Renewable Energy - We Plug Into The Sun!
"I'd put my money on the sun and solar energy. What a source of power! I hope we don't have to wait until oil and coal run out before we tackle that." Thomas Edison to Henry Ford, 1931
Energy, in simplest terms, is a force that does something
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, "natural" (thermogenic, and increasingly tapped using highly polluting hydraulic fracturing technology) gas, or highly refined uranium-bearing ore that leaves behind massive amounts of radioactive waste at both ends of the process.
A tiny but quickly increasing 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, (either simply energizing banks of photovoltaic (PV) panels directly or by using mirrors to concentrate the sun's energy on oil-filled pipes that power a steam turbine generator), and high-temperature, underground, geothermal heat powering steam turbine generators.
- The Grid is intended and built for power distribution from areas of large supply to areas of high demand, not the storage, or the intelligent distribution, of small sources.
- Grid-intertie does not really use the Grid as a "battery". Sometimes you produce an excess, if your system is sufficiently sized, and sometimes you just end up burning coal, oil, "natural" gas, or neutrons (nuclear fission) like everyone else who is not producing power.
- If the Grid blacks out, so does your supply of renewable energy, unless you maintain some local storage.
- That black-out is for the safety of maintenance staff who need to work on faults in the distribution lines, and it cannot be avoided for the convenience of individual small energy producers.The Grid inter-tie inverter, local transformer, and the Grid line losses incurred in moving your expensively-produced power around make the system quite inefficient.
- Larisa says that Grid inter-tie is like bicycling with training wheels: You don't get the real experience of renewable energy; instead, 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 Grid-connected (your "base rate") may easily exceed the payments you can get for your excess energy.
- Connecting with the Grid is often an "all-or-nothing" decision in terms of equipment purchases and contracts, unless your discretionary funds are ample.
- You have to supply liability insurance to make sure you do not inadvertently electrocute any line workers, and there are usually up-front fees for the right to become a producer.
- Grid inter-tie inverters themselves can be more costly, not to mention the other needed equipment such as added disconnects, meters, etc.
- Many utility companies really do not want you to become a producer simply because, if your system is below a certain specific production threshold, they have to pay you retail prices for power they could buy elsewhere at a wholesale price (net metering).
- Look at any solar PV system on a winter's day after a snowstorm. If the panels are roof-mounted they will still be covered in snow. But on ground-mounted panels, the off-Grid systems will almost always be snow-free, while the Grid systems owners just don't feel compelled to bother with clearing them. Since shading even one cell in a PV panel can reduce its output to zero, and since that one shaded PV panel can reduce an entire "series string connected" PV array to zero output, who do you suppose gets more energy?
- And you don't like the idea of cutting back on consumption before sizing your renewable energy system? Well, in very hot or cold weather your local Grid utility asks everyone to cut back consumption or your monthly bill will be even higher due to high-priced energy purchases from neighboring utility companies with more generation capacity.
- Connecting to a 7000-volt+ AC supply is always more dangerous than dealing with a lower-voltage AC or low-voltage DC source.
- Your Grid-intertie inverter injects stress-causing harmonic "switching frequencies" into all of your neighbor's homes. This is listed as "harmonic distortion" in the inverter specifications, and it ranges from 2% to 10% of the output power.
- 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. In a shared power scheme "the biggest hog always feeds first".
- Don't even get me started on the future (or in the arctic, present) dangers of global climate change caused by burning massive amounts of coal, gas, and oil for Grid electricity. This is the paradigm you support when you are Grid-connected. The resulting increased size and lengthened patterns in the oscillation of the jet streams has led to more intense droughts, heat waves, storms, flooding, mud slides, heat and cold related deaths.........
The decentralized renewable home power system:
- Uses a safe, high-capacity, recyclable storage medium on-site.
- It is your insurance against black-outs caused by weather extremes or other more mundane Grid failures.
- It has extremely
high efficiency: low line loss, no transformer loss, and no inverter
loss on low-voltage loads running on DC straight from the batteries.
- It requires only a regular homeowner's insurance policy, if any.
- Low-voltage systems are often immune to local electrical code regulation and inspection, although I always opt for code compliance wherever possible. The National Electrical Code (NEC) has prevented a lot of household fires!
- The investment is made "up-front" with no increasingly large "power rental" costs each month.
- Any electrical inverter "noise", 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 quickly learn how to more effectively conserve power.
responsibility for the total environmental cost of your system and its
use lies only with you and the makers of your equipment. It is not an ongoing polluter, and it is not an "externalized expense" in some energy monopoly's budget.
- Solar PV in particular is modular by nature; you can add to it or change it gradually as your needs and budget change.
Home Power Systems can be categorized along a continuum of independent and distributed to dependent and networked, starting with:
Off-Grid, powered by renewable energy only. In the case of solar, you buy your next 30 years of power supply and 10 years of energy storage up-front. Small wind turbines and solar work well as a hybrid system since the wind often blows when the sun is not shining. Small-scale hydroelectric can operate seasonally or year-round.
Smaller off-Grid system with generator back-up power. Get cheap on the investment and pay for fuel instead.
Smaller off-Grid system with the Grid as a parallel system for large loads, or for back-up charging only. Add in a monthly connection charge for Grid service. This could be handy if you have enormous AC loads, like a workshop full of heavy duty tools, welder, etc. that would be expensive to run from a stand-alone inverter.
Grid-intertie, using the Grid as an energy "bank", where your excess cleanly produced power gets used primarily by energy-hog neighbors who have not made the investment in renewable energy. Drop the batteries to save some money, but you have no renewable back-up power in case of Grid failure. This is mainly for really big systems that are designed to sell power to the Grid at whatever price they are willing to pay.
Grid power alone. Renewable energy? What's that? Maybe you see a huge wind turbine or solar farm in your neighborhood and imagine your power comes from there, but that's still pretty rare. Meanwhile, you rent your power by the month and watch the bills slowly increase unless you cut back on consumption.
We have gotten some recent feedback (at a local introductory PV workshop) indicating that some large power users object to our use of the term "crutch" when describing the Grid or a fossil-fueled generator when powering very large loads. A crutch is just another tool, but it is made for temporary use in special circumstances, not as something you would choose to rely on permanently. If a renewably-powered household energy system is not yet big enough to run a shop, farm, or power hungry home-based business, then this crutch may be a temporary necessity until the business can fund the renewable upgrade. But money spent on fossil fuel, generating infrastructure, or more Grid-sourced power is money that could have been spent to upgrade a renewable power system.
Are you trying to use decentralized renewable power or centralized non-renewable power? If you do not like something, do not feed it. If you want to achieve change, do not hamper it. Indecision is, in itself, a decision if you do not like your present habits. We find that it is best to do what makes you proud of your actions, not just what makes the most economic sense in the narrow, changing confines of your current personal budget. Renewable energy can be done incrementally. Each step is one in the right direction.
You may have noticed that when I refer to the Distributed AC Power Grid I always capitalize the word "Grid". This is intentional, just as it is conventional practice to capitalize the word "God". The reason I do so is that people generally treat the Grid as they would a god, something unknown, unseen, all-powerful, omnipresent, infinitely good, and not-to-be-questioned.
Renewable energy, on the other hand, is something that is best known well if you intend to use it, is definitely seen when it is present, is limited in its power, is present to a lesser extent (for now, anyway), is realistically good (with some ecological footprints in terms of production resources, siting, wildlife impact, etc.), and is certainly not beyond question in terms of practicality for every situation.
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 sister site's EMF Hazards page.
Peoples' Power Primer - Our little book on how to live with renewable energyIf you want to learn more about renewable energy systems, many people have found our self-published book from 1999 very helpful. The subtitle calls it "Renewable Energy for the Technically Timid", but it slowly turns you into someone technically savvy enough to carry on an intelligent conversation with a systems dealer. This can, besides saving you lots of money and frustration in the long run, get you to make better choices based on your current and future electrical needs. There are sections on equipment, electrical terms, electrical usage and conservation, component sizing, choosing the right renewable source for your location, and system maintenance.
From the back cover: This is the dawn of a new age in electrical power production. Increasingly, homeowners are producing their own power using devices that capture free, clean, safe, and inexhaustible energy. While the utility companies are just catching on and gearing up, you could be getting wise and "growing your own." But shopping for this stuff, using it wisely, and keeping it running smoothly are a challenge if you can't converse in "tech-speak." Don't let those geeky buzz-words get you down! We'll have you discoursing with dealers directly, hastily harvesting heaps of energy, and managing maintenance matters momentarily. With ample visual and verbal cues, and while side-stepping the superfluous, this info-packed booklet will put you in the driver's seat on the Twenty-first Century road to renewables!
- Physical copies of "Peoples' Power Primer" (74 pages, spiral-bound) cost $8.50 each, postpaid in the U.S. (please add $0.41 sales tax if you are ordering in Minnesota), or $6.00 plus shipping elsewhere in the world. Contact us for international shipping costs. All others can simply send a personal check, traveler's check, or postal money order to:
30319 Wiscoy Ridge Road
Winona, MN, 55987-5651
- OR: To order a physical copy of "Peoples' Power Primer" using PayPal, Click Here. Clicking this takes you (very slowly if you have a dial-up connection) to a new screen with a "Buy Now" button, and this links to PayPal's secure order form where you can pay by credit card, checking account, or an existing PayPal account balance.
Our Home Power System - An Historical Perspective of our Off-Grid Solar PV from the Ground Up
When we discuss renewable energy with people it seems that we are usually talking past each other. We started with nothing and built a system from the ground up, meeting our needs as they increased. Most folks nearby already have unlimited Grid power, are supplying "needs" that we long ago decided were not sustainable, have little to no interest in reducing their energy consumption, and simply want us to tell them:
- how much to spend
- what to buy in order to make their super-sized lifestyle ecological, and
- how quickly will they pay for the system in energy savings.
Our first home electrical energy system, in 1983, was a retrofit on a normal 120-volt AC home electrical system. It was based on the battery in a 1968 Volkswagon (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 television 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, using the existing 120-volt wiring and outlet boxes for our tiny DC loads. 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 battery not designed for deep discharges. A new system was eventually needed.
We next purchased 36 round, 4-inch, silicon solar cells from an electrical surplus catalog. We mounted them to an aluminum sheet using silicone cement and wired all of the cells in electrical series (positive to negative terminals). They were covered by a simple wooden frame with an acrylic cover to keep the rain off. This homemade photovoltaic (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. While it was not a hybrid car it completed a hybrid power system.
Every home power system we have used since that time simply added more loads, more and better wiring, more power storage, more switching and circuit protection, more jobs done using solar or wind power, and more sources of renewable power generation. Some folks have asked why we ended up with PV panels mounted in different places and on various racks around our house. Partly this is because we added panels over time and partly it is because the best solar site nearest our house (to keep wire costs to a minimum) has enough trees surrounding it that space for more panels was limited. We wanted the closest possible site because we had a simple 12-volt charge controller that did not convert high voltages to lower ones for our battery bank as our current, more modern controller does. This meant that we needed thick, expensive copper wire buried underground to reduce power losses. The site south of our house gets sun from mid-morning until nearly sunset and is faced directly south. But the site next to our driveway gets sun immediately in the morning and loses it in late afternoon. The latest panels we have installed are 250 feet from the house, along our driveway for easy snow removal access, but they get the longest solar day of all our site possibilities. In 2019 all of our PV panels are now along our driveway.
So how do you decide what size your power system needs 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. One place to start is by using either a solar system size calculator for off-Grid systems or a solar system size calculator for Grid-based systems.
don't use a non-renewable generator for backup power and didn't do so
in our previous home either. Our 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 between 5% and 20% of our full 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. Beginning in February, 2011, we have switched all of our lighting to 12-volt
LEDs (light emitting diodes) in order to further cut our power
And if you are undecided about which type of renewable energy source might be best for your location, situation, and funding, you can click here see a flow-chart PDF (requires a free Adobe Reader download) that logically explains how we go about designing a renewable energy system.
The first questions you need to ask yourself are:
- What forms of renewable energy are available for harvesting locally? Wind, sunshine, running water?
- 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?
- Am I just going to use renewables in a new installation or should I switch from an existing Grid connection to renewables a bit at a time using separate electrical panels and circuits?
- How can I afford this and where do I start?
Our Energy Source
This is part of our solar PV system, an array of Kyocera panels ranging from 120 to 130 watts each. There are now a total of 19 Kyocera panels in our overall system. The oldest type, the KC-120, is from 1997. The newest five are KD-135's, made in 2011. Many of the panels are not shown since they are mounted on a different site that gets better early-morning or late-day sun exposure. You can identify the newer panels by their darker blue color, indicating lower reflection of sunlight and more conversion to electricity. Our most recent addition, in the fall of 2017, has been four 255-watt Sainty monocrystalline PV panels manufactured in China and four 260-watt Boviet monocrystalline panels made in Vietnam.
Some folks have asked us why we used multi-crystal silicon panels. The monocrystalline, or single-crystal panels are slightly more efficient, meaning the panels can be a bit smaller for the same power output, and they do a little better in cloudy weather. But this usually comes at a higher cost. Amorphous silicon panels are cheaper, sometimes flexible, and also have slightly better output in cloudy weather. But they are about half as efficient (meaning more space required) and have poor longevity. CIGS panels (made from Copper, Indium, Gallium, and Selenium) are cheaper to produce and have good efficiency. But they are about the same price and are relative newcomers. We chose what works well, has a terrific warranty, and was within our means at the time.
To compare specifications of most of the currently available commercial PV panels, just click here for SolarDesignTool.com's comparison page. To see how many fully cloudy days per year you will need to plan for, just click here for a map of the U.S. Annual Mean Cloudy Days. And for a really comprehensive guide to what is currently available in both on- and off-Grid solar, whether materials or installation-related, simply click here to get to Let'sGoSolar's highly informative website. You will find links there to answer any solar question I can think of.
System A: 1.2 kilowatts
Power Control Systems
This simple one-way diode on a heat sink is an electrical valve, preventing energy from flowing outward from the batteries to the solar panels at night.
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. This type of controller works well for loads that need to be run either fully on or off (more on this in a moment), but its loudly clicking relay was a bit of a distraction at times.
This is another of our previous load diversion controllers, the Trace C-40. 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 and supply the rest to another load (more on this below). 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 more sophisticated "maximum power point tracking" (MPPT) controllers that continuously monitor incoming amps and volts to maximize solar input.
Sophisticated Power Control
This is the previously mentioned 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, yielding 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 (more on these very soon, I promise!), including the water heater, refrigerator, electric tractor, electric mower, electric hybrid trikes and, most recently, a couple of 12-volt electric ovens.
- 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 either our 12-volt household battery bank, the 36-volt electric tractor, or the 36-volt electric trike (but not at the same time). To see the manual on this product, just Click Here.
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 once used 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 (Ni-Fe) 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 mechanically damaged Ni-Fe 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.
Beginning in January, 2010, we got a replacement battery system that was initially set up in parallel with our older one, as you can see in the photo. The new gray-cased batteries, with two levels of 5 batteries, 10 in all, are sealed, lead-acid gel cells made by Deka. We purchased them locally at that time since we heard that the price of lead was about to increase 50% and since our current batteries were over 6 years old.
The old wet-cell lead-acids, at the left, typically get up to 10 years of cycling at the rate we use energy while the sealed batteries should at least double that lifespan. They cost a bit more per amp-hour than equivalent wet cells but, besides the increased "cycle-life", you don't need to add water, vent explosive gases, or worry about corrosion of the terminals or leakage of the cases. They also have a much slower "self-discharge" rate and they don't have to be charged immediately after discharge since they won't "sulfate" like a wet cell (sulfation is the growth of large, insoluble lead sulfate crystals on the battery plates, gradually lowering amp-hour capacity).
The new and old battery sets have a slightly different resting voltage. The wet cells coast at 2.1 volts per cell, or about 12.6 volts as we have them set up. The sealed batteries coast at over 12.8 volts. So while we used both sets we had switches on the main positive terminals of both battery sets, allowing us to run from one or the other. The "wet-cell" battery bank held about 9.4 kilowatt-hours (kWHrs) of power and the sealed bank holds about 12.5 kWHrs. Beginning January 1, 2011, the older wet cells were recycled and we now rely solely on the new gel cells. In 2015 we increased our storage capacity to a total of 19 batteries, or just under 19 kilowatt-hours. We didn't really need the extra capacity, but having extra means that your batteries are never discharged very deeply, adding greatly to their "cycle-life".
Sizing Your Storage
Once you have completed an Electrical Loads Worksheet to determine how many amp-hours of power you will typically need per day you can begin to assess your ideal battery bank size.
Amp-hours/day X Number of days you wish to store X Factor for battery type (X2 for lead-acid cells, or X1.1 for nickel-based cells) X Average battery room temperature factor (80F = 1.0, 70F = 1.04, 60F = 1.11, 50F = 1.19, 40F = 1.30, 30F = 1.40) / Available cell or battery amp-hours = Number of parallel cells or batteries (round up to whole number).
System voltage (12-volts, 24, 36, or 48) / cell or battery voltage = Number or cells or batteries in series (round up to whole number) X Number of parallel cells or batteries (from calculation in previous paragraph) = Number of cells or batteries to buy.
This may seem complicated but it gets you into the right zone in terms of storage size. If you end up with too much storage your batteries may not charge as efficiently as possible and you can simply add more renewably-sourced input, a back-up generator, or Grid back-up charging. If you end up with too little storage you can add more or use the following power-using option.
Diversion Loads - An Option to Battery Storage
In our area of the U.S. we typically see about half sunny days and half cloudy, averaged throughout the year. So we eventually built a PV system with about twice as many panels as we would need based solely on our typical usage. What to do with the excess on sunny days?
This is a 300-watt, 0.5-ohm, 12-volt air heating resistor element made by Ohmite. Putting two or more of these in parallel gives you enough heat to make your own oven, which is what we have done. We often find that our masonry stove gets our water quite hot enough in the winter without additional solar energy, and we need to either use the excess for something like cooking, baking, or charging some other battery-powered device 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 Energy-Wise Canning & Cooking page. In the summer of 2011 we swapped three of these resistors for 5-ohm units which produce only 30 watts of heat at 12 volts. We found that we rarely needed 1200 watts, but using one 30-watt element makes the oven into a great incubator for yogurt or tempeh production. 60 watts gets it a little hotter. And switching the 300-watt unit on turns it back into an oven. Lots of flexibility again!
Thinking about where to send excess power brings to mind the notion of figuring out what you need electrical power for at all. In an age where oxen bred more oxen, the idea of switching to a high-priced tractor could seem pretty stupid. But, in an era when solar panels are manufactured mainly via robotics in a factory powered by solar panels, perhaps we've come full-circle. The main thing is to not get hung up on the devices used to fulfill your needs. It's not about the gadgets, it's about the energy source that you have available and how best to harvest it. Or as writer/blogger Sharon Astyk would say, don't "confuse a desire for familiarity with necessity". For instance, if you have always used a clothes dryer, don't presume that it is the only way to achieve dry clothing. A clothesline saves gobs of money when you need to purchase solar PV hardware!
This photo shows the little wood-covered, and heavily insulated, 10-gallon water heater tank suspended above and behind our masonry wood-stove, where household water can be heated using a spiral of copper pipe around our wood-stove's chimney or by using a DC 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 at, among other sources, Backwoods Solar Electric Systems.
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 used on our lead-acid "wet-cell" batteries. Since charging batteries "gas off" some hydrogen and oxygen when they are 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 do not 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.
Our current sealed, lead-acid gel batteries combine the gases internally and are charged at a lower voltage to prevent very much gassing, all of which means no dangerous gases released in the house and no loss of water that had to periodically be replaced.
We previously also used 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 "wet-cell" 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.
We are not using this, nor is it necessary, on the new gel-cell batteries, as they do not sulfate. It is now connected to the wet-cell, lead-acid batteries in our electric tractor.
DC Home Loads
Power flows form the batteries, or directly from the charge controller output, into this 12-volt DC electrical service box. As currently configured, two 30-amp, Square-D "QO" (AC or DC) breakers control our homes low amperage DC power circuits. This includes all of our LED lighting, our household water pump, and many other small devices. A 60-amp breaker controls power to the DC refrigerator and DC hot water heater. A 40-amp breaker controls the power coming from the relay (activated by the Outback FM-80) that powers some of the heating elements in our DC oven automatically. And the final 100-amp breaker switches and controls all of the heating elements of our DC oven manually.
The Electrical "Fuel Gauge"
This is an amp-hour meter. It functions solely as a battery fuel gauge. And even though it consumes a tiny bit of power, and injects a tiny but "whiney", high pitched, electrical noise frequency into the batteries, it is still worth its cost (about $200) for peace of mind, especially when you are just starting out in renewables and do not yet have a handle on your power usage versus power input. While this photo is showing battery voltage, we normally have it set to display our battery bank capacity in percent.
If we need more information than this, we simply toggle through the menus on the Outback controllers to check on long-term trends in power production and use.
AC Electrical Loads - Converting AC Into DC
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 inverters, such as this Exeltech XP1100 Inverter, which we previously used when our loads were a bit smaller. 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. The inverter was operated with an electrical filter unit supplied by the manufacturer. The filter remove the inverter's transistor switching frequencies, a form of harmonic distortion which can have health effects for those near unshielded household wiring (like the commonly used "Romex"). This inverter easily handled all of our household loads but was too small to use with our electric chainsaw or our electric car charger. We eventually replaced the Exeltech with the model seen below.
Since early 2011 this was our household inverter. We traded up from the 1100-watt Exeltch to the 1800-watt Statpower (now Xantrex) unit so that we could operate full 15-amp AC loads, such as our Makita electric chainsaw or our electric car's on-board charger. Although this unit has no built-in filter to remove harmonic switching frequencies it can be used with capacitive filters, such as the Stetzerizer (see below). This unit has now been sold to a nearby neighbor and we have upgraded to a massive Outback VFX-2812 (2800 watt, 12-volt) sine-wave inverter seen here.
Cleaning Up Your Green Power
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. The Stetzerizer Filters do not work well on some inverters. A few inverters that seem to be unbothered by the capacitive filtration of the Stetzer filters are the Xantrex (or Statpower) Pro-Sine series, the Xantrex SW series, and the full line of Outback inverters (although they do cause some drainage of power when the Outbacks are idling).
Load Management - The Basics
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 (CFLs) 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 our our sister-site's Low-Frequency EMF page.
We have also started to use 12-volt LED (light-emitting diode) bulbs for all of our lighting. If you can find the ones with the Philips Luxeon, Cree, or Edison Opto-engine LED bulbs, they also put out a lot of light for very little power use. If not, the clustered single-LED bulbs work well too if you can find ones that are bright enough and have a color temperature you can stand. We use mellow, "warm white" bulbs while many of the LEDs out there are the more harsh, but brighter, "cool-white" types. The "light engine" type bulbs have to dissipate a lot of very localized energy to preserve the life of their big LED surfaces so they have aluminum heat-dissipating fins. Our favorite living room task lights draws only 4 watts but put out the equivalent of 40 incandescent-bulb watts at 3000 K ("warm white"). There is no AC electric field to contend with, no inverter "noise", and it puts out less heat than a comparable CFL.
We have also recently found (after 2 years of searching) an online source (Energy Efficient Products) for both 110-volt and 12-volt bulbs in Rome, New York that has very low prices, along with pretty good service, documentation, shipping, and responsiveness to its customers. Although we use the 12-volt bulbs, and still recommend their generally problem-free AC models, some of our 12-volt friends have have had problems with a few of the lowest-wattage models causing interference with their FM radios and televisions. If you order bulbs from them be certain that they cause no interference within 15 days or they may not replace/refund your order!
And in our home, each cluster of AC outlets has an inverter switch to turn the AC power on only when it's needed. This eliminates both inefficient "phantom loads" and inadvertent AC electric field exposure, since no AC is being sent through the wiring most of the time.
Load Management - "Nega-Watts"
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.
If you would like to figure out where the big power uses are in your household electrical system you can use a worksheet that we have prepared. It uses a conversion factor that takes the typical 87% efficiency of an inverter into account when estimating AC loads. Simply look for the nameplate on the device or appliance and you will see figures for volts, amps, or watts (volts times amps). Fill in the figures and you will see what your biggest consumers are. From there you can determine what needs replacement or possible elimination. Or you can buy/borrow (around here, from local public libraries) a recording kilowatt-hour meter (like the "Kill-A-Watt" from Intertek) and simply plug appliances into it for a period of time to see their average electrical consumption. This works really well for intermittent loads like refrigerators/freezers.
Some Helpful Web Resources
- The Midwest Renewable Energy Association - The MREA
- Solar system details with loads of good graphics
- NABCEP Installer's Guide for those who really want to get it right the first time
- Our electrical consumption worksheet will help you to find where your power goes
- U.S. Solar Radiation Resources Maps,
by month or annual, using various collector tilts/tracking. Just check
four choices and you get a map showing, essentially, how many hours of
full, 1000 watt/meter, hours you will see at your chosen panel angle,
for a month or year, either as an average, minimum, or maximum.
- SolarDesignTool.com's PV comparison page, listing most of the current commercially available PV panels by brand and model number.
- U.S. map of Annual Cloudy Days per year, to help estimate PV system sizes
- Our logical flow chart showing how we plan a renewable energy system
- An excellent article from Homepower Magazine about how to choose a wind-turbine
- U.S. average wind speed map at 33 to 164 feet above terrain