Our solar installers, Mercury Solar, were on site this morning in preparation of next week's solar installation. Kind of dig their tee-shirts and we are very excited to see this actually coming together. Incorporating solar on our own building is thrilling, knowing we get to harness a small fraction of the sun's radiation, and do our small part in lowering fossil fuel consumption.
Our system comprises of 24 Sunpower SPR-230 panels on a rooftop canopy, providing approx. 5.52 to 5.75kW of power. The 230 stands for 230watts generated by each panel. Sunpower right now is operating at 18.5% efficiency on the panel (18.5percent of the light hitting the panel will be converted to usable energy), which may not sound like a lot, but given the industry average of about 12% these are actually at the top of the market. A little more pricey, but worth it. Panel efficiency is where solar is criticized and where innovation is being focused. There are reports of efficiencies reaching upwards of 35% in lab based environments, hopefully this will make it out to the real world.
So how much does 5.52kW actually produce? Well, just about 7,286 kWh per year, and according to our energy analysis (more on that later) each apartment will consume approx. 8,500 kWh annually. So our solar system is predicted to offset one residential unit by 85.7%. Yeah! Perhaps we can even watch the meter go backward and earn a few dollars.
Our system will be grid-tied, meaning that we are connected to the ConEdison electrical grid, so not off-the-grid, as many associate with solar systems. This is for a number of reasons. The first is that the batteries are fairly toxic, hard to recycle, require maintenance, take up room for storage, and in this situation un-necessary. Grid-tying means that the power we create gets fed into the city grid, and our meter flows backward giving us credit. In the hours we are consuming more than we are producing or in the evening hours the meter flows forward. At the end of the month the difference is billed. You can actually watch and monitor the meter and see what is happening on a daily basis. Fun! So rooftop systems, like ours, is basically a way to decentralize and localize power generation. The draw back is that when NYC has a brownout / blackout, we will be in the dark as well.
The image below is of a solar shade calculator. For both NYSERDA incentives and just general efficiency of the system, shade should be kept to a bear minimum. The sun-tracker, and shade mapper gives an idea of how buildings, chimneys, and objects may cast shadows on rooftop panels. Our building happens to be as tall as our neighbors with nearly no obstructions, so we are in good shape. Doing a solar canopy, lifting it off the roof plane really helps with this as well.
Check back next week, the solar installation is scheduled for November 16!
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