In the Netherlands, two inverters for AC modules are being developed: the Mastervolt Sunmaster 130 and the OKE-Services OK4.

The energy yield of a 2 kWp system was monitored over a period of 1,5 years. Twenty AC modules incorporating Sunmaster inverters were mounted on a free standing array. Over a twelve month period, the system yielded 830 kWh/kWp, clearly demonstrating that losses on the DC level are extremely low. Ohmic losses due to cabling, fuses and switches are avoided and there are not mismatch losses between modules.

The OK4 inverter has been on field test since the summer of 1995. Six AC modules with OK4E inverters have been tested at the Netherlands Energy Research Foundation, ECN. The field results confirm values measured in the laboratory regarding efficiency, noise, etc. The tests revealed excellent MPP tracking with efficiency exceeding 99% at power levels above 10% of the maximum input power. Even at lower power levels, the inverter's MPPT still has an efficiency higher than 95%. At the IEEE conference in the USA in May 1996, the OK4U - the US version of the OK4 - was demonstrated in boiling water. Even under these extreme conditions the inverter operated well.

Recently OKE-Services teamed up with NKF Kabel, Holland's largest cable manufacturer and supplier of transmission systems. NKF is now collaborating with Trace Engineering, which will be responsible for distribution in North America.

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