Abstract: A modular solar collector comprises a plurality of detachably interconnected modules forming a closed structural surface. Each module comprises a solar collector unit with a cavity receiving a heat carrier fluid through an inlet and delivering the heated fluid through an outlet, the inlet and out each having a coupling part. The unit is carried on a mounting plate which has a conduit portion for the fluid embedded therein. The inlet and outlet ends of the conduit portion each has a coupling part. The inlet end coupling part and the outlet coupling part, on the one hand, and the outlet end coupling part and the inlet coupling part, on the other hand, are matched for detachable assembly to form detachable joints between respective registering pairs of the coupling parts for detachably assembling the unit and the mounting plate.

Abstract: A form for producing a wall, particularly for an underground gallery, comprises a plurality of support members spaced from each other and casing elements supported on the support members. Each casing element includes two casing plates spaced from each other and consisting of shape-retaining synthetic resin, end and side walls extending between the casing plates, and a set of substantially parallel webs of synthetic resin. The webs connect the casing plates to provide a shape-retaining support for the casing plates and to transmit between the plates stress and pressure forces to which the casing element is subjected.