Why are Fresnel lenses not widely used in the production of solar electricity?

Question

Why are Fresnel lenses not commercially used in the production of steam to run a turbine and produce electricity?

Answer 1

This is built on, and directly quotes from, my answer and user26165's answer to a similar question over on Physics.SE.

No, fresnel lenses are not widely used for solar power. Occasionally, but rarely.

The issues are engineering and economics.

Other solar competitors

The big economic story is the amazing speed at which ordinary photovoltaics have reduced their unit costs. This means that the economics of all the competing solar technologies - trackers, concentrating PV, concentrating solar thermal electric, all have got much more to prove now.

The economic problem that comes from depending on direct rays

Concentrated solar power (CSP) that work by concentrating the sun on a heat-transfer fluid, to drive a turbine, depend on direct rays. Ordinary photovoltaics do not; they generate electricity from light however it comes in; reflected off snow, or scattered by the atmosphere and by clouds. And there's light like that all around the world (I've designed and sold PV systems for locations in Northern Europe, sub-tropics, Mount Everest, the tropics, and the South Pole).

Whereas if you need high-intensity direct rays for a lot of the year, you're pretty much confined to the tropics and near the tropics. And those are places where clean water is precious - and these sort of plants can be large consumers of clean water. These plants can be sited further away (and there are indeed concentrating solar power stations further from the equator), but then you've got an economic problem - it will be the same capital costs, but much lower generation to spread those costs over, so unit energy costs will be higher.

Maintenance challenges

As user26165's answer says:

Fresnel lenses are inherently single surface lenses; all of the optical power is on the serrated surface. The grooved structure of this surface is easily contaminated , needing frequent cleaning. They are expensive to make in glass, and most moldable optical plastics are UV degradable.

The surface contamination problem can be overcome by putting the grooved side on the inside, towards the focus. This is the worst possible way to use a single surface refracting lens; the lens aberration are extremely large, whereas they are not too bad, with the grooved side out.

The axial edges of the grooves scatter a lot of light, greatly reducing the transmission efficiency. You already have an 8-10% Fresnel reflection loss from the surfaces anyway, so Fresnel lenses are inefficient compared to reflector mirrors, and even with plastic molded lenses the costs are high. Numbers like 500 x concentration are not possible with linear (one directional trough) Fresnels, and even with rotationally symmetrical lenses, achieving 500 x is difficult because of the scattering from the non active edges of the grooves.

Answer 2

The very reason solar energy is exciting is that it is not scarce at all.

So, instead of making the best use of any photon, we use twice the surface area and cover it with cheap solar panels.

Pros

• Cheaper
• Higher output
• Better scalability
• Minimum need for structure. Otherwise, you need to elevate a very heavy lenses

Cons

• If you live in Monaco, you want to save each m²
• Less satisfying for engineers
• When each square meter on earth will have been used, we'll need to come to that