Considering the preliminary assessment of a small scale shaft power generation system, yearly simulations where performed, for three different locations, after the following parameters:

• ORC operates at full load (i. e., whenever QinORC is available);

• heat produced in the solar field at ToutSolar = T2 + ATm (i. e. variable fluid flow in the solar field circuit);

• inlet temperature Т1пВЫаг calculated after constant outlet temperature condition and heat exchanger parameters (vide Table 1);

• heat stored in unstratified storage system at T2 + ЬТШ;

• heat delivery priority levels: 1. solar field; 2. storage system; 3. backup system;

• circuit and storage heat losses neglected.

Solar field inlet temperature calculation follows heat exchanger operation, a minimum temperature difference of 5 K and 10 K between heat transfer fluid and working fluid of the ORC was adopted for cycle 2 or cycle 3 respectively, according to regenerator outlet (T), evaporation (Tevap), and

superheating (T2) temperature values [17]. Average heat addition temperature (Ty-2) rounds 113.5 °C, for cycle 2, and 166.6 °C for cycle 3 conditions.

The use of thermal energy storage (TES) is considered regarding a daily increase of solar based operation. The size of the TES (QTES. max) is given in terms of storage time, traducing, for a general storage material, the amount of energy required to run the system for a given time period (AtTESmax), according to equation 1:

It is important to refer that such simplified system operation conditions are likely to penalize solar field results, considering that no heating regimes are considered in the non stratified storage system and that the solar field is forced to operate permanently under maximum temperature conditions.

Yearly system performance calculations where carried out for three different locations: Almeria (Spain), Cairo (Egypt) and Moura (Portugal) after hourly average data series for global horizontal and diffuse irradiation, as well as ambient temperature, whose average monthly values are presented in figures 2 a) and 2 b).

Regarding a dimensioning assessment of both solar field and storage system, system configurations with and without energy backup where simulated after the following dimensioning parameters:

• total collector area heat є [1500, 2000, 2500, 3000, 3500, 4000, 4500] (m2);

• storage capacity є [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12] (h).