Frensel Lens Stirling Engine

[etodds]

I have heard of companies developing stirling engines using a
parabolic mirrors to solar power stirling engines. Has anyone heard
of research using Frensel Lenses? I would think you could get a
smaller footprint design with this method.

[rtopf]

Todd,

The commercial developments I am aware of are 10-25 Kw parabolic dish systems that use dishes 8 or more meters in diameter. They are usually made up of smaller facets arranged on a metal frame. This way, each facet is relatively thin. The focal point is in front of the mirrors, so the structure does not block the sunlight.

A Fresnel lens would need to be of similar diameter. It would be very difficult to support a thin lens of this size without obscuring much of the light.

Rick

[dbarnettaz]

Back in school we built a solar metal cutter using Fresnel lenses. A problem arises when you try to go too large with such a lens because the incoming light must be perpendicular to the plane of the lens. With some of the high-powered units being the ultimate goal (25 kW & up) getting the concentration ratio of the concentrator to be in the range of g.t. 2000:1 is problematic with most Fresnel lenses. The parabolic concentrators used now at Sandia are fairly long focal length jobs. The Fresnel lenses are not long focal length, and as such getting a lot of them on target will be an issue.
Don

[moreshkokane]

We at NewPower India have developed a technique to manufacture large
Fresnel concentrators. There are number of Optical challenges involved,
which cause issues in this design. Try doing a google for nonoptical
fresnel solar thermal collectors. Number of research papers by a
Japanese guy which explains in detail the issues involved.