Thermal or Photo voltaic energy?

[camerart]

Hi,
Has anyone got experience with comparing the energy from Thermal and Photo voltaic panels?

From what I've read thermal panels don't get enough heat to get the most energy from them.
My main quetion is: If instead of having 'say' a 1mtr panel, instead there is a 1mtr magnifiying lens, that concentrates the heat into a smaller panel, so it gets hotter.

I was also wondering if a liquid other than water could be used, with a lower boiling point, where boiling expansion could be converted to energy better?
Cheers, Camerart

 

[^woody^]

Doesn't one produce electricity and the other hot water?

 

[ajstoneservices]

You can get a hybrid panel that does both.

edit: Hybrid solar panels

 

[oldbutnotdead]

Google is your friend, look for evacuated thermal solar panels.
Back In the 70s there were a load of chancers flogging solar panels to preheat heating/dhw- all they did was throw cheap radiators painted black on the roof. Yes there was some heat gain but not a useful amount.
Modern thermal solar panels do focus a reasonable area of sun capture onto a smallish volume of water thus giving a useful max temperature. Of course you have the cost of running a pump to think about....
Solar PV is a bit less efficient in theory (losses through inverter, expensive hardware) but may make up that loss through convenience and usefulness.

 

[^woody^]

So when you need the heating most in winter, on cloudy days, do the Thermal tubes/ET provide enough energy? Or even a tank of hot water for a bath?

 

[ajstoneservices]

Most of us wash all year round. After a hard days work in the summer is when they are needed the most.

 

[camerart]

Hi,
Thanks for your replies, but none of you answered my particular questions!

I wanted to know if there is anyone who has got experience of comparing the energy for both of these types of panels.

Having already read that the output of thermals panels (These produce hot water) is not high, I want to know if there could be a lens that focuses the same area of the existing panel, to a smaller panel, so generating more heat that could be useful.
C

 

[ajstoneservices]

There is nothing new under the sun. Fresnel lens, thermal oils and salts have been used. What you have read about solar panels may or may not be correct. Many people with no experience of solar thermal or photovoltaic panels write the most about them.

 

[oldbutnotdead]

Hi,
Thanks for your replies, but none of you answered my particular questions!

I wanted to know if there is anyone who has got experience of comparing the energy for both of these types of panels.

Having already read that the output of thermals panels (These produce hot water) is not high, I want to know if there could be a lens that focuses the same area of the existing panel, to a smaller panel, so generating more heat that could be useful.
C

No experience apart from basic physics. Of course there could be a lens (did you never torture ants with a magnifying glass when you were young or is that a Boomer thing) but you'd need lots of small lenses or one massive one. Solar energy capture is about square metres- if you have 10 sq m of panel you'll get 10 times the energy of 1 sq m of panel. So focus your 10 sq m of lens onto a 1 sq m of panel and you'll get some heat, but payback might be a way down the road and (crucially here) 1 sq m of lens will not capture 10 sq m-worth of energy.

 

[SFK]

lens that focuses the same area of the existing panel, to a smaller panel, so generating more heat that could be useful

No not currently.

These is some reasearch to put micro lenes on the glass to collect more non direct sunlight (ie mornings and evenings). But currently puts costs of panel up by more than simply buying more panels.

Your suggested method would need lenses a distance from the panels - which would be a structral issue. And also lenses collate the light so makes the panels less effecient at collecting evening and morning light. Again simpler and likley cheaper to get more panels.

 

[SFK]

So focus your 10 sq m of lens onto a 1 sq m of panel and you'll get some heat, but payback might be a way down the road and (crucially here) 1 sq m of lens will not capture 10 sq m-worth of energy.

Of course some do this on a big style (Gemasolar Thermosolar Plant, Spain) :>
But they are melting salt to store the heat to drive a turbine so not applicable to home use.

https://en.wikipedia.org/wiki/Gemasolar_Thermosolar_Plant

 

[SFK]

experience of comparing the energy for both of these types of panels

Unfortunatly not seen this done openly.

And I feel is sometime comes down to what system yo have. Id you have a south facing roof, and a large hot water tank system, and easy plumbing between the two, then 'Solar Evacuated Tube Collector' systems can work well.
They are frequently used in more southern countries such as Greece.
https://www.google.com/search?q=Solar+Evacuated+Tube+Collectors+roof

But as 'Solar Evacuated Tube Collector' installers are low in the ground here in UK (and many have gas supply to the home ), then the focus seems to be on PV here in UK.

But I relealise that that is not a deffinative answer that yiou are looking for.

 

[camerart]

Of course some do this on a big style (Gemasolar Thermosolar Plant, Spain) :>
But they are melting salt to store the heat to drive a turbine so not applicable to home use.

View attachment 266435
https://en.wikipedia.org/wiki/Gemasolar_Thermosolar_Plant

Hi S,
Nice, but I'll need a bigger garden.
C

 

[camerart]

No experience apart from basic physics. Of course there could be a lens (did you never torture ants with a magnifying glass when you were young or is that a Boomer thing) but you'd need lots of small lenses or one massive one. Solar energy capture is about square metres- if you have 10 sq m of panel you'll get 10 times the energy of 1 sq m of panel. So focus your 10 sq m of lens onto a 1 sq m of panel and you'll get some heat, but payback might be a way down the road and (crucially here) 1 sq m of lens will not capture 10 sq m-worth of energy.

Hi O,
Yes, sorry ants!
C.

 

[camerart]

Hi,
I have PV solar panels on my van, so I can check the output here.

I also have a similar sized Fresnel lens, plus a computer radiator, app 100x100mm. I had a quick try once, but I ran out of self imposed time, to get anything meaningfull.

If I thought it would be worth it, I'd have another go. I suppose first I would fill it with water, and see how hot it got. I think it would boil if sunny, so I would need a temperature controlled pump.
It could of course be filled with another lower boiling point liquid, but I think that would need a bit more care.

Then comes the question of storage, there used to be storage heaters, but a tank in the ground would do.

It would need move and follow the light.
C