An AC module is a PV module with an integrated DC to AC converter, which can be connected without the use of other equipment tot the public grid. Although the innovative component is the mini-inverter (size around 11x11x3 cm), the combination with a (DC) PV module can be seen as a new product aimed at new markets.

The availability of new electronic power components has made it possible to develop small-size converters, specially designed for integration into the back of a PV module. In the Netherlands R&D in this field is carried out in a technology cluster formed by the inverter industry together with research institutes and PV and energy companies. It was in this case directed towards the achievement of an expected lifetime comparable with that of PV modules, as well as high efficiency and the fulfilment of EMC standards.

The mini-inverter is ideal for mass production. It has led in the Netherlands to new companies, working in the field of PV, so broadening the scope of the PV industry. Two mini-inverters (Mastervolt and OKE-Services) are currently in production for the European market. Field experiments revealed that the yield of a PV system consisting of AC modules is about 4% higher than that of conventional dispersed PV systems, due to reduced mismatch and DC losses. Mini-inverters for the USA and Japanese markets are now in preparation.

The AC module concept is truly modular and flexible, and this may generate new markets. For the first time it is possible to install a small affordable PV system consisting of one or more AC modules, and extend it later. In the Netherlands single AC modules were installed on the roofs of over hundred houses by the end of 1995, while a further 1200 or more are to be installed this year.

For further reading, go to AC modules: performance assessment in PV Power, Issue 6, December 1996

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