Comparison between double slope solar still and fourfold slope solar still: energy, exergy, exergoeconomic, and enviroeconomic evaluation

This paper proposes a single basin fourfold slope solar still, which includes a fourfold slope glass cover plate used for solar heat collection and steam condensation. In order to show the efficiency of fourfold slope solar still, comparative experiments are conducted under the winter climate conditions in Hangzhou for testing the operational performance of double slope type solar still (DOSS) and fourfold slope still (FOSS), so as to make a comparative analysis between them. Results show that the productivity of fourfold slope still is 19.51% higher than that of double slope still, and fourfold slope solar still enhances the average hourly energy efficiency by 31.11%. According to the energy method, the energy payback time values of fourfold slope solar still and double slope solar still are 64.88 months and 75.42 months respectively. According to the environmental parameter method, FOSS and DOSS reduce 5.47 tons and 4.58 tons of CO2 respectively. The corresponding values based on the exergy environment parameters are 0.21 and 0.18 tons of CO2, respectively. The fourfold slope solar still has more obvious emission reduction function than the double slope solar still. The cost of distilled water of fourfold slope solar still is 0.28 RMB/kg, and the cost of double slope solar still is 0.30 RMB/kg. In addition, the environmental and economic parameters of fourfold slope still and double slope still are 79.29$ (561.37RMB) and 66.35$ (469.76RMB), respectively. While, the corresponding values based on the exergoenvironmental parameter are 3.05$ (21.59RMB) and 2.56$ (18.12RMB), respectively. From the analysis of exergoeconomic and exergoenvironmental parameters, fourfold slope single basin solar still appears to be more effective.

Experimental study of a solar water treatment device with dome structure cover in winter: performance evaluation and comparative analysis

In this paper, a dome slope single basin solar still for water treatment and desalination is presented. This new solar still device is based on installing a dome slope cover on the walls of the solar still. The main objective of such still is to concentrate more sunrays at the still's bottom basin, through the increased area of dome glass cover. Experiments are conducted under the climate conditions in Hangzhou city, China, for testing the operational performance of dome slope type solar still and the fourfold slope still, so as to make a comparative analysis between them. Assessment of the dome slope still's feasibility is performed based on energy, exergy, exergoeconomic, and enviroeconomic methodologies, as well as energy payback time. Results show that the productivity of dome slope still is 36% higher than that of fourfold slope still, and dome slope solar still enhances the average hourly energy efficiency by 34%. Due to the higher energy and exergy outputs of dome slope solar still throughout its lifetime, the novel solar still proposed in this study mitigates more CO2 compared to the fourfold slope still. Overall, incorporation dome slope cover with the still is found promising in terms of freshwater yield, cost, and energy payback time compared to conventional one. The dome slope single basin solar still appears to be effective from exergoeconomic, exergoenvironmental parameters analysis.

Life cycle energy use and environmental implications of high-performance perovskite tandem solar cells

A promising route to widespread deployment of photovoltaics is to harness inexpensive, highly-efficient tandems. We perform holistic life cycle assessments on the energy payback time, carbon footprint, and environmental impact scores for perovskite-silicon and perovskite-perovskite tandems benchmarked against state-of-the-art commercial silicon cells. The scalability of processing steps and materials in the manufacture and operation of tandems is considered. The resulting energy payback time and greenhouse gas emission factor of the all-perovskite tandem configuration are 0.35 years and 10.7 g CO2-eq/kWh, respectively, compared to 1.52 years and 24.6 g CO2-eq/kWh for the silicon benchmark. Prolonging the lifetime provides a strong technological lever for reducing the carbon footprint such that the perovskite-silicon tandem can outcompete the current benchmark on energy and environmental performance. Perovskite-perovskite tandems with flexible and lightweight form factors further improve the energy and environmental performance by around 6% and thus enhance the potential for large-scale, sustainable deployment.

Energy Demand, Efficiency Measures and Embodied Energy in the Italian Residential Sector

This paper investigates a strategy for energy saving in the Italian residential sector that includes in the assessment the embodied energy related to the efficiency measures. Simulations are run in three main cities (Milan, Rome and Naples) covering different climate zones. The purpose is, firstly, to estimate the baseline of the buildings energy consumption, secondly, to simulate the implementation of realistic retrofit solutions and, finally, to assess the retrofitting’ embodied energy and its energy payback time. The energy payback is based on the comparison between the net saved operational site energy and the embodied energy of the selected measures. By running the simulations, it is possible to estimate the maximum potential for energy savings and realistic estimation of achievable results in short-medium period. Results show the energy efficiency measures more convenient in terms of energy payback depending on the climate zone. For Naples, a focus on façade insulation has been held and the results defined the optimal material thickness in terms of embodied energy and net saved operational site energy in a life cycle of 15 years.