The solar collectors are centrally located on a field about 500m away from the storage. The collectors are single glazed with one 4 mm thick toughened glass cover and two transparent teflon films underneath. Each collector is 12m^ and the absorber consists of an aluminum plate with a selective layer. The fluid (water/glycol) flows in a copper tube in the middle of the absorber and it passes through 80m of absorber in each collector. The collectors are coupled in parallel.
The storage is a rock cavern with the top situated 30m below ground level. It has an annular form, 75m in diameter and with 30m height. The walls are unlined and the roof Is sprayed with shotcrete. There are two separate systems for inlet and outlet and the pipings are movable as the storage is stratified.
The temperatures in the cavern will vary between 40 to 90°C. As there is no heat pump in the system the solar collectors then have to produce energy at temperatures over 96°C because of the two heat exchangers between the solar collector circuit and the rock cavern water.
The distribution system is a low temperature system with a maximum temperature of 70°C in the winter and 55°C in the summer.