Combining PV with thermal

[zanghue]

Been thinking about building my own solar panel for quite some time and now have a real good excuse as I could also use it to heat the pool. Idea i am thinking of is similar to this one here only I want to also have pipes mounted underneath the panels for heating the pool.
is pretty straight forward as far as building one for electric, but I can not think of how I would build one that would also have the piping beneath it. The cells would need a substrate to be mounted on, but that would obviously cover up the pipes, which would defeat the purpose of the pool heater.

Moved from an unrelated thread....

[inetdog]

Been thinking about building my own solar panel for quite some time and now have a real good excuse as I could also use it to heat the pool. Idea i am thinking of is similar to this one here only I want to also have pipes mounted underneath the panels for heating the pool.
is pretty straight forward as far as building one for electric, but I can not think of how I would build one that would also have the piping beneath it. The cells would need a substrate to be mounted on, but that would obviously cover up the pipes, which would defeat the purpose of the pool heater.

If you really are talking about combining a Photo Voltaic (PV) panel to produce electricity with solar thermal piping to heat water directly, the concept just does not work out in practice. The PV wants to operate at as low a temperature as possible, and much of the light which does not produce electricity is reflected, with the rest converted to heat which goes equally out the top and bottom sides of the panel.
The solar thermal for domestic hot water (DHW) needs to be much hotter than a solar PV panel would be comfortable with. For pool heating you do not have that problem, but it is still far better to keep the PV and the thermal separate.

[SunEagle]

If you really are talking about combining a Photo Voltaic (PV) panel to produce electricity with solar thermal piping to heat water directly, the concept just does not work out in practice. The PV wants to operate at as low a temperature as possible, and much of the light which does not produce electricity is reflected, with the rest converted to heat which goes equally out the top and bottom sides of the panel.
The solar thermal for domestic hot water (DHW) needs to be much hotter than a solar PV panel would be comfortable with. For pool heating you do not have that problem, but it is still far better to keep the PV and the thermal separate.

I recently saw a hybrid solar panel that included both pv cells and tubing to run a fluid through which would transfer heat to a storage tank.

Not sure how well it works but some people are thinking along the lines of using the excess heat at the panel to be used to preheat water and the possibility of also cooling the pv panels to limit output loss due to heat.

[J.P.M.]

The idea of using excess heat in PV panels to heat water, and/or looked at from the other side - to cool the PV and increase efficiency of the PV - or both, makes a lot of sense on paper. The idea has been around since before PV became practical, and similar in logic to economizers and waste heat recovery logic. Two collector/applications for a bit more that the price of one and about the same footprint as one. What's not to like ? Seems almost like a no brainer.

That's sort of the logic I'd expect from what I call the "you could just" crowd. As in: " you could just do this and POOF - problem solved, I don't need to worry about the details - I'm an 'idea person' ".

At this time, the extra equipment and design effort needed to get decent heat transfer in a safe, workable and reliable way is a tough nut to crack in terms of the economics and practical hurdles.

Similar to most things, perhaps including some that seem deceptively obvious, the devil is in the details - something the "you could just" crowd is usually is ignorant of, or conveniently seems not to notice, often and IMO only, for the sake of getting into someone's wallet.

Safe, efficient, workable and cost effective heat transfer being to some degree one of the engineering black arts, most folks are unaware of the limitations.

As a practical matter, combined modes of solar energy utilization are more the province of DIY and graduate theses at this point.

[russ]

TThat's sort of the logic I'd expect from what I call the "you could just" crowd. As in: " you could just do this and POOF - problem solved, I don't need to worry about the details - I'm an 'idea person' ".

I had lots of those when I was working in India - most came from the bean counter area or the owners. One time the boss suggested we just shoot oxygen on the 700°C hot iron coming out of our furnaces - make liquid steel and bypass a lot of other costly steps.

[SunEagle]

The idea of using excess heat in PV panels to heat water, and/or looked at from the other side - to cool the PV and increase efficiency of the PV - or both, makes a lot of sense on paper. The idea has been around since before PV became practical, and similar in logic to economizers and waste heat recovery logic. Two collector/applications for a bit more that the price of one and about the same footprint as one. What's not to like ? Seems almost like a no brainer.

That's sort of the logic I'd expect from what I call the "you could just" crowd. As in: " you could just do this and POOF - problem solved, I don't need to worry about the details - I'm an 'idea person' ".

At this time, the extra equipment and design effort needed to get decent heat transfer in a safe, workable and reliable way is a tough nut to crack in terms of the economics and practical hurdles.

Similar to most things, perhaps including some that seem deceptively obvious, the devil is in the details - something the "you could just" crowd is usually is ignorant of, or conveniently seems not to notice, often and IMO only, for the sake of getting into someone's wallet.

Safe, efficient, workable and cost effective heat transfer being to some degree one of the engineering black arts, most folks are unaware of the limitations.

As a practical matter, combined modes of solar energy utilization are more the province of DIY and graduate theses at this point.

I agree with you. The "you could just" crowd sometimes forgets about the laws of physics when it comes to solving a problem. I guess those laws would be the "details" in most designs.

[J.P.M.]

I had lots of those when I was working in India - most came from the bean counter area or the owners. One time the boss suggested we just shoot oxygen on the 700°C hot iron coming out of our furnaces - make liquid steel and bypass a lot of other costly steps.

Kind like a BOF on steroids without containment ? At least it wasn't liquid O2 - or was it ?

[J.P.M.]

I agree with you. The "you could just" crowd sometimes forgets about the laws of physics when it comes to solving a problem. I guess those laws would be the "details" in most designs.

Maybe, but probably more like clueless about such things.

[russ]

Kind like a BOF on steroids without containment ? At least it wasn't liquid O2 - or was it ?

Yep - that was what he was thinking of and they do blow gaseous O2 - lots of it!

All he could see was cost savings - no BOF shop to build - all we had to do was dump the hot metal in the caster and SAVINGS.

We spent a short while discussing the problem and zero engineering hours on it.

[J.P.M.]

Yep - that was what he was thinking of and they do blow gaseous O2 - lots of it!

All he could see was cost savings - no BOF shop to build - all we had to do was dump the hot metal in the caster and SAVINGS.

We spent a short while discussing the problem and zero engineering hours on it.

Why didn't I think of that ?