In this experiment, we covered a black stainless pipe( diameter:2.5cm, thickness:1mm ) with an acrylic transparent pipe. The air gap was about 4cm. The convection in the air gap was not taken into account in later calculations. The opening of the parabolic reflecting surface was 100cm by 100 cm, and the focal length was 20 cm. We moved the reflector by hand towards the sun after which the water temperature easily reached boiling point. The calculated result is compared with the measured one in the following figures.
Summer in Japan is characterised by fine, calm and humid weather. Solar radiation collection with a two-dimensional reflector that tracks the sun and generates electricity with a turbine would be ideal for this and similar situations.