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In reference to E.S. Spiak's letter asking for silicone RTV, GE makes one which I believe is #555 (their code), and Dow Corning makes one called Silastic E RTV. Both are two part mixes, and cost from $12-15 per 1.1 pound kit. They can usually be located at places selling rubber products (raw materials), plastic raw materials, sometimes large electrical supply houses, or sometimes large crafts or jewelry supply houses, as they are used for making molds. Or you can write Dow Corning at Midland, MI 48640 and ask them where the nearest supplier is, or order it from them. The material is easy to mix and use, but has a shelf life of 6 months to one year. Each company makes a line of silicone rubbers, for different applications, so you might want to look at the entire product line before you choose one of the above, as it is primarily for molding.

Sincerely, Rives McDow, Leicester, NC.

Stoking Up Calentadors

Dear Friends at Home Power:

This is in reply to Clyde Gress and others who wrote letters regarding wood-burning water heaters in issue #12.

In 1979 I founded Appropriate Technology Importers, Inc. for the purpose of importing wood-burning water heaters ("Calentadors") from Mexico. It was a good idea that over time evolved into a not-so-good- idea. My only ambition was to support myself and family with a reasonable income while providing a valuable product at a fair price. However, Mexico's runaway inflation soon made each shipment cost more than the previous one, and it became extremely difficult for me to maintain stable prices from month to month. Finally it reached the point where I couldn't earn a living without pricing the product higher than I felt was reasonable. These were great little heaters, but by the time we got them trucked from Mexico City, through customs, into a warehouse, and finally shipped to their destination, the price was more than most people wanted to pay. I sold the company in 1981 to New Atlantis Enterprises, who are now also out of business. The last contact I had with I was told that wood burning water heaters are not even being made for the Mexican market any more. (This may only apply to the Magamex brand that we were importing, although the last time I was in Juarez I couldn't find calentadors of any brand for sale in the hardware stores.) Don't take this as the final word, however. If you visit any border city in Mexico check the hardware stores outside the tourist zone. Ask for a "calentador de agua para lena." ("Wood-burning water heater.") Be cautious about purchasing "a no-name" brand made in someone's backyard: These are fairly common, but they are often more folk art than useable water heater. Your next choice may be to make one by welding a fire box to the bottom of an old gas water heater. This isn't hard to do, and they work quite well. Always install a Temperature and Pressure relief valve on the heater -- these are available for about $10.00 in any hardware or building supply store. I am willing to answer brief questions on this subject only if you send an SASE.

Sincerely Yours, James B. DeKorne, POB 145, El Rito, NM 87530

Answering Machines Revisited

Dear HP,

I read with interest Joseph Berube's letter (HP12) regarding problems with DC powered telephone answering machines.

Our machine is a Radio Shack TAD-252, combined phone and answering machine, which is equipped with a 12 volt input (DC)

and sold with a transformer for 110 vac use.

However, when we use this machine on our 12 volt battery system, there is a strong hum on the phone whenever the answerer is plugged in. Sometimes incoming calls are accepted by the machine and then immediately cut off.

We have found that disconnecting the entire battery system from its ground somewhat alleviates the problem. It has been suggested to us that the problem lies in the "interface" of the phone with its combined answering circuits, and that the ac transformer normally would also act as a noise filter.

Can anyone help us solve this problem? Is there a way we can filter or isolate the noise while using DC power? Like Mr. Berube, we would be greatly indebted!

On another tack, your fine magazine demonstrates the "power" of "home" publishing. Perhaps an article on how you do it would lend power to others fighting for social change from their homes.

And for anyone who is interested, I'd like to tell the world that our ancient, $40, Servel gas refrigerator just keeps on running and running without the slightest problem. In ten years all we've done is replace the door gasket. Things that work!

Yours, Peter Ladd, RFD#2, Warner, NH, 03278

Peter: I had the same problem with our R/T system. Everything functioned fine until I added an answering machine (Panasonic KX-T1427) and then nothing worked. No phone (incoming or outgoing) no answering machine, no nada. The problem was that the answering machine had a different idea of what ground potential was than did the rest of the equipment. I solved the problem with a completely isolated battery/PV microsystem to power just the answering machine. Another solution is to use a DC to DC switching power supply to give isolation. These supplies are about $50 and will TOTALLY isolate any DC gear with ground contention or noise problems. Give the folks at Carlson Communications a call (advertisers in this issue), they have the DC/DC converters. RP

Wind Equalizer

Dear HP,

I want you to know what a great magazine you folks have! I always look forward to your magazine in the mail, and it's nice to hear about people who also believe we can all share in making our world more clean and healthy, or just plain ol' beat the big guys at their own game.

I originally started out with a Jacobs 32 volt wind plant, but found out that 32 volt appliances are virtually impossible to locate, so I converted the system to 24 volt. The wind plant would begin charging the batteries in a very light wind, but now I have found out that 24 volt appliances are still more scarce and more expensive than their 12 volt counterparts. I like the higher voltage overall, and I'm not willing to give it up without a fight - everything draws less current and uses much smaller wire. I refuse to use those heat generating, current guzzling linear voltage regulators. Have you heard anything about the Vanner voltmaster equalizer for keeping batteries equalized during discharge and recharge? How efficient is it? Does it work well or is it little more than caca? If you folks don't know, please print my name and address, so that someone out there might let me know that has one of those.

I would also be interested in building something to do the job. I tried to build a switched capacitor voltage divider using 140,000uf capacitors, oscillator, and some transistors But I can't get any better than 50% efficiency out of it - maybe from improper transistor selection or something. Maybe there are some tinkerers out there like myself who could give me some ideas on this problem. I have access to any discrete component, and I use mostly 4000 series CMOS IC's.


Thanks again for such a great magazine and keep up the good work!

Steve Robertson, 204 Sasser, Clovis, NM 88101

Steve: I've no personal experience with the Vanner Voltmaster. I know that Windy Dankoff of Flowlight Solar Power (see ad this issue) has done some work with the Voltmaster. Give him a try. The Voltmaster is really a switching power supply and high efficiency for these types of units is now around 80% to 90%. RP

Swimming Anyone

Hi Folks;

Great job you're doing with the magazine. I've got a question for you and your readers.

What are the various options for running swimming pool equipment (i.e. filters, pumps, etc.) on a 12VDC system? We have used a 12' diameter above ground pool for the last 2 summers without a filtering system and would like to get a larger above ground pool next year (15' x18' x 34") but it will definitely need to be filtered.

Aside from using a generator to run the 120vac equipment that comes with the pool, what 12 VDC equipment could be substituted? I'd like to hear from anyone who has tried various other ways to accomplish this.

Thanks, Margaret Waters, Rt2 Box 48, Twin City, GA 30471

How about it readers? Anyone using a low voltage PV system to circulate and filter a swimming pool? RP

PVs, Power & Pollution

Dear Home Power,

As one who has depended on photovoltaics for electricity for the last 7 years, I certainly appreciate the miracle of producing electricity from sunlight. Part of me feels self righteous about living with a "renewable" energy source that is not spewing out CO2 or nuclear waste. But another part of me realizes that the mining of materials and manufacturer of the panels is not a totally benign practice.

I would be curious if you have the following information?

1) What is the energy input per 50 watt panel for mining and transportation of raw materials?

2) What is the input per 50 watt panel for manufacture of cells and panel components (especially if there is plastic or aluminum in the frame)?

3) What pollutants and/or toxic wastes are associated with mining of the raw materials and manufacture of PV cells and panels?

4) What is the expected net energy of a 50 watt panel over, let us say, one 20 year period, assuming 4, 5, or 6 average hours of full sunlight a day?

5) What is the net energy of the system when one factors in batteries (to be replaced every 10 years)?

I suspect that photovoltaics may not be such an energy bargain. Indeed, I probably used up much potential energy of my first 35 watt panel the day I drove a truck 4 hours (one way) to pick it up. What I do like about PV's is that they are so expensive that I have learned to be extremely conservation minded. I cannot afford to use equipment that wastes energy. Getting the public to switch to photovoltaics is probably not as important as getting them to switch to the type of energy miserliness to which PV users are accustomed.

Sincerely, Mitch Lansky, Wytopitlock, ME

Gee, you HP readers sure ask easy to answer questions... Well, Mitch, the scuttlebutt I get within the industry says that a PV

panel now will produce more power within its lifetime than took to make the panel. Whether this includes transportation, mining, and the lights in the showroom that sells the panel, I don't know.

The basic material of PV panels is silicon (like beach sand). The "sand" is highly purified and formed into wafers. This purification process is the major power consumer in PV manufacture. The hyperpure wafers are then doped much in the fashion of any semiconductor, transistor or integrated circuit. It is these dopants that present a hazard to the environment. Like any other industrial process, if one gets sloppy/greedy, then we all suffer.

At 6 hours of full output daily, a 50 Watt PV panel will produce 2,190,000. Watt-hours in a 20 year period. All financial calculations we make about these systems are based on a 10 year system life. This means the whole system is written off after ten years. Now, most of the components (PVs, inverter, controls, etc.) will last much longer than 10 years, so this method of estimating is very conservative.

The energy conservation techniques we are learning in these RE systems can well be applied to kilowatt guzzling America. Everyone, please listen, consider what that appliance will consume before you buy it. It's not a matter of doing without anything, but of doing whatever we need to do efficiently. Make appliance efficiency a prime criteria when you buy your stuff and you'll be a happy kinda guy! RP

Zapping Nicad Packs

Dear HP,

I've been loaned a copy of #11 and like the magazine. Your coverage of a broad range of alternative energy topics and helpful hints as well is great, and has peaked my interest. I hope you will add me to your mailing list for future issues.

I plan to build a home in the mountains and will be beyond access of conventional energy sources. I believe that through reading your publication I can gain the knowledge needed to make an intelligent decision toward which alternative method to choose. As an added bonus reading Home Power is just plain enjoyable!

In issue #11, under the Q&A section, there was discussion about rejuvenating ni-cads. I wonder if I might ask Richard to extend his advice to 12V portable VCR type ni-cads. I have about 10 of these that either hold only a very short charge or no charge at all. I've been close to throwing them away many times but have renewed hope after reading of Rick Goodier's success and Richard's encouragement.

Thank you for the good work you're doing.

Sincerely, J.F. Moore, Richmond, VA

The same info (HP#11) applies to zapping the cells in the VCR packs. The very real problem with nicads assembled into packs is that we no longer have electrical access to the individual cells. Zapping cells as series strings is entirely experimental and anyone with a success story please come forward. If you can take the VCR packs apart and get electrically to the poles of each cell, then regular zapping works. If you cannot electrically access the discrete poles of each cell, then good luck. Incidently whenever zapping nicads, wear gloves and glasses.

If you cannot get cell access, then consider the following procedure. Recharge the entire pack. Discharge it in two hours or less into a large 12 VDC load (like a lightbulb). Repeat this procedure about four times. If the pack has the will to live, then this usually does it. RP

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