Nicola Cardinale Department of Environmental Engineering & Physics Università degli Studi della Basilicata, Via della Tecnica n. 3, 85100 POTENZA, Italy tel. +39 0971474659, +39 097156537, e.mail cardinale@unibas.it

Antonella Guida Department of Architecture, Planning and Infrastructures for Transport Università degli Studi della Basilicata, Via della Tecnica n. 3, 85100 POTENZA, Italy tel. +39 0971474633, +39 097157104, e.mail guida@unibas.it

The M. Vallario's degree thesis of the course in Civil Buildings Engineering of the Università degli Studi della Basilicata (Potenza, Italy) is splitted up into a part of solar energy theory and devices, and a design. The design is on a simulation of a solar house in lucanian territory (40°N, 16°E; altitude: 800 m), energetically independent thanks to free solar gains and to thermal solar plants (innovative solar panels) and photovoltaics (amorphous silicon shingles): particular care is given to thermal insulation (10 cm of glass wool in external walls cavities, windows of Transparent Insulation Materials, like those in Solar House, Freiburg, and underground setting of the roofing and northern wall). PV cells, solar panels and transparent surfaces of the "living hothouse" are distributed on a south-facing surface with a 50° slope on the horizon.

Storage of the electrical energy from the PV cells is entrusted to electrochemical batteries of 20 kVAh capacity and to hydrogen cicle, usinf electolyzers, hydrogen (15 m³) and oxygen (7,5 m³) tanks, and fuel cells (2 stacks of 100 W each), that recharge batteries when their charge level is under a quarter of the maximum. From the fuel cells (PEMFC, 60-80°C of exercise temperature) depart pipes ending in a water-water exchanger, plunged in a 1000 litres hot water cistern, into which also meet the exchangers of the solar panels (natural flowing) and of the heating plant (forced flowing), whose radiators are copper coils drowned into the floor (see figure).

The annual balance of this building is largely positive, especially for thermal solar systems: in comparison with the 7752 kWh requirement (7420 domestic hot water, 332 heating) for the four users, only the solar panels collect 9353 kWh; free solar gains just through the hothouse make over than 27000 kWh/year, but a large part of them is dissipated, during summertime, through the cooling system, that uses a blowhole on the ceiling of the living hothouse, and air inlets by a conduit in touch with crushed stones behind the back wall (at 12°C constant through the seasons). Electricity produced by the a-Si cells is estimated in over 1600 kWh/y, compared with an estimated consumption of 1400 kWh; let's remember all the summertime kWh will be available all over the winter thanks to the hydrogen cycle.

Pay-back time of these plants (compared with the connection to the electric and methane grids, 3 km far, and respective plants) is evaluated approximately 29 years, in the hypotesis of their zero management cost and of the doubling of real prices of traditional thermal and electric kWh till 2010, driving higher the management costs of the traditional domestic energy plants.