Buzz, Buzz, Buzz Dear Home Power Magazine, I know you've reported on these inverters before, but I thought I'd update you on my limited, and somewhat disappointing experience, with the STATPOWER PROwatt 250 AC/DC inverter. I teach energy education courses for classroom teachers. In my two day course we spend several hours discussing solar energy and doing experiments. I put together a small portable, yet complete, PV system for demonstration and experiment. The system includes a 30 watt PV panel connected to a 40 Ah 12 volt battery. The compact battery is nestled inside a carrying case with appropriate meters attached. When I'm not in class I use the solar electricity to power my office. I carry the battery case into my office and hook up my Macintosh computer for about 3 hours of computing in the morning. Some of the equipment in my office does not like the inverter: 1) The transformer on my HP Deskwriter printer emits a barely audible but annoying buzz. 2) Every transistor radio I've tried experiences too much static or interference from the inverter, whether or not the radio was using it as it's power source. 3) The inverter also interferes with television reception and VCR playback. Sometime in the next year I plan on installing a permanent PV system for my office. Will I continue to have these problems with larger inverters? P. S. I have enclosed an Energy Education Course Description, which I offer through University Extension, Continuing Education, and to school districts. Love your magazine and wishing you the best, Mike Arenson, Air 'N' Sun Resources, 142 Darwin St, Santa Cruz, CA 95062 „ 408-423-8749 You're not the first person that I've hear from that has experienced unacceptable noise and interference from that inverter, Mike. While all inverters that I've seen and worked with emit SOME noise (especially in the AM broadcast band of transistor radios), few cause the severity of symptoms that you describe. Both my Trace 2012 and PowerStar UPG 1300 make an audible buzz in my Deskwriter transformer, but I had to get within 3 feet to hear it. It's not audible above the fan noise from my Mac IIcx CPU and it doesn't affect the printer operation at all. Either inverter will run the 19" color TV and VCR without interference. Proximity is always a problem with a high power switching supply, so try to put as much distance as possible between the inverter and your electronics when you make that permanent installation. Keep the inverter/battery leads as short as practical and twist them around each other if possible. - Bob-O Hang 12 I live 6 months/year on a small island on the Pacific coast of Mexico. Tides are about three feet. Does anyone have information or ideas on how to convert tidal or wave energy to 12 v? We now use only PV with a small generator back-up. Thanks for a great publication. Greg Plimpton, POB 14545, N. Palm Beach, FL 33408 This is an interesting question, Greg. We were all sitting around Home Power Galactic Central awhile back discussing how all power came from the sun, whether it be wind, water or solar. "Ah," someone said, "but the tides are lunar." Try George Hagerman at SeaSun Power Systems, 124 East Rosemont Ave., Alexandria, VA 22301 „ 703-549- 8067 - Kathleen One Man's Junk is... Dear Home Power Magazine, Enclosed find $20 for a 2 year subscription plus $3.50 for issue #25 which I am sure I missed by now. I also have two items I would like to comment about which follow: 1) I am a CPA and live in S E Nebraska. During tax season I am rarely home and don't have time to maintain and check a self supporting solar or wind system. What I'm interested in is a system that hooks into my present utility system and back feeds through the meter when producing more than I use and draws power when not producing enough electricity. This would eliminate batteries and a lot of maintenance. Nothing would make me happier than to receive a check back from my present utility company. What would be the best system for this? Who are the closest dealers? It must be simple as I am a novice at this. 2) Another item I am very interested in as I would think all of your AE and environmentally conscious readers would be is recycling. I never see any articles on recycling in your magazine. Maybe this is too far off the AE beaten path to be covered in your magazine. If so is there another magazine I can get to cover the subject? I am seriously thinking about getting into this commercially. I live on a farm and have plenty of room. I understand there is a company in Ireland converting all kinds of plastic into super wood. Any information you or your readers could supply me on these two subjects would be much appreciated. Keep up the good work, as I love Home Power Magazine. Kenneth T. Reese, RR #1 Box 286, Nebraska City, NE 68410 In Mike Bergey's article, "A Primer on Wind Generators", HP #22, he discusses this option under the subheading, "Being Your Own Utility Company." He Says, " The federal PURPA regulations passed in 1978 allow you to interconnect a suitable renewable energy powered generator to your house or business to reduce your consumption of utility supplied electricity." He goes on to explain how these systems work and what options are available. You can contact Mike at Bergey Windpower, Inc., 2001 Priestley Ave., Norman, OK 73069 USA Tel: 405-364-4212 Fax: 405-364-2078 As to your question on recycling, Ken, I refer you to Garbage magazine. Also Earthkeeping magazine, POB 44, Luzerne, PA 18709 „ 717-288-1567 - Kathleen Sine Language Dear Richard, My friend Anita (who helps run our software business) and I went to SEER '91 in Willits, where we volunteered to keep the lectures at the Energy Independence Hall running smoothly (I also helped assemble the solar demo home). On Industry Day, we attended the Inverter Manufacturers Panel Discussion, where part of the discussion centered on the inability of inverters to power sensitive electronic equipment such as video equipment and laser printers. This might be important to us since we are a software company that may need to run computer equipment off the grid in the future and may need to give other people advice on how to do that. The way I understood the discussion, the common inverters do not put out a smooth sine wave (from 120 VAC to -120 VAC 60 times per second), but instead put out a modified square wave, which is like a sine wave with the "stair case effect" (to borrow a computer graphics term). I do not use video equipment, but someone mentioned that modified square wave power causes interference in video pictures. I do use laser printers, and remember that some persons, including yourself, mentioned that laser printers could not operate on the modified square wave power. The inverter manufacturers said it would not be cost effective enough to develop and market sine wave inverters to the public since market demand would be minimal, but they said they would introduce new inverters that would produce a modified square wave with smoother curves (less of a stair case effect), and that these new inverters would run video equipment but not laser printers. You told the audience that would be no problem because laser printer users could switch to ink-jet printers, which I think you mentioned draw only 40 watts. We pretty much need to keep a laser printer because our customers use laser printers (to print postal barcodes on envelopes) and we need to test the software on the same kind of printers our customers use. So I suppose that If I move off the grid I'll just use a generator to run the laser printer when I develop new versions of the mailing list software and need to test it. Since most of our customers are in the San Diego area, where alternative electricity will not be implemented soon, our customers there will not need to worry about running their laser printers on inverters soon. But I'll be keeping an eye out for any available information on how to run laser printers off the grid. When I introduce our solar software, someone is bound to try to run it off the grid, so we'd like to find out more about how to run computers off the grid. Is there any source of information on that? Will you be covering that at all in Home Power magazine? (Note: I'll love your magazine even if you don't cover computers.) For example, we have a friend who asked us about running computers off the grid. He is an accountant in mid-California with a pickup truck camper. He had an old portable Compaq computer with a 20-MB hard diskŠa very common computer a few years ago, bigger than today's laptops but smaller than desktop PCs. It runs on 120 VAC and does not have any kind of batteries (it must be plugged in to run). Since he sometimes travels in his truck, he wanted to be able to run the portable Compaq from one of his two truck batteries, and to attempt to do that he purchased a small inverter from Real Goods. As he told me, the Real Goods catalog shows a picture of someone near a beach using a Mac in their car with that inverter. However, the computer refused to even boot up when he did plug it into the portable inverter. Figuring that maybe there was too much line-loss (voltage drop), he connected the inverter directly to the battery with big cables. Then he would get the computer to boot up, but it would crash (turn off, lose power) after a few minutes. He just couldn't get it to work. Recently he purchased a Goldstar laptop computer: a 386 with a 40- MB hard disk. He called Goldstar technical support to ask them if he could run the computer on the inverter, and they told him they've never tried it and that if he tries it and it causes damage to his computer the warranty will not cover that. So he has not and will not attempt to run the laptop on the inverter. I heard a rumor that those portable inverters have a real square wave (not even modified to produce a staircase effect). But I can't remember where I heard that and it might not be accurate. In any case, I hope to find out more about how to run computers on alternative energy. Sincerely, Carlos Portela, 3-D Software, POB 43975, Tucson, AZ 85733 We've had readers express good results by using a Shape Line TamerØ (available from Photron, see their ad for access) between their inverter and laser printer, Carlos. Apparently, they're a bit noisy and will reduce inverter efficiency by 20% or so, but if they do the job... It sure sounds like your accountant friend bought an inverter that was too small to handle the power requirements of his Compaq. Contrary to what most folks think, computers are some of the least fussy and easiest loads for inverters to run. That's because they don't use the 110 vac directly, but transform it down to 5VDC to run the ICs and usually +12 and -12 VDC to run the drives, etc. During the step- down process, they also filter the heck outa the input power. The filtering nearly always eliminates the "noise" on the ac line, whether it's caused by the inverter or the grid. Too bad Goldstar is afraid of what they don't know. The four Macs that are used in the direct production of HP day in and day out have never been fed anything BUT inverter power! I know of IBMs and lots of clones that digest it just fine with no problems. - Bob-O Carlos, check out HP#16, pg. 7. This article is about Home Power's system. Most of the 5 kWh we cycle daily goes down the throats of computers and peripherals. Included in this article is a detailed list of computer gear that we know works well on inverters. In general, computer gear has less problem digesting inverter power than most consumer electronics. Just like all appliances, power consumption varies widely with type. Sounds to me like your friend had a big power consumer tied to a marginal car battery. Plugging a new computer or peripheral into the inverter for the first time is alway thrilling. We keep close track on problems like with the laser printers. Filtration, like the Line Tamer, works on some lasers, but it cost money to buy the filter and it takes power to run it. These filters are mondo phantom loads, so be sure to switch them off line when they are not in active use. Meanwhile, we are happy with our Hewlett-Packard DeskWriter printers. They love inverter power and consume only 26 Watts while printing and 4 Watts on standby. They also cost about $500, which is much less than even the cheapest laser printer. As far as the quality of the DeskWriter's output, you tell me. You are reading it right now. We used a DeskWriter to print the masters for this issue. Richard. 3-in-1 Gas I really enjoy your magazine. I am just beginning to understand some of the methods of producing your own electricity environmentally safe. In beginning to set up, could a person use methane gas to run a generator? I have read somewhere where China uses methane to heat their homes, cooking, run the vehicles, etc. Am I correct in this? The lower portion of the tank was used for fertilizer, 3-in-1 purpose. William J Catlett, RR #1 Box 186, Monticello, IA 52310 Although I do not know about the Chinese use of methane you are in luck, Will. I refer you to Al Rutan's article on home methane in this issue on page 24. I hope it will enlighten you as it has me. - Kathleen Battery Box Dear Home Power, I'm two miles "from the grid" and am approaching the purchase of a small PV system from the position of a "well read, armchair, soon to be PV user". In other words, I've read Davidson's and Fowler's most recent books, pored over piles of catalogs, gone to SEE working systems, and finally feel educated enough to purchase and install my own system. My one question is how to keep my batteries at an optimum temperature, say 65”-70” F, in a house (cabin) which goes unheated for 3-5 days at a time. Utilizing solar heat is not practical for the next 1 or 2 years. My plan is to build an insulated and vented "box" for the batteries. Inside the box I'll put a light as a heat source and control it with a temperature sensitive switch. Comments? Clay Turnbull, Simpsonville Brook Rd., Acton Hill - HC 33, Townshend, VT 05353 That light bulb idea is asking for trouble, Clay. As lead-acid batteries become discharged, the electrolyte will freeze at higher temperatures. A fully charged lead-acid battery won't freeze until -60”F or so, but at 25% state of charge you're in trouble below +5”F. Totally discharged lead-acid cell are goners below +32”F. Suppose it snows the whole 5 days you are away from the cabin? The light bulb attempts to keep the batteries warm and totally discharges them in the process. The best solution would be to use alkaline (nickel-cadmium or nickel- iron) cells in your system. They will deliver full output at 32”F. They will only roll off 20-25% of capacity at below zero, and won't freeze above -55”F regardless of the state of charge. Even if alkaline cells do freeze, they are not damaged and will work fine when thawed out. Richard & Bob-O.