Would It Work? Concept for fixed installation: Using Focal Mirrors

[EclecticBadger]

One of the cost factors to take into account with any solar installation involves cabling between the panels and either where the power is to be used and/or the battery storage bank.

My question for the forum, could long cable runs be substituted by using mirrors to focus sunlight on to a panel. The panel itself could even be installed on a shaded wall, but would be illuminated by focused and redirected sunlight. I have considered that heat would be a factor and am aware that middle east countries employ banks of mirrors focussed on to a central tower as a means of creating steam to power generators. But would this work for PV?

This is purely a thought experiment at this stage, but I would love to read other's opinion, whether that be with links or comment on 'pie in the sky'.

Cheers.

 

[SolarRat]

Focused hot-spots would likely hurt the panel. But maybe with a convex mirror? Or shaped mylar panels? You'd have to get a perfectly even spread of light. Anyway, any cost factors or cable losses of doing it normally would be negligible compared to the loss/danger/cost of using mirrors.

I had thought of using mirrors/mylar to redirect the sun onto flat mounted panels in the early am or late in the day...but only a quick thought.

 

[svetz]

The problem probably isn't in the reflection, it's in the apparatus to keep the reflected focal area (not point) on the solar panels and keep them clean. Someone's probably done a study on it. I know people use heliostats to keep rooms warm in winter.

Will's done a video on this, but I believe the point there was that it works, but not worthwhile. A part of that is a regular mirror is fine for reflecting visible wavelengths. But panels absorb wavelengths beyond that as illustrated below.

3M makes some films that are more reflective than silver-backed-glass. Although you might need multiple reflective surfaces tuned to capture different wavelengths and redirect their energy. By making the reflective area greater than that of the panels area you can concentrate more light to overcome both reflective inefficiencies and even more important atmospheric absorption (graph below), thus freeing you from the tyranny of the insolation maps that even 2 axis trackers suffer:

Keeping your Panels Cool
I believe heat is conducted in all the wavelengths a typical solar panel uses, but it might be that by selectively tuning out some wavelengths the panel could be kept cooler. It just depends as to whether there are any wavelengths (and their harmonics) the panel is particularly adept at converting into heat rather then electricity.

 

[svetz]

I wonder if you could take advantage of the analemma shape and create some sort of non-moving reflector "shape" whose job it was to always keep reflected sunlight on your panels throughout the day over the entire year. Doubt many HOAs would approve it. Or perhaps there's a configuration like the retroreflectors that were taken to the moon?

 

[MrNatural22]

Here’s some research on that topic

Can mirrors boost solar panel output - and help overcome Trump’s tariffs?

Raising the cost of solar panels coming to the US could rekindle interest in a simple but potentially significant technology: solar reflectors.

theconversation.com

 

[EclecticBadger]

I wonder if you could take advantage of the analemma shape and create some sort of non-moving reflector "shape" whose job it was to always keep reflected sunlight on your panels throughout the day over the entire year.

That would be some interesting math to calculate the precise shape. Subsequent 3D printing of the model and reflective foil vacuum-forming would be easy by comparison.

 

[EclecticBadger]

Here’s some research on that topic

Can mirrors boost solar panel output - and help overcome Trump’s tariffs?

Raising the cost of solar panels coming to the US could rekindle interest in a simple but potentially significant technology: solar reflectors.

theconversation.com

Good article.

 

[svetz]

I was looking into @SolarRat's idea about mylar, those space blankets are not only super cheap but pretty amazing (even protection from EMF). Basically they're mylar film with an aluminum coating. The table below a variety of reflective coatings for telescope mirrors, but this ref says you can coat mylar with UV enhance aluminum, so that would 80-90% reflectivity. I've seen greenhouse films around 94%, but they only show visible light spectrums.

​

 

[offgriddle]

Preposterous. https://www.extremetech.com/extreme...death-ray-thats-incinerating-birds-mid-flight

 

[svetz]

Preposterous. https://www.extremetech.com/extreme...death-ray-thats-incinerating-birds-mid-flight

Are you saying their goose is cooked?

 

[offgriddle]

Are you saying their goose is cooked?

It would appear so!