The Required Concentration Ratio for Two Stage Water/Steam Cavity Receiver

The pioneering water/steam cavity receiver CESA-1 is not very successful for that the evaporator and superheater are in the same cavity cause it is very difficult to control the heat flux distribution on the absorber surface and hence the flow stability inside the receiver.The two-stage water/steam receiver is a promising way for separating the evaporator and superheater in two different cavities or parts. Because the two different parts have different thermal performance, the required concentration ratio(CR) of per heliostat projected two different parts will be different. Based on the transient efficiency equation and existed DAHAN solar tower power plant, the paper research the influence principle of many factors such as receiver thermal performance,superheater operation capacity, heliostat size and numbers of heliostats projected to the absorber. The results show that the required CR of per heliostat for superheat part is decreasing with the superheater thermal performance improving. When the receiver operates in lower capacity, the required CR of per heliostat is lower. With more heliostats project to the superheater, the required CR of per heliostat becomes lower. The smaller heliostat size, the lower required CR of per heliostat. The results also give us some inspirations that: 1) using the method in the paper, one can evaluate whether the existing heliostat field is fit for the two-stage receiver. 2)two stage receiver capacity and heliostat size should be in harmony for different CR requirement for evaporator and superheater.3) the results about how the heliostat size influences the required CR of per heliostat for superheater give the reference to industrial choose of heliostat size. 4)from the required CR point, the smaller heliostat is better than bigger one. Of course, in the real commercialization process, the cost of the heliostat should also be considered.