated that Maxsorb III/R-511A pair based solar adsorption ice-maker produced the highest values for specific cooling power, coefficient of performance, and ice production per 1 kg of adsorbent of approximately 226.7 W/kgads, 0.197, and 1.96 kg/kgads, respectively. While granular activated carbon/R-410A based solar adsorption ice-maker produced the lowest values of ice production per 1 kg of adsorbent and coefficient of performance of 1.38 kg/kgads and 0.104, respectively. Moreover, it can be concluded that the tested pairs are feasible to be used in solar adsorption ice-maker systems, especially in such hot climate of Upper Egypt for food and vaccine preservation and storage.

Performance enhancement of single-slope solar still using phase change materials.

Freshwater scarcity appears clearly in coastal areas of Egypt despite the existence of a large amount of seawater around. Solar still is the cheapest and oldest way to desalinate seawater and brackish water. In the proposed study, single-slope solar still was examined in the climatic conditions of Qena, Egypt (Latitude: 26.16°, longitude: 32.71°). The purpose of the study was to analyze the energy storage behavior inside the phase change materials and to enhance the solar still productivity during both daytime and nighttime operation. The performance of the proposed solar still was tested under the use of phase change material (RT42PCM) with different quantities of 2, 4, and 6 kg in weight, which was placed inside the basin area. Furthermore, the optimum phase change material quantity was compared with simple conventional solar still without phase change material. The results showed that the productivity of the proposed solar still in the case of using 4-kg phase change material was higher than that for using 2-kg phase change material and 6-kg phase change material by about 18.6 and 27.7%, respectively. Moreover, the average daily efficiency is 68, 57.2, and 53.6%, respectively. The use of 4-kg phase change material in the basin caused an enhancement in the proposed solar still productivity by about 29.7% and the average daily efficiency was 66.7 and 51.5%, respectively, in comparison with simple solar still without phase change material. It was additionally seen that in the case of using phase change material, more yield was gotten over during the nighttime and the average basin water temperature was increased due to its high ability to store thermal energy inside. Furthermore, the produced freshwater could be used in different life applications, because of its appropriate ranges of total dissolved solids, pH, hardness, and water clarity.