At Ottrupgaard, Denmark, a pit water heat store of 1,500 m3 and a lid area of about 700 m2 are built for seasonal storage of a solar collector field of 560 m2. The lid price is the largest component of a pit water store with a cost share of about 57%, more precisely 1,163 Dkr./m2.
The development of lid constructions is crucial for the development of pit water storage as it seems that the development of the other main component for large-scale solar heating, the solar collectors will not have a breakthrough in the near future.
The Ottrupgaard lid design is basically a sandwich element construction of PUR-foam between two metallic covers. The elements are joint in situ by special steel profiles. A two-step sealing with silicone mass and bitumen-tape is applied to tighten the construction.
The project is to find and evaluate a floating lid design at Ottrupgaard and give a survey of the known floating lid design for pit water storage.