# Solar electric to heat outdoor water pipe?



## Joel_BC (Nov 10, 2009)

I have a question concerning the possiblity of using solar (pv) in an isolated special application, here in our rural situation. Our area (latitude just above the 49th parallel) is prone to recurrent cloud during the year. That, coupled with mountains looming to the east and west making high horizons, has generally discouraged people from trying to use pv for household electrical supply.

But I'm wondering about the use of a solar st-up (panel, some sort of battery, and two-conductor "heat tape") to keep a 30 foot section of black-plastic water pipe from freezing during cold weather. This pipe is part of a gravity-feed water supply for several households. A total length of pipe of about 400 feet runs between a collection basin in a creek and a distribution box (from which individual water lines emerge and run, buried, to each of the home sites). The 30 foot section in question is unburried, as it runs over gently sloping bedrock. 

We've tried covering the pipe with a commercially available foam-rubber jacket, but this has not worked out too well, due to rodents chewing away the rubber for nest making. A thick fluffy layer of straw in the late fall of each year has been of some value, though winds can diminish the straw layer, and rain and snow compact it and wet it, reducing its insulative value. 

A steady inflow of water can be maintained into the pipe, but when the air temp gets down to about 10* F or lower that 30 foot section of pipe has a habit of freezing. Then ice then spreads throughout the longer length of pipe. I believe that keeping the unburried portion of the pipe warmed by a heat tape might be able to keep the water from building up ice layers within the pipe.

In the specific location, sun intensity varies during winter days. Skies are sometimes clear and bright, sometimes quite cloudy. A panel could be positioned to catch sunlight (bright or diffused) for a minimum of five hours in deepest winter, and seven hours in the shoulder seasons. We'd need to capture the output in some sort of battery - and I know that the overnight cold could have an effect on the chemical activity & effectiveness of certain types of batteries in an outdoor situation. The electrical-current output from the system would have to be enough to provide sufficient warmth via the heat tape.

If you're reading this, have you heard of a pv set-up working in an application (and situation) anything like this? What can you tell me? Thanks.


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## Gray Wolf (Jan 25, 2013)

Resistance heating uses a lot of power and generally won't work unless you have a lot of panels, inverter, charge controller, and a lot of batteries. And a few days without sun will pretty much end that exercise unless you bring a generator to the battery bank to recharge them.

You can buy a lot of wire a lot cheaper. If only a few hundred feet, why not run ac to where you need heat?


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## TnAndy (Sep 15, 2005)

Cheapest solution ?

Put the mice loving foam on the pipe, then slide the supply pipe inside another, larger piece of Sch40 PVC. Seal the ends with either a cap with a hole of the exact OD of the supply pipe, or canned foam (the hard kind) and aluminum tape.


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## Joel_BC (Nov 10, 2009)

Gray Wolf said:


> Resistance heating uses a lot of power and generally won't work unless you have a lot of panels, inverter, charge controller, and a lot of batteries. And a few days without sun will pretty much end that exercise unless you bring a generator to the battery bank to recharge them.
> 
> You can buy a lot of wire a lot cheaper. If only a few hundred feet, why not run ac to where you need heat?


Dang!

This is the mountains of western Canada. The closest of the households using the system is maybe 1200 ft away.


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## wy_white_wolf (Oct 14, 2004)

Everything I looked at showed a low of about 0.8 hours insolation for the winter. A PV system would run in the area of $20,000 to $30,000 for ever 100W of tape you wished to run. And then you'd have to replace the batteries every 5 to 7 years.

Be far cheaper to start hauling in fill dirt to build the area up by 4 foot to bury the pipe.

WWW


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## Joel_BC (Nov 10, 2009)

TnAndy said:


> Cheapest solution ?
> 
> Put the mice loving foam on the pipe, then slide the supply pipe inside another, larger piece of Sch40 PVC. Seal the ends with either a cap with a hole of the exact OD of the supply pipe, or canned foam (the hard kind) and aluminum tape.


Hmmm... Given the info in the replies, I suppose this may be the best option. The hard foam (canned) for the ends is the element we hadn't thought of before. Thanks. Possibly have to cut out a channel down the length of the outer hard sleeve (pipe), to allow it to spread a little - so as to be able to slip the foam jacket in through the whole length. Then slip the whole works over the water pipe.

There are a lot of "ifs" between the concept and the actual thing, but it _sounds_ like it could work. And yes, it would be much cheaper.


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## Jim-mi (May 15, 2002)

Under the heading "wire cheaper than solar" would be to run a 220v extension cord. A step down transformer 220--110 at the far end to heat tape with pipe with in a pipe is another option.
With 220v there will be less line loss.
But with a heat tape lower voltage will work.


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## Nimrod (Jun 8, 2010)

wy_white_wolf said:


> Everything I looked at showed a low of about 0.8 hours insolation for the winter. A PV system would run in the area of $20,000 to $30,000 for ever 100W of tape you wished to run. And then you'd have to replace the batteries every 5 to 7 years.
> 
> Be far cheaper to start hauling in fill dirt to build the area up by 4 foot to bury the pipe.
> 
> WWW


Insulation in a pipe will only have a minimal effect. I'm with WWW. Bury the pipe under enough dirt so it's below the frost line. Also cover it with hay and don't disturb the snow over it.


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## TnAndy (Sep 15, 2005)

Minimal effect may be all it needs. 

I have a similar situation where I have a 3/4" pipe that lays on the ground down from the spring collection box down to the storage tanks.....about 150'. Water runs in it constantly, and has never frozen, and we get temps down below zero here....it was -8 couple weeks back, and record is -25. 

I do have a good, positive slope on it. Perhaps Joel has a place where the water line is nearly level, and the water doesn't move well.....that's the only way it would freeze down to -10 or probably lower. You keep water flowing good, and it's pretty hard to freeze.

UNLESS the line from the spring to the "distribution box" doesn't have an overflow AT the distribution box ? 

If that is the case, and nobody in any of the households is using water at the time ( like the middle of the night ), then right there is the problem.....the water in the line from the spring isn't flowing when water isn't being taken off the distribution box, and thus, WILL freeze.

Simple solution....put an overflow pipe near top of the box ( I have one on my tanks with a separate line that feeds down to my fish ponds), and you'll solve this issue very easily.


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## Jim-mi (May 15, 2002)

Don't know about your area there in BC . .But here in my area of Michigan the frost line data used is --42"---deep.....
It was -21 F this morning . . . .
Many many small towns are advising to leave the water running because of oh so many places freezing pipes.........

All this to say that covering that exposed pipe with at least 3' of earth might not be easy . . .?!?!

Like Andy says . .a constant flow might be the easy way.....

Can you rent a trencher . . ???


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## Gray Wolf (Jan 25, 2013)

If bringing in 4-5 feet of fill is impractical, maybe try this? 

Put down just enough dirt to cover the pipe and get a flat area about 3-4 feet wide on each side of the pipe.. Then put down sheets of 2" or thicker foam board insulation centered on the pipe. (The kind that does not absorb water) Your exposed run will need quite a few sheets and it's not free but ....... One layer deep may do it but two or more would be better. Look on the specs for the product you are considering to see how many inches of foam has the same R as a foot of dirt and go from there. Then cover the whole deal with 6" or so of dirt to keep the foam board from blowing away and so weeds can grow back.


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## Joel_BC (Nov 10, 2009)

Nimrod said:


> Insulation in a pipe will only have a minimal effect. I'm with WWW. Bury the pipe under enough dirt so it's below the frost line. Also cover it with hay and don't disturb the snow over it.


Well, we've had many years to contemplate these basic ideas. The pipe has to flow over a sort of "goat trail" that in some places is less than two feet wide, over bedrock that's right at th surface. No soil there. Unfortunately, much of this rock goat trail is at a fairly shallow slope, too.

Plus, we have to have a way to walk on that ledge. It's easier to walk beside the foam covered pipe than it is on a fluffy layer of straw, which can be very slippery.

So the best we'd come up with is the foam-rubber jacket, and the layer of straw.



Jim-mi said:


> Many many small towns are advising to leave the water running because of oh so many places freezing pipes.........


We have an overflow at the distribution box. So there's always been that provision for keeping a flow going (atttempting to do so anyway).



Jim-mi said:


> All this to say that covering that exposed pipe with at least 3' of earth might not be easy . . .?!?!


Yes, you're correct. LOL


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