3.1 Concentratiing solar power technology: clean energy for power tenability

Energy availability has always been an essential component of human civilization. In the last 150 years, the yearly average rate of world energy consumption has grown by about 2.3%. The energy requirement of human beings, mostly satis­fied by fossil fuel, has grown so much that it has overcome sum of the thermal energy coming from the Earth’s core and from the ties induced by the Sun and the Moon. The endogenous energy of the Earth has been more than doubled by human activities. However, it is important to underline that the overall human energy con­sumption is only 1/10,000 of the energy received on the Earth from the Sun. Solar radiation, despite its scarce density, remains the most rich and clean energy source on the terrestrial surface [45-47].

This statement, together with the exhaustion of fossil fuels and the growing environmental risks, leads us to seriously consider solar energy as one of the most important candidates for the planet’s energy tenability project.

The greatest part of the solar source’s potential can be found in the so-called ‘sun belt’, which is the area of the planet that receives the highest quantity of solar radiation, as shown in Fig. 81. In particular, Northern Africa and the Middle East have large areas with a high level of solar radiation which is suitable for the installation of a large number of solar thermal systems as they cannot be used in any other way. These countries spontaneously stand out as candidates for the intensive development of solar energy [45].

From the recent MED-CSP research, commissioned by the German Ministry of Environment Policies and carried out at the Aerospatiale Centre DLR, it has

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Figure 81: World map of solar radiation underlining the sun belt.

been shown that the solar energy potential available in the countries on the Mediterranean coast is much larger than the actual electrical energy consump­tion of the area which includes Southern Europe, the Middle East and Northern Africa. Besides the DLR and other German organizations, other centres of research such as NERC (Jordan), CNRST (Morocco), NREA (Egypt) and NEAL (Algeria) contributed to the development of this study. This project shows that a common interest could link European countries (energy importers and technol­ogy exporters) with the Northern Africa countries (owners of fossil fuel resources and solar energy who will see a significant growth in their energy consumption in the next few years) [45, 48]. To exploit this huge solar energy potential, the concentrating solar power (CSP) technology is very useful. This technology exploits solar radiation, concentrating it using mirrors for electricity production and also for the realization of high-temperature chemical processes, for example, the production of hydrogen. A more detailed description of CSP technology is given in par. 4.4. This technology can be considered as a competitor of the photovoltaic technology, which is already common and is growing in Europe (actually, this is only partially true). On this matter, two aspects have to be considered: first, the photovoltaic technology exploits both the direct radiation and the spread (diffuse) radiation and so it is also suitable in areas such as Northern Europe where direct solar radiation is scarce; second, it is fit for many different applications (from a few watts of a mobile phone’s solar battery char­ger, to the megawatts of dedicated solar systems, passing through a few or tens of kilowatts used in many applications in the residential or civil field). CSP tech­nology, on the other hand, exploits only the direct radiation and lends itself poorly, excepting in a particular situation or only in thermal applications, to the realization of small dimension systems. As regards systems that have a capacity of about or more than a megawatt and that are used in areas with strong direct radiation, CSP technology allows achieving a cost for electrical energy produc­tion which is much less than that for the energy produced using photovoltaic technology, and this advantage, in this specific case, is destined to last for a long time unless there is a radical technological improvement in the photovoltaic field [45, 48].

Considering only the European part of the Mediterranean area, we can observe a sort of integration between the two technologies: the photovoltaic technology is installed where there is lesser direct radiation and in applications which require from a few kilowatts to a hundred kilowatts of power. On the other hand, CSP technology is installed in areas with stronger direct radiation and in medium-large power systems (starting from a megawatts of power). It is also possible to think of a situation where Europe increases its own consumption of ‘green electricity’ by taking it both from the different renewal sources available in the area and from the solar energy imported from the most suitable regions.

To highlight the significance of this project, which has got many prospects, it is necessary to point out that the density of the solar energy received in the Mediterra­nean southern coast and its territorial characteristics allow to cut the solar energy production costs, which are then invested to produce solar energy in the southern

European area; moreover, large areas which cannot in any case be used for agricultural purposes are available on the coasts of Northern Africa and the Middle Eastt. Since the cost for high-tension and continuous line electricity transmission for a distance of about 1000 km, of which 100 km is by submarine cable, is about 0.7-1.5 c$/kW h, it is not illogical to think of realizing in those regions — inside a wider project of social and economic integration — solar energy production capable of satisfying the growing requirement for electricity in Northern Africa and also a part of Europe [45-47].

With the regard to this matter it is important to underline how, despite mere energy considerations, the so-called ‘Mediterranean electric belt’ has been studied for a year, which will shortly allow the complete electrical interconnection between the Mediterranean countries and the European electric net.

Considering what we have just stated, it is clear that the wide exploitation of the solar source in the Mediterranean area is a very important topic with a high politi­cal and economic agenda since it has important consequences in terms of bringing about the integration of the northern and southern parts of the world and also in terms of development of pacific relationships.

As regards future prospects, the direct production of hydrogen, mainly by CSP technology, will allow the sun belt to increase the production of energy. Presently, a few Southern European areas, Spain in particular and also southern Italy, have a fairly good potential, which allows them to exploit the CSP technologies to increase the renewal quantity of electricity production.

Spain in particular is in a favourable situation because of both the presence of a huge energy potential and the remarkable experience it has with experimental activities developed since 1981 at the Plataforma Solar De Almeira.

As regards Italy, currently, there are no accurate studies on the energy potential which can be exploited using the CSP technology. The MED-CSP study [48] estimates that the ‘technical exploitable’ potential is about 88 TW h/year while the ‘economically exploitable’ potential is about 5TW h/year; actually, these figures refer to very approximate values. Despite this, it is clear that the principal aim of

using the CSP technology is to obtain advantages, in addition to economical advantages, by the exploitation of the energy potential in the areas that are rich in the solar source. This is more justified if we consider the case of Germany which has been pursuing the development of this technology for many years although its economically exploitable energy potential is almost non-existent. Since the primary source is free, it is also important to underline that the total turnover related to energy production from solar energy benefits those who realize this and take care of the production systems; those who own the know-how are then designated to exploit the biggest part of the business connected with solar energy production [45].