Jan Cappelle

Introducing small storage capacity at residential PV installations to prevent overvoltages

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.

The use of the adding-doubling method for the optical optimization of planar luminescent down shifting layers for solar cells

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.

Beyond the plug and socket: Towards safe standardized charging infrastructures

This paper will present the current evolution in the field of charging infrastructure standardization, highlighting the main development areas of safety, compatibility and performance, also giving special interest to ongoing European developments in the field as well as to the residential charging field.

Home charging of electric vehicles in Belgium

The demand for green alternatives in the transportation sector is resulting in an expanding supply of electric vehicles. This triggers the need for both public and home charging infrastructure. In Flanders, five living-lab platforms were launched and funded by the government [1]. The main goal of one of these projects, i.e. the EVA-platform, is to deploy and monitor a public charging network. Nevertheless, in those five living-lab platforms no special attention is paid to home charging infrastructure. However, fleet tests have shown that 90-95% of the time electric vehicles will be charged at home [2]. This proves that home charging infrastructure is an indispensable part of electric driving. Regarding home charging, the electrician will often be the first point of contact for the general public. At this moment however, electric vehicles and home charging are still unknown concepts for this stakeholder group. Therefore, it is important to provide them with appropriate information concerning standardization and safety, to give an overview of the existing variety of home charging stations and to suggest the possibility of self-assembly of home charging stations. This paper describes the content of the current hands-on training sessions, organised in the context of the Flemish research project “Home charging of electric vehicles”, which has started to fill this hiatus. Special attention is drawn to the given installation guidelines of three phase charging stations and to problems experienced by some electric vehicles when charging on the 3×230V part of the Belgian distribution grid.

Experimental validation of adding-doubling modeling of solar cells including luminescent down-shifting layers

Luminescent down-shifting (LDS) layers applied on top of solar cells can potentially increase solar cell performance due to the better match of the incident irradiance spectrum reaching the cell to its spectral response. In this study, the adding-doubling tool is presented, which allows fast predictions of the influence of LDS sheets on solar cell performance. The model is validated by comparing its predictions to experimental data. Four LDS sheets including different conversion materials were investigated. The modeling tool was able to predict the external quantum efficiency with an average deviation of 0.02.