On Thursday, December 18, 2014 9:59:51 PM UTC, Martin Brown wrote:
On 18/12/2014 20:05, Dennis@home wrote:
On 18/12/2014 13:52, wrote:

When hot water is heated, it starts stone cold, and progresses up to
piping hot. Flat plate work better at the cold to warm region, tubes
work better in the warm to hot region. Hence the upside of using both
together with 2 water zones, one hot one warm.

I have tubes, with a compound reflector behind them, I can see no reason
why a flat plate of the same area would work any better.
I can see several reasons why flat panels wouldn't work as well.

But then you always were rather dense.

Well, it was addressed further upthread and explained on the link given. Its not just energy out over energy in, its also financial efficiency, ie power out per pound in. That's a prime issue for system choice.

Assuming the same grade of absorber with efficiency 1-a
(a 1 probably around 0.04 in a typical matt black finish)
eg
http://www.aviantechnologies.com/pro...fuse_black.php

And a typical aluminised mirror with an efficiency 1-b
(b 1 but probably around 0.08 or worse)
eg
http://en.wikipedia.org/wiki/Reflect...eflectance.png

Flat plate efficiency = 1-a ~ 96%

Mirror tube efficiency = (1-a)(1-b) ~ 88%

IRL flat plate is far lower due to losses, in fact its normal for them to work all the way down to 0% as they approach their stagnation temp. But as the graph illustrates, at low temps they beat tubes on efficiency, at high temps tubes win.


NT

Acting against that is that with evacuated tubes there is no convection
robbing heat off the tube based designs so long as their vacuum holds.

At higher temperatures the tubes win out with lower convection losses.

t makes me wonder what panels were being compared and what assumptions
were made.

That the mirrors are not perfect ones - which is *very* true.

A typical production mirror scatters or absorbs about 8% of the incident
light where as a decent matt black paint scatters less the 4%.

The concentrators allow you to trade some minor loss of efficiency for a
much higher output temperature which is usually worth it.

There are additional losses off the air-glass surfaces of the front
cover plate as well but they are common to both designs.

In message ,
lid writes
In message ,
writes
Interesting feedback thanks. Obviously not a good idea is the general
consensus.

Just as a matter if interest I thought Id run these figures by and see
if I can get a
clearer picture... My electric storage heater uses 12kwh a night on
cheap rate
night tariff. (Thats 85 p/night) That gets it nice and hot.
Im trying to calculate how many panels would give me the equivelent of
12kwh mains a day...so...

How does one calculate average annual UK output for each 100W panel?
Assuming more in summer less in winter etc.
And how can that be converted into 12kwh/day? In other words
in the UK, if one wanted 12kwh for *general use heating* during the day,
how many 100w panels, on average, would be needed to get the
the equivelent of a mains 12kwh/day input?
Thanks ahead.

On a 4kW SSE-facing array in Sussex, with some shading from trees in
December/January, I get about 3.5MWh/year, so on average, just under
10kWh/day. But that's mostly in May to September. Daily outputs are as
high as 25kWh in summer, but at this time of year 3 kWh would be
exceptionally good, and a dull day might yield only 500Wh. So to
guarantee 12kWh on any day, I make that nine hundred and sixty 100w
panels :-(

HTH...
But scientists have come up with a new way to combat global warming
caused by excessive CO2 emissions by shooting salt crystals into the
atmosphere to create more cloud to reflect the suns heat back into space
thereby screwing solar panels even further - and causing us to fall back
on gas power stations which in turn will pump more CO2 into... Ah!!

--
bert

replying to Rod Speed, Kenneth Graham Rolfe wrote:
Hi, I have 6.5kw of solar panels and yes, in winter you don't get enough power
but I also have a solar diverter which switches any spare power to where you
want it. Most people use this for hot water but I have 3 storage heaters which
I only ever use with free electric. This means I can turn my gas heating down
sooner in spring and on later in autumn. While they will never be able to
replace my gas heating, they certainly save on bills. Ps, the storage heaters
have separate idolaters.

--
for full context, visit https://www.homeownershub.com/uk-diy...r-1013846-.htm

posted on December 15, 2014, 2:04 pm

Hmmmmmmmm.
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Kenneth Graham Rolfe" m
wrote in message ...
replying to Rod Speed, Kenneth Graham Rolfe wrote:
Hi, I have 6.5kw of solar panels and yes, in winter you don't get enough
power
but I also have a solar diverter which switches any spare power to where
you
want it. Most people use this for hot water but I have 3 storage heaters
which
I only ever use with free electric. This means I can turn my gas heating
down
sooner in spring and on later in autumn. While they will never be able to
replace my gas heating, they certainly save on bills. Ps, the storage
heaters
have separate idolaters.

--
for full context, visit
https://www.homeownershub.com/uk-diy...r-1013846-.htm

Kenneth Graham Rolfe
m wrote:

replying to Rod Speed, Kenneth Graham Rolfe wrote:
Hi, I have 6.5kw of solar panels and yes, in winter you don't get enough power
but I also have a solar diverter which switches any spare power to where you
want it. Most people use this for hot water but I have 3 storage heaters which
I only ever use with free electric. This means I can turn my gas heating down
sooner in spring and on later in autumn. While they will never be able to
replace my gas heating, they certainly save on bills. Ps, the storage heaters
have separate idolaters.

I am glad your heaters are treated with the reverence they deserve.

--

Roger Hayter

On Monday, 15 December 2014 14:05:39 UTC, wrote:
Id like to find out if its possible to buy a few solar pv panels, and take the feed
from that direct to a storage heater or underfloor heating pad. Not plug into the grid, or even the house
electrical circuit. And not have the heater or heating coil attached to the mains either to avoid
any shocks etc. Straight from pv to dedicated electric heater.
It doesnt matter if the heat only comes in the day. Thats when I need the heat anyways.
Ive seen underfloor heating kits. And seperate pv solar panels. Can the pv panel
plug straight into the coil of the kit?
One reason I ask is that a few months ago I had seen a solar powered pv panel to underfloor heating kit
for a few hundred pounds online. Ive lost the link, but I know its possible. What Id like to do
Is buy something like that, wrap the coil in bricks and some sort of cover and get cheap heat.
Any thoughts advice etc?
For instance can the electric output from a pv panel go straight to the heating coil and
trickle feed it. and slowly heat the coil Or does it need an intermediate pulse convertor?

Grow firewood trees in your garden and buy a wood stove.
You can collect a lot of firewood for free if in a rural area.

On Saturday, 24 March 2018 15:44:08 UTC, Kenneth Graham Rolfe wrote:
replying to Rod Speed,

must you?

Kenneth Graham Rolfe wrote:

Hi, I have 6.5kw of solar panels and yes, in winter you don't get enough power
but I also have a solar diverter which switches any spare power to where you
want it. Most people use this for hot water but I have 3 storage heaters which
I only ever use with free electric. This means I can turn my gas heating down
sooner in spring and on later in autumn. While they will never be able to
replace my gas heating, they certainly save on bills. Ps, the storage heaters
have separate idolaters.

I suspect you're one of those idolators.


NT

On 24/03/2018 16:33, harry wrote:
On Monday, 15 December 2014 14:05:39 UTC, wrote:
Id like to find out if its possible to buy a few solar pv panels, and take the feed
from that direct to a storage heater or underfloor heating pad. Not plug into the grid, or even the house
electrical circuit. And not have the heater or heating coil attached to the mains either to avoid
any shocks etc. Straight from pv to dedicated electric heater.
It doesnt matter if the heat only comes in the day. Thats when I need the heat anyways.
Ive seen underfloor heating kits. And seperate pv solar panels. Can the pv panel
plug straight into the coil of the kit?
One reason I ask is that a few months ago I had seen a solar powered pv panel to underfloor heating kit
for a few hundred pounds online. Ive lost the link, but I know its possible. What Id like to do
Is buy something like that, wrap the coil in bricks and some sort of cover and get cheap heat.
Any thoughts advice etc?
For instance can the electric output from a pv panel go straight to the heating coil and
trickle feed it. and slowly heat the coil Or does it need an intermediate pulse convertor?

Grow firewood trees in your garden and buy a wood stove.
You can collect a lot of firewood for free if in a rural area.

Is that a peasant's right? What does the Lord of the Manor require in
return?

--
Max Demian

Max Demian wrote:

On 24/03/2018 16:33, harry wrote:
On Monday, 15 December 2014 14:05:39 UTC, wrote:
Id like to find out if its possible to buy a few solar pv panels, and
take the feed from that direct to a storage heater or underfloor
heating pad. Not plug into the grid, or even the house electrical
circuit. And not have the heater or heating coil attached to the mains
either to avoid any shocks etc. Straight from pv to dedicated electric
heater. It doesnt matter if the heat only comes in the day. Thats when
I need the heat anyways. Ive seen underfloor heating kits. And seperate
pv solar panels. Can the pv panel plug straight into the coil of the
kit? One reason I ask is that a few months ago I had seen a solar
powered pv panel to underfloor heating kit for a few hundred pounds
online. Ive lost the link, but I know its possible. What Id like to do
Is buy something like that, wrap the coil in bricks and some sort of
cover and get cheap heat. Any thoughts advice etc? For instance can the
electric output from a pv panel go straight to the heating coil and
trickle feed it. and slowly heat the coil Or does it need an
intermediate pulse convertor?

Grow firewood trees in your garden and buy a wood stove.
You can collect a lot of firewood for free if in a rural area.

Is that a peasant's right? What does the Lord of the Manor require in
return?

Generally it's theft. But I've not noticed anyone complaining. I would
advise against carrying a chainsaw, however.

--

Roger Hayter

On Saturday, 24 March 2018 20:10:03 UTC, Max Demian wrote:
On 24/03/2018 16:33, harry wrote:
On Monday, 15 December 2014 14:05:39 UTC, wrote:
Id like to find out if its possible to buy a few solar pv panels, and take the feed
from that direct to a storage heater or underfloor heating pad. Not plug into the grid, or even the house
electrical circuit. And not have the heater or heating coil attached to the mains either to avoid
any shocks etc. Straight from pv to dedicated electric heater.
It doesnt matter if the heat only comes in the day. Thats when I need the heat anyways.
Ive seen underfloor heating kits. And seperate pv solar panels. Can the pv panel
plug straight into the coil of the kit?
One reason I ask is that a few months ago I had seen a solar powered pv panel to underfloor heating kit
for a few hundred pounds online. Ive lost the link, but I know its possible. What Id like to do
Is buy something like that, wrap the coil in bricks and some sort of cover and get cheap heat.
Any thoughts advice etc?
For instance can the electric output from a pv panel go straight to the heating coil and
trickle feed it. and slowly heat the coil Or does it need an intermediate pulse convertor?

Grow firewood trees in your garden and buy a wood stove.
You can collect a lot of firewood for free if in a rural area.

Is that a peasant's right? What does the Lord of the Manor require in
return?

--
Max Demian


https://www.telegraph.co.uk/news/ukn...m-forests.html

A nominal 4kW array in Yorkshire can produce 25ish kWh on a good day in mid summer.
Around Christmas it struggles to make 1kWh
Forget the idea or as others have said it can contribute to heat water/aircon to cool in summer.