My "Solar" assisted car Years and years ago I purchased a 25 watt PV panel for 12 volt use in our home. When that power system was expanded, the 25 watt panel was replaced with 8 ARCO M 53's. As I contemplated a possible use for the original 25 watt panel I considered several facts. If gasoline engines are about 25% efficient, and auto alternators about 50%, then the conversion of gasoline to electricity would be about 13%. I then measured all the major electrical loads on my VW Rabbit, and figured that the 25 watt panel should handle the load. I mounted the 25 watt panel on the roof of the car and ran the wires directly to the battery through a blocking diode. The actual mounting was accomplished with RTV. Even though the panel protruded up into the air stream a good inch and a half, the gasoline mileage went up 7%. Most driving was short trips of 5 miles or so, and this meant more starter operation. To prove to onlookers that the PV panel was doing the job I disconnected all the wires from the alternator. Now the alternator was only keeping the belt tight on the water pump pulley. The car was driven this way about eight months. One December night I even gave a jump start to a fellow with a pickup truck. Finally on the 21st of December the battery gave out and I reconnected the alternator wires for the winter. More recently the 25 watt panel rode atop a small pickup truck. Though I left the alternator wiring stock, it yielded a 5% increase in fuel mileage. This, while still using a framed PV panel which raised the aerodynamic drag. The original battery in this truck lived to an age of 8 years! My most recent experiment is to use one of Photocomm's "duravolt" 25 watt unmounted panels on top of a '91 Subaru Justy. This panel has an unbreakable glazing which can be curved ever so slightly. I mounted the panel on the rear center of the roof and ran the wires down inside the rear hatch hinge gap. As can be seen in the photo, this made a neat, inconspicuous installation. With a panel thickness of about 10 mm there should be little additional aero drag. This front wheel drive Justy is EPA rated at 34 mpg in the city/39 hwy. So far (10,000 miles) the fuel economy has been about 39 mpg for trips of 5 miles or less, and the best has been 41.++ mpg. What remains is a full wheel alinement, and synthetic oil in the engine. Although the synthetic oil may yield small mileage gains., I will use, and dispose of less oil by doubling or trebling the distance between changes. What should be done for new production car? Engine and alternator size reduction is a place to start, (if it has to use gas) and the adoption of similar PV panels for electrical power supply. Maximum gains could be realized by regulating alternator output at about 13 volts and allowing the PV panel to "top off" the battery. Randy Laatsch, 11888 Wexford Pl., Maryland Hts., MO 63043 THIS LETTER CAME WITH PHOTO, WHICH IS IN PHOTOS 26 ENVELOPE!!!!!! Cool Condenser Dear Friends: I am writing to request a copy of the book Heaven's Flame. I have enclosed $10. Also please put me on the Oozie design newsletter. Its been a while since I looked at vehicle design (Ga. Tech Aerospace Eng 1972) lately I'm an AC power specialist with South Central Bell. From that I can tell you and your readers that used TELCO batteries will be very hard to get ahold of due to the need for documented recycling of the hazardous material. That's of course good, but it would also be good to keep the cells in use rather than paying to get them recycled. On using water to cool the condenser on a refrigerator, water cooled chillers are very common in commercial HVAC service. The existing condenser coil on a refrigerator is larger than would be required (designed) for a water cooled condenser on a factory model. It should work to drip (not spray) water down over the coil, and catching the water in a drain pan at the bottom. If you want to get fancy, you could wire up a solenoid water valve with the compressor to control (conserve) the water usage. The evaporative effect of the water would of course add to the efficiency of the unit but raise the relative humidity in the kitchen unless the coil was outside. Guess if it is outside you don't really need the drain pan either. (Just be sure to keep the condenser coil shaded all day.) Of course there are some places around where the relative humidity could stand some raising, but that thought doesn't occur around here. The amount of water needed would be very small. To figure the water consumption look at the spread of your available water temperature versus the room temperature. For each BTU/Hr your refrigerator is rated for, you're going to need 1 pound of water raised 1 degree F. (One of the few sensible areas for engineering in English measurements is heat transfer.) to allow for compressor inefficiencies, figure on 1.25 pounds. It works out like this: 1000 BTU/Hr refrigerator with water 20 degrees colder than the room will need about 8 gallons per hour or about 1/8 gpm. For the experts, yes, I know its the temperature between entering and leaving water temperature is much above room temperature, and efficiency is what the whole effort is directed toward here. Anyway this will only really help where the unit is in an area (room) that is normally warmer than the available water by 5 or so degrees, again except for the evaporative effect. To look at the evaporative effect (this will really help in hot and dry areas) remember that one pound (one pint) of water evaporated will take 970 BTUs of heat. That is about the amount of heat a refrigerator will move in an hour. Larry Bentley, KA5HKR, 905 Palm St., Jackson, MS 39212 Compadre Dear Home Power Crew: You are doing a great job. I love your magazine. I'm trying to give myself the time to write you a real letter feedbacking you lots of things from this very end of the world, that arose from reading and discussion of HPM articles and Q&A. More sooner than later I will do. When you are forced to find solutions far away from the supply of technology, many times, simple and cheap means of doing otherwise complicated and expensive tasks arise. I think we have things in common, we people who live in underdeveloped countries and you Home Power people in the USA. Our fight here is to convince short-minded people that development and progress by no means is to follow the wrong steps of the so called "developed countries" that led into pollution, extinguished animals and a very unhuman way of life. I think the right way is to join those like you who are already "coming back" from all that, and are leading mankind in the right path. There's still a lot to save here from destruction. We should work together. Keep up the good work. Diego Lorenzo Gomez de la Serna, POB Correo Central, Santiago, Chile Thank you, Diego, for a wonderful letter. I congratulate you on your far-seeing awareness. I believe all people using renewable energy are working together towards the common goal of a cleaner earth. It makes our hearts glad to know you are with us. - Kathleen Pump Power Dear Home Power, I am in the process of planning an alternative energy system for a cabin out in the woods. I have an idea that I would like some input on. I would like to use a Whisper 1000 wind generator that produces 120VDC. This would be used to charge a series of ten 12v deep cycle batteries. This idea seems worthy in that I can use inexpensive wire and the voltage would not need to be stepped up. I will still need an inverter to create AC from DC. A) Are there any reasons not to use a 120 volt power source? B) Would a mechanical inverter have any benefit in this system? I have an old shallow well pump. I would like to know if it might work in a hydro electric system to convert the water flow into power. The vaned rotor is 4" in diameter. I connected it up to a garden hose - it started to spin with pressure. The reason I am motivated to use this instead of a turbine is because it has the potential of not having to be at the end of the run. I could install it "in line" and use the push and the pull of the water supply to create power. I could put the working parts of my system in a location that is both convenient and accessible. Sincerely, Ben Laughlin, 2288 Rt 414, Watkins Glen, NY 14891 ¥ 607-535-4564 No reason not to run your battery system at 120VDC, Ben. Just keep in mind that all your switches, fuses, etc., must be rated at 150 VDC or better. 120 VDC is just a nominal battery voltage. The actual voltage of a fully charged 120 V battery system will be pushing 140 VDC or more. Finding a 120 DC to 120 ac inverter is a little trickier. Try Chad Lampkin at Michigan Energy Works-(616) 897-5161. By "mechanical" I assume you mean a motor/generator type? They do work and have the added advantage of producing a true sine wave, but are pretty inefficient compared to today's FET based units. Running a water pump "backwards" in a closed system as you describe can produce power, but unless we're talking about lots and lots of water, not very much. The push-pull that you describe only works if the water is flowing freely out the bottom end of the line at near zero pressure. That's fine if you are just using the water to fill a pond or something, but if you expect to use the water under pressure, you would be better off directing the tailwater after it freely exits your runner into a catchment and starting over from that point. - Bob-O Solar Anthem Dear Home Power Persons: Here is the new Official National Anthem of the Solar Power Movement. The song is intended for solo and group singing at all gatherings of one or more solar-minded energy- efficient people and their pets! This song is especially recommended for group singing whenever the TV news cameras roll during coverage of home power expositions wherever they may be held. Everybody join hands and SING! The words are by the shy but talented wordsmith Joel Chinkes. The music is by Giacomo Puccini, a familiar tune of his from the very famous opera about what's-his-name , the sad clown. O SOLAR MIO! O Solar Mio! Mi Sol Est Free-O! Frio? Not Me-O! Mi Sol Est Warm! O Solar Mio! Voltage For Free-O! Photon Est Clean-O! Free Am-per-age! So Come! Enjoy The Sun! Clean Energy For Ev-ry One! (Repeat three times) Lyrics Copyright © 1991 by Joel Chinkes. Solar minded people have permission to accurately reproduce these lyrics in any form provided proper credit is given. Yours truly, Joel Chinkes, Cincinnati, OH 45244 I'm just guessing here, Joel, but before you were an HP subscriber you read MAD magazine regularly, right? - Kathleen Jeez, another maniac crazed on PVP (PhotoVoltaicPower)! -Bob-O Solar Help Dear HPM Staff, Thank you for this great magazine! Please renew our subscription for two more years. We have been off the grid since 1974 and we have been using solar electric since 1982, and we love both. My husband is disabled with multiple sclerosis. He has been working on some solar electric devices to help other disabled people be more independent in the backwoods. As I am pressed for time I will not elaborate now, but if anyone is interested I will gladly write more. Sincerely, Lu Marie & Michael Strickland, Dearborn Solar Electric Co., Rt. 1 So., Box 2364, Cascade, MT 59421 We salute you, Michael & Lu Marie. Independence enriches any life, renewable energy enriches the earth. Keep us up to date on your projects - Kathleen Ram Pump Dear HP, I read with interest the article in HP #23 on the high lifter pump. I agree that in many applications this pump is the best way to go. However, in the list of advantages there are some not always true statements. While in some situations the high lifter would be more efficient than a hydraulic ram, this would not be the case if the ram were installed correctly. I operated a business here in Missouri building, servicing and installing hydraulic rams for 10 years and am known as the local ram expert. We have used hydraulic rams to pump our water since 1979 and still do. The hydraulic ram water pump was invented in the late 1600s and is still used, mostly in developing countries where power is not available. In 1979 I attended a workshop on hydraulic rams at New Life Farm in Drury, Missouri where we designed, built, and tested over 10 different hydraulic rams. The efficiency of most rams we built was over 80%, with one model having an efficiency of 95%! The efficiency was measured by measuring the amount of water used to operate the rams times the feet of fall used to operate the ram to give us the number of foot pounds of water used. We then measured the pounds of water delivered times the height the water was pumped to give us the foot pounds of water pumped. Dividing the foot pounds delivered by the foot pounds used actual efficiency was obtained. For example, one test used 40 pounds of water per minute with a supply head of 6 feet for 40*6=240 foot pounds of water. The pump delivered 5 pounds of water to a height of 40 feet for 5*40=200 foot pounds of water. The efficiency was in this case 200/240=83% efficient. Most pumps scored 90% or better. The only one less than 80% was the plastic pump published many years ago in Mother Earth News which didn't work at all, probably due to poor construction or materials. I used the design we decided on as the best for 12 months here at home using 15 feet of head pumping 75 feet before the impetus valve required replacement. Using the figures in the article to calculate the efficiency of the high lifter as follows. Six gallons per minute and 26 feet of head gives 6*26=156 gallon feet of water used. Delivered is .166 gallons per minute and 132 + 26 = 158 feet height gives .166*158=26 gallons feet of water delivered. The efficiency for this application is therefore 26/156=17% efficient. I definitely do not want to imply that the high lifter is not a good pump. I can see that in many cases it would be a better pump than a hydraulic ram. It does have many other advantages as listed in the article. An efficiency of 17% is actually very good for this type of pump. The efficiency of hydraulic rams can be this low or lower if improperly installed or if there is something wrong with the ram. If anyone has trouble with their ram feel free to call me at 417-683-3570. Written responses please include a stamped self-addressed envelope and $10 per response. For plans to build a ram from metal pipe fittings send $5. Dave Luckenbach, Rt 1 Box 393, Ava, MO 65608 Worldwide PVs This is a terrific magazine. I first heard about you folks through Real Goods and I am glad I subscribed. As a top shelf magazine, first class mailing is called for. Here at Maryknoll I purchase alternative energy commodities for our personnel overseas, especially in Tanzania where we have several photovoltaic Missions where electricity is needed for various usages such as running medical clinics. Here at Maryknoll my involvement at the present time is with the Burns Sun Ovens. This started out when I became interested in this type of project through trying out some of the VITA materials that were available many years ago when I was assigned to Bolivia. There my first experience was with a parabolic type of cooker that didn't work too well, but eventually we were able to bake some cakes in it. Keep up all the good work you are doing. Brother Theodore Flick, Maryknoll Fathers, POB 167, Maryknoll, NY 10545 I have never tried a parabolic cooker but apparently it takes some finesse to use them. I am so enamored of the reflector style sun ovens that I haven't really pursued parabolic cooker research or testing. Although I still use my two cardboard Sunstar cookers I received a Burns Sun Oven for my birthday. I love it. It's a nice tight, light efficient little unit. The benefits of solar cooking in under developed nations are obvious. Once you cook with the sun here in the States, the benefits of this cooking style will become obvious too. Good luck, good life and to borrow your own words, Brother, Keep up all the good work you are doing. Kathleen. PV Performance Dear Home Power Types, re: your PV performance article (HP24). An impressive compilation of data. After looking at it a while it occurred to me that it wasn't telling me much about what I should purchase. If the specs that you focused on are typical of what manufacturers provide I would suggest that they are woefully deficient in the face of the real world applications. I have two suggestions: 1) A minimum derived quantity would be a power vs output voltage curve as this would allow for some comparative analysis if I know the operating voltage range of my batteries. 2) The obvious and most difficult to get would be the total A-H produced by an array as its illumination source is rotated from the edge on the right angle with the light source tracing through this 90¡ at a fixed rate. It seems to me that there is a big question of array performance not only at typical real world ambient but also at angles of incidence characteristic of real world applications. re: Your article on instrumentation (#24). Too much data can easily bury a neophyte to the point of total confusion. As an occasional troubleshooter, I would like to add my take on data. When troubleshooting a malfunctioning system, historical data from known good times can be invaluable. Perhaps you could provide readers with some insight into the important bits of information that should be collected on a regular basis that would give them a "minimum system profile" to work with when troubleshooting. What data points do you rely on when troubleshooting? Regards, Ken Robart, Address Witheld Hello, Ken. We supplied the voltage versus current curves for the modules because space didn't permit also printing the voltage versus power curves. Voltage is only really important in a module if there isn't enough to recharge the battery. Since most folks use static arrays, this is what we tested. PV output is roughly linear with angle of incidence. We took the measurements when the sun was perpendicular to the modules so that we would have the minimum 100 mW./cm2 solar insolation. We want to place computerized Ampere-hour instrumentation on the test array for a long period of time. Only problem is coming up with the some $7,000 worth of dedicated hardware for the project. If we can talk the industry or whomever into helping out, then we will be conducting long term Ampere-hour testing of PV modules. We need a Fluke Hydra and an extra Mac to ride herd on it. Sorry to have buried you in info. Give it a read through in several months and I'll bet it makes more sense because you have learned more. Array current is the one thing to watch on a regular basis. Folks who do this will know immediately when something goes wrong in the PV circuit. Constant monitoring of array current will also give the user a good idea of array power fluctuation caused by high air temperatures. Richard. Dome Home Hello! As an AE novice, most of what I know about this field has come from reading HPM. My special interests are PV systems and electric cars. A friend and I are building a 1600 + foot geodesic dome - it's built on a raised foundation and is currently little more than an enclosed shell: has shingles, siding, windows and doors, but little else. Also have a 2-car dome garage. We live on a desert mesa (about 3500 ft) and thus far have experienced 98% sunshine. PV seems to be the sensible way to go! HPM is much appreciated! Dorothy L. Walker, 61870 Aberdeen Dr, Joshua Tree, CA 92252 Good luck on your endeavor Dorothy, it sure sounds like you're in the right place for PVs and a dome. It sounds like a great site, although I wonder about water and gardening opportunities. - Kathleen Hey, it's great to hear from dome builders. Karen and I built a 26 foot diameter, two frequency breakdown, octahedral dome here on Agate Flat in September 1970. We used a connector kit from the DynaDome folks and it went together in thirteen days with nothing but hand- powered tools. We affectionately call it the "DynaDump". After years of trying to stop all the leaks, we finally roll-roofed the puppy and gave it to Oozie, Karen's horse, as a barn. We learned several things about dome building. Domes do not tolerate funky carpentry, so make and use accurate jigs for all the parts. Domes are all roof, so if it can leak, then it most certainly will leak. Richard. Vintage Vacuum Dear Kathleen & Co., I own a Kirby 509, which I bought, rebuilt, at an L.A. swapmeet in 1978. I have never seen another upright that can out-perform or outlast this one. When I moved into my (rented) solar/12-volt home a few years ago, I thought I would have to do without it, or save for a generator. The house came with a Tripplite PV-550 inverter, and I was pleased to discover that the Kirby works quite well on its "juice". Because of the square-wave output of the inverter, I usually run the vacuum for only a few minutes at a time, so it won't heat up. Like the 505, this is a 3-amp machine, heavy, but small. I like the old fashioned cloth bag (always hated the wasteful, paper ones), and the hatch on the bottom makes it easy to empty. Until I read your article in HP 23, I was not aware that it was still possible to get accessories. I am contacting the Sandersons for more information on this. Thank you, Kathleen for sharing this information. On another track; it was a joy to connect with members of the HP crew at Seer'91. We even managed to fulfill a long-time ambition of mine, getting Richard and AEE's David Katz together for an interview for KMUD's Environment Show. As expected, the interview was quite lively and very well received. May the SPARK be with you! Arlo Hagler, POB 1194, Redway, CA 95560 Thanks, Arlo. I like to hear about information from HP being utilized. I just love my Kirby (3 amp, 505), it performs flawlessy. Yes, SEER '91' was really great. It was a treat to be there, see you next year. - Kathleen How about a Solar Traveler Network? "Long Distance Solar Voyager Network". X$ fee to join. Covers: Printing and postage for Solar Traveler newsletter. (Twice yearly or whatever) B) Advertising C) Solar Traveler Solar Transport Fest? (Sunfest?) A network of solar vehicle owners who enjoy long distance travelling and would like to use their sun transportation to do so. Each member would receive a list of all other members and a map showing town locations of other members. Any member would be welcome at a fellow member's home to lodge and refuel for free or a small fee. All arrangements would be made prior to departing for journey concerning number of people if more than one, cost if any, and other details of that sort. What say? Other ideas anyone? For now, Love, Matheau David Moore, Bubela Press, 124 9th Ave., Pitman, NJ 08071 How about it Solar EV folks? If you're interested in setting up a Solar Travelers Network, then drop Matheau a line. Richard. Cabin Conversion We have a cabin in northern New Hampshire. We decided in the beginning that we would not hook up to the grid - that was 18 years ago. The first construction was done totally with hand tools. Then we bought a generator with 110 vac and a 12 VDC output. It bothered me that so much energy was going to waste while using small power tools. Next step was to buy a deep cycle marine battery and a couple of fluorescent lamps. Then we hooked up the radio/cassette player (no more throw away batteries). I was just getting into a PV system when I read about Home Power in the Whole Earth Ecolog and began my subscription with issue #21. The Code Corner article was most helpful and prevented me from making mistakes that could have been expensive not to mention dangerous. We have just completed installation of a system following John Wiles article. We are pleased with its operation. Many thanks for this and many other fine articles. Would like to see more articles devoted to small vacation type situations and 12 v DC refrigeration (small). Richard A Kenyon, 37 Danielson Pike, Foster, RI 02825 Thanks for the flowers, Richard. We will keep on with articles about efficient and low-cost refrigeration. Richard Help! Several months ago, I received a letter from a fellow who had devised a tracking mechanism which was positioned by a clock and some kind of little magnetic actuator. This man sketched a mechanical diagram and a schematic, both on separate pages. Well, I have lost the schematic, which also has his name and address! Help! If you're out there, I have begun to collect some of the parts, such as the 12v gearmotor, but I'm adrift w/out the rest of your info. Please help me out, and be so kind as to send me your drawings again. I will be forever grateful. Bill Barmettler, POB 1462, Chemalis, WA 98532 Solar Pellet Stove As my latest project I have installed a pellet stove operated on solar power. It appears on a 3 day test that the system will work great, but will have to see what happens during long foggy periods in the winter months. I am using 2 Trojan L-16 batteries, a 700w PowerStar inverter, a Todd 75 amp charger and 6 used PV panels. The PV panels are 1 Tri-lam from Real Goods, 3 are M-51s from Alternative Energy Engineering. Used recycled PVs to try to save money on system. Putting out about 11 amps. How do you get a hold of Windy Dankoff to answer a letter. I have written twice and got no answer in about three months. I need lightning suppressors. I really like your magazine. Gerald Ames, POB 749, Okanogan, WA 98840 Keep us advised on your stove project, Gerald, it sounds very interesting. Windy Dankoff's phone number is ¥ 505-793-9699. Small business operators often have a difficult time answering letters. There just seems to be no time for that along with all the other duties involved. It is usually best to call the person, then if you catch them, you can get your information right away and ask any questions that may come up. - Kathleen Eureka I can't tell you just how "juiced" I was when I picked up an issue of your magazine at a local bookstore and read 1/4 of it before I could even get out of the store. My finding this magazine was a complete fluke, since I went in to peruse organic gardening literature, but what a difference Home Power has made in my thinking. I live in the country in Central Illinois, where wind and solar resources are plentiful, and electricity is expensive. After thinking for a couple years about small or large alternative energy schemes, it's a shot in the arm to know that "there must be somebody out there doing this", and now I have a wonderful resource in your magazine. Already making plans. Thanks for the great articles which sent me back to my Physics books to freshen up and gear up for "off-grid" potential. Sincerely, Ginny Dahms, Rt 1 Box 88, Bement, IL 61813 Yes, Ginny, we are out here and getting stronger all the time. You have joined some people surfing on a wave of sensibility and conscience. The information is spreading across the world. We have subscribers on all eight continents. Welcome. - Kathleen Illuminating Dear Home Power, I wholeheartedly agree with Dan Freeman's call for RE to be used for more than just bare essentials (#25). And I do not believe that this contradicts Henry David Thoreau's maxim: "That man is richest whose pleasures are the cheapest." But Dan's examples are terrible. Please consider your luxuries with great care. For example, "lighting up the outside of your home". We should learn to respect and welcome the sanctity of the darkness of nighttime. To unnecessarily defile its character with outdoor lights is simply unconscionable. The heart breaking conflict between the environmental community and astronomers over the construction of an observatory on Arizona's Mount Graham is an example of our lack of respect for the night. There are so very few places of high altitude left that are not affected by light pollution. Turn off those outside lights! I share Bill Barmettler's view (same issue) that most of us will make a gradual transition to RE while staying connected to the grid and so I encourage more articles about this approach. As I see it, it is a task of drawing RE supply and your demand together until they meet. And yes indeed you should select some luxury items to be your first users of RE; to show to your friends and neighbors. Like your stereo. But do keep it turned low, or some of those neighbors might train air rifles on your PV panels. Sincerely yours, Hank Bruse, 235 Travis Dr., Wisconsin Rapids, WI 54494 I learned maybe two things from surviving the '60s. One, no individual has the right to impress his will upon another. Two, be careful what you want because you just might get it. Richard. DHW Dear Richard Perez and Home Power Folks, Thanks for the info on running computers off grid, and for starting my subscription to your excellent magazine. I received HP#25, and looked at Tom Lane's article on active solar domestic hot water (DHW) systems. I also saw bill Battagins's article about passive solar DHW in HP #22. These are great articles that provide valuable hands-on construction details. However, while Lane's article is well-suited for solar-aware contractors, readers that are just learning about solar energy could be confused by a paragraph titled "Thermosyphons" into thinking that passive thermosyphon DHW systems are grossly inefficient and only partially heat up water tanks no matter how they are plumbed, as one reader I showed the article thought, when in fact passive solar DHW systems can be efficient and effectively heat up entire water tanks. Lane was not writing about passive systems, but rather about an active system with a passive component: he was saying that external heat exchangers should be avoided in active systems because they require two pumps instead of one, and that relying on passive thermosyphon currents instead of a second pump would greatly reduce efficiency and only heat up part of the water tank. Maybe the paragraph could have been titled "Avoid External Heat Exchangers". Lane recommends water tanks with internal heat exchangers that can be purchased individually -- a great idea, and as far I know those are probably only available for active (not passive) solar DHW systems. (The difference between active and passive solar DHW systems is that active systems use pumps, and passive systems do not.) Some prefabricated passive systems do have water storage tanks with internal heat exchangers, but are only available as complete systems, including the collector. Can such passive tanks be purchased separately? Tom Lane is a Gainesville, Florida contractor. He writes like there is no such thing as passive solar DHW systems, and in Northern Florida there probably isn't. I haven't been back there since I was an architecture and engineering student in Gainesville in the mid 1970s, when the only solar panels I saw in Northern Florida were at a state funded solar demo house. That demo house was where I first learned about passive solar DHW, by watching the classic simple open loop thermosyphon drain-down system in the backyard. I guess those must not have caught on in Northern Florida. Heck, you gotta be a farmer to remember to drain it down (other folks don't watch the weather so closely), and those systems haven't caught on in other U.S. cities either, where most solar DHW systems now being installed are as Lane describes (contractor-installed closed loop systems with PV- powered pump) or are prefab passive or active systems, many of which were displayed at SEER '91. Bill Battagin's article on passive solar DHW responsibly covers only closed-loop systems, since those generally provide the most reliable freeze protection. In a closed loop system, the water to be heated does not actually pass through the collector. Instead, a secondary fluid (with anti-freeze and anti-corrosion properties) is circulated through the collector. The secondary fluid transfers its solar heat to your actual water through a heat exchanger tank (in Battagin's design, a home-made combination water storage tank with internal heat exchanger). Besides freeze protection, closed loop systems reduce scaling inside the collector if scaling is a problem with your water system, since the water does not come in contact with the collector. Passive open loop systems, on the other hand, send the potable water through the solar collector. If the water in the collector stops flowing and freezes, even just for one night, serious damage to the collector will occur. To prevent such damage, one option is to drain the collector seasonally or on freezing nights. If you have frost sensitive crops that must be covered with cold frames or cloches, put them near the collector, so you remember to drain it when you are closing the cold frames. Another option is to put the bare collector (without its outdoor housing) in a climate protected area, such as in a greenhouse (this can also be done with batch collectors). Another option is to circulate warm water from the tank through the collector on freezing nights. This happens naturally in passive systems if the check valve is bypassed, but cools down the tank, should be done with backup heating disconnected, and is only suitable in mild climates or in sites that are drained down seasonally, and/or in locations with most water demand late in the day, and/or as a preheat for a gas water heater. And batch collectors (where the tank is the collector) also make good passive preheat systems. For many passive solar DHW users, Bill Battagins's closed-loop system may be the answer. But building his home-made heat exchanger could be tricky (requiring the use of acid, protective clothing, etc.), and open loop systems can provide freeze protection in some cases, eliminating the need to build that heat-exchanger. Here in Tucson, where I live Temporarily, almost any kind of passive design works, including a friend's seasonally drained-down open loop system with floor-level tank below the roof collector -- a passive system that wouldn't work in other U.S. climates. I work on solar DHW systems occasionally, and am interested in learning more about them, especially passive systems in climates that are cooler than Tucson. Thanks for covering solar water heating, an important technology that can be widely used on and off the utility grid. Sincerely, Carlos Portela, POB 43975, Tucson, AZ 85733 Salute, Carlos. The problem with all of us is that we see only part of a problem. We arrive at what works for ourselves and feel we have discovered the truth. We what we have discovered is part of the truth, but certainly it isn't all of the truth. We human are provincial animals and only by sharing with others, who have different experiences, can we even hope to become more aware. Richard. The Salad Days Happy 25th, Congrats for staying the course, on track. I appreciate your consistent approach, without becoming overly Green or Technical. How to get the attention of the masses and open their eyes might be a future goal. (Where are they going to get the juice to charge all those electric cars of the future anyway?) Thumbs up to Mr. Sagrillo and Mr. Perez for telling the dogmatics to "ground this". My house sticks out on a windswept hillside. The aluminum roof has always seemed like a prime target for lightning. Mr. Sagrillo's past article has reduced my fears by raising understanding. I believe windswept is the key. When walking the local Pinion and Juniper forest, the lightning burned trees are ALWAYS down in the draws, not in the high spots. I will continue to float my PV system, knock on wood, and hope writing this doesn't spoil 25 years of luck. Mr. Perez's article on PV Basics is the one I have been waiting for. Some of the systems illustrated in the past show more dollars than sense. (It must be nice.) My experience is you don't need all that power. During the hard years (that's pre-PV) the only things the generator was used for were vacuum cleaning and skill saw or drilling. After 5 yrs. of being a 12v purist, and coddling my batteries, (skim the cream method ala' Joel Davidson in The Solar Electric Home) I have begun to realize how durable this kind of system is. At first lights and entertainment seemed the goal, but being able to move water rather than pouring it from containers has been the true improvement to the quality of life. Now that inverted power is on line, SunFrost is frosting, and the excess power is being dumped to the hot water tank. I guess its time to go back to working on my old cars. But don't cancel my subscription. Thanks for the information, and competition among advertisers. P.S. Issue #23, page 4, From Us To You, most profound. May the Force of the Source be with you. Chris Byers, Address Witheld Thanks, Chris. You know there is always room for education and improvement. Right now there are many advances being made in Renewable Energy. The near future will bring many more. Do your old cars happen to be electric? Maybe your new one will be. - Kathleen DHW Survivor Dear Home Power, Where have I been all your life? A friend recently loaned me his collection of every issue of your magazine. I was impressed and pleased to see a viable publication of this type. I'm a survivor of the great commercial solar DHW wave of the 80s. I've been a solar installer/technician since the late 70s and a solar contractor since the mid 80s. I entered this field with a concerned interest in renewable energy sources and such concepts as appropriate technology and decentralized power. The last few years have found me submerged in the task of patching up many overpriced, maintenance-intensive, "user unfriendly" solar DHW systems. Most were sold and purchased on the basis of tax incentives more than environmental concerns. The concept of simplicity of design - a high priority in my opinion - was seldom acknowledged. The redeeming value of all this was depriving the hungry power grid of a few meals. Enough said about the past. I'm grateful for what I learned in that era and I'm glad to bless it and move on. I'm delighted to discover Home Power, a source of information as well as inspiration. I especially enjoy reading about solar DHW systems such as Bill Battagin's Glycol Thermosyphon System ( HP #22) and the Copper Cricket (HP #8 & #21). Long live the K.I.S.S. principle! I look forward to seeing more "appropriate" solar DHW designs in future issues. Enclosed is my subscription. I hope to renew it many times. Steve Shewmake, 10607 Bragg Ave, Grass Valley, CA 95945 Hi, Steve. My favorite quote is, "Parts left out cost nothing and cause no service problems." Richard. Back Issues The printing of your cumulative index in issue #24 was both welcome and tantalizing. Since I "discovered" your fine magazine too late to order a complete set of back issues, I could only wonder about what I had missed. In just one issue (#4) there are references to articles in issues 1, 3 and 5. I feel like someone with only some volumes of encyclopedia. I have a PC with modem and did see mention of availability in electronic form, but didn't understand all the details. I would gladly pay the cost of duplicating, postage, handling, etc. to get the information in issues 1, 3, 5, 6, and 7. Libraries in this area do not subscribe or keep back issues of this type of publication. Thank you for your time. Thomas E. Cannard, 309 Maryland Ave., Havertown, PA 19083 INSERT HP COMPUTER NETWORK DATA. Dream Delayed Dear Home Power Folks, Greetings and happy September! The primary purpose of this letter is to say Hi and Thanks for all the great info. I am always glad to see HP show up and always sad to finish the last page. Our original plan was to build a solar powered home in Western Washington this spring. The plans of mice and men are so often interrupted by just about anything. A unique job opportunity has placed us 2900 miles east of our 5 acres, and two years away from our dream. The dream was hard to walk away from even if it was only for two years. We have been interested in solar power for many years and had intended to look into using it on our new home. The local power company came to measure the distance to the nearest power and give us an estimate. Wow!! If we hadn't been convinced before we sure got that way quickly. The price tag for the power line and transformer was ultimately over 20,000 dollars. If that wasn't enough, while we were paying the $20,000 they would send us our regular power bill. Our first contact with solar powered people was in Bremerton WA. Steve and Lisa Taylor of Steamco Solar lead us out of the darkness and literally into the world of sunlight. They are nice folks to do business with and we hope they are there to help us when we finally get back to build. In the meantime, we suffer under the heavy hand of the local power company. Thanks to Home Power we can keep up with what's going on. So until the two years are over we will keep learning through a really great magazine. You are doing much good for America, please keep it up. Yours in Sunlight, Bill & Roseanne Newton, 3062 Winter Pine Ct., Fairfax, VA 22031 Think of it this way, Roseanne & Bill. Now you'll have two more years of reading Home Power and fine tuning the RE plans for that dream home. In the mean time, invest in some compact fluorescents to help lower your current utility bill. When you leave take them with you for your new home. You'll get back ready and raring to go. Keep the Faith. Dreams do come true. - Kathleen Underground Garden Dear Richard, Karen and Group, The Schatz Hydrogen project (HP April/May 91) is of particular interest to me. With a unit of the proper size this unit could make a person almost 100% independent of the greedy Mattoids who are hell bent on enslaving us. With this unit it would be quite easy to adapt all excess energy to growing ones own food in a perfect man made environment. This would certainly make the whole process cost effective. Martha and I did quite a lot of research on "Geni-Phonics" farming prior to a devastating fire that wiped us (and all our notes) out in 1976. This is a process of growing FOOD products in a totally involved man made climate. Our research included a project that was conducted in Alaska by a fellow from the U. of Oregon: Another person from G.E. and a Dr. Thomas from the U. of Alaska. Dr. Thomas was the only one willing to give us any info at all on this type of farming. It was quite encouraging I might add. One of the greatest benefits of this type of farming would be the quality and quantity of food produced in a confined atmosphere. (Up to 32 times field production). I do remember that he said at $.50 per pound his unit (including 2 ft.aisleways) produced at a rate of $2.50 to $3.50 per sq. ft. per season. They were using a cinder block building with 14' ceilings with 400 M.V. lights that could be adjusted for height. Their crops were the normal garden variety. Think what would happen here with free energy!! Being in the building industry for 42 years - it would be very simple to put a unit like this underground where you would only need from 20¡ to 30¡ rise in temperature to grow tropical crops in a colder climate. And to make a comfortable living as a family group producing for others. We are too old to do the physical part of this but the concept of the good it could do for the people is mind boggling. (Just eating the food for health alone would be a great payoff). My spelling isn't too good anymore - too much formaldehyde. Thanks for listening - Ideas from communication too! Our best to you folks, Harry & Martha Scott, POB 1265, Walsenburg, CO 81089 ATTENTION, PLEASE PLACE THE ANSWER HERE. THANK-YOU.