Solar Powered Shop
Here our fearless leader (Art, of course) proudly poses with the completed system.
Why invest in solar? We’re looking at the money spent on our solar system as an investment with returns in environmental protection, publicity, and if everything works out, a financial profit as well. Solar power will reduce our use of electricity created by burning fossil fuels, which will help with smog and global warming. This is cool, but not our only reason for wanting a solar electric system. Our customer’s reactions to our participation in the Bay Area Green Business Program, Berkeley’s consumer oil recycling program, and our own self initiated battery collection and recycling program has taught us that our customers care about the environment. Some of our customers have even told us the reason they started to bring their cars in was our participation in Green Business Program. Being good to the earth is a lot cheaper than a yellow page ad, and makes us feel good too. We’ve been in the same spot for 25 years and plan to be here for 25 more. Over the long term, provided the solar panels last as long as they were designed to, we should actually turn a profit on the system, especially if electricity prices rise. So to recap: good for the earth, good for our business, good for our wallets. Why solar? Why not!
Here’s some information about our system. I thought the technical information was neat. Electrical theory is the same whether it’s on our roof or under the hood. If you don’t find it as interesting as I do, you can scroll past this section to see step by step photos of the installation.
The system consists of 90 solar panels, each one with a theoretical maximum output of 167 watts (appox. 33.5 volts x approx. 5 amps). The theoretical maximum will never be reached while on our roof, it’s only a figure used in lab testing with very bright lights. There are 5 “strings” of panels wired in series on our roof: one string of 16 panels, two strings of 18 panels, and two strings of 19 panels. Each string is wired in series so the voltages are added together and the amperage stays the same. For example, on the 16 panel string, the total voltage would be 16 x 33.5 volt = 536 volts. The total wattage would be 536 volts x 5 amps = 2680 watts. So here are the specs for each strings:
String 1: 16 x 33.5V = 536V x 5A = 2680W
String 2: 18 x 33.5V = 603V x 5A = 3015W
String 3: 18 x 33.5V = 603V x 5A = 3015W
String 4: 19 x 33.5V = 636V x 5A = 3180W
String 5: 19 x 33.5V = 636V x 5A = 3180W
Total watts: 2680W + 3015W + 3015W + 3180W + 3180W = 15,070 watts or 15KW
or the quicker calculation 167W x 90 = 15,030 watts (Yeah, I know there’s a 40 watt difference. I did say “approx.”)
However, Sunlight and power bills this as a 12KW system. Probably based on more realistic optimal performance figures rather than the theoretical maximum.
Each string of panels is wired into an inverter that converts the DC (direct current) generated by the panels to AC (alternating current) which is what is used for household electricity. Each inverter is rated for 2500 watts, and you may have noticed that each string’s theoretical wattage is higher than 2500 watts. Blake explains this is OK because the inverters rating is in real capacity, whereas the panel’s rating is in theoretical capability. If you add the inverter capacities (2500W x 5), you come up with 12,500 watts, which more closely matches our system’s rating of 12 KW. The voltage input to the inverters from the panels is on average about 600 volts. This is way more than can be used by household items like computers and lights, which normally run on 120 volts. It’s even more than is used by heavy duty electrical items like welders and parts washers, which normally run on 240 volts. So in addition to converting DC to AC, the inverters also transform the around 600 volts / 5 amps to around 240 volts / 12.5 amps. In doing this, there is a little power loss at the inverter. Our inverters are 94% efficient, meaning 3000 watts will drop to about 2820 watts (240 volts x 11.75 amps). Our maximum system wattage of 12,500 watts drops to 11,750 harvestable watts.
PG&E will credit your bill for power generated, but will not issue a check for power generated over your needs. It makes sense, therefore, to carefully plan a system to meet the power requirements of your home or business, but not exceed it. If you install to large a system, you’ll be giving away free power to PG&E, who will no doubt use it to give their top executives a fat bonus before filing for bankruptcy and being bailed out by the taxpayers, again. If you install too small of a system, you will still have to pay for some of your electricity. This is why using an experienced local solar contractor is important. They know how their systems will perform in the real world based on past installations. Sunlight and Power first checked a full year of PG&E bills to determine our power consumption, then designed a system to match.
Here’s our start to finish photolog.
Before installing the solar system, we had to correct one of the buildings electrical oddities. Our building had two power meters. One on the newer and more robust San Pablo underground line, and the other on the older and more trouble prone Russel above ground line. We were advised that the solar system should be tied into only one meter, so we had a contractor come out and tie all of our buildings into the meter on San Pablo side.
The first step in installing a solar electric system is a consultation with the company who will be designing and installing the system. We’re working with Sun Light & Power . They’ve checked past electrical usage and talked to us about our goals for the system. The next step is the site survey, where they check the amount of space available for solar panels, check existing wiring, and determine the best way to install the system.
Here’s a picture of Blake and Charlie from Sun Light & Power, tape measure at the ready. They’ve come to do the site survey.
Here are Blake and Charlie from Sun Light & Power on the roof with Art. Charlie is taking pictures of the site to aid in planning while Blake talks to Art about different panel mounting options. “I’m not ready to install the new rigid awnings I was telling you about earlier. You won’t be able to stand on these.”, says Art. “No problem, we can mount the solar panels from up here”, says Blake.
Next Daniel and Pete came out to start building the mounting system for the solar panels.
They install mounting posts for the solar panels in the roof, running along the rafters. Art’s Automotive has grown bit by bit over the years and working space has been added as it was needed. The three buildings that stand on our main lot were all built at different times. The rafters run in different directions on the two building where the solar panels are, so the chalk lines and posts run in different directions as well.
The roofers came out to check to make sure the roof was sound. As it turns out, it wasn’t. There were some leaks and some rot caused be the leaks. In addition a vent fan was improperly mounted. The roofers has the roof up to snuff in a couple of days. It’s a good thing it got fixed before the installation had gotten too far along.
The roofers also seal the mounting posts so the don’t leak where they are bolted into the roof.
As the roofers work to seal the mounts, the guys from Sunlight and Power install the inverters, which convert the DC (direct current) the solar panels generate into AC (alternating current), so the system can be connected to the power grid.
Next preparations are made to install a cutoff switch to automatically disengage the system in the event of a power outage. Without the cutout, when voltage on the grid went low, the solar equipment might be damaged by the high current flow. This means we will be in the dark just like everybody else in the event of a blackout. Solar systems can be designed “off grid” using batteries to store the electricity generated by the panels, but this option did not make sense for us, but might be good for people living in remote areas.
Now that the roof is repaired and sealed, Sun Light and Power starts to build the mounts.
Jack and Roger came out next to finish the installation of the panel mounts.
The mounts are complete. This picture shows a little over half of all the panel mounts. All we need now are the panels. Unfortunately, the panels are on back order, so we’ll have to wait. On the bright side, it’s winter, and the panels would not be working at their full potential; it’s less frustrating to not have the panels now than it would be in the middle of summer. Most of the mounting system is made of aluminum, which is more expensive that steel, but I suppose the addition of weight to a structure not originally designed to support it should be minimize. All of the mounts are grounded together and to the panel frames with braided wire reduce the danger of electrocution should a short occur in one of the panels or in the wiring.
After a few weeks, Sun Light and Power comes out to double check their work. The panels scheduled to arrive the next day and they want to make sure everything is ready. When the panels come in the next morning, they fly up. I took this picture while the crew was taking their lunch.
The underside of the panels are surprisingly clean. Not a lot of jumbled wiring or electrical doodads.
By the end of the day most of the roof is covered with panels.
The final panels are in place and the system is almost ready for testing.
The system is tested and it works. We get a little break in the clouds and our electric meter starts to spin backwards!
Here’s the completed system. Luckily, we don’t get a lot of hail in California. The panels have a 25 year warranty and should pay for themselves in fewer than 10. If all goes well, we should have 15 years of free juice.