Does anybody see any problems with My Solar Power Plan? I've asked some specific questions, there, highlighted with this symbol: Q: Please, be brutal. This is a big expense for me, which I'm planning to make without much family support. It could backfire horribly by exposing my whole family to ridicule (not just me), and possibly tipping people off that we have likely made further preparations that would be of more interest to them (like food).

-- Y2K, ` la Carte by Dancr near Monterey, California (minddancr@aol.com), July 12, 1999

Answers

I've got a question for you regarding that 3-way fridge...do you know if it cycles on and off like a standard fridge does or does it run 24/7 ? The specs on it show a consumption of 100 watts per hour @ 115VAC and 7 amps @ 12 volts. If this unit is cyclic and at least somewhat well insulated, then assuming a duty cycle of 50% you'd be looking at 84 amp hours (1000 watt-hours) using 12 volts -or- app. 1200 watt-hours using 115 VAC. FYI...looks like the most efficient use of that fridge would be on propane. At an average of 2.5 lbs of propane per week, a standard 20lb propane tank would run it for at least 6 weeks. That's 4 tanks for 6 months. Something to think about anyway...might be easier than messing with lots of extra panels....then you'd only be looking at a minimal amount of solar panels to power the laptop, battery charger, etc. Roy Four Winds Renewable Energy Co.

-- Roy Butler (Roy@Four-winds-energy.com), July 12, 1999.

I looked into propane vs electrical refrigeration when I was setting up my own system. No matter how I ran the numbers, propane saved me several $K in initial system cost.
For short term use, or for limiting initial capital outlay, go with the propane reefer. Especially with these 'mutiple energy' units. The unit you refer to looks like an ammonia absorption type fridge - they work by using heat to drive an ammonia evaporation-condensation cycle. Using electricity to make things hot is a poor use expensive solar electricity. Propane powered freezers are available but they are very expensive.

Propane is cheap and easy to store. If you cannot lease or handle the larger tanks, get a bunch of those 20 pound canisters like used for barbecues. Make sure you have all the proper adapters - fridge to tank, and make sure that adapter fits your tanks. There is a new style of fitting coming online for the smaller tanks.

I would not plan to put the heavy batteries full of corrosive liquid in your attic. Keeping the batteries around 70F is about ideal. Don't let the batteries (lead-acid, flooded or sealed) freeze. Although, charged batteries don't freeze until they get well below 32F.

I assume that you are above the typical fog layer in the Monterey bay area of Caifornia.

The panel you refer to looks fine, but Real Goods is kind of pricey - check out N Az Wind and Sun

ht tp://www.windsun.com/Inverters/trace_inverter_specials.htm

or Joel Davidson's PV bulk buy

http://home. earthlink.net/~joeldavidson/index.html

You will of course need appropriately sized charge controller(s), disconnects, fuses, cabling. A large inverter will greatly extend the utility of your system. best regards

-- been there (done@that.com), July 12, 1999.

Thanks, Roy & "been there," and to another reader who wrote to me privately for your answers thus far.

Roy, you asked "if [my refrigerator] cycles on and off like a standard fridge does or does it run 24/7 ?" A call to Lehmans reveals that it cycles in propane mode only, not in electric modes, whether A/C or D/C. So your calculation is correct as stands.

I could certainly better insulate the unit if only by cutting a water heater blanket to go around it, and flap to rest on the top. I would probably only have to get into it twice a week for my own meds, unless my husband's health goes so drastically south by the end of the year that he ends up on insulin (He's a TypeII diabetic).

I'm still not too clear on how I'm going to get either method (propane or batteries) adequately ventilated. As it stands now, unless I can come up with something better, I will have to put this stuff in our yard (community property), where there is no fence, and it will be subject to almost certain theft.

-- Y2K, ` la Carte by Dancr near Monterey, California (addy.available@my.webpage.neener.autospammers--regrets.greenspun), July 12, 1999.

Hi Dancr,

Well, you asked for brutal......:)

Q: Would it need to have a turbine?

You are going to have to vent those batteries, somehow, some where. I'm surprised Roy wasn't screaming about this because I know that safety is paramount to him. If the batteries are going into the attic you probably should consider bring air in from under the eaves and then exhausting some place else.......even if it's only under other eaves.

Do you have good under eave ventilation? If so, put the batteries in a good solid box with air inlet holes and a vent running outside (under eave). You could put an exhaust fan on the battery box and key it off the output of the charge controller.......when the batteries are being charged the fan goes on.

If you draw air in and exhaust using the eaves you don't have as much of a problem hiding the arrangement from the buildingnazis.

Q: Do I need to be concerned about any possible danger from freezing? I'm thinking no, since I know folks with huge propane tanks outdoors in cold climates, and people keep batteries in the freezer to prolong their life.

Been there is right. Keep the batteries about 70 degrees. If they get too cold they lose power. If they get too warm the water evaporates (lead-acid) and you have more of a maintenance problem.

Q: Does it seem as if this arrangement would be healthy since it's so near to our living space or should we plan to get the safer sealed gel cell batteries instead.

Putting stuff in the attic isn't unhealthy, but I don't think I would want an 8 year old boy going up to maintain the batteries. Some things to think about:

overcharging in order to desulfate the plates adding water checking water levels checking terminals and possible corrosion

all of this in an arena in which a wrench that slips across the + and - terminals can get cut in two by the current. uh, uh.

Keep at it, Dancr. You sure have the right idea.

-- de (delewis@Xinetone.net), July 12, 1999.

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-- 5 (4@4.4), July 12, 1999.