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# Solar heated water into radiator system

#1
12-18-13, 09:39 AM
Member
Join Date: Dec 2013
Location: United States
Posts: 1
Solar heated water into radiator system

Good morning.
I have a question, I have a 1940's home. Radiator heat from gas fired boiler. Recirculator pump 2 pipe heating system. I am building a solar powered heating system and was wondering if I can incorporate this into the existing water pipes (proper flow direction) and bypass the boiler? The heated water tank will reach between 170`-190` which, I think, would be sufficient to heat the 1400sq/ft home. Any feedback would be appreciated.

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#2
12-18-13, 11:43 AM
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Join Date: Oct 2006
Location: USA
Posts: 23,539
The heated water tank will reach between 170`-190` which, I think, would be sufficient to heat the 1400sq/ft home
How large is the tank? Chances are not big enough to store enough BTUs to effectively heat the home.

Thinking in terms of BTUs, the definition is " ONE BTU is the amount of heat required to raise ONE pound of water ONE degree "

Let's think about the coldest day of the year. At 1400 sq ft, you probably have a HEAT LOSS of approximately 35,000 BTU PER HOUR.

Let's say that your tank is 500 gallons.

If you start pumping the 180° water in that tank into your heating system, you will get useful heat out of it until perhaps down to 100° or so. That's an 80 degree difference.

500 gallons of water weighs 4175 pounds.

The number of USEFUL BTU in that tank then becomes 80 (degree difference) times 4175, or 334,000 BTU

Your home will require 35,000 BTUH to be heated, and this means that a 500 gallon tank of 180 water would be able to heat your home for a bit under 10 hours.

How long does it take to recharge that tank?

For this to work, you would have to be able to put an average of 35,000 BTU back into the tank PER HOUR.

To put this another way, you need to be able to STORE ENOUGH HEAT in the water tank to get you through periods of darkness, and bad weather, in order to heat the home, AND be able to collect the heat again quickly enough to recharge the tank when the sun IS out.

You MIGHT be able to do this with a LARGE array of collectors and at LEAST a 1000 gallon tank.

Of course, during periods when the weather is not that cold, you could get by with less, but don't expect to be able to use the solar output for 100% of your heating needs.

#3
12-19-13, 12:43 AM
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,495
Thanks, Trooper, everything that I would have posted.

Solar is simple in concept but people often get lost in the details. It takes a whole lot of storage to maintain solar over the night and cloudy days and that takes space. The capital costs of solar, especially in areas that are not bright and sunny during most days, can be absolutely prohibitive. Yes, the cost of heating is low when extended over the thirty (or more) years of useful life of a good system but the cost of construction is quite high.

#4
12-19-13, 04:35 AM
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Join Date: Jul 2009
Location: Toronto
Posts: 1,174
Supplementing solar to an existing system makes sense. Since your on natural gas (I assume) not propane. Your cost per therm is quite low.

If you use the solar in the day, and set back your stats (assuming you work during the day), you might be able to design a system with enough solar output to look after heating during this period for 70% of the time.

This is not a bad thing, as you don't need to take all the load all the time to save money.

The one problem you will have to overcome is dealing with 5-10 times more output in the summer when you don't want or need it. If you have a pool then you can dump the heat into the pool, if not you will find that your solar tank quickly charges and your left with energy that you need to dump somehow.

You need to know your heat loss and balance the capital cost of the system with the possible savings and the cost to run your fosil fuel boiler.

Another approach, use PV panels and a small electric boiler. Set the system up so that in the summer the energy from the PV array can be sold back to your electrical utility. Up here we could get up to 82 cents per KW/ hour generated.
I think at this level it makes more sense to dump all the energy into the grid.

Basically, use your capital dollars wisely.

#5
12-19-13, 05:24 AM
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Join Date: Oct 2006
Location: USA
Posts: 23,539
Up here we could get up to 82 cents per KW/ hour generated.
EIGHTY TWO CENTS / KWH ?

That's gotta be a typo, NO?

Did you mean EIGHT POINT TWO ?

Down here we only pay about FIFTEEN cents / KWH, I can't imagine that the utility would pay me more than five times that to sell it back to them. If that were the case every inch of my roof, yard, and driveway would be covered with panels. I'd have to park in the street.

#6
12-19-13, 03:48 PM
Member
Join Date: Jul 2009
Location: Toronto
Posts: 1,174
Oh No...
82 C/ KWh

Yep some smart overpaid exec dreamed that up.
That allows us, the lowly hydro bill payer, to subsidize green power.
Let's look at the math..
I think with all the crap added up we pay about 18 cents a KWh (and I would have to check that for accuracy). Yet we (as the hydro utility) will buy the power for 82 c / KWh... for quite the remarkable net loss.
Luckily they have reduced it to about 50 +- cents. but not before a lot of people locked in at 82 cents for 20 years.

#7
12-19-13, 06:06 PM
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,495
Eighteen cents per kilowatthour for hydro generation? That's insanely high.

I just had my rates raised last month and because of some smart wheeler-dealering (NOT!) several years back with Enron my power utility has (I think) the highest rate in Washington state for a publicly owned utility at just under nine and one-half cents a kWh. Snohomish county PUD only generates about 5% of their power, buys about 80% from the Bonneville Power Administration and the rest on the open market, some by long-term contract and other by spot needs/prices.

#8
12-20-13, 04:45 AM
Member
Join Date: Jul 2009
Location: Toronto
Posts: 1,174
Furd, Ontario was one of the poorest run crown corporations.
They were (are) losing money faster than we could count it.

So, they decided to privatize it.
So now we pay 5 or 6 cents for generation, 3 cents or so for delivery, another 3 or 4 cents for something else, then.... and you love this.... we have to pay off the crown corps debt. We pay a debt reduction charge that will seemingly never terminate and we don't even get an accounting of the debt.

Oh, then to add to the misery, the government has to put 13% HST (tax) on it cause they are not getting a "taste" on everyones money.
Taxed to death... with no end in sight

The things you can do when your a monopoly, and own the energy board that regulates you.

I hope I am not coming across too bitter :-)