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Major Natural Environmental Factors Affecting the Performance of CSP Plants

Reported from CSPPLAZA: “It is generally believed that the main natural environmental factors affecting the performance of CSP plants are DNI, wind speed, cloud and temperature. How do these factors affect the CSP plants? ” At the 3rd Delingha CSP conference,Jin Jianxiang, chairman of Zhejiang SUPCON Solar Technology Co.,Ltd. explain the problem with Four Q&As.

Q1, DNI will drop by 100kWh/㎡a, will the LECO increase by 4.5%?

(1) For CSP plants, when DNI is around 2000 kWh/㎡a, DNI is 100 kWh/㎡a (5%) lower than design, LCOE will increase by 4.5%;

(2) In fact, after the design optimization, 5%lower of DNI can be increased by 5% of solar field. The total cost will only increase by 2.5%, and the LCOE will only increase by 2.25%, not 4.5%.

(3) the influence of the reflectivity of the heliostat on the Economic analysis is similar.

Q2, what is the effect of wind speed on the efficiency and cost of molten salt tower CSP station?

(1) Strong wind increases the convective heat dissipation of the heat absorber; each increase in wind speed of 3 m/s, the efficiency of heat absorber decreases by about 2.1%.

(2) Strong wind increases the oscillation of heliostat and decreases the tracking accuracy, resulting in a decrease in the truncation efficiency; when wind speed at 12m/s ,truncation efficiency decreases by 4.5%, at 15m/s, truncation efficiency decreases by 13.3%.

(3) other influences:

Beyond the working wind speed, heliostat will enter the protection state and increase the idle capacity of solar.Or to increase the amount of steel used for heliostat and torque and rigidity of the drive system, which increased the costs.

Therefore, the excessive wind speed has great influence on efficiency and cost, and can’t be ignored.

Q3. How does the cloud affect the efficiency of molten salt tower CSP station and life of the absorber?

(1) Cloudy days, frequent startup and shutdown of the absorber, idle capacity of solar increase due to preheating and gap; as shown below, the idle capacity rate of solar is 28% in cloudy days, while only 3% in sunny days.

(2) the accuracy of power generation estimation decreased in cloudy weather.

(3) Complex operating conditions in cloudy weather makes standardize operation strategies harder to achieve and mistakes increased.

(4) Rapidly change of DNI leads to drastic changes in the surface temperature of the absorber, which affects the life of the absorber, increases the failure rate of the equipment.

Therefore, cloud is an important factor affecting the equipment life, idle capacity of solar and electricity generation.

Q4. How does ambient temperature affect the efficiency of molten salt tower CSP plant? Answer:

(1) The ambient temperature reduced by 20℃, the efficiency of the heat absorber is decreased by 0.3%; the temperature increased by 20℃, the efficiency of the heat absorber is increased by 0.06%.

(2) the ambient temperature increased from 13.5℃ to 26.5℃, and the turbine efficiency is reduced by 3%.

Other influences:
The reduction of ambient temperature will increase the heat dissipation of pipe, the pipe heat dissipation of tower CSP station is far less than the parabolic trough CSP station.

When the ambient temperature decreases by 20 C, the heat dissipation of the cold tank increases by about 7%, the heat dissipation of the hot tank increases by 3.5%, assume the daily heat dissipation of the hot &cold tank is 1% of the total energy storage, the increase of the total heat dissipation is only 0.05%, which can be neglected.

In short, the lowering of ambient temperature does have a negative impact on heat absorber, pipeline heat dissipation, salt tank heat dissipation, but the impact is very small. on the contrary, it is conducive to obviously improving the efficiency of steam turbines; but when the ambient temperature drop to below 0℃, water can’t be used to clean the mirror, which will affect the mirror cleanliness and Reflection efficiency.

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