have proposed a fluid flow layout to improve the heat transfer in the active absorber surface of solar central cavity receivers. The proposed design is conformed to the solar image symmetry on the absorber surface. Thus, the global HTF mass flow is divided in as many circuits as quasi-symmetrical regions can be defined on the absorber surface. In this way, more uniform temperatures are achieved at the outlet of all the circuits, reducing mixing irreversibilities. Sahoo et al. [24] have investigated the heat loss due to radiation and steady laminar natural convection flow in a trapezoidal cavity having eight absorber tubes for a Linear Fresnel Reflector (LFR) solar thermal system with uniformly heated tubes and adiabatic top wall. It has been observed that the dominant mode of heat losses from the cavity is radiation. They have proposed to use a selective coating on tubes and cavity inside wall in order to reduce the overall losses. Although the dominant mode of losses is radiation, the losses by natural convection are also significant. Therefore, Sahoo et al. [24] have recommended the use of evacuated cavities to minimize convection losses. Garcia et al. [25] have listed the different codes for solar flux calculation
dedicated to central receiver system (CRS) applications. Their study has permitted them to classify the calculation codes into two categories, corresponding to two types of problems encountered in studies on CSP technologies: the first category is about the optimization
codes used to design installation projects such as HFLCAL, UHC-RCELL, or (WIN) DELSOL and the second one represents the performance analysis codes to assess optical performances of a
given installation like FIAT LUX, MIRVAL, UHC-NS or IH, or SOLTRACE. Buck et al. [26] have proposed a new dual-receiver concept for solar towers, using the open volumetric receiver technology. The results have shown several benefits of the new concept, especially higher thermal efficiency of the receiver, lower receiver temperature and lower parasitic losses. Wei et al. [27] have developed a new computing code, based on new method, for the design of heliostat field layout (HFLD) for solar tower power plant. In the new method, the field boundary is constrained by the receiver geometrical aperture and an efficiency factor.