May 2 , 2004
Do Solar Panels Sleep at Night?
(Okay, it's a pretty strange question to ask, but consider the source.)
After testing twelve of the twenty-four panels, I was amazed as to how much power the panels were producing even on a cloudy day. This led me to wonder if there were enough photons streaming around in the night sky to register on a volt meter. With the moon half full, I'm happy to report that two of the panels tied together in series were generating eight-hundredths of a volt. Not that you can do anything meaningful with eight-hundredths of a volt, but for this geek, it was interesting to know that the solar PV's actually do generate power (albeit very small) during the night.
I can now say that half of the panels are up. They're not connected to anything, but physically they are mounted to the rack. It wasn't too difficult to mount by them by myself, although a second person would have made things go a bit smoother.
I started on Tuesday morning by carrying twelve of the panels out to the rack and prepared to test their power output under a load. My plans were to try to match the panels in groups of three to get the best possible efficiency out of the array.
I checked the weather report, and it looked to be sunny until about noon. I started testing the panels at around 9 AM and immediately found that there was a fairly sizeable difference in the voltage between the first two panels. It appeared that the first panel was about a volt and a half lower than the second panel under the same load. The first panel had been sitting in the sun for at least 30 minutes, so it was rather warm. The second panel had been sitting in the shade. I watched the voltage on the second panel slowly drop. It kept dropping for quite some time. The reason why it was dropping was due to the temperature change in the panel. Photovoltaics are more efficient the cooler they are, and conversely less efficient the warmer they are. I watched the voltage drop for a good 15 minutes when I decided that I probably wasn't going to get all the panels tested if I had to wait this long for the panels to "warm up". Secondly, the sun's angle was also changing which would skew the numbers. Thirdly, condensation trails from high-altitude airplanes were covering part of the sky by now.
And to top things off, visitors arrived unexpectedly. Not that I don't mind visitors, but the timing wasn't very good. I explained to my guests that I only had a few hours worth of sunlight to test the panels, so I couldn't spend a lot of time with them. They were quite understanding and within 30 minutes, I was back to testing panels...well sort of.
It seemed that my visitors had inadvertently locked themselves out of their car. I really felt sorry for them and I quickly came up with an idea to get the car unlocked. Luckily, the passenger door wasn't closed all the way and if we pried the door with our fingers, the door was cracked open enough that you could at least slip something in between the door and the frame of the car.
Being that it was a fairly new vehicle, it wasn't "unlock friendly." There was really no way to unlatch the knob or power door lock switch. After thinking about this for a few minutes, I came up with the idea of using my electric wire fish tape to attempt to pull the keys out of the ignition and pull the keys through the crack in the door.
Using the fish tape was like playing an arcade game. (All I could do at this point is laugh.) I was having a heck of a time keeping the "springy" fish tape going towards the steering column. It kept going in all directions except the right one! Finally, after about 10 minutes of finagling, I got the keys hooked with the fish tape.
Due to the added weight now on the end of the fish tape, it swung wildly towards the passenger side floor. I thought for sure I had lost the keys, but after gently raising the wire, I discovered the keys were still dangling on the end of the fish tape.
Ever so slowly, I brought the keys closer to the crack in the door. With both of my guests pulling on the door, I slipped the keys out of the car! By this time we were all laughing about it. Just remember when you are out in the middle of nowhere, don't forget to carry an extra key! (I always keep one in my wallet.)
After they left, I went back to testing the solar panels, but by now the jet contrails covered at least a third of the sky (got to love those contrails) and real clouds were blowing in from the northwest. I tested about five of the panels and discovered that after they warmed up, the voltages were real close. Needless to say, not all of the panels got tested, but from what I could tell there wasn't much of a reason to continue this lesson in futility. I spent the rest of the day mounting the panels and not worrying too much about matching the panels in strings of three. I really don't think the difference in the power output is that great with the Kyocera panels.
Wednesday, was tackle a bunch of miscellaneous tasks day. One thing is for sure, you always have to plan for other odd jobs that must be done, taking you away from the "hot" projects. I'm always asked why it takes me so long to get things done, and this is the main reason why. (At least, it's my best excuse.)
Wednesday was the start of this year's mowing season, and the mower needed the oil changed along with the filter. Then I had to fix a flat tire. Then I had to mow for three hours. I stayed away from ravines and luckily didn't cause myself nor the tractor any damage, but most of Wednesday was spent doing odds and ends.
Carleton College Visits Day Creek
Thursday was put aside in order to meet with faculty and students from Carleton College. This event had been planned for some time now, and I was really looking forward to meeting with them. Richard Strong, Director of Facilities Management and Planning is presently working with a group of students to test the insulative values of various green building materials— one of which happens to be a double cordwood wall that they have built at their college. I am anxiously awaiting their test results and I plan to visit their college on June 1st, to find out more about their tests.
I hope the students enjoyed the visit as much as I did. They asked a lot of good questions and it was very encouraging to discover that there is quite an interest in green building amongst college students. Their talents and knowledge will go a long way to promote green building to the general public. (Class trips to Day Creek are always welcome.)
That's about it for now. This coming week will be devoted to building the second rack.
Remember last week's Woodcock story? Well, here's a photograph of the male Woodcock doing his dance to attract the female.