>>13524229Mirrors are cheaper. Why, are you going to say they are not?
Your idea of a lens has been done in small scale with solar panels. A dish tracks the sun and follows it with a small solar cell under a large plastic lens. The cell is an expensive high-efficiency model and it is water cooled because thats a lot of heat. Practically speaking the whole apparatus cost more money than the cells or the lens or a mirror of similar size mounted. Bottom line the lens is only practical with solar cells, not with a central water heater.
