I am looking at building a solar water heating system for domestic hot
water. I have 'Googled' and found quite a few good sites for DIY panels,
does anyone in this group have any good links to panel construction and
control systems?

Also has anyone (silly question!) done it and was it worth it.

I can but a system for about 2.5K but I would like to try to do some or all
of it myself.

Thanks.

--
brian

ashnook wrote:

I am looking at building a solar water heating system for domestic hot
water. I have 'Googled' and found quite a few good sites for DIY panels,
does anyone in this group have any good links to panel construction and
control systems?

Also has anyone (silly question!) done it and was it worth it.

I can but a system for about 2.5K but I would like to try to do some or all
of it myself.

This one on a mountain hut does not look elegant but it works
like a charm. It works off tank water, and the water is so hot it
needs to have a temperature limiter.
http://i2.tinypic.com/qowuog.jpg

I've always wondered why a cheapskate one couldn't be built using
vast coils of cheap black plastic pipe of a type that can stand
being in the sun for years, and covered with old window sashes or
similar. If you are prepared to have a small electric pump, that
could feed to an existing tank that does not have to be on the
roof. It would need a way of releasing pressure in case the pump
stopped.

"ashnook" wrote in message
...

I am looking at building a solar water heating system for domestic hot
water. I have 'Googled' and found quite a few good sites for DIY panels,
does anyone in this group have any good links to panel construction and
control systems?

Also has anyone (silly question!) done it and was it worth it.

I can but a system for about 2.5K but I would like to try to do some or
all of it myself.

brian, look at http://www.cat.org.uk They supply kits and all the books
too. If fitting a solar panel or two. Look at http://www.navitron.org.uk/

If fitting a solar system use a thermal store/heat bank, not a preheat
cyldiner. Heat is input into the store via solar panels and boiler, etc.
Heat is output into the DHW and CH. All in one cylidner. If you go this
route, I will give you setup for the contol system to prioritise the solar
heated hot water in the lower sectron of the store, and keep the burner off
as long as poosible to heat the upper boioer heated section.

Further info on solar thermal sto
http://www.heatweb.com/solar/solar.html

On Sat, 4 Mar 2006 08:10:33 -0000, "ashnook"
wrote:

I am looking at building a solar water heating system for domestic hot
water. I have 'Googled' and found quite a few good sites for DIY panels,
does anyone in this group have any good links to panel construction and
control systems?

Also has anyone (silly question!) done it and was it worth it.

I can but a system for about 2.5K but I would like to try to do some or all
of it myself.

I have followed some threads on this in the past and think there are a
few 'questions' you might need to answer first.

1) Do you intend to stay at that place for a good few years (if you
are interested in clawing the installation cost back via energy
savings? That time will depend on the cost of the install (may be
improved by your diy input) and the cost of 'buying in' energy (going
up fast at the moment).

2) From a global point of view, how long would it take to recoupe the
energy expended making the items you use for the cheating the project
(along the lines where electrical solar panels used (?) to take more
energy to make than they ever gave back in their lifespans)?

The above is compared with locations where you actually have a choice
of course (like a gas / electric supply .. ie you aren't in the
middle of nowhere ...) ;-)

Given all positive answers to the above and that you have a favorable
outlook (South facing etc) and you make the system 'big / concise
enough' then I believe it's possible to provide much of your hot water
most of the year .. even in the UK ;-)

All the best .. and good luck if you go for it .. ;-)

T i m

"T i m" wrote in message
...
On Sat, 4 Mar 2006 08:10:33 -0000, "ashnook"
wrote:

I am looking at building a solar water heating system for domestic hot
water. I have 'Googled' and found quite a few good sites for DIY panels,
does anyone in this group have any good links to panel construction and
control systems?

Also has anyone (silly question!) done it and was it worth it.

I can but a system for about 2.5K but I would like to try to do some or
all
of it myself.

I have followed some threads on this in the past and think there are a
few 'questions' you might need to answer first.

1) Do you intend to stay at that place for a good few years (if you
are interested in clawing the installation cost back via energy
savings? That time will depend on the cost of the install (may be
improved by your diy input) and the cost of 'buying in' energy (going
up fast at the moment).

2) From a global point of view, how long would it take to recoupe the
energy expended making the items you use for the cheating the project
(along the lines where electrical solar panels used (?) to take more
energy to make than they ever gave back in their lifespans)?

The above is compared with locations where you actually have a choice
of course (like a gas / electric supply .. ie you aren't in the
middle of nowhere ...) ;-)

Being in the middle of nowhere makes solar energy more necessary and
appealing.

Given all positive answers to the above and that you have a favorable
outlook (South facing etc) and you make the system 'big / concise
enough' then I believe it's possible to provide much of your hot water
most of the year .. even in the UK ;-)

All the best .. and good luck if you go for it .. ;-)

T i m

Depending on how it is done (panels looking ugly on the roof right at the
front, etc) and positive proof of savings, a solar system can be a selling
point, and may add some value.

On Sat, 4 Mar 2006 08:10:33 -0000, "ashnook"
wrote:

Also has anyone (silly question!) done it

Yes

and was it worth it.

No. It was an interesting experiment but never paid for itself and
contributed little in terms of energy saved, nothing at all when you
considered manufacturing costs. You are far better off looking at
improving insulation and ventilation.

--
Peter Parry.
http://www.wpp.ltd.uk/

wrote in message
oups.com...

Dont attempt to solar heat a thermal
store / heat bank, as DHW panels
run this way will have very low efficiency,
and contribute close to zilch.

You xclearly know little of thermal stores/solar to come with such a crass
comment.

Preheat cylinders are used because
they are the one way to get
good efficiency from unconcentrated panels.

The pre-heat cylinder can be the bottom half of a thermal store, not heated
by anything but solar panels. The DHW drawoff can take off water from the
solar section and when too cool start to use the cooler solar heated water
for mixing, instead of much colder mains water. An depletion of hot water
in the upper section heated by a boiler, will be replaced by warmer water
from the lower section, not very cold mains water, hence keeping the burner
off for longer. Not difficult or expensive to do, using only a 3-way
blending valve with a remote temperature.

Also any solar generated heat can be used for CH too.

Preheat cylinders are notorious for being inefficient to all one cylinder
thermals storage.

ashnook wrote:
I am looking at building a solar water heating system for domestic hot
water. I have 'Googled' and found quite a few good sites for DIY panels,
does anyone in this group have any good links to panel construction and
control systems?

Also has anyone (silly question!) done it and was it worth it.

I can but a system for about 2.5K but I would like to try to do some or all
of it myself.

http://www.sustainable-girton.org.uk/pv/ gives a few figures on a new PV
installation, which in *February* produced 2/3 of the owner's
consumption. On good days it made 3.3Kw.

If you contact me privately I could get more details for you but you
should be able to work out the installer's website from the pictures.

Douglas de Lacey

Doctor Drivel wrote:
wrote in message
oups.com...

Preheat cylinders are used because
they are the one way to get
good efficiency from unconcentrated panels.

The pre-heat cylinder can be the bottom half of a thermal store, not heated
by anything but solar panels. The DHW drawoff can take off water from the
solar section and when too cool start to use the cooler solar heated water
for mixing, instead of much colder mains water. An depletion of hot water
in the upper section heated by a boiler, will be replaced by warmer water
from the lower section, not very cold mains water, hence keeping the burner
off for longer. Not difficult or expensive to do, using only a 3-way
blending valve with a remote temperature.

In principle its a good idea. To work the panels efficiently though you
need a lot of stratification, as panel efficiency drops rapidly as the
water they heat gets hotter. I'm not sure how much temp diff in the
tank one would get in practice.


Also any solar generated heat can be used for CH too.

not really hot enough. CH runs at close to flat panel stagnation temp,
making efficiency close to zero. Evacuated tubes would contribute, but
are high cost and lower output.

I suppose in principle one might try circulating the CH system via the
solar panel, with boiler off, when the room stat is already satisfied.
The lower heat output could then extend the time it takes before the
boiler refires due to the stat calling for more heat.

On 2nd thoughts a comfort zone would be the thing, let the solar heat
run when the stat is satisfied, but only as far as 1-2C above stat
setting.

This is only going to fly when the boiler off periods are long enough
for rad water to cool to below solar panel output temp, at peak heat
times the panels would contribute nothing.


Really quite a lot could be done with solar HW once you have a flexible
and capable multivalve controller panel. These are unheard of today,
but if they become low cost they could control the flow from multiple
inputs to multiple outputs, working out how to maximise return at all
times. For example the inputs might be:
- minimum cost solar collector, eg black radiator or hose panel
- medium cost flat panels
- high cost evacuated tube collectors
- boiler

and the outputs would be several layers in the HW heat store, each at
different temperature. The controller would monitor all the temps and
work out what to route where when to maximise output.

The controller would also automatically drain down collectors when
frost damage risk arose. This means an all direct system, with its
lower install cost, higher efficiency, and more routing flexibility.


Preheat cylinders are notorious for being inefficient to all one cylinder
thermals storage.

They extract heat from the panels efficiently, which is why they get
used, then they use that heated water inefficiently.


NT

wrote in message
oups.com...
Doctor Drivel wrote:
wrote in message
oups.com...

Preheat cylinders are used because
they are the one way to get
good efficiency from unconcentrated panels.

The pre-heat cylinder can be the bottom half of a thermal store, not
heated
by anything but solar panels. The DHW drawoff can take off water from the
solar section and when too cool start to use the cooler solar heated
water
for mixing, instead of much colder mains water. An depletion of hot
water
in the upper section heated by a boiler, will be replaced by warmer water
from the lower section, not very cold mains water, hence keeping the
burner
off for longer. Not difficult or expensive to do, using only a 3-way
blending valve with a remote temperature.

In principle its a good idea. To work the panels efficiently though you
need a lot of stratification, as panel efficiency drops rapidly as the
water they heat gets hotter. I'm not sure how much temp diff in the
tank one would get in practice.


Also any solar generated heat can be used for CH too.

not really hot enough.

You are only guessing here.

CH runs at close to flat panel
stagnation temp, making efficiency
close to zero.

The solar section is at the bottom with the DHW top, CH middle and solar
bottom. No CH return to the solar section, only the middl;e CH section.
Using a plate heat exchanger the return from the DHW can be directly into
the bottom of the cylidner in the solar section. That is because the
efficiencies of the plate is phenominal. There can be 80C into the plate
and the temp of the pipe coming out is so low you can grab the pipe
infefinately. So, cold/very cool water enters the solar section. A tall
thin cylinder helps in stratification.

Evacuated tubes would contribute, but
are high cost and lower output.

http://www.navitron.org.uk

I suppose in principle one might try
circulating the CH system via the
solar panel, with boiler off, when
the room stat is already satisfied.
The lower heat output could then
extend the time it takes before the
boiler refires due to the stat calling for more heat.

No. Just heat the solar section. Any heat extracted from the centre CH
section (cool return water) will be replaced by hotter solar water in the
lower section (hot water rises).

Really quite a lot could be done with solar HW once you have a flexible
and capable multivalve controller panel. These are unheard of today,
but if they become low cost they could control the flow from multiple
inputs to multiple outputs, working out how to maximise return at all
times. For example the inputs might be:
- minimum cost solar collector, eg black radiator or hose panel
- medium cost flat panels
- high cost evacuated tube collectors
- boiler

May as well fit the optimum cost/perfoanmnce panel rather than inefficient
black rads.

and the outputs would be several layers in the HW heat store, each at
different temperature. The controller would monitor all the temps and
work out what to route where when to maximise output.

The controller would also automatically drain down collectors when
frost damage risk arose. This means an all direct system, with its
lower install cost, higher efficiency, and more routing flexibility.

Preheat cylinders are notorious for being inefficient to all one cylinder
thermals storage.

They extract heat from the panels efficiently, which is why they get
used, then they use that heated water inefficiently.

Mixing and prioritising water use is the problem. A preheat may have very
useful hot water at the top, yet this only enters the run cylinder when it
draws-off hot water. Then this hot ware mixes with the run cylinders cooler
water cooling the water overall. Not what you want. An all one thermal
store can prioritise the use of solar water very easily with one blending
valve and mix the solar water with hotter DHW boiler heated water.

Have a look at www.navitron.org.uk I bought a 20 tube solar panel at a very
good price which made it better than building one. Haven't installed it yet
though


"ashnook" wrote in message
...
I am looking at building a solar water heating system for domestic hot
water. I have 'Googled' and found quite a few good sites for DIY panels,
does anyone in this group have any good links to panel construction and
control systems?

Also has anyone (silly question!) done it and was it worth it.

I can but a system for about 2.5K but I would like to try to do some or
all of it myself.

Thanks.

--
brian

Doctor Drivel wrote:
wrote in message
oups.com...


Also any solar generated heat can be used for CH too.

not really hot enough.

You are only guessing here.

no, as explained he

CH runs at close to flat panel
stagnation temp, making efficiency
close to zero.

The solar section is at the bottom with the DHW top, CH middle and solar
bottom.

DHW is usually not as hot as CH, 65 versus anything upto 82, so an
unusual choice. Why choose to heat dhw to above its use temp, to extend
heat capacity?


No CH return to the solar section, only the middl;e CH section.
Using a plate heat exchanger the return from the DHW can be directly into
the bottom of the cylidner in the solar section.

return from DHW? whats that?
where does the plate exchanger connect in your scheme (it has 4
connections)

That is because the
efficiencies of the plate is phenominal. There can be 80C into the plate
and the temp of the pipe coming out is so low you can grab the pipe
infefinately. So, cold/very cool water enters the solar section.

hard to know what to think until you explain your setup clearly.


A tall
thin cylinder helps in stratification.

yes

Evacuated tubes would contribute, but
are high cost and lower output.

http://www.navitron.org.uk

20" of panel for £220 is steep (10x 2" tubes). Evacuated tubes also
dont perform well in winter in Britain, flat plate works better. Tubes
are good with direct sun only, plates work ok on diffuse IR too.

BTW when are people going to start cutting fl tubes and putting copper
or plastic pipe thru them? 10 tubes for a tenner that way.


I suppose in principle one might try
circulating the CH system via the
solar panel, with boiler off, when
the room stat is already satisfied.
The lower heat output could then
extend the time it takes before the
boiler refires due to the stat calling for more heat.

No. Just heat the solar section. Any heat extracted from the centre CH
section (cool return water) will be replaced by hotter solar water in the
lower section (hot water rises).

But its not cool return water, CH return is still not that far from
panel stagnation temps. Except of course with vac tubes, but those are
just too expensive to pay their way.

You still need to change the thermostat setup to make use of the solar
heat, otherwise the pump only comes on when heat is needed, and the
solar part wont supply high enough water temp to avoid the boiler
firing. IOW the system would not heat the rads between boiler firings.


Really quite a lot could be done with solar HW once you have a flexible
and capable multivalve controller panel. These are unheard of today,
but if they become low cost they could control the flow from multiple
inputs to multiple outputs, working out how to maximise return at all
times. For example the inputs might be:
- minimum cost solar collector, eg black radiator or hose panel
- medium cost flat panels
- high cost evacuated tube collectors
- boiler

May as well fit the optimum cost/perfoanmnce panel rather than inefficient
black rads.

The point is that each type of panel has its own advantages, and is the
best choice for some and only some of the work.

Tubes are best for the highest temp water input, theyre the only ones
that will heat water thats nearly hot enough with any efficiency. But
their cost is excessive for any other task, and they dont collect well
in winter.

Flat plates are the middle ground, mid price, mid efficiency, no use at
higher temps, and unnecessarily costly for heating cold water. But the
best option for a fair range of water heating temps.

Black rads will preheat cold incoming water effectively, and do so at
less cost than the others, but are not for medium or high temps. Their
inbuilt water storage means no need to allocate more tank capacity for
the lowest temp water layer, that temperature layer is effectively done
in the rads. Adding 15-20C to the tank's incoming water temp means more
piping hot water out the other end, and at minimal cost. That means
savings can be made elsewhere in the system for the same overall system
performance, giving better energy/£ ratio.

Most simply, rads can be connected between header tank and water tank,
though thats not what I'm suggesting doing here.


The whole point of a mixed panel system is to get the highest output
with the least cost - which is the only way solar dhw will ever pay.
Using vac tubes to heat cold incoming water is sheer folly - yet its
often done.


and the outputs would be several layers in the HW heat store, each at
different temperature. The controller would monitor all the temps and
work out what to route where when to maximise output.

The controller would also automatically drain down collectors when
frost damage risk arose. This means an all direct system, with its
lower install cost, higher efficiency, and more routing flexibility.

Preheat cylinders are notorious for being inefficient to all one cylinder
thermals storage.

They extract heat from the panels efficiently, which is why they get
used, then they use that heated water inefficiently.

Mixing and prioritising water use is the problem. A preheat may have very
useful hot water at the top, yet this only enters the run cylinder when it
draws-off hot water. Then this hot ware mixes with the run cylinders cooler
water cooling the water overall. Not what you want. An all one thermal
store can prioritise the use of solar water very easily with one blending
valve and mix the solar water with hotter DHW boiler heated water.

Yes... if you can maintain enough stratification.

Also a separate preheat cylinder means more surface area per volume
stored, meaning more heat loss or more insulation expense, or both.


NT

Quality & Value
"ashnook" wrote in message
...
I am looking at building a solar water heating system for domestic hot
water. I have 'Googled' and found quite a few good sites for DIY panels,
does anyone in this group have any good links to panel construction and
control systems?

Also has anyone (silly question!) done it and was it worth it.

I can but a system for about 2.5K but I would like to try to do some or
all of it myself.

Thanks.

--
brian


Thanks for the input Group. The Navitron stuff looks good.

I want to use something on a barn conversion we might move to. Add more
insulation etc. is not an option as no loft etc. exists. The boiler is oil
fired but no indirect to HW tank so all HW is electric, E7 at night and full
price during the day. I can get to the tank from the roof line so I was
thinking solar HW would be helpful here.

I thing self build for possibly £1k might be worthwhile if we assume we will
stay for 10 years. Once installed the running costs are very low and almost
free of energy price rises.

.... or have I got me head in a dark place?

Thanks
Brian

wrote in message
oups.com...
Doctor Drivel wrote:
wrote in message
oups.com...


Also any solar generated heat can be used for CH too.

not really hot enough.

You are only guessing here.

no, as explained he

CH runs at close to flat panel
stagnation temp, making efficiency
close to zero.

The solar section is at the bottom
with the DHW top, CH middle and solar
bottom.


DHW is usually not as hot as CH, 65 versus anything upto 82, so an
unusual choice. Why choose to heat dhw to above its use temp, to extend heat
capacity?


It is clear you don't understand the principle of heat banks.thermal stores.
the DHW stored water is between 70-85C to instantly heat the incoming water.

No CH return to the solar section,
only the middle CH section.
Using a plate heat exchanger the
return from the DHW can be directly into
the bottom of the cylidner in the solar section.

return from DHW? whats that?
where does the plate exchanger
connect in your scheme (it has 4
connections)


It is clear you need to understand how they work. See
http://www.heatweb.com That gives good explanations. No se sens ein
continuing until you understand, you think about it and then form questions.

"Douglas de Lacey" wrote in message
...
ashnook wrote:
I am looking at building a solar water heating system for domestic hot
water. I have 'Googled' and found quite a few good sites for DIY panels,
does anyone in this group have any good links to panel construction and
control systems?

Also has anyone (silly question!) done it and was it worth it.

We've just done it and it's a joy! We weren't thinking about pay-back but it
will be worthwhile in that respect, especially given fuel price rises.

I can but a system for about 2.5K but I would like to try to do some or
all of it myself.

We bought a panel and pv pump from www.Solartwin.com and they've been
extremely helpful and friendly. It's probably been the best company we've
ever dealt with for anything. We installed it ourselves, it didn't save much
because it meant that we weren't eligible for a grant but it was far more
satisfying than having someone else do it.

We're getting a large tank full of water at over 40C even on recent days
when everything outside has been frozen.

Several of our friends and family have been so impressed that they're
looking into it.

Mary

"ashnook" wrote in message
...
Quality & Value
"ashnook" wrote in message
...
I am looking at building a solar water heating system for domestic hot
water. I have 'Googled' and found quite a few good sites for DIY panels,
does anyone in this group have any good links to panel construction and
control systems?

Also has anyone (silly question!) done it and was it worth it.

I can but a system for about 2.5K but I would like to try to do some or
all of it myself.

Thanks.

--
brian


Thanks for the input Group. The Navitron stuff looks good.

I want to use something on a barn conversion we might move to. Add more
insulation etc. is not an option as no loft etc. exists. The boiler is oil
fired but no indirect to HW tank so all HW is electric, E7 at night and
full price during the day. I can get to the tank from the roof line so I
was thinking solar HW would be helpful here.

I thing self build for possibly £1k might be worthwhile if we assume we
will stay for 10 years. Once installed the running costs are very low and
almost free of energy price rises.

... or have I got me head in a dark place?

No, you are correct. 5 years ago laughed at peopel who eco things and
bopasted they virtually no insulation and oil bills were low. How time
schange quickly. 5 years ago if you said gas would rise 25% in one swoop
they would have locked you up. Energy will "never" get cheaper.

I know of a solar DHW system installed in the oil crisis of 193/74. Most had
never heard of the stuff, many said it would not make back the cost. Many
said it wouldn't work. The usual comments. The only thing gone wrong in 30
years is a new brass pump, well the head. The money it must have saved over
30 years must be quite a stack.

Doctor Drivel wrote:
wrote in message

The solar section is at the bottom
with the DHW top, CH middle and solar
bottom.


DHW is usually not as hot as CH, 65 versus anything upto 82, so an
unusual choice. Why choose to heat dhw to above its use temp, to extend heat
capacity?


It is clear you don't understand the principle of heat banks.thermal stores.
the DHW stored water is between 70-85C to instantly heat the incoming water.

What is clear is you didnt fully describe your proposed system. Now we
know which body of water is in the tank. And we also know that this
approach makes solar collection less efficient, which is why I had
initially guessed you had the DHW in the tank, being drawn off at the
top for the taps. This would be more efficient.


No CH return to the solar section,
only the middle CH section.
Using a plate heat exchanger the
return from the DHW can be directly into
the bottom of the cylidner in the solar section.

return from DHW? whats that?
where does the plate exchanger
connect in your scheme (it has 4
connections)


It is clear you need to understand how they work. See
http://www.heatweb.com That gives good explanations. No se sens ein
continuing until you understand, you think about it and then form questions.

Either describe your setup or dont.


NT

"Doctor Drivel" wrote in message
reenews.net...

"ashnook" wrote in message
...
Quality & Value
"ashnook" wrote in message
...
I am looking at building a solar water heating system for domestic hot
water. I have 'Googled' and found quite a few good sites for DIY panels,
does anyone in this group have any good links to panel construction and
control systems?

Also has anyone (silly question!) done it and was it worth it.

I can but a system for about 2.5K but I would like to try to do some or
all of it myself.

Thanks.

--
brian


Thanks for the input Group. The Navitron stuff looks good.

I want to use something on a barn conversion we might move to. Add more
insulation etc. is not an option as no loft etc. exists. The boiler is
oil fired but no indirect to HW tank so all HW is electric, E7 at night
and full price during the day. I can get to the tank from the roof line
so I was thinking solar HW would be helpful here.

I thing self build for possibly £1k might be worthwhile if we assume we
will stay for 10 years. Once installed the running costs are very low and
almost free of energy price rises.

... or have I got me head in a dark place?

No, you are correct. 5 years ago laughed at peopel who eco things and
bopasted they virtually no insulation and oil bills were low. How time
schange quickly. 5 years ago if you said gas would rise 25% in one swoop
they would have locked you up. Energy will "never" get cheaper.

I know of a solar DHW system installed in the oil crisis of 193/74. Most
had never heard of the stuff, many said it would not make back the cost.
Many said it wouldn't work. The usual comments. The only thing gone wrong
in 30 years is a new brass pump, well the head. The money it must have
saved over 30 years must be quite a stack.


I forgot to add in the earlier mail that I cannot add more insulation due to
no loft so this is what I seem to be left with.

Brian

On Sat, 4 Mar 2006 17:15:44 -0000, "ashnook"
wrote:


I want to use something on a barn conversion we might move to. Add more
insulation etc. is not an option as no loft etc. exists. The boiler is oil
fired but no indirect to HW tank so all HW is electric, E7 at night and full
price during the day. I can get to the tank from the roof line so I was
thinking solar HW would be helpful here.

You would be better replacing the existing system with one which
included hot water provision off the boiler. Almost anything you do
to improve the efficiency or running cost of existing systems will be
more worthwhile than solar panels.

I thing self build for possibly £1k might be worthwhile if we assume we will
stay for 10 years. Once installed the running costs are very low and almost
free of energy price rises.

... or have I got me head in a dark place?

Mostly :-). The best you will get from a south facing correctly
angled collector is about 350kWh/year per m2 of installed collector.
In the winter months this drops to well under 500Wh a day. Most
practical installations are about 4m2. In the winter they can't
provide enough energy, in the summer you usually end up unable to use
all the energy collected as you simply don't use enough hot water.
Solar water heaters are most economically in places with large hot
water demands, such as schools and hospitals.

Typically you might save about GBP100 a year. However solar systems
are not as maintenance free as some suppliers and ecowarriors would
have you think and failures in the panels, which are obviously
subject to a lot of temperature cycling, is not uncommon. Certainly
the figure of 25 years useful life quoted by protagonists are not
supported by past experience anywhere in the world (unless you invoke
Triggers Broom).


--
Peter Parry.
http://www.wpp.ltd.uk/

On Sat, 04 Mar 2006 13:51:44 +0000, Douglas de Lacey
wrote:


http://www.sustainable-girton.org.uk/pv/ gives a few figures on a new PV
installation, which in *February* produced 2/3 of the owner's
consumption. On good days it made 3.3Kw.

"The total cost was large,...If the predictions are correct, these
costs will be paid back in around 24 years"

Solar water heating may be marginal but solar pv is a wonderful way
of wasting money.


--
Peter Parry.
http://www.wpp.ltd.uk/

wrote in message
oups.com...
Doctor Drivel wrote:
wrote in message

The solar section is at the bottom
with the DHW top, CH middle and solar
bottom.


DHW is usually not as hot as CH, 65 versus anything upto 82, so an
unusual choice. Why choose to heat dhw to above its use temp, to extend
heat
capacity?


It is clear you don't understand the principle of heat banks.thermal
stores.
the DHW stored water is between 70-85C to instantly heat the incoming
water.

What is clear is you didnt fully describe
your proposed system.

I said thermal stopre and heat abnk. I can't get any clearer. If don't
understand the principle then....

Now we know which body of water
is in the tank. And we also know that this
approach makes solar collection less
efficient,

You keep saying that without knowing what a thermal store is. Again, is is
not less efficient is it more efficient and controls that prioritise the use
of solar gained heat are in place.

which is why I had initially guessed
you had the DHW in the tank, being drawn off at the
top for the taps. This would be more efficient.

Understand what I am describing. Draw it out and think it through.

No CH return to the solar section,
only the middle CH section.
Using a plate heat exchanger the
return from the DHW can be directly into
the bottom of the cylidner in the solar section.

return from DHW? whats that?
where does the plate exchanger
connect in your scheme (it has 4
connections)


It is clear you need to understand how they work. See
http://www.heatweb.com That gives good explanations.
No se sense in continuing until you understand,
you think about it and then form questions.

Either describe your setup or dont.

I did, re-read. Read again, draw it out and come back to clarify.

On Sun, 05 Mar 2006 13:26:11 +0000 someone who may be Peter Parry
wrote this:-

I want to use something on a barn conversion we might move to. Add more
insulation etc. is not an option as no loft etc. exists. The boiler is oil
fired but no indirect to HW tank so all HW is electric, E7 at night and full
price during the day. I can get to the tank from the roof line so I was
thinking solar HW would be helpful here.

You would be better replacing the existing system with one which
included hot water provision off the boiler.

It would certainly be worthwhile replacing the existing hot water
cylinder with a solar one, able to take heat from the boiler and
solar panels as necessary. With electric heating as a backup this
would give the best range of options. A heat bank is another option,
especially useful if there is a suitable source of fuel around, like
wood.

In the winter they can't provide enough energy,

Probably not, though it depends on the water usage and size of the
storage vessel, as well as the amount of light. However, that is not
really the point. What energy they do provide is energy that is not
provided in other ways.

in the summer you usually end up unable to use
all the energy collected as you simply don't use enough hot water.

That rather depends on the water usage and size of the storage
vessel.

failures in the panels, which are obviously
subject to a lot of temperature cycling, is not uncommon.

Assuming you are talking about flat plate panels, in a year they
cycle less than radiators. With evacuated tubes a tube may fail, but
this does not affect the other tubes.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

On Sat, 4 Mar 2006 19:27:54 -0000, "Doctor Drivel"
wrote:

No, you are correct. 5 years ago laughed at peopel who eco things and
bopasted they virtually no insulation and oil bills were low. How time
schange quickly. 5 years ago if you said gas would rise 25% in one swoop
they would have locked you up. Energy will "never" get cheaper.

It will, given enough time. For instance when the
Iranians/Chinese/Indians start exporting their miniature nuclear
reactor technology giving an all in one solution that never needs
refueling for 100 years, yet provides 40 litres a minute of hot water
at delta T 55 deg C and 500kW output for the radiators, you'll be able
to strip out all that expensive insulation and leave the windows open
all year round.

Hacksaws will have to be banned though - just in case anyone decides
to replumb the cooling circuit.


--

"Matt" aka Lord Hall wrote in message
...
On Sat, 4 Mar 2006 19:27:54 -0000, "Doctor Drivel"
wrote:

No, you are correct. 5 years ago they
laughed at people who eco'd things and
boasted they had virtually no insulation
and oil bills were low. How time has
change quickly. 5 years ago if you
said gas would rise 25% in one swoop
they would have locked you up. Energy
will "never" get cheaper.

It will, given enough time.

Lord Hall, you are guessing.

** snip Lord Hall babbling and dreaming of a nuclear powered Makita**

The message
from Matt contains these words:

It will, given enough time. For instance when the
Iranians/Chinese/Indians start exporting their miniature nuclear
reactor technology giving an all in one solution that never needs
refueling for 100 years, yet provides 40 litres a minute of hot water
at delta T 55 deg C and 500kW output for the radiators, you'll be able
to strip out all that expensive insulation and leave the windows open
all year round.

And inglenuke!

--
Skipweasel
Pay no attention to the man behind the curtain.

Matt wrote:
On Sat, 4 Mar 2006 19:27:54 -0000, "Doctor Drivel"
wrote:

No, you are correct. 5 years ago laughed at peopel who eco things and
bopasted they virtually no insulation and oil bills were low. How time
schange quickly. 5 years ago if you said gas would rise 25% in one swoop
they would have locked you up. Energy will "never" get cheaper.

It will, given enough time. For instance when the
Iranians/Chinese/Indians start exporting their miniature nuclear
reactor technology giving an all in one solution that never needs
refueling for 100 years, yet provides 40 litres a minute of hot water
at delta T 55 deg C and 500kW output for the radiators, you'll be able
to strip out all that expensive insulation and leave the windows open
all year round.

Hacksaws will have to be banned though - just in case anyone decides
to replumb the cooling circuit.


Alt energies keep getting cheaper and cheaper per watt as the
technology improves. At some point they will become cheaper than oil
and gas... and keep getting cheaper. Our future is one of plantiful
energy at low cost. How long it wll take to get there no-one knows, and
we probably will have to go through a period of steep costs first. I
suggest this is a more realistic long term forecast than the popular
never-have-it-so-good-again predictions.


NT

wrote in message
oups.com...
Matt wrote:
On Sat, 4 Mar 2006 19:27:54 -0000, "Doctor Drivel"
wrote:

No, you are correct. 5 years ago laughed at peopel who eco things and
bopasted they virtually no insulation and oil bills were low. How time
schange quickly. 5 years ago if you said gas would rise 25% in one
swoop
they would have locked you up. Energy will "never" get cheaper.

It will, given enough time. For instance when the
Iranians/Chinese/Indians start exporting their miniature nuclear
reactor technology giving an all in one solution that never needs
refueling for 100 years, yet provides 40 litres a minute of hot water
at delta T 55 deg C and 500kW output for the radiators, you'll be able
to strip out all that expensive insulation and leave the windows open
all year round.

Hacksaws will have to be banned though - just in case anyone decides
to replumb the cooling circuit.


Alt energies keep getting cheaper and cheaper per watt as the
technology improves. At some point they will become cheaper than oil
and gas... and keep getting cheaper. Our future is one of plantiful
energy at low cost. How long it wll take to get there no-one knows, and
we probably will have to go through a period of steep costs first. I
suggest this is a more realistic long term forecast than the popular
never-have-it-so-good-again predictions.

How Mr Parry can say that solar DHW heater don't pay for themselves over 20
years is mystifying. He must have had a very inefficient system. DIYing
it, they can pay for themselves in about 3 to 5 years. The more energy
costs rise along the way, the quicker the payback.

On Mon, 6 Mar 2006 14:29:58 -0000, "Doctor Drivel"
wrote:


How Mr Parry can say that solar DHW heater don't pay for themselves over 20
years is mystifying.

I have no doubt you find it so. It involves measurement and
recording of information - techniques you do not appear to have any
familiarity with.

--
Peter Parry.
http://www.wpp.ltd.uk/

"Peter Parry" wrote in message
...
On Mon, 6 Mar 2006 14:29:58 -0000, "Doctor Drivel"
wrote:


How Mr Parry can say that solar DHW heater don't pay for themselves over
20
years is mystifying.

I have no doubt you find it so. It involves measurement and
recording of information - techniques you do not appear to have any
familiarity with.

You are the "only" one who comes out with such allegations. Everyone else
seem to make them work properly and make back the cost in fraction of that
time.

On Mon, 06 Mar 2006 18:49:06 +0000, Peter Parry wrote:

On Mon, 6 Mar 2006 14:29:58 -0000, "Doctor Drivel"
wrote:


How Mr Parry can say that solar DHW heater don't pay for themselves over 20
years is mystifying.

I have no doubt you find it so. It involves measurement and
recording of information - techniques you do not appear to have any
familiarity with.

Putting the question the other way around, could you say what the total
installed price for a marginally justified system would be - with a 20
year payback say.

If you'd payed a lot (£2,000 say) for the system then I have no doubt
you'd not recover the cost. What might be the threshhold?


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Peter Parry
saying something like:

On Sat, 04 Mar 2006 13:51:44 +0000, Douglas de Lacey
wrote:


http://www.sustainable-girton.org.uk/pv/ gives a few figures on a new PV
installation, which in *February* produced 2/3 of the owner's
consumption. On good days it made 3.3Kw.

"The total cost was large,...If the predictions are correct, these
costs will be paid back in around 24 years"

Solar water heating may be marginal but solar pv is a wonderful way
of wasting money.

I don't see how. Sure, if you buy factory-made panels and all the
necessary pro stuff and pay for the installation.

This is a DIY group. Building panels from base materials and feeding a
pre-heat cylinder works out at less than a couple of hundred quid if you
DIY the whole thing from salvaged materials.

In my own situation, I have several suitable sized radiators and
double-glazing units which will be pressed into a different role from
their intended one. I have a few used-but-good hot cylinders and the
perfect position upstairs for a gravity solar system fed by 3 or 4
panels at ground level.

I don't expect it to work miracles, but I do expect it to work a bit -
enough to cut the cost of electrically heating water by at least a third
and probably half.
--

Dave

This thread is from uk.diy, and is kinda relevant for a.e.h too.


Ed Sirett wrote:

Putting the question the other way around, could you say what the total
installed price for a marginally justified system would be - with a 20
year payback say.

If you'd payed a lot (£2,000 say) for the system then I have no doubt
you'd not recover the cost. What might be the threshhold?


Good question. I'll have a go.

Lets say it saves £20 a year heating dhw only.
Lets say we want it to break even after 10 years, interest is 5% and we
optimistically ignore the risk of system failure, underperformance or
repair for the moment.

A system that does this in 10 years is worth paying £157 for now.

From this emerges one clear conclusion: we need either a lot more
saving or a lot less cost than commercial solar dhw systems deliver.

If one got a bit desperate and justified a 20 year payback, system
value would rise to £251. But I dont think thats justifiable in truth,
nor is the extra spend allowance very significant. Either will make a
cheap system and nothing more.


Now, since almost all solar dhw setups fail miserably to pay their way,
lets see how low cost we can get. Start with a dirt cheap direct
drain-down system for summer use only. This preheats the header tank,
which of course must be hot water safe in this design. That rules out
use of plastic header tanks where already fitted. Metal headers are ok,
a plastic one would need replacement.


Collector and loft piping:
100' garden hosepipe: £20
sheet of green house polythene: £? Lets say we use a £1 poundland
plastic patio table cover set
4x8 sheet 7mm WBP ply £? rough guess £5
stainless roof fixings £? guess £5
black paint £1

CH pump £30

loft piping insulation: cardboard and/or rags £0, sellotape to hold in
place temporarily £0.50, string to fix it permanently £0.50.
header tank insulation: as above, no more spend needed
connecting 2 pipe ends to header tank: £2
1mm cable from lighting jbox to pump £1-2
FCU & pattress £2
panel thermostat, bimetal, £5

HW header tank if metal one not already present: £ not sure, and will
vary according to source

Now, if you had to buy all the above new, total cost is:
£73 + maybe a new header tank

The numbers look quite a bit better if you've got various bits lying
around already, or can use chuckouts to build it from. Then it might
actually be worth the 2 days work.

But given the low value overall of such systems, I dont think this is
the way to go. More sensible to go for a system that delivers much
more, such as flat panel solar space heating, which is cheaper, easier,
requires no roof access, and delivers more payback.

Solar flat panel space heating is little more than a frame, polythene,
black mesh cloth and holes in the wall. I'll let someone to play with
the numbers if they wish.


NT

Ed Sirett wrote in message
news
How Mr Parry can say that solar DHW heater don't pay for themselves over
20
years is mystifying.

I have no doubt you find it so. It involves measurement and
recording of information - techniques you do not appear to have any
familiarity with.

Putting the question the other way around, could you say what the total
installed price for a marginally justified system would be - with a 20
year payback say.

If you'd payed a lot (£2,000 say) for the system then I have no doubt
you'd not recover the cost. What might be the threshhold?



That's still a moving target, how much will energy prices have to increase
before we can't afford NOT to fit some type of solar heating.



-

On Tue, 07 Mar 2006 00:31:08 GMT, "Mark" wrote:


Ed Sirett wrote in message
news
How Mr Parry can say that solar DHW heater don't pay for themselves over
20
years is mystifying.

I have no doubt you find it so. It involves measurement and
recording of information - techniques you do not appear to have any
familiarity with.

Putting the question the other way around, could you say what the total
installed price for a marginally justified system would be - with a 20
year payback say.

If you'd payed a lot (£2,000 say) for the system then I have no doubt
you'd not recover the cost. What might be the threshhold?



That's still a moving target, how much will energy prices have to increase
before we can't afford NOT to fit some type of solar heating.


The market will decide that. Energy prices will increase. Volumes
of solar heating products may well increase and more manufacturers
will enter the market, increasing competition and reducing purchase
price. There will be more people out there fitting them.

I'll give you an example. It's very common in Israel to see solar
water heating systems on the roofs of houses and apartment buildings
consisting of a solar panel propped up on a typically flat roof and a
header tank on a stand. Frankly they look extremely ugly, but Israel
is not a country where these kind of aesthetics are high on the
agenda.

These systems cost a few hundred US dollars and are not very
sophisticated because they don't need to be - there is plenty of
energy to heat much of the hot water used for most of the year.

People buy them because they are cheap, they make a substantial saving
in that climate and because they don't care about the appearance.

That's it. Simple as that.


--

..andy

Mark wrote:
Ed Sirett wrote in message

If you'd payed a lot (£2,000 say) for the system then I have no doubt
you'd not recover the cost. What might be the threshhold?

That's still a moving target, how much will energy prices have to increase
before we can't afford NOT to fit some type of solar heating.

another good question, and another bastion of solar DHW support. So,
lets find out:


At todays prices a £2000 commercial system saves in the region of £20
per annum on hot water bills. This is in the region of a tenth the
amount that woud be needed for the unit to eventually pay its install
cost.

To pay back £2000 @ 5% over x years would require a yearly payback of
- calculator time -

over 10 years: £254.52 per annum
over 15 years: £189.84 per annum
over 20 years: £158.40 per annum
over 25 years: £140.28 per annum
over 50 years: £117.6 per annum
over 100 years: £100.68 per annum
infinity years: £100 per annum.


So, even if all such systems lasted the entire life of the universe
with never a need for repair, the £2000 spend would be almost entirely
lost. In no sense are these systems an investment, whether short term,
medium term, long term, or even infinite term.


Lastly, how much do energy prices need to rise to make these pay their
way? Well, if an infinite amount of time to pay off their cost is
acceptable, and there is zero risk of ever needing repair or
decommissioning, then current energy prices would need to rise to
roughly around 5x the present price. Since there are already various
renewable energy technologies up and running, with huge implementation
capacity available, at a fraction of 5x current oil based costs, this
paying-their-way scenario will never happen. They can never pay off
their cost, not even applying the most extreme and unrealistic
optimism.

The lie is dead.


NT

wrote in message
oups.com...
Mark wrote:
Ed Sirett wrote in message

If you'd payed a lot (£2,000 say) for the system then I have no doubt
you'd not recover the cost. What might be the threshhold?

That's still a moving target, how much
will energy prices have to increase
before we can't afford NOT to fit some
type of solar heating.

another good question, and another
bastion of solar DHW support. So,
lets find out:

At todays prices a £2000 commercial system saves in the region of £20
per annum on hot water bills. This is in the region of a tenth the
amount that woud be needed for the unit to eventually pay its install
cost.

To pay back £2000 @ 5% over x years would require a yearly payback of
- calculator time -

over 10 years: £254.52 per annum
over 15 years: £189.84 per annum
over 20 years: £158.40 per annum
over 25 years: £140.28 per annum
over 50 years: £117.6 per annum
over 100 years: £100.68 per annum
infinity years: £100 per annum.


Look at the 10 years figure. That doers not take into account that energy
may be twice as much in 10 years and has risen steadily along the way. The
payback calcs are more complex than this simplistic view.

That is having one installed commercially. DIYing the installation will
payback rather quicker. Also saving £20 per year in DHW bills is rather on
the conservative side. I know of a few solar systems that produce 2/3 to 3/4
of all DHW needs, and these must save far more than £20 per right now. If a
solar system is DIYed, is large covering most of the roof, or all of it, and
this energy gained is used to supplement heating too, then the matter may be
more beneficial again. Solar heating is more feasible in cold northerly
Scotland, as they have a heating season 9 months of the year, so any free
energy gained is a bonus at any time. And as free energy is being collected
for 9 months, more of it is being captured over the year. It all adds up.

wrote:
This thread is from uk.diy, and is kinda relevant for a.e.h too.


Ed Sirett wrote:

Putting the question the other way around, could you say what the total
installed price for a marginally justified system would be - with a 20
year payback say.

If you'd payed a lot (£2,000 say) for the system then I have no doubt
you'd not recover the cost. What might be the threshhold?


Good question. I'll have a go.

Lets say it saves £20 a year heating dhw only.
Lets say we want it to break even after 10 years, interest is 5% and we
optimistically ignore the risk of system failure, underperformance or
repair for the moment.

A system that does this in 10 years is worth paying £157 for now.

Since you can get about 20 quid interest a year on about 800 quid, if
you have the 800 quid, and it will save 20 quid a year, its worthwhile
spending that on solar heating.

Which is different from £157.

The difference being the bid/offer spread on renting money ;-)

Mark wrote:
Ed Sirett wrote in message
news
How Mr Parry can say that solar DHW heater don't pay for themselves over
20
years is mystifying.
I have no doubt you find it so. It involves measurement and
recording of information - techniques you do not appear to have any
familiarity with.
Putting the question the other way around, could you say what the total
installed price for a marginally justified system would be - with a 20
year payback say.

If you'd payed a lot (£2,000 say) for the system then I have no doubt
you'd not recover the cost. What might be the threshhold?



That's still a moving target, how much will energy prices have to increase
before we can't afford NOT to fit some type of solar heating.


Indeed. We ave a crude system. When the sun shines we open the curtains.
When the sky goes dark we close them.

I estimate this nets about 1000 a year solar gain.



-

On Mon, 06 Mar 2006 22:53:09 +0000, Grimly Curmudgeon
wrote:


Solar water heating may be marginal but solar pv is a wonderful way
of wasting money.

I don't see how. Sure, if you buy factory-made panels and all the
necessary pro stuff and pay for the installation.

I'm not sure DIY construction of solar photovoltaic panels is really
going to catch on :-).

This is a DIY group. Building panels from base materials and feeding a
pre-heat cylinder works out at less than a couple of hundred quid if you
DIY the whole thing from salvaged materials.

I've helped build such a system for warming a swimming pool and it
works quite adequately - it's also very large and pretty hideous.
Where we built it it was possible to hide it behind a large hedge but
not many people have a farm to play with.


--
Peter Parry.
http://www.wpp.ltd.uk/

On Tue, 07 Mar 2006 11:10:48 +0000 The Natural Philosopher wrote :
Since you can get about 20 quid interest a year on about 800 quid,
if you have the 800 quid, and it will save 20 quid a year, its
worthwhile spending that on solar heating.

No because if you leave the money in the bank you still have the £800.
If you spend it on solar heating then you have a solar heating system,
but I have seen no evidence that you are likely to get more than a
fraction of this back when you come to sell your property. So what
you've really done is spend the best part of £800 on an annuity that
will pay you £20 per year (increasing by the rate of fuel inflation)
for the rest of the period you stay in that house.

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
Free SEDBUK boiler database browser http://www.sda.co.uk/qsedbuk.htm
[Latest version QSEDBUK 1.12 released 8 Dec 2005]