ENIS - Intermediate Systems
From Solar Plants
Intermediate systems use steam to produce electricity from the sun, in a similar manner to conventional steam power plants. The main difference is that the concentrated solar power (CSP) to generate heat, use carbon-free, clean sunlight instead of the fossil fuels and nuclear energy. In intermediate systems solar radiation is concentrated by parabolic shaped mirrors. These mirrors, arranged in rows, are more than 400 meters long and are made of parabolic mirror segments that ensure maximum use of sunlight daily.
Basic elements of the intermediate is shown in the figure:
1. Parabolic mirrors
2. Receiver tubes
3. Oil transporting heat
4, 6. Heat exchanger
5. Storage tanks
11. Cooling Tower.
The principle of operation of the intermediate system is as follows: under direct sunlight of a solar plant, parabolic mirrors, arranged in rows concentrate solar radiation. Parabolic shape of the mirror provides the highest efficiency of the system, because it allows the sun tracking, so that mirrors store solar radiation on a continuous basis throughout the day. Radiation is stored on specially coated vacuum receiving tubes, that convert it into heat. Then, heat is transferred by means of a special oil, which receiving tube are filled with. Oil circulating in the system is heated to a temperature of 400 ° C, through a heat exchanger the oil heats the steam, which in turn feeds the traditional steam turbines.
A key element of intermediate systems is receiving tube, which has a decisive impact on the overall performance and power efficiency. It is characterized by a high degree of absorption of solar energy, as well as low emission of thermal energy (heat emission).
The highest optical and absorption properties of receiving tubes are ensured by a special absorption coatings with their long-term thermal stability. This contributes to a significant reduction of the cost of electricity and to production maximization.
The use of concentrated solar power plant is the most desirable in the large scale solutions with capacities of up to 300 MW. The most appropriate location for this type of plant are large dry and uncultivated areas, which makes getting the land relatively cheap. Climatic conditions in Poland are not conducive to investments in intermediate solar power systems.