As well as the energy storage, the use of conventional energy backup for a 24 hour demand of mechanical energy is also considered in this paper. In that case, the annual solar fraction, SF, (the ratio of solar heat to total heat delivered to the cycle) is the characteristic parameter of the performance of the system.

Together with the specific power production, SP, (the ratio of annual mechanical energy produced and solar field area), this analysis opens way for a future economical analysis of the system, after adequate cost information for solar field, storage system and backup energy. The results obtained for both cycles at the three tested locations are in figure 4.

The results presented in table 5 allow a comparison of the system, at the three tested locations, using a reference condition of (SC = 6 h, SP = 300 kWh. year/m2).

Fig.4 — Solar fraction (SF) and specific production (SP) results obtained for yearly simulations of cycle 2 and

3 at Almeria (SP), Cairo (EGY) and Moura (PT)

5. Conclusions

Project POWERSOL [1] aims at the development of a small scale solar thermal based mechanical power/electricity generator, suitable for applications with lower requirements of maintenance and operation expertise, as those found in industry, desalination or small communities.

In the present article, a performance analysis of such a power system at three different locations and at two different working temperatures is presented, allowing a preliminary assessment of its design.

Simulation of the system working without backup energy allowed the determination of the critical storage system dimensioning, as well as a preliminary (and conservative, in view of the simplified simulation conditions) estimation of overall system efficiencies, which present values, at the best location tested, of 5.0% and 7.8% for the lower (C2) and higher (C3) temperature cycles, respectively.

Further development of the project, allowing a better cost/performance estimation for the different solar thermal collector technologies addressing the cycles operating temperatures, will enable a

final economical analysis of the system, following the approach of solar fraction and specific

power production estimation presented in this paper.

References

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