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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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Will solar prices increase soon?
Jul23

Will solar prices increase soon?

Representatives from GoGreenSolar.com just attended InterSolar North America, one of solar’s leading networking events.  Businesses from more than 70 countries met in San Francisco to showcase new technologies, watch presentations, network, and discuss the future of solar.       Having had the opportunity to talk with suppliers, manufacturers, distributors, and service providers, we’ve discovered some key information that suggests that the days of low solar panel prices might soon be coming to a close.  Though no one has a crystal ball, industry-insiders believe that the prices for solar modules will be going up soon, meaning that the days of  $0.72 / Watt solar panels may not be around much longer.  Over the last several years, the surplus of solar panels being manufactured drove margins down, consequently pushing multiple manufacturing companies out of business.  While solar panels continue to get cheaper to produce, this consolidation process is now helping manufacturers that are left in the game. If you recall the trade scuffle we talked about this last year, the Chinese government was found to be providing illegal subsidies, allowing their manufacturers to sell their products below fair market value in the United States. In response, the U.S. government imposed anti-dumping tariffs of roughly 30% on Chinese solar cells.  As you might expect, Chinese manufacturers have been circumnavigating these duties by manufacturing solar cells outside China.  Taiwan, which now manufactures these cells, is now having difficulty keeping up with the increase in demand.  This could cause prices to increase. As the dominant solar panel manufacturer in the world, China recently swung back at the U.S. by implementing their own import duties on polysilicon coming from the United States.  Because this is a raw material used to make solar panels, this new tariff could also drive up the cost of solar panels. Though these issues may indicate a coming increase in solar panel pricing, even manufacturers can’t foresee what will happen several months into the future.  As you might imagine, this can pose a problem for solar projects that are scheduled months if not years into the future.  Imagine a multi-MegaWatt solar project- even a matter of a few cents would make a massive difference.   For a homeowner looking into a residential application, several cents per Watt isn’t exactly pocket change. While prices are still low, request a no obligation solar quote or call 1 (866) 798-4435. _____ Tom Jackson...

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All-New Enphase M250 Microinverter!
Jul09

All-New Enphase M250 Microinverter!

Enphase Energy, the world’s leader in solar microinverter technology, used Intersolar North America 2013 as a platform to launch their latest generation microinverter:  Enphase M250 The company’s first generation microinverter, the Enphase M175 is considered to be the world’s first commercially successful microinverter. The M175 was followed by the Enphase M190 microinverter, which has built-in trunk cables and is compatible with both 60 and 72-cell solar modules. Unlike the first two generations, the Enphase M215 microinverter featured a single mounting bracket and an improved cabling system, allowing up to 17 microinverters per branch circuit instead of 15 with the Enphase M190. The Enphase M215 is a lightweight microinverter designed for 60-cell solar modules. Enphase M215 has a maximum output of 215W AC – with a 96.5% CEC efficiency rating. It also features a single-bolt bracket for dramatically simplified installation, which has been passed on to the 4th Generation Enphase microinverter, the M250.  What’s different about the Enphase M250? Though its design appears to be nearly identical to the Enphase M215, the Enphase M250 microinverter is rated at 250W AC, meaning it’s compatible with solar panels up to 300W. But the key improvement to this model is that the M250 DC circuit already meets grounding requirements (NEC 690.35) because it’s isolated and insulated from the ground.  This improvement means that when you’re installing a Enphase M250s, you won’t need additional Grounding Electrode Conductor (GEC) in between each microinverter (copper). This not only simplifies installation, but enhances safety while saving material and labor costs. The Enphase M250 microinverter comes with comes with the industry standard 25-year warranty.  The Enphase M250 is rated at 96.5% CEC efficiency- the highest efficiency for microinverters available.  Like the M215, it’s also NEMA 6 rated for severe temperatures and humidity. When using Enphase microinverters (and an Envoy communications gateway), you can monitor the production of your system remotely with a web-based software called Enlighten.  The newest Envoy can handle up to 500 microinverters – or 100kW. Enphase now offers Enlighten in two versions of the software: Enlighten Manager for solar professionals to maintain the systems they’ve installed, and MyEnlighten for system owners to monitor the output of their systems. We’re excited to get some of these microinverters on some roofs. Check out the specification sheet for the Enphase M250!...

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