PV panels that also collect heat?

Dale Farmer · May 16, 2005

Does someone make a photoelectric panel that also has
a backing panel that picks up the waste heat? I have a
nice south facing roof on the house that I've got to re-roof,
and so I'm now looking into options for getting power and
heat out of what I put up.
Also, the bookstores I've looked at around have a plethora
of solar power books, and looking for suggestions on which
books are better. I've got good grounding in construction,
third generation carpenter here, living in a home my
grandfather built, so I don't need books that tell me how to
frame up supports or solder piping.
I'm in the Boston, Massachusetts area.

Thanks

--Dale

Derek Broughton · May 16, 2005

Dale said:
Does someone make a photoelectric panel that also has
a backing panel that picks up the waste heat?

I haven't heard of one, and I suspect it isn't a good idea. PV efficiency
(already low) goes down as the temperature goes up.

SQLit · May 16, 2005

Dale Farmer said:
Does someone make a photoelectric panel that also has
a backing panel that picks up the waste heat? I have a
nice south facing roof on the house that I've got to re-roof,
and so I'm now looking into options for getting power and
heat out of what I put up.
Also, the bookstores I've looked at around have a plethora
of solar power books, and looking for suggestions on which
books are better. I've got good grounding in construction,
third generation carpenter here, living in a home my
grandfather built, so I don't need books that tell me how to
frame up supports or solder piping.
I'm in the Boston, Massachusetts area.

Thanks

--Dale

Nice idea, I am unaware of any manufactures that provide this product.

Hot water is cheaper that PV. Especially when you factor in the replacement
of the batteries.

Dale Farmer · May 16, 2005

Derek said:
I haven't heard of one, and I suspect it isn't a good idea. PV efficiency
(already low) goes down as the temperature goes up.

True, But the water or whatever is intended to remove heat from
the panels. Possibly using a working fluid such as ammonia with a
low boiling point to pull more heat out of it in the winter time, which
is when I most need the heat.
I'm exploring options in thought experiment space right now.

--Dale

Me · May 17, 2005

Dale Farmer said:
Possibly using a working fluid such as ammonia with a
low boiling point to pull more heat out of it in the winter time, which
is when I most need the heat.

Don't even think of ammonia as a heat transfer agent, in this system
cause if you have ANY leak, your copper wiring will turn into blue powder
in short order. One of the new Freons would be a much better choice.

Me

Scott Willing · May 17, 2005

True, But the water or whatever is intended to remove heat from
the panels.
Exactly.

Possibly using a working fluid such as ammonia with a
low boiling point to pull more heat out of it in the winter time, which
is when I most need the heat.
I'm exploring options in thought experiment space right now.

AFAIK the basic concept is sound, and I suspect the main reasons you
don't see much in the way of combined systems is that (a) they'd be
much harder to sell, as they would fit fewer markets, and (b) solar
electric OEM's like Sharp et. al. probably don't have much plumbing
expertise.

Just guessing though. Possibly too many compromises in
combination?

I have a copy of "Practical Photovoltaics" by Richard J. Komp Ph.D.
(1995). It includes a couple of DIY panel projects, one of which
combines PV and thermal in the form of a long string of cells on a
single copper pipe with a serious "hippie student" sort of aesthetic.
However I've never seen a commercial system that combines the two
technologies.

-=s

Gordon Reeder · May 17, 2005

Does someone make a photoelectric panel that also has
a backing panel that picks up the waste heat? I have a
nice south facing roof on the house that I've got to re-roof,
and so I'm now looking into options for getting power and
heat out of what I put up.
Also, the bookstores I've looked at around have a plethora
of solar power books, and looking for suggestions on which
books are better. I've got good grounding in construction,
third generation carpenter here, living in a home my
grandfather built, so I don't need books that tell me how to
frame up supports or solder piping.
I'm in the Boston, Massachusetts area.

Thanks

--Dale

As others have pointed out there is probably not a product out
there that does both jobs. Perhaps a retrofit of a PV panel
could get you what you want. As a suggestion I would check
out a product by Radiantec as a place to start. This is a
coper flashing that attaches to the underside of a floor to
provide a retrofit to radient heat. But I don't see why it
couldn't be attached to the underside of a PV panel to extract
heat.

--
Just my $0.02 worth. Hope it helps
Gordon Reeder
greeder
at: myself.com

Hey Dubya!
Unity means let's try to meet each other halfway

Derek Broughton · May 17, 2005

Scott said:
Exactly.

I understand that, but I wonder how much usable heat you can get that way.
A typical hot-water collector lets the heat get much higher than would be
good for a PV panel. Perhaps that's only because the traditional use for
that water is to pre-heat your hot-water tank, and you don't really need
that high a temperature for home heating.

Derek Broughton · May 17, 2005

Jim said:
I do not understand where so many that contribute to these threads on
homepower assume that batteries are required for solar photo-voltaic
systems? If you need to be "Off-Line" and away from commercial power, yes
they are needed.

But, I feel it is far better if you are able to get on the commercial
power grid that you make use of it.

I agree. Unfortunately that doesn't work everywhere. afaik, it is still
impossible to get net metering in Nova Scotia (they _will_ happily put in
dual meters and pay you a pittance for the power going to the grid).

Your solar PV system is a lot cheaper
without the batteries and their controllers.

Just the batteris. Controllers are pretty cheap. But the batteries are by
far the most expensive component of my installation.

In most cases, your electric
meter will either slow down or run backwards when your solar cells are
producing power. That is generally true of all meters, no matter whether
your power company will give you credit for a meter that is less in
subsequent readings or not.

It isn't, however, always legal.

M Souness · May 18, 2005

I've seen a combination PV / concave mirror solar collector system somewhere
but cannot recall the exact details.

Regards,
Malcolm Souness
www.ruralenergy.co.nz

Norman Webb · May 19, 2005

I've been thinking along these lines.
My panels have got a 2" cavity underneath.
A collector as used in hot water systems could easily be installed in the
panel.

Advantages

It would have to keep the panel cooler for at least part of the day.
A seperate frame for hot water collector is not needed.

Jim Baber · May 19, 2005

Jim Baber's reply to:

I have a system with batteries that can do both. It is a grid tie and
a stand alone unit.

When are your peak and off-peak hours and do they change regularly, by
the season, at random or what schedule?

Thanx

John,
Pacific Gas and Electric has two sets of these Time Of Use rules for
rates, but for sake of simplicity, I will try to just explain the one
set that users MAY choose to use.

This is an option the user makes himself, if fact there is an extra 1
time charge of $277 to take advantage of the residential "TOU" rates,
and there probably is a one time cost for the commercial user also, but,
I do not know what it might be.

These rates only make sense if no one is using much power during the
PEAK hours (like they are at work elsewhere), unless you are exporting
power back to the utility. Then since, solar PV is producing best
during that same general time of day and will either export any unused
power back to the grid, or the solar will reduce the amount of power you
might otherwise need to import from the utility.

PEAK hours are weekdays only between noon and 6 PM and do take into
account daylight savings time, but no holidays.
OFF PEAK hours are all other times.

In general commercial users the other set of Time of use rules may
optionally apply and it divides the year into SUMMER (May 1 thru Oct.
31) and WINTER seasons. It also has 3 time frames during the summer
(PEAK, PARTIAL PEAK, OFF PEAK) and 2 during the winter (PARTIAL PEAK and
OFF PEAK)

PEAK hours are those hours on SUMMER weekdays between noon and 6 PM
and do take into account daylight savings times.
PARTIAL PEAK hours, except for certain holidays, are those hours
between 8:30 AM and 9:30 PM. During the SUMMER season,
when PEAK hours are in effect they supersede the partial peak rates
during the noon to 6 PM portion of the weekday.
OFF PEAK hours again are all other times.

Jim Baber · May 19, 2005

Jim Baber replies:
In my opinion, like I said elsewhere a transfer to a heat pump utilizing
that same 2" space heat source would avoid all the possible leak, and
freeze problems that can and do greatly complicate solar thermal
systems. The only thing "new" about this would be the ducting from your
2" cavity to the heat pump, and that could be done fairly inexpensively
via sheet metal ducting once you made a pattern. If it might leak a
little, so what, slap a little duct tape on it sometime when you get
around to it. It won't short out or flood any thing while you are
waiting for the rain to quit so you can fix it. This is exactly what I
am considering doing, heat pumps are not so unusual that you can't find
an installer or repairman if you need to, and they do not normally leak
water. By the way, you could also use the same hot air to preheat your
hot water and this could be done inside an attic to avoid any freezing
problem.

John P Bengi · May 19, 2005

If I read this correctly you have to volunteer for TOU metering installation
and pay for the meter and setup costs.

I also saw you post about $0.10 per off peak and $0.30 per on peak kWh. What
is the rate for not being on TOU metering, I am assuming is 24/7?

John P Bengi · May 20, 2005

Thanx. The table was so scrambled due to HTML and back I guess but I found
the rates table online.

It looks like you have a 1st to 5th rate based on area as they assign that
goes from about $0.11 to $0.27

If you go to TOU it still is graduated by total monthly consumption but also
based on TOU so now it varies from $0.11 to $0.37 per kWh.

I conclude if you want to play or are nocturnal you go TOU and if you are
just the average dumb consumer you would stay with non-TOU rates.

Have people found big differences when switching. Do many try it and fail
only to return?

I ask these questions because we see it coming. Ontario Canada are being
forced to install "smart" meters on every house and throw away 5 million
existing meters. The debate right now, in parliament is whether these meters
are going to be bi-directional communictaions. It sounds lie they want to
vary the peak times from day to day based on system peak demand.

I left the bottom mess so you could see the code that made it through...LOL

John P Bengi wrote:
If I read this correctly you have to volunteer for TOU metering installation
and pay for the meter and setup costs.

I also saw you post about $0.10 per off peak and $0.30 per on peak kWh. What
is the rate for not being on TOU metering, I am assuming is 24/7?

John,
Pacific Gas and Electric has two sets of these Time Of Use rules for
rates, but for sake of simplicity, I will try to just explain the one
set that users MAY choose to use.

This is an option the user makes himself, if fact there is an extra 1
time charge of $277 to take advantage of the residential "TOU" rates,
and there probably is a one time cost for the commercial user also, but,
I do not know what it might be.

These rates only make sense if no one is using much power during the
PEAK hours (like they are at work elsewhere), unless you are exporting
power back to the utility. Then since, solar PV is producing best
during that same general time of day and will either export any unused
power back to the grid, or the solar will reduce the amount of power you
might otherwise need to import from the utility.

PEAK hours are weekdays only between noon and 6 PM and do take into
account daylight savings time, but no holidays.
OFF PEAK hours are all other times.

In general commercial users the other set of Time of use rules may
optionally apply and it divides the year into SUMMER (May 1 thru Oct.
31) and WINTER seasons. It also has 3 time frames during the summer
(PEAK, PARTIAL PEAK, OFF PEAK) and 2 during the winter (PARTIAL PEAK and
OFF PEAK)

PEAK hours are those hours on SUMMER weekdays between noon and 6 PM
and do take into account daylight savings times.
PARTIAL PEAK hours, except for certain holidays, are those hours
between 8:30 AM and 9:30 PM. During the SUMMER season,
when PEAK hours are in effect they supersede the partial peak rates
during the noon to 6 PM portion of the weekday.
OFF PEAK hours again are all other times.

Jim Baber's Reply to JohnQ's additional request for the NON TOU rates

John , I have included the TOU rates as well above the NON TOU rates,
I don't know how well all of this will transmit copied right from PG&E's
rates. Here goes:
Total Energy Rates ($ per kWh) PEAK OFF-PEAK 
Summer  
Baseline Usage$0.29372 $0.08664  
101% - 130% of Baseline$0.29372 $0.08664  
131% - 200% of Baseline$0.33940 (R)$0.13232 (R) 
201% - 300% of Baseline$0.37857 |$0.17149 | 
Over 300% of Baseline$0.37857 (R)$0.17149 (R) 
Winter  

Baseline Usage$0.11472 $0.08966  
101% - 130% of Baseline$0.11472 $0.08966  
131% - 200% of Baseline$0.16040 (R)$0.13534 (R) 
201% - 300% of Baseline$0.19957 |$0.17451 | 
Over 300% of Baseline$0.19957 (R)$0.17451 (R) 
 
  
 
 

NO TOU  
Total Energy Rates ($ per kWh)  
Baseline Usage $0.11430
101% - 130% of Baseline $0.12989
131% - 200% of Baseline $0.17557 (R)
201% - 300% of Baseline $0.21474 |
Over 300% of Baseline $0.21474 (R)

Now I know that you are going to ask about the baseline, and I will attempt
to explain it as best as I can. There are

The concept was that the utility would determine a "typical number of kWh
that a typical user living in a certain geo-physical territory should
normally use. The general idea was to treat someone living in Fresno (a hot
desert city) fairly compared with someone in San Francisco or even Tahoe
high in the Sierra Nevada mountains, yet to be able to penalize those users
that were energy hogs. The following table I copied from PG&E's standard
residential rate table shows the daily "accepted quantity of kWh" for each
geo-physical territory the company has determined. Note: there is again a
difference as to what time of year and also if the home is "All Electric" or
not. By the way, they did determine summer vs winter by the same dates
they used for the TOU rate determination.

 2. BASELINE (TIER 1): The
following quantities of electricity are to be billed at the rates for
baseline use: 
 BASELINE QUANTITIES (kWh PER
DAY) 
 Code B - Basic
Quantities Code H - All-Electric
Quantities 
 Baseline Summer
Winter
Summer
Winter 
 Territory Tier I
Tier I Tier
I Tier I 
 
  
  
  

 P
15.8 12.9 19.5
31.1 
 Q
8.5 13.0 10.4
21.9 
 R
17.5 12.7 22.1
29.7 
 S
15.8 12.8 19.5
31.2 
 T
8.5 10.2 10.4
19.1 
 V
8.7 10.4 15.3
24.4 
 W
18.7 11.9 23.8
29.2 
 X
12.2 13.0 11.4
21.9 
 Y
11.3
 12.9 14.5
31.1 
 Z
7.3 11.2 14.0
 31.7 



 I have probably talked to 3 or 4 hundred
people about these Baseline quantities and I know for a fact well over half
of the people do not understand them at all and of the others I have
talked to, I can tell you that I have met only a very few who were under
their baseline quantities, and they all lived in newer apartments or "energy
efficient" new homes. These base lines are NOT TYPICAL at all. In fact
the decision we made to build a solar PV system was driven a lot by the
fact that our 1954 built house that sort of wanders all over the lot was a
real energy hog (typically always in the 300% of Territory R's Baseline with
4 people living in it). It does have good insulation in wall, ceilings. and
some 34 double paned windows, but it is a 4,000 sq. ft. house and has 3
"central" HVAC units that are zoned for efficiency.

So, JohnQ now you know all about it
Jim Baber E-mail me at jim, and I will send this all to you as an attachment

Jim Baber · May 20, 2005

Jim Baber wrote:
I apologize to all for the mess I got when I tried to show the whole set
of tables. It worked in HTML. at least it looks good in Netscape's
newsreader so I am sorry that it bothered anyone. I am trying to
remember some do not use HTML in the newsreader. But this time I sent it
that way because I knew it had tables.
I tried to contact John outside of the news group, but it didn't work:

Final-Recipient: rfc822; <[email protected]>
Action: failed

So if John or anyone else would like this information, E-mail me
directly, and I will send you an attachment in a .doc form with the
tables and explanation. My E-mail address is [email protected]

John P Bengi · May 21, 2005

The URL links are easy to find by googling "PG&E rates"

I actually prefer HTML anyway and the attempt was appreciated. No worries
mate.

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PV panels that also collect heat?

PV panels that also collect heat?

Dale Farmer

Derek Broughton

SQLit

Dale Farmer

Me

Scott Willing

Gordon Reeder

Derek Broughton

Derek Broughton

M Souness

Norman Webb

Jim Baber

Jim Baber

John P Bengi

John P Bengi

Jim Baber

John P Bengi

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