Pressure solar water heater with copper coil

This is a compact type pressure solar water heater. There is a copper coil in the tank as the heat exchanger. The vacuum tubes absorb the solar energy then convert into heat energy, to heat the water in the tubes and the water in the tank. But we dont use the hot water in the tank, just store it in the tank as the heat energy to heat the copper coil. The water we use forshower is the one go through the copper coil. The cold-water come into the copper coil from the inlet of the copper coil, go through the copper coil, then come out from the copper coil. As I mentioned above, the hot water stored in the tank heat the copper coil, by the copper coil as the heat exchanger, then the heat energy will be passed to the water go through the copper coil. So when the water that come out from the outlet of the copper coil is the hot-water for shower.