Fresh Heating idea for 2007

Joe Brix

> heat water with collectors to heat your <BR>
> house.<BR>
> <BR>
> PV's are less than 15% efficient, water <BR>
> is more around 80%.<BR>
> <BR>
> figure out your heatloss, <BR>
> 3,412 btu's = 1 kilowatt.<BR>
> <BR>
> from Real Goods <BR>
> catalog, 1 kilowatt of PV runs about $5,000. <BR>
> then a 1,000 watt invert about $2,200, grid <BR>
> compatable.<BR>
> <BR>
> i would use PV's for lighting. <BR>
<BR>

flanger

Fresh Heating idea for 2007 (updated)

Here in CO we have some tremendous incentives to install PV solar in 2007 - rebates as much as 50% of installation. Since my existing hydronic radiant floor heating system is approaching end of life, I am considering combining a Solar PV grid-tied system with electric radiant floor heat.

When my current system dies, I would like to avoid ripping out the existing Solaroll-in-concrete (on all 3 floors - major demo!) and instead just find an alternative heating approach, such as hot-water baseboard (to reuse existng boiler and copper lines). But I hate to give up the warm floors. So I am considering this electric radiant alternative.

For a 2700sf home, electric radiant floor would be very expensive. But if I over-size my solar installation, I guess I could get free heat and continue to experience the joy of warm feet! Over the years, I expect it would be close to maintenance free. I would appreciate any feedback on this fantasy as I start to consider replacement heating systems.

Fred

jp_2

use solar collectors

heat water with collectors to heat your house.

PV's are less than 15% efficient, water is more around 80%.

figure out your heatloss, 3,412 btu's = 1 kilowatt.

from Real Goods catalog, 1 kilowatt of PV runs about $5,000. then a 1,000 watt inverter about $2,200, grid compatable.

i would use PV's for lighting.

Joe Brix

Wouldn't a 2 coil indirect tank

> heat water with collectors to heat your

> house.

>

> PV's are less than 15% efficient, water

> is more around 80%.

>

> figure out your heatloss,

> 3,412 btu's = 1 kilowatt.

>

> from Real Goods

> catalog, 1 kilowatt of PV runs about $5,000.

> then a 1,000 watt invert about $2,200, grid

> compatable.

>

> i would use PV's for lighting.

Joe Brix

Wouldn't a 2 coil indirect tank

> heat water with collectors to heat your

> house.

>

> PV's are less than 15% efficient, water

> is more around 80%.

>

> figure out your heatloss,

> 3,412 btu's = 1 kilowatt.

>

> from Real Goods

> catalog, 1 kilowatt of PV runs about $5,000.

> then a 1,000 watt invert about $2,200, grid

> compatable.

>

> i would use PV's for lighting.

Joe Brix

Wouldn't a 2 coil indirect tank

be the simplest config? Just pipe a gylcol loop throught one coil with check valves Only run a circulator when the solar panel's at 120+.

Gordy

Cha Ching

Doable but thats a whole lot of PV panels to power electric floor radiant plus converters ect to run it.

Sunny days are the days with lower demand so now ya gotta stow the power.

Gordy

kevin coppinger_4

How about...

home running pex tubing to panel rads and as one poster said use the solar panels to heat up a storage tank w/ the 2 coils....you could a control to put the rads on constant circ. almost the same idea...then put the new floor heat in just certain area (tile in baths and or kitchen)...kpc

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flanger

Good feedback - gonna research panel radiators becuase I don't know anything about them. Sounds like a better/nicer option then baseboard radiators.

But remember with a grid-tie system, I will run my meter backwards all sunny day long to acquire the kWh credit I would need to use the grid in the evening for powering any electric heat - hopefully I would break even. The beauty of Xcel letting solar users run their meters backwards (during sunny hours) is providing a way to essentially let me "store my energy" on their grid.

kevin coppinger_4

look at....

buderus.net for the panels....kpc

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jp_2

looks at my post again fred

for 1,000 watts of PV, will run you about $7,500.00.

so every hour you sell back 1 kilowatt hour. if the power company pays you 10 cents per kilowatt hour, how many year hours til pay back? if 10 hours of sunlight per day give you $1.00 or 7,500 days til you break even!

so much for those big smiles watching the meter spin backwards at a snails pace.....

hr

Don't write off that Solaroll too soon!

for the most part the only tube failures are when a slab cracks and shifts and rips the tube, or they become completely plugged with rust and corrosion from eating the ferrous components.

I would flush all the lines and test them. if you don't have any leaks, use a HX to keep the "roll" seperated from any ferrous components.

I must say that mat system, counterflow concept really provided for an incrediably even, consistent floor surface temperature.

But... you would be wise to have a plan B in the back of your mind.

hot rod

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flanger

OK , this was a bad idea. Now I understand the HUGE difference in performance. Doing a little math, I would need to TRIPLE the size of the PV installation (from just lighting/electric) to support electric heat - not what I was calculating for. I would be 6ft under before that system could ever have been paid for.

I will try to keep the solaroll going as long as possible. It is already on a HX and I will keep flushing it annually. But those 1/4" rubber tubes aren't flowing too well any more, and the manifold connections are looking pretty corroded. When all 4 zones are running, the pressure drops to almost zero (prob due to soft expanding rubber sections between each manifold and where it goes into the concrete). I see HW baseboards and panels in my future. I would like to suppliment with solar hot water, but don't have room for a large storage tank. I only need heat in the evening because of the passive solar design of the house.