January 2012 will go down in the history books. Is this climate change? I feel as though I have moved to Boulder CO. Sometimes it's been cold, but mostly it's almost balmy. Last November, December, January heating degree days (base 65F) were 584, 978, 1,086, for a total of 2,646. This year the values are 429, 685, 823, for a total of 1,937, or 73% of last year's heating demand. I haven't once needed to wear my neoprene overbooties when riding a bike.
At the same time, January was extraordinarily sunny. The online estimating software called PV Watts estimates that my system, if completely unshaded, would make 330, 318, and 366 kWh in November, December, and January. The actual numbers, which include the effects of shading, have been 413, 303, and 468. December clearly has the most shading from trees to the south, and it's closest to the estimate. November and January have been 25 and 28% over the estimate. We at South Mountain think that Sunpower may be correct when they claim their panels outperform others watt for watt, but this also must be more sunshine.
In January, last year we used 418 kWh in the heat pump and this year it was 277. In fact, we only consumed 30 kWh more than the PVs generated. So it's scary but darn enjoyable.
Marc,
Greetings. Enjoy your blog, especially the quantitative reportage - very informative. I mounted a pyronometer(?) - an SMA Sunny Sensorbox unit - on my PV system, which uses an SMA inverter. It's useful for logging the insolation at the site for system diagnostics, design verification, and for doing direct comparisons with the PV Watts et al database for one's location. Now, to negotiate with my southerly neighbor about topping a couple of evergreens.......
Best,
Dodd
Posted by: Dodd Stacy | 02/04/2012 at 07:09 PM
Hi Dodd, thanks for your comment. What does SMA claim for the accuracy of the unit? Have you compared measured insolation on your system with predicted? Are there local insolation stations (Dartmouth?) to compare with?
Thanks!
Posted by: Marc Rosenbaum | 02/05/2012 at 08:15 AM
I have to confess to not yet making much quantitative use of the data for comparison purposes. I'm not yet able to find a claimed accuracy for the unit, nor have I looked into local monitoring stations. I'm using it so far to look at shading and cloudiness effects over the annual cycle. It's interesting to see cloud edge amplification!
My first order job is to deal with winter shading and snow accumulation. Otherwise I'm pleased with system overall performance and reliability. You can look over the top level data at:
http://www.sunnyportal.com/FixedPages/PlantProfile.aspx.
Best,
Dodd
Posted by: Dodd Stacy | 02/13/2012 at 06:13 PM
When you say "cloud edge amplification", do you mean increase in output from skies that have clouds but the beam radiation from the sun is unshaded? If so, that's when I've anecdotally noticed the highest output from my systems over the years - winter, clear beam radiation, white clouds in the sky.
Posted by: Marc Rosenbaum | 02/13/2012 at 09:52 PM
Low carbon is good for the community.
1. grow well: to grow vigorously and healthily
2. do well: to be successful and often profitable
Posted by: ryan | 05/13/2012 at 04:59 AM