"Matthew Maddock" wrote:

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.

Tres naturel.

I've seen this system on eBay
http://cgi.ebay.co.uk/ws/eBayISAPI.d...tem=6064859125
can anyone comment on how good these systems are (not necessarily
this one specifically)...

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...

Where we will be, there is plenty of sun, but it also gets pretty cold
in winter too (tho still usually sunny!)

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.

... are the systems any good?

Yes, generally speaking.

will it actually work to a satisfactory degree? or will the electric
backup element always be running?

The solar hot water fraction can be close to 100% if you spend enough money.

Considering that I can buy a large French "chauffe eau" (pressurised,
highly insulated electric water tank) for around 200€ max,
is it worth it?!!

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:

Y

^
|
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
2'|----------------------------F .
| 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...

20 PI=4*ATN(1)
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 ALD=180*(PI/2-A)/PI'lower elevation angle (degrees)
110 AUD=180*(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.

Nick

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.

Robert Gammon wrote:

....
As interesting as Nick's ideas are, I don't think that you want to
build a home brew solar hot water heater.


Why not?


--


Gary

www.BuildItSolar.com

"Build It Yourself" Solar Projects









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Gary wrote:
Robert Gammon wrote:

...
As interesting as Nick's ideas are, I don't think that you want to
build a home brew solar hot water heater.


Why not?


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.......)

Robert Gammon wrote:
Gary wrote:

Robert Gammon wrote:

...

As interesting as Nick's ideas are, I don't think that you want to
build a home brew solar hot water heater.


Why not?


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.......)

Hi Robert,
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
is required.
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.



Gary


--


Gary

www.BuildItSolar.com

"Build It Yourself" Solar Projects

Gary wrote:
Robert Gammon wrote:
Gary wrote:

Robert Gammon wrote:

...

As interesting as Nick's ideas are, I don't think that you want to
build a home brew solar hot water heater.


Why not?


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.......)

Hi Robert,
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
is required.
Anyway, was just wondering why you thought it would not be a good idea.

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.

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.


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.

"Robert Gammon" wrote in message
.net...

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've not seen any restrictions in England.

Mary

Robert Gammon wrote:
As interesting as Nick's ideas are, I don't think that you want to
build a home brew solar hot water heater.

I agree. If it were hot water, it would be a waste of effort to heat it.

- Logan

Matthew Maddock wrote

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.

They're hardly ever good value where mains power is available.

I've seen this system on eBay
http://cgi.ebay.co.uk/ws/eBayISAPI.d...tem=6064859125
can anyone comment on how good these systems
are (not necessarily this one specifically)...

Very over priced basically.

Where we will be, there is plenty of sun, but it also
gets prettycold in winter too (tho still usually sunny!)

... are the systems any good?

They do work, lousy value tho.

will it actually work to a satisfactory degree?

Really depends on how long you go without sun.

or will the electric backup element always be running?

No, not if its sized properly to the use of hot water.

Considering that I can buy a large French "chauffe eau"
(pressurised, highly insulated electric water tank) for
around 200€ max, is it worth it?!!

Nope.

In alt.solar.thermal Rod Speed wrote:
Matthew Maddock wrote

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.

They're hardly ever good value where mains power is available.

I've seen consistent proclamations that a solar DWH system is the best buy
for the money that can be made after pure conservation.

And those comaprisons are verses natural gas. I would expect solar verses
electric to be a very good proposition.

Why would you think that isn't true?
http://www.builditsolar.com

--
---
Clarence A Dold - Hidden Valley Lake, CA, USA GPS: 38.8,-122.5

wrote
Rod Speed wrote
Matthew Maddock wrote

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.

They're hardly ever good value where mains power is available.

I've seen consistent proclamations that a solar DWH system is the
best buy for the money that can be made after pure conservation.

Only by one eyed fools who havent got a clue about the basics.

And those comaprisons are verses natural gas. I would
expect solar verses electric to be a very good proposition.

It isnt. Largely because the MUCH higher capital cost cant
be justified economically. In spades in France where the
bulk of electrical power comes from nukes which dont even
consume natural resources in the generation of the power.

And then there's the resouces wasted with the relatively high
tech approach to solar hot water in the system being discussed.

Why would you think that isn't true?

Its mostly basic economics. The MUCH higher capital cost with
the system being discussed wont even pay for the electricity
that would otherwise be used if you have to borrow that money,
or even if you just forego the interest on the extra cash etc.

http://www.builditsolar.com

Just another rabid one eyed pack of lies on the economics.

Solar does make good economic sense with SOME situations,
most obviously with solar pool heating where the capital cost
is minimal, and the losses very high.

Solar can also make sense with air heating, particularly when its
designed into the house before construction, but its hardly ever
good value for water heating when offpeak mains power is available.

In alt.solar.thermal Rod Speed wrote:
It isnt. Largely because the MUCH higher capital cost cant
be justified economically. In spades in France where the
bulk of electrical power comes from nukes which dont even
consume natural resources in the generation of the power.

I neglected to question the cost of energy in France. What is it?

In California, it's all about trimming the tiered usage. The DWH sellers
quote the price comparisons at "tier 5" rates. The baseline rates don't
rise, but the high tiers do. Those KWh are currently $0.51. My DWH is
propane, currently at $1.69 per gallon, up from $1.07 in 2002.

And then there's the resouces wasted with the relatively high
tech approach to solar hot water in the system being discussed.

That is the difference between Nick's coil of hose and the $6000 I was
quoted for an installed system. ;-)

Solar does make good economic sense with SOME situations,
most obviously with solar pool heating where the capital cost
is minimal, and the losses very high.

I am considering both, and neglected to keep an eye on the cost
differential, since they both seem like a good idea in my area. The solar
pool heater will cost less than any other style of heater... but it is
entirely optional, so the "savings" is harder to justify. The solar
blanket could be considered sufficient. The solar heater also fits the
usage pattern. The heat is there when the usage is desired.

Solar can also make sense with air heating, particularly when its
designed into the house before construction, but its hardly ever
good value for water heating when offpeak mains power is available.

Offpeak mains power. Another caveat. I think showers would tend to be
offpeak for most people. Some mental agility is required to do the laundry
offpeak, or maybe not, depending on the lifestyle. Offpeak KWh is still
$0.30 at the high tier usage.

Retrofitting some solar air heating is on my list. I have a few months to
think about that one. I like the Solar Sponge, and it would fit neatly
into my current home design. http://solarsponge.com

--
---
Clarence A Dold - Hidden Valley Lake, CA, USA GPS: 38.8,-122.5

wrote
Rod Speed wrote

It isnt. Largely because the MUCH higher capital cost cant
be justified economically. In spades in France where the
bulk of electrical power comes from nukes which dont even
consume natural resources in the generation of the power.

I neglected to question the cost of energy in France. What is it?

Nothing special, because they have a lot of nuke generators now.

In California, it's all about trimming the tiered usage.
The DWH sellers quote the price comparisons at "tier 5"
rates. The baseline rates don't rise, but the high tiers do.
Those KWh are currently $0.51. My DWH is propane,
currently at $1.69 per gallon, up from $1.07 in 2002.

What anyone with a clue uses is the offpeak rate for hot water.

And then there's the resouces wasted with the relatively high
tech approach to solar hot water in the system being discussed.

That is the difference between Nick's coil of hose and
the $6000 I was quoted for an installed system. ;-)

Nope, the one being discussed is a lot more high tech than Nick's.

Solar does make good economic sense with SOME
situations, most obviously with solar pool heating where
the capital cost is minimal, and the losses very high.

I am considering both, and neglected to keep an eye on the cost
differential, since they both seem like a good idea in my area.
The solar pool heater will cost less than any other style of heater...

Yeah, they're very simple, often just black plastic
tubing on a flat roof. The pump etc is already there to.

but it is entirely optional, so the "savings" is harder to justify.

It isnt hard to justify it on the longer season of viable water temps.

The solar blanket could be considered sufficient.

Maybe, but its rather more irritating to use.

The solar heater also fits the usage pattern.
The heat is there when the usage is desired.

Solar can also make sense with air heating, particularly when its
designed into the house before construction, but its hardly ever
good value for water heating when offpeak mains power is available.

Offpeak mains power. Another caveat.

Its really the only sensible way to do hot water.

I think showers would tend to be offpeak for most people.
Some mental agility is required to do the laundry offpeak,
or maybe not, depending on the lifestyle.

The water tank is heated in off peak times and used any time you like.

Offpeak KWh is still $0.30 at the high tier usage.

Plenty pay nothing like that. I only pay 5c myself.

Retrofitting some solar air heating is on my list.

Its much better to do it at the house design stage.

I have a few months to think about that one. I like the Solar Sponge, and
it would fit neatly into my current home design. http://solarsponge.com

MUCH too small for my taste. I've got 7 8'x8' myself.

Rod Speed wrote:

Matthew Maddock wrote

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.

They're hardly ever good value where mains power is available.

I beg to differ. It's not hard to generate enough hot water to pay for a
DHW system in reduced electric costs. Pay back for my system vs.
electricity would be about 100 months. Not great, but I know many systems
running over 10 years with no capital additions, so it's workable. Since
I'm not _on_ grid, and use propane for hot water, payback is quicker.
--
derek

Derek Broughton wrote
Rod Speed wrote
Matthew Maddock wrote

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.

They're hardly ever good value where mains power is available.

I beg to differ.

You have to get down on your knees to beg properly.

It's not hard to generate enough hot water to
pay for a DHW system in reduced electric costs.

Dont believe it when its calculated properly.

Pay back for my system vs. electricity would be about 100 months.

Dont believe it, show the numbers.

Not great, but I know many systems running over
10 years with no capital additions, so it's workable.

Nope, not when its calculated properly.

Since I'm not _on_ grid, and use propane
for hot water, payback is quicker.

Sure, thats why I said what I said about mains power.

Rod Speed wrote:

Derek Broughton wrote

It's not hard to generate enough hot water to
pay for a DHW system in reduced electric costs.

Dont believe it when its calculated properly.

Pay back for my system vs. electricity would be about 100 months.

Dont believe it, show the numbers.

Where are yours?

$30 MINIMUM per month for electric hot water heating at my home. $3000,
installed, for a complete solar DHW system.

Not great, but I know many systems running over
10 years with no capital additions, so it's workable.

Nope, not when its calculated properly.

Show me the numbers.

Since I'm not _on_ grid, and use propane
for hot water, payback is quicker.

Sure, thats why I said what I said about mains power.

No, you said it wasn't workable with mains power. I just said it's even
faster when off-grid.
--
derek

Derek Broughton wrote
Rod Speed wrote
Derek Broughton wrote
Rod Speed wrote
Matthew Maddock wrote

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.

They're hardly ever good value where mains power is available.

It's not hard to generate enough hot water to
pay for a DHW system in reduced electric costs.

Dont believe it when its calculated properly.

Pay back for my system vs. electricity would be about 100 months.

Dont believe it, show the numbers.

Where are yours?

$30 MINIMUM per month for electric hot water heating at my home.

You need that anyway, you cant use pure solar almost anywhere.

$3000, installed, for a complete solar DHW system.

I just replaced my storage hot water system after 30 years for $500

Not great, but I know many systems running over
10 years with no capital additions, so it's workable.

Nope, not when its calculated properly.

Show me the numbers.

You didnt.

Since I'm not _on_ grid, and use propane
for hot water, payback is quicker.

Sure, thats why I said what I said about mains power.

No, you said it wasn't workable with mains power.

No I didnt. I said it wasnt usually GOOD VALUE.

I just said it's even faster when off-grid.

You also claimed that its viable on grid too.

wrote in message
...

"Matthew Maddock" wrote:

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.

Tres naturel.

I've seen this system on eBay
http://cgi.ebay.co.uk/ws/eBayISAPI.d...tem=6064859125
can anyone comment on how good these systems are (not necessarily
this one specifically)...

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...

Where we will be, there is plenty of sun, but it also gets pretty cold
in winter too (tho still usually sunny!)

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.

... are the systems any good?

Yes, generally speaking.

will it actually work to a satisfactory degree? or will the electric
backup element always be running?

The solar hot water fraction can be close to 100% if you spend enough
money.

Considering that I can buy a large French "chauffe eau" (pressurised,
highly insulated electric water tank) for around 200? max,
is it worth it?!!

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:

Y

^
|
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
2'|----------------------------F .
| 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...

20 PI=4*ATN(1)
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 ALD=180*(PI/2-A)/PI'lower elevation angle (degrees)
110 AUD=180*(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.

Nick

how about the old reliable "batch" or "bread box" style solar heater?
http://www.motherearthnews.com/top_a...r_Water_Heater
http://tva.apogee.net/res/rewhsba.asp
http://www.motherearthnews.com/Green...r_Water_Heater
http://www.solarnet.org/SolarHWH.htm
http://rise.org.au/reslab/resfiles/lowtemp/text.html