On 2023-12-13 13:09, Fred Bloggs wrote:

'Scientists in the United States has developed a new photovoltaic-thermal system design that utilizes parallel water pipes as a cooling system to reduce the operating temperature of photovoltaic panels. The waste heat generated by this process is then

used to generate domestic hot water.'

Main thing is a miniature 11W pump stopped the panel conversion efficiency from degrading by a full 4%. The hot water thing is an aside. Unless the installation is at a YMCA or something similar, the average residential water heater is going to, or

actually must, divert the heat to prevent an overpressure release going off. Despite that it's a major cost advantage over those very expensive solar thermal heat collectors with sophisticated vacuum piping, circulating phase change medium, and all their
controls and special heat storage auxiliary water tanks, like those stone-lined tanks.

If that -0.45%/oC reduction in conversion efficiency is typical, it's a wonder the industry hasn't put more thought into cooling them.

https://www.pv-magazine.com/2023/12/12/using-waste-heat-from-pv-panels-to-generate-residential-hot-water/

Flat panel thermal collectors were a thing back in 1980ish--I had a
summer job building them, iirc 1979.

What they actually did was preheat the input water to a normal HW tank.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

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On Wed, 13 Dec 2023 10:09:11 -0800 (PST), Fred Bloggs <bloggs.fredbloggs.fred@gmail.com> wrote:

'Scientists in the United States has developed a new photovoltaic-thermal system design that utilizes parallel water pipes as a cooling system to reduce the operating temperature of photovoltaic panels. The waste heat generated by this process is then

used to generate domestic hot water.'

Main thing is a miniature 11W pump stopped the panel conversion efficiency from degrading by a full 4%. The hot water thing is an aside. Unless the installation is at a YMCA or something similar, the average residential water heater is going to, or

actually must, divert the heat to prevent an overpressure release going off. Despite that it's a major cost advantage over those very expensive solar thermal heat collectors with sophisticated vacuum piping, circulating phase change medium, and all their
controls and special heat storage auxiliary water tanks, like those stone-lined tanks.

If that -0.45%/oC reduction in conversion efficiency is typical, it's a wonder the industry hasn't put more thought into cooling them.

https://www.pv-magazine.com/2023/12/12/using-waste-heat-from-pv-panels-to-generate-residential-hot-water/

That sounds economically absurd.

And why would this be a eureka-level invention now?

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On 12/13/2023 11:28 AM, Phil Hobbs wrote:

On 2023-12-13 13:09, Fred Bloggs wrote:

'Scientists in the United States has developed a new photovoltaic-thermal
system design that utilizes parallel water pipes as a cooling system to
reduce the operating temperature of photovoltaic panels. The waste heat
generated by this process is then used to generate domestic hot water.'

Main thing is a miniature 11W pump stopped the panel conversion efficiency >> from degrading by a full 4%. The hot water thing is an aside. Unless the
installation is at a YMCA or something similar, the average residential water
heater is going to, or actually must, divert the heat to prevent an
overpressure release going off. Despite that it's a major cost advantage over
those very expensive solar thermal heat collectors with sophisticated vacuum >> piping, circulating phase change medium, and all their controls and special >> heat storage auxiliary water tanks, like those stone-lined tanks.

If that -0.45%/oC reduction in conversion efficiency is typical, it's a
wonder the industry hasn't put more thought into cooling them.

https://www.pv-magazine.com/2023/12/12/using-waste-heat-from-pv-panels-to-generate-residential-hot-water/

Flat panel thermal collectors were a thing back in 1980ish--I had a summer job
building them, iirc 1979.

What they actually did was preheat the input water to a normal HW tank.

Depends on the water temperature and volume available:

<https://pubs.aip.org/aip/acp/article/1766/1/020006/786702/REhnu-dish-based-CPV-Module-performance-and>

Click "PDF" link for actual article.

You can also use waste heat from an ACbrrrr:

<https://www.homedepot.com/c/ah/how-to-heat-a-swimming-pool-with-an-air-conditioner/9ba683603be9fa5395fab901a118c138>

You can also make use of shade from overhead panels (many parking lots,
here, are now "covered" thereby protecting the vehicles parked under
them as well as cutting down their cooling load when reoccupied).

And, use them to reduce evaporation:

<https://www.abc15.com/news/local-news/gila-river-indian-community-breaks-ground-on-installing-solar-panels-over-canal>

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On 2023-12-13 13:44, Fred Bloggs wrote:

On Wednesday, December 13, 2023 at 1:28:27 PM UTC-5, Phil Hobbs
wrote:

On 2023-12-13 13:09, Fred Bloggs wrote:

'Scientists in the United States has developed a new
photovoltaic-thermal system design that utilizes parallel water
pipes as a cooling system to reduce the operating temperature of
photovoltaic panels. The waste heat generated by this process is
then used to generate domestic hot water.'

Main thing is a miniature 11W pump stopped the panel conversion
efficiency from degrading by a full 4%. The hot water thing is
an aside. Unless the installation is at a YMCA or something
similar, the average residential water heater is going to, or
actually must, divert the heat to prevent an overpressure release
going off. Despite that it's a major cost advantage over those
very expensive solar thermal heat collectors with sophisticated
vacuum piping, circulating phase change medium, and all their
controls and special heat storage auxiliary water tanks, like
those stone-lined tanks.

If that -0.45%/oC reduction in conversion efficiency is typical,
it's a wonder the industry hasn't put more thought into cooling
them.

https://www.pv-magazine.com/2023/12/12/using-waste-heat-from-pv-panels-to-generate-residential-hot-water/

Flat panel thermal collectors were a thing back in 1980ish--I had

a summer job building them, iirc 1979.

What they actually did was preheat the input water to a normal HW
tank.

I think you'll find the more modern versions produce much hotter
water, hence all the insulation schemes.

You can't do that unless you're okay running your photovoltaic panels at upwards of 70 C. Second law of thermodynamics, and all that.

Concentrator panels run much hotter than that, of course.

'Flat plate solar collectors can reach temperatures as high as 200°C (395°F), and evacuated-tube collectors can reach temperatures as high
as 295°C (563°F). It is important to be aware that solar glycol will
begin to break down when temperatures exceed 150-200°C for long
periods of time.'

https://www.ecohome.net/guides/3297/product-of-the-month-solar-water-heater-with-overheating-protection/

'Evacuated-tube solar collectors They feature parallel rows of

transparent glass tubes. Each tube contains a glass outer tube and
metal absorber tube attached to a fin. The fin's coating absorbs
solar energy but inhibits radiative heat loss. These collectors are
used more frequently for U.S. commercial applications.'

https://www.energy.gov/energysaver/solar-water-heaters

Sure, we were using selective coatings too, though not vacuum. But you
aren't using those to improve photovoltaic efficiency.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

--- SoupGate-Win32 v1.05
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On 13/12/2023 18:28, Phil Hobbs wrote:

On 2023-12-13 13:09, Fred Bloggs wrote:

'Scientists in the United States has developed a new
photovoltaic-thermal system design that utilizes parallel water pipes
as a cooling system to reduce the operating temperature of
photovoltaic panels. The waste heat generated by this process is then
used to generate domestic hot water.'

Main thing is a miniature 11W pump stopped the panel conversion
efficiency from degrading by a full 4%. The hot water thing is an
aside. Unless the installation is at a YMCA or something similar, the
average residential water heater is going to, or actually must, divert
the heat to prevent an overpressure release going off. Despite that
it's a major cost advantage over those very expensive solar thermal
heat collectors with sophisticated vacuum piping, circulating phase
change medium, and all their controls and special heat storage
auxiliary water tanks, like those stone-lined tanks.

If that -0.45%/oC reduction in conversion efficiency is typical, it's
a wonder the industry hasn't put more thought into cooling them.

https://www.pv-magazine.com/2023/12/12/using-waste-heat-from-pv-panels-to-generate-residential-hot-water/

Flat panel thermal collectors were a thing back in 1980ish--I had a
summer job building them, iirc 1979.

That sounds about right - in the aftermath of the first OPEC induced oil crisis. I worked on something similar about then too. I still have a
couple of good books from that era on alternative energy...

ISTR there were slightly more sophisticated ones that had a modest sized
water tank at the top of the panel which thermal syphoning would allow
to get to quite a respectable temperature (at least on a sunny day) and
then a second heat exchange circuit to move that heat to where it was
needed in the domestic HW tank.

What they actually did was preheat the input water to a normal HW tank.

Or preheat the water to one of the fancier ones. ISTR simple FPC were
popular in California back then for heating outdoor swimming pool water.

--
Martin Brown

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Martin Brown <'''newspam'''@nonad.co.uk> wrote:

On 13/12/2023 18:28, Phil Hobbs wrote:

On 2023-12-13 13:09, Fred Bloggs wrote:

'Scientists in the United States has developed a new
photovoltaic-thermal system design that utilizes parallel water pipes
as a cooling system to reduce the operating temperature of
photovoltaic panels. The waste heat generated by this process is then
used to generate domestic hot water.'

Main thing is a miniature 11W pump stopped the panel conversion
efficiency from degrading by a full 4%. The hot water thing is an
aside. Unless the installation is at a YMCA or something similar, the
average residential water heater is going to, or actually must, divert
the heat to prevent an overpressure release going off. Despite that
it's a major cost advantage over those very expensive solar thermal
heat collectors with sophisticated vacuum piping, circulating phase
change medium, and all their controls and special heat storage
auxiliary water tanks, like those stone-lined tanks.

If that -0.45%/oC reduction in conversion efficiency is typical, it's
a wonder the industry hasn't put more thought into cooling them.

https://www.pv-magazine.com/2023/12/12/using-waste-heat-from-pv-panels-to-generate-residential-hot-water/

Flat panel thermal collectors were a thing back in 1980ish--I had a
summer job building them, iirc 1979.

That sounds about right - in the aftermath of the first OPEC induced oil crisis. I worked on something similar about then too. I still have a
couple of good books from that era on alternative energy...

ISTR there were slightly more sophisticated ones that had a modest sized water tank at the top of the panel which thermal syphoning would allow
to get to quite a respectable temperature (at least on a sunny day) and
then a second heat exchange circuit to move that heat to where it was
needed in the domestic HW tank.

What they actually did was preheat the input water to a normal HW tank.

Or preheat the water to one of the fancier ones. ISTR simple FPC were
popular in California back then for heating outdoor swimming pool water.

Pool collectors made much more sense, then and now. They don’t need an insulated box, for one thing.

These were all-copper and self-draining, with a manifold top and bottom,
and parallel tubes soldered to flashing-copper absorbers.

We used a neat little tool to make the manifolds—it was sort of like making spun-aluminum bowls. It had a screw+nut arrangement with a small ball on a hook. You drilled a small hole, stuck the hook in, and twisted the screw
part so that the hook pulled the metal out into a tee fitting.

Each manifold had eight or ten of them. They weren’t long or smooth enough
to use like a normal sweat fitting, so the parallel tubes were brazed on.
That annealed the copper too, which helped prevent leaks.

Fun job, for three months at least.

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

--- SoupGate-Win32 v1.05
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On 12/14/2023 3:57 AM, Martin Brown wrote:

Or preheat the water to one of the fancier ones. ISTR simple FPC were popular in California back then for heating outdoor swimming pool water.

Here, many pools are "heated" using just "miles" of black nylon (?) pipe
lying -- coiled -- on rooftops.

A smarter and cheaper way is to cover the surface of the water with
a large sheet of "bubble-wrap" (floats) to trap the heat gained from
solar exposure. This will easily yield 105+ degree water temperatures
(which actually is a bit uncomfortable).

It also has the benefits of keeping airborne cruft out of the water
(droppings from nearby palms) AND cutting evaporative losses. It's
not uncommon to lose ~1/2 inches each *day* in Summer; maybe half that
in Winter (hard to estimate Monsoon losses as rainwater adds to the pool).

Of course, automatic filler hides that chore from you -- until the monthly water/sewer bill arrives!

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On Thu, 14 Dec 2023 08:07:44 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:

On 12/14/2023 3:57 AM, Martin Brown wrote:

Or preheat the water to one of the fancier ones. ISTR simple FPC were popular
in California back then for heating outdoor swimming pool water.

Here, many pools are "heated" using just "miles" of black nylon (?) pipe >lying -- coiled -- on rooftops.

A smarter and cheaper way is to cover the surface of the water with
a large sheet of "bubble-wrap" (floats) to trap the heat gained from
solar exposure. This will easily yield 105+ degree water temperatures
(which actually is a bit uncomfortable).

It also has the benefits of keeping airborne cruft out of the water >(droppings from nearby palms) AND cutting evaporative losses. It's
not uncommon to lose ~1/2 inches each *day* in Summer; maybe half that
in Winter (hard to estimate Monsoon losses as rainwater adds to the pool).

Of course, automatic filler hides that chore from you -- until the monthly >water/sewer bill arrives!

An easier use case would be to use extra energy from the PV when you
can't sell back to grid, power the house or charge the batteries.

boB

--- SoupGate-Win32 v1.05
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On Thu, 14 Dec 2023 08:07:44 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:

On 12/14/2023 3:57 AM, Martin Brown wrote:

Or preheat the water to one of the fancier ones. ISTR simple FPC were popular
in California back then for heating outdoor swimming pool water.

Here, many pools are "heated" using just "miles" of black nylon (?) pipe >lying -- coiled -- on rooftops.

A smarter and cheaper way is to cover the surface of the water with
a large sheet of "bubble-wrap" (floats) to trap the heat gained from
solar exposure. This will easily yield 105+ degree water temperatures
(which actually is a bit uncomfortable).

It also has the benefits of keeping airborne cruft out of the water >(droppings from nearby palms) AND cutting evaporative losses. It's
not uncommon to lose ~1/2 inches each *day* in Summer; maybe half that
in Winter (hard to estimate Monsoon losses as rainwater adds to the pool).

Of course, automatic filler hides that chore from you -- until the monthly >water/sewer bill arrives!

A home swimming pool seems like a huge nuisance to me. And if you have
small kids, about the most deadly thing around.

--- SoupGate-Win32 v1.05
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On 12/14/2023 10:21 AM, boB wrote:

On Thu, 14 Dec 2023 08:07:44 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:

On 12/14/2023 3:57 AM, Martin Brown wrote:

Or preheat the water to one of the fancier ones. ISTR simple FPC were popular
in California back then for heating outdoor swimming pool water.

Here, many pools are "heated" using just "miles" of black nylon (?) pipe
lying -- coiled -- on rooftops.

A smarter and cheaper way is to cover the surface of the water with
a large sheet of "bubble-wrap" (floats) to trap the heat gained from
solar exposure. This will easily yield 105+ degree water temperatures
(which actually is a bit uncomfortable).

It also has the benefits of keeping airborne cruft out of the water
(droppings from nearby palms) AND cutting evaporative losses. It's
not uncommon to lose ~1/2 inches each *day* in Summer; maybe half that
in Winter (hard to estimate Monsoon losses as rainwater adds to the pool). >>
Of course, automatic filler hides that chore from you -- until the monthly >> water/sewer bill arrives!

An easier use case would be to use extra energy from the PV when you
can't sell back to grid, power the house or charge the batteries.

Apparently takes a shitload of energy to heat 15000G of water that is open
to the environment. (I don't know how this changes for folks with
*indoor* pools; I will have to ask my friends) E.g., I see 100KBTU
gas-fired heaters (30KW?) driving pools.

Most PV installations here are <~ 10KW so you really don't have much to
spare -- especially if you are powering refrigeration with "your"
electrons. The utility seems to have a say in just how big a PV
installation can be... perhaps only if grid tied? (We're looking
at installing ~5KW but NOT grid tied)

I think the better/cleverer way (for pools) is to use waste heat from the ACbrrrr. E.g., a typical 4T ACbrrr would move 48K BTU which is ballpark
with the gas-fired heater. *And*, the pool would most likely WANT to
be used when the ACbrrr is also likely to be "needed".

But, I see fewer and fewer folks using their *installed* pools. I
suspect some of it is age-related (kids seem to be the main motivator
for having a pool). Most of our friends with pools just pay to maintain them and never actually *use* them (unless the grandkids come for a visit).

Sadly, once you have a pool, you *must* maintain it. Draining it will
ruin the liner. Leaving it full (paying for evaporative losses) means
you need to keep the chemistry correct or risk it going south (a code violation, here). "Taking out" a pool is almost as expensive as putting
one *in*!

Finally, most are little more than big bathtubs... you can't swim laps
in a backyard (if I kick off from *any* wall in *any* residential pool,
here, I'll hit the far wall before I can take my first stroke!).

*If* you are willing to sacrifice yard space for a "water feature"
(that is NOT a fountain), your best bet is an "infinite pool".
This can be smaller (and more useful) than a nominal pool *or* a
"spa"/hottub. But, you're still stuck with all the maintenance
issues. How likely are you to "swim laps" to make use of it?

[We opted against a pool when selecting a home, here, as we didn't want
the maintenance/liability issues and didn't want to deprive the puppy
monsters of a yard in which to play. I can get 30 minutes of daily
exercise for a 32 minute investment -- the two minutes required to
put shoes on before heading out for a walk. Swimming has far more
overhead.]

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