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Even if silicon is actually the industry common semiconductor in most electric devices, including the solar cells that pv panels employ to transform sunshine into power, it is hardly the most efficient product readily available. For example, the semiconductor gallium arsenide and associated compound semiconductors offer practically double the effectiveness as silicon in photo voltaic products, but they are rarely employed in utility-scale applications because of their high production price.
University. of I. (http://illinois.edu/) professors J. Rogers and X. Li discovered lower-cost methods to produce thin films of gallium arsenide that also made possible usefulness in the sorts of products they can be integrated into.
If you could lower considerably the cost of gallium arsenide and other compound semiconductors, then you could increase their own range of applications.
Typically, gallium arsenide is placed in a individual thin layer on a little wafer. Either the preferred device is created directly on the wafer, or the semiconductor-coated wafer is break up into chips of the desired dimension. The Illinois group made the decision to deposit numerous layers of the material on a single wafer, making a layered, “pancake” stack of gallium arsenide thin films.
If you increase 10 levels in 1 growth, you only have to load the wafer a single time. If you do this in ten growths, loading and unloading with heat range ramp-up and ramp-down take a lot of time. If you consider exactly what is needed for every growth – the machine, the research, the period, the workers – the overhead saving this method offers is a significant expense reduction.
Next the scientists separately peel off the layers and transport them. To accomplish this, the stacks swap layers of aluminum arsenide with the gallium arsenide. Bathing the stacks in a solution of acid and an oxidizing agent dissolves the levels of aluminum arsenide, freeing the single thin sheets of gallium arsenide. A soft stamp-like system picks up the layers, just one at a time from the top down, for exchange to one more substrate – glass, plastic or silicon, based on the application. Next the wafer can be used again for an additional growth.
By executing this it's possible to produce a lot more material more fast and more cost effectively. This process could produce mass quantities of material, as opposed to just the thin single-layer method in which it is generally grown.
Freeing the material from the wafer also opens the possibility of flexible, thin-film electronics produced with gallium arsenide or many other high-speed semiconductors. To make products that could conform but still maintain high performance, which is significant.
In a document released on-line May 20 in the journal Nature (http://www.nature.com/), the group explains its methods and demonstrates 3 kinds of devices making use of gallium arsenide chips produced in multilayer stacks: light products, high-speed transistors and solar cells. The authors additionally offer a detailed price comparison.
Another advantage of the multilayer approach is the release from area constraints, particularly essential for solar cells. As the layers are taken out from the stack, they could be laid out side-by-side on one more substrate to make a significantly bigger surface area, whereas the standard single-layer procedure limits area to the size of the wafer.
For solar panels, you want large area coverage to catch as much sunlight as achievable. In an extreme case we may increase enough layers to have 10 times the area of the standard.
After that, the group programs to explore more potential item applications and additional semiconductor resources that might adapt to multilayer growth.
About the Publisher - Shannon Combs contributes articles for the www.residentialsolarpanels.org/ resident solar power generation</a> web site, her personal hobby weblog based on suggestions to assist home owners to save energy with sun power.
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This guide will help you start exploring the possibility of going solar at your house.
Let's get up to speed on solar electricity basics with a few key definitions...
PV module: AKA a solar panel, converts energy from the sun into direct current (DC) energy. PV modules come in varying wattages and sizes. Typical PV modules used on home installations are 200 watts and about 14 square feet.
PV array: A number of PV modules wired together. Using 5 x 200 watt PV modules creates a 1,000 watt PV array. Typical array sizes range from 2,000 to 5,000 watts and up.
Inverter: Converts DC electricity into alternating current (AC) electricity used around the house. A 3,000 watt inverter will output 3,000 watts of AC electricity given enough PV input. Typical inverter sizes range from 2,000 watts to 7,000 watts.
Grid-tied solar system: An electrical system comprised primarily of a roof or ground mounted PV array and inverter, which are connected to and interact with the utility grid. Other devices called over current protection devices or OCPD are used for safety. Energy from the PV array goes fist to household loads and any extra power is stored on the utility grid.
Kilowatt hour (kwh): One kilowatt (1,000 watts) for 1 hour = 1 kilowatt hour. The utility company charges you by the number of kwh you use (or 1 unit in your utility bill).
The three main factors that will determine your eventual grid-tied solar electric systems are daily energy requirements, available shade-free space, and project budget.
Daily energy requirements: The PV array will be generating most, if not all, the energy your home needs, so looking at your own usage is a good place to start. Look on your utility bill or call your utility company to find out your energy use in terms of kilowatt hours per day or kwh/day. It's best to use the average kwh/day for the last 12 months to account for seasonal variations in energy consumption.
While you're talking to the utility company, ask them for their "interconnection agreement." This is essentially the contract you'll enter with them when you connect PVs to their grid. Once you know your average kwh/day usage you can plug this number into simple calculations to determine system size and cost.
Shade-free space available: PV modules need direct sunlight to produce electricity. Even a little shade on the PV array will cause significant drops in power generation. The PV array needs to be in a location where it will receive direct sunlight between 11 a.m. and 3 p.m. The early morning and late afternoon hours don't really count for solar production because the sun's rays pass through too much atmospheric debris to be "strong" enough to produce much power.
Every location on Earth has an average "peak sun hours" ranging from 4-6 hours, or the yearly average number of hours per day for good solar production. These peak sun hours occur between 11a.m. and 3 p.m., so shading outside this time is less of a concern.
Tools like solar pathfinders and sun charts can be used to find out if that big tree across the street will shade the PV array in December/January. You might have more shade-free space than necessary or it could be the limiting factor in your system's size.
Project budget: Solar electric systems are not cheap and usually cost more than expected. Modest systems start at around US$5K but the majority fall in the US$20K to US$40K range. There are government incentives and rebates to take advantage of that will significantly decrease out of pocket costs. It may not be possible to produce 100% of the energy you use and many systems are supplemental, producing as much as space and/or budget allow.
The cost becomes more reasonable when looked at as a long term investment. After all, you are pre-paying for your electricity at a fixed rate for what could be the rest of your life and providing free energy for your kids and grandkids.
People often complain about a long payback period, but isn't any payback whatsoever a good thing no matter how long? What's the payback on the last car you bought? A PV electric system is a risk free investment with a guaranteed payback.
Easy calculations for system size and cost:
If you know your average kwh/day or know how many kwh/day you would like to produce, a simple calculation will determine system size and cost.
System size in kilowatts (kw) = (kwh/day) / 4 hours (peak sun) x 1.43 (system losses)
Step 1: Divide average kwh/day by number of hours of peak sun, or (kwh/ay) / 4
Step 2: Multiply by 1.43 to account for system losses due to friction, heat, and other inefficiencies.
Example: What size system is needed to produce 20kwh/day?
20kwh/4h = 5kw
5kw x 1.43= 7.15kw
7.15kw = system size to produce 20kwh/day assuming 4 peak sun hours (11am to 3pm).
System cost = system size x US$7,000 to US$9,000
Step 1: multiply system size by US$7 for competitive system cost installed
Step 2: multiply system size by US$9 for conservative system cost installed
Example: How much would a 7.15kw system cost?
7.15kw x $7,000 = US$50,050 = competitive system cost
7.15kw x $9,000 = US$64,350 = conservative system cost
We used to see an average cost of a grid-tied system to be about $9,000 per kilowatt (array size) installed, but with a growing market, systems are being installed for as low as $7,000 per kilowatt in competitive areas. Keep in mind that these costs are before any incentives or rebates are taken into account.
Hopefully this helped introduce you to some of the basic considerations needed before purchasing a solar electric system. There is far too much information to cover in a short guide and anyone serious about greener living should contact us at firstname.lastname@example.org
How we light up the places we live and work makes a big impact on how we feel. It also makes a big impact on the environment. The kind of bulbs, the kind of fixtures, the kind of power, and the habits we keep can all add up to a very significant greening. Start with the fact that a conventional incandescent bulb turns only around five to ten percent of its consumed energy into light, the rest goes out as heat. From there, there’s no limit to how green your lighting can be.
Here are 10 highly effective ways to go greener. Hit it.
1. CFL: The better bulb
Compact florescent bulbs (CFLs) are those swirley little guys that look like soft-serve ice cream cones. Actually, they come in a myriad of different shapes, sizes, and colors of light. Economically speaking, they’re a great deal, too. CFLs cost a bit more than an incandescent, but use about a quarter as much energy and last many times longer (usually around 10,000 hours). It is estimated that a CFL pays for its higher price after about 500 hours of use. After that, it’s money in your pocket.
Also, because CFLs release less heat, not only are they safer, but your cooling load is less in the summer. CFLs aren’t hard to find anymore, and many cities will give them away for free. Wal-Mart has plans to sell 100 million of them.
2. Get the LEDs out
LEDs are a definite TreeHugger favorite. LEDs, or light emitting diodes, are a technology that allows for extremely energy efficient and extremely long-lasting light bulbs. LEDs are just starting to hit the consumer market in a big (read affordable) way and still cost quite a bit more than even CFLs, but use even less energy and last even longer.
An LED light bulb can reduce energy consumption by 80-90% and last around 100,000 hours. They even light up faster than regular bulbs (which could save your life it there are LEDs in the brake lights of your car). They are almost always more expensive presently, but we have seen the cost go down steadily. It’s no coincidence that the Millennium Technology Prize went to the inventor of the LED.
Most LED lamps on the market have the bulbs built into them, so you buy the whole unit. For screw-in bulbs, check out Ledtronics, Mule, and Enlux. For desk lamps, check out a few affordable ones from Sylvania and Koncept. For more designer models, look at LEDs from Herman Miller and Knoll. Vessel rechargeable accent lamps represent some of the interesting new things LEDs can do as well.
Light isn’t all about the bulbs, though. Having eco-friendly lamps and light fixtures is key to greening your lighting. When scouting for new gear, keep your eyes out for lamps made with natural, recycled, or reused materials. Lights made from recycled materials include metal, glass, or plastic, and natural materials can include felt, cloth or wood. Interesting lamps that use reclaimed materials include these made from traffic signal lenses, and these made from wine bottles. Also, don’t be shy about borrowing ideas for reuse in your own projects (see DIY).
Fluorescents last a long time, but when they’re dead, they have to be properly disposed of. CFLs, like all florescent bulbs, do contain a small amount of mercury, which means they definitely can’t be thrown in the trash. Every city has different services for recycling, so you’ll need to see what’s offered in your area. LEDs, to our knowledge, do not contain mercury, but the jury may still be out on how to best recycle them.
5. Wall warts
Power adaptors, or “wall warts” as they’re affectionately called, are those clunky things you find on many electrical cords, including those attached to lamps and some light fixtures. You’ll notice that they stay warm even when their device is turned off. This is because they in fact draw energy from the wall all the time. One way to green your lighting is to unplug their wall warts when not in use, attached lights to a power strip and turn off the whole switch when not in use, or get your hands on a “smart” power strip that knows when the devise is off.
By far, the best source of light we know is (yes, you guessed it) the sun, which gives off free, full-spectrum light all day. Make the most of daylight by keeping your blinds open (sounds obvious but you might be surprised). If you want to go a little farther, put in some skylights, or, of you are designing a home or doing a renovation, put as many windows on the south-facing side of the house as possible (or north-facing if you live in the southern hemisphere). To take it even further, sunlight can be “piped” inside via fiber optics and other light channeling technologies.
7. Good habits
As efficient as your lighting equipment might be, it doesn’t make sense to have lights on when no one’s around. Turn out lights in rooms or parts of the house where no one is. Teach your family and friends about it too and it will become second nature. If you want to get a little more exact, follow these rules:
Standard incandescent: turn off even if you leave the room for just seconds. Compact fluorescent: turn off if you leave the room for 3 minutes. Standard fluorescent: turn off if you leave the room for 15 minutes.
8. Do it yourself
We’re always encouraging people to take matters into their own hands. So much great eco-innovation comes when people create the things they can’t find elsewhere. Lighting is an especially accessible and rewarding thing to tackle. For some inspiration, check out the Cholesterol lamp made from cast-off plastic egg cartons, and the recycled Tube Light. Strawbale building pioneer Glen Hunter made some LED fixtures when he couldn’t find any he liked on the market. Eurolite, the company from which he bought the lighting components, liked his designs so much they decided to sell them.
9. Dimmers and motion sensors
Motion sensors can be a good way to keep lights turned off when they’re not needed, and dimmers can give you just the right amount of life, and timers can be set to turn things on and off when needed.
10. Get green power
A great way to green your lighting is to buy green power. More and more electric utilities are offering customers a green power option on their bill. Signing up for green power usually means paying a few more dollars a month to support energy in the grid that comes from renewable sources like wind, solar, or biogas. For some more info on how to get green juice, look here, and for the greenest grids in the States, look here. More info is also available in How to Green Your Electricity.
Note: This article is written by Yahoo Green.
The Case for Solar-Powered LED Lighting
|Rapid developments in solar cells, LED lighting and energy storage are creating great opportunities for solar-powered solid-state lighting, says Moneer Azzam of SolarOne Solutions.|
|The outdoor lighting industry, as with so many other application-oriented industries, assumes that the power source is infinite and always available. This is a tribute to the reliability of the electric grid - at least in developed-world nations. It has certainly made life simpler for the lamp/lighting designers who, for the most part, are able to divorce the lamp characteristics from the energy source. The developed world is starting to learn that the power source is far from infinite.* |
Some companies are not waiting to see the bottom of the barrel, and are exploring alternatives that range from replacement power sources to energy demand reduction. A number of companies are developing technologies that achieve both: SolarOne Solutions' work in solar-powered solid-state lighting under the SOLED™ brand name is an example of this.
[* Estimates indicate at current levels of energy usage, the earth has about 150 years of energy stored in the form of oil, coal and uranium. However, if the entire population of the earth consumed as much as Americans' do on a per capita basis, that amount drops to 15 or 20 years.]
Solar electric lighting systems do in fact connect to a truly "infinite" power source - the sun. However, as we all know, this source is intermittent. In the case of solar outdoor lighting, the power source is inversely related to the load (the lights turn on when the sun goes down). This relationship leads to an important conclusion; the system must rely on energy storage (e.g. batteries), unless it remains connected to grid.
Now in order for a solar lighting system to perform reliably, the solar panel and battery must be sized for the period of longest nights, shortest days and cloudiest weather, all of which occur at the same time each year (see figure 2). Historically, the solar industry has addressed this worst-case scenario by seeking out the most efficient lumen per watt DC lamps and over-sizing the system for the rest of the year. That translated to DC fluorescent bulbs, bigger solar panels, more batteries, higher costs and less-than-appealing appearance.
This approach confined the market for solar lighting to areas closer to the equator with highest average levels of solar irradiation and temperatures that did not affect the performance and lifetime of the DC fluorescent bulbs. It also left the markets in the higher latitudes, typically with higher per capita wealth levels and greater lighting needs rather under-served.
SolarOne perceived the shortfalls in the status quo products and the under-served market as an opportunity to integrate white LED lighting into its product offering and an area on which to focus its development efforts. With a deep understanding of solar cell characteristics and system operation along with resources in circuit design and micro-processor programming and strong relationships to major manufacturers of key components, the company saw their role in integrating the components into useful products and developing the brains that most cost-effectively manage their operation. At this year's LightFair International, SolarOne announced the first embodiment of such a system in a lamp, driver, and system manager combination named SOLED™ mc2 Technology. With the proverbial umbilical cord to the electric utility severed, the mc2 Technology seeks to create a more symbiotic relationship between the lighting load, solar cells, battery storage and the user. While the use of high efficiency components and circuit designs are a vital aspect of the technology, attaining the highest level of resource utilization is paramount to the mc2 philosophy. This is where the LEDs make an enormous contribution.
1. More effective illumination
Fluorescents, while providing a cool color temperature at a very efficient lumen per watt (lm/W basis still have fundamental deficiencies. In addition to their bulk and inherent fragility, fluorescents project light poorly, in all directions around the lamp and in almost 180 degrees in the plane of the lamp. Thus their utilization, (the amount of usable light projected) is lower than the technical calculations of efficiency suggest. A reflector can redirect the light around the lamp downward, but there are efficiency costs. Further, as the fluorescent lamp is controlled to direct light downward for ambient lighting, approximately 30% or more of the light is lost. For more demanding task lighting, when even greater control is required, the loss from the fluorescent is approximately 50%.
In contrast, LEDs produce directional beams of light, up to 90% of which is usable for ambient lighting and 70% of which is useable for task lighting (assuming that the lighting design incorporates multiple LED installations to compensate for shadows in a space measuring 4 feet square). The relatively low lumen output ratings of LED lamps are often times compensated for when looking at the foot-candle levels at the illuminated surfaces. In other words, for outdoor lighting applications, SolarOne estimates that an LED lamp rated at 45 lumens per watt will perform equivalently to a fluorescent bulb rated at 75 lumens per watt. This facet of LEDs offer an enormous side benefit to areas with dark-sky mandates.
2. Optimized system efficiency
Solar cells and LEDs share many characteristics - even in the assembly process. For example, both solar cells and LEDs require sorting and balancing to optimize performance. The SOLED mc2 LED Lamp and Lamp Driver is configured to effectively eliminate the need for balancing resistors and their associated losses. Perhaps more significantly, through its range of testing and field experience, SolarOne has identified "sweet spots" in LED operation that optimize current flows and light levels with solar panel and battery costs. The trade-offs are quite different than grid-connected or even automotive applications. This translates into almost a 10% improvement in overall system efficiency.
3. Fine tuned to user needs
Unlike conventional lighting, LED's lend themselves to programmability and fine-tuning. Delivering light not only where, but at the level and time it's most needed is another cornerstone of the mc2 philosophy. This aspect alone can reduce solar panel size and battery capacity by as much as 50%. The mc2 System Manager offers the user with 16 set lighting profiles they can select for their application. The company also offers factory installed custom profiles, depending on the size and nature of the project.
4. Battery runtime extension
SolarOne's extensive field experience with solar systems highlighted the need to give options to users in selecting the preferred intervention methods for those cases where battery drops to lower states of charge. By giving the user the ability to define their "hierarchy of needs" and apply it to system operation, mc2 adds a new tool to address solar panel size, system cost and siting issues to the satisfaction of the customer.
5. Cold weather
Another shared characteristic between Solar cells and LED lights is improved efficiency, performance and lifetime at colder temperatures. This brings advantages over other types of lamps whose performance and lifetime drops in colder climates - such as DC fluorescents. An LED lamp is expected to last at least 5 to 10 times as long as a DC florescent in these environments. It is another arrow for solar/LEDs' quiver in serving markets at latitudes further from the equator.
SolarOne and the other companies in this business space are just scratching the surface of opportunities for outdoor lighting. Quantum leap developments are underway in the fields of LED lighting, solar cells and energy storage alike. With each advancement, the benefits multiply throughout the system. As an example, the latest generation of high-brightness LEDs are playing a key role in realizing the potential of the SOLED mc2 concept.
Cutting the tether from the outdoor light fixture to the electric grid is akin to what happened in the telecommunications market with the advent of the cellular phone. LED bulbs are conceptually solar cells in reverse - solid-state devices converting electricity into light. By combining them we create wireless, solid-state lighting. Who knows what markets will emerge? One thing seems certain, great opportunity exists in the compatibility between solar cells and LED lighting, it is just a matter of seizing it.
Note: This article is adopted from Ledsmagazine.com.
It's not hard to see why outdoor solar lighting is all the rage. Of course it's great that you don't have to pay for electricity, but more important for most folks is the fact that you don't need to install any wiring. Take the light out of the box, put it beside your walkway or in your garden, and you're done. Because most solar lights have a built-in darkness sensor, you don't even need to think about turning them on and off.
The technology for outdoor solar lighting is improving rapidly. Solar lights are looking more attractive, shining more brightly, and their run-time is getting longer. To give you a better sense of how these lights work and how to select a good one, here are the basic components:
Solar Panel: The solar panel has a photovoltaic cell inside, which converts sunlight to an electrical current. A solar panel's effectiveness depends on the size and quality of the solar cell and the transparency of the protective cover. The solar cell itself is usually the most expensive part of a solar light. As photovoltaic technology advances, prices are gradually coming down.
Battery: The solar cells are wired directly to a re-chargeable battery that stores the electricity generated by the cell. A diode located between the cell and the battery ensures that electricity flows only one way -- into the battery. NiMH batteries are often used because they stand up better to the frequent charge and release cycles than standard NiCAD batteries. NiMH batteries also have a significant environmental benefit. They can be disposed of without harm to the environment. The battery is usually the second most costly component of a solar light.
LED: "Light-emitting diodes" are like miniature light bulbs that are installed in-line on an electrical circuit. The light emitted by an LED bulb is the byproduct of electrons moving through a semi-conductor material. Since there's no need for a filament, these bulbs last a very long time and also do not generate waste heat. The standard runtime of most LEDs is upwards of 100,000 hours, while an incandescent bulb usually lasts for about 3,000 hours. LEDs can be wired in clusters to intensify the light output.
Sometimes manufacturers of solar lights increase brightness by combining LEDs with a small halogen bulb. But as LED technology improves, most manufacturers are shifting away from halogen in favor of all-LED solutions. The only exception is solar security lights, which still require the extra light intensity provided by halogen bulbs.
Circuitry: This is the most crucial component of a solar light, and the one that most often separates the good solar lights from the bad. Wiring determines how efficiently the stored electricity is converted into light. High-quality circuitry will give you a longer-lasting, brighter solar light.
Run Time: The quality and integration of the components described above determines how many hours the light will shine. Run times can be as short as an hour or as long as a few days.
Housing: Whether a solar light is strictly functional or highly decorative, its housing needs to be UV-stable and weather tight. Assembly should be minimal. In most cases, the solar panel will be an integral part of the light itself. Sometimes the solar panel is separate, which allows you to mount the light where you need it, and then mount the panel where it will get the best sun exposure.
Solar lights have either a manual on-off switch or a photo resister that turns the light on when the sun sets and off when it gets light again.
Getting the Most Out of an Outdoor Solar Light
Placement of a solar light is all-important. For maximum solar gain, the solar cell should face due south and be positioned on an angle so it is perpendicular to the sun. The surface of the solar cell should not be shaded by foliage or structures at any time during the day. If the light has an automatic on-off sensor, it should not be placed near any other bright light source, such as a street lamp, because it may cause the light to shut off prematurely.
Note: This article is written by Gardener Supply Company.
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