Abstract
High temperature solar receivers are developed in the context of the Gen3 solar thermal power plants, in order to power high efficiency heat-to-electricity cycles. Since particle technology collects and stores high temperature solar heat, CNRS (French National Center for Scientific Research) develops an original technology using fluidized particles as HTF (heat transfer fluid). The targeted particle temperature is around 750 °C, and the walls of the receiver tubes, reach high working temperatures, which impose the design of a cavity receiver to limit the radiative losses. Therefore, the objective of this work is to explore the cavity shape effect on the absorber performances. Geometrical parameters are defined to parametrize the design. The size and shape of the cavity, the aperture-to-absorber distance and its tilt angle. A thermal model of a 50 MW hemi-cylindrical tubular receiver, closed by refractory panels, is developed, which accounts for radiation and convection losses. Parameter ranges that reach a thermal efficiency of at least 85% are explored. This sensitivity analysis allows the definition of cavity shape and dimensions to reach the targeted efficiency. For an aperture-to-absorber distance of 9 m, the 85% efficiency is obtained for aperture areas equal or less than 20 m2 and 25 m2 for high, and low convection losses, respectively.
Highlights
Among the various concentrating solar technologies, central receiver (CR) point focusing systems offer a wide range of options, in term of power, working temperature, storage capacity and, as a consequence, conversion efficiency
Tubular receivers are operated in all the commercial solar thermal power plants even if other options as porous receivers have been developed at pilot scale [1]
The results indicated that convection losses decrease strongly with the inclination angle of the cavity for all the receiver shapes
Summary
Among the various concentrating solar technologies, central receiver (CR) point focusing systems (or solar power tower, SPT) offer a wide range of options, in term of power, working temperature, storage capacity and, as a consequence, conversion efficiency. Getting higher efficiencies (~50% and more) is possible at 700–750 ◦ C with supercritical carbon dioxide (sCO2 ) cycles [2] and at approximately 850 ◦ C with combined cycles [3] Such high operating temperatures result in great challenges on the solar receiver design, construction materials and heat transfer fluids. Study of the combined natural convection and radiation heat losses of downward facing cavity receivers of different shapes was presented in [7], in the temperature range 250–650 ◦ C. For cavity receivers at 900 ◦ C the ratio of radiation to convection losses ranged between 2 and 7 except with head-on high wind condition (10 m/s) that resulted in a ratio approximately equal to one [12]. Other specific constraints are justified by previous results and general consideration as explained below
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