The PV/Engine System that Produces Home Power Magazine Richard & Karen Perez Many have asked about the energy system produces this magazine. Well, I've been hesitant about writing about our system. It is less than optimum for our needs. It wasn't really planned, it just grew. But, here it goesÐÐ warts and allÉ System Location We are located on a plateau, called Agate Flat, in the Siskiyou Mountains of SW Oregon. At an altitude of 3,300 feet, we are dwarfed by the 6,000+ ridge of mountains NE of us. This site was a lakebed where mastodons once lunched on lush grasses at the end the last ice age. We are not the first humans to live here. We have discovered stone tools and arrowheads here that date back over 2,000 years. If you want to locate us on a map, our coordinates are 42¡ 01' 02" North and 122¡ 23' 19" West. The nearest paved roads are 8 and 11 miles away. Unimproved dirt tracks run everywhere; it is common to be "snowed-in" or "mudded-in" during the winter. After several days of rain, the ground's consistency resembles pudding. This sticky mud coats vehicle tires and makes driving difficult. On a good day, the nearest town is about 1.5 hours away. On a bad day, we don't even make it to the paved road. We walk home returning to the stuck truck in the morning with jacks, shovels and a comealong. We are 8.5 mi. from the nearest commercial power hookup. At a going rate of $5.25 per foot, this amounts to around $235,000. The irony is that there are two 60kV+ power lines within 3/4 of a mile of this location. The power company got a good chuckle out of my suggestion of a substation. From the very beginning we realized if we wanted electricity, then we had to make our own. The building where we produce Home Power Magazine is a two story, 16 ft. by 16 ft. "Plywood Palace". It uses passive solar hot air for heating, backed up by a wood stove. Our friends say this building exists only to support the 9 radio antennas growing on its exterior. INSERT PHOTOS OF PLYWOOD PALACE System History The electrical power system here was not planned, it grew. And in 18 years of growth we made many mistakes. This article is as much about what not to do as what worked. We learned these lessons the hard way because information wasn't available to help us. We started using electricity the first day we arrived. We powered a small 12 VDC cassette recorder/player from the battery in our truck. This arrangement provided music, while we used kerosene lamps for lighting. We had a lot of romantic notions about country living. For example, we planned to cut all our firewood using hand saws. We cut for 2 months when it became obvious that we couldn't cut enough wood before winter. Fortunately a neighbor lent us a chainsaw and we didn't freeze our first winter. By 1976 we had developed a rudimentary stand-alone electrical system. It employed a 100 Amp-hr car battery and a home made engine/12 VDC charger. The DC charger used a 3.5 HP Tecumseh horizontal shaft gas engine driving a 35 Amp Delco car alternator via a pulley/belt arrangement. We learned several valuable facts from this system. One, car batteries don't last very long (less than 2 years) in deep cycle service. Two, inexpensive gas engines have short lifetimes (about 500 to 1,000 hours of operation). Since we were putting over 1,000 hours on the DC powerplant yearly, we were using up an engine every year. With power production on site, our electrical consumption soared. We were using about 300 Watt-hours daily. We added 12 VDC car tail lights, several radios including Ham & CB units, and a 5" B&W TV. Even with the increased utility of the system, we were far from satisfied. The entire system depended on gasoline as power input. We hauled over $30. worth of gas from town monthly. The generator was noisy & required constant maintenance. Electricity Requirements Here is a description of our system as it exists now. We use electricity only when & where necessary. When we are finished using an appliance we turn it off. Our total electrical consumption now averages about 1,130 Watt-hours per day. This is about 10% of the energy consumed by the average US household daily. This is a daily AVERAGE. We often "binge" on electricity. Some days we use less than our average, while on others (like during magazine production) we use over twice as much as our daily average. Just before Home Power goes to press, both computers and lights are running all night. Inverter Powered Appliances We use about 660 W-hrs/day as 120 vac from our inverter. The majority (over 50% of our total consumption) of this energy is consumed by our two Macintosh computers and their printer. The remainder of the 120 vac is consumed by various motorized household appliances. 12 VDC powered appliances We use about 480 W-hrs/day as 12 VDC directly from the batteries. Our system grew up when efficient inverters that lasted where a fantasy. As such, we have wired the "Plywood Palace" extensively for 12 VDC usage, and have accumulated many specialized DC appliances. The major consumer of 12 VDC is a 28 Watt (measured by us) fluorescent light made by the Solar Retrofit Consortium (see their Mercantile ad in this issue). This light is on the ceiling of our main work room and operates an average of 4 hours daily. Before we had this fluorescent we used several incandescent car tail lights. Changing to fluorescent lights significantly reduced our power consumption. For a report on this fluorescent see our "Things that Work!" review of it in Home Power #4. We power a number of electronic devices directly from our batteries. A full duplex UHF radiotelephone, 9 inch color TV, cassette/FM stereo, 2 meter FM ham radio, HF ham radio, a nicad recharger (see Home Power #5), and an electronic field fence charger are some of the specialized 12 VDC appliances. Below is a chart of our appliances' power consumption. INSERT CHART System Components The hardware in our system reflects its organic growth. If we were to specify this system today, it would be very different. We used what we hadÉ Power Source- Photovoltaics The main input to our system is 3 Kyocera PV modules. We now use two 48 W and one 59 W module. We purchased the 59 W module to test its performance against the lower voltage 48 W module. The modules are made of the same PV cells, but differ in number of series PV cells. Our experience shows that the 48 Watt modules are more cost effective in 12 VDC systems such as ours. For a discussion of the relative merits of the different sized modules please see Home Power #3, page 9. INSERT PV ARRAY PHOTO We are now about 70% solar powered. We (with the extensive help from George Patterson of Santa Rosa, CA) installed a cumulative Ampere-hour meter on the PV array. Our PV array of 3 modules produces an maximum of 63 Amp-hrs daily. Currently we are not using any regulation on the array. This is possible because the array's output is less than our average consumption and overcharging the batteries via the PVs just doesn't happen. When we add more PV modules, then we will have to add regulation to keep from overcharging the batteries. Due to our altitude & clear skys, our PV modules outperform Kyocera's specifications. The PV array has sunshine from to dawn to about 4 PM daily. We have been keeping records of solar insolation at our site since 1985. Our records indicate an average of 242 full sun days yearly. This data is interesting when compared to the US Weather Bureau's records in our area. The official records show much lower solar insolation. Consider where the solar insolation data for your neighborhood is taken. It is most often at a site that is convenient for the weather bureau. If you are at a higher altitude, then there is less atmosphere to absorb the sunlight, and your solar insolation may be greater than the official figures. Power Source- Engine/12 VDC Alternator When it's cloudy, or when we need extra power, we fall back on our gasoline generator. This generator uses a 5 HP, single cylinder, Honda engine driving a 70 Amp Chrysler automotive alternator. The engine is coupled to the alternator via a 6 in. pulley on the engine, a 1/2 in. Vee belt, and the stock alternator pulley. A Mark VI Field Controller regulates both the amperage output of the alternator and its maximum voltage output. For a complete discussion, with photos, of this engine/generator & its control system see Home Power #2, pgs 23-26. Before we had PVs, this generator was our only power input. We have used a variety of engines and the Honda engines are the best. The one on our generator now has operated for 7,343 hours (we have an hour meter). The only failure was in its ignition system. We made an electronic battery/coil ignition to replace the stock magneto (see the engine/generator article in this issue). Our Honda still doesn't consume ANY oil between changes. With the 3 PV modules, we are running our engine about 980 hours yearly. Most of this occurs in the winter. In the summer we may go for over a month without using the generator at all. Operation of the engine/generator now costs us about $19 a month. Without the PVs, we would be running our engine about 2,000 hours per year, and spending some $40. per month on its operation. The addition of 2 more PV modules will reduce our engine/generator operating time to less than 475 hours a year. And you can believe we are saving our bucks for these additional PV modules. Energy Storage- Batteries In 1980 we purchased 2 Trojan L-16W batteries. We are still using this battery pack, which has a capacity of 350 Amp-hrs at 12 VDC. This pack gives us about 3 days of energy storage. The energy supplied by the PVs extends the average storage period to almost 6 days. With 5 PVs in our array the average storage in this battery would be 11 days. We need more battery capacity in our system. The addition of 2 or 4 more L-16Ws would be cost effective. It would reduce our generator operating time, saving us money. We have not added more batteries because our batteries are so old. In our experience, it is not effective to assemble packs of dissimilar batteries. Age and size are such dissimilarities. An efficient battery pack should be composed only of cells that are of the same type, size and age. Batteries that differ in age by over two years should not be assembled into packs, even if they are of the same type and capacity. With 8 years of service on the pack, we should get another 2 years use before replacing it. This expected 10 year lifetime reflects very careful cycling and maintenance. We NEVER withdraw more than 80% of the pack's energy. An advantage of the engine/generator is we can recharge our pack at will. We don't let the batteries languish at low states of charge; this courts sulphation and premature cell failure. Use only DISTILLED WATER to replace lost electrolyte. We keep our batteries and their electrical connections clean. The thin film of acid that collects on the batteries is an electrical conductor. Since the L-16s have external interÐcell connections, this electrolyte forms short circuits between the cells. This increases self-discharge, and state of charge inequalities between the cells. We are careful to do regular equalizing charges. About once a month, we completely recharge our batteries and then give them a controlled overcharge at the C/20 rate for at least six hours. A C/20 rate for our 350 Amp-hr pack is 17.5 Amps (350 Amp-hrs/20 hrs = 17.5 Amps). The secrets of battery longevity are: 1) proper cycling, 2) regular equalizing charges, & 3) regular maintenance. Energy Conversion- Inverter Our first Macintosh computer (1984) led us to install an inverter. Over the years, we have used many different inverters. Some self-destructed rapidly for no apparent reason, and some lasted. The inverter is a critical link in an RE system. It allows the low voltage PV energy to be used as 120 vac. Two inverters we have used are worthy of mention- the Trace 1512 (now the 2012) and Heliotrope PSTT inverter. These inverters not only work and are very efficient, but they LAST. We are currently using a Heliotrope WF 12-2300 inverter. It powers our computer equipment beautifully- no additional heat is generated within the computer's power supplies.. INSERT HELIOTROPE INVERTER & BATTERY PHOTO Our Heliotrope is a powerful unit, with output power of 2,300 watts continuous, surge to over 6,000 watts. The WF 12-2300 has enough power that we haven't used our 120 vac powerplant for months. This inverter runs all of our shop tools, such as our circular saw, drills, soldering irons and our monster, 1/2 HP split-phase bench grinder. I doubt that we will outgrow this inverter within the next few years. For a discussion of the Heliotrope inverter, please see Home Power #3, pgs 29-31. For info on the Trace inverter, please see Home Power #2, pgs 29-30. The inverter is wired to our batteries via short, 0 gauge, copper cables with homemade, soldered, copper connectors. It is essential that any inverter have a very low resistance path to the battery's energy. On surges, a powerful inverter can draw over 500 Amperes from the batteries. Our cable ends are filled with solder to resist the inevitable corrosion involved with battery connection. See the battery article in this issue. INSERT SYSTEM DIAGRAM System Cost We have invested about $4,500 in hardware. The three PV panels cost $1,068, the Trojan L-16W batteries cost $490, the engine/generator cost about $1,100 to construct, and the Heliotrope inverter cost $1,720. All these prices include shipping to our site. This hardware cost info is presented as a pie chart below. INSERT COST PIE If the engine/generator operating expenses are figured into our system's cost, we will spend about $6,800. to both buy and operate this system over 10 years. This power cost, right now, is $1.64 per kiloWatt-hour (kWH). While this may not look so swell when compared with our local utility's rate of 7¢ per kWH, consider the $235,000 that the power co. wants just to run the lines. The way I look at it, we've got all the electricity we need and saved some $228,000. If there were no PVs making electricity for us we could expect to pay $8,121 over 10 years to run this system, or $1.96 per kWH. With 5 PVs in our array, the 10 year cost would be $6,366, or $1.53 per kWH. If you're making your own electricity, PVs can really save you money. The graph below shows how PVs financially impact our system. INSERT BOTTOM LINE CHART Some Valuable Lessons This article is chronicle of experience, not an optimum way to design a system. We've had to learn the hard way- by making mistakes. We are still living with some of our mistakes. If you are smart, you will profit from our errors. So here are some suggestions. ¥ Plan well ahead when you design your system. Do a comprehensive, accurate, long-term estimate of your needs before you buy any system components. We were short-sighted. For example, we purchased too few batteries. This has caused us to spend much more money on generator operation. Look well ahead to your energy needs not only next year, but for at least five to ten years. ¥ Don't think twice about purchasing PVs. Money spent on PVs rapidly comes back. There is no comparison between using gasoline or sunlight as power inputs. With fossil fuels, we get noise, pollution and the way things were done. With PVs, we get silence, freedom and the way things are going to be. Let the future into your life & use the Sun's power. ¥ Don't be tempted to buy the least expensive system components. Your home power system should last for at least 10 years. System components designed with cost as their primary criteria are not going to last. Stick with equipment that has documented longevity, it will be cheaper over time, eventhough it costs more to initially buy. ¥ Seek help from experienced people when you specify & purchase your components. Details such as how many batteries, system voltage, how many PV modules, and what size inverter are critical to system efficiency and cost effectiveness. If you are in ANY doubt about the equipment you require, enlist the aid of a those with the experience necessary to specify a system that meets your needs at the minimum cost. ¥ Learn all you can about your system and how to operate it. You are your own power company. The longevity and performance of your system depends on your involvement in its operation and maintenance. You'll have no one to blame, but yourself, if the lights go out. ¥ Consider the appliances that use or will use energy in your system. In home power systems, it is ALWAYS more cost effective to purchase the most energy efficient appliances available. Appliances as RE refrigerators and fluorescent lighting will pay for themselves because of reduced power consumption. ¥ Feel good about your home power system. Through your use of renewable energy, you point the way to a clean and sane future we can all share. So give the Earth a break and support renewable energy!