Computing stuff tied to the physical world

Going solar – almost there!

In Hardware on Oct 15, 2012 at 00:01

It’s been over two years ago since I started looking for ways to collect solar energy on the roof, here at JeeLabs.

And then reality set in… the roofs of the houses in this street are covered with shingles from the late 70’s, and as we found out they contain asbestosyuck! Then, earlier this year, we were told that nothing could be done on the roof unless those shingles were first officially removed by a specially-equipped third party:

Image 5

So now at last, those “bad” shingles have been replaced and panels have been mounted:

DSC 4177

That little bulge is a “Solar tube” which brings extra sunlight into the stairway.

That’s 2 x 5 panels on this side, and 3 x 4 on the other roof:

DSC 4183

(the 10 panels you saw in the first picture are mounted on the roof to the far left)

For a total of 22 x 240 = 5280 Wattpeak. Not that they will ever all generate full power at the same time, because these two roofs are facing west and east, respectively. But hey, together they should still give us more than our annual 3100 kWh consumption. JeeLabs is about to become a net electricity producer!

Just one more step: wait for the SMA 5000 inverter to arrive and get it hooked up…

  1. Very cool! I was wondering: Since they’re mounted on quite different directions, did you do anything to prevent the shading effect?

    • Yes – the panels are connected as 4 separate “strings”. That way, weaker units don’t interfere with the units which are getting more sunlight and producing more power.

  2. Do you plan to monitor the power level directly from the inverter? Once per second it should emit a stream of serial data over bluetooth, the protocol is proprietary but it was partially reverse engineered and there’s even some arduino code out there:

    I got one of those cheap bluetooth serial module for the purpose, but for now it is sitting in a drawer because it needs a firmware reflash:

  3. Super! From where these panels were purchased?

  4. bravo!

  5. Very cool!

    Asbestos is a pain. Fine if you leave it alone, but dangerous if disturbed.

    It will be interesting to see how they perform because the satellite dish says your roof of far from the ideal orientation. BTW, who’s watching 3 different satellites?

  6. How do you manage to use just 3100 kWh/year? My house of three people is just 100 sq. m, all of my heat-producing appliances are natural gas or wood-fired, my refrigerator and freezer are modern and efficient, and most of my lights are fluorescent. Yet we still burn 7500 kWh/yr. Maybe I’ll have to deploy some Jeenodes around the house to help me do an energy use inventory. :-)

  7. Fascinatingly, wikipedia’s list of electricity consumption by nation ( ), shows us (Canada) burning 1795 watts per capita, and the Netherlands consuming just 767 watts. This is very similar to the 7500/3100 kWh ratio I note above. Interesting.

  8. Paul, maybe it is bacause you have real winters over there ;-)

    jcw, you will be a net energy producer, but the problem is that you want the juice at a different time than when it is produced. That is where the good old coal-fuelled generators come in handy. so, let’s find a good way to store this energy now.

  9. Paul: We live in Finland (real winters here too) in 116 m² with similar devices (non-electric heating as well), and consume currently 3200 kWh/year. Interestingly, Wikipedia indicates that Canada and Finland have similar per-capita electricity consumptions…

    Are you sure your neighbors are not tapping into your house? :)

  10. Did you already alter the meter sketch to keep track of negative pulses? Must be fun to see the daily kwh delivered to the powergrid. Electricity consumption here is 2950 kwh and natural gas consumption 1295 M3.

    • Not yet – planned, of course.

      Gas is a different story here, alas – the house is wide open, we need 2200 m3/yr to keep it comfy. That’s just heating and showers for two (cooking is electric, so is hot water in the kitchen). I’m looking into better isolation, but it’ll be tough to improve things substantially.

  11. Ah, well that’s where we make it up. In the last 12 months here we burned 1800 m^3 of gas for virtually all the heat, hot water, cooking and clothes drying. This is a relatively (for Canada) poorly-insulated 80 year-old house.

    Paradoxically, if we reduce our electricity consumption here we’ll be increasing our net carbon dioxide emissions, as the waste heat from the nuclear-derived electricity we use reduces the gas we burn for bulk heating.

  12. JCW, tisk tisk, mounting them on opposite sides of the roof. Solar panels are expensive, linear actuators are cheap. What you really want is to mount one of the sets of panels on a hinged mount. Then use the linear actuator to tilt the panels to face the sun. (could be done with both sets – one would be down and one would be up) The control algorythm can be something as simple as once an hour slowly run the actuator out a few times and in recording the solar voltage the whole time – then adjust the panel position to where the voltage was the highest, or as complex as going to the NASA website and trying to figure out the calculations fo where the sun will be, using time and date to adjust the panels.

    Something to consider instead of adding new panels – just fab up some mounts that allow the panels to be tilted, get a linear actuator (or better yet, a linear servo), fab up a plug/shield for a microcontroller and profit.

    Also may I reccomend the phillips AmbientLED LED light bulbs? Its the only LED bulb that I have tried that makes no compromises, and no excuses.

    Anywho – good job on saving the earth.

    • Hinged mounts would be the ultimate geek solution, however the Dutch building code doesn’t allow it (of course :-(). Roof mounted solar panels must be mounted in the same plane as the roof surface.

      A solar tracker in the garden would be allowed as far as I know, but that may have some WAF issues…

  13. i am very close to you (20 km to the north-east), jcw, take a look at my production (14x 250 wp, 2 string, sunnyboy): the monitoring is done with a raspi and usb-bt dongle using mrtg and this project:

  14. Isn’t it true anymore, that the cost of such a panel is more than the cost of electricity it generates during its whole lifespan?

    The second problem is, that AFAIK the primary energy consumed during the manufacturing of a solar panel is more, that the electrical energy it gains during its lifespan.

  15. There is interesting Web site ( ) comparing performance of 27 different solar systems. All systems are installed in Alice Springs (centre of Australia in desert). It is interesting to see that even in this environment most systems struggle to achieve rated peak performance. To some degree it will be affected by higher temperatures in this location (which you can display). One installation (#16), compares east, north, west and flat installation.

Comments are closed.