[Camerart (OP)]

Hi,
I would like to know, if anyone has got experience with thermals solar panels, with lenses focused on them?

I have tried a quick experiment, and my 1/2mtr square Fresnel lens plus a 100mm square computer radiator, produced a lot of heat.

I couldn't spend much time on this, and I wonder if different liquids, that perhaps boil, plus maybe heat pumps could be used.

Would this type of settup compare with PV panels?
Cheers, Camerart

[vhfpmr]

What do you want, heat or electricity? Generating electricity to produce heat is not efficient, solar PV is far less efficient than thermal solar. The most efficient panels are the hybrid ones, which generate both heat and electricity.

[Camerart (OP)]

What do you want, heat or electricity? Generating electricity to produce heat is not efficient, solar PV is far less efficient than thermal solar. The most efficient panels are the hybrid ones, which generate both heat and electricity.

Hi V,
Heat or electricity, whatever is best after testing the project.

I'm interested about getting the most of thermal panels, then compare them to PV panels.

Have you considered my suggestion of a light focusing lens in front of the panel?  The lens being the same area of the PV panel.
C

[vhfpmr]

I don't see any point in a lens the same size as the panel when the purpose of the lens is to focus light into a smaller area than its own. Are standard panels designed to withstand light at a higher power density than naked sunlight without damage?

[Camerart (OP)]

I don't see any point in a lens the same size as the panel when the purpose of the lens is to focus light into a smaller area than its own. Are standard panels designed to withstand light at a higher power density than naked sunlight without damage?

Hi V,
Have you heard the terms low quality and high quality heat?
Warm water has low quality heat, so there's not much energy in it.  Boiling water is high quality heat, and can run a steam engine.
The purpose of the lens is to concentrate the light into a smaller area, which gives higher quality heat, and can be more useful.
C

[Bored chemist]

The purpose of the lens is to concentrate the light into a smaller area

The lens being the same area of the PV panel.

You can't "concentrate" something into the same size.

[alancalverd]

Concentrating sunlight with a lens is an entirely reasonable means of generating high temperatures. There are solar boilers and furnaces around though they generally use an array of mirrors rather than a lens to generate industrially useful quantities of heat - it's more robust  and easier to construct on a very large scale. Nevertheless a Fresnel lens seems like a good choice at the scale of a meter or less.

Given that practically all of the sunlight can be converted to heat, but only about 10% to electricity, solar heating is far more efficient than photovoltaics,whether you want to heat a house or cook with it. The advantage of a concentrator is that it gives you a choice, whereas a flat panel heater will only generate low temperature water in the UK - OK for underfloor heating but little else..   

[Camerart (OP)]

Concentrating sunlight with a lens is an entirely reasonable means of generating high temperatures. There are solar boilers and furnaces around though they generally use an array of mirrors rather than a lens to generate industrially useful quantities of heat - it's more robust  and easier to construct on a very large scale. Nevertheless a Fresnel lens seems like a good choice at the scale of a meter or less.

Given that practically all of the sunlight can be converted to heat, but only about 10% to electricity, solar heating is far more efficient than photovoltaics,whether you want to heat a house or cook with it. The advantage of a concentrator is that it gives you a choice, whereas a flat panel heater will only generate low temperature water in the UK - OK for underfloor heating but little else..   

Hi A,
Good!  It does seem interesting, and worth an experiment.

I have PV panels on my van (110W), and have experience of cloudy days, when the sun is low.  Bearing in mind that the van top is parallel, so not aiming at the light, and and I think I got about 200W.

Regarding efficiency: PV panels, are improving all of the time.  Have you heard of the later double layer type?

I think I'll try water first, and see what I get.  It will take some time to set up, as I need a temperature controlled pump, and a following mechanism.
c

[evan_au]

an array of mirrors

I imagine that you could lose a few drones while making a video like this...

[Bored chemist]

Lenses and mirrors are cheap . PV cells are expensive.
Focussing light onto small cells with big optics makes sense in some cases. (for example, where the Sun's light is weak)
It might be an idea to put a filter in place to block IR.
For extra kudos, take the heat from the IR blocking filters + use it to provide low grade heat while still harvesting high grade energy, directly as electricity.

[Camerart (OP)]

Lenses and mirrors are cheap . PV cells are expensive.
Focussing light onto small cells with big optics makes sense in some cases. (for example, where the Sun's light is weak)
It might be an idea to put a filter in place to block IR.
For extra kudos, take the heat from the IR blocking filters + use it to provide low grade heat while still harvesting high grade energy, directly as electricity.

Hi B,
Hi B,
Can you tell me the reason for the IR filters, please?

I was more thinking about focusing the light onto a thermal radiator (Liquid filled)  then extracting the heat with a pump and converting it to higher level heat.
C

[Bored chemist]

Photovoltaic cells don't work well when overheated.

[evan_au]

One problem with a Fresnel lens (or mirrors) is that you need some mechanism & computers to ensure the concentrator follows the Sun accurately (otherwise the "concentrator" actually reduces the amount of sunlight reaching the collector).

Solar panel losses increase with temperature, so systems that use a concentrator also need a cooling system to keep the solar cell cool, eg by running cold water behind the photovoltaic cell.

DARPA (US military research) launched the Very High Efficiency Solar Cell (VHESC) project to develop portable and highly efficient solar panels, aiming at > 50% efficiency. Various concentrators were used. Here is a report on the early results.
https://www.nxtbook.com/nxtbooks/ieee/spectrum_na_0912/index.php?startid=50#/p/50

[Camerart (OP)]

Hi,
Let me clarify:
When I mention the cells on my van, that I can compare with, I'm talking about the PV type.

Here, I'm asking about heating liquid in a radiator, that is being heated by concentrated sunlight through a freznel lens the same size as a PV panel. 

As an example the liquid could be stored in an insulated tank for later use.

Melting salt etc is not something I'm likely to do, just simple liquid in a garden test.

Then I would like to compare it with heat generated from a PV cell, for comparison.

If anyone has experience with this kind of comparison or test, then I'm interested.
C