Research to Business
Offer: 572

Innovative circuit for photovoltaics

Transformerless inverter for thin-film or reverse-side contacted solar cells makes plants more efficient.

The use of renewable energies must be increased if sustainable energy supplies are to be achieved. Photovoltaics makes a key contribution to the planned "Energiewende". At present, more than 36,000 megawatt of solar capacity are installed in this country. Inverters are needed to feed into the grid the DC-current obtained from the solar generator.

If the negative pole and the positive pole, respectively, of the inverter circuit are not grounded, various types of solar cells can suffer a loss of yield. Thus, leakage currents in thin-film solar cells often produce corrosion of the conducting layer. Cell efficiency can drop significantly in solar cells contacted on the reverse side.

KIT scientists of the Institute of Electrical Engineering developed a circuit which allows the negative or positive poles of the solar generator to be grounded. Corrosion of the TCO (Transparent Conductive Oxide) in thin-film solar cells can thus be prevented. In addition, the efficiency of solar cells contacted on the reverse side can be maximized by avoiding the polarization effect.

The benefits of the invention are apparent from other details: The circuit contains no transformer, which results in high efficiencies and low weight. Only five transistors are required, which allows the devices to be built at very low cost. Moreover, the inverter, in line with current standards, has reactive-power capability. As a consequence, other grid services can be performed. The high efficiency of the converter, low investment costs of the equipment and, if applicable, the avoidance of losses in efficiency by grounding one solar generator pole in summary result in a high return on investment of the photovoltaic plant. As this is a monophase circuit, the unit has been designed mainly for private small solar plants.

The KIT is looking for partners interested in applying this technology.

Your contact person for this offer

Dr. Aude PĂ©lisson-Schecker, Karlsruhe Institute of Technology (KIT)
Innovation Manager Energy, Innovation and Relations Management (IRM)
Phone: +49 721 608-25335


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