Is Solar Right For You? Find Out!

Solar panels are revolutionizing the electric power industry, but not everyone is a good candidate for rooftop solar. Obviously people in extreme northern or sothern latitudes aren’t going to be making a ton of energy during the winter compared to people living closer to the equator, for example, but there are other factors at play that are more specific to each individual house. To find out if any one in particular will benefit from solar panels, [Jake] and [Ryan]’s solar intensity sensor will help you find out.

The long-term intensity tracker is equipped with a small solar panel and a data recording device, properly contained in a waterproof enclosure, and is intended to be placed in the exact location that a potential solar installation will be. Once it has finished gathering data, it will help determine if it makes economical sense to install panels given that the roof slope might not be ideal, landscaping may be in the way, or you live in a climate where it rains a lot in the summer during peak production times.

As we move into the future of cheap, reliable solar panels, projects like this will become more and more valuable. If you’re not convinced yet that photovoltaics are the way of the future, though, there are other ways of harnessing that free solar power.

22 thoughts on “Is Solar Right For You? Find Out!

  1. Funny I thought about this recently myself. I already had a bunch of Arduino Nanos and just bought some cheap tiny solar panels. I was going to put them in the various location the person that gave me a quote, some I suspect may not be worth placing at that location. would love to collect via WiFi but only have a few Sparks to play with. with this setup I could decide what locations are best. Of course this could change as the seasons change.

  2. The whole thing about solar panels not being economical in the extreme north or south isn’t quite true.

    A huge factor is that solar panels often are limited by the temperature, as they get hotter their output sinks. During summer, the daytime is longer the closer you get to the poles as well.

    I live at 78°N and it turns out that solar panels work darn good and harvest a lot more energy than anticipated. Here it makes sense to put them on walls however. Almost 24h sunshine, snow reflection while there is both snow and light and finally the low temperatures do wonders.

    Of course they are no good the months where there is no light at all. But the time with at least a tiny bit of light is longer than the absolute polar night.

    1. The thing is that solar panels up north produce most power when the least power is needed, especially with the spring melt bringing abundant hydroelectric power, so they’re 180 degrees offset from being useful.

      With near 24 hour sunlight, you don’t need lights, you don’t need heaters, yet it’s not hot enough to need AC… about the only thing you do need it for is the TV and computer, and the kettle.

      1. It is true that the electrical needs here for households are lowest in the summer.

        Nonetheless in mainland Norway there is a power grid that allows to send the electricity down to other European countries.
        The hydropowerplants can store some water over time but there has been several summers already where it was so dry that the hydropower couldn’t keep up with the demand for hydropower.

        Here we have a coal power plant on a island power grid, so solar is a good power source.

    2. Not as far up North as you are (52 N) but I can confirm that solar is more efficient that I was told it would be. The expected amount per year was 2000 kWh, but every year it actually was 2600+ kWh.

      Also I ignored the advice of the “specialist” to remove one panel because of shade during part of the day. As all panels are in serial they said the shaded panel would reduce output to almost zero. It doesn’t, I see a significant drop in voltage but the inverter manages an increase in current, Power drops of course, but not all that much.

      1. That works, but mind that the current is still pushed through the shaded cell which causes internal heating and can damage the cell. When the sun isn’t moving the charges around inside the cell, it works like a large resistor and the current going through the series is heating the shaded cell a lot. It can even lead to cracking the glass from the heat.

        There’s a way around that using bypass diodes, which carry the current around the shaded cell. You lose the diode voltage, but you avoid baking the shaded cell.

        1. The worst case is when only part of the panel is shaded, because the panel is internally a bunch of series-connected cells as well. Then you get a small area of high resistance inside the panel, which gets heated by all the current going through the entire array. If the power draw increases, the panel develops a hot spot which ages the PN junction rapidly if it doesn’t burn open.

          Here’s how to do blocking and bypassing diodes in a solar array.

  3. This is a math problem involving the position of the sun over the 12 months of the year. It can definitely be done with an arduino… same exact math as you would do it on paper by hand, once, and write down the results for each month. I love the idea of doing it with some code in an arduino… but it would be a lot less work to do it once by hand and keep a sheet for each month, or each week, as you choose. Of course, you would have to learn to use a compass as well for either method.

    It will work with an arduino, and do so admirably. If doing it for just yourself at your location, just using paper would be a lot easier. I DO like seeing projects like this done with some processing power… Hacking is great stuff! I advocate such exercises, but if you’re just doing it once for your own solar install it’s less effort to just use paper and pencil.

    1. Sure, if weather, particulate scattering, shade from trees and buildings, etc are all ignored, it is simply a math problem. In reality, it is more complicated to determine how much solar power will actually be available in a given location. I have compared our measurements to those expected using that math, particularly using the PVLIB in Python. The clear sky measurements are quite close, but that’s not the whole picture.

      Another note is the project is also to teach those who are not Hackaday folks and may be less technical about some of these details about solar systems. Many are very surprised to hear about efficiency loss and high temperature and that power drop under clouds is so huge. For that, seeing is often believing, more than math every could show.

  4. Mind that using a solar panel for measuring solar intensity is not directly comparable, because solar panels suffer from the same “viewing angle” effect as cheap LCD monitors. There’s internal shadowing, and the angle of the light striking the silicon affects how the charges separate, so you’ll get different results depending on how the panel is oriented.

    If you want to simulate how a solar panel would operate in that location, in that orientation, that’s fine – but you do have to check that the panel is turned the same way. If you have it rotated 45 degrees off, then the angle effect will be very different and the results will be off.

    1. Yes, that is a very good point, but the project’s goal is for determining the available power from a PV installation, moreso than a scientific instrument to determine solar intensity, so ideally those details are actually an advantage. Of course you are correct in that the orientation and solar cell type must be the same for that to be true.

  5. Here at 45 north, a friend installed PV panels this spring. He has a one story in a U footprint. He has fixed panels on the east facing slope, west facing slope and south facing slope. That was modelled by the PV seller/installer using PV software that handles all of the year-round calculations of sun azimuth & elevation, etc.. Installed, it’s producing somewhat more than than the software predicted, likely due to using conservative values.

    No batteries, it supplies the grid. This first summer, it earned more than he paid for the electricity from the grid. Which is quite the acheivement, as in the prior year he’s dumped the propane furnace, stove and hot water and ICE car for Air Sourced Heat Pump, electric stove, HPWT and a EV Chev Volt and the higher voltage home charging. Prior to the PV, his monthly electric bill had jumped from what is had been, but that total bill, with all the prior electrical charges (including three teenagers) plus all of the new loads, came in less than his old monthly gas bill for his ICE commuter car. His PV is well on track to paying for itself in less time than its end of life.

    1. Return on investment at less than the finance rate, is it greedy to expect more than that?

      I’m assuming the price he paid includes no subsides, because that’s cheating the figures somewhat

  6. Full disclosure: I don’t own any panel > 10W
    In northern climate actually are some upside:
    -colder temperature means improved efficiency, better heat dissipation.
    -snow will scatter / reflect light quite a lot.

    removing snow from them must be a pain though. Not worst than car I suppose.

      1. unless the panel are not high up above the surface of whatever you put them on, and show piles up from below….

        roofs are usually designed to keep the snow on them and melt it, and not dump it straight down, because even surface friction manages to gather enough snow, that a clump of it falling down on a person might significantly injure them.

        unless you do what we did as kids, and toss firecrackers on the roof for controlled avalanches.

        my point is it’s not a factor one can nonchalantly dismiss under any circumstance.

  7. Interesting hands on approach …

    But there are lots and lots of reliable simulation software, used by Solar Panels installers that provide all that info, including tilt and orientation.

    Unfortunately as government incentives pay for a big part of the investment, orientation and tilt is ignored and more panels installed instead.
    We were invited to install our panels “flat” as the decrease in performance (versus tilted) will be less than 10% and cost (and used roof area) will be half. More panels instead, that produce more power for the same price and in the same roof area.

    And also, for the industry, panel-racks that do solar tracking are a four letter word … too expensive and complicated when half a dozen extra panels will do the same… (yes, they sell panels…)

  8. Hey there, latitude neighbour! I’m at 26S.

    Solar PV is generally best at an angle close to your latitude, i.e. my panels are at 26 degrees, which gives best overall performance during spring and autumn – they’re close to perpendicular at the equinoxes.

    My solar system was audited some years ago (a condition of getting subsidies), and the inspector was very friendly and forthcoming – showed me his data logger. He placed it on the centre of the panels on the roof, and it did its thing.

    1. Established location with a GPS receiver.
    2. Took a fish-eye photo of the sky – horizon-to-horizon – to establish obstructions such as trees.
    3. Entered some data – total solar capacity, etc

    Result? My place was 94% efficient! I lost a few points because of high trees on the western side, although it wasn’t as bad as I’d expected. He said it was a pretty good setup – lots of north-facing roof space, no obstruction until late in the afternoon, and so on

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