Rising up from the countryside in Zhangbei county, 260km to the northwest of Beijing is a unique CSP plant. With 170,000㎡Fresnel solar field, 720MWh(th) concrete TES system and 15MWe steam turbine system, it wows people all over the Chinese CSP industry.
Huaqiang TeraSolar I 15MW CSP Plant is developed by Beijing TeraSolar Photothermal Technologies Co., Ltd. (hereby referred to as TeraSolar). By the end of 2017, it was basically completed, standing out as a notable milestone.
The project’s most distinctive feature is the new kind of proprietary Fresnel CSP technology originated by TeraSolar. It’s a global pioneer in the world andwill have asignificant impact on the future CSP industry.
It’s known that several innovative technologies have been used, such as cold-curved double glass mirror structure created by TeraSolar, inclined Fresnel-like high-concentration ratio solar field, low-cost large-scale formula concrete TES system, integrated land use plan, automatic rainwater collection system, and high-frequency automatic mirror-cleaning technology.
With proven technology and economic effectiveness, the project has taken all the special problems in China into consideration and offered unique solutions. More notably, the whole technology system is based on the goal of achieving grid parity.
Image: Huaqiang TeraSolar I 15MW CSP Plant
An Innovation in CSP Technology
Since 1980 when the commercialization of CSP plant was first achieved in the U.S., the mainstream technology has been limited in parabolic trough and tower type with synthetic oil and molten salt as the only two heat transfer fluids. For 30 years, all innovationshaven’t detached from the mainstream technology, and revolutionary breakthroughs, such as supercritical CO2 cycle, are still only theoretical.
Huaqiang TeraSolar I 15MW CSP Plant, however, is a radical innovation in CSP technology.
It adopts Direct Steam Generation(DSG) technology system. There are several benefits if the water/steam can be used for heat transfer fluid. Firstly, there is no need for oil-water heat exchangers if water is directly evaporated and superheated in thesolar field, resulting in a simpler plant configuration and lower investment costs. Secondly, the use ofwater is eco-friendly: compared to oil, water is cheaper, non-toxic and non-flammable;compared to molten salt, water is less expensive and less corrosive.
HLIACS Solar field—Several Advantages are Rolled into One
In the sunlight, the 170,000㎡new kind of Fresnel solar field of TeraSolar I is magnificent. Differing from parabolic trough and traditional Fresnel, it shows a unique layout of east-west inclined arrays, called HLIACS.
When solar field shows a north-south horizontal linear layout, the cosine effect difference between summer and winter is significant and would cause the former gets much more solar radiation than the latter. But HLIACS, with a layout of east-west inclined arrays, overcomes the problems above. It is well suited for China where DNI resource is abundantin intensely cold high latitudes.
Image: Diagram of Monthly Accumulated Heatof Different Types of CSP Technology
According to TeraSolar, without considering heat loss, the total yearly accumulated heat of north-south parabolic trough is 794kWh/㎡, while the HLIACS is 786kWh/㎡. There is only 1% difference between them. But HLIACS’s monthly accumulated heat is evenly distributed, and distinctly exceeds two other technology types, especially in winter.
On the other hand, the total yearly accumulated heat of north-south Fresnel is only608kWh/㎡, which is far less than the former two，andits accumulated heat is even less than half of HLIACS‘s during several months in winter.
The First Commercialization of Concrete ThermalEnergy Storage System
For a long time, many research institutes and enterprises have been experimenting on concrete thermal energy storage(TES) system. But there is no commercialization of the technology until the TeraSolar I was completed.
Another innovation of the project is the 14h formula concrete TES system. The system has a maximum thermal capacity of 720MWh(th), design pressure of 16MPa, and design operating temperature of 450℃(a maximum of 550℃).
Image: Concrete TES System under Construction
Image: Concrete TES Storage System Completed
The concrete TES system is developed and constructed by TeraSolar, which is also the patent owner of the technology. It combines the function of heat transferring/storing and steam generating. High-temperature steam produced by solar collecting system goes directly into the TES system to transfer heat for storage ,and water is pumped into it to generate high-temperature steam for heat releasing.
Patented formula concrete used in the TES system boasts various advantages, including high thermal conductivity, high specific heat capacity, high density, ideal expansion factor, and high strength sustaining operating throughout the year. Besides, materials can be pumpable to achieve high efficiency during construction. After years of experiments and verification of third-partyauthoritative organization, the formula concrete can meet the standards of TES system in CSP plant, and its application will be expanded to other TES-related industries.
The common view of the CSP industry is that the biggest problem ofconcrete TES technology is low heat-transfer efficiency. Through years of efforts, TeraSolar has solved the problem with strengthened heat-transfer structure which is stable, economic, durable and suitable for mass production.
In CSP industry, as a heat transfer fluid, water has been long ignored, but TeraSolar chose water. Similarly, molten salt is the most popular TES medium, but TeraSolar chose concrete. Water and concrete, two readily available and low-cost materials, built up TeraSolar’s unique CSP technology system.
Differing from some air-castle innovations, TeraSolar’s CSP technology system is based on continuing research and all-dimensional performance verification. Since 2016, it has evolved from theory to preliminary and mid-term experiments. Finally, commercialization of the 15MW CSP plant was achieved.