Solar snow melting systems

For shallow-pitch PV units, a wifi-controlled device with video camera monitor may be your last, ideal hope.

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Ice-Buster. When you"re stuck with shallow-pitched PV panels, de-icing cables coupled with smart plugs may be an option.

WITH THE SERVICES of Revision Energy, among the the majority of respected solar installers in Southern Maine, I adhered to the ridiculous sightline standards of Portland"s Historic Preservation Office, while installing my 7-kilowatt solar selection.

What I finished up with was solar panels on a flat roof pitched so low that they never melted their snow fill, leading to ice dams to form at the bottom of the panels, threatening to shatter them. I do not blame Revision. They did their best under the scenarios. It"s Historic"s heavy-handed nostalgic bologna that led to the trouble.

A Field Test Before Installation

It transforms out that no one I talked to might offer an affordable and effective PV de-icing solution, so I chose to develop my own, making use of roof de-icing cable. First, I picked up a 60-ft. self-included cable to attempt, and also last winter, I clipped it to the trailing edge of a couple of of my pv panels through tension clamps. Then, after poor icing or scurrently events, I ssuggest plugged the cable in to a heavy duty extension cord. The outcomes were surprisingly efficient. The 60-ft. cable cleared sufficient of the ice from the base of the panels to defend them from freeze-thaw damages, and also slightly accelerated the melting procedure overall.

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Reading up on exactly how these cables job-related, the majority of use about 5 watts per straight foot. So in concept, 60 ft. would certainly draw only about 300 watts. My system wasn’t yet finish, however I wanted to make sure a single circuit can manage the entire roof—about 160 ft. full of cable size, or a full of around 800 watts. That’s well listed below the 1800-watt max of a typical 15-amp circuit, through plenty of juice left over to charge my remote camera.

Full-On Melting


This fall, I purchased one more 100 ft. of deicing cable, and had a new 20-amp, ground fault-protected circuit in armored cable run to the roof, and inserted inside a jumbo all-weather plastic box. I experimented through means to connect the de-icing cable to the panels, and discovered that utilizing Gorilla tape readily available the simplest and leastern terrible solution. I attached the cable at 12-inch intervals to the trailing edge of each panel, flush with the surface to permit water circulation. I would certainly guess that the heating cable will have a lifeexpectancy of about 5 years at finest, and also have the right to be easily removed. For the remainder of the cable, I adhered to the organic contours of the panels and also their supports. As an outcome, the last de-icing cable is all but invisible. Each length of cable has its own grounded plug, which I left dangling close to the power junction.

For the junction box, I ordered a jumbo weatherproof cover. I know the roof takes a beating all year in Maine, and I wanted my distinct plugs well defended. Lowes didn’t bring them substantial enough, so I had to order it virtual.

A Phone-Ready Wifi Switch

Next, I purchased a Wemo Insight wireless outlet, in addition to a Wemo Mini from Belkin. Although designed for internal usage, I hope my huge weatherproof box will save it functioning. With a Wemo Insight, you have the right to not just regulate once an outlet turns off and on—you have the right to Monitor the power its making use of from a smartphone utilizing the cost-free Wemo App from Belkin. I tested the power draw from both ice-melting cables and also uncovered that they pull 926 watts, a little more than my estimate, but still well below the 1800-watt resistance rating of the Wemo mini plug. I switched over to that plug ssuggest bereason as soon as i had actually the power consumption data, i didn"t need that feature any even more.

To put both cables on one wemo, I plugged a simple 3-prong splitter into it, giving me two grounded outlets controlled by the Wemo—enough for both de-icing cables. I had one outlet left over, so I supplied it to plug in the usb charger for an Arlo wifi video camera, attached to the chimney that surveys the PV panels. This means, wherever before I am, I deserve to take a quick look at the roof and also revolve on the de-icing as soon as it’s needed.

Solar In—Ice Melting Out

You’re probably wondering, like I was, how a lot of my priceless solar credits will be consumed by this ice-melting requirement. Here’s an estimate. In a negative winter, we might have 7 or 8 snow/ice events that warrant some melting on the roof. Let’s say that in each situation, I leave the cables on for around 12 hours after the storm. That’s a total of about 96 hours (for 8 storms) at 926 watts. At 11 cents/kilowatt as the going rate for residential power, that’s about $10 worth of electrical energy per winter. My mechanism peaks at 6 kilowatts per hour, so put another method, it takes my roof around 12 hours of solar at optimal performance to make that much power.

Ultimately, I’m hoping my snow melting initiatives end up being quaint artifacts, prefer leaky single-pane windows. Perhaps the presence of solar panels on roofs in Portland’s densely occupied area will come to be a welcome authorize or eco-friendly duty. For a city that prides itself on progressive national politics, the reality that I have to hide my solar panels is ironic to the suggest of stupidity. Have you ever watched world walk dvery own a city street? The reality is, they never look up. And if they did happen to glance skyward, perhaps the glint of shimmering solar panel might inspire them to break their very own fossil fuel addictions. Let’s hope future Historic Preservation bureaucrats will be asking world why they have so few solar accessories, not what color they intend to spray paint a vent pipe.