Ah I get it now. It's an electric hot water storage system. I think it would work pretty well. Any heat supplied by the solar pre heater will not need to be provided by the electric element in the storage heater. But the total increased surface area of 2 tanks will lose more heat energy then just (say) a stand-alone solar-electric heater where all the hot water is stored in ONE tank with modern efficient insulation.
Many years ago I had a neighbour who had a flat black tar+concrete roof and about 200 feet of hosepipe on his hot roof feeding into his hot water system. And walls of his house made from local sandstone (from his own property) about 2 feet thick. Most people thought he was a bit crazy but I guess he was many years ahead of his time...