Concentrated solar power (CSP) systems are known to be the most efficient solar power generating means. This is because CSP systems comprise of numerous rotating mirrors that track the sun. This ensures that all reflected light is concentrated onto a single receiver, which in turn minimizes the impact from fluctuations in strength of sunlight.
Power plants that use CSP can benefit from one other advantage- thermal energy. If that is stored, energy production can continue at night or on cloudy days.
Unfortunately, all great things have their price, and when it comes to CSP, that price is much higher than that of conventional solar.
Now, the great minds over at Mitsubishi Hitachi Power Systems (MHPS) developed a hybrid system that aims to make CSP cheaper, by integrating a low-cost, low-temperature Fresnel evaporator. This technology is currently being tested in a large facility, which is spread over 10,000 sq m. It has 150 mirrors, one evaporator and one superheater, which is built into a tower. Around 70% of the sunlight that reaches the plant is pulled to the evaporator. It then uses the thermal energy to produce steam with temperature of 300 degrees C (572 F).
From here, the steam is transferred to the top of the tower, where the superheater is located. Using the concentrated sunlight, the temperature of the steam is further increased to 550 degrees C (1,022 F).
The reduction in price comes from the fact that the steam is already pre-heated before it reaches the top of the tower. This means that fewer mirrors are required to bring the steam to the maximum temperature.
According to MHPS, this new hybrid system can generate 300 kW of electricity for a fraction of the cost.
The test facility is operating under the Ministry of Environment of Japan. The test phase will continue until March 2017. By then, MHPS are hoping to demonstrate the great improvement that their invention can bring. In October this year, they also plan to begin testing a high-temperature thermal energy storage system, which should replace the polluting back-up fossil fuel operated systems.
Image (C) MHPS