Answers from Home Power Readers Flues and 24 Volt Equipment In answer to Loren Amelag's question about a coating for his solar flue (HP#10, pg.42). 1) EPDM rubber used for roofs. Some calls to roofers might yield enough left over material to do a small area. 2) Premixed cement used for mortarless concrete block assembly available probably in local lumber yards. These mixes contain special glues and fiberglass filaments so they can be trowled to 1/8th of an inch without cracking. 3) "Insulcrete" made by Dow is a similar material which was specifically designed to be trowled (or gunnite sprayed) over fiberglass laid on top of "Styrofoam". It also contains special glues and fiberglass filaments. Recommended thickness = 1/4 inch. In answer to Nancy Dooley about locating 24 volt equipment (pg.42, HP10) try Solar Retrofit Consortium (Box 34, 200 E. 71st St., New York City, NY 10021-5138, (212)-517-3580), an advertiser in HP. I spent an hour talking to their head designer about their products, all solar and AE equipment, some of which they manufacturer themselves. He told me that 90% of what they have is not in their catalogue. I'm getting the catalogue anyway. He said they have about 8,000 DC motors in stock, ranging from 12 to 48 volts. They make their own refrig which he claims is about 30% more efficient than SunFrost, largely because it has more insulation. The insulation is shipped separately as it makes the frig too big to go thru standard doors! It comes with a small fan and vent so the heat can be directed outside. Maybe cold can be directed in reverse in the winter? It also has a tray for condensate which can supply distilled water for batteries. Apparently in the first 3 months of this year they sold $1,000,000 worth of equipment, mostly to the Caribbean and Third World countries. They have a contract with Eureka to make a full sized 12 volt vacuum cleaner. Thought you might like to know about these folks in case you didn't already. Delighted to see your readership growing! Due to the quality of your mag, I hope you will become a truly major national asset to all of us who want to go with AE systems. I am particularly impressed with the space given to reader responses. In a field as new as this, the quickest way to learn is from the successes and failures of others. Cordially, Donner Denckla, Washington, DC Wood Burning Hot Water Heaters Dear Home Power Crew: Keep up the good work as it is GREATLY appreciated by all of us. Patricia Ganyard inquired about a wood burning water heater in the Q & A section of HP10. That jogged my memory a bit to look this one up in the Cumberland General Store catalogue. Their address is Rt3, Crossville, TN 38555. Thanks A lot, Barry R. Smith, Olean, NY Thanks Barry. The heater that Barry is talking about is a Magamex Model R-3. The Cumberland Catalog says that this heater is designed for a maximum water pressure of 200 psi, is compatible with existing plumbing, requires only the installation of a stovepipe and standard U.S. 125 psi temperature and pressure relief valve. The Magamex has a 14 gallon capacity but is designed to heat up quickly and then provides a continuous flow of hot water as long as the fire is maintained (three or four chunks of wood the size of 12 inch 2x4's every half hour, during periods of high demand, provide all the hot water you'd need). The promo also says that you can use junk mail and shredded cardboard for fuel. The dimensions are 11.41" diameter, height 57.08", weight 50.05 lbs. Stovepipe size 4", firebox 11"x22 1/2" Shipping weight 60lbs. Shipped FOB Price $306.25 (Don't know how old the catalog is though). KP More on Wood Fired Hot Water Heaters Someone wanted to know about wood fired hot water heaters. The "AguaHeater" is available from Domestic Water Works, POB 809, Cave Junction, OR 97523, (503) 592-3615. No price is listed in the catalog so you have to call, probably the price changes a lot. So there you are. Hope this helps someone. D.S.,Hayfork, CA More on Palomas Dear HP Besides being a successful soccer coach and father, etc. my one claim to fame is my service experience with Paloma water heaters. Regarding Tim Traquair's problem: The spec. on the PH6DP Paloma says: Min. water pressure 4.3 psi. Firstly, that number only applies when the heater is turned completely to the "hot" setting. What that number means is that the incoming water pressure must exceed the resistance thru the plumping system by at least 4.3 psi for the heater to fire on the "hot" setting. Each elbow, valve and vertical run downstream from the heater has a resistance measured in psi. If you were to calculate total resistance to the outlet of the showerhead (which incidentally can be as high as 10 psi) then you add the 4.3 psi and you know how much pressure you need on the incoming. Gravity feed is certainly a problem for all tankless water heaters. The heater with the lowest pressure requirement among all tankless water heater brands is the Paloma PH12M and the Paloma PH16M. Both require 2.1 psi more than the resistance on the outlet side to make them fire on their "hot" setting. The reason for your problem is product safety. I would not suggest an tampering with the Paloma. What I would suggest is putting a 12V pump on a toggle switch and when you want hot water flip the switch and open the spigot. Neil Green, Low Energy Systems, 2916 S Fox St, Englewood, CO 80110, (303) 781-9437 More on Palomas and Sterling Engines Question In response to Timothy Traquair's problem (Q & A HP9) with Paloma propane water heaters not coming on because of low water pressure from his elevated water tank. I had the same problem. I also have an elevated water tank. Most times the heater would not come on, on demand, because the water pressure was too low. I over came the problem by ordering a Flojet 12VDC pump from Real Goods in Ukiah, CA. I installed it between the tank and the water heater. This pump has a built in pressure switch which turns the pump on and off automatically. After installing the pump, the problem was solved, the heater came on whenever I opened the valve and then the pump came on and kept the pressure up. Also in HP9's Q & A I read where Linda Roger's is planning on wiring a sterling engine to supply electricity. I wish to get more information about the sterling engine. I did not know they made sterling engines that are of any use other than experiments and demonstration. Isaac Amstutz, Dublin, MS For more information on sterling engines contact Stirling Technology Inc., 9 Factory St., Athens, OH 45701, (614) 594-2277. These folks make a homestyle 5 HP. sterling engines capable of producing 3.5kw, ac or DC. KP A Bunch of Answers to Questions from HP9 Hopefully I can provide answers to several questions some of your Home Power readers have posed in issue #9. First DC washers: In many washers the ac controls can be eliminated or bypassed providing an all DC machine, although without the timer, etc. I usually use old machines that have been given to me and so most of the time the timer and/or water level switch is bad anyway. Sears machines have a motor that turns in one direction, the agitation and spin cycles are shifted by two small solenoids. The motor obviously needs an on/off switch if converted to DC operation. It may be possible to use the solenoids with DC but will probably require replacement with a 12 Volt solenoid winding. At any rate, all that is required to shift this machine is a three position switch which has on-off-on positions. The center position places the machine in neutral, while toggling to one side selects agitate and toggling to the other selects spin dry. Many machines just reverse the direction of rotation of the motor to shift from agitate to spin. This is even easier to effect once the DC motor is installed. Thus all controls but a forward/reverse switch can be completely eliminated. I prefer this manual control over the sysles myself. On water pumping windmills and using them to produce electricity: This is a marginal idea. The water pumping is optimizied for torque (twisting force) NOT power. The truth is that all of those vanes get in their own way. A single blade is the most efficient for developing power. The "secret" here is drag; the force you feel on your hand when you put it out the car window. With a single blade drag is minimized and power ( and rotor speed) is maximized. With 16 or 20 blades drag is maximizied. In fact drag is so extensive on these multi-blade turbines that the power output of a waterpumper is self limited to 2-3 horsepower because as the turbine gets up to speed drag quickly costs more horesepower than the turbine can produce. So why multi-blades? All things are a comprise. Although a single blade produces the most horsepower per disk rotor area you don't see many. Although, if I remember correctly, the West Germans were, are, or have built a large one. Most wind turbines are 2 or 3 bladed. This is a comprise for balance and/or rotor strength. With a water pumper maximum output is not as important as with a wind generator. You want that hummer to start pumping in a gentle breeze and to keep pumping as long and as often as possible. To pump water you need to overcome a lot of inertia (weight of sucker rod, pump, and water being pumped) and friction (of pump, seals and flowing water) to even get the thing moving and you want to do this in practically no wind. Thus high-end performance of a water pumping windmill is compromised to maximize performance at low wind speeds. These units can start pumping in winds as low as 3 mph compared with an absolute minimum of about 9 mph for an electrical wind generator, most need about 12 mph for an effective output. I am not trying to say "never" to use the use of a water pumper for generation. Compromise is the name of the game. If you have one it may be easier to attach an alternator to it than to spend the $1,500 to $10,000 to do it "right". Just remember that you ARE making a compromise. On converting the Servel or probably any other gas refrigerator from natural gas to propane/butane (LP gas): Natural gas has much less heat energy per cubic foot than LP gas, thus a natural gas appliance must use about three times the volume of fuel than a propane/butane appliance uses. This means that the metering hole that helps the flow of natural gas must be larger. To convert to LP gas this metering orifice must--somehow--be shrunk. I have accomplished this several times on Servel gas refrigerators by removing the metering orifice in the burner and VERY CAREFULLY peening around the edges of the hole in the middle with a center punch. This will dispalce metal toward the orifice closing it slightly. You can use a sharp needle or awl to round the inside of the orifice for smooth gas flow. I stress that this is NOT the prefered factory method and it helps to understand what you are doing. The correct way is to replace both the orificeand, in the Servel, the turbulator beneth it and to choose the correct orifice based on actual measured gas flow. In some cases even the burner unit will have to be changed. A CAUTION here. When disassembling the burner unit in a Servel DO NOT, under any circumstances, try to remove the "Clixon" safety valve for any reason. This is not designed to be removed, it is not serviced separately from the burner and an attempt to remove it will likely remove all of the threads inside the burner which the "Clixon" is screwed into --98% chance of this--requiring purchase of a whole new burner. You must keep the inside of the orifice smooth to keep the gas flow smooth. Fuel gas normally flows through the turbulator, which imparts a swirl to the gas, then it flows out through the metering orifice and into the burner mixing chamber. The natural gas turbulator has two grooves in it to accomodate the extra volume of that low caloric gas, while the LP gas turbulator only has one. Ideally the LP gas turbulator should be used to keep gas velocities up but the natural gas part works--of a fashion. These are worst-case "field modification" instructions. Were possible you will be ahead by having the conversion done by a knowledgable person who has the correct burners, orifices and turbulators on hand. Last is inverter hum in electronics: This hum can be minimized in some equipment by the simple steps of using grounded 3-wire outlets and also trying different positions for the 120 vac plugs. For instance, if a turntable is plugged into a switched receptacle on the back of a stereo it can build up a 60hz field on its chassis. Grounding the chassis directly to the third (grounded) prong on an outlet (make sure that it IS grounded) can sometimes reduce the hum markedly. So can simply unplugging it, turning the prongs 180¡ and plugging it back in. This works because there is a "hot" lead and a grounded lead on most tools and equipment and if you get them reveresed it can feed the 60hz signal into the amplifiers. Once you've minimized the hum this way you may not need a noise filter but if you do you will find it much more effective. GEI (Gas Energy Inc.), 166 Montague St., Brooklyn, NY 11201-9871 makes gas air conditioners, as well as those running on steam and waste heat. Infortunately they are only useful if you happen to own the Empire State Building as they are designed for industrial complexies. Solar evaporative coolers are here already. Contact the University of Arizona, Environmental Resources Lab, 2601 E. Airport Dr., Tucson, AZ 85706-6985. Ask about the Oasis Project and cool tower technonolgy as well a solar chimmneys. Clifford W. Mossberg, Fairbanks, AK Q & A on Ni-Cads Congratulations on your fine publication! I'm really impressed to see how it is growing. I hope to spark some discussion on a topic I have yet to see discussed between your covers--rejuvenation of "dead" ni-cads. I buy and use a lot of surplus ni-cads of primarily AA and, more recently, the 4 A-h D sizes. Although I am careful to fully cycle my batteries every month or so to avoid the formation of a dysfunctionally short "memory", it is often the case with these surplus batteries, and occasionally with new ones, that they cease to take a charge after a year or so of regular use. I have recently discovered, through trail and error, that I can use very brief applications of higher voltage current to reactivate these batteries, and it is this I would like information on. When I use my Radio Shack Universal Voltage Adaptor, 7.5 Volts at 300 mA. is enough to get AA's going. At first I left this current on for long periods, but I soon found that it only took five or ten seconds to affect the battery enough so it would then accept regular charging current. C cells and the big 4 A-h D cells seem to need more than my little adaptor will give. The only resistor I had was a 3 ohm, 3 W. model, so I tried that. It took care of the C cells in two to three seconds, before it had time to heat up. But the big D cells needed more time and the box-like resistor was hot enough to melt zip cord insulation before each of the five of the seven batteries I tried to fix would take a charge. Two of them still read zip on my voltmeter. So, finally, to the questions: What am I doing to these batteries? Will it last? Assuming this fix is worthwhile to do (and it seems to be for me--I'm using batteries that haven't worked for ages), how do I calculate correct resistor values and "zap" times for various sizes of batteries? Last, but not least, why would ni-cads cease to take a charge after only 300 or so cycles, anyway? Is there a way to avoid this in the first place? Many thanks for the forum you provide. Hard to image life without Home Power. Rick Goodier, Huntsville, AR Zapping works! After many cycles, nicads develop "dendrites". Dendrites are whisker thin tendrils of nickel and cadmium that form short circuits between the cell's electrodes. A dendrite is just a few molecules thick. The dendrite can be vaporized by running a substantial amount of current through it in a very short period of time. The trick is to vaporize the dendrite without gassing and ruining the cell. All nicads have vents to protect them from explosion caused by too rapid charging. Some nicads contain resealable vents and some have vents which only operate once. I've zapped single D sized (4 A-h) cells using the following method. Place the nicad cell's case (it negative pole) on the negative pole of a large lead-acid battery. I use a single L-16W (6 VDC at 350 A-h). Hook a 14 gauge copper wire to the positive pole of the lead acid battery. Touch this wire to the top of the nicad (it positive pole) for just an instant. There will be arcing and sparking as the big lead-acid battery puts about 10 to 50 Amps. through the small nicad. The nicad will get hot. BE careful when zapping. The cell may explode if you overdo it, so wear goggles and gloves. While I've never had one explode, I have ruined some by venting the cell. If the cell is cooled in the snow or in the freezer before zapping, then venting is greatly reduced. Zap the cell only once, then cool it before zapping again. Some cells take several zaps to vaporize all the dendrites. Use a smaller lead-acid battery (or fewer series cells of a large battery) to zap smaller nicads like C and AA. A lead-acid battery works best as a zapping source because it can deliver high amps easily. After zapping, recharge the cell normally. I'm still using cells I recycled over five years ago, so the fix looks permanent. Dendrites can be prevented by proper recharging. Use high ampere pulses to recharge the nicad. This vaporizes the dendrites as they form. See HP#5, page 27 for detailed info on recharging nicads using pulses, building a pulse type charger, and zapping. RP Self Regulating PVs I know that Kyocera, ARCO (and perhaps other manufacturers) have "Self Regulating Modules". These generally have fewer cells and consequently operate at lower voltages (ie. 14.5VDC) instead of the typical 16 to 17VDC modules Since you are the author of "The Complete Battery Book", I would appreciate your comments as to: 1) What are the most appropriate applications for Self Regulating Modules (SRM's): a) 1 Module for 1 battery (ie. RV, boat) or b) 4 modules for 4 batteries (ie. cabin)? 2) Will an SRM do a good job of fully recharging a conventional lead acid battery (ie. RV, marine deep cycle, golf cart, etc.): a) in mid-winter and b) during hot summer days? 3) Can an SRM "overcharge" and damage a battery? How can I tell if the battery is being overcharged? 4) If a battery can be overcharged by an SRM, and what can I do to prevent this from happening? 5) As a general guideline, under what circumstances is an SRM a good choice? Joe Solar, Sun City Well, Joe, you've asked a mouthfulÉ Let's start with question #1. The best use of SRMs is in small (one battery Å100 A-h and one SRM) intermittently used systems. Larger systems are better off with standard 36 cell modules and a regulator. This is an energy vs. cost decision. Question #2: Yes the SRM will fully recharge a lead-acid battery, they just take much longer to do it, especially when the battery is above 75% SOC. The SRMs also recharge slower as the winter's cold elevates the recharge voltage of cold batteries. All PV modules decrease in output when the get really hot during the summer. The same is true only more so with the SRMs as they have fewer cells to work with. Question #3: Yes, an SRM can overcharge a battery. Over a long period of time, an SRM in an unused system can eventually boil the battery dry. The problem here is not really the SRM's fault, but the user's fault for not doing his maintenance. If a system must be left unattended and unused, the even the SRM must be controlled to prevent boiling the battery dry. Use a blocking diode to drop the incoming voltage by Å0.5 Volts. Use Hydrocaps to recycle the water lost by the cells. Leave a small load on in the system. Or finally use a regulator. Question #6: The SRM is best applied in small system cycling under 20 Ampere-hours per day. RVs and occasionally used cabins are good places for SRMs. They are not cost effective in larger (>40 A-h/day) systems, or systems with large temperature extremes (average daytime temps >100¡F. or <30¡F). RP Stoves A friend brought by a copy of your magazine. It's great. What do other people with 12 volt systems do about the 110 requirements of gas stoves. We used to have an old stove. Now we've bought a middle aged one and the oven doesn't work unless the timer is plugged in. Does anyone have alternatives to buying an inverter? Diane Paget, POB 223, Philo, CA 95466 The problem is an electrically activated valve that controls the gas to the oven on command from the timer. Remove or bypass this valve and you'll have a regular manually controlled gas oven. The thermostat is almost surely thermally operated and requires no electricity. If you're not handy with tools, then get your local appliance techie to help. RP LED Voltmeter A friend just sent me #10. I think it's great. I design and install these systems locally. Your articles seemed right on and I like the access to other people, ideas, and manufacturers you provide. I am, today, following up on the permanent magnet motor patent letter (hope I can make something of it!!). Is there any easy way I can get the LED voltmeter to give me 1/10 volt increments? Can anyone there tell me why I can only get LED's in red, green & yellow? No clear? Blue? Bill Seckler, SolarWind, POB 780, Bandon, OR 97411 Yes, the LED Voltmeter can be made with 1/10th Volt resolution. Directions for "cascading" several LM3914N chips is in National Semi's application literature. It will take 50 LEDs to cover the range of 11 to 16 VDC with 1/10 Volt resolution. That's complicated, expensive and consumes a fair amount of power. If you want that degree of resolution, use a digital meter. It will be more accurate and cheaper. The color of an LED is determined by the composition and construction of its semiconductor junction. There are only a few compounds that can be made into junctions which will emit light in the visual range. There are blue LEDs, but they are very hard to make and expensive (>$50 each). All LED junctions emit very monochromatic light. White light is made up of many colors and no one now makes an LED that produces white light. RP Access and Passive Solar Do you have/know of a mail order source for: 1) radiant shield discussed on page 21 of HP10 2) Solar Shade screen material discussed on the same page and issue? Also, what are the range of options for passive solar hot water rather than a black hose hanging in a window or laying on a roof in the summer. Also, do you know of a mail source for tankless hot water heaters discussed on page 22 HP10. Ronald Bushy, Stigler, OK Solar Components Corp., 121 Valley St., Manchester, NH 03103 ¥ 603-668-8186 can supply radiant shields and other solar heating/greenhouse products. Tankless hot water heaters are available from Real Goods, see page 2 this issue. RP