solar floor heating

[Thomson Tim]

I am probably dreaming here but here goes.
Last fall I installed a air tight wood stove and I dropped my natural
gas consumption down by 90%. I used the stove to heat the 1000 square
foot main floor of a split bungalow. The basement was unusable because
of the cold..........anyways here is what I am doing and almost done. I
have installed ceramic tiles on the entire living section of concrete in
the basement with electric in floor heating. The total will be about 8
or 9 thousand watts of draw @ 110v.

I have about 10,000.00 more CDN to blow and was just thinking what could
I get for solar panels to put on my roof? Could I dump the energy
directly into the floor heating system? How many watts of solar can I
put on the sunny side of my roof 40x13 feet (520 square feet) and how
much money? I am not worried about the pay back I just want bragging
rights lol. My main goal is to be able to keep the pipes from freezing
in the basement. I don't want to get into inverters or batts yet and
wont discuss it. Just a few simple switches to go from line power to
solar power in the floor.

I know that electric is the most expensive back up heat but I just hate
the gas co and plan on ripping out the gas meteor. I also plan on
converting my hot water to electric and cooking stove to propane. To
keep my house legal I also have to have a heat source that will maintain
the house at 21 c all year so I will convert the furnace as well.
Wood is free here where I live other than your time and a little gas for
the chainsaw and truck. I also bought one of those electric wood
splitters. Awesome machine......I don't have to be so picky when getting
wood....It says it will split a maximum of 20" by 10" round. Ha all the
garbage that people can't split with an ax I take. I easily split 20" by
24" round

 

[Thomson Tim]

One more question I dont want to max out my 100 amp feed.
Whats the formula for watts volts amps. How many amps does 8000 watts need
at 110/120 vac

 

[John P Bengi]

You better save your $10K to pay the electric bill. This would be a waste of
time and energy and the gas company will have the last laugh on your dime.

Solar to PV to electric to resistance heating is a very, very inefficient
technique and a waste of everything. Find a way to store or move the solar
heat directly where you want it. Much more efficient. Save the PV for
electric appliances and lights etc. Use the solar to assist your gas hot
water heater in a preheat mode. Put in a water heat exchanger for your
showers etc.

 

[Anthony Matonak]

Thomson Tim wrote:
....

I have about 10,000.00 more CDN to blow and was just thinking what could
I get for solar panels to put on my roof? Could I dump the energy
directly into the floor heating system? How many watts of solar can I
put on the sunny side of my roof 40x13 feet (520 square feet) and how
much money? I am not worried about the pay back I just want bragging
rights lol. My main goal is to be able to keep the pipes from freezing
in the basement. I don't want to get into inverters or batts yet and
wont discuss it. Just a few simple switches to go from line power to
solar power in the floor.

....

Most PV panels run around 10 to 12 watts per square foot. This means
you can install around 5,000 to 6,000 watts of PV panels at a cost
of somewhere between $25,000 to $40,000 depending on various factors.

You would do better to install solar air heating panels on the roof
and duct the air down to the basement. Not only would it be more
efficient (up to 80% instead of 12%) but it would also be a fraction
of the price. These kinds of heating panels can even be home-made
out of ordinary materials found in home improvement stores so the
savings in cost over PV can be very significant.

Anthony

 

[Thomson Tim]

No clue next!
How in the hell can a direct usage of solar be less efficient than storing it?
I will store some at a later date thanks any ways.

 

[Thomson Tim]

Wow I guess I better turn the floor off before I turn on the dryer.

 

[John P Bengi]

Turning solar into electricity is at best about 13% efficient. Then the
storage and recovery of the electricity is about 80% at best.

Read the other reply to your post by Anthony.

 

[Thomson Tim]

Do you mean turning DC into AC?
Thats not the plan. I would dump the DC directly with some regulation into the
resistive wires. Its also coldest here when the east wind comes around the
mountains
So I am looking at a wind turbine as well.

 

[Derek Broughton]

I have about 10,000.00 more CDN to blow and was just thinking what could
I get for solar panels to put on my roof? Could I dump the energy
directly into the floor heating system? How many watts of solar can I
put on the sunny side of my roof 40x13 feet (520 square feet) and how
much money? I am not worried about the pay back I just want bragging
rights lol.

Worried or not, using PV to create electricity to heat a floor is a heck of
a lot less efficient than using solar glycol-filled panels to circulate
heat through the floor. Planning is kind-of important.

My main goal is to be able to keep the pipes from freezing
in the basement. I don't want to get into inverters or batts yet and
wont discuss it. Just a few simple switches to go from line power to
solar power in the floor.

How are you going to do that? Your floor is 110V resistive heating. You'd
need to invert the power from the panels.

I know that electric is the most expensive back up heat but I just hate
the gas co and plan on ripping out the gas meteor. I also plan on
converting my hot water to electric

That's just not smart. Get a solar hot water system from Thermo-Dyanmics
(Dartmouth, NS).

and cooking stove to propane.

And you think dealing with the tanked-gas company will be any better than
dealing with the piped-gas company? Don't bet on it. Superior Propane has
a virtual monopoly on the propane market in much of Canada.

To
keep my house legal I also have to have a heat source that will maintain
the house at 21 c all year

You're kidding? I _never_ keep my house that warm!

 

[Derek Broughton]

No clue next!
How in the hell can a direct usage of solar be less efficient than storing
it? I will store some at a later date thanks any ways.

Well Bengi tends not to be too clued in, but you aren't talking about a
"direct" use of solar. You're talking about converting the photons to
electricty (much less efficient than converting them to heat), then
converting them to heat. Using a solar hot-water system you avoid the loss
of efficiency at the panel.

 

[Derek Broughton]

You would do better to install solar air heating panels on the roof
and duct the air down to the basement. Not only would it be more
efficient (up to 80% instead of 12%) but it would also be a fraction
of the price. These kinds of heating panels can even be home-made
out of ordinary materials found in home improvement stores so the
savings in cost over PV can be very significant.

Sure, this is probably easiest for a system that has to be retrofitted. For
a Canadian manufacturer, look up "Cansolair".

 

[Thomson Tim]

All along I was talking electric solar panels

No, he means PV into heat. That's insanely wasteful.

 

[Thomson Tim]

Maybe I meant solar electric panels....so how many watts od DC per square foot
do panels put out?Any ideas of the best place to get them in Alberta?

 

[Thomson Tim]

Worried or not, using PV to create electricity to heat a floor is a heck of
a lot less efficient than using solar glycol-filled panels to circulate
heat through the floor. Planning is kind-of important.
Not an option the floor was poured 45 years ago.

How are you going to do that? Your floor is 110V resistive heating. You'd
need to invert the power from the panels.

Invert the power to what? AC? Resistive heating doesnt care if its ac or dc
Just have to do the math on the volts and amps to get the rated output.

That's just not smart. Get a solar hot water system from Thermo-Dyanmics
(Dartmouth, NS).

I guess I should have said Electric on demand...more than tankless gas but
still cheaper than tanked storage gas water.

And you think dealing with the tanked-gas company will be any better than
dealing with the piped-gas company? Don't bet on it. Superior Propane has
a virtual monopoly on the propane market in much of Canada.

I talked to alot of locals here and all are happy with the differant propane
suppliers.....my choice is the Coop
They rent a four hundred litre tank for 12.00 month......cheaper than the gas
co fixed fees of about minimum fifty a month.
Its now about 650.00 a year just to have a gas metour on the wall now with no
consumption. Once I get rid of the gas hot water I doubt that I would use four
hundred liters of propane per year. The only time that my furnace would kick in
is when I am not home to throw a log on the fire. I have allready proven that.
All last winter I consumed 14 gigajouls of natural gas all for domestic hot
water. More than anything just to stay insured and legal I still have to have a
alternate heat source other than wood.

You're kidding? I _never_ keep my house that warm!

Not kidding .....municipal bylaw I read it. Part of the spec to meet code when
you install wood stoves here.
I must mantain a heat source that can maintain 21 c even when no one is home.
Doesn't mean I have to keep it that warm it just means be ready if needed.

 

[Derek Broughton]

Invert the power to what? AC? Resistive heating doesnt care if its ac or
dc Just have to do the math on the volts and amps to get the rated output.

I suppose... Come to think of it, I'm not sure how well an inverter would
work either without a battery backup. Still it gets pretty hairy trying to
match panels to get to a reasonable DC voltage - and I'd expect the heating
vendor to disavow any responsibility if you put anything but 110VAC into
it.

I guess I should have said Electric on demand...more than tankless gas but
still cheaper than tanked storage gas water.

It doesn't matter. You're looking at the wrong ways to produce heat (btw, I
don't think you can get a tankless electric water heater that will work on
your 100Amp service). If you want heat from solar, collect it via liquid
or air collectors. For direct heating, air is probably good, for hot water
use a liquid collector. Then maybe use a tankless propane heater to keep
it up to required temps.

Not kidding .....municipal bylaw I read it. Part of the spec to meet code
when you install wood stoves here.

Yeah, I didn't _really_ think you were kidding. I just see red when I hear
such stupid rules...

I must mantain a heat source that can maintain 21 c even when no one is
home.

Like, what's wrong with 3C, when no one is home? Bureaucrats!

 

[News]

Turning solar into electricity is
at best about 13% efficient.

But as you do not pay for the input, it is 100% efficient.

 

[News]

Worried or not, using PV to create electricity to heat a floor is a heck of
a lot less efficient than using solar glycol-filled panels to circulate
heat through the floor. Planning is kind-of important.


How are you going to do that? Your floor is 110V resistive heating. You'd
need to invert the power from the panels.

The elements in a floor don't care if ac or dc runs thought it. You just
need to find out have dc voltage/current is applicable.

 

[daestrom]

All along I was talking electric solar panels

And that is silly, exactly what everyone is trying to tell you. Using a
photovoltaic panel, it converts about 13% of the sunlight that shines on it
into electricity. The rest of the radiant energy that shines on it just
warms it up. So now you have 13% of the energy from the sunshine in the
form of DC electricity. Run that through resistance heating (100%
efficient) and you have 13% of the energy from the sunshine warming your
floor.

Instead, if you use a thermal solar collector (warm air, or warm water), you
get a much higher percentage of the energy from the sunshine deposited into
the warm water. Circulate the warm water under your floor, and even if it
loses some heat in the piping as it runs down from the roof, you still are
much further ahead when you count the number of BTU's delivered to the floor
vs the square footage of collector area.

A thermal collector can capture more than 50% of the total energy from the
sunshine that shines on it (even as high as 80-90 %). Thermal collectors
are much cheaper than photovoltaic on a per square foot basis. If all you
want is low-grade heat, forget about the photovoltaic panels and look at
thermal collectors.

daestrom

 

[daestrom]

But as you do not pay for the input, it is 100% efficient.

'Efficient', maybe. But a very costly way to heat water for a radiant floor
system. Thermal collectors with the same surface area are *much* cheaper.
And since thermal collectors can deliver more energy to the floor for a
given collector surface area, the savings are two-fold (cheaper collectors,
and smaller total collector surface needed).

daestrom

 

[daestrom]

Maybe I meant solar electric panels....so how many watts od DC per square
foot
do panels put out?Any ideas of the best place to get them in Alberta?

For a given square footage, 'solar electric' panels put out between 1/4 and
1/5 the 'watts' for heating as simple thermal collector panels. So for a
given *heating* need, you would need 4 to 5 times the collector surface area
using 'solar electric panels' as you would using simple thermal collectors.

daestrom