Humidity Effect on the Simulation Accuracy of Solar Vortex Engine Performance

In this study, a validated computational simulation is presented to investigate the effect of humidity on the performance prediction of the solar vortex engine system. Data from an experimental model are used to validate the CFD simulation. Three humidity cases are considered: dry air, 40% and 80% humid air. An expansion process with heat addition is taking place inside the vortex generator. When the vortex field continues outside the system, a compression process with heat rejection occurs, eventually bringing the air vortex to be thermal and mechanical equilibrium with the surrounding atmosphere. The change in total energy and the heat transfer rate for both processes, inside the vortex generator and outside the vortex generator, increase with increased humidity in the working fluid. The humidity increases the energy required by the system to generate and maintain the air vortex. Compared to the dry air, the pressure drop at the center of the vortex field decreases by (2-5%) and (4-9%) for the 40% and 80% humid air, respectively. Reduced pressure drop decreases the stability of the air vortex when it is in contact with the atmosphere. The intensity of the air vortex is not affected by the increase in humidity.

A Provisional Model for the Optimal Management of a Charging Station Assisted by Photovoltaic Panels for Plug-In Electric Vehicles

There is a strongly increasing diffusion of Electric Vehicles (EV) and Plug-in Hybrid Electric Vehicles (PHEV), in order to reduce air pollution in urban environment and to mitigate the global warming issues. Anyway, the achievement of this latter goal strictly depends on the source of primary energy used to generate electrical energy. In the paper, a model for the optimal design and operation of a charging station for EV and PHEV assisted by a PhotoVoltaic (PV) plant is presented. A provisional model for the estimation of the incoming insolation, based on cloudiness prevision, is integrated with a nonlinear constrained optimization algorithm, in order to satisfy the load while minimizing the recourse to electrical grid for battery storage charging. Simulations on different locations and charging loads for various size of PV plant and battery capacity are presented, and the benefits in terms of CO2 reduction discussed.

History of Solar Car Technology and its Future Especially in Power Electronics

This paper describes the history and evolution of technologies related to the whole electrical system of solar car [1]. The components are the solar cell, maximum power point tracker, boost converter, motor& Inverter and battery. In a solar car, it is difficult to arrange the solar cells on a flat vehicle surface, and solar cells with different incident angles and temperature is different in each cell. This is a problem when many solar cells with different characteristics are connected in series, and the improvement method will be described in detail. Next, we will explain the development of a boost converter using a GaN power device that can improve the overall running efficiency. We will also discuss the technological advances in motors & inverters and batteries over the last 30 years. The evolution of solar cars is largely due to the evolution of semiconductors, including solar cells, and material technologies, but at the same time, we will explain examples of these technologies being first demonstrated in solar car race and then socially implemented

History of Solar Car Technology and its Future Especially in Power Electronics

This paper describes the history and evolution of technologies related to the whole electrical system of solar car [1]. The components are the solar cell, maximum power point tracker, boost converter, motor& Inverter and battery. In a solar car, it is difficult to arrange the solar cells on a flat vehicle surface, and solar cells with different incident angles and temperature is different in each cell. This is a problem when many solar cells with different characteristics are connected in series, and the improvement method will be described in detail. Next, we will explain the development of a boost converter using a GaN power device that can improve the overall running efficiency. We will also discuss the technological advances in motors & inverters and batteries over the last 30 years. The evolution of solar cars is largely due to the evolution of semiconductors, including solar cells, and material technologies, but at the same time, we will explain examples of these technologies being first demonstrated in solar car race and then socially implemented

Decarbonization of Summer Cooling Energy Demands of Buildings Employing Absorption Systems in the Framework of Climate Change in Italy

Temperatures in the Mediterranean area have gradually risen in the last decades due to climate change, especially in the Italian Peninsula. This phenomenon has increased the cooling needs to ensure thermal comfort in buildings and, consequently, the use of refrigeration machines. Summer air conditioning is carried out mainly using compression machines powered by electricity supplied by the national network. All this contributes to the emission of climate-changing gases. To avoid this disadvantageous chain, compression machines could be replaced by absorption cooling systems powered by solar energy. The energy needs of the buildings in a time are directly proportional to the sum of positive differences between the outdoor air temperature and the indoor set point of the systems (equal to 26°C). The annual sum of hourly temperature differences defined above can be computed for each grid cell thanks to a numerical weather prediction model, namely the Weather Research and Forecasting model, that simulates the hourly temperatures on high-resolution computation grids and over fairly large extents. Maps of cooling consumption for buildings are thus produced. Choosing absorption solar energy-powered systems instead of vapor compression refrigeration systems leads to a drop in electrical energy consumption and therefore in emissions of greenhouse gases. In this work, different hypothetical scenarios of penetration of this technology have been considered. And the subsequent consumption of electricity withdrawn from the national grid has been estimated together with the reduction of greenhouse gas emissions.

A Passive Solar Air-House Conditioning System Integrated in Tunisian households

In Tunisia, the buildings’ space heating sector represents a major part of the total energy consumption budget. These issues have been increasingly prominent concerns since the energy crisis. Hence, interests have been growing to adopt renewable energies as viable sources of energy that offer a wide range of exceptional benefits with an important degree of promise, especially in the buildings sector. However, the management of renewable energy sources for space air heating/cooling is usually not economically feasible compared with the traditional carriers. In this chapter, we present a passive energy system, called air-conditioning cupboard which exploits renewable energies (hot water supplied from solar collector [40-50°C] and cold groundwater (19°C)) as thermal sources, is conceived and tested in our laboratory (Laboratory of Thermal Procedure, LPT Tunisia). To evaluate the air-conditioning cupboard efficiency indoor experiments were carried out under varied Tunisian environmental conditions for several days. Results show that the air-heating system has good thermal effectiveness (80 %). It permits to the maintenance of the temperature inside the experimented room at the range of [24-27°C] during the cold months and [20-23°C] during hot months. A theoretical model is employed for the sizing of the air-conditioning cupboard to obtain the required temperature values. This model allows also the determination of the air-cupboard conditioning thermal performances.

Experimental Investigation and Theoretical Analysis on the Performance of Tube-Sheet Photovoltaic Thermal (PV/T) Collectors

The PV/T collectors realize the simultaneous output of electricity and thermal energy, which are more efficient than the separated photovoltaic (PV) or solar thermal collectors. In this paper, the electricity generation and thermal collection performances of tube-sheet PV/T collector are studied. The main research contents are as follows: an experimental test system of PV/T collector was built to test the electricity generation and thermal collection performances of tube-sheet PV/T at an inlet water temperature of 30°C. Moreover, the flow resistance test was carried out. In addition, the theoretical heat transfer model was established, and the thermal performance was calculated by theoretical analysis. The experimental data showed that the daily average temperature difference between the PV panel and the inlet water temperature was about 22.5°C. The daily average electrical efficiency was about 9.25%, and the daily average thermal efficiency was about 28.67%. The theoretical analysis of the tube-sheet PV/T model was carried out, and the calculated results were close to the experimental results. The main reason for the large temperature difference between the PV panel and water temperature was that the combined thermal resistance between the PV panel and the absorber plate was large, and reducing the combined thermal resistance could reduce the temperature of the PV panel. The effects of solar irradiance, ambient temperature and spacing of row tubes on the performance of thermal collection were analyzed to optimize the PV/T performance.

Design and Evaluation of a Concentrated Solar-Powered Thermal-Pasteurization System

A device has been designed, constructed, and tested for heating fluids using solar energy. The device heats water to levels to kill pathogens by a parabolic reflecting surface that concentrates solar energy along an axis. Among the components that increase the thermal performance of the system is a thermally actuated valve, which controls the temperature and the thermal exposure duration of the fluid to cause deactivation of targeted pathogens. Also, a novel fluid-to-fluid heat exchanger arranged in counter flow is used. Experiments were performed with a water solution containing non-pathogenic Escherichia coli K-12 MG1655 (E. coli) bacteria. The results showed that the system is capable of pasteurization to levels where no living pathogens were detected in the heated fluid. The experiments were carried out over a wide range of temperatures and exposure durations to test the device and the underlying mathematical model. E. coli log reductions greater than 1 were achieved in all cases and it is shown that arbitrary values of reduction can be achieved with appropriate temperature/time settings.