Investment

The following costs have to be considered, [11] : Ci=2673 Euros for air solar collectors, C2=1203 Euros for water storage tank, C3=1093 Euros for Trombe wall, C4=890 Euros for solar still, C5=6500 Euros PV system. The total cost of the equipment is C’=12539 Euros.

Installing cost is roughly C’’=C’/4=3100 Euros.

Total cost (equipment + installing) is Csun=15639 Euros.

Investment payback

Taking into account the electricity price in Romania, cl=0.06Euro/kWh, in 2003, the total useful energy supplied by the hybrid systems would cost yearly CL=694.7 Euros/year. If we do not take into account the rate of interest, the investment Csun would be paid back in a time T=Csun/cl=24.9 years. The life time of the installations is roughly t’’=40 years, that means the solar energy user would benefit from free energy during т1=15 years.

If the state supported VAT, the costs of the suggested solar system for a small or medium sized stock raising farm would be only C’sun=12668 Euros. The investment payback time would be reduced to only t2=20 years. In this case the solar energy user will benefit from free energy during 20 years.

Conclusions

The suggested solar system satisfies the requirements of the possible users by:

• Indoor air heating at the required thermal level.

• Water heating

• Water distillation

• Air ventilation

• Space illumination

Small and medium sized stock raising farms could be organised by modules. Each module would have lairs of one hundred young animals each. A part of the modules would be experimental and another part would be reference modules. The modules organised like reference modules would be energy supplied by means of conventional tools. The experimental modules would be energy supplied both by conventional and RES tools. The monitoring of energy consumption and expenses based on RES and conventional energy would allow the users to choose the most convenient way for their specific activity. The new RES legislation initiated by the Government could facilitate the implementation of RES (e. g. by exemption from taxes).