Solar Panel > Battery and 12V Heat Tape
Solar Panel > Battery and 12V Heat Tape
(OP)
I've recently been handed the task of trying to design a stand-alone system to heat a 10 foot section of water pipe during the winter months.
Let me preface with the fact that I'm an environmental engineer and it's been a while since my Intro to Electrical classes.
I figure I'll need a 10-20W solar panel, a 12V battery (maybe 2?) and either acquire or create a section of 12V heat tape. I figure avoiding inverting into a 120V heat tape should conserve a considerable amount of power/help efficiency?
The site is very sunny. Perhaps a heat tape wouldn't be necessary if the section was insulated well with heat strips such as (http://www.mcmaster.com/#heat-tape/=8g3q46)?
At this point the solution is very open ended, so I'd appreciate any different directions and/or OTC solutions or ideas you electrically adept folks may have. Thanks for your time!
Let me preface with the fact that I'm an environmental engineer and it's been a while since my Intro to Electrical classes.
I figure I'll need a 10-20W solar panel, a 12V battery (maybe 2?) and either acquire or create a section of 12V heat tape. I figure avoiding inverting into a 120V heat tape should conserve a considerable amount of power/help efficiency?
The site is very sunny. Perhaps a heat tape wouldn't be necessary if the section was insulated well with heat strips such as (http://www.mcmaster.com/#heat-tape/=8g3q46)?
At this point the solution is very open ended, so I'd appreciate any different directions and/or OTC solutions or ideas you electrically adept folks may have. Thanks for your time!





RE: Solar Panel > Battery and 12V Heat Tape
Batteries drop off in efficiency when they get cold. If your batteries freeze so might your water pipe. I would put them in an insulated enclosure ( with a vent) and a heater of some kind. You may need a bigger solar panel.
RE: Solar Panel > Battery and 12V Heat Tape
How hot is the water?
TTFN
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RE: Solar Panel > Battery and 12V Heat Tape
Presumably the pipe is coming from somewhere and going somewhere. For freeze protection you may be better to consider constructing a duct between the "From" and the "To" and running the pipe in the duct.
BTW, what may be the consequence of a heating system failure?
Have you considered the possibility of installing monitoring and solenoid valves to close the flow and dump the pipe contents to prevent freeze up when the solar system fails. (I give it about 3 to 5 years max from my experience with solar. But batteries may be better now.)(Less if there is a an extended period of overcast skys.)
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Solar Panel > Battery and 12V Heat Tape
1 in OD pipe
40°C delta from water to air temp
25 W/m^2-K convection+radiative loss to air
Using a 35mm thick vacuum insulation with 0.003W/m-K thermal conductivity, the heat loss from the water is only about 2.25 W, which could be made up by your heater.
http:/
TTFN
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RE: Solar Panel > Battery and 12V Heat Tape
A small drip is less expensive and more reliable than batteries. And, of course, insulate.
RE: Solar Panel > Battery and 12V Heat Tape
Standard scenario: In rolls the cold weather => overcast => solar cell output drops to 10% design value => freak snow storm => batteries die => pipe freezes and splits => batteries freeze and split shortly after.
Furthermore batteries have a life cycle. Without careful testing and monitoring after a time the end result will be insufficient battery capacity and spit pipe.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Solar Panel > Battery and 12V Heat Tape
Only you would know the environmental impact of a pipe burst due to freezing. You should be the one opposing this idea.
Rafiq Bulsara
http://www.srengineersct.com
RE: Solar Panel > Battery and 12V Heat Tape
Rafiq Bulsara
http://www.srengineersct.com
RE: Solar Panel > Battery and 12V Heat Tape
And while I hear a lot of naysaying, do we have any more suggestions on the constructive side?
I'll answer some of the questions first.
The system is for freeze protection. The pipe is 6" diam, flowing full, and flowing most of the time. It is fairly well insulated, but could be improved upon. Temps can get down to -20F. The site typically does not stay overcast for long, but it sounds like just 3 days would be enough to completely drain a battery. The water starts at ~55 deg.
I can certainly scale up if it'd make the difference... 5 batteries? 10? Deep Cells? 60W panel? Wind actually has a lot of potential.
The site has full time employees and it's not a problem to have the batteries regularly checked up on. Burial is not an option for grade and rock reasons.
So aside from using wind as well as solar and keeping the water running, who's got some other fresh ideas?
RE: Solar Panel > Battery and 12V Heat Tape
Given that, you're probably looking at lots more batteries, and lots more solar panels. Have you considered a gas generator as an addition to the solar panels? I'm guessing that 5 panels is a bit of an overkill, but it would allow the batteries to be charged emough in a few hours to make it through the night and still have power to run the heaters during day.
If there are people around, then what are they using for power?
TTFN
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RE: Solar Panel > Battery and 12V Heat Tape
RE: Solar Panel > Battery and 12V Heat Tape
Keith Cress
kcress - http://www.flaminsystems.com