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Snow Covered Solar Hot Water Collectors
At Mapawatt HQ, we often find ourselves reminding each other that we have to avoid “region-itis.” Since we are located in the southeast, it’s easy to focus on cooling, natural gas heated water and such without remembering that in other regions of the world, there are other energy concerns such as heating with fuel oil, wood pellets, gray-water systems and wind. Before I had a solar hot water system installed on my home, I researched the pro’s and con’s of solar before deciding on what type of system to install. Here is the list of issues I focused on when making the decision:
- Solar heating doesn’t work at night
- When it is cloudy, solar doesn’t work very well
- Solar doesn’t work when it’s raining
- Will pine needles from Georgia pine trees cover my collectors?
- What about haze and particulate in the air which is common in the Southeast. Will this affect my solar fraction?
When I walked outside this morning, I was reminded of another problem that we don’t encounter much in Georgia. Last night, it snowed 4 inches and covered our home and woods with a beautiful white blanket of snow. This is an occasion for great excitement in my home since it is seldom that we get even a snow flurry in Georgia.
Temperature of Snow Covered Solar Hot Water Collectors
As I felt the warmth of the bright sunshine, I looked up at my solar collectors and noticed the 2 inch blanket of snow completely covering them! Yes, the sun is shining, it’s below freezing and my solar hot water system is dormant. I checked my solar controller and the temperature on the collectors was 55*F. Both I and my family are thankful that I chose to install a pre-heat system that makes use of our electric hot water heater as a backup when the sun isn’t shining. (or the collectors are covered in snow!)
For many of you this may not be news but it is an important reminder. Make sure to account for snow cover as an additional issue when contemplating solar. Even solar hot water won’t work with the sun shining unless you are a brave soul and climb to the roof to sweep off the collectors. My house is three stories high so I’m not brave enough to risk having this being my last post on Mapawatt!
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I have the same problem with my solar PV system. We had over 1 foot of snow on Wednesday and the panels didn’t clear until late yesterday. It is very annoying sitting home on a sunny day and seeing my inverter output at 0.
PV is probably even more susceptible to obstruction. Did you notice if you had to get all of the snow off of all of the modules to get output? My understanding is that if just part of one panel is obstructed, it keeps the whole string from producing power.
Even with half the panels uncovered, output was extremely low, it wasn’t until almost all of the snow was off that production became decent. It is amazing how much the system relies on being completely unobstructed. I wonder if the the new optimizers would help in this case?
You might want to see some pictures I posted to my site recently of me using a snow rake on my panels. Go to the bottom of this page:
http://www.arttec.net/SolarPower/10_More/index.htm
There’s a big difference between solar electric panels and solar thermal collectors when it comes to shading. If you shade (cover with snow) only one cell on a solar electric panel it will compromise the power output considerably. Electricity flows through the cells in series – so it’s like pinching a garden hose. But partly shading (snow covering) a solar collector is not as bad. The part that is not shaded produces heat that warms the glass cover and melts the snow off pretty quickly.
Here in Maine hardware stores sell a tool called a “roof rake” that is like an angled plastic snow shovel on extension poles that can go out to 24 feet. You use this to haul the snow off the roof to reduce the weight on the roof – and to clear solar panels of course!
We have to deal with the snow a lot in the midwest this is precisely why we tilt the panels at a high angle when installing SHW panels.
Hi there from New Zealand, Great to get the Mapawatt daily blogs and follow the incentives to go green in your lovely country. The green movement and incentives here are a complete farce (only my opinion ) The Government grant toward home insulation is a prime example–so called qualified installers charge $60 per hr to install ceiling insulation and a hefty markup on the product and to get the grant one has to use these “approved” installers,whereby doing probably a better job yourself and with friends can get the same result for half the price, but no grant to help with some of the cost. I have installed a 30 evacuated tube system with a 340 litre holding tank and heat exchange copper coil and electric backup element for $2500.00 This is a total standalone solar water heater and we are now saving approx $50 –60 per month on our electric bill, so about a 2 year payback which is very good. This system is not of an “approved” type and I did the whole installation myself (except electric) so cannot get the Gov help again. I am currently waiting for the price of PV to come down to your levels (normal NZ retail is about $7 to $11 per watt) so far too expensive. Our utility price is 24c per unit at the moment so PV needs to come way down (maybe $2.00 watt)to be economic to install. I can but hope for that day soon — Keep up the good work on a wonderful informative site
Thanks for the feedback! Does the NZ government not give incentives for PV? How is most of the power generated there? Hydro?
Hi Chris, Yes the New Zealand gov does give incentives but only $1000-00 and again must be installed by “an approved” installer. Most of our power is generated by huge hydro dams and generators and also by steam in the thermal areas with two new stations being built at present.Natural gas powered sites are also being built as our oil fields come on line and huge wind farms are also being built to take advantage of our wild southerly winds –more of these would be great but our environmentalist minority groups seem to have a huge voice with concerns for visual and noise pollution?? Not all of our electricity supply companies will allow grid connect or mini hydro rebates either –a problem being addressed at the moment also.