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Pedin · Guren


A bit more attic and roof work

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I am a bit behind in the journaling, trying to keep up with the maintenance cycle this year since the bug ticket items are due work: deep PV panel maintenance, battery bank replacement, rezoning the heating system,... Well, here's a view of the rooftop panels:



As I was up there at the time and no one was around to perform the photojournal, I have to go with a 'stock' shot. The roof peak is 26 feet above the ground and the front roof slopes 37 degrees, so it is basically a metal slide. Each of the modules can be pivoted up, and with wooden stand-offs, it is possible for me to slip under them with a rope harness to service the wiring. Module #8, panel #2 had the faulty wiring.

A week later, my housemate complains that he's uncomfortable at any temperature less than 80F. I pointed out I am not going to turn on the heating system in the summer, and advised him to get some heavy clothing and begin an exercise regimine immediately since the heating system will keep the place at 70F in the winter (extra sun notwithstanding). He's taking the advice well, off on a stationary bicycle hoping to raise his core tempoerature. Nonetheless, I decided to rezone the heating system. When I installed the hydronic system, I had it engineered with 14 heating loops each capable of being a zone if required. My initial setup split the house into two large zones.  The entryway and office above it are in two heating loops, and since this is where housemate has his office set up, I decided to change the system into three zones. I'll set the studio wing to coast down to 62F, the main wing to coast at 70F, but raise the entryway to 73F in the early monring winter at 5AM in preparation for his 6AM forray into daytrading futures.

That zone adjustment required going into the attic to run telestat cables from the mechanicals room across and down into the mainfold in the studio. Though I did this at 8AM, it proved massively hot in the attic:



Here I am in flight suit all covered up to avoid havng cellulose insulation plaster itself onto my body. While I was up there, I also rewired things a bit, adding an attic light switch and an extra outlet to help me when I work up there. Now I no longer have to fish about in the dark trying to plug in the attic light into a hard to find plug, and when I have to clean up the heat exchanger box, I'll have a plug nearby for the vacuum cleaner and extra lights.

My final bit of deep maintenance was to check all the batteries. I presently have a series of 4 batteries (48V) in 4 banks (16 batteries total); each battery is a 12V 258A 8D unit which when discharged to 50% should yield a capacity of 1.5KWh. The entire bank should be capable of delivering 24.8Kwh. In practice the capacity is a little lower because the current draw can sometimes be much higher so the internal resistance at those higher draws reduces the  aggregate capacity. Still, it was clear I was not getting that anymore; it was looking like 11KWh. Voltage checks during discharge and charging intervals revealed 7 bad batteries and another questionable one. I am not surprised since 8 of the 16 batteries are just shy of 6 years old. Their life time at 50% DOD is 5-7 years.

I ordered 12 new batteries, 4 extra ones (20 total) to augment the capacity up to 31KWh. Housemate runs a tower computer with multiple monitors. I got him to ditch the monster CRTs for LCDs, but even so, the energy demand is higher, that along with his TV watching and satellite recevier. The price for the new batteries came out to $6100, which when amortised across six years becomes $85/month. Now wthat is not at all bad considering the Califronia energy rates. Still, off-grid PV living is not inexpensive. This is clearly a life-choice.

Some time soon I need to add the solar hot water heating system. All the copper plumbing is in place for that eventuality, and now that propane prices are up 25% it is time to take advantage of the sun yet again.  I will watch the shadows this winter to determine the best site for the evacuated tube collectors.



Current Locale:
Kirkland
My temperment:
accomplished accomplished
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[User Picture]
On September 6th, 2006 02:00 am (UTC), insomnia commented:
Solar still appears to be bleeding edge... especially if you fall off the roof.

Applied Materials just unveiled a big program today to move into solar energy cell fab equipment. This is pretty cool, as it hints at a significant increase in economy of scale, as well as integration of Applied's semiconductor and LCD technologies, which they believe will allow them to deposit thinner layers on solar module, reducing costs considerably, as well as attaining higher power yields.

They released a powerpoint presentation that has some details on projected costs / yields. Their audio presentation mentioned the possibility of being competitive with conventional power plants in a few years, and also pointed out an interesting factoid -- the entire country could be powered by solar cells in an area the size of 100 square miles.
[User Picture]
On September 6th, 2006 02:50 am (UTC), elimloth replied:
Solar still appears to be bleeding edge... especially if you fall off the roof.

:-) Yes, a fall takes me in the red.

Solar is still bleeding edge for off-grid living. Power storage is in a primitive state. It is a much better and communitarian endeavor for on-grid situations. Much of the advantage of on-grid solar is its ability to level the power peaks of the convential powerr plants which then run more efficiently.

BTW, thanks for the link!
[User Picture]
On September 8th, 2006 01:09 am (UTC), insomnia replied:
"Power storage is in a primitive state. It is a much better and communitarian endeavor for on-grid situations."

Maybe they just need to build a better flywheel.
[User Picture]
On September 8th, 2006 06:54 am (UTC), elimloth replied:
Maybe they just need to build a better flywheel.

I truly wish there were decent flywheel storage systems. When I first built the house and its power system, I scoured the alt power companies but found nothing suitable. It is easy to find flywheel storage systems that deliver a lot of powr for a short time (e.g., 190KW for 12 seconds), but what I need is a system that stores 50-100KWh, delivering across 2-4 hours with a holding time of 12 hours. Only fancy vacuum flywheel systems can do that. I also looked for fuel call and hydrogen catalyzers, but nothing came close to 30% sotrage efficiency or lower than millions of dollars. So, it was good old lead-acid battery technology.
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