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Most people have no appreciation of the amount of energy that must be expended in order to generate the electricity that runs a typical household. Until we actually get a chance to produce some by our own physical labors such as on an exercise bicycle or treadmill, we can't possibly understand what a bargain the electricity that comes into our home on the powerlines really is. The measure of electrical energy we're familiar with from reading the monthly utility bill is the kilowatt-hour, which translates to 1,000 Watts of energy for one hour's time. Let me put this into perspective for you. If you are reasonably physically fit, you might be able to generate 28 Watts, or 0.028 kilowatt by pedaling my wife's exercise bicycle at a moderate rate of speed. Do that for one hour and you'd have generated 0.028 (about 1/36th) kilowatt-hour (kwh) of electricity. You will be hot, tired and thirsty at the end, perhaps even exhausted and more than willing to have paid the power company the less than half a penny they would have charged for providing the same amount of electrical energy. In fact, I'll bet you'd eagerly hand over a hundred times that amount if you don't happen to be an avid bicycle rider. Just what could you have operated for lights while you were pedaling? Not a 100 Watt incandescent light bulb. Not a 60 Watt bulb. Not even the 40 Watt one like illuminates the interior of your refrigerator. Sadly, only seven 4-Watt (or four 7-Watt) nightlight bulbs could have been lit for an hour from all that exertion.
If you're thinking that a tiny, home-built alternative energy system will take the place of all (or a good portion of) the commercially-generated electricity you're now paying for, I'm afraid you're likely to be very disappointed. Unless you're willing to lead a minimalist existance, the electrical demands of your household will far exceed what can be generated by a solar panel or two. Just divide the kilowatt-hours on your monthly electric bill by 30 to get an idea of your daily kwh usage. Figure the average home-built solar panel probably puts out a daily total of about 0.22kwh on a clear and sunny day and maybe only an eighth of that on a rainy one and you'll see what I mean. Therefore, finding ways to save energy is a desireable and integral part of any small-scale alternative energy system. The need for energy efficiency will come more into focus once you get a micro-system up and running and are trying to balance the energy being generated with the demand. However, most everyone can save some hard-earned cash by using electricity more frugally than they are now. I'd like to pass along some energy-saving ideas that I have adopted in my own household.
Save Money on your Electric Bill Now
Most of us waste a fair amount of electricity simply because there is no compelling reason to be frugal when it's in plentiful supply. As long as the monthly bill from the utility isn't outrageously high, we seldom give our usage a second thought. Since you're reading about building an alternative energy system, chances are you are looking to save some money on your utility bill, or doing your part to help the environment by "going green". Both these reasons are noble ones, and can be worked towards in steps.
Perhaps the first thing to do, and certainly the easiest and least costly, is to reduce your electricity usage starting right now. This can be done in conjunction with building a system, if you choose to go that route, but would be beneficial even by itself. You have probably read that the biggest users of electricity in a home are electric heating and cooling devices including electric hot water heaters and air conditioners. Older appliances such as refrigerators and dehumidifiers generally use more energy than their modern, energy-saving counterparts. One thing that may pay for itself in short order is a thermometer or two for the fridge and freezer. If either of these are running colder than necessary, you are wasting electricity. I found this to be the case in our household. You've read advice elsewhere about turning the heating thermostat down, using air conditioning sparingly, purchasing energy-efficient appliances and devices, etc. so I won't rehash that here. However, if you're relying on hot water heated by electricity I do have a suggestion. For a number of years now, my wife and I have each taken to shutting the water off in the shower while we are lathering up. Just what percentage this saves I can't say, but I think 25% would be a good guess.
While it's true that going after the items that have the highest wattage should result in the biggest savings, this approach does have its drawbacks. Readjusting the temperature so that one shivers or sweats isn't for everyone and purchasing new appliances means a substantial cash outlay. Fortunately, there are ways to save a smaller amount of electricity that don't involve any real hardship and cost little to implement. Let's look at some of them.
De-fang Those Energy Vampires!
I'm referring to those electrical and electronic devices that lurk in abundance around most of our homes that we leave plugged in 24 hours a day and which consume a small amount of electricity continuously. Eliminate some and restrict the electricity-sucking of others and you may find that you've eliminated the equivalent of a kilowatt-hour of electric usage each day. Here are some potential culprits to go after.
Using Compact Fluorescent Lamps
Substantial savings, with little hassle or expense, can be realized just by swapping out old incandescent bulbs for electronic types. The compact fluorescent lamp (CFL) is a great energy saver, consuming less than a quarter of the electricity of an incandescent bulb for a given amount of light. At the time this was being written, the prices of these lamps were being subsidized in my locale, which reduced the cost to as little as 99 cents per bulb. These lamps, which have an electronic ballast running a spiral fluorescent tube, typically screw into the same socket that an equivalent incandescent lamp would. They are available in many configurations, including reflector style, that allow their use in most applications. The disadvantages to the CFLs are that they don't come to full brightness instantly and are very slow to warm up in cold temperatures. Another type of fluorescent lamp is the CCFL, or cold cathode fluorescent lamp. This thin-tube type is used for illuminating LCD screens and in scanners and copiers. It does not suffer from the same drawbacks mentioned above, although it is expensive. We may see these utilized in instant-on household lighting in the future. I use one of these CCFL lamps that operates from 12VDC as a desk lamp on my 12 Volt system.
One problem with using fluorescent lamps that are driven by electronic circuitry is that they emit RFI, or radio-frequency interference. While this doesn't present a problem for most folks, those who listen to AM or shortwave radio may regard them as a nuisance to be avoided. Incandescent lamps or LEDs operated from a battery source would be preferable in these situations.
Using LED Lamps
Light-emitting diode, or LED lamp technology for household use has become commonplace and the price has fallen considerably. The energy savings are usually greater than those provided by CFL technology, generally by about a third. They are more-or-less instant-on at full brightness and are relatively unaffected by temperature, thus having these advantages over CFLs. So-called white LEDs vary considerably in color temperature, from a pseudo-warm white similar to an incandescent bulb to a cool, bluish hue. Color names and their Kelvin temperature equivalents are roughly as follows:
The wattage and styling of small LEDs varies, those producing more than a fraction of a Watt in a single package generally requiring their being mounted to some sort of a metal heat sink. So-called super or ultra-bright white 5mm LEDs are useful to the alternative energy hobbyist and can often be purchased in bulk on the big Internet auction site, at a very reasonable price. These LEDs, which resemble the ordinary cylindrical variety that have been in use for years, typically like to draw a current of 20mA at a voltage somewhere around 3.2V DC. For 12 Volt applications, three can be connected together in series through a suitable voltage-dropping resistor so that the overall current is limited to a maximum of 0.02A. One thing all LEDs are intolerant of is high reverse voltage, so it may be prudent to protect them from this by adding a diode to the circuit. The shorter lead on a standard untrimmed LED, the one that can be seen to form the anvil that supports the central reflective "cup", is the negative. Although the typical LED package with its rounded lens usually casts a fairly narrow beam in the forward direction, there exists a flat-top style that is much better at mimicing a small incandescent bulb. Although a bit more expensive to purchase, the illumination from this type is more diffuse.
There are other styles of LED available now that are surface-mount devices (SMDs). Each device may contain from one to three light-emitting semiconductor chips, with each additional one increasing the overall brightness of the device by that much more. Unfortunately, it's usually impossible to tell simply by looking at them just how many internal chips they contain. Two SMD types have become popular; the 3528/1210 which can have up to three chips but generally only has one or maybe two, and the 5050 which almost always contains three. These SMDs are named for their physical dimensions, the latter measuring 5.0mm square. With the sections of a tri-chip LED wired together in series through a dropping resistor (generally of 150 Ohms), it will operate nicely from a 12V system. It appears to my eyes that a single 5050 will provide at least one-half the illumination of a 4-Watt incandescent night light, while consuming only 1/8 or less of the energy. Lamps for automotive use containing these SMDs are widely and cheaply available on the large Internet auction site. I have purchased styles that use one, three, six and nine of the 5050s for use in side marker, tail light and dome light applications. Again, you are looking for a current flow of 20mA through each chip in these small LEDs, a figure that remains the same when two or more are wired in series. In the case of a 12 Volt lamp using six, tri-chip SMDs (wired with 3 chips in series), we'd expect to see an overall current draw of around 120mA or 0.12A (18 chips divided by 3, then multiplied by 0.02A). Flexible strips containing a row of pre-wired SMDs (or standard LEDs) and associated resistors are also available at very reasonable prices. These strips may have a self-adhesive backing and will provide a fairly even light, similar to that of a tube fluorescent lamp. They are available in different lengths, most of which may be cut to a shorter size every three LEDs. I use several strips employing the 5050 SMD to provide illumination in small rooms that are not served by inverter power. Just be aware that the smaller, single-chip SMDs are sometimes mis-represented as being their larger cousins. A true type 5050 will have six connections and is 3 times brighter than a single LED.
Another kind of LED has shown up for sale on the large Internet auction site. This is referred to as a 1W LED lamp bead, and a package of ten can be purchased from Asian vendors for about $3.51 (with free postage), or even less if you get lucky. Considering these have 15 times the power of a type 5050, they may well be the best value yet for the do-it-yourselfer. These consist of a small encapsulation in a somewhat circular form that kind of resembles an egg cooked sunnyside-up. Meant to be mounted on a circuit board, there are two solderable tabs (legs) 180 degrees apart and a circular, heat-transferring plate on the underside. Assuming one doesn't purchase a circuit board, this plate can be glued to a suitable piece of metal for conducting the heat away and the tabs bent up so that wires may be attached. One tab has a (-) stamped on it for lead identification and connects to the negative. As with other LEDs, these operate from about 3.2VDC, but obviously draw a current of slightly more than 300mA, thus their 1 Watt rating. Three may be wired in series through a resistor for operation from a 12-Volt system, and a 10 Ohm resistor rated for a Watt or more should be suitable in this application. I have just started to experiment with these and cannot draw any conclusions just yet.
A fairly recent development is the "COB" or chip-on-board style of lamp, a narrow strip containing many points of light along its length. This arrangement has seen use in screw-base lamps that resemble the antique Edison variety, although the so-called filament is much thicker.
How much LED power is required to light a room adequately depends on the size of the room, how it's decorated and what level of illumination is desired. Generally speaking, you'll need at least one-half the electrical power (in Watts) that would be consumed by the CFL (or CFLs) presently providing the light, and probably closer to the same wattage. If you're still employing incandescent lamps, simply divide their total wattage by 4.5 to roughly determine the fluorescent equivalent. Based on my own experience, I can give you a general idea of what to anticipate on the lower end of the brightness scale. For a very small room such as a bathroom, plan on not less than 108 individual LEDs or chips. Probably triple that number for a medium-sized room such as a kitchen and more than quadruple the figure for the typical living room. Again, this isn't engraved in stone and the actual numbers required will depend on your personal circumstances and preferences, the color temperature of the LEDs and how near to capacity they are running. High-power LEDs and LED arrays may be calculated on the basis of their rated power consumption. For example, three or four 3-Watt LEDs would probably be needed to replace a 13W CFL or 60W incandescent lamp. Where the lumen output of an LED or array of them is published, it is helpful to know that an incandescent bulb puts out about 16 lumens/watt.
Contrary to what some may lead you to believe, LEDs do not last forever. Their light output will gradually diminish over time, although a true burnout or the point at which their illumination is considered to be seriously impaired might be tens of thousands of hours of operation distant. I must say from my own experience with these (individual) devices that at least some of them do grow noticeably dimmer within a few thousand hours and I have experienced several burnouts. In one case, a number of individual warm-white LEDs I was using appeared to emit less than half of their original brilliance after just 2,500 hours of use as nightlights and their color temperature had become much cooler. This would appear to be the result of phosphor degradation, whether from sub-standard construction or normal wear I cannot say. Either way, it is something to keep in mind, especially when considering an investment in the expensive, household variety of LED lamp. Unfortunately, an LED (like a CFL) will continue to draw full power even though its light output has dimmed.
Another thing to be aware of is differences in the brilliance of pre-wired LED lamps owing to the value of series resistors used. I have learned from experience that some vendors run their product well below the maximum ratings, which leads to less light output than expected, although perhaps extending the useful life of the lamp. Worse, I encountered one LED lamp array which appeared especially dim, although drawing approximately the correct amount of current for the number of SMD chips used. Upon examining the device closely I discovered a design flaw using a series-parallel resistor arrangement that was wasteful of electricity. In another instance, two multi-LED strips I purchased had only one chip out of three in each of the 5050s illuminating. Fortunately, I was able to rework the circuitry in both these cases and ended up with useful lights, but this illustrates how even lamp procurement can be a buyer-beware situation.
To sum up, CFLs or household-style LED lamps powered by a DC-AC inverter are the recommended way to provide general household lighting in an alternative energy system. There are also CFLs and perhaps LEDs available that will run directly from 12VDC such as for marine or RV use, but they are not as available or inexpensive as the household variety. LED arrays, perhaps built from scratch, are great for providing small amounts of illumination from 12V DC power and even general lighting when used in large enough quantities. I use both sources of light in my system, but primarily the first. Incandescent light bulbs will generally require more energy than a tiny home system can provide and should therefore be avoided.
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