Friday, August 27, 2010

Solar system failures

Here's my latest renewable energy project -- repairing the solar power "motherboard" at our Bale House. This is just one of many repair and restoration projects I have to do over there to make it all work again.

This was all set up because the house is too far from the nearest grid power lines. Originally we had provided the house with a small scale solar power system providing 110V and 12V, backed up by a fairly expensive propane generator and a dedicated wiring system.

But the house's occupants broke the generator in the first couple years, mostly by running it too much, which they had to do because they refused to take or didn't listen to our advice to downsize their TV from a 100 watt cathode ray tube TV to a 25 watt flat screen TV. When the generator quit on them, I was able to go over over and salvage the unit. I repaired it, and decided they couldn't have it back if they were going to treat it so badly. They would have to live off their solar "income" instead.

But I failed to make allowances for ignorance. Pretty soon the solar system was damaged in a lightning strike. It shouldn't have been damaged, and in fact had lived through dozens of storms in years past, but the ground wire had been disconnected, and so the excess voltage induced in the lines by the atmospheric electricity had nowhere to go. This most likely happened because the occupants had worn out the battery pack, but rather than tell me to have it changed (probably didn't want me over there to see their mess) they had hooked up a car battery. In doing so they had failed to connect the wire to the household ground rod. The inevitable power surge eventually came and a very expensive inverter and charge controller were fried.

But having started, this round of user-error induced failure couldn't end there. A car battery can't run one of these systems for more than a half hour or so, so when that didn't work for them, they'd tacked all these 12 foot extension cords everywhere, which they'd hooked up to a gas generator outside, no doubt using a veritable "Christmas tree" of double or triple adaptors.

And it was a very old gas generator to boot, and was probably producing pretty low voltage a lot of the time.

This burn is the result. Lucky the place didn't burn down.

And of course, no-one bothered to hook the generator to a ground rod either.

At some point the male occupant moved out and became an ex-husband. I took pity on the female occupant and went over and replaced the batteries and provided her with a safe new generator, properly grounded, but I for durn sure wasn't going to give her a new inverter to break. I used one her boyfriend had bodged up for her. I just wired it up more safely.

Now I have to get the whole system back to the original level of performance and safety.

Luckily the price of these components has come down, while the technology has improved, so the cost of repair is less than it would otherwise have been, and the results better overall.

I paid a lot of money for the old inverter, a Trace 600 W standby type, and Trace C 140 charge controller. These were standard equipment for small scale solar design for many years, and very robust.

I was able to replace the whole shebang with new, up-to-date gear for less than I paid for secondhand gear 8 years ago. I used a Cobra 1,000 RV-style inverter, which provided more wattage than the Trace but doesn't need a standby circuit because it draws very little power when on. The new inverter runs without a sound, and has a built-in input volt-meter and output wattage meter. The old inverter was slightly noisy, and the entire system had only a variably flashing LED (on the charge controller) for voltage, and not a very accurate LED at that.

Very nice. We'll see how long it lasts, though.

The white thing on the motherboard is the new charge controller, which is a Xantrex C35, basically the Trace C40 (with the same old LED!), but without a shunt for excess power, which experience shows is rarely produced by this system.

There were newer, fancier, and cheaper units, but the price of the C35 was much lower than before and they are very robust units despite being a 30 year old design. The black thing is the new inverter. I also went through and reconfigured the wires to make the connections more straightforward, and I put a smaller main breaker in to protect the inverter.

On reflection, I know and have always known that technological understanding evades some people. The level of complexity that is reflected in even a small scale solar power system is far more than a regular house with 200 amp supply, because the regular house doesn't run out of sunshine, while the breaker and grounding system is fail safe.

The solar house, especially the small scale, off-grid solar house, is always in danger of running out of power. You get a fixed maximum supply every day, and if the sun doesn't shine, you don't even get that. This house produces about 300-400 watts a day on average, about 1000 watts on a good day, and none at all on a bad day. That's enough for some light and music, a couple hours of a small TV, and to run the 12 V water pump, but no more. And it's only fail safe as long as you don't mess with it.

Here we provided the building with a breaker and grounding system that was initially fail safe, but we could never provide enough sunshine to run all the normal range of American lifestyle appliances that the occupants wanted to run. Instead of adapting to the new low power lifestyle, they tried to adapt the home to their original high power lifestyle. The result was a cascading system of failures, one after the other, each one adding another level of safety issues, and each one setting the system up for the next failure.

If we ever do have a major climate and energy crisis, one greater than the current chronic disruption, it will cascade like this too. The trick to avoid this is to call a time-out right at the beginning and work to get systems back to a safe and functional level before making things worse.

(And if the owner/designer says the house can't run a 100 watt TV, the house can't run a 100 watt TV. Even a secondhand 25 watt portable TV would have cost $50 and saved the whole system.)
Here's, too, the recycled metal roof I put on the Bale House kitchen last Saturday. We had a pretty good rainstorm Wednesday, and no water came in, so I'm happy with this job.

And here's another local numpty, a woodpecker that woke Aimee up, and surprised me, by drumming loudly on our house the other day.

In other GFD news, we have lots of tomatoes, so many that I am now canning only one variety: the miniature Roma-type called Juliets. We're going to make some fresh salsa, and then I guess we'll take them to college and give them away.

And the first day of the fall term is Monday. Global Change at 8am. Better get some coffee.

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