Basic knowledge  ___________ ___________on solar thermal
What is the difference between solar thermal and solar photovoltaic?
Currently, there is a big confusion between the two.

photovoltaique intégré dans la toitureA photovoltaic cell generates electricity. It faces south, it must be inclined at 35 degrees to maximize production across the year.
In France it is systematically integrated into the roof (the tiles are removed) because the purchasing price is much more interesting vs a non integrated solution. This integration is the only source of defects related to PV.

capteurs thermiques inclinés en rez de jardin pour le chauffage et l'eau chaudeThe temperature collector is used to heat a house and/or to produce domestic hot water, it must be inclined generally at 60 / 70 ° (can even be installed vertically), so it can provide part of the winter heating and DHW during the summer months without causing overheating. In order to maximize the heat production, the collector must be strongly inclined to collect the sun ray, as the winter sun is low. Here, we are not looking for the maximum yearly production but rather the best fit between heat production and the needs. Obviously producing Domestic Hot Water for camp site in summer,  would need to maximize summer production, i.e. the collector should not be inclined too much as the summer sun is very high.
 Is it true that the ultimate flat plate collectors are better than evacuated tubes?

Under normal household use, a flat collector average yield is actually better than average evacuated tube collector (calculated against the overall surface). See detailed study  here

 We often hear that solar heating is not possible with dissipation in radiators, what is it?

This is absolutely false, if you read the proposed study on the above link, you understand it is key the collectors work at low temperatures (low delta T). Obviously make solar heating in a thick concrete floor (20/25 cm) capable of storing a large amount of energy is very efficient. We are going to illustrate this by comparing a simple solar DHW, a house heating with radiator and a direct floor heating.
We'll take the best collector tested by the CSTB, the French Testing organization. It is a Tinox coated collector: the top line in light blue. At an outside temperature of 0 ° , the delta T will be equal to the collector temperature.

Direct Floor heating require a temperature of 30/35 ° C: yield is then around 60%.

In case of radiator require temperature is 45/50 ° C: yield is around 55%

Case of DHW, temperature is 65/70 ° C: yield is around 45% see even worse if one wants to raise the water at 80 ° C

Conclusion, one cannot promote solar DHW and at the same time says that solar heating with radiators is not performing!

How much training does it take to become a good solar installer?

The solar installer is a carpenter, a plumber, an electrician with knowledge in automation and industrial IT. From our standpoint, we need a serious training to acquire these skills, in France the BTS level that seems most appropriate.