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Quick Look at STC vs. PTC Ratings
Sep17

Quick Look at STC vs. PTC Ratings

What’s the differnce between STC & PTC? Looking at the specifications for a solar panel, you’re going to see two distinct ratings:  STC and PTC, both of which refer to DC (direct current) Watts of the solar panel. STC rating Standard Test Conditions, or STC ratings, are the solar panel’s name plate value.  This means that if it’s a Sharp ND-250QCS, 250 Watt solar panel, the STC rating is 250 Watts.   STC ratings reflect the solar panel’s production in ideal conditions, which is actually a flash of light shot at the solar panel in a lab environment. PTC rating When you’re looking to get an idea of PV output, PTC ratings are a more realistic number to look at.   PTC ratings, or PVUSA (Photovoltaics for Utility Systems Applications) Test Conditions, show the results from a test that more closely mimics real-world conditions.  PTC ratings are based on 1,000 Watts per square meter of solar irradiance at 10 meters above ground level, at 20 degrees Celsius, and with a wind speed of 1 meter per second. As seen in the image above, the Sharp ND-250QCS, 250W solar panel has a PTC rating of 223.6 Watts.  If you were using these solar panels for your photovoltaic system, using the PTC rating of 223.6W to estimate output would provide a more accurate, “real-world” number than the STC rating of 250W. Keep in mind that there are still other factors that will effect PV output.   There will usually be some energy loss via wires, inverters, etc.  There’s also normal degradation of solar panels over time and environmental factors such as soiling (dirt), heat, and shading....

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What’s the optimal angle for my solar panels?
Aug08

What’s the optimal angle for my solar panels?

Enter in your country, state, and city to calculate the optimum tilt of your solar panels every month. The optimal angle varies throughout the year, depending on the seasons and your location and this calculator shows the difference in sun height on a month-by-month basis.  For even more precise angling, you would need to track the sun as it moves throughout the day on a minute-by-minute basis.  This can be accomplished with an automated mechanical solar tracker, but unfortunately this is not very economical. The sun reaches its peak at solar noon each day (exactly half way between sunrise and sunset) and this calculator shows the angle at that time of day. At solar noon, the irradiance from the sun is at its zenith and you can generate the most energy. As an example, the sun is due south at solar noon in the northern hemisphere.  To get the best performance out of your photovoltaic panels, you would face them due south at the optimum angle so that the panel is receiving as much sunlight as possible at this time. The best angle for your solar project also depends on when you want to get the best out of your photovoltaic system. If you want the best performance during the summer months (when there is the most sunlight), you would angle your photovoltaic panels according to the height of the sun in the sky during these months. If you have the ability to adjust your photovoltaic panels throughout the year, you will benefit from having the optimum performance from your solar system all of the time. If you like this calculator please...

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Are solar panels tested for hail?
Aug01

Are solar panels tested for hail?

Are solar panels tested for hail, golf balls, or other kinds of impact? If solar panels are broken by some kind of impact, is this damage covered by the solar panel manufacturer’s warranty? If you’re about to drop thousands of dollars on a solar system that’s supposed to last a few decades, you obviously want to be confident that you’re not investing in equipment that could be ruined by one day of extreme weather.  It’s a valid concern. The ambiguity regarding hail resistance and impact testing for solar panels can be frustrating, so I spoke with a claims representative from a major solar panel manufacturer to get some clarification. The short answer is that there’s probably no manufacturer’s warranty that will cover this kind of damage, but any high-quality solar panel will have tempered glass that’s designed to take a beating and tested accordingly. If you’re worried about protecting your investment from this kind of damage, make sure that you pull a permit for the system and consult your property insurance provider.  There should be no problem getting the coverage you need if you go by the books. Back to the question about manufacturer’s warranty-  even though you likely won’t find a manufacturer’s warranty that covers hail damage, any reputable brand will test their solar panels to obtain industry-recognized quality certifications. In North America, these tests are a 5 ft·lbs impact of a 2 inch diameter ball of 1.18 lbs that’s dropped at a distance of 51 inches- no parts of the solar panel can be damaged to acquire this label.  If the solar panel has undergone this standardized testing successfully, you will see something like this in the specifications sheet. Quality Certifications from the Sharp ND-240QCJ specification sheet Because solar panel manufacturers usually sell to markets outside of the United States, modules are often subject to additional testing standards such as Europe’s “IEC.” Quality Certifications from Canadian Solar CS6P-240P specification sheet The European quality certificate specifically for hail is IEC 61215, which is circled in the image above.  Solar panels with this label were shot with frozen ice balls at varying sizes and speeds from an air gun. The most substantial of this IEC impact testing comes at 39.5 m/sec from a 203 gram ice ball.  The solar module must perform at a maximum of 5% degradation with no visible damage. If you live in an area that’s prone to hail storms, you should get solar panels that have been tested for impact and talk with your homeowner’s insurance company about your coverage options. That being said, if your system is going to experience hail that would dwarf...

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Another DIY Solar Success Story
Jun05

Another DIY Solar Success Story

John and Renee Shean’s DIY Photovoltaic Installation If you’re at all like John and Renee Shean, you’re probably turned off by the solar companies that want to charge you an arm and a leg for PV installation.  Maybe the lease or power purchase agreement (PPA) models just don’t cut it for you.  John Shean is one of those people.  John is an electrician who just wanted to work with a knowledgeable supplier that would offer fair price on the materials needed for a complete PV system.  Earlier this year, Renee and John Shean had been trying to “go green” over time.  First came dual-pane windows, then a tankless water heater and pellet stove.  Installing a solar system was just part of this natural progression.   Renee explains how she and her husband made the decision to go solar: “We probably would have done it a lot sooner, but it was just too costly.  Most of the cost was in the installation and since John is an electrician he knew he could install the panels himself.  However, we found it impossible to find anyone that would sell us just the panels, that is until John found Deep at Go Green Soar.  So now we are the proud owners of our own solar system, furthering our quest to ‘Go Green’!” As an electrician with the International Brotherhood of Electrical Workers (IBEW),  John wanted to find a supplier that would get him the right equipment for the job so he got in touch with us at GoGreenSolar.com.  He explained how he’s an electrician and just wanted to discuss the different options available, purchase the equipment, and install the system with his own hands.  John chose to work with an Ironridge racking solution and Sharp solar panels, which are manufactured in Memphis, Tennessee by IBEW workers. “John is more focused on the mechanics of it all,” says Renee, “Being able to see the meter running backwards and being able to pull up the system online and monitor each panel and the energy it’s producing, although I think that part is pretty cool too!” “Oddly enough, my favorite part about our solar system is actually seeing the panels on the roof every time I drive into the driveway.  It makes feel happy knowing I can say to myself, I’m creating my own energy!  I say odd because not too long ago seeing the panels on the roof was considered ‘unsightly.’  I remember my parents were approached in the 70’s to put panels on the roof to heat our pool and they considered it until they found out you would be able to see the panels from...

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Small Scale Solar Electric Power Systems
May03

Small Scale Solar Electric Power Systems

In the natural world, solar energy has two primary effects: heating and photochemical. The primary photochemical effect is photosynthesis, which is the foundation upon which all carbon fuels are built. Coal, oil, natural gas, wood, alcohol and any other fuel built by life are all forms of stored solar energy. The heating effects of solar energy can be used for both heating and cooling by proper design of buildings, a practice that goes back many thousand of years. Wind power and ocean current power systems are basically means of capturing solar power for human use. A sail boat is a solar powered boat, even though most people don’t usually think of it as such. In the modern technological world we have learned to use focused sunlight to generate heat and, perversely, power refrigeration systems utilizing absorption type refrigeration. Focused sunlight can be used to power steam operated electrical generation plants and very high temperature ovens for scientific research. The ancient Greek scientist Archimedes was said to have used focused sunlight to set Roman ships on fire during the siege of Syracuse in 214-212 B.C. Modern technology has a much simpler system for producing electrical power from sunlight. The photovoltaic effect ( a very distant relative of photosynthesis) produces electricity directly from sunlight. Devices called solar cells capture sunlight and produce electricity. Solar cells are usually small, perhaps a few square inches at most. They are not very thick and are usually supported and protected by glass or plastic and can be arranged in panels with up to several hundred cells connected and supported by some sort of framework. GoGreenSolar.com offers a considerable selection of panels providing power up to 250 watts or as small as 7 watts. Portable power systems are usually designed to charge batteries and provide constant regulated power. In many parts of the world, even in remote parts of the United States, electrical power is hard to come by. If you live 50 miles from the nearest power line, the connection fee for electrical service can be quite prohibitive. Many businesses and ngo’s have designed solar power systems to provide electricity for remote sites. GoGreenSolar.com offers portable systems suitable for remote sites. They also offer components to create permanent off-grid power systems. An off-grid system can be as simple as garden lighting or a charger to allow you to sit in the park or on a mountain trail with your portable electronics, whether a cell phone or lap-top computer. Perhaps it can be a back-pack system to provide power for a back-woods camping trip. Off-grid systems can be an emergency power system or a complete power...

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Basics of Wiring Parallel and Series
Apr23

Basics of Wiring Parallel and Series

An introduction to series and parallel circuits Series connections: When a positive (+) end from one solar panel is connected to the negative (-) end of another module it is called a series circuit or a “string.” When wired in series, the voltage increases but your current will remain the same. For every connection made in series, multiply the voltage by the number of solar panels. For example, let’s say you have four solar panels that are 12VDC, 10A.  When you wire all four of them in series, just multiply the voltage of one solar panel for the number of solar panels in the string.  In this case, this will be a total of 48VDC. Keep in mind that connections in series do not change the amperage.  The amps of one solar panel = the amps of all four solar panels connected in series. Parallel connections:  When positives(+) are connected with positives(+) and negatives(-) with negatives(-), this is called a parallel circuit.   When wired in parallel, the current (amperage) will increase with each panel. In this case, if you were to wire the same four 10A, 12 VDC solar panels in parallel, they’d have a current of 40 amps.  The voltage wouldn’t have increased, so it would still be 12VDC. One last note- always talk with an electrician before attempting any sort DIY solar project and stay in compliance with any laws, fire codes, etc. that are specific to your area.  Any questions?  ...

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