A fundamental aspect for the development of the ENEA technology is the real­ization of demonstrative applications on an industrial scale. The realization of a complete solar prototype plant for electrical energy production, linked to the national distribution net, needs the participation of public and private initiatives, as well as adequate investments. In fact, the prototype plant involves high costs because of the essential phase of learning in the setting up and use of new technol­ogies; to be economically viable, plants of this kind need to produce more than 40 MWe of power. But, solar plants can also be integrated with conventional thermo­electrical systems, even those with combined cycles, to improve the total amount electrical energy produced. This possibility allows using, with small changes, already working installations. So we can rely upon the electricity production system on the site and the existing infrastructure, limiting the cost for the con­ventional part of the plant as much as possible and focusing the investment on the innovative components of the new technology. In this case, the improvement in the power can also be widely modulated during the day, making the addi­tional production of the solar plant to happen during the hours when the external users’ demand is higher [53]. In line with what we have just stated, on 26 March

2007, Santo Fontecedro, Director of the General Division and ENEL Energy Man­agement, and Luigi Paganetto, President of ENEA, signed, in the presence of the Environment Minister Alfonso Pecorario Scanio and the Nobel prize winner Carlo Rubbia (former president of ENEA), an agreement protocol to make the Archimedes Project operative. This project located in Sicily at Priolo Gargallo (Siracusa) represents the integration of an ENEL combined cycle thermo-electric solar plant, comprising two sections of 380 MWe each (250 MWe for the turbo gas group and 130 MWe for the vapour group) to produce a total power of 760 MWe, with a thermodynamic solar plant based on the newly elaborated ENEA technology. The Archimedes Project is the main demonstrative realization of the ENEA technology and it will be the first application at a worldwide level of the integration between a combined cycle plant and a thermodynamic solar plant [58].

The choice of Priolo Gallo was made based on the following technical reasons:

• Currently, there is a considerable availability of land that is not being used of almost 60 ha in the central area.

• The site enjoys elevated insulation values, with a medium year direct solar irradiation equal to 1,748 kW h/m2 a year.

• The vapour produced from the solar plant, having practically the same temp­erature and pressure characteristics as that coming from the heat recovering generator of the discharge fumes of the turbo gas, will be directly emitted into the vapour turbine of the existing central part (see Fig. 107), allowing to save

on the entire conventional part (avoiding the installation of a turbo alternator group and electrical instruments for the internet connection).

• The integration with ENEL central will permit the exploitation of a series of technical infrastructures and it will ease the experimental management.

The big solar plant will improve the power from the central of 28 MWe, against an occupied area equal to 37.6 ha. The calculated electrical production net is equal to 54.2 GWe/year, with a primary energy saving equal to 11,835 Tep and the missed emission of 36,306 t of CO2. The global yearly medium earning (from solar energy to electricity) is equal to 17.3% [59].

The realization of a first plant module made of 60 collectors of 100 m, equivalent to about 5 MWe, was already planned. Such a module will permit the production of [58]:

• additional electrical energy from the solar source, which can satisfy the yearly requirements of 4,500 families;

• a saving equivalent to 2,400 t of petrol;

• lower emissions of carbon oxide of about 7,300 t in a year.

Once the demonstrative plant is completed, a more concrete commercial perspec­tive will open up, and some Italian companies have already been authorized to pro­duce components for the emerging Spanish market. In an elevated irradiation site such as in the North African area, the ENEA technology permits, in perspective, the production of 275 GW h/year of electricity at a levelled cost equal to 4.5 c€/kW h for each square kilometre of the territory, with a saving of primary energy which is equal to 60 ktep/year and an avoided emission equal to 185 kt/year of CO2 [59].

4.6 Conclusions

The concentration of solar technology can play a fundamental role in the future of the world’s energy production, allowing the production of large quantities of electricity and hydrogen, which are completely renewable and without emission of greenhouse gases, at competitive costs. The available theoretical potential in the ‘sun-belt’ countries is in fact large enough to ensure a meaningful contribu­tion to the predictable world requirements. The technological maturity regarding electricity production will be realized in the medium to brief term, and regarding hydrogen production in the medium to long term.

Especially the countries facing the southern side of the Mediterranean and the Near East countries have notable powers, with direct insulation characteristics of 50-60%, which is higher than what was found in the most favourable areas, from the southern Europe point of view. This strong insulation and the presence of large areas that are appropriate for the installation of solar concentration plants will result in energy production costs which are really lower than that in Europe.

This fact has lead to a renewed interest in proposing countries with a strong tech­nological background, such as Germany, as candidates for ambitious development plans in collaboration with the middle-southern and Mediterranean area countries.

The presence of areas which are favourable for the concentration of solar tech­nologies, in the southern European countries also (not only in Spain but also in Italy and Germany), has allowed the building of prototype plants to create a solid industrial base so that they can take advantage of, in addition to the energy produc­tion (especially from the manufacturing experience), the huge potential exploita­tion, with returns in terms of supplies for the national industries. In fact, it is evident that, being primarily a free source, the total invoice which is linked to energy production from the solar source is good for those who realize and takes care of the maintenance of production plants, and those who have the know-how are destined to exploit most of the connected businesses.

The solar concentration technology can soon be integrated, even in Italy, with other renewable technologies (Aeolian and solar photovoltaic), which will contribute to the growing European demand of ‘green electricity’ [45].