I want to attach a photovoltaic panel on top of a thermal absorbing system. My idea was to to replace or add a steel backing to the photovoltaic panel. The thermal system would consist of a box filled with water, which would be in direct contact with the panel. But before I begin my idea I need to know whether it would work. I need to know the heat transfer coefficient between steel and water so that I can find out whether the photovoltaic panel would be able to provide enough heat. But I don't know where to get the heat transfer value. I was thinking about using the formula q= h*A*deltaT but I figured this would leave me with two unknowns. I searched around for a value for the heat transfer coefficient between steel and water but no website gave me a value. Could someone please tell me a value or a correct formula. Thanks for the help.