Already with the current efficiency of approx. 10%, solar power plant located in the desert and covering an area 300 — 1000 km2 (ok. 1/3 the territory of Egypt) would be able to produce energy equal to this, which the whole world consumes, and the solar cell has a surface 30 m2, placed e.g.. in southern France, can provide energy for a family of 4 all year round.
The efficiency of photoelectric batteries increases with greater intensity of solar radiation and with the direction of incidence of these rays relative to the plane of the battery. Photovoltaic batteries are already installed in single-family houses, mostly like this, where there are no traditional electric lines or on mobile "trailer" houses.
There are two battery installation systems:
1) anywhere next to the house or on the roof, as independent structures, of own design,
2) jako części składowe pokrycia dachu, e.g.:
— ARCO Solar „Batten and Sean” — fotoelektryczny dach i General Electric „Solar Shingle” — (sunny shingle), - two American companies, which propose to lay the batteries as top covering layers on the previously planked traditional rafter structure, which is the basis,
— Solarex, which proposes batteries as roof elements integrated with the structure of high stiffness, not requiring direct rigid backing, e.g. formwork.
It follows from a cursory balance sheet, that the electricity demand of a family of four living in a single-family house in Poland is approx. 3000 kWh per year; to fully cover them, Install photovoltaic batteries with a total area of approx. 35 m2. It should be accepted, that the annual dose of total radiation on the horizontal surface is 950 — 1050 kWh/m2, in direct sunlight, max. = 7 do 8,4 kWh/m2 and min. = 0,5 do 0,8 kWh/m2, and battery efficiency - approx. 10%.
Such a battery surface, requiring only optimal orientation to the sun depending on latitude, it is very little interference in the architecture of single-family houses. Apart from the placement of photoelectric batteries, a small room for lead batteries should be provided, which are an integral part of the system.
The high cost of photoelectric batteries is still an obstacle to their massive use, but it is not excluded, that this is the type of use of solar energy, because of its advantages, will be most widely used in the near future.