Thoughts on solar in snow country

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LakeLeaf

Well-known member
Joined
Jun 7, 2010
Messages
1,424
Location
South Lake Tahoe, California
I like the idea of using solar energy to generate your own power. Unfortunately I live in snow country and the roof is covered in snow from Oct/Nov well into April or sometimes even May - usually a good six months. With a couple of feet of insulation in the attic, in a good winter I have more then another story of snow on the roof!

In order to install solar, I'd have to have a way to melt the snow on the panels. I'm thinking that I might be able to get enough solar on the side of the house to heat up water pipes, send that warm water to the solar cells on top of the roof and heat them enough to get rid of the snow. There is a whole lot of solar gain when you are at almost 7000 feet with more then 320 days of sunshine a year - it's just that darn snow that gets in the way.

Has anyone ever seen a solar system designed to keep itself clear of snow?

The second major issue I have to overcome is that I'd likely have to tilt my solar panels off the roof to get the right angle. We sometimes have 50-70+MPH winds here, so the installation would have to be able to withstand some pretty strong winds. Any suggestions on this?

Lastly, the squirrels like to climb the 100 foot tall pines around the house and chew off the pine cones so that they drop onto the roof. I'd be a little worried that a pine cone would hit a panel and ruin it - I don't know how tough these panels are.

Am I looking at too many obstacles here for an effective solar system?
 
LakeLeaf said:
Lastly, the squirrels like to climb the 100 foot tall pines around the house and chew off the pine cones so that they drop onto the roof. I'd be a little worried that a pine cone would hit a panel and ruin it - I don't know how tough these panels are.
I don't know. If I had ever been hit by a pine cone dropped 100 feet I might well have a different opinion, but I suspect that is the least of your worries. We have a cluster of three very tall pine trees about 100 feet southwest of our house (not on our property), and they make our solar output plummet as the sun dips below their tops on winter afternoons. I can't imagine what they would do to the output if they were close enough for pine cones to hit the roof. [Given how straight pines grow, those squirrels must have really strong throwing arms. :lol: ] Oh, wait, you did say something about wind, didn't you?

Here is a half serious thought - we get no snow at all, but our solar panels produce an average of about 6 MWh/year in the five months from May 1 to Oct 1 and only about 5 MWh/year in the seven months from Oct 1 to May 1. Lake Tahoe is a couple of degrees further north than we are, so the difference is likely to be even a bit more pronounced for you. You might consider just letting the solar system hibernate all winter.
 
I think the snow would melt away after a few days with the sun hitting the metal frame as the snow reduces as the day go by.
 
If you have squirrels dropping pine cones on your roof, it sounds like snow is the least of your problems and that shading would prevent you from using solar.......???
 
hmm. i would be worried about roof loading. add solar panel weight plus that much snow?? keep in mind; the Metrodome (you know the stadium with the "new" sunroof?) was supposed to be able to handle it and it is in Minnesota...

how much property do you own? up here many with land simply put it up "near" the house. can you do that?
 
LakeLeaf said:
We sometimes have 50-70+MPH winds here, so the installation would have to be able to withstand some pretty strong winds.
How about getting some small wind power generator instead ?
 
What about a ground mounted array? Maybe a couple pedestal mounted panels. Sweeping snow off would be easier and much safer than on the roof. A friend has two pedestals with four panels on each. Granted he does have room and no shading or squirrels. The output would be reduced with a smaller array but think of it as a supllemental source.
 
well you could design a system that incorporates the "avalanche" effect. where warm water is pumped thru the system creating a melted super thin layer of water. the slope of the roof would allow the snow to just slide off.

i would still go with ground mounted system if you have the yard space. this allow the perfect alignment which is not always possible
 
Call a professional and get and estimate and recommendation. This is the easiest way to get accurate answers.
 
EVDRIVER said:
Call a professional and get and estimate and recommendation. This is the easiest way to get accurate answers.

You mean like calling my local Nissan dealer and asking questions about this new Nissan LEAF EV?

Ya that worked well, in the beginning the first dealer told me they wouldnt be available until 2012. Second one said they arent planning to sell or support the LEAF because they do not think they will make any money off the dealer markup.
Third one said, the LEAF? What's that........ :shock:

I think their are more informed people on this forum than all the commissioned based sales experts out in the field.
Get some good ideas, do your own research and then approach the experts with your questions.

just my two cents
 
We have 34 panels on our roof and we are at an elevation of nearly 7,000 ft., but we are in AZ and our location doesn't get near the amount of snow that you do. However, a few things come to mind. First, the ground mounted, and if possible passive tracking system, may be a first choice except there are a couple of drawbacks. As I'm sure you are aware, you need a fairly large clear area to keep them in sunlight and that may not be possible if you have tall pines in abundance. Also, theft is easier with a ground mounted system.
I've written an article for the Kerr-Cole Center for Sustainable Living that shows how to calculate the appropriate mounting angle for the collectors to fine-tune when you want maximum solar insolation in relation to latitude and roof pitch. There are several other factors that the article mentions when planning a system. Give me ([email protected]) your email address and I'll send it to you. It is a trade off on racking cost versus wind protection but with the formulas in the article you may be able to mount the panels at quite a steep angle which will make snow removal easier and still have excellent insolation value.
Another thought is that there are heat strips that are made for keeping ice out of gutters in the winter. I talked to the company and they are not all that expensive nor use a lot of electricity. With sufficient angle of the panels and the strip mounted at the bottom of each row of collectors you may be able to have the snow slide off easier.
Good luck.
 
The pine cones aren't going to be a problem. Solar modules use tempered glass and can withstand the impact. However they do need direct sunlight, and if you're that close to pine trees you might be getting too much shading. You might contact a local installer to get insolation measurements to see if it's feasible. The winds aren't going to be a problem either - mounting systems are typically rated for 120 mph winds. As for the snow - as long as it doesn't build up too deep, enough sunlight will be able to penetrate it to reach the solar panels which will heat up and melt the snow. If it does get too deep as might happen with a big storm, you can use a pole to scrape off the majority of the snow and the solar panels will melt the remainder. The solar panels should be tilted south at about 40 degrees or so for maximum sun exposure, and this will also help the snow slide off. With the amount of wind you get, though, a small wind system might make a lot of sense. Check out the Skystream - a small wind turbine with built-in net-metering inverter - you can connect it directly to your house wiring and be running your meter backwards just like that, plug-and-play: http://www.skystreamenergy.com/ You might even go with a hybrid system including wind and solar.
 
Trees make wind inefficient to use, since the flow is all choppy after coming through the trees. It's hard for a turbine to extract energy from turbulent flows. Not impossible, of course - some styles might still to pretty well. The "fan" type ones will not work that great with lots of obstructions.

If you want solar, maybe a thin film system is a viable option. Thin film solar has about half the efficiency, but will performs better that crystalline panels in partial shade/light snow covering. Even works a bit on overcast days, and I've heard claims that even a strong moonlight can give some output. You'd need to research mounting options, though, since all the thin film modules I know of are designed to adhere to flat/membrane roofs. And of course you'll need more area to get the same output compared to crystalline.
=Smidge=
 
Johnr wrote:
Check out the Skystream - a small wind turbine with built-in net-metering inverter - you can connect it directly to your house wiring and be running your meter backwards just like that, plug-and-play: http://www.skystreamenergy.com/
I'd be very careful about any "plug-and-play" set up plugged into house wiring and hence the grid. Although all inverters are required to shut down when they cannot sense power from the grid, there are several lockouts involved to meet code. These guarantee that the utility can physically lock out your system to protect a lineman from getting electrocuted from back-feed current.
 
Carlos said:
EVDRIVER said:
Call a professional and get and estimate and recommendation. This is the easiest way to get accurate answers.

You mean like calling my local Nissan dealer and asking questions about this new Nissan LEAF EV?

Ya that worked well, in the beginning the first dealer told me they wouldnt be available until 2012. Second one said they arent planning to sell or support the LEAF because they do not think they will make any money off the dealer markup.
Third one said, the LEAF? What's that........ :shock:

I think their are more informed people on this forum than all the commissioned based sales experts out in the field.
Get some good ideas, do your own research and then approach the experts with your questions.

just my two cents



Not sure how you compare a car sales person to a trained installer. Installers usually have experience in the design of systems and knowledge of the area. Mine did full CAD drawings, and full 20 page analysis on every aspect and placement option, etc, etc. The processed all my paperwork for rebates and I even received a large additional city rebate as they were part of a city workforce project (only a few were). That is the role of a professional solar installer and why one gets several bids. Car dealers sell many products and the objective is to get the product sold as fast as possible.

Hiring a competent professional helps take the guesswork out and give options one may not have considered. I see people that get advice and "know" what they want on projects and end up making decisions based on advice of non-professionals. In my business we don't fix these issues we start from the beginning and do it right.


WInd is not a good option in most cases as you need very high, constant laminar flow unless you go with less efficient VAWT devices which are expensive. It is extremely windy where I live almost all year as I live at the top of a mountain and it's blowing 20mph now but wind is not a good option. Another situation where a trained professional can help.
 
ERG4ALL said:
I'd be very careful about any "plug-and-play" set up plugged into house wiring and hence the grid. Although all inverters are required to shut down when they cannot sense power from the grid, there are several lockouts involved to meet code. These guarantee that the utility can physically lock out your system to protect a lineman from getting electrocuted from back-feed current.
Surprisingly, the physical AC disconnect requirements depends on your local jurisdiction and utility co - typically the utility.

The biggest utility in CA no longer requires an AC disconnect for PV installs, anyway. They trust that the inverters will shut down when the grid goes down as all inverters have been certified to do. I wish more utilities would get on board - it would save a couple hundred bucks off each PV install for a feature that never gets used. The utility can always pull the meter if they really want to make sure a house can't power the grid.

In my system I have 4 different AC OCD devices in line with my PV system plus the physical disconnect. Goes something like this:

18 PV panels -> 18 Micro-inverters -> 2 15A breakers -> subpanel -> 30A rated AC disconnect -> 20A breaker in main panel -> 100A main panel -> meter -> utility.
 
LakeLeaf said:
The second major issue I have to overcome is that I'd likely have to tilt my solar panels off the roof to get the right angle. We sometimes have 50-70+MPH winds here, so the installation would have to be able to withstand some pretty strong winds. Any suggestions on this?
Yes, you would need a sturdy mounting system, but wouldn't tilt+wind combine to minimize snow accumulation on the panels?
 
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