I know this has been done to death previously but I am about to visit a
friend who is contemplating a *grand design*.

National grid want their usual arm and 3 legs to connect so alternative
sources are under consideration. The site is on a steep slope so a
basement thermal store would be do-able.

Very roughly, how large a store of water would be required to provide
dhw and under floor heating for say 200m2, constructed to something
better than current regs.?

The idea would be to heat this with off peak electricity possibly
supplemented with power from a PV array. Nice unshaded South facing
roof.

I suppose tank life and replaceability is a consideration.

regards
--
Tim Lamb

In message , Tim Lamb
writes
I know this has been done to death previously but I am about to visit a
friend who is contemplating a *grand design*.

National grid want their usual arm and 3 legs to connect so alternative
sources are under consideration. The site is on a steep slope so a
basement thermal store would be do-able.

Very roughly, how large a store of water would be required to provide
dhw and under floor heating for say 200m2, constructed to something
better than current regs.?

The idea would be to heat this with off peak electricity possibly
supplemented with power from a PV array. Nice unshaded South facing
roof.

I suppose tank life and replaceability is a consideration.

Thinking on.... I suppose dhw would be best kept separate as you don't
want to heat the big store all summer.

regards

--
Tim Lamb

On Thu, 22 Sep 2011 21:45:38 +0100, Tim Lamb
wrote:

In message , Tim Lamb
writes
I know this has been done to death previously but I am about to visit a
friend who is contemplating a *grand design*.

National grid want their usual arm and 3 legs to connect so alternative
sources are under consideration. The site is on a steep slope so a
basement thermal store would be do-able.

Very roughly, how large a store of water would be required to provide
dhw and under floor heating for say 200m2, constructed to something
better than current regs.?

The idea would be to heat this with off peak electricity possibly
supplemented with power from a PV array. Nice unshaded South facing
roof.

I suppose tank life and replaceability is a consideration.

Thinking on.... I suppose dhw would be best kept separate as you don't
want to heat the big store all summer.

regards

I would have thought that you *would* want to heat the big store all
summer. (Isn't that when the most energy is collectable?) But using solar
heated water rather than electricity.

--
Rod

On Thu, 22 Sep 2011 21:41:34 +0100, Tim Lamb wrote:

Very roughly, how large a store of water would be required to provide
dhw and under floor heating for say 200m2, constructed to something
better than current regs.?

If you get enough insulation in you need aircon to keep the interior
at sensible temperatures. Just from the waste heat from appliances
and the humans.

The idea would be to heat this with off peak electricity ...

Thought you said NG wanted body parts for a connection. So implying
an off grid place.

possibly supplemented with power from a PV array.

Wouldn't it be better to use solar thermal directly rather than go
through PV's that have a much lower effciency?

The thermal store going in here will have as heat inputs, solar
thermal sized for summer DHW, wood burner (something around 8kW flat
out to water), existing oil boiler and immersion heater. The store
will be something around 250 to 300l but that is really sized for
getting maximum benefit of the solar thermal during the summer. A
store sized to provide space heating from itself would require a huge
solar thermal system to get it hot even in summer so you'd need to
use other heat sources just for DHW and you don't need space heating
in summer...

If you do want a store big enough to handle space heating you need to
do the heat loss calculations for the building then it's simple maths
to find out how many litres of water you need to hold that amount of
energy with say a 20C temp range for the store (80C max to 60C min).

--
Cheers
Dave.

On 22/09/2011 21:41, Tim Lamb wrote:
I know this has been done to death previously but I am about to visit a
friend who is contemplating a *grand design*.

National grid want their usual arm and 3 legs to connect so alternative
sources are under consideration. The site is on a steep slope so a
basement thermal store would be do-able.

Very roughly, how large a store of water would be required to provide
dhw and under floor heating for say 200m2, constructed to something
better than current regs.?

The idea would be to heat this with off peak electricity possibly
supplemented with power from a PV array. Nice unshaded South facing roof.

I suppose tank life and replaceability is a consideration.

Do it in energy terms, and its easy enough to work out a ballpark.

Take a cold day, and work out the heatloss from the house making
allowances for air changes etc and the level of insulation[1]. You will
come out with a figure of a few kW no doubt. Multiply that up and
convert to Joules you need to feed in to maintain the temperature inside
for a day. Work out your energy demands for hot water, and add to the
total. You can knock some off for heat wasted by appliances and people.
Once you have a figure, and a useful store temperature differential of
say 40 degrees (i.e. 80 deg C actual storage temperature). Divide that
and the SHC of water into your energy requirement to come out with a
number of litres.

(the answer will be "lots" unless you can get the energy requirement for
heating down to very low worst case figures)

[1] http://wiki.diyfaq.org.uk/index.php?title=Heat_loss



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 22/09/2011 21:45, Tim Lamb wrote:
In message , Tim Lamb
writes
I know this has been done to death previously but I am about to visit
a friend who is contemplating a *grand design*.

National grid want their usual arm and 3 legs to connect so
alternative sources are under consideration. The site is on a steep
slope so a basement thermal store would be do-able.

Very roughly, how large a store of water would be required to provide
dhw and under floor heating for say 200m2, constructed to something
better than current regs.?

The idea would be to heat this with off peak electricity possibly
supplemented with power from a PV array. Nice unshaded South facing roof.

I suppose tank life and replaceability is a consideration.

Thinking on.... I suppose dhw would be best kept separate as you don't
want to heat the big store all summer.

Big tall stores will stratify quite nicely...


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In message o.uk, Dave
Liquorice writes
On Thu, 22 Sep 2011 21:41:34 +0100, Tim Lamb wrote:

Very roughly, how large a store of water would be required to provide
dhw and under floor heating for say 200m2, constructed to something
better than current regs.?

If you get enough insulation in you need aircon to keep the interior
at sensible temperatures. Just from the waste heat from appliances
and the humans.

The idea would be to heat this with off peak electricity ...

Thought you said NG wanted body parts for a connection. So implying
an off grid place.
Electricity connected, gas next door.

possibly supplemented with power from a PV array.

Wouldn't it be better to use solar thermal directly rather than go
through PV's that have a much lower effciency?

Umm.. presumably target temperature would need to be quite high to
maximise the offtake heat. PV through an immersion would always provide
useful heat whereas direct solar?

The thermal store going in here will have as heat inputs, solar
thermal sized for summer DHW, wood burner (something around 8kW flat
out to water), existing oil boiler and immersion heater. The store
will be something around 250 to 300l but that is really sized for
getting maximum benefit of the solar thermal during the summer. A
store sized to provide space heating from itself would require a huge
solar thermal system to get it hot even in summer so you'd need to
use other heat sources just for DHW and you don't need space heating
in summer...

Yes. No hope of wood burner. Oil could be done but better to pay for a
gas supply.

If you do want a store big enough to handle space heating you need to
do the heat loss calculations for the building then it's simple maths
to find out how many litres of water you need to hold that amount of
energy with say a 20C temp range for the store (80C max to 60C min).

I think you could go lower for an underfloor system if dhw was separate.

regards


--
Tim Lamb

In message , John
Rumm writes
On 22/09/2011 21:41, Tim Lamb wrote:
I know this has been done to death previously but I am about to visit a
friend who is contemplating a *grand design*.

National grid want their usual arm and 3 legs to connect so alternative
sources are under consideration. The site is on a steep slope so a
basement thermal store would be do-able.

Very roughly, how large a store of water would be required to provide
dhw and under floor heating for say 200m2, constructed to something
better than current regs.?

The idea would be to heat this with off peak electricity possibly
supplemented with power from a PV array. Nice unshaded South facing roof.

I suppose tank life and replaceability is a consideration.

Do it in energy terms, and its easy enough to work out a ballpark.

Take a cold day, and work out the heatloss from the house making
allowances for air changes etc and the level of insulation[1]. You will
come out with a figure of a few kW no doubt. Multiply that up and
convert to Joules you need to feed in to maintain the temperature
inside for a day. Work out your energy demands for hot water, and add
to the total. You can knock some off for heat wasted by appliances and
people. Once you have a figure, and a useful store temperature
differential of say 40 degrees (i.e. 80 deg C actual storage
temperature). Divide that and the SHC of water into your energy
requirement to come out with a number of litres.

(the answer will be "lots" unless you can get the energy requirement
for heating down to very low worst case figures)

Yes. I was just hoping for a ball park figure to see whether the concept
is practical.

[1] http://wiki.diyfaq.org.uk/index.php?title=Heat_loss

right. Ta.

I'll see if her architect has come up with some drawings for rough
dimensions.

regards
--
Tim Lamb

On Thu, 22 Sep 2011 22:24:52 +0100, John Rumm wrote:

(the answer will be "lots" unless you can get the energy requirement for
heating down to very low worst case figures)

With a store temp range of 20C you need about 1000l for every 90MJ
(25kWhr) of energy.

--
Cheers
Dave.

In message o.uk, Dave
Liquorice writes
On Thu, 22 Sep 2011 22:24:52 +0100, John Rumm wrote:

(the answer will be "lots" unless you can get the energy requirement for
heating down to very low worst case figures)

With a store temp range of 20C you need about 1000l for every 90MJ
(25kWhr) of energy.

Ah!

So if the store temp could drop to say 30C (underfloor heating)
something like 60kWhr/1000l.

2 or 3 cu.m in a basement ought to be possible.

regards


--
Tim Lamb

Tim Lamb wrote:
In message , John Rumm
writes
On 22/09/2011 21:41, Tim Lamb wrote:
I know this has been done to death previously but I am about to visit a
friend who is contemplating a *grand design*.

National grid want their usual arm and 3 legs to connect so alternative
sources are under consideration. The site is on a steep slope so a
basement thermal store would be do-able.

Very roughly, how large a store of water would be required to provide
dhw and under floor heating for say 200m2, constructed to something
better than current regs.?

The idea would be to heat this with off peak electricity possibly
supplemented with power from a PV array. Nice unshaded South facing roof.

I suppose tank life and replaceability is a consideration.

Do it in energy terms, and its easy enough to work out a ballpark.

Take a cold day, and work out the heatloss from the house making
allowances for air changes etc and the level of insulation[1]. You will
come out with a figure of a few kW no doubt. Multiply that up and
convert to Joules you need to feed in to maintain the temperature
inside for a day. Work out your energy demands for hot water, and
add to the total. You can knock some off for heat wasted by
appliances and people. Once you have a figure, and a useful store
temperature differential of say 40 degrees (i.e. 80 deg C actual storage
temperature). Divide that and the SHC of water into your energy
requirement to come out with a number of litres.

(the answer will be "lots" unless you can get the energy requirement
for heating down to very low worst case figures)

Yes. I was just hoping for a ball park figure to see whether the concept is practical.

[1] http://wiki.diyfaq.org.uk/index.php?title=Heat_loss

right. Ta.

I'll see if her architect has come up with some drawings for rough dimensions.

We have a 300 litre thermal store with solar thermal panels, a log burner
and an lpg boiler. There's also an (unused) 3kw immersion heater. It's too
soon to give costs - we need to run it through winter. However monitoring
the thermometer shows that the store stays above 60C through the day even
when used for both underfloor heating and six showers per day.

Ambient temperatures have been above 20C so far. The floor area is 280 sq
m.

The store has thermostatic mixers on the hot water and UFH circuits. These
mix water from top and bottom of the store and ensure that the temperature
in the store is maintained.

On 22/09/2011 23:43, Tim Lamb wrote:
In message o.uk, Dave
Liquorice writes
On Thu, 22 Sep 2011 22:24:52 +0100, John Rumm wrote:

(the answer will be "lots" unless you can get the energy requirement for
heating down to very low worst case figures)

With a store temp range of 20C you need about 1000l for every 90MJ
(25kWhr) of energy.

Ah!

So if the store temp could drop to say 30C (underfloor heating)
something like 60kWhr/1000l.

2 or 3 cu.m in a basement ought to be possible.

If you store at 80, and can drop to 30, then that gives you:

3000 x (80 - 30) x 4200 = 630MJ to play with, which is the equivalent of
a 25kW boiler running for 7 hours. Probably way more than you need...


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 22/09/2011 22:51, Tim Lamb wrote:

If you do want a store big enough to handle space heating you need to
do the heat loss calculations for the building then it's simple maths
to find out how many litres of water you need to hold that amount of
energy with say a 20C temp range for the store (80C max to 60C min).

I think you could go lower for an underfloor system if dhw was separate.

You can run the UFH from lower taping on the store than than those used
for the DHW. Alternatively use blending valves to mix water from
different levels to achieve the desired output temperature.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In message , John
Rumm writes
On 22/09/2011 22:51, Tim Lamb wrote:

If you do want a store big enough to handle space heating you need to
do the heat loss calculations for the building then it's simple maths
to find out how many litres of water you need to hold that amount of
energy with say a 20C temp range for the store (80C max to 60C min).

I think you could go lower for an underfloor system if dhw was separate.

You can run the UFH from lower taping on the store than than those used
for the DHW. Alternatively use blending valves to mix water from
different levels to achieve the desired output temperature.

er.. Wouldn't you just blend stored hot water with returning heating
water.

I understand what you are saying about stratification but if the store
needs to be the size of a young swimming pool, tall/thin is not going to
happen.

I am simply trying to get hold of how practical such a system might be.

regards



--
Tim Lamb

In message

g, Steve Firth writes
Tim Lamb wrote:
In message , John Rumm
writes
On 22/09/2011 21:41, Tim Lamb wrote:
I know this has been done to death previously but I am about to visit a
friend who is contemplating a *grand design*.

National grid want their usual arm and 3 legs to connect so alternative
sources are under consideration. The site is on a steep slope so a
basement thermal store would be do-able.

Very roughly, how large a store of water would be required to provide
dhw and under floor heating for say 200m2, constructed to something
better than current regs.?

The idea would be to heat this with off peak electricity possibly
supplemented with power from a PV array. Nice unshaded South facing roof.

I suppose tank life and replaceability is a consideration.

Do it in energy terms, and its easy enough to work out a ballpark.

Take a cold day, and work out the heatloss from the house making
allowances for air changes etc and the level of insulation[1]. You will
come out with a figure of a few kW no doubt. Multiply that up and
convert to Joules you need to feed in to maintain the temperature
inside for a day. Work out your energy demands for hot water, and
add to the total. You can knock some off for heat wasted by
appliances and people. Once you have a figure, and a useful store
temperature differential of say 40 degrees (i.e. 80 deg C
actual storage
temperature). Divide that and the SHC of water into your energy
requirement to come out with a number of litres.

(the answer will be "lots" unless you can get the energy requirement
for heating down to very low worst case figures)

Yes. I was just hoping for a ball park figure to see whether the
concept is practical.

[1] http://wiki.diyfaq.org.uk/index.php?title=Heat_loss

right. Ta.

I'll see if her architect has come up with some drawings for rough
dimensions.

We have a 300 litre thermal store with solar thermal panels, a log burner
and an lpg boiler. There's also an (unused) 3kw immersion heater. It's too
soon to give costs - we need to run it through winter. However monitoring
the thermometer shows that the store stays above 60C through the day even
when used for both underfloor heating and six showers per day.

Ambient temperatures have been above 20C so far. The floor area is 280 sq
m.

The store has thermostatic mixers on the hot water and UFH circuits. These
mix water from top and bottom of the store and ensure that the temperature
in the store is maintained.

Is this Hampshire or Italy? The site in question is a fairly exposed bit
of East coast Suffolk:-)

300l sounds tiny so your winter results should be interesting.

Last Autumn we rented a *cabin* in Suffolk which had a wet underfloor
system and a store similar in size to yours heated using off peak. As
many have said, underfloor is slow and not really suited to interval
occupation. Once up to temperature, it seemed OK but I don't know how
much full price power was used to boost the store output.

regards

--
Tim Lamb

In message , John
Rumm writes
On 22/09/2011 23:43, Tim Lamb wrote:
In message o.uk, Dave
Liquorice writes
On Thu, 22 Sep 2011 22:24:52 +0100, John Rumm wrote:

(the answer will be "lots" unless you can get the energy requirement for
heating down to very low worst case figures)

With a store temp range of 20C you need about 1000l for every 90MJ
(25kWhr) of energy.

Ah!

So if the store temp could drop to say 30C (underfloor heating)
something like 60kWhr/1000l.

2 or 3 cu.m in a basement ought to be possible.

If you store at 80, and can drop to 30, then that gives you:

3000 x (80 - 30) x 4200 = 630MJ to play with, which is the equivalent
of a 25kW boiler running for 7 hours. Probably way more than you need...

OK chaps.

Lets pause this. I'll report back when I have some proper figures.

regards



--
Tim Lamb

On Sep 22, 9:41*pm, Tim Lamb wrote:
I know this has been done to death previously but I am about to visit a
friend who is contemplating a *grand design*.

National grid want their usual arm and 3 legs to connect so alternative
sources are under consideration. The site is on a steep slope so a
basement thermal store would be do-able.

Very roughly, how large a store of water would be required to provide
dhw and under floor heating for say 200m2, constructed to something
better than current regs.?

The idea would be to heat this with off peak electricity possibly
supplemented with power from a PV array. Nice unshaded South facing
roof.

I suppose tank life and replaceability is a consideration.

regards
--
Tim Lamb

I have seen a design that use the "light bulb" shaped septic tanks set
in a periphally insulated concrete whole house sized block.. This use
solar heat panels.
The advantage of using solar electric would be that they function at
very low light levels and still deliver normal voltage power long
after the solar heat panels are too cool.

The major problem is the inverter runs in parallel with the grid and
you don't want to inadvertently be using grid power. You need a
device to somehow prevent this and I can't think of one that's cheap
or could be home made.

As for sizing, it's a how long is a piece of string job. The main
problem with any thermal store is keeping the heat in. Actually a
bigger issue than how big.

The size really depends on the space available when it comes down to
brass tacks. You can store a lot of heat by simple massive
construction of the building. This is what I have done with my
house. I also have massive insulation. I do not need any heating for
99%of the time.

These high tech solutions usually fail, I have seen it several times.

http://www.flickr.com/photos/ara-chl...7627608971673/

harry wrote:
[snip]
The advantage of using solar electric would be that they function at
very low light levels and still deliver normal voltage power long
after the solar heat panels are too cool.

This is complete and utter ****. The efficiency of photovoltaics is less
than that of decent solar thermal arrays.

In message

g, Steve Firth writes
harry wrote:
[snip]
The advantage of using solar electric would be that they function at
very low light levels and still deliver normal voltage power long
after the solar heat panels are too cool.

This is complete and utter ****. The efficiency of photovoltaics is less
than that of decent solar thermal arrays.

Yebbut.

If the thermal store is hot after over night off peak how much useful
heat would you get out of solar thermal?

regards

--
Tim Lamb

In message
,
harry writes
On Sep 22, 9:41*pm, Tim Lamb wrote:
I know this has been done to death previously but I am about to visit a
friend who is contemplating a *grand design*.

National grid want their usual arm and 3 legs to connect so alternative
sources are under consideration. The site is on a steep slope so a
basement thermal store would be do-able.

Very roughly, how large a store of water would be required to provide
dhw and under floor heating for say 200m2, constructed to something
better than current regs.?

The idea would be to heat this with off peak electricity possibly
supplemented with power from a PV array. Nice unshaded South facing
roof.

I suppose tank life and replaceability is a consideration.

regards
--
Tim Lamb

I have seen a design that use the "light bulb" shaped septic tanks set
in a periphally insulated concrete whole house sized block.. This use
solar heat panels.
The advantage of using solar electric would be that they function at
very low light levels and still deliver normal voltage power long
after the solar heat panels are too cool.

The major problem is the inverter runs in parallel with the grid and
you don't want to inadvertently be using grid power. You need a
device to somehow prevent this and I can't think of one that's cheap
or could be home made.

I suppose a photocell controlling the immersion heater would do.

As for sizing, it's a how long is a piece of string job. The main
problem with any thermal store is keeping the heat in. Actually a
bigger issue than how big.

The size really depends on the space available when it comes down to
brass tacks. You can store a lot of heat by simple massive
construction of the building. This is what I have done with my
house. I also have massive insulation. I do not need any heating for
99%of the time.

I am sure the design will incorporate adequate insulation. I don't want
to go making waves about exotic heating systems if they are not
practical. Very large thermal stores would need future proofing to allow
replacement without major re-building work. The site slopes and I
envisage a basement accessed at rear ground level from the rear.

These high tech solutions usually fail, I have seen it several times.

I can see Steve managing his set up but I struggle a bit with the
thought of a late 60's widow and anything seriously complex.

http://www.flickr.com/photos/ara-chl...7627608971673/

regards

--
Tim Lamb

On Sep 23, 10:36*am, Steve Firth wrote:
harry wrote:

[snip]

The advantage of using solar electric would be that they function at
very low light levels and still deliver normal voltage power long
after the solar heat panels are too cool.

This is complete and utter ****. The efficiency of photovoltaics is less
than that of decent solar thermal arrays.

So it is nitwit. But it dleivers 240v electricity at low light levels
into any heat store, no matter how hot it is, long after the thermal
panel is running too cool to to do this.
**** for brains.

On Sep 23, 11:09*am, Tim Lamb wrote:
In message
,
harry writes





On Sep 22, 9:41*pm, Tim Lamb wrote:
I know this has been done to death previously but I am about to visit a
friend who is contemplating a *grand design*.

National grid want their usual arm and 3 legs to connect so alternative
sources are under consideration. The site is on a steep slope so a
basement thermal store would be do-able.

Very roughly, how large a store of water would be required to provide
dhw and under floor heating for say 200m2, constructed to something
better than current regs.?

The idea would be to heat this with off peak electricity possibly
supplemented with power from a PV array. Nice unshaded South facing
roof.

I suppose tank life and replaceability is a consideration.

regards
--
Tim Lamb

I have seen a design that use the "light bulb" shaped septic tanks set
in a periphally *insulated concrete whole house sized block.. This use
solar heat panels.
The advantage of using solar electric would be that they function at
very low light levels and still deliver normal voltage power long
after the solar heat panels are too cool.

The major problem is the inverter runs in parallel with the grid and
you don't want to inadvertently be using grid power. *You need a
device to somehow prevent this and I can't think of one that's cheap
or could be home made.

I suppose a photocell controlling the immersion heater would do.



As for sizing, it's a how long is a piece of string job. *The main
problem with any thermal store is keeping the heat in. *Actually a
bigger issue than how big.

The size really depends on the space available when it comes down to
brass tacks. * You can store a lot of heat by simple massive
construction of the building. *This is what I have done with my
house. *I also have massive insulation. I do not need any heating for
99%of the time.

I am sure the design will incorporate adequate insulation. I don't want
to go making waves about exotic heating systems if they are not
practical. Very large thermal stores would need future proofing to allow
replacement without major re-building work. The site slopes and I
envisage a basement accessed at rear ground level from the rear.



These high tech solutions usually fail, *I have seen it several times.

I can see Steve managing his set up but I struggle a bit with the
thought of a late 60's widow and anything seriously complex.



http://www.flickr.com/photos/ara-chl...7627608971673/

regards

--
Tim Lamb- Hide quoted text -

- Show quoted text -

The problem lies in the outside air temperature shoulder period.
This is the time of year when it' s too warm to need the house to be
heated but too cool to gather any more energy into a store that's
already hot.
(Unless by SolarPV. But the amount gathered in at this time of year
is quite small.)
About a month normally before the begining of the heating season.
In a month all your stored heat has leaked away.
So long term thermal stores are not practical.

Which is why I went for massive insulation of the house.

Tim Lamb wrote:
[snip]

I can see Steve managing his set up but I struggle a bit with the thought
of a late 60's widow and anything seriously complex.

Not much management to do. The control pack does it all.

Tim Lamb wrote:
In message
, Steve Firth writes
harry wrote:
[snip]
The advantage of using solar electric would be that they function at
very low light levels and still deliver normal voltage power long
after the solar heat panels are too cool.

This is complete and utter ****. The efficiency of photovoltaics is less
than that of decent solar thermal arrays.

Yebbut.

If the thermal store is hot after over night off peak how much useful
heat would you get out of solar thermal?

In our case enough to boil the tank, so we dont use off-peak. solar alone
is sufficient so far from April to September. In fact it's a bit too much
and a second thermal store is planned for next year. That one is likely to
be a tonne of water.

And yes this is in Italy. A separate system is planned for the barn/tractor
shed for washing down oil containers and sweaty tractor driver.

On Fri, 23 Sep 2011 00:21:05 +0100, John Rumm wrote:

With a store temp range of 20C you need about 1000l for every
90MJ
(25kWhr) of energy.

Ah!

So if the store temp could drop to say 30C (underfloor heating)
something like 60kWhr/1000l.

30C woould be a bit cool even for underfloor heating I'd have
thought. 40C minimum? Running the store down to that temp would also
mean you'd need something else for DHW. To get the required heat
transfer from the store to, on demand, hot water you need a
reasonable temperature differential between your max HW temp and the
store temp. HW would normally be at 50C or there abouts a 10C
differential means a minimum store temp of 60C...

--
Cheers
Dave.

On Thu, 22 Sep 2011 23:03:19 +0000 (UTC), Steve Firth wrote:

We have a 300 litre thermal store with solar thermal panels,

How big (sq m) are your solar thermal panels. Trying to get a handle
on what I'm being offered. I'm not convinced that a 250l store and
3.23m^2 (apperture) is big enough, we have plenty of roof space for
larger or extra panels.

We do have a space heating requirement even during the summer. The
current oil boiler normally only has a thermostat controlled holiday
from space heating duty for at most a month. This "summer" the total
number of single days it hasn't fired for heating is probably less
than seven...

--
Cheers
Dave.

In article , harry wrote:
On Sep 23, 10:36*am, Steve Firth wrote:
harry wrote:

The advantage of using solar electric would be that they function at
very low light levels and still deliver normal voltage power long
after the solar heat panels are too cool.

This is complete and utter ****. The efficiency of photovoltaics is less
than that of decent solar thermal arrays.

So it is nitwit. But it dleivers 240v electricity at low light levels
into any heat store, no matter how hot it is, long after the thermal
panel is running too cool to to do this.

Use a hybrid thermal-PV panel with the PV running a heat pump from low
temperature thermal panels into a higher temperature store.
(Apparently there are actually commercially available systems that do that.)

On Sep 22, 9:41*pm, Tim Lamb wrote:

I know this has been done to death previously but I am about to visit a
friend who is contemplating a *grand design*.

National grid want their usual arm and 3 legs to connect so alternative
sources are under consideration. The site is on a steep slope so a
basement thermal store would be do-able.

Very roughly, how large a store of water would be required to provide
dhw and under floor heating for say 200m2, constructed to something
better than current regs.?

The idea would be to heat this with off peak electricity possibly
supplemented with power from a PV array. Nice unshaded South facing
roof.

I suppose tank life and replaceability is a consideration.

regards

PV to heat is never worth doing. Solarthermal to heat is a fraction
the cost.


NT

On 23/09/2011 17:14, Dave Liquorice wrote:
On Fri, 23 Sep 2011 00:21:05 +0100, John Rumm wrote:

With a store temp range of 20C you need about 1000l for every
90MJ
(25kWhr) of energy.

Ah!

So if the store temp could drop to say 30C (underfloor heating)
something like 60kWhr/1000l.

30C woould be a bit cool even for underfloor heating I'd have
thought. 40C minimum? Running the store down to that temp would also
mean you'd need something else for DHW. To get the required heat

That's why they sometimes run the UFH from a lower tapping - so it leave
a reserve of hotter water for DHW purposes.

transfer from the store to, on demand, hot water you need a
reasonable temperature differential between your max HW temp and the
store temp. HW would normally be at 50C or there abouts a 10C
differential means a minimum store temp of 60C...

The big crossflow plate heat exchangers will actually work down to quite
a small temperature differential - some under 5 degrees.




--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Sep 23, 6:26*pm, John Rumm wrote:
On 23/09/2011 17:14, Dave Liquorice wrote:

On Fri, 23 Sep 2011 00:21:05 +0100, John Rumm wrote:

With a store temp range of 20C you need about 1000l for every
90MJ
(25kWhr) of energy.

Ah!

So if the store temp could drop to say 30C (underfloor heating)
something like 60kWhr/1000l.

30C woould be a bit cool even for underfloor heating I'd have
thought. 40C minimum? Running the store down to that temp would also
mean you'd need something else for DHW. To get the required heat

That's why they sometimes run the UFH from a lower tapping - so it leave
a reserve of hotter water for DHW purposes.

transfer from the store to, on demand, hot water you need a
reasonable temperature differential between your max HW temp and the
store temp. HW would normally be at 50C or there abouts a 10C
differential means a minimum store temp of 60C...

The big crossflow plate heat exchangers will actually work down to quite
a small temperature differential - some under 5 degrees.

The only benefit of a plate heat exchanger is that it is compact and
cheap for it's rate of heat exchange. No better or worse than any
other.

On Sep 23, 4:23*pm, harry wrote:
On Sep 23, 10:36*am, Steve Firth wrote:

harry wrote:

[snip]

The advantage of using solar electric would be that they function at
very low light levels and still deliver normal voltage power long
after the solar heat panels are too cool.

This is complete and utter ****. The efficiency of photovoltaics is less
than that of decent solar thermal arrays.

So it is nitwit. *But it dleivers 240v electricity at low light levels
into any heat store, no matter how hot it is, long after the thermal
panel is running too cool to to do this.
**** for brains.

still a lousy idea

On Fri, 23 Sep 2011 16:23:05 +0100, harry wrote:

On Sep 23, 10:36 am, Steve Firth wrote:
harry wrote:

[snip]

The advantage of using solar electric would be that they function at
very low light levels and still deliver normal voltage power long
after the solar heat panels are too cool.

This is complete and utter ****. The efficiency of photovoltaics is less
than that of decent solar thermal arrays.

So it is nitwit. But it dleivers 240v electricity at low light levels
into any heat store, no matter how hot it is, long after the thermal
panel is running too cool to to do this.
**** for brains.

240 volts - and how much current?

--
Rod

NT wrote:
On Sep 22, 9:41 pm, Tim Lamb wrote:

I know this has been done to death previously but I am about to visit a
friend who is contemplating a *grand design*.

National grid want their usual arm and 3 legs to connect so alternative
sources are under consideration. The site is on a steep slope so a
basement thermal store would be do-able.

Very roughly, how large a store of water would be required to provide
dhw and under floor heating for say 200m2, constructed to something
better than current regs.?

The idea would be to heat this with off peak electricity possibly
supplemented with power from a PV array. Nice unshaded South facing
roof.

I suppose tank life and replaceability is a consideration.

regards

PV to heat is never worth doing. Solarthermal to heat is a fraction
the cost.

Dont tell harry.....

NT

polygonum wrote:
On Fri, 23 Sep 2011 16:23:05 +0100, harry wrote:

On Sep 23, 10:36 am, Steve Firth wrote:
harry wrote:

[snip]

The advantage of using solar electric would be that they function at
very low light levels and still deliver normal voltage power long
after the solar heat panels are too cool.

This is complete and utter ****. The efficiency of photovoltaics is less
than that of decent solar thermal arrays.

So it is nitwit. But it dleivers 240v electricity at low light levels
into any heat store, no matter how hot it is, long after the thermal
panel is running too cool to to do this.
**** for brains.

240 volts - and how much current?

couple of picoamps? :-)

The Natural Philosopher wrote:
polygonum wrote:
On Fri, 23 Sep 2011 16:23:05 +0100, harry wrote:

On Sep 23, 10:36 am, Steve Firth wrote:
harry wrote:

[snip]

The advantage of using solar electric would be that they function at
very low light levels and still deliver normal voltage power long
after the solar heat panels are too cool.

This is complete and utter ****. The efficiency of photovoltaics is
less
than that of decent solar thermal arrays.

So it is nitwit. But it dleivers 240v electricity at low light levels
into any heat store, no matter how hot it is, long after the thermal
panel is running too cool to to do this.
**** for brains.

240 volts - and how much current?

couple of picoamps? :-)


I've just realised that steve firth is being even more of a tosser than
harry.

A solar thermal panel will - if insulated properly and proteced from
re-radiation.. - theoretically get up to the temperature of the sun, as
long as you only take very small amounts off heat out.

"Dave Liquorice" wrote:
On Thu, 22 Sep 2011 23:03:19 +0000 (UTC), Steve Firth wrote:

We have a 300 litre thermal store with solar thermal panels,

How big (sq m) are your solar thermal panels.

We have two 30 tube panels. Each is a 3 sq m aperture. This is overkill for
280 sq m of floor and DHW given that we're in Italy.

Trying to get a handle
on what I'm being offered. I'm not convinced that a 250l store and
3.23m^2 (apperture) is big enough, we have plenty of roof space for
larger or extra panels.

I suspect it's right sized for summer and may be small for the extreme ends
of the season.

We do have a space heating requirement even during the summer. The
current oil boiler normally only has a thermostat controlled holiday
from space heating duty for at most a month. This "summer" the total
number of single days it hasn't fired for heating is probably less
than seven...

The UK house is oil fired but cunning Georgian builders ensured that it has
huge thermal mass and that it heats up passively from the south facing
windows. Even in December we have days when the boiler doesn't fire.

"Dave Liquorice" wrote:
On Fri, 23 Sep 2011 00:21:05 +0100, John Rumm wrote:

With a store temp range of 20C you need about 1000l for every
90MJ
(25kWhr) of energy.

Ah!

So if the store temp could drop to say 30C (underfloor heating)
something like 60kWhr/1000l.

30C woould be a bit cool even for underfloor heating I'd have
thought.

About optimum in my experience.

40C minimum? Running the store down to that temp would also
mean you'd need something else for DHW. To get the required heat
transfer from the store to, on demand, hot water you need a
reasonable temperature differential between your max HW temp and the
store temp. HW would normally be at 50C or there abouts a 10C
differential means a minimum store temp of 60C...

We have DHW set to 45C at present. My wife finds that to be excessive. I
may try 40C next time I get to fiddle with the mixer valve.

You seem to be forgetting that the thermal store is stratified. DHW and
radiator feeds are taken from the top of the cylinder. UFH is taken from
the lower third. Similarly boiler flow is about halfway down, solar and
solid fuel flow is taken from the bottom.

In message o.uk, Dave
Liquorice writes
On Fri, 23 Sep 2011 00:21:05 +0100, John Rumm wrote:

With a store temp range of 20C you need about 1000l for every
90MJ
(25kWhr) of energy.

Ah!

So if the store temp could drop to say 30C (underfloor heating)
something like 60kWhr/1000l.

30C woould be a bit cool even for underfloor heating I'd have
thought. 40C minimum? Running the store down to that temp would also
mean you'd need something else for DHW. To get the required heat
transfer from the store to, on demand, hot water you need a
reasonable temperature differential between your max HW temp and the
store temp. HW would normally be at 50C or there abouts a 10C
differential means a minimum store temp of 60C...

Depends on the pipe spacing. I'm no expert but our annexe runs happily
at 27C.

John was suggesting that stratification and separate draw off points
could take care of DHC. I think a separate cylinder fed from off peak
might be simpler in use. There is the issue of pipe runs and time for
hot water to reach the taps. A very large heating store might be best at
ground level.

Initial thinking is that this may be an *upside down* house with a
kitchen on the second floor.

regards


--
Tim Lamb

The Natural Philosopher wrote:
The Natural Philosopher wrote:
polygonum wrote:
On Fri, 23 Sep 2011 16:23:05 +0100, harry wrote:

On Sep 23, 10:36 am, Steve Firth wrote:
harry wrote:

[snip]

The advantage of using solar electric would be that they function at
very low light levels and still deliver normal voltage power long
after the solar heat panels are too cool.

This is complete and utter ****. The efficiency of photovoltaics is less
than that of decent solar thermal arrays.

So it is nitwit. But it dleivers 240v electricity at low light levels
into any heat store, no matter how hot it is, long after the thermal
panel is running too cool to to do this.
**** for brains.

240 volts - and how much current?

couple of picoamps? :-)


I've just realised that steve firth is being even more of a tosser than harry.

Your brain is ****ed. Must be that "degree" from Ipswich.

A solar thermal panel will - if insulated properly and proteced from
re-radiation.. - theoretically get up to the temperature of the sun, as
long as you only take very small amounts off heat out.

Yeah if I were you, I would ridicule something haven't said.

Given the same incident radiation a solar thermal panel will produce more
usable heat than a photovoltaic panel feeding an immersion heater. Unlike
Harry I am not trying to claim that solar panels produce useful power in
the gloom.

In message , Alan Braggins
writes
In article
,
harry wrote:
On Sep 23, 10:36*am, Steve Firth wrote:
harry wrote:

The advantage of using solar electric would be that they function at
very low light levels and still deliver normal voltage power long
after the solar heat panels are too cool.

This is complete and utter ****. The efficiency of photovoltaics is less
than that of decent solar thermal arrays.

So it is nitwit. But it dleivers 240v electricity at low light levels
into any heat store, no matter how hot it is, long after the thermal
panel is running too cool to to do this.

Use a hybrid thermal-PV panel with the PV running a heat pump from low
temperature thermal panels into a higher temperature store.
(Apparently there are actually commercially available systems that do that.)

That makes a sort of sense. Ideally the overall system needs to be
maintenance free and within the understanding of an oldish person. She
is good with TV button sets:-)

regards

--
Tim Lamb