ENERGYSTORAGE
industrial partners Voltwerk and Tenesol, as well as with French and German research institutions. The aim is to create an integrated energy conversion and storage kit, capable of production on an industrial scale, for decentralized on-grid, residential PV systems. Li-ion technology is required in order to meet the need for 20 years‘ battery life under demanding cycling conditions.
The development phase of the project, which commenced in August 2008, has been completed recently, and it is now moving into its test and evaluation phase. This involves the deployment of 75 Sol-ion energy kits for field trials across France and Germany.
The Sol-ion trials will see Li-ion (lithium-ion) batteries used in PV systems on the largest scale ever tested in Europe. These trials will be used to assess the performance of the technology, its economic viability, the added value of energy storage in an on-grid system and the benefits to stakeholders.
The project will also investigate the impact of energy storage on demand side management issues such as peak shaving effects and the potential for integration within future smart grid concepts.
Self-consumption
The Sol-ion system will provide strategic management of the power flows within the PV panels, the battery, the house and the grid. This will shift excess power production at noon to make it available for use in the evening, maximising ‘self-consumption’ and leading the movement towards energy autonomous buildings.
Initial simulations have shown that the addition of energy storage to a PV installation could increase self-consumption from 30 to 35 percent up to 60 to 70 percent. The Sol-ion trials will assess two different approaches to self-consumption in the German and French markets.
In Germany, the approach will be based on self- consumption of solar power while the household is connected to the grid, with solar power being fed in parallel to the household and to the grid. In France, the approach is based on self consumption of solar power while the household is disconnected from the grid, investigating the household’s capability for island operation in case of grid failure.
System design
The Sol-ion battery is connected to the grid inverter through a separate battery converter. The interaction of the inverter and battery converter within the Sol-ion kit has been optimised for an optimal overall system performance. Both components have a high efficiency (>97 percent).
The battery is based on Saft high energy Li-ion modules, with a nominal voltage of 48 V and capacity of 2.2 kWh capacity. These compact, maintenance-free modules feature an advanced, robust industrial design, and they can easily be connected in series or parallel to create the desired voltage and capacity for each installation. A particular advantage of Li-ion battery technology is its highly flexible operation so that it can deliver both energy and power. The entire battery DOD can be utilised if required while it is also suitable for partial cycling with no reduction in cycle-life. The Sol-ion kit has been developed to accommodate PV energy production of 5 kWp (peak) with a battery rated from 5 to 15 kWh and a nominal voltage of 170 V to 350 V.
Conclusions  Energy storage is vital in smarter grids  Distributed on-grid PV systems with battery energy storage can make energy available where and when it is needed.
 Decentralized storage provides value to all stakeholders
 Li-ion is a promising energy storage technology and industrialized systems are being developed and trialled
© 2010 Angel Business Communications. Permission required.
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