Solar radiation collection system

Abstract

High efficiency solar radiation collectors may employ a dual flow path relative to heat transfer surfaces of the collector panel. A major air flow is confined beneath the panel, but a subsidiary (bypass) air flow at an angle to the principal air flow is also employed to suppress natural (free) flow convection at an upper side of the panel. Advantageously, the subsidiary air flow can be established by perforations in the collector panel and by creation of a suction for the bypass air. High efficiency energy collection, particularly adapted to weak and intermittent radiation environments, is further enhanced by the usage of a collector panel having a low thermal mass and providing good thermal interchange with a relatively small air mass moving beneath and above the panel, while being arranged to limit thermal conduction along the panel in the direction of air flow. Thus, a thermal gradient is established along the length of the collector panel, with a low temperature differential with the heated air mass at every position, with a fast heating response time, and with reradiation losses being minimized. By recirculating the air in a low thermal mass heat exchange system with an energy storage system in such fashion that inlet fluid is at the lowest sustainable temperature, insolation incident upon the collector is more fully utilized. The thermal energy storage most advantageously comprises what may be termed a minimum entropy system, with thermal energy in the heated air mass being interchanged in counterflow relation with a storage fluid which may be fed to different temperature level storages, dependent upon the intensity of the solar radiation available to the collector.