Abstract: A closed core base having concave channels in its top face is fitted with a thermoplastic lens having corresponding convex channels. The channels form transfer passages which carry a liquid medium which absorbs solar energy as it flows through the passages. The base consists of an insulating core material having an outer skin fabricated in a solar absorbant color. The sides of the base are sloped for stacking and extend above the top of the conduit to support a clear cover. The core of the base is coated with a reflective material and filled with insulating material.