Steam and gas turbines powered by coal, uranium, oil and natural gas are today’s guarantees of power-grid stability. They provide base-load and peak-load power. However, turbines can also be operated with high-temperature heat from concentrating solar collector fields (Figure 5). Solar thermal power plants of this type with 30 to 80 MW output power have already been operating successfully in California for over 20 years, and new plants are being constructed right now in the USA, Spain and other countries, with up to 1000 MW of output power. By 2015, as much as 10 GW of solar-thermal power capacity could be installed worldwide, and by 2025, even 60 to 100 GW At present, nearly 1 GW is online. According to a current study, today’s solar energy price of 27 €-ct./kWh in Spain could decrease to below 10 €-ct./kWh .
The example of Andasol in Andalusia can be used to illustrate the principle (see the picture on p. 121). The plant consists of three installations of the same size, each using long, trough-like mirrors with a parabolic cross-section, similar to oversized rain gutters. In Andasol 1, an overall area of nearly two square kilometers contains more than 600 of these collectors, each one 150 meters long and 5.7 meters wide. All together, the mirrors have a surface area of more than 500,000 square meters (Figure 5).
Electric motors turn the collectors around their long axes to follow the path of the sun. The solar radiation, which falls perpendicular onto the collectors, is concentrated by a factor of ca. 80 in their focal line. Along this line, the absorber tubes are mounted. Their surfaces are covered with a special coating which absorbs sunlight especially well and converts it to heat. The tubes are filled with a synthetic oil, which is heated to nearly 400° C. The hot oil flows into a heat exchanger where its heat vaporizes water. As in a conventional power plant, the hot water vapor – steam – shoots into the turbines, which are connected to generators that produce electric power. The temperature of the steam at the turbine entrance is comparable to that in nuclear power plants. As in any steam power plant, the
POWER GENERATION IN THE MENA COUNTRIES
□ Exported solar power
□ Oil/Gas ■ Coal
Power generated on the basis of sustainable and fossil energy sources in the MENA countries to supply the increasing energy demand. Exports of solar power to Europe and the additional power for desalination of seawater in the region are included.
POWER GENERATION IN EUROPE
□ Imported solar power
□ Solar thermal
□ Heating oil
□ Natural gas ■ Coal
Power generated on the basis of sustainable, fossil and nuclear energy sources in European countries to supply the energy demand, including imports of solar power from the MENA countries.
2050. With the exception of wind and hydroelectric power, sustainable energy forms will hardly play a role in electric power generation there before 2020 (see Figures 6 and 7). At the same time, we assumed in our study that the phasing-out of nuclear power in many European countries and the stagnation of the combustion of lignite and anthracite coal for environmental reasons will lead to an increased utilization of natural gas. We used the official scenario of the European Commission up to 2020, which presumes a decrease in nuclear power plants of one percent per year.
Up to 2020, the growing fraction of sustainable energies will for the most part serve to reduce the combustion of fos – 114 | sil fuels. They can however also to some extent replace the
electric power from pumped-storage plants. According to our scenario, fossil-fuel plants will be used by 2050 only as a backup, to some extent also as supplementary power source for solar-thermal plants. This will reduce the combustion of these fuels to an acceptable level and will put a limit on the otherwise soaring costs of electric power. Fossil fuels will be employed to guarantee that power is always available, while their consumption will be strongly reduced by the use of sustainable energy sources.
To complement the mixture of sustainable power sources, an efficient backup infrastructure will be necessary: On the one hand, it must provide a secure generating capacity oriented to consumers’ needs and based on gas – fired peak-load plants which can react quickly to power shortages; on the other, an efficient power grid must be established to allow the transmission of power from the most suitable production sites for sustainable sources to the major centers of power consumption. One possible solution is a combination of high-voltage DC transmission lines (HVDC) with a conventional AC grid.