Scrobby’s on Your Roof, Cleaning Your Solar Panels

Solar panels are a great, sustainable addition to your home’s energy scheme. They’re bound to get dirty, but they can’t withstand harsh chemicals and still be effective. While there are companies that will come out and clean your installation a few times a year, the service is a recurring cost that adds up quickly. With Scrobby, his entry into The Hackaday Prize, [Stefan] sought to build a highly affordable and sustainable solution that, after installation, requires no dangerous trips back up to the roof.

Scrobby is solar-powered and cleans using rainwater. The user can set and alter the cleaning schedule over Bluetooth from their phone. [Stefan]’s prototype was built around a Teensy 3.0, but he will ultimately use custom boards based on the Freescale KL26. In addition to the Bluetooth module, there are six ultrasonic sensors, rain and temperature sensors, and motor-driven spools for tethered movement.

Make the jump to see Scrobby get his prototype bristles installed and show off his abilities in [Stefan]’s demo video. To register for updates, check out Scrobby’s website. If you hurry, you can donate to Scrobby’s Kickstarter campaign. The question is, who will clean Scrobby’s solar panels?


SpaceWrencherThis project is an official entry to The Hackaday Prize that sadly didn’t make the quarterfinal selection. It’s still a great project, and worthy of a Hackaday post on its own.

33 thoughts on “Scrobby’s on Your Roof, Cleaning Your Solar Panels

  1. Personally, I think this is a brilliant product. Solar powered, only runs when it rains according to a schedule, learns your panel layout, has a base. It looks great, too – like a finished product.

    The main downside I see is the price – certainly low cost, but it could be much lower; after all, it has less smarts and parts than a Roomba.

    I wish this guy a lot of luck – if I had a panel setup, I’d buy one. Unless he gets a ton more backers in a short amount of time, he’s not going to make the KS. Which is unfortunate, because it’s a great product that deserves to see the light of day.

    Hopefully iRobot will throw the guy a bone, buy up the tech (or hire him), and add it to their product line; it would go perfectly with their current consumer product line.

    1. Thanks for the compliment! I only now saw the frontpage article myself, it’s amazing to see my product featured here.

      The KS might not have succeeded in financial sense (I had to set a pretty high goal because I didn’t want to end up in a situation I’d have to find a way to produce 10 or 20 units, which isn’t possible without taking a huge loss on each one), but it sure has succeeded in generating discussion about the product and market. It also has been a crash course in marketing and communication.
      Most of my funders are individuals. I’ve also been receiving a lot of corporate interest, but they haven’t been as eager to join in the funding stage.
      I’m still in talks about continuing the project with other ways of funding, because I do believe automated cleaning systems is where solar energy is heading in the western world.

    2. Looks like there is a working prototype, but no demonstration of a full cleaning cycle with docking.
      Also, there is no mention of wind in the campaign which is a significant issue with this device. There is a docking station, but anything that is not locked down can break free in winds; the docking station seems a bit inadequate. We currently have a tornado sweeping across the UK.

      I think the kickstarter is a bit short on detail for a robust end product for the money it’s asking. It would probably cost as much again to get it up on the roof, something I’ll not do myself; an issue that could cause the kickstarter to fail.

      A great product for sure, developed in the right hands, but at this stage of product development, it might be cheaper to have dirty solar panels for ten years (depending on your environment).

      A think partnership is needed with panel installers and a manufacturer to deliver the best value for money with this type of product.

    1. How do you “dock” to a water source successfully, 100% of the time? I could see that failing in a way that leaves you using hundreds of thousands of gallons of water.

      1. Gravity, more or less. A little bowl on top, that collects water from a spout above it. Scrobby could even have it’s top shaped like a rough, squarish funnel. This would mean that as the water trickled over Scrobby’s top surface, into it’s tank, it’d give it’s solar panels a rinse.

        You’re only talking about a litre or so, tops. Or Plan B would be to have separate sprayers that wet the roof panels when it’s time for a clean. Either way, you’d control the water flow yourself from a valve in the kitchen or wherever.

        I wouldn’t use shower water, you’re supposed to be making things cleaner after all. Dead skin and soap crusted on top wouldn’t help.

    2. I’ve considered adding a reservoir at one point, but it’s not as simple as it sounds for a product that remains outdoor for years. An open reservoir would make a great swamp over time. Therefore I’ve chosen to focus on the areas with enough rainfall (which were plenty, after studying the meteorology data on rain days across the globe).

  2. Anywhere there isn’t reliable, periodic rainfall that lasts long enough for this thing to complete the job, it won’t work there. It will need a pipe and distribution manifold for water.

    Another problem with doing the cleaning in the rain is available sunlight. The cleaner’s PV cells need sunlight, which is generally much lower in a rainstorm. Oops. Same problem as Solar Freaking Roadways with its PV cells constantly blocked by the cars driving over them.

    Cleaning the cleaner’s PV is easy. Put a garage somewhere with a squeegee and water squirt so that when not in use it gets parked and cleaned.

    The cleaning process could go much faster with a four cable system, which would also keep it from blowing around and possibly causing damage to itself or the panels in a wind gust.

      1. In Colorado apparently rainfall belongs to those who own water-rights in that state and denying rainfall from reaching it’s normal drainage denies them their water. Laws were loosened a bit in 2009 when they started permitting residential land owners with the right kind of wells to collect rainwater directly.

  3. Just remember to not leave Scrobby on any part of your solar panel for prolonged periods of time, or you can cause it to crack.

    Solar panels are internally series-connected because each junction only produces 0.7 volts. If any part of the series is shaded, it reverses polarity and starts to heat up due to current being forced through by the other cells. This reduces efficiency, lifetime, and can crack the panel due to overheating.

      1. A resting pad which I reassuringly notice seems to have the means to stop it blowing up and off the panels; but the idea of wind gusts still bother me. How does Scrobby decide that it is indeed safe to venture out in rain that may be accompanied by gusty winds? (I am commenting during a particularly sudden squally thunderstorm.) Is it reliant on infrequent scheduling to summer months and a dose of luck? For a fire and forget product, how will it stand up to freezing conditions of a harsh winter?

        I too could not help but to imagine a tiny Scrobby cleaning the Scrobby panels, and an even tinier Scrobby upon that and so on!

  4. I have solar panels on my roof and finally got up there and cleaned them by hand. I saw no difference in output at all. I guess the rain is enough to clean them, and the minute amount of dirt that remains is negligible on performance.

    Do others have a different experience?

    1. I think it has to do with with what’s in your rainwater/if it’s dusty. I suspect in some areas with lots of minerals/pollution, rainwater would be less than beneficial.

    2. I also have panels. I’ve cleaned them once in two years. The tree pollen had collected noticably so I hosed them off from the ground. There was a slight increase in output. This year the rain has kept them clean.

      I’ve thougt about automated cleaning solutions, but so far the need has not been great enough.

  5. If there is little rainfall, it seems like this might be an impractical way to get the job done – otherwise, it seems like a viable way to keep the solar panels clean. We just had our roof cleaned to get rid of some mold.

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