The number one
Concentrated-solar technology system use mirror with tracking system to focus a large area of sunlight onto a small area.
example number two
Passive (thermosiphon) solar water heaters on a rooftop
example number three
Good but it is difficult to construct and maintain on grownd
Example number four
The best solution but to small gathering surface
example number five
The cheapest and the best
example number six
Some examples in summary
SOLAR WATER HEATER IN WIKI
The most closest project to my, but not the Best
Good day. My short opinion.(Can discuss more on skype)
If you've read article in wiki or other sources doesn't matter . I think that there is two main problem with existing solar heater the price and the design.
All existing manufacturers gravitate to make it more expensive. Why...It’s better to ask them about the reasons.
About design, they are all trying to improve their existing solution. And make it universal for all consumers
My decision to use the cheapest materials and an individual approach to each consumer.