To assure a complete self-sufficient system, the air solar system should cover the 20% of the remaining demand. With this aim, 12 sq m of Solarwall system (the same surface of the solar panels) has been added.

Figure 11 shows how the system works. A fan collects the preheat air from the Solarwall and it is introduced through a special insulated channel directly to the living room. The system keeps the house dry also when it is not occupied for long periods. In sunny days the air system will delay the switching on of the conventional solar water system.

The calculation indicates that only in December the self-sufficiency could not be reached. Nevertheless, the results depend completely on the weather. In fact, on a sunny day the house could be heated mainly by the air solar system, but on a cloudy day the risk to be insufficient is very high.

Then, it is necessary to integrate the solar system with a boiler, using renewable energy source, which means a wood heater.

The wood heater

When necessary, a wood heater integrates the solar system and covers the small daily energy need, about 5,3 kWh/day. This small requirement can be satisfied burning around 1 kg of pellets o using directly the local olives trees pruning in a stove with a 85% efficiency.

In order to cover the remaining winter heating demand not cover by solar energy of 171 kWh, only 43 kg of pellets (that means 7,74 Euro for the whole period) or 40 kg of olives trees pruning is required.