Friday, November 21, 2014

Snow on Solar Panels in Toronto

3 in 12 roof (14.0deg)
8 in 12 roof (33.7 deg)
It snowed two days ago - We got the normal 2" of snow while Buffalo got the 50"! (1.5m of snow, in 24hr).
A neighbor recently installed solar on their roof, and there is a bit of snow covering the panels.  The two photos below are to indicate the tenacity of snow cover over the panels.  Their roof slope is 3 in 12 (14.0deg from horizontal).  Ours is at 8in12 (33.7 deg).  As I mentioned, the snow arrived two days ago on a cloudy day.  Temperatures yesterday were below freezing all day, with night time temperatures about -9 deg C and daytime about -3 peak.  Some sun yesterday.  Last night was similar, and the sun came out earlier today so at 10am (when both these photos were taken) it has risen to about -3 C already, and sunny.  You can see the roof angle makes a significant difference.  On the steeper roof, the snow was actively shedding and within about 1/2hr after the photo was taken, pretty much all the snow had slipped off the panels.  It is great when snow slides of panels - it has a cleaning effect due to the slight rubbing.  I'll be monitoring the snow over the next few hours and days and months and updating this posting.  There are is a lot of knowledge and data out there on how much sun solar panels receive based on their angle and local climate, but less information on how the panels shed snow or dust, which appears to be a bit more complex and difficult to figure out (due to a lack of experience).  One thing I can suggest for low-slope panel installations: frameless panels such as these from Lumos (photo from
 - these will probably shed the snow a little more easily, I suspect - but no real data, as far as I can tell.  But I would want this kind, just for the improved appearance.  A number of manufacturers offer them.

Sunday, November 2, 2014

High Efficiency and LED Lighting for Passive Houses, Again

News:  Cree recently announced another breakthrough in LED technology:  a commercially available LED with a new level of efficacy:  200Lm/W  !  This is only a chip at the moment, but it is available for purchase - and this is of great interest to makers of flashlights, at the very least. For actual luminaires, they offer a troffer, 2' x 2' for commercial applications performing at 150 Lm/W, not necessarily with the same chips - I don't know.  Pretty awesome performance, and I think people are already aware of their other items I've mentioned in the past  - I have no affiliation with them, but their news seems to reach me easily.  Here is the troffer (it has a CRI of over 90):

The complexity of switching to LED lighting keeps surprising me.  At first I began to learn about the three main specs:

  1. Efficacy (Lumens per watt)
  2. CCT - Correlated Colour Temperature
  3. CRI - Colour Rendering Index
Armed with just these 3, one goes shopping for energy efficient LED replacements or integrated fixtures. Very quickly, we find ourselves surprised at the field of offerings. The first surprise is that all the major manufacturer's offerings are low-efficacy, offering usually not more than 60 Lm/W. I scoffed at this, in error. The next thing you run into is that there are often no claims of efficacy on some products, and then frequently, there is no certification label. Never mind the CRI - which hardly ever appeared. Then, we were in Costco the other day and found this:

The Luminus product. It lists all three main specs, and carries all the certs, and the purchase price (it was a sale) was $5 ea! Pretty impressive to find a product with this level of efficacy, at this colour, with a CRI of over 85, and at a $5 price.

Yet, looking around we find highly acclaimed products like this one from Soraa:
Which uses a different LED technology - GaN - I assume this means gallium nitride. At 54 Lm/W for the 3000K MR16 bulb, one is not impressed by the efficacy. But look at the CRI - 95% - a figure you just can't find in the common PC (phospor coated?) LED technology.

And then I discovered LED Benchmark ( These are the same guys doing benchmark testing of things like video cards and hard drives. I highly recommend their website, where you can expand your knowledge of LED lighting beyond the three main specs. They also have comparison with halogens. It was there I found that we can go beyond to also look at:
  • Flicker
  • actual performance
...and we find that many of the lesser-known product offerings (the cheap ones generally) frequently do not live up to their claims of efficacy, colour rendering, or even colour temperature. And all those low - efficacy major brands? Often they have sacrificed efficacy for colour rendering and reduced flicker. Having purchased a number of LED products now, I can confirm that flicker and CRI are important measures of light quality and should be given significance in the purchase decision. I am now, unlike before, willing to compromise on efficacy to get a light that has no flicker, and a high colour rendering index.

The photo above shows an LED chip I bought on Ebay.  It claims a 1000 Lumen output.  Using my lab power supply, I found it consumes only about 4W, so I highly doubt the claimed output.  The colour is warm white, as claimed, but the light quality was terrible - I'm not sure why, but probably CRI is low, and flicker high.

The photo above shows an LED chip I bought on Ebay. It claims a 1000 Lumen output. Using my lab power supply, I found it consumes only about 4W so I doubt the output is more than 500 Lumens. The colour is warm white, as claimed, but the light quality is terrible - I'm not sure why, but probably CRI is low, and flicker high.

The following 5 photos show commercial lighting quality hardware. We were very lucky to come across a batch of these on Kijiji and bought about 60 trimless recessed light fixtures (two types shown below - these are RSA brand by Cooper). These are about $200/fixture plus about $65 per trim ring. Costly when you consider a house can easily have 100 recesssed lights. We got them for about $6 ea, so we are installing these - they are low voltage (12V), with a solid -state voltage converter per the photo.

 I was interested to know the quality of the output waveform on these, wondering how the LED lamps would respond. But the output frquency is about 40kHz. A little high for my old oscilloscope to read well.

These are the fixed trims for the RSA trimless pot lights.  There are adjustable ones, and square ones for the square version of these lights also. This is a used one, of which I have only the one.

These are the trimless lights. They come with mounting bars and also butterfly clips, but I just didn't like the flimsy-ness of the mounting, so using wood rails - I got 50 of the white square ones below. An interesting feature is that since these are all trimless, they are mudded right into the ceiling drywall. This means no removing and replacing the fixture - but there is a facility to service them - the fixtures are designed so you can reach inside the opening and remove steel covers to service the wiring and the voltage converter as well.