When I was installing solar panels on our house I couldn’t decide if there should be a gap between the rows. Leaving the gaps would make space for snow to pile up and cover the top row. With no gap the snow would slide off as one sheet. However, in the summer time having a gap would make the panels cooler with more space for hot air to escape. Since there is more sun in the summer time, I opted for a gap to keep the panels cooler.
Well I proved one thing, a gap does create snow dams.
I walked over to the Ypsi Food Coop and looked at their solar panels. Those panels don’t have a gap between the rows and you can see that snow on the top row has completely slid off.
However, they have another problem of not being high enough off the roof so the snow piles up at the bottom of the panels.
This is not a big deal since these panels are on a flat roof that is easily accessible and a volunteer checks on the panels to shovel the snow away from the bottom of the panels. If the panels were mounted higher, they would have a higher wind load and would need more weight to keep them ballasted to the roof.
Another project we’ve been working on is making QR tags and placing them on the buildings that have solar panels. People with a QR tag reader (usually a free app) can point their smart phone at the tag and it should bring up a 2 minute video about someone from that location explaining the solar installation at that location. This is very useful for places like the Ypsilanti Food Cooperative where the panels are on the roof and not visible from the front of the building. Here is a picture of the QR tag on the Ypsi Food Coop.
and on the River Street Bakery
Head over to the 312 River Street and point your phone at the wall, or if you’re lazy, just point your phone at the pictures on this blog posting.
Don’t have a smart phone? The videos are also available on the SolarYpsi website. Click on one of the locations and then click on the “files” tab to see a link to the video.
Thanks to Paul Haas for helping me make the tag at the Maker Works in Ann Arbor, to Nik Estep for writing the QR tag code for the SolarYpsi website, to Steve Pierce and HDL.com for hosting the SolarYpsi website, and to all the “actors” in the current and future videos.
As you saw a couple of postings ago, we lost real time monitoring at the Ypsi Food Coop and River Street Bakery when the power company swapped out our meters with the newer smart meters. I thought this would be a good time to review the energy production at our four real time monitoring sites. Here are some pictures from the last 12 months.
Recall that if you hover your mouse over the monthly energy charts on the different webpages, it will show you the value for each portion of the bar chart. Doing this for the four locations and adding up the values, the Ypsi Food Coop produced 2739.1 KWH for the past 12 months, City Hall made 3015.8 KWH, the Bakery made 6616.6 KWH, and Adams School made 1886.6 for the past 9 months. If we divide these values by the rated values of these systems we see that the Ypsi Food Coop is running (2739.1/3328.8) 82.3% efficient, City Hall is (3015.8/3591.6) 84.0% efficient, the Bakery is (6616.6/8760) 75.5% efficient, and Adams School is (1886.6/2630) 71.7% efficient. It is not surprising that City Hall is the best, because it is located four stories up and has no issues with shading. Both the Ypsi Food Coop and Bakery have afternoon shading with the Bakery getting the most. The Adams School numbers are for only a partial year, and I suspect once we get a full years worth of data it’s percentage will go up.
If we divide that generated power by the total power consumed, we see the portion of the Ypsi Food Coop that is solar power was 38% solar powered, City Hall is 2.7% solar powered, the Bakery was 30% solar powered, and Adams School was about 1% solar powered. You may be wondering why the Bakery was not 100% solar power as we designed the system. You’ll notice that the first two months the bakery was doing great, but then drops off. In August last year, the Ypsi Food Coop installed some new coolers that used 3-phase electricity, but the store did not have 3-phase power, so they wired them into the Bakery. This created a much larger demand for power and dropped it’s percent solar powered. In May of this year, the store finally got their own 3-phase power, and the coolers were moved back to this circuit. In May you can see that the bakery is back to being mostly solar powered. Hopefully the next 12 months will show the Bakery 100% powered.
I didn’t post the graphs for the apartments on Huron street. We are collating real time data for those three apartments, but using a different method, we’re pulling data for only the generation directly from the EnPhase inverter’s website. We have data for the monthly charts, but the numbers don’t look correct and I’ll have to work with Nik to understand what’s going on. Hopefully we can just correct the numbers that are there and calculate an efficiency later.