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Fig. 1: Using self-generated solar power at night too!
© BMU
Grid and energy management with new PV sytems
Projektinfo 10/2010
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Multi-functional inverters and storage equipment for solar power

Photovoltaic power can be used even when the sun is not shining with the help of a battery system that provides intermediate storage. The result is that electricity not consumed during the day can be used to light the house in the evening. Alternatively, an energy company can draw on this power when demand is high. For owners of photovoltaic systems, the option of consuming the power they generate themselves has become more attractive since the remuneration for self-generated solar power was revised as of 1 July 2010.

PV systems with smart inverters and batteries can help to increase consumption of self-generated power and to ensure a secure power supply for the generating party. In addition, these systems are developing to become an important component of so-called smart grids: They can be used to make energy available when it is in demand and to control and ease the load on electricity grids.

As part of its “Optimisation of Energy Supply Systems” support initiative, the German Federal Ministry for the Environment is promoting research and development work on uninterruptible power supply (UPS) devices and equipment for intermediate storage and the use of PV power by the generators themselves. The first solutions are already available, and research is continuing on cost-effective storage technologies with long service lives.

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The use of self-generated solar power can be significantly increased using new combined systems; developers consider it possible that the self-generation percentage could be increased to over 70%. This would also result in reduced loads on electricity grids, particularly in the low-voltage range. The new combinations of inverters and energy storage devices mark the end of the conventional unidirectional feed-in of solar power: The new decentralised switching unit controls energy flows and decides whether electrical energy will be delivered, stored, used by the generator or else drawn down from the grid.

In the case of a power grid outage, these new combined systems quickly disconnect themselves from the grid. Thanks to the integrated UPS, the most important consumers in the building can remain online in stand-alone operating mode and form a stand-alone grid supported by solar power and batteries. Sensitive systems can continue to be operated using smaller integrated storage devices (2-5 kWh). However, energy-intensive devices such as an electric cooker or a washing machine may represent too much of a challenge for this approach.

Projektinfo 10/2010:
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Addresses

Battery Systems
Saft Batterien GmbH

Project partner
SMA Solar Technology AG