Abstract-Low voltage distribution feeders are designed for unidirectional energy supply from transformer to consumer. However, the implementation of small-scale PV production units on local utilities may result in bidirectional energy flows. The simultaneous power injection at sunny moments may cause a serious voltage rise along the feeder. These overvoltages may not only damage critical loads but also switches PV inverters off causing loss of green energy at the most productive moments. This paper presents a method to limit the voltage rise by introducing small battery buffers at local production sites. A smart inverter decides whether the PV energy is injected in the grid or buffered in the batteries. The relation between battery buffer size and overvoltage reduction is presented for a typical Belgian residential distribution feeder. The influence of the buffer along the feeder is calculated by working with synthetic load profiles and solar irradiation data.
Agrovoltaic systems (combination of biomass production and electricity production by photovoltaics (PV)) are typically installed in locations with high insolation and/or arid climates in order to protect the crops against drought and sunburn. However, even in Belgium with a temperate maritime climate, summers are getting warmer and dryer, with reduced crop yields as result. This paper describes the first agrivoltaic prototype in Belgium. By use of a coupled simulation program developed in Python, a checkerboard panel arrangement was selected as an initial validation, in order to have a homogeneous ground radiation and crop growth. Potatoes were grown below the PV modules and the microclimate was measured. Results show lower temperatures below the PV modules and less transpiration and evaporation from crop and soil. The leaf area of the potatoes was larger below the PV modules which indicates an adapted light harvesting capability. Night-time temperatures were not seen to be improved under the agrivoltaic checkerboard structure, which indicates that this arrangement may not provide much protection against frost.
A sample of 12 electric bicycles offered on the Belgian and Italian markets was the subject of a comparative quality and performance study. This sample contains electric bicycles of different price categories and with different drive technologies. This paper describes the test program that was used for the study and reveals the differences that were observed between the test samples. The electric bicycles were tested on the road in the Brussels region. An appreciation of the electric traction offered by the bicycle in different situations was given: electrical assistance at start, on a flat road, when riding uphill and when decelerating or braking with the bicycle. The vehicle's driving range under real driving conditions, was determined for the different electric bicycles. Also the electricity consumption when recharging the traction battery was measured and allowed to make an analysis of the cost for driving an electric bicycle. An environmental analysis (well-to-wheel) was made of the electric bicycles and put against the environmental impact of a thermal moped and an electric scooter.
To enhance the efficiency of solar cells, a luminescent down shifting layer can be applied in order to adapt the solar spectrum to the spectral internal quantum efficiency of the semiconductor. Optimization of such luminescent down shifting layers benefits from quick and direct evaluation methods. In this paper, the potential of the adding-doubling method is investigated to simulate the optical behavior of an encapsulated solar cell including a planar luminescent down shifting layer. The results of the adding-doubling method are compared with traditional Monte Carlo ray tracing simulations. The average relative deviation is found to be less than 1.5% for the absorptance in the active layer and the reflectance from the encapsulated cell, while the computation time can be decreased with a factor 52. Furthermore, the adding-doubling method is adopted to investigate the suitability of the SrB4O7:5%Sm2 + ,5%Eu2 + phosphor as a luminescent down shifting material in combination with a Copper Indium Gallium Selenide solar cell. A maximum increase of 9.0% in the short-circuit current can be expected if precautions are taken to reduce the scattering by matching the refractive index of host material to the phosphor particles. To be useful as luminescent down shifting material, the minimal value of the quantum yield of the phosphor is determined to be 0.64.
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