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The increasing number of Distributed Generation Units (DGs) in distribution grids is challenging the way electrical systems are designed and operated. For traditional power systems, Low Voltage (LV) networks play a passive role in voltage regulation, but when DGs are present the LV network may play an active role in voltage control. In this paper, a voltage control strategy using mini Combined Heat and Power (mCHP) is proposed. For this aim, the electrical and thermal dynamics of a mCHP plant are considered, a voltage controller is designed and a voltage control mode is developed, which prolongs the regulation action of the mCHP unit using heat storage. Simulations are conducted considering thermal and electrical demand of a typical multi-family house in the climate region of North Rhine-Westphalia, Germany. Aspects of resulting voltage and thermal profiles, compared to a traditional heat lead mode, are discussed for an exemplary day.

AbstractStriving for sustainability, most industrialised countries make increasing use of renewable energy sources to meet their energy demands. This causes power generation to become more decentralised and volatile, making flexibility in production (i.e. energy demand) a fundamental necessity for manufacturing companies. Hence, it is to be expected that companies which attain a symbiosis of renewable energy applications, efficient technologies, and innovative approaches to production organisation will have a competitive advantage in the future. The EU funds research in this direction as part of the REEMAIN project, amongst others. In particular, a concept for Resource Networks is developed. These networks aim to manage production using renewable energy sources by dividing a complex factory into smaller subsystems including energy suppliers and consumers, as well as storages to reach this symbiosis. This paper explains the concept and its application within Fraunhofer IWU's E3-Research Factory.

Abstract The increasing global energy demand, the foreseen reduction of available fossil fuels and the increasing evidence off global warming during the last decades have generated a high interest in renewable energy sources. However, renewable energy sources, such as wind and solar power, have an intrinsic variability that can seriously affect the stability of the energy system if they account for a high percentage of the total generation. The Energy Flexibility of buildings is commonly suggested as part of the solution to alleviate some of the upcoming challenges in the future demand-respond energy systems (electrical, district heating and gas grids). Buildings can supply flexibility services in different ways, e.g. utilization of thermal mass, adjustability of HVAC system use (e.g. heating/cooling/ventilation), charging of electric vehicles, and shifting of plug-loads. However, there is currently no overview or insight into how much Energy Flexibility different building may be able to offer to the future energy systems in the sense of avoiding excess energy production, increase the stability of the energy networks, minimize congestion problems, enhance the efficiency and cost effectiveness of the future energy networks. Therefore, there is a need for increasing knowledge on and demonstration of the Energy Flexibility buildings can provide to energy networks. At the same time, there is a need for identifying critical aspects and possible solutions to manage this Energy Flexibility, while maintaining the comfort of the occupants and minimizing the use of non-renewable energy. In this context, the IEA (International Energy Agency) EBC (Energy in Buildings and Communities program) Annex 67: “Energy Flexible Buildings” was started in 2015. The article presents the background and the work plan of IEA EBC Annex 67 as well as already obtained results. Annex 67 is a corporation between participants from 16 countries: Austria, Belgium, Canada, China, Denmark, Finland, France, Germany, Ireland, Italy, The Netherlands, Norway, Portugal, Spain, Switzerland and UK.

The requirements for the contact metal deposited on solar cells are rising as the size of solar cells grows. Particularly, the improvement of the electric properties – especially the conductivity – is attracting interest. Light-induced plating is deemed to be a sophisticated approach to deposit a highly conductive metal layer on an arbitrarily generated seed layer. Although already in industrial operation to some extent, the mechanism is not understood in detail. In addition, the aim of avoidance of cyanide containing electrolytes for silver deposition is high. We will show voltammetric techniques are an appropriate approach investigating these topics. 23rd European Photovoltaic Solar Energy Conference and Exhibition, 1-5 September 2008, Valencia, Spain; 1785-1788

Abstract Despite the comparatively limited stock of vehicles, heavy-duty road transport is responsible for a major share of CO2 emissions from the European transport sector. Electric trucks powered by overhead lines, so-called trolley trucks or catenary hybrid trucks, have been proposed as a potential GHG mitigation option. However, from the perspective of the energy system, trolley trucks constitute an additional and inflexible electricity demand. Here, we analyse scenarios with an ambitious European market diffusion of trolley trucks and their impact on the electricity system and CO2 emissions. Our results show that trolley trucks can noteworthily reduce the CO2 emissions from heavy road transport even when the additional CO2 emissions from electricity generation are taken into account. Furthermore, the actual impact of the additional load from trolley trucks on the total energy system is limited. Compared to the anticipated electricity demand from passenger cars in 2030, trolley trucks require less energy and the load is more equally distributed over daytime. Our findings thus show that electric trucks are an interesting option for CO2 mitigation in heavy road transport.

Abstract The performance of n-type Si back-contact back-junction (BC-BJ) solar cells under illumination with high energy ultraviolet (UV) photons was investigated. The impact of the phosphorus doped front surface field (FSF) layer on the stability of the front surface passivation under UV illumination was investigated. Lifetime samples and solar cells without the front surface field showed a significant performance reduction when exposed to ultraviolet light. The surface saturation current density ( J 0e ) increased from 48 to 446 fA/cm 2 after the UV exposure. At the same time the efficiency of the BC-BJ solar cells without the FSF diffusion reduced from 19.8% to 14.3%. In contrast to the lifetime samples and solar cells without the FSF diffusion, the tested n + nn + structures and the BC-BJ solar cells with applied FSF diffusion profiles were significantly more stable under UV exposure, i.e. J 0e increased only by a factor of 25% and the efficiency of these cells decreased only 0.3% abs by the UV illumination. Finally it was shown that the performance of the UV-degraded solar cells without FSF could be improved during a forming gas anneal (FGA). Due to application of FGA the efficiency almost fully recovered from 14.3% to 19.6%.