I am new to all of this, but have had a long term interest.
We are moving to France in a few months to a house that needs
renovating etc. There is no existing hot water system, so that
got me thinking that instead of putting in the usual electric
water heating system that is common in France, a solar system
might be nice.
I've seen this system on eBay
can anyone comment on how good these systems are (not necessarily
this one specifically). Where we will be, there is plenty of
sun, but it also gets pretty cold in winter too (tho still usually
I guess I really want to know, are the systems any good? will it
actually work to a satisfactory degree? or will the electric backup
element always be running? Considering that I can buy a large French
"chauffe eau" (pressurised, highly insulated electric water tank)
for around 200€ max, is it worth it?!!
Thanks in advance,
You still need some backup heating (Oil, Gas, Electric, ...) as you can not
guarantee you will always get a sunny day at least every n-th day. "n" is
dependent on the system layout and size. For me, it's 5-7, depending on the
See www.invest-tools.com/pub/solsys for a description of my system. I'm
still happy with it.
"Will it be worth it" - well that depends a lot on future energy prices. If
you take the current prices, usually "no" is the answer unless you do a lot
yourself and you get cheap and still qualitatively good parts (repair
costs!). You should find out how much electricity is usually used by the
electric heating, then you can calculate an approximate cost curve. I cannot
tell for France.
Here in Germany, I would assume electric heating is too expensive, so it
would be worth it. I never did calculate it, as I did not need it. Assuming
you need 5 kWh per day (which is approx. what we need, 2 adults, 3 kids),
it's 400 EUR/year here. Just compare it to the sum you need to pay for the
solar system, and add 1/4 of the electricity costs (75% solar, 25% backup
heating if the system is well designed). Plot the curves and look at the
Just as a rough calculation, of course.
Evacuated tubes with glass-to-metal seals tend to crack over time.
http://www.sunpowersolutions.com distributes Apricus systems
with no glass-to-metal seals in France...
How many kWh/m^2 of sun falls on the ground and south walls? Grenoble
(where I worked) is similar to Phila, with 620 Btu/ft^2 on the ground
and 1000 walls on an average January day with a 34 F daytime temp.
Yes, generally speaking.
The solar hot water fraction can be close to 100% if you spend enough money.
That's a cheap heat storage tank and cheap backup fuel, if rarely needed.
You might buy one and build a solar preheater (since you'll be renovating)
with a $35 fountain pump (eg Tractor Supply's #3119117) and a $60 1"x300'
pressurized plastic pipe coil in a $170 3'x8'x2' tall metal stock tank (TSC
#2177285) inside an 8'x12'x7' tall A-frame structure with a $100 8'x12'
Dynaglas polycarbonate south wall at a 30 degree tilt, which might collect
0.9x12(4x620+8cos(30)1000) = 101.6K Btu of sun and lose 6h(Tg-34)8x12/R1
= 576Tg-19.6K on an average day, where Tg (F) is the A-frame air temp.
If we collect Q Btu/day of useful heat, Tg = 210.4-Q/576.
If a 4'x12' tank cover collects 90% of the sun that enters the glazing
(91.4K Btu, with the help of 2'x12' of Big Fins on the south tank wall)
in Tw F water and loses 6h(Tw-Tg)1.5x6x12 = 648(Tw-Tg), Q = 305(352-Tw).
Tw = 140 F makes Q = 64.5K Btu (19 kWh) per day, with Tg = 98 F. It might
look like this, viewed in a fixed font:
7'| . <------------------------- sun
| . ru . south -->
| U. ru down-reflected upper ray
| . .
| . ru
| (x,y) 45 .
| . <---------- sun ru \
| . rl .8'
| L. rl ru \
| . rl down-reflected lower ray (not to scale)
|. 67.5 degrees
| i | 300' pipe coil | i B
| n | | n i .
| s | | s g
| u |300 gal stock tank| u F .
| l | | l i
| | | n white 60 .
0' ------------------------------------------------------------------> X
0' 4' 8'
The north wall could be made from 4'x8' 2" double-foil polyiso boards.
... 500 W of standard PV panels under a water duct on the lid might
produce 1000 W of electrical power...
30 F=4'max focal distance (ft)
40 A=PI/8'kerf angle (radians)
50 X=F/(1+1/TAN(A)/TAN(2*A))'x breakpoint (ft)
60 Y=X/TAN(A)+2'y breakpoint (ft)
70 L=SQR(X^2+(Y-2)^2)'lower segment length (ft)
80 H=8*COS(PI/6)'height (ft)
90 U=SQR((F-X)^2+(H-Y)^2)'upper segment length (ft)
100 ALD0*(PI/2-A)/PI'lower elevation angle (degrees)
110 AUD0*(PI/2-2*A)/PI'upper elevation angle (degrees)
120 PRINT F;L,ALD,U,AUD,2+L+U
focus -- lower segment -- -- upper segment -- total segment
(ft) length (ft) elev (deg) length (ft) elev (deg) length (ft)
4 3.061468 67.5 3.522649 45 8.584117
With lots of insulation, the 300 gallon tank could provide 300x8.33(140-60)
= 200K Btu of water heating over 5 cloudy days.
In the deep southeast Texas area that I live, in spite of 42 inches of
rain that we receive annually, A direct gain solar hot water heater
means that we spend very very little on hot water heating. Scald risk
is avoided because the water in the hot water tank is generally cooler
than the water coming down from the solar collector.
Lots of different designs out there for solar hot water, some good,
some no so good. Choose carefully and you CAN dramatically cut your
hot water costs. It would be best to look for products sold and
serviced in Europe. Cast your eyes a bit further than France as you
may find that both Germany and Italy offer decent solar products.
As interesting as Nick's ideas are, I don't think that you want to
build a home brew solar hot water heater.
Not in a house that you are in for only a couple of years, i.e. rent or
lease. Installing a commercial system, one that you can show hte owner
example sof and literature for is more likely to gain acceptance OUTSIDE
YOUR HOME COUNTRY.
So build it here on a home you own and so long as local building codes
allow, so long as homeowner deed restrictions will permit such a device
, and MANY now require details plans to be submitted in writing before
proceeding - we have to get shingle color approved, exterior pain colors
approved and the solar hot water system had to be approved by the HOA
BEFORE work began, then go ahead.
Just don't dream of doing this in a foreign country WITHOUT getting the
homeowner's approval AND consult with local real Estate professionals to
get their advice on the homebrew plan.
Could be a thing that gets you evicted over there, so be very very
careful if you intend to do homebrew in France (or Germany, or Italy, or
Spain, Or England.......)
I guess that makes sense if he is renting, or will not be there for long -- not
sure it thats the case or not?
Places vary a lot on approvals and covenants -- sounds like you live in a very
picky place. Where I am, the covenants are not very restrictive, and no permit
Anyway, was just wondering why you thought it would not be a good idea.
I think that DIY solar water heaters can be a good way to go. The cost of
commercial systems is high -- I think a lot due to low volume production. You
can save a substantial amount of money building your own. I think that the
simple payback on some systems could be as low as a couple years -- less if
energy rates keep going up. Not to mention the greenhouse gas benefits.
Most overseas assignments like this tend to be for two years or less due
to Visa requirements (displacement of citizen workers and all that). He
did not make it clear in posting I saw in alt.home.repair as quoted by
Nick whether this was to be a relatively short term assignment, as most
of these are, or if he is, in effect, emigrating to France, intended to
set up is long term household there, and to eventually renounce US
citizenship to become a French citizen.
DIY solar hot water, hmm
I see a 3-4 person system with 80 gallon heat exchanger tank (so
antifreeze soltuion flows thru the collector for only $2500 plus
installation. Yes, that is more than a gas powered hot water tank,
but will pay for itself quickly. This feeds into a standard hot water tank.
I think for whatever reason this was cross-posted! but I removed the
cross posting on my reply because I thought NG cross posting was
frowned upon! I am British, but am moving permanently to France.
Sorry - not used to NG's that are predominantly US read.
Thanks for the replies. Still don't know what to do, but will search
out more local information in France when I move there.
Where it is in bad form is multi posting, where the same or similar
message is posted *seperately* to multiple groups. You want to keep the
groups tied together.
Cross posting can be a good idea when you are not sure what group is
most appropriate or when the most appropriate group is very low traffic.
I'm not sure how on topic this is for alt.home.repair, I think 4 groups
is pushing it. Certainly widely crossposted posts have the most "noise"
in them because the participants don't know each other well, you wind up
with arguments about trivialities. See, I'll probably start one now!!!
I think almost any usenet group is dominated by the US, although solar
expertise doesn't seem to be dominanted in the same way ;-(
As in any case, you have to ignore the advice/advise you don't like ;-)
Some of the high government subsidies vary from place to place, changing
what is economically viable in one location into a losing proposition in
another. Do-it-yourself verses commercially produced is also a breaking
point. What Nick might build for a pittance is quoted at $6000 installed
I don't know if Nick actually builds anything, though.
Clarence A Dold - Hidden Valley Lake, CA, USA GPS: 38.8,-122.5
Brits are known for tolerating eccentrics, but the UK seems to have more
restrictions on looks than France, where we can invoke liberte' and egalite'
and call this kind of lawn ornament "art." French people deeply respect art,
to the point of setting aside 6% of the cost of public works for art...
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