Water Walls
From Swikipedia
Introduction
A water wall is a thermal storage wall made up of drums of water stacked up behind glazing. It is based on the same principle as that of the Trombe wall, except that it employs water as the thermal storage material. Due to the higher specific heat, water walls have the ability to store more heat than concrete walls. They are painted black externally to increase the absorption of radiation. The internal surface can be painted with any other color and can be in contact with the interior space directly, or separated by a thin concrete wall or insulating layer. As the storage in the water wall is a convective body of mass, heat transfer is very rapid compared to a masonry wall.
References:
