The calculated cost of photovoltaic electricity is based on an assumed total capital investment of 5500 € per peak kW generating capacity. This figure represents low — estimate currently achievable equipment costs for roof mounted PV (compare [Cre 00] [SFV 02]). The operating costs are set at 1.5% per year of the initial investment, and a
service life of 20 years is assumed. The resulting average costs of electricity are 68 €ct/kWh in Germany and 61 €ct/kWh in EU countries overall. Optimum placement of the modules in locations unaffected by shadows allows generation costs to be reduced by about 18%. These lower cost assumptions apply also to the scenarios, since here the higher yield data form the basis of calculations. Electricity transmission from exemplary production regions with high solar irradiation (Morocco and Algeria) has been included into this consideration (s. Tab. 3). The transmission costs of 6.5 €ct/kWh are due mainly to losses responsible for 4 €ct/kWh, while the remainder arises from the capital investment for the high-voltage DC grid. Photovoltaic electricity generation is significantly more expensive than wind power by about one order of magnitude. Even imported photovoltaic electricity with its significantly greater cost efficiency does little to change this relationship.

• 5.3 Costs of Solar Electricity from Concentrating Parabolic Trough Plants

Cost calculations for this case are more difficult than for the previously treated technologies, mainly because of the high variety of possible plant configurations. The use of a heat storage medium enhances the output characteristics, reducing the losses resulting from unused excess heat and thus increasing the efficiency of the power plant [EC 94]. Appropriate scaling correspondingly lowers the price of electricity. A worldwide generation capacity of more than 7 GW would reduce the costs of the collector array, the primary component, by about half [KMNT 98]. In Tab. 3, representative calculations are provided that depict the electricity costs both locally and after their transmission to Germany at current and reduced costs of the mirrored troughs when storage is employed or not employed. A generous storage capacity insures that no heat will remain unused. This condition definitely does not lead to the most economical design, so that the cost data may be considered conservative. An additional assumption used for calculations of enhanced conservation is that 70% of the electricity has been generated from stored heat, resulting in relatively large average storage losses. The capital investments of very large solar power stations are 185 € per m2 of mirror array. (Concepts with more effective collectors are already envisioned that would reduce the costs of electricity by about 30 — 40%, and which are presently approaching the prototype stage [SM 01].) In a power plant without thermal storage, a mirror surface of approximately 6m2 per kW of electrical power (kWel) is required, whereas the addition of a heat storage with 14 FLH storage capacity raises this value to approximately 15m2/kWel. The cost of the storage medium itself lies at around 60 €/kWhei. (This value is also used for the scenario, although recent research has indicated that it would thereby be overestimated by a factor of 3, since more expedient configurations would allow two thirds of the original storage volume to be avoided [LS 02].) The capital investment for the conventional part of the thermal power plant is 525 €/kWel.

Solar thermal power stations may be used not only to generate electricity, but also to provide combined heat and power. In this case, a portion of the solar energy employed might be used for the desalinisation of seawater in order to provide an additional necessity of human existence that is often short in supply. The regional ecological, social, and economic utility of this technology is consequently improved. The turnover realized from water sales effectively reduces electricity production costs by 1-2 €ct/kWhel, thus approaching the threshold of cost-competitive generation [KNT 01]. This additional benefit is only mentioned at this point, since it has not been included into the assumptions made for the scenarios.

Since northern and central European regions are less suited for electricity generation using concentrating parabolic arrays, comparisons have been made between a region on the Iberian Peninsula in southern Portugal and areas both in southern Morocco and in

Mauritania. The transmission line load has been assumed equivalent to full capacity operation of the solar power plant during half its operating time, with the remaining 50% of the electrical energy divided in a power ratio of 2:1 in order to approximate average transmission loss. The results are compiled in Tab. 3 without consideration of possible cost reductions achieved through the additional production of fresh water. The cost of electricity from parabolic trough power stations for current component prices at good locations are comparable to the costs of electricity from wind power produced at locations capable of delivering about 1400 FLH. If the anticipated cost regression of 50% for the solar field can be realized, controllable solar power from concentrating solar power stations in northern Africa employing heat storage need not to be more expensive even after transmission to Germany.