| | Renewable Energy - We Run from the Sun!
Energy is a force that does something. And we ask a lot from the energies available to us, especially electrical and chemical energies. The electrical energy from the AC power "grid" is obtained primarily from mined, heavily polluting, nonrenewable resources: coal, petroleum in some form, or highly refined uranium-bearing ore. A tiny portion (in the U.S.) of electrical power is supplied by renewable sources: moving water captured by hydroelectric dams turning turbine-coupled generators, moving air powering large wind turbines, sunlight energizing banks of photovoltaic (PV) panels, and geothermal heat powering steam generators.
Chemical energy is often utilized solely for its ability to produce heat, often for a terribly innefficient conversion (about 24%!) into mechanical energy (the internal combustion gasoline engine). Chemical energy for portable power, remote locations, or high volume users is usually supplied by nonrenewable petroleum in the form of natural gas, liquefied petroleum (LP), gasoline, diesel fuel, fuel oil, aviation fuel, or kerosene. Really high volume users who don't need a portable source (like electrical power plants) use coal.
A hundred years ago the scenario was quite different. Electricity, where it could be obtained, was usually from hydroelectric dams, small local steam engine generators, or, a little later, from small wind turbines. It was stored in bulky, heavy, lead-acid batteries that could be charged, discharged, and recharged many times. Chemical energy for direct heating of homes, or for conversion to mechanical energy was obtained mainly from non-renewable coal or renewable trees.
World War II was the impetus for many of the changes we see now. A huge energy appetite and the demands for massive destructive capabilities left us with an enormous civilian chemical products industry and the ability to produce electrical energy from the controlled splitting of uranium atoms. Both industries have left us with huge and ongoing waste disposal problems, neither of which has been adequately resolved. Coal mining continues to be a major polluter of water, a hazard to miners, and, even with decreased noxious emissions from planned "FutureGen" plants, its increasing use exacerbates the global warming scenario of trapped carbon dioxide in the atmosphere. The popular press, influenced no doubt by heavy-handed lobbying, is touting the "carbon neutral" benefits of nukes. But the mining and preparation of uranium fuel rods is a huge source of carbon dioxide, not to mention the water pollution and health hazards associated with uranium mining.
Roughly 76% of all electric power generation goes into building operations! That's about 44% of ALL the energy humans produce. Renewable resources that offer energy with no net CO2 increase are the only intelligent choices in our current situation. But a swelling human population practically guarantees that wise choices won't be made by politicians wanting to remain in office. Still, for those who'd like to take a stab at a semi-sustainable lifestyle, there are some updated versions of the traditional renewable energy sources.
Local electrical power production lost its battle with centralized power way back when Edison's local DC power production scenario was replaced by the Westinghouse-Tesla distributed AC power grid. The main reasons for AC power were the ability to easily transform the energy to a high voltage that could be transported long distances with lower loss, and the ability to transform it back to a safer low voltage at its point of use. Modern power conversion devices using switching transistors have made locally produced DC power much more efficient, versatile, safe, reliable, and easily obtained. DC to DC converters can transform nearly any voltage to another, either for transport or use. And sine-wave inverters can produce AC power, for conventional appliances, that's often far less "noisy" or "spiky" than grid power (if they are outfitted with on-board or retro-fitted RF filters made by their manufacturers - more on this in a bit).
The Case for Decentralized, Off-Grid Power Production:
Reasons we think that connecting a renewable power source to the Grid are A) Stupid, B) Too Costly, and C) Dangerous.
- The Grid is intended and built for power distribution, not storage.
If the Grid blacks out, so does your supply of renewable energy.
The inter-tie inverter, transformer, and line losses make it quite inefficient.
Larisa says that Grid inter-tie is like bicycling with training wheels: You don't get the real experience of renewable energy, you get accustomed to the "crutch", and you don't have full control of the process.
- The amount you have to pay for just being connected may easily exceed the payments for your excess energy.
Connecting with the Grid is an "all-or-nothing" decision in terms of equipment purchases.
You have to supply liability insurance to make sure you don't electrocute any line workers.
Grid-intertie inverters themselves are more costly, not to mention the other needed equipment.
- Connecting to a 7000-volt+ AC supply is always more dangerous than a lower-voltage AC or low-voltage DC source.
Your inverter injects health-damaging harmonic frequencies to your home wiring and your neighbor's homes.
You come to expect unlimited power, have little impetus for conservation, and the responsibility for your over-consumption, as well as others', is spread throughout the Grid instead of being yours or theirs alone.
The decentralized renewable home power system:
- Uses a recyclable storage medium on-site.
It's your insurance against black-outs.
It has extremely high efficiency: low line loss, no transformer loss, and no inverter loss for loads running on DC straight from the batteries.
It requires only a regular homeowner's insurance policy, if any.
The investment is made "up-front" with no increasingly large "power rental" costs each month.
Any inverter EMF, when you actually need to use AC loads, remains in your home and can be filtered out on-site.
You gain a better sense of your power limits and usage, and how to more effectively conserve power.
The responsibility for the total environmental cost of your system and its use lies only with you and the makers of your equipment.
Solar PV in particular is modular by nature; you can add to it or change it gradually as your needs and budget change.
Before you start to tackle a renewable power system, if you would like to know a lot more about electricity and its effects on the human body, check out our EMF Hazards page.
Our Home Power System (Photovoltaic Solar with Battery Storage - "Off Grid") A Historical Progression:
Actually, our first electrical energy system, in 1983, was an improvement on a house electrical system that was based on the battery in a 1968 VW "Bug". Our little 1950's vintage, 8-foot by 35-foot "mobile home" had standard 120-volt wiring but we were in a location nowhere near the "grid's" power lines. Our only electrical loads were a small 12-volt TV and a few 12-volt fluorescent lights. We constructed an electrical "umbilical cord" that ran from the VW's battery to our home's electrical fuse box. Running from just the Bug's battery, we managed to ration power out for a week before we would have to push-start the car and take a shopping trip 10 miles to the nearest town. This charged the battery for the next week. It also slowly destroyed a battey not designed for deep discharges. A new system was needed.
We next purchased 36 round, 4-inch, silicon solar cells from an electrical surplus store. We mounted them to an aluminum sheet using silicone cement and wired all of the cells in series. They were covered by a simple wooden frame with an acrylic cover to keep the rain off. This homemade PV panel was not terribly powerful but it worked well! We wired this through a diode to keep the power from flowing backward at night, and wired it all to a new, deep-cycle marine battery. This did a much better job of supplying our meager needs, and we still could connect the car if we had a lot of cloudy weather that precluded solar charging.
Every home power system we have used since that time simply added more loads, more jobs done using solar or wind power, and more sources of renewable power generation. So how do you decide what size your power system need to be? You probably don't want to begin where we did, but your first step may be a single PV panel hooked up to a few lights and a battery or maybe a "micro-inverter" designed to connect your PV to the power grid.
The first questions you need to ask yourself are:
- What forms of renewable energy are available for harvesting locally?
- How much energy do I really need for the various things I'm trying to accomplish?
- What form does that energy need to be in (heat, lighting, water pumping, hot water, cooking heat, etc.)?
- How can I reduce both my use of energy and, especially, my use of non-renewables?
- How can I afford this and where do I start?
Some will certainly first ask "Is this renewable stuff cost-effective?", or "What is the pay-back period?", or simply "Isn't this awfully expensive"? Of course it's expensive. You are buying you power up-front instead of "renting" it a month at a time. We went with solar energy since it was the the best for our area and our homesite, and since solar systems are "modular", you don't have to buy enough for all of your electrical needs at one time. You can add to it bit-by-bit until you are fully weaned from non-renewable sources. In our case, we started with just one little home-constructed solar panel charging the battery in our VW "Bug". We added to the system and repaced undersized parts as we added more renewably-powered loads. If you'd like more details on how to plan, build, and maintain such a system, I'd suggest reading our book, "Peoples Power Primer - Renewable Energy for the Technically Timid", found on our home page.
 This is a quick sketch I made of how the most recent version of our electrical power is wired. Power flows from the 12-panel photovoltaic (PV)array at the south side of our home in 2 discrete paths. One path, wired with two 12-volt PV panels in series, directly charges our electric tractor, and electric hybrid trikes. The highest the voltage can reach is about 41 volts, and the voltage at which the power flow is at its highest (the maximum power point, or MPP) is around 35 volts. So a 36-volt battery can be plugged directly into this wiring without a series charge controller (to limit voltage).
The other path from the PV panels goes to an Outback FlexMax-80 MPPT charge controller, regulating power from 10 PV panels wired as 5 series panels in each parallel "stack". With our 12-volt household battery bank this is all the power the controller can handle. We can switch the controller to send power either to our household batteries or to the 36-volt batteries in our electric tractor or the three 48-volt banks of batteries in our electric car.
The big inverter on the electric tractor turns 36-volt DC into 120-volt AC to run a 144-volt, 10-amp, on-board charger in the car, or we can direct-DC charge. The inverter in our home is a bit small for car charging, but it is often used for either a "float" charge or to run the car's battery heaters in the winter.
We also have a single 12-volt PV panel at the shed which can directly charge our little Toro lawnmower (to mow garden paths), or it can be switched in series with the other two panels leading to the shed. This gives us over 60 open-circuit volts for slower bulk-charging of either the tractor or car, but leaves us all 10 remaining panels for house charging. Loads of flexibility!
The following photos and discussion can all be downloaded either as a 771 KB PDF file, or as a 444KB Microsoft Word document (DOC file) if you'd like all of the included links to work.
 Power can be stored on-site using a variety of battery chemistries including the old lead-acid, deep-cycling variety, improved by better construction, lower maintenance, and longer useful life before recycling. We use four, 375 amp-hour, 6-volt batteries wired in series-parallel configuration to obtain 12 volts and 750 amp-hours. Our previous batteries were Thomas Edison's nickel-iron cells using potassium hydroxide electrolyte, manufactured in the 1920's. They were built for severe conditions and industrial use, and could be restored by simply changing electrolyte every 10 years. But we switched to lead-acid mainly because it's getting harder to find replacements for machanically damaged cells or to find additional cells. There are Chinese models made now, but the quality is not up to Edison's standards! Power that exceeds what you can economically store must be either "dumped", "blocked", or "diverted". A charge controller usually blocks excess power input. But some models allow the use of a "grid intertie", a "dump load" or a "divert load". Connecting to the grid is not our preferred choice. But the latter two are types of appliances that "burn off" excess power while doing something useful. If you burn natural gas or propane (LP) to heat water, heat your home, or cook a meal, a charge controller can automatically switch on electrical versions of these loads for you. This allows you to have enough generating power to keep up with electrical demand even on cloudy or windless days. And it gives you the option to power loads that would normally burn fuels.
 This is a 300-watt, 0.5-ohm, 12-volt air heating element made by Ohmite. Putting four of these in parallel gives you enough heat to make your own oven, which is what we have just done. We often find that our masonry stove gets our water quite hot enough without additional solar energy, and we need to either use the excess for something like baking or the controller will simply reduce our solar input electronically, "wasting" valuable sunshine. If you'd like to see the details of what we built, just check near the bottom of our "Eat Local Year-Round" page.
 Some of what is now used for home energy systems got its start in the military. This is a close-up of the water-saving battery caps we use. Since charging batteries "gas off" some hydrogen and oxygen when they're nearing full charge, various caps have been designed to catalytically recombine the gases to water (HydroCaps, for instance), or simply to condense evaporating water (like these), in systems that don't heavily overcharge. This technology was originally used in WWII submarines which surfaced to quickly diesel-charge their batteries and generated lots of explosive gases in the process.
 We also use a device designed for the military called a "desulfator". It uses a tiny bit of battery power to send a small high-frequency pulse back into the batteries, hampering the growth of large lead sulfate crystals that build up on the lead plates, eventually leading to premature battery failure. This rather cramped photo shows the 2-inch by 2-inch device.
On-site power generation using wind turbines, micro-hydroelectric, or PV panels is becoming increasingly popular, especially where you can sell excess power to the AC grid, or, even better, when you can remain off-grid and utilize your excess electrical production for heating, cooling, or whatever else makes sense in terms of swapping solar power for LP gas, natural gas, grid electricity, or petroleum that you are now using.
Personally, we prefer not to be grid connected. With monthly connection fees exceeding the cost of the power we actually use, it makes no economic sense for us to support this otherwise ugly, dangerous and innefficient infrastructure. And calling the Grid a giant battery is simply nonsense. The Grid exists to generate and distribute, not store. A temporary excess of wind or sunshine may make your meter spin in reverse and make you feel like a hero, but that power usually goes into the Grid when it's not really needed, gets wasted as heat in the power lines, or goes to the nearest big energy hog who really doesn't care where the power came from.
 Our previous home used both wind and solar electricity, while the current house is solely solar powered. While solar's up-front cost may be the highest of the available alternatives in terms of cost per watt produced, it's the simplest to install, the longest lasting, and the easiest and cheapest to maintain. You can install it in "blocks", adding more capacity as you can afford it. Plus, our current site is ideal for solar but not the others, and you have to use what your site dictates! These are our sole electric power source: 840 watts of solar power by Kyocera, one of the oldest ceramics companies (and they aren't owned by an oil company!). Actually, we are currently upgrading to 1500 watts of solar in order to charge an electric car conversion of a 1979 Porsche 924. To see the technical specifications on these panels, just Click Here.
 Seen from the back of the panels, the center three panels can be switched to either power the house or charge our G.E. Electrak garden tractor, our cordless electric mower and string trimmer, or our electric-human hybrid trikes (seen on the Transportation Option page). These panels have now been reconfigured on sturdier racks, including 5 more panels (see below). And we can now charge our electric Porsche directly from 3 panels using DC charging instead of the car's on-board AC charger (more efficiently and quickly).
 This is a close-up of the switch arrangement with the weather cover open. Each toggle controls one panel using a Double-Pole, Center-Off, 20-Amp DC switch. Toggling up runs the three 12-Volt panels in series to run 36-Volt power to the electric tractor and electric-assisted trike. Toggling down puts the panels in parallel to run 12-Volt power to the house.
 Actually, as of late March 2009, this is our latest PV array. There are now 13 Kyocera panels. The oldest, a KC-120, is from 1997. The newest 6 are KC-130's, made in 2008. One of the panels in not shown since it is mounted on a different building. You can tell the newer panels by their darker blue color, indicating lower reflection of sunlight and more conversion to electricity. These are now wired as two banks with 5 panels in series, leaving up to 3 panels in series that run "24/36-volt" (actually 40 volts, open circuit) or "36/48-volt" (actually 62 volts, open circuit) directly up to the shed where they charge the electric tractor, electric car, the hybrid electric trikes, and a lawnmower for garden paths.
 Before flowing into the batteries the solar power gets intercepted by this device, a lightning arrestor. It connects to both the positive and negative wires, and shorts to a ground cable if voltage spikes too high.
 The next item in the positive wire is a simple diode on a heat sink. This one-way electrical valve prevents energy from flowing outward from the batteries to the solar panels at night. This has acyually been omitted since a new charge controller, the Outback FlexMax-80, hasl replaced its functions (see below).
 Then the power flows into this DC electrical service box. The left breaker cuts off the batteries. The next controls our present Load Diversion Controller (a Trace C-30, seen below). The next controls the solar input. And the final two run the two DC load circuits in our house. We don't use a non-renewable generator for backup power and didn't do so in our previous home either. The solar system is sized to ensure a 2 week supply of electrical power with no solar input. On the worst cloudy days, we still get one-tenth normal power input and an average of half of our days are cloudy. So designing with these factors in mind, we normally have far too much power. To see a free Adobe PDF file of our household loads, just Click Here.
 This is an amp-hour meter. It functions as a battery fuel guage. And even though it consumes a tiny bit of power, and injects a "whiney", high pitched, electrical noise frequency into the batteries, it's still worth its cost (about $200) for peace of mind, especially when you're just starting out in renewables and don't yet have a handle on your power usage vs. input.
 Most solar controllers shut the PV input off when the batteries are fully charged, or, if you are Grid-connected, excess power is sent into the Grid during sunny days and purchased back from non-renewable sources at night. Instead, we have been using a load diversion controller (Trace C-30) which channels excess power into an "off the shelf" hot water heater and a small chest-type refrigerator. Refrigeration isn't a huge priority in our home since we're not meat or dairy eaters. Still, we do occasionally have left-overs or home-canned condiments that need cooling. Soon this device will be replaced by a controller from Outback, the FlaxMax-80 (see below). It does something called Maximum Power Point Tracking, where excess voltage from the panels is turned into more amps flowing into the batteries.
 This is our previous load diversion controller. It uses PWM, or Pulse-Width Modulation, to divert the exact amount of excessive input power that will keep the batteries at a specified bulk-charge or float-charge voltage. But with precision came a nasty low-pitched electrical hum from the pulsed DC current sent to the diversion loads. Eventually this had to go in favor of the older C-30 (above), and the house got quieter both in terms of sound and electric fields.
 This is the aforementioned Outback FlexMax-80 MPPT charge controller. It replaces all of the functions of a reverse-flow-preventing diode (seen above), a load diversion controller (like the Trace C-30), and a PWM input controller (like the Trace C-40). It also checks the incoming voltage and continuously converts extra voltage into added amps, yeilding up to 30% more power from the same panels! It can handle up to 80 amps of power and has "AUX Send" output terminals to switch external power-control relays on or off at specific voltages. This allows tight control over our power diversion loads, including the water heater, refrigerator, electric tractor, electric mower, electric hybrid trikes and, most recently, an electric car and electric toaster oven. Plus, this unit logs all of the voltage, amperage, and power statistics generated by the PV system, available for viewing up to 128 days later. And, since it can handle many different output voltages, it can be switched to charge both our 12-volt household battery bank as well as the 36-volt electric tractor battery (but not at the same time). To see the manual on this product, just Click Here.
 This photo shows the little wood-covered, and heavily insulated, 15-gallon tank suspended behind the masonry woodstove, where the water can be heated using a spiral of copper pipe around the stove's chimney or by the electric heating element. The stainless steel, 12/24-volt heating element which we purchased to replace the 120-volt element in the water heater can be purchased, among other sources, at Backwoods Solar Electric Systems.
 Since neither the Trace C-30 nor the Outback FlexMax-80 is large enough to control the 32-37 Amps typically used by the water heater and refrigerator, we use two tiny 12-volt, 40-Amp relays to switch the power. Both are now controlled by the auxiliary relay output on the Outback FM-80 controller. These relays divert excess solar into two very useful assets! Although the refrigerator can run using 120-volt AC or LP gas, we just use the 12-volt DC option, straight from the batteries and solar system. When the battery voltage exceeds 14.5 volts, the loads are on. When voltage drops to 12.8 volts, they turn off. This gives us a 30% "duty cycle" yielding cooled foods without freezing anything, and hot water without boiling it.
 Our "critical" electrical devices (water pump, lighting, flour mill, radio) run directly from the batteries on 12-volt DC. Conventional 120 volt appliances run from this Exeltech XP1100 Inverter. Since humans are quite sensitive to AC electrical currents, the inverter is switched on only when AC loads are being operated. We use switched outlets at each appliance location and where a device uses a "black box" or "wall wart" to change voltage or switch from AC to DC current, we use additional labeled wall switches to activate only the intended device. This eliminates "phantom loads", which are energy sucking, unintended drains on an otherwise intentional, clean, and efficient electrical system. This inverter easily handles all of our household loads but is too small to use with our electric chainsaw or our electric car charger. For these we use a much larger (but cheaper, $717 on the Web) "modified-sine-wave" inverter (Tripp-Lite APS3636VR) mounted on the electric tractor.
Many homes that utilize RENEWABLE ENERGY for their electrical needs are wired for both low-voltage DC and standard AC loads. Since electric fields drop as voltage goes down, 12-volt lighting and appliances are an attractive option where low-power, low-amperage devices can be used. In high-amp loads like big motors or water heaters, the increased magnetic fields can offset any gains made from lowering voltage, unless those loads are far from the main living spaces. In our home, all of the lighting is 12-volt DC, although we have a few 12-volt compact fluorescent lamps that convert 12 volts of DC to roughly 10,000 volts of AC in the bulb's "ballast". This creates a moderately-sized electric field "no-man's-land" around the fixtures as a trade-off for one-fifth the energy use. For more detail, check the EMF Hazards page.
We have also started to use 12-volt LED (light-emitting diode) bulbs. If you can find the ones with the Philips Luxeon or Edison Opto-LED bulbs, they also put out a lot of light for very little power use. Our favorite living room task light draws only 6 watts but puts out the equivalent of 50-60 watts at 2700 K ("warm white"). There is no AC electric field to contend with, no inverter "noise", and it puts out very little heat.
Another factor that can reduce or eliminate AC electric/magnetic field exposure is the "sensible" use of an INVERTER in renewably-powered homes. If the home IS NOT connected to the GRID (by using a GRID-INTERTIE INVERTER), the "stand-alone" inverter turns low-voltage DC from storage batteries into "line-voltage" AC for standard appliances. Since many AC loads can be eliminated by using DC devices wherever possible, the inverter often doesn't have to be running all of the time! And if an inverter should break down (unlikely, but there's always a lightning strike!), powering essential loads direct from battery DC is great insurance.
Older and cheaper "square-wave" and "modified sine-wave" inverters rapidly and abruptly switch voltage levels to create a "choppy" sort of AC that only roughly approximates grid-produced AC. The modern "sine-wave" inverter produces a smoother, wave-like pattern of increasing and decreasing AC voltage that most electrical devices prefer. Not only do motors run cooler on sine waves, but the transformers found in many audio-visual devices and "wall warts" no longer hum. Sine-wave inverters can (at least with some modification) actually produce "cleaner" power than what's found on the grid. Grid-produced AC often has voltage spikes, or dips (requiring the use of surge suppressors) and high-frequency "harmonics" (or "hash") and "transients" (or "spikes") that have additional negative health consequences.
But even the best sine-wave inverters also generate harmonic frequencies and internally-generated switching frequencies. What to do about it? Some inverters constantly check for switched-on loads and turn themselves on only when called for (the Search Mode). And in our home, each cluster of AC outlets has an inverter switch to turn the AC power on only when it's needed. Either way, this eliminates inadvertent AC electric field exposure since no AC is being sent through the wiring most of the time. The Stetzerizer Filters I mention on the EMF Hazards page don't work well on some inverters. A couple of inverters that seem to be unbothered by the capacitive filtration of the Stetzer filters are the Xantrex Pro-Sine series and the Xantrex SW series.
 This is a Stetzer capacitive filter, composed of a small motor capacitor, a resistor to discharge the capacitor when it is unplugged, a couple of tabs to plug it in, and a plastic case. This one has been modified by wrapping an aluminum screen around it and securing it with "Zip-ties". This shields the home's occupants from high-frequency electric fields that radiate like an antenna from the capacitor's outer shell. I've contacted the manufacturer about this problem (including electric field readings before and after alteration) and received no response, but this rig works well.
 But by contacting your inverter's manufacturer, the technical staff may be able to build a frequency-targeted filter specifically designed to remove the unwanted frequencies the unit generates. We've done this with a call to Exeltech for our XP1100 inverter. This is what they sent. We've wired it into the inverter's output and enclosed it in a metal box to shield its fields. The Exeltech sees the capacitor in a Graham-Stetzer filter as a challenge to put the voltage and amperage back in synch. This makes for a very unhappy inverter. The solution from Exeltech is lots of induction and very little capacitance. This creates a large localized magnetic field, so the filter they sent is enclosed in a heavy steel box that encloses most of the field.
 And this is the final stop for AC current moving from the inverter filter to the AC loads. As you can see, we have only two AC circuits. One goes out to our shed where it powers chargers for an electric mower and a "string trimmer". It also powers an irrigation pump for the garden and an electric rotary tiller for the garden (Mantis brand). Plus it powers various AC shop tools and AC lights, when needed. And most recently it is being used to keep our electric car's gel-cell batteries warm on super cold (-22F or lower) winter nights.
Load Management: "Negawatts"
Amory Lovins of the Rocky Mountain Institute coined the term "Negawatts" to describe power that you didn't have to generate because you lowered your power requirements. In our household we call this process "Load Management". It involves the standard conservation methods of turning off unused lights, finding and eliminating "phantom loads", switching to energy-saving lights and appliances, etc. But we also include behavioral changes based on the weather forecast and power system design to maximize overall system efficiency.
The changes in behavior are what give conservation a bad name among those who don't really know how much energy they need to use, who have never been without an unlimited supply, and who aren't interested in following Nature's rhythms. If we know that it's going to be quite cloudy for a week or more, we might delay doing the laundry, hold off temporarily on some big computer project, or watch a DVD on the evening of a sunnier day.
And power use that maximizes direct use of solar energy as it's coming in is our first priority. Direct use eliminates battery storage losses, which are usually at least 10%. Second priority is using DC lights and appliances, powered straight from the batteries. This avoids lost efficiency from inverter-supplied AC power, which normally also exceeds 10%. We keep the solar panels clean, unshaded, and at an optimum tilt angle to capture maximum solar input. The individual solar cells of a solar panel are wired in series to obtain sufficient voltage for charging a battery or powering an inverter. And the flow of current in the panel, or in an array of panels wired in series, is limited to the lowest cell output in the series. Shading even one cell with dirt, leaves, or snow can cut the current flow from the affected panel(s) dramatically. For more details, check out our book, "Peoples' Power Primer" on our Home Page.
Other Concerns
EMF (Electro Magnetic Fields) and "Stray Voltage" (returning neutral ground currents) are causes for concern in any home electrical system. Low voltages generate the smallest electrical fields. But high-powered, low-voltage appliances require a lot of amps, generating large magnetic fields. Electromagnetic fields are easily reduced using two simple wiring options. Closely twisted wires, each with an opposing direction of current flow, cancel each other's magnetic fields to a large extent. And enclosing wire in a spiraling steel ("Greenfield", "MC", or "BX") or solid steel conduit (EMT) that's grounded will shield you from the electric fields. But the best options are Distance and less Duration. Doubling your distance from household wiring gives you one-half to one-fourth the EMF exposure. And turning off an inverter eliminates the time spent soaking up higher-voltage electrical fields from AC wiring and from high-frequency "radio" waves generated by the inverter itself.
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