Background
Evacuated-tube solar collectors, in conjunction with non-tracking, non-imaging parabolic concentrators, can heat working fluids to 200°C at efficiencies near 50%, providing a relatively economical means for capturing and transferring solar energy for use in cooling, heating, and power generation applications.
However, the transfer of heat from the solar energy-absorbing element to the working fluid within such collectors poses a significant challenge to the feasibility of these systems. It is a critical limitation of existing evacuated-tube collector designs because of trade-offs between resistance to heat transfer, cost, and safety.
A scientist at the University of California, Merced has recently invented an improved evacuated-tube solar collector design that incorporates mini-channels for circulating the working fluid in the absorber element.
While mini-channel technology helps overcome the limitation described above, a serious engineering problem remains in optimizing the coupling between the absorber mini-channels and the connecting manifolds. These manifolds, which enable the flow of the working fluid to and from the mini-channels, must connect to pipes that are much larger and possibly a very different shape than the mini-channels. Inlet-outlet manifolds that are suitable for this application currently are not commercially available.
Description
A UC Merced scientist has invented several manifold designs for mini-channel-based absorbers, including absorbers containing flat-plate and semi-circular arrays of mini-channels. Variations of these manifold designs include manifolds with separate inlet and outlet sections, and also featuring an end cap where the fluids from different mini-channels can mix and flow back to the manifold through a separate tube or a shallow slit on the surface of a mini-channel containing pipe. The manifold can also assume several different forms, including drums or semi-circular tube arrays.
Applications
The UC Merced input-output manifolds are necessary for implementing evacuated tube solar collector designs based on mini-channels, which could help realize the great potential of mini-channels for making such solar collectors commercially feasible.
Advantages
At present, this invention is the only technology that addresses the specific need for enabling the flow of working fluids into and out of mini-channels in solar collector absorber elements.
Patent Status
Patent Pending
Inventor
Gerardo Diaz
