Solar Heat Pipe Research Articles

Solar chemical heat pipe in closed loop operation: mathematical model and experiments

A computer model was developed for closed loop operation of a solar chemical heat pipe, to include both the endothermic methane reforming and the exothermic methanation of synthesis gas. The modeling results showed reasonably good agreement with experiments. The model can be used for design of larger systems as well as other chemical heat pipes.

Oil-shale gasification by concentrated sunlight: An open-loop solar chemical heat pipe

Gasification of oil shales followed by catalytic reforming can yield synthesis gas, which is easily transportable and may also be used for producing liquid fuels. We report here on experiments performed at the Weizmann Institute's Solar Central Receiver involving the use of concentrated solar energy as the heat source for the gasification. A number of dual-axis tracking heliostat mirrors provided primary concentration, and compound parabolic concentrators (CPCs) were used for secondary concentration. In addition to being the first experimental study on this particular type of chemical storage of concentrated sunlight, new aspects of this work include demonstrations of the following: 1. (i)significantly higher synthesis gas yields than previously reported; 2. (ii) marked improvements in conversion efficiency in transparent reactors, as opposed to opaque reactors, both as fluidized beds, primarily due to better heat transfer; 3. (iii) a substantial increase in deliverable energy compared to the conventional retorting of oil shales, and considerable reduction in the resulting spent shale.

Methanation of synthesis gas in a solar chemical heat pipe

The reversible reaction CH 4 + CO 2 = 2 H 2 + 2 CO is under investigation as a chemical heat pipe for storage and transport of solar energy. In this paper, the study of the back exothermic reaction, the methanation of CO-rich synthesis gas, is reported. Three different methanators were constructed and operated in a closed-loop, with the reforming products from the reaction carried out in the solar furnace. The best performance was obtained with a six-stage adiabatic methanator. The experimental results are compared with computer calculations, assuming equilibrium at each stage. The agreement between experimental and calculated results is satisfactory. Scale-up work on a 400 kW unit is in progress.

Chemical reactions in a solar furnace 2: Direct heating of a vertical reactor in an insulated receiver. Experiments and computer simulations

The performance of a solar chemical heat pipe was studied using CO 2 reforming of methane as the endothermic reaction. A directly heated vertical reactor, packed with a rhodium catalyst was used. The solar tests were carried out in the Schaeffer solar furnace of the Weizmann Institute of Science. The power absorbed was up to 6.3 KW, the maximal flow rates of the gases reached 11,000 1/h, and the methane conversions reached 85%. A computer model was developed to simulate the process. Agreement of the calculations with the experimental results was quite satisfactory.

Closed-loop operation of a solar chemical heat pipe at the Weizmann Institute solar furnace

The performance of a solar chemical heat pipe was studied using CO 2 reforming of methane as the vehicle for storage and transport of solar energy. The endothermic reforming reaction was carried out in an Inconel reactor, packed with a rhodium catalyst. The reactor was suspended in an insulated ☐ receiver which was placed in the focal plane of the Schaeffer Solar Furnace of the Weizmann Institute of Science. The exothermic methanation reaction was run in a tubular reactor filled with the same Rh catalyst and fed with the products from the reformer. Conversions of over 80% were achieved for both reactions. In the closed-loop mode the products from the reformer and from the methanator were compressed into separate storage tanks. The two reactions were run consecutively and the whole process was repeated for nine cycles. The overall performance of the closed loop was according to expectations.