We moved into our two storey, reconstituted stone-built, pitched-roof
house in April.

We decided early on to get as much of our energy as possible from
renewables.

A couple of weeks ago we signed up for a solar heating system. I've
looked at a few and this seems like a very good system.

The marketing wonk who visited us (who had obviously been in the pub
first) declared that our directly west-facing roof would be perfectly
adequate to site the panels. It is a very clear prospect as it faces a
flat field, and there are no trees in the line of sight.

However, when their surveyor came to measure up he said that the
west-facing roof was inadequate and the panels would have to be sited
on the gable-end wall (facing south).

I can't see how this would be an improvement. Even though the panels
would be angled away from the wall (mimicing the roof's pitch) they
would certainly be obscured by the angle of the roof for at least part
of the morning and part of the evening.

Am I wrong? The alternative, according to the surveyor, would be double
the number of panels with half on the east pitch and the other on the
west.

Many thanks

Will.

"Will" wrote:
We moved into our two storey, reconstituted stone-built, pitched-roof
house in April.

We decided early on to get as much of our energy as possible from
renewables.

A couple of weeks ago we signed up for a solar heating system. I've
looked at a few and this seems like a very good system.

Watchdog 'did' the solar energy industry on BBC 1 last Tuesday evening.
Their conclusions were that there a lot of rogue companies, the estimates
for equipment and installation are very inflated (£12,000 in one case for a
non-working system), the claimed energy benefits are often very exaggerated,
the salesmen talk a lot of dishonest rubbish, and a lot of properties are
not suitable. My understanding is that the panels need to be mounted on a
south-facing aspect. Got a long bargepole?

We moved into our two storey, reconstituted stone-built, pitched-roof
house in April.

We decided early on to get as much of our energy as possible from
renewables.

A couple of weeks ago we signed up for a solar heating system. I've
looked at a few and this seems like a very good system.

The marketing wonk who visited us (who had obviously been in the pub
first) declared that our directly west-facing roof would be perfectly
adequate to site the panels. It is a very clear prospect as it faces
a flat field, and there are no trees in the line of sight.

However, when their surveyor came to measure up he said that the
west-facing roof was inadequate and the panels would have to be sited
on the gable-end wall (facing south).

I can't see how this would be an improvement. Even though the panels
would be angled away from the wall (mimicing the roof's pitch) they
would certainly be obscured by the angle of the roof for at least part
of the morning and part of the evening.

Am I wrong? The alternative, according to the surveyor, would be
double the number of panels with half on the east pitch and the other
on the west.

Have you checked with the local planners that you don't need their
permission? Quite a lot of people get caught out with this.

Peter Crosland

On 16 Nov 2006 12:09:52 -0800, "Will" wrote:

We moved into our two storey, reconstituted stone-built, pitched-roof
house in April.

We decided early on to get as much of our energy as possible from
renewables.

A couple of weeks ago we signed up for a solar heating system. I've
looked at a few and this seems like a very good system.

The marketing wonk who visited us (who had obviously been in the pub
first) declared that our directly west-facing roof would be perfectly
adequate to site the panels. It is a very clear prospect as it faces a
flat field, and there are no trees in the line of sight.

However, when their surveyor came to measure up he said that the
west-facing roof was inadequate and the panels would have to be sited
on the gable-end wall (facing south).

I can't see how this would be an improvement. Even though the panels
would be angled away from the wall (mimicing the roof's pitch) they
would certainly be obscured by the angle of the roof for at least part
of the morning and part of the evening.

Am I wrong? The alternative, according to the surveyor, would be double
the number of panels with half on the east pitch and the other on the
west.

Many thanks

Will.

Its a little difficult to visualise the gable end of the roof, but it
sounds at though your roof ridge runs north/south, which is really as
bad as it gets for placing solar panels (presumably water heating, not
space heating?).
Technically your surveyor is right - in the northern hemisphere they
should face south at approximately the angle of your latitude.
I don't understand, from your description, how they can "mimic" the
roof pitch, unless there is a small angled roof facing south - in
which case that is where the panel should be placed.
In practice you may need to make a compromise if your roof has wrong
angles. But remember its an expensive installation, so you want to
capture the greatest amount of solar insolation possible.

Of course, if the panels were for space heating, you might want the
greatest input in the morning, in which case the east facing roof
might be better. There are a number of factors to consider.

Best wishes
Eric Sears.

Eric Sears

"Eric Sears" wrote in message
...

Technically your surveyor is right - in the northern hemisphere they
should face south at approximately the angle of your latitude.

Correct, and a little shade in the early morning and late evening is neither
here nor there as there's little heat in the sun's rays at those times. Look
at graphs for solar energy vs time of day, and vs orientation, angle, etc.

I don't understand, from your description, how they can "mimic" the
roof pitch, unless there is a small angled roof facing south - in
which case that is where the panel should be placed.

He just means that they'll be mounted at an angle rather than vertically.


Of course, if the panels were for space heating, you might want the
greatest input in the morning, in which case the east facing roof
might be better. There are a number of factors to consider.

Solar panels for space heating! How daft is that! Who needs heating
April-September? If you do, it'll be because the sun isn't shining... These
things provide some heat at other times, but not enough to get your cylinder
hot let alone heat the house! Super-insulated eco-houses excepted, of
course.

Mark

"Peter Crosland" wrote in message
...
However, when their surveyor came to measure up he said that the
west-facing roof was inadequate and the panels would have to be sited
on the gable-end wall (facing south).

Have you checked with the local planners that you don't need their
permission? Quite a lot of people get caught out with this.

Good point. You can normally fit panels to the roof without PP if they don't
protrude more than about 100mm, but sticking them on a gable end at an angle
probably will require PP.

To be safe it's best to get a letter from the local planning dept even if no
PP is required, to help speed the inevitable solicitor's queries when the
time comes to sell. I did for mine, in fact I delayed placing my order until
it was in my hands.

Mark

On 16 Nov 2006 12:09:52 -0800, Will wrote:

However, when their surveyor came to measure up he said that the
west-facing roof was inadequate and the panels would have to be sited
on the gable-end wall (facing south).

I'd go with the surveyor. Maximum solar input is at midday, the sun is
due south at midday, you want to present the largest surface area to the
incoming radiation that you can to capture the most energy.

Early morning and late evening with the sun low in the sky has much less
energy available than midday.

--
Cheers
Dave. pam is missing e-mail

"Will" wrote in message
oups.com...
We moved into our two storey, reconstituted stone-built, pitched-roof
house in April.

We decided early on to get as much of our energy as possible from
renewables.

A couple of weeks ago we signed up for a solar heating system. I've
looked at a few and this seems like a very good system.

The marketing wonk who visited us (who had obviously been in the pub
first) declared that our directly west-facing roof would be perfectly
adequate to site the panels. It is a very clear prospect as it faces a
flat field, and there are no trees in the line of sight.

However, when their surveyor came to measure up he said that the
west-facing roof was inadequate and the panels would have to be sited
on the gable-end wall (facing south).

From our experience with our very good south-facing solar panel I'd say that
the surveyor was right. The sun's rays will only be falling on a west-facing
panel for part of the day and in winter they'll be too low to be effective.

I can't see how this would be an improvement. Even though the panels
would be angled away from the wall (mimicing the roof's pitch) they
would certainly be obscured by the angle of the roof for at least part
of the morning and part of the evening.

Am I wrong? The alternative, according to the surveyor, would be double
the number of panels with half on the east pitch and the other on the
west.

That would make it very expensive.

We only looked into the system because we had a directly south facing
pitched roof, if we'd not had that we wouldn't have considered it.

I don't know what your system is but suspect it can't be the same as ours,
our company was very straight with us. In fact, because we did the work
ourselves, nobody visited, they didn't need to.

Mary

Many thanks

Will.

On Thu, 16 Nov 2006 21:11:51 -0000, "MarkK"
wrote:

"Eric Sears" wrote in message
...

Technically your surveyor is right - in the northern hemisphere they
should face south at approximately the angle of your latitude.

Correct, and a little shade in the early morning and late evening is neither
here nor there as there's little heat in the sun's rays at those times. Look
at graphs for solar energy vs time of day, and vs orientation, angle, etc.

I don't understand, from your description, how they can "mimic" the
roof pitch, unless there is a small angled roof facing south - in
which case that is where the panel should be placed.

He just means that they'll be mounted at an angle rather than vertically.


Of course, if the panels were for space heating, you might want the
greatest input in the morning, in which case the east facing roof
might be better. There are a number of factors to consider.

Solar panels for space heating! How daft is that! Who needs heating
April-September? If you do, it'll be because the sun isn't shining... These
things provide some heat at other times, but not enough to get your cylinder
hot let alone heat the house! Super-insulated eco-houses excepted, of
course.

http://www.sunwarm.com/
These sent us a leaflet
Thats for new build only I think but they do a retro fit solution too.
I'm not entirely convinced but I do know the south side of my house in
winter during the day is very toasty but the north side isn't.



Mark

"Will" wrote in message
oups.com...


Am I wrong? The alternative, according to the surveyor, would be double
the number of panels with half on the east pitch and the other on the
west.


South facing or just West of South, but certainly not West.

In alt.energy.renewable Will wrote:
The marketing wonk who visited us (who had obviously been in the pub
first) declared that our directly west-facing roof would be perfectly
adequate to site the panels. It is a very clear prospect as it faces a
flat field, and there are no trees in the line of sight.

http://rredc.nrel.gov/solar/codes_al...ATTS/version1/
is set up for predicting solar PV installations, but you could make use of
the solar insolation for various angles to see the effect of reorienting
the panels.

Directly south should be the best. Flat on the wall can be compared to
various pitches using the calculator. It might be that flat on a south
wall is better than your west-facing pitched roof.

Highlight "Europe" radio button, then select, say, GBR-London.
The defaults fall to 180 degree azimuth, 51 degree elevation.
That yields "Solar Radiation (kWh/m2/day)" of 3.07.
A tilt of 90 degrees yields 2.16.
Moving to directly west azimuth, 51 degree tilt is 2.32.

This calculator uses observed sunlight at various locations, so it takes
into account the number of sunny days you have in the area as well as sun
angles.

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

On 16 Nov "Will" wrote:

I can't see how this would be an improvement. Even though the panels
would be angled away from the wall (mimicing the roof's pitch) they
would certainly be obscured by the angle of the roof for at least part
of the morning and part of the evening.

I would cancel the order until the details are worked out.

If this is for space heating, then both the east and
west facing slopes are no good unless the panels are mounted
at a complex angle so that they face south and up at an angle
according to latitude (to get more heat in winter than summer,
plus 23 degrees, which at north 50 degrees, approaches
vertical).

Vertical south facing walls are best for the most heat
in the winter in higher north latitudes.

Am I wrong? The alternative, according to the surveyor, would be double
the number of panels with half on the east pitch and the other on the
west.
Will.

For a millionaire, sure. Most installations have
the panels at the same angle as the roof, but only when
the roof slopes south (in the northern hemisphere),
but HVAC experts know that for thermal energy,
and not solar electric, vertical mounting on a south
facing wall is best for maximum heat in winter.

But the type of panels might make a difference,
air panels without storage might heat certain rooms,
like the kitchen and bath in the morning, and other
rooms later in the day.
Drain-down water panels with thermal storage
really should be tracking panels to get the most heat, and
tracking is not implemented as much as it should be.

If the panels are mounted on the west slope,
and there is no concern about the appearance, then
they could be angled toward the south, but would
need space in between panels so that no panel makes
shade on another panel.

If there is enough yard space, it might be
better to mount the panels on a platform a few
feet above the ground, and have the platform
rotate to face the sun.

All it takes for a rotating platform is a post
and a couple of wheels to allow rotation, and
for better results have an altitude tracking system,
ask about the tracking here.

In general, east and west facing roof slopes
are not good for solar water heating unless the pitch
is shallow, and the panels are angled to the south

The roof pitch should be ignored, and the
panels mounted so they get the most direct sun,
but sometimes that makes an unsightly installation.

Panels on the south facing wall sounds good,
especially if the wall has enough area, but tracking
would be better.

Joe Fischer

1.Do not do anything until you have looked at Navitron's website.
2. Solar panels do not have to be high up - I know at least one geezer who
has them at ground level and another who has one on his garage.
3. Do not believe ignoramuses who suggest that you will not get much heat -
that did apply to the old flat panel stuff, still being sold by B&Q, but the
vacuum tubes now being used on the continent are vastly superior. I recently
went to a demo and noted a cylinder water temperature of 48 c being obtained
on a relatively cloudy and cool day. I am reliably advised that on a warm
summers day, the tube manifold can reach well over 100 c and hence so much
heat is being soaked up that one can have 3 to 4 free baths and still have
to dump excess heat into a loft radiator - that's how good they are.
4. If you have already signed up and paid a deposit for a flat panel system
do your best to get out of it.
5. I will probably be putting in a Navitron system myself soon with help
from plumber brother for around £900. The B & Q deal for £1500 is a total
rip off and the energy savings will take at least 15 years to recover.
"Will" wrote in message
oups.com...
We moved into our two storey, reconstituted stone-built, pitched-roof
house in April.

We decided early on to get as much of our energy as possible from
renewables.

A couple of weeks ago we signed up for a solar heating system. I've
looked at a few and this seems like a very good system.

The marketing wonk who visited us (who had obviously been in the pub
first) declared that our directly west-facing roof would be perfectly
adequate to site the panels. It is a very clear prospect as it faces a
flat field, and there are no trees in the line of sight.

However, when their surveyor came to measure up he said that the
west-facing roof was inadequate and the panels would have to be sited
on the gable-end wall (facing south).

I can't see how this would be an improvement. Even though the panels
would be angled away from the wall (mimicing the roof's pitch) they
would certainly be obscured by the angle of the roof for at least part
of the morning and part of the evening.

Am I wrong? The alternative, according to the surveyor, would be double
the number of panels with half on the east pitch and the other on the
west.

Many thanks

Will.

On 16 Nov 2006 12:09:52 -0800 Will wrote :
However, when their surveyor came to measure up he said that the
west-facing roof was inadequate and the panels would have to be sited
on the gable-end wall (facing south).

You might want to download SAP2005 from www.bre.co.uk/sap2005

You can leave 95% of it to people like me, but Appendix H will give you
some hard numbers. Table H2 gives solar radiation as 724W/m2 on a
vertical south facing panel, 886/829 for a west facing panel pitched at
30/45 degrees.

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk

On Thu, Tony Bryer wrote:

On 16 Nov 2006 12:09:52 -0800 Will wrote :
However, when their surveyor came to measure up he said that the
west-facing roof was inadequate and the panels would have to be sited
on the gable-end wall (facing south).

You might want to download SAP2005 from www.bre.co.uk/sap2005

You can leave 95% of it to people like me, but Appendix H will give you
some hard numbers. Table H2 gives solar radiation as 724W/m2 on a
vertical south facing panel, 886/829 for a west facing panel pitched at
30/45 degrees.

Is that average year-round, or max in January?

for domestic hot water, year round is important,
for space heating, the max in winter should be sought.

Pitching the panels south on a west sloping roof
really complicates the installation because of trying to
position the mounts without causing leaks.

Joe Fischer

On Thu, 16 Nov 2006 18:41:47 -0500 Joe Fischer wrote :
Is that average year-round, or max in January?

Sorry I gave you the wrong units: the numbers are kWh/m2/yr

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk

MarkK wrote:

Solar panels for space heating! How daft is that! Who needs heating
April-September? If you do, it'll be because the sun isn't shining... These
things provide some heat at other times, but not enough to get your cylinder
hot let alone heat the house! Super-insulated eco-houses excepted, of
course.

Mark

http://www.builditsolar.com/
&
http://www.builditsolar.com/Projects...ce_Heating.htm


NT

Richard Bates wrote:

3. Do not believe ignoramuses who suggest that you will not get much heat -
that did apply to the old flat panel stuff, still being sold by B&Q, but the
vacuum tubes now being used on the continent are vastly superior. I recently
went to a demo and noted a cylinder water temperature of 48 c being obtained
on a relatively cloudy and cool day. I am reliably advised that on a warm
summers day, the tube manifold can reach well over 100 c and hence so much
heat is being soaked up that one can have 3 to 4 free baths and still have
to dump excess heat into a loft radiator - that's how good they are.
4. If you have already signed up and paid a deposit for a flat panel system
do your best to get out of it.

You'll notice the thread is posted to uk.d-i-y as well as other ngs.
This tells me the OP is in Britain.

First, flat panels give much better ROI than vac tubes
Second, British winters are mostly overcast, and flat panels work ok on
indirect sun, whereas silvered evacuated tubes work a lot less
efficiently under these conditions.

3rd, it is all more complex than that, but suffice it to say that flat
panels are very much a going concern in Britain.

An optimally designed system would have a mix of both flat panel and
vac tube, with each heating a separate part of the system. Flat panel
is best for mid-temp water, as it gives much more output per £/$. Vac
tube is best for the final max temp water, as it gives high output
temps that flat panels cant consistently deliver. However, the ROI on
the flat tubes will be much poorer, so spending some of the money on
flat panels will much improve total annual output.


NT

On Thu, 16 Nov 2006 18:09:22 -0500, Joe Fischer
wrote:

I agree with that. If you can. Sounds didgy.
I would cancel the order until the details are worked out.

On 16 Nov 2006 12:09:52 -0800 someone who may be "Will"
wrote this:-

However, when their surveyor came to measure up he said that the
west-facing roof was inadequate and the panels would have to be sited
on the gable-end wall (facing south).

Generally that is the case.

I can't see how this would be an improvement. Even though the panels
would be angled away from the wall (mimicing the roof's pitch) they
would certainly be obscured by the angle of the roof for at least part
of the morning and part of the evening.

I find that difficult to visualise without looking at the house.
However, the sun is usually weak in those positions.

Someone mentioned planning permission in the thread. You didn't say
which country you are in, but if you are in Scotland then an
installation mounted on the house wall doesn't need planning
permission, provided a few conditions are met. An installation
mounted on a roof only needs planning permission if it sticks up by
more than a certain amount. The certain amount is no problem for
flat panel systems, but is a problem for evacuated tubes, where the
header may stick above the limit. Beware that the natural reaction
of planning officials is to say no, you may need to quote chapter
and verse to them before they agree that an installation doesn't
need planning permission.


--
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

Will,

I too have been experimenting and trying to get all my energy from
renewables. First was to have a structure that needed a minimum of
energy. I have a simple structure with 12" thick walls filled with
fiberglass insulation.

I use no power for heating or A/C.As long as there is light outside it
is enough to serve my needs inside ... the roof has clear sections
insulated with bubble wrap.

But my experience with solar panels show them to be an abject failure.

1. Cost is high. My 165W high voltage panel cost over $700
2. My 165W panel has never delivered more than 90W
3. The panel can only supply current about 5 hrs per day
4. The panel only supply useful power on sunny days
5. The panel loses lots of efficiency on hot days
6. Any shadow on the panel is the same as complete panel in shade
7. Can lose 30% or more if panel is not perpendicular to sun's rays
8. Charge controller must be very efficient or more is lost
9. For anything practical a huge number of panels and batteries is
necessary

The solution I have arrived at is hybrid. I use my one panel to charge
batteries when I'm away. When away, my refrigerator is my only load
(about 120W with 30% duty cycle). My battery bank is 10 70AH car
batteries. All together they cost about as much as my 1 PV panel. I
don't use deep discharge because they are much more expensive and I
haven't seen an inverter that works below 10V. Most shut down at 11.5V.


My real power source is a 3hp diesel engine driving a car alternator
capable of delivering 40A. I run it on waste vegatable oil (WVO) at low
RPM (~1,000). I route it through the same high voltage (up to 53VDC)
charge controller that I use with the PV panel. It does a splendid job
of keeping the batteries charged and only runs 4 to 5 hours per day. It
uses hopper cooling so I get my hot water from it as well.

The batteries have enough charge to get me through the night with no
other power source. I use small fluorescent lights and all that is
usually running is my refrigerator. I use less than 50AH over night and
the diesel recovers that in the morning in less than 2 hours.

My average daily consumption is about 1.2KWH.

Regards,

Todd Marshall
Plantersville, TX

Will wrote:
We moved into our two storey, reconstituted stone-built, pitched-roof
house in April.

We decided early on to get as much of our energy as possible from
renewables.

A couple of weeks ago we signed up for a solar heating system. I've
looked at a few and this seems like a very good system.

The marketing wonk who visited us (who had obviously been in the pub
first) declared that our directly west-facing roof would be perfectly
adequate to site the panels. It is a very clear prospect as it faces a
flat field, and there are no trees in the line of sight.

However, when their surveyor came to measure up he said that the
west-facing roof was inadequate and the panels would have to be sited
on the gable-end wall (facing south).

I can't see how this would be an improvement. Even though the panels
would be angled away from the wall (mimicing the roof's pitch) they
would certainly be obscured by the angle of the roof for at least part
of the morning and part of the evening.

Am I wrong? The alternative, according to the surveyor, would be double
the number of panels with half on the east pitch and the other on the
west.

Many thanks

Will.

"Joe Fischer" wrote in message
...

The roof pitch should be ignored, and the
panels mounted so they get the most direct sun,
but sometimes that makes an unsightly installation.

I disagree that solar water heating panels are unsightly, they look like a
large Velux window, flat and dark.

Mary

"Todd" wrote in message
oups.com...
Will,

I too have been experimenting and trying to get all my energy from
renewables. First was to have a structure that needed a minimum of
energy. I have a simple structure with 12" thick walls filled with
fiberglass insulation.

I use no power for heating or A/C.As long as there is light outside it
is enough to serve my needs inside ... the roof has clear sections
insulated with bubble wrap.

But my experience with solar panels show them to be an abject failure.

The OP was asking about solar water heating, not electricity production :-)

My experience of solar water heating is very good.

Mary

On Fri, 17 Nov 2006 12:58:52 -0000, Mary Fisher wrote:

"Joe Fischer" wrote in message
...

The roof pitch should be ignored, and the
panels mounted so they get the most direct sun,
but sometimes that makes an unsightly installation.

I disagree that solar water heating panels are unsightly, they look like a
large Velux window, flat and dark.

You appear to have misunderstood the observation about ignoring the roof
pitch. For best efficiency the panels need to be set at an appropriate
angle which can be steeper than the roof pitch. This means that the panel
must stand proud of the roof. Which *is* unsightly but it is also more more
efficient.

Your observations about the appearance of the panels also refers really to
the style of low-efficiency flat panel that you favour. An efficient vacuum
tube array does not look like a Velux. OTOH Velux windows are also
unsightly.

Steve Firth wrote:
On Fri, 17 Nov 2006 12:58:52 -0000, Mary Fisher wrote:

"Joe Fischer" wrote in message
...
The roof pitch should be ignored, and the
panels mounted so they get the most direct sun,
but sometimes that makes an unsightly installation.
I disagree that solar water heating panels are unsightly, they look like a
large Velux window, flat and dark.

You appear to have misunderstood the observation about ignoring the roof
pitch. For best efficiency the panels need to be set at an appropriate
angle which can be steeper than the roof pitch. This means that the panel
must stand proud of the roof. Which *is* unsightly but it is also more more
efficient.

Is that "much more" efficient? I wonder.

For someone in England the altitude of the sun is about
90 - 52 +-23.5 = 14.5 to 61.5 degrees with the lowest value in midwinter.

So about 38-11.75 = 26.25 degrees from vertical is a good panel angle for winter
heating. The efficiency varies roughly as cos(angle from optimum). For a roof
making an angle of 50 degree with the vertical, the efficiency is

cos(50-26.25 deg) = cos(23.75 deg) = 91.5%
(a vertical mounting has cos(26.25) = 89.7% efficiency)

so you only lose about 8.5% efficiency with a flush roof mounting. Not too bad.

Toby

Solar thermal panels for space heating is one of the ways we can
save lots of fossil fuels in the future.

"MarkK" wrote in message ...
"Eric Sears" wrote in message
...

Technically your surveyor is right - in the northern hemisphere they
should face south at approximately the angle of your latitude.

Correct, and a little shade in the early morning and late evening is neither
here nor there as there's little heat in the sun's rays at those times. Look
at graphs for solar energy vs time of day, and vs orientation, angle, etc.

I don't understand, from your description, how they can "mimic" the
roof pitch, unless there is a small angled roof facing south - in
which case that is where the panel should be placed.

He just means that they'll be mounted at an angle rather than vertically.


Of course, if the panels were for space heating, you might want the
greatest input in the morning, in which case the east facing roof
might be better. There are a number of factors to consider.

Solar panels for space heating! How daft is that! Who needs heating
April-September? If you do, it'll be because the sun isn't shining... These
things provide some heat at other times, but not enough to get your cylinder
hot let alone heat the house! Super-insulated eco-houses excepted, of
course.

Mark

On Fri, Toby Kelsey wrote:

Steve Firth wrote:
On Fri, 17 Nov 2006 12:58:52 -0000, Mary Fisher wrote:
"Joe Fischer" wrote in message
...
The roof pitch should be ignored, and the
panels mounted so they get the most direct sun,
but sometimes that makes an unsightly installation.

I disagree that solar water heating panels are unsightly, they look like a
large Velux window, flat and dark.

You appear to have misunderstood the observation about ignoring the roof
pitch. For best efficiency the panels need to be set at an appropriate
angle which can be steeper than the roof pitch. This means that the panel
must stand proud of the roof. Which *is* unsightly but it is also more more
efficient.

Is that "much more" efficient? I wonder.

In winter, maybe, and that is for a south slope
roof, the original poster has an east-west sloped roof,
which is a problem.

For someone in England the altitude of the sun is about
90 - 52 +-23.5 = 14.5 to 61.5 degrees with the lowest value in midwinter.

So about 38-11.75 = 26.25 degrees from vertical is a good panel angle for winter
heating.

Actually, vertical or almost vertical is better in
winter for space heating, and does not overheat the
panels as much in summer.
Also, mounted on a south facing vertical wall,
snow cover can give 50 percent more thermal energy
in winter, or even polished aluminum laying flat
can almost double the thermal energy.
And in a region where hail is likely, the vertical
mount protects any plastic or glass cover.

The efficiency varies roughly as cos(angle from optimum). For a roof
making an angle of 50 degree with the vertical, the efficiency is

cos(50-26.25 deg) = cos(23.75 deg) = 91.5%
(a vertical mounting has cos(26.25) = 89.7% efficiency)

Is that year round, or only in winter?

so you only lose about 8.5% efficiency with a flush roof mounting. Not too bad.
Toby

On the west slope roof there would be zero efficiency
until nearly noon, even if the panels have the north edge
of each higher than the south edge with the panels spaced
wide apart so they don't shade each other.

The big advantage of the south facing wall mount
is the near optimum efficiency in winter, with the
possibility of extra reflections to exceed 100 percent
rating of the panels, and the reduction of thermal
energy in summer. (This was discussed at length
with graphs in a 1959 ASHVAC proceedings
publication).

But that is for space heating (and it has a short
pay back time for low cost flat panel collectors), and
for domestic hot water, it may also be suitable, with
maybe one or two panels mounted for summer sun.

Joe Fischer

Joe Fischer wrote:

Is that "much more" efficient? I wonder.

In winter, maybe, and that is for a south slope
roof, the original poster has an east-west sloped roof,
which is a problem.

With an east-west slope the heating would be much less, and may even be better
with a cloudier sky.

For someone in England the altitude of the sun is about
90 - 52 +-23.5 = 14.5 to 61.5 degrees with the lowest value in midwinter.

So about 38-11.75 = 26.25 degrees from vertical is a good panel angle for winter
heating.

Actually, vertical or almost vertical is better in
winter for space heating, and does not overheat the
panels as much in summer.

In fact my angles were based on the midday sun position, so a more vertical
position is probably better for capturing the sun during most of the day, and a
vertical position is better than I calculated.

Is overheating a big issue? Could you automatically cover the panels?

Also, mounted on a south facing vertical wall,
snow cover can give 50 percent more thermal energy
in winter, or even polished aluminum laying flat
can almost double the thermal energy.
And in a region where hail is likely, the vertical
mount protects any plastic or glass cover.

I can see those issues could outweigh any marginal differences in efficiency.

The efficiency varies roughly as cos(angle from optimum). For a roof
making an angle of 50 degree with the vertical, the efficiency is

cos(50-26.25 deg) = cos(23.75 deg) = 91.5%
(a vertical mounting has cos(26.25) = 89.7% efficiency)

Is that year round, or only in winter?

That's only at midday for the winter months, so a bit misleading. In fact the
all-day efficiency of a vertical position is better than that, but I haven't
done the calculation. Other factors also affect the efficiency, for example if
the sun is not visible until it has risen say 5 degrees above the horizontal
that changes the calculation. Or the circulation and heat transfer may be
faster in a vertical orientation. It's better to do a direct comparison in the
field if possible.

On the west slope roof there would be zero efficiency
until nearly noon, even if the panels have the north edge
of each higher than the south edge with the panels spaced
wide apart so they don't shade each other.

And the same for the east side after noon, and with the poor angle you would
probably get less than 1/4th the normal heating effect.

Toby

Mary Fisher wrote:
"Joe Fischer" wrote in message
...
The roof pitch should be ignored, and the
panels mounted so they get the most direct sun,
but sometimes that makes an unsightly installation.

I disagree that solar water heating panels are unsightly, they look like a
large Velux window, flat and dark.

....And unsightly..like a large Velux window. ;-)
..

Mary

On Fri, 17 Nov Toby Kelsey wrote:

Joe Fischer wrote:
In winter, maybe, and that is for a south slope
roof, the original poster has an east-west sloped roof,
which is a problem.

With an east-west slope the heating would be much less, and may even be better
with a cloudier sky.

Popcorn clouds maybe, but full clouds provide
very little heat, especially for any kind of focusing collector
like a trough, dish, or vapor deposited vacuum tube.
PV does get the same voltage with diffuse daylight,
but much less amps.

For someone in England the altitude of the sun is about
90 - 52 +-23.5 = 14.5 to 61.5 degrees with the lowest value in midwinter.

So about 38-11.75 = 26.25 degrees from vertical is a good panel angle for winter
heating.

Actually, vertical or almost vertical is better in
winter for space heating, and does not overheat the
panels as much in summer.

In fact my angles were based on the midday sun position, so a more vertical
position is probably better for capturing the sun during most of the day, and a
vertical position is better than I calculated.

Is overheating a big issue? Could you automatically cover the panels?

Sure, but the sun doesn't rise due east in winter,
and doesn't set due west, so south vertical or near
vertical is better for winter.

Also, mounted on a south facing vertical wall,
snow cover can give 50 percent more thermal energy
in winter, or even polished aluminum laying flat
can almost double the thermal energy.
And in a region where hail is likely, the vertical
mount protects any plastic or glass cover.

I can see those issues could outweigh any marginal differences in efficiency.

It is more true for high latitudes, I think most of Europe
and the UK is higher than I am at 38 N.

The efficiency varies roughly as cos(angle from optimum). For a roof
making an angle of 50 degree with the vertical, the efficiency is

cos(50-26.25 deg) = cos(23.75 deg) = 91.5%
(a vertical mounting has cos(26.25) = 89.7% efficiency)

Is that year round, or only in winter?

That's only at midday for the winter months, so a bit misleading. In fact the
all-day efficiency of a vertical position is better than that, but I haven't
done the calculation. Other factors also affect the efficiency, for example if
the sun is not visible until it has risen say 5 degrees above the horizontal
that changes the calculation. Or the circulation and heat transfer may be
faster in a vertical orientation. It's better to do a direct comparison in the
field if possible.
Toby

There may be charts according to latitude,
this has been studied a lot, but really under implemented,
and it is a shame now with fuel prices getting higher.

There is something really wrong if my car
is warm when the sun shines regardless of temp,
while the house can be cooler than our side with
no heat.

Joe Fischer

In message , Curious
writes
"Will" wrote:
We moved into our two storey, reconstituted stone-built, pitched-roof
house in April.

We decided early on to get as much of our energy as possible from
renewables.

A couple of weeks ago we signed up for a solar heating system. I've
looked at a few and this seems like a very good system.

Watchdog 'did' the solar energy industry on BBC 1 last Tuesday evening.
Their conclusions were that there a lot of rogue companies, the estimates
for equipment and installation are very inflated (£12,000 in one case for a
non-working system), the claimed energy benefits are often very exaggerated,
the salesmen talk a lot of dishonest rubbish, and a lot of properties are
not suitable. My understanding is that the panels need to be mounted on a
south-facing aspect. Got a long bargepole?


We also had a discussion in here following my father having signed up to
such a system

This was £7000

Say a payback period of 10 years being reasonable, it has to save £700 /
year to pay itself back. Given that it's only saving (optimistically )
70% of hot water, not central heating or gas for cooking, it's patently
impossible for it to be viable

--
geoff

In message , Mary Fisher
writes
"Will" wrote in message
roups.com...

The alternative, according to the surveyor, would be double
the number of panels with half on the east pitch and the other on the
west.

That would make it very expensive.

Yes, but not double the price. Maybe about a third more ?


We only looked into the system because we had a directly south facing
pitched roof, if we'd not had that we wouldn't have considered it.

It's not without advantages. It does mean you can get more power
earlier and later in the day, and more or less as much in the middle.


Cheers, J/.
--
John Beardmore

In message , Eric Sears
writes
Of course, if the panels were for space heating, you might want the
greatest input in the morning, in which case the east facing roof
might be better. There are a number of factors to consider.

Like ...

what time the sun rises in winter, how big a thermal store you would
need to store sufficient heat overnight

it's just not very realistic for heating

--
geoff

In message , Mary Fisher
writes
"Will" wrote in message
roups.com...

We moved into our two storey, reconstituted stone-built, pitched-roof
house in April.

We decided early on to get as much of our energy as possible from
renewables.

A couple of weeks ago we signed up for a solar heating system. I've
looked at a few and this seems like a very good system.

The marketing wonk who visited us (who had obviously been in the pub
first) declared that our directly west-facing roof would be perfectly
adequate to site the panels. It is a very clear prospect as it faces a
flat field, and there are no trees in the line of sight.

However, when their surveyor came to measure up he said that the
west-facing roof was inadequate and the panels would have to be sited
on the gable-end wall (facing south).

From our experience with our very good south-facing solar panel I'd say that
the surveyor was right. The sun's rays will only be falling on a west-facing
panel for part of the day and in winter they'll be too low to be effective.

Yes. Facing due west won't be great, but keep in mind that if you
capture heat towards the evening, it won't have to be stored long before
a typical family will use it.

We once inspected a system, and data logged a collector that faces 45
degrees west of south in summer.

To quote our report, "the temperature of the pipe from the solar panel
shows a rise of about 5.25°C per hour on the 25th, starting at around
9:00 and continuing until around 19:00".

(The 25th was one of the few sunny days !)


Cheers, J/.
--
John Beardmore

In message ppk7h.30$JQ.26@trnddc06, SJC writes
Solar thermal panels for space heating is one of the ways we can
save lots of fossil fuels in the future.

Sorry, this is UK.d-i-y, not alt.bad jokes

as practical, as they say, as a chocolate teapot

where are you going to get meaningful heat from at 7am ?

the best source, I would suggest, would be the hot air emanating from
the sales rep

--
geoff

In message , Mary Fisher
writes

"Joe Fischer" wrote in message
.. .

The roof pitch should be ignored, and the
panels mounted so they get the most direct sun,
but sometimes that makes an unsightly installation.

I disagree that solar water heating panels are unsightly, they look like a
large Velux window, flat and dark.

It could only be an improvement around Leeds


--
geoff

In message , MarkK
writes
"Peter Crosland" wrote in message
...
However, when their surveyor came to measure up he said that the
west-facing roof was inadequate and the panels would have to be sited
on the gable-end wall (facing south).

Have you checked with the local planners that you don't need their
permission? Quite a lot of people get caught out with this.

Good point. You can normally fit panels to the roof without PP if they don't
protrude more than about 100mm,

I thought it was 80mm, (even in national parks ?), as long as you aren't
in a conservation area or on a listed building ?


but sticking them on a gable end at an angle
probably will require PP.

Yes - and the planners I've asked really hate it !


To be safe it's best to get a letter from the local planning dept even if no
PP is required, to help speed the inevitable solicitor's queries when the
time comes to sell. I did for mine, in fact I delayed placing my order until
it was in my hands.

Hmmm... I've never heard of such queries, but no doubt it's the kind of
thing solicitors live for...


Cheers, J/.
--
John Beardmore

On Thu, 16 Nov 2006 20:30:21 -0000, "Curious"
wrote:

Good. They should look at all renewables.

Was this solar PV, or solar HWS systems, OOI ?

Watchdog 'did' the solar energy industry on BBC 1 last Tuesday evening.
Their conclusions were that there a lot of rogue companies, the estimates
for equipment and installation are very inflated (£12,000 in one case for a
non-working system), the claimed energy benefits are often very exaggerated,
the salesmen talk a lot of dishonest rubbish, and a lot of properties are
not suitable. My understanding is that the panels need to be mounted on a
south-facing aspect. Got a long bargepole?

You seem to be so sure of yourself, but you are so wrong.
Look up fluid source heat pumps with solar...get a clue.

"raden" wrote in message ...
In message ppk7h.30$JQ.26@trnddc06, SJC writes
Solar thermal panels for space heating is one of the ways we can
save lots of fossil fuels in the future.

Sorry, this is UK.d-i-y, not alt.bad jokes

as practical, as they say, as a chocolate teapot

where are you going to get meaningful heat from at 7am ?

the best source, I would suggest, would be the hot air emanating from
the sales rep

--
geoff

On Fri, 17 Nov 2006 22:12:22 GMT, raden wrote:

Well, having done a few quick calcs, I tend to agree, unless you had a
HUGE heating panel to get it active the next morning.

However, I would be interested in your calcs and figures, as you seem
to feel strongly about this G

Like ...

what time the sun rises in winter, how big a thermal store you would
need to store sufficient heat overnight

it's just not very realistic for heating