DIY insolation meter (almost)

Piwoslaw · 09-27-15, 10:34 AM

Poland's government has finally matured (or was forced by the European Union) to introducing renewable energy incentives which actually work - in the last year I've noticed a lot of new PV systems on private houses. We've wanted solar too, but always thought we have too much shade from the tall trees around our house. Now I want to confirm this.

I'd like to check exactly how long the roof of our house gets direct sunlight during the day, at different times of the year. Yes, there are complicated and/or expensive gizmos which will do the job, but can I do it low tech? I'm not really interested in quantifying how many watts of energy hit the roof, minute by minute, a yes/no is enough.

My idea is to make a primitive insolation sensor - 2 photo- or thermoresistors on the north and south sides of a "wall". When in the shade, both sensors give the same value, when in the sun, the sensor on the southern side of the "wall" will show more light/heat than the one on the shady north side. In fact, I there would be 5 "south" sensors (1 on each corner of the roof plus 1 in the middle), while the "north" need only be one (could be anywhere, as long as it is always shaded). There could also be a "control" sensor in a spot which always gets sunlight (when available), then comparing each "south" sensor to the "north" and "control" will additionally tell if there is partial shading. Collecting data for 1 cloudless day once a month should be enough?

What do you think? Am I overdoing this? Yes, getting pictures of the roof during the day would also work...

09-27-15, 10:34 AM	#1
Piwoslaw Super Moderator Join Date: May 2009 Location: Warsaw, Poland Posts: 961 Thanks: 188 Thanked 110 Times in 86 Posts	DIY insolation meter (almost) Poland's government has finally matured (or was forced by the European Union) to introducing renewable energy incentives which actually work - in the last year I've noticed a lot of new PV systems on private houses. We've wanted solar too, but always thought we have too much shade from the tall trees around our house. Now I want to confirm this. I'd like to check exactly how long the roof of our house gets direct sunlight during the day, at different times of the year. Yes, there are complicated and/or expensive gizmos which will do the job, but can I do it low tech? I'm not really interested in quantifying how many watts of energy hit the roof, minute by minute, a yes/no is enough. My idea is to make a primitive insolation sensor - 2 photo- or thermoresistors on the north and south sides of a "wall". When in the shade, both sensors give the same value, when in the sun, the sensor on the southern side of the "wall" will show more light/heat than the one on the shady north side. In fact, I there would be 5 "south" sensors (1 on each corner of the roof plus 1 in the middle), while the "north" need only be one (could be anywhere, as long as it is always shaded). There could also be a "control" sensor in a spot which always gets sunlight (when available), then comparing each "south" sensor to the "north" and "control" will additionally tell if there is partial shading. Collecting data for 1 cloudless day once a month should be enough? What do you think? Am I overdoing this? Yes, getting pictures of the roof during the day would also work... __________________ Ecorenovation - the bottomless piggy bank that tries to tame the energy hog.