Details about this cheap solar heater for 50-250 ºC (its design, maintenance, lifespan, cost of heat

The cost of its solar heat (1-3 cents / kWh) can be several times cheaper than heat from natural gas or other traditional energy sources
Links to those videos:
- (in English) My mirrors of stainless steel sheets: https://www.youtube.com/watch?v=2whfOMDo7ck
- (in Russian) Technology of making my mirrors of reflective film: https://www.youtube.com/watch?v=frLAGBRUQTE
- (in Russian) Technology of making the Part #2: https://www.youtube.com/watch?v=PwQo-M87-zE
- (in Russian) Technology of making the Part #3: https://www.youtube.com/watch?v=KVVbF2YDXlY
- (in Russian) Technology of making the Part #4: https://www.youtube.com/watch?v=lT_TwYrBsjE
- (in Russian) Technology of making the Part #6: https://www.youtube.com/watch?v=a5zyqNI77Cw
- (in Russian) Technology of making the Part #7: https://www.youtube.com/watch?v=Q8cU0ZkG2Dk
- (in Russian) A short description of installing my solar heaters: https://www.youtube.com/watch?v=Ddf8iD2a8k4
- (in Russian) Detailed description of the installation of my solar heaters: https://www.youtube.com/watch?v=dCqk_yMi54o