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Solar 101: What’s the difference between microinverters and string inverters?
Mar19

Solar 101: What’s the difference between microinverters and string inverters?

If you’re a homeowner or an installer doing residential or small scale commercial solar installations, you essentially have three choices for converting the solar system’s DC power into AC power: You can either go with new microinverters or with string inverters—with or without DC power optimizers. All will work, but there are differences, especially in certain situations. String Inverters: The solar industry standard With residential string inverters, all solar modules are connected in a series circuit to a DC electric cable, which is then connected to a single inverter box mounted on a wall by the home’s main AC panel (as well as to any required DC disconnects). So it’s a very centralized system with a limited amount of labor. Modern string inverters not only convert the power from DC to AC, but also use Maximum Point Power Tracking (MPPT) to deliver the maximum amount of power available. This is important, since each solar panel can produce different amounts of power due to manufacturing anomalies, intermittent shading, leaves, dirt, passing clouds, and/or other factors. While a string inverter’s MPPT works fairly well, especially in sunny areas with no obstructions, having all solar modules tied in a series circuit can still be a disadvantage for several reasons: 1)   MPPT technology is essentially drawing the average amount of power available, rather than the full amount available from each module. As a result, the entire solar array can lose 15% to 30% or more of its full potential output because one or more panels in the string are temporarily shaded or have debris. 2)   If you have limited roof space and need two arrays with different sun orientations, each array will need its own string inverter. 3)   Similarly, since module mismatch can cause efficiency issues, you’ll need to use the same brand and panel voltage within each string. 4)   String inverters don’t easily allow for expanding the system in the future unless you purposely oversize the inverter, wiring, and other BOS parts. 5)   While it’s common to have online monitoring with string inverters, the monitors only measure the performance of the entire array. So, if an array isn’t producing the expected power, installers will need to individually test each panel for malfunctions. 6)   String inverters are typically warrantied for 10 years and have an expected lifetime of 12 to 15 years, while solar panels typically last 25 years or longer. Thus, the string inverter will need to be replaced at least once. Adding DC Power Optimizers to String Inverters Adding DC power optimizers to a string inverter system can solve most of the above string inverter challenges. Power optimizers are relatively new...

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What’s wrong with solar permitting?  Q&A with Deep Patel, CEO of GoGreenSolar.com
Mar04

What’s wrong with solar permitting? Q&A with Deep Patel, CEO of GoGreenSolar.com

Experience any roadblocks while trying to pull a permit for a photovoltaic (PV) system in your city?   Paying too much?  You’re not alone.  Getting your PV system a permit can be a daunting task for both customers and installers. According to report by Clean Power Finance, about 23% of PV installations cost more than expected.   More than a third of solar installers actually avoid working with certain Authorities Having Jurisdiction (AHJs) because of their solar permitting processes. What’s wrong with these permitting processes and what can we do to fix it?  What’s being done right now? No standardized permitting process or fees have been set among AHJs, or the entities that have the power to determine and enforce code requirements for PV systems.  I’m catching up with GoGreensolar.com CEO Deep Patel to touch on some of these issues. From a solar contractor’s perspective, how do varying permitting procedures affect your business? It makes it more difficult to generate a proposal.  There really is not a cookie cutter solution, so unfortunately we can’t just generate proposal on the spot.  It often takes weeks because we have to call the Authority Having Jurisdiction (AHJ), leave messages, and wait for them to call us back. So when you’re trying to get a proposal out, it often takes up your time.  This increases the wait-time for customers and often drives up the soft costs of solar.  Would you say that this cost is passed along to consumers? Yes, proposals currently have to account for this unpredictability. When you’re running a business with that kind of uncertainty, you have to pad the proposal in case of any unexpected fees or codes changes. In an attempt to bring down the time and soft-costs that come with this inconsistent permitting process, the DOE’s Sunshot supported Clean Power Finance’s efforts to develop a National Solar Permitting Database.  The goal is to provide solar professionals a platform to give testimonials about different AHJs and coach each other through these permitting processes.  I guess you could say it’s like Yelp for solar contractors to review AHJs. A National Database can help solar contractors work more efficiently, but is it not placing a Band-Aid on a bullet wound?  Given that the DOE already has a standardized set of permitting policies known (solar ABCs), is it even fair that the burden of navigating these arduous permitting processes is imposed on those who are installing solar electric systems?  The problem is that the DOE doesn’t have the jurisdiction here.  The DOE can’t force the cities to follow a standardized permitting process, but they can make recommendations and city governments can choose to adopt them.  Meanwhile,...

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Will solar work in your state? (Infographic)
Jan17

Will solar work in your state? (Infographic)

Do photovoltaics(PV) really work outside of California?   When first looking into solar, it seems only natural to assume that solar panels will work best in hot areas. Contrary to this intuition, solar panels perform best in cool environments.   You’ll get the maximum yield from your PV system when direct sunlight is hitting your array, but solar panels continue to generate electricity with ambient sunlight on cloudy days. Tip: monocrystalline solar panels are known to be more efficient in low-light conditions than polycrystalline solar panels. Rain can also rinse off “soiling,” or the dirt and dust that builds up on solar panels, making them operate more efficiently. Some areas also have rewarding “net metering” policies that credit you for the the energy your PV system generates on those clear days.  It’s fed into the electricity grid and later used to offset your energy consumption (kWh) on cloudy days or at night when you’re drawing from the utility grid.   To learn more about grid-tied PV systems, read Grid-Tied and Off-Grid Solar 101. With the installed price of solar photovoltaic (PV) systems declining, investing in clean energy is more cost-effective than ever.  Solar is even saving homeowners money in cloudier cities like Seattle and Portland. Solar is steadily appearing on more rooftops throughout the country- which U.S. cities have you noticed more PV systems being installed?...

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How to make a light source out of plastic bottles.
Jan08

How to make a light source out of plastic bottles.

Well over a billion people on our planet don’t have access to electricity and this D.I.Y. solar light can brighten homes during the day and replace toxic kerosine lamps. Watch this video: 4 easy steps to light a room with a solar bottle lamp: 1. Add a couple teaspoons of bleach to keep the water clean. 2. Drill a hole in roofing to fit the circumference of the plastic bottle. 3. Push the bottle up through the hole in the roofing. 4.  Seal the the bottle with polyester resin to prevent a leaking roof. [i] It’s a stunningly simple lighting solution: sunlight passes through the water inside the bottle, refracting light, and brightening the room. Even though you might not insert a 2-liter bottle into your roof, this might also come in handy if you’re want to illuminate the inside of a tree-house. Check out the infographic below and “share” this page if you think this is cool!    ...

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Is the 60W lightbulb illegal?
Jan03

Is the 60W lightbulb illegal?

Beginning 2014, Federal Efficiency Standards Outlaw the Production of “old-school” 40 and 60 Watt Incandescent Lamps About 6 out of 10 Americans don’t know that traditional incandescent lamps are being phased out. [1] As of January 1st, 2014, it goes against Federal law to manufacture one of these old things… This federal regulation was signed into law by President George W. Bush in 2007, banning the production and importation of 40 and 60 Watt incandescent lamps.  Over the last several years, 100W and 75W incandescent were also phased out. About a third of consumers plan to stock up on these 60W incandescent lamps while they’re available in stores. Others will reach for halogen or compact fluorescent lamps (CFL). What about LEDs? More frequently referred to as LEDs, Light Emitting Diodes are small digital light bulbs that fit into an electrical circuit board and produce light when the correct voltage is applied to them. An LED light source comparable to a 60W incandescent lamp might be around 12.5 Watts. LEDs generally have a higher price tag, but they can actually save you money over time. Not only does an LED light source consume far less energy than a 60W lightbulb, the lifespan of this solid-state technology goes far beyond that of traditional incandescent lamps.  Most LEDs will last at least 10 years and some will last a couple decades. LED lighting is available in different wavelengths, meaning that they’re now offered in a wide range color temperatures like cool “daylight” colors and cozy orange colors you’d expect to come from an incandescent bulb. The infographic below compares Incandescent Lamps with CFL and LED lighting. [1]...

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Surface area needed to power the world with solar?
Dec30

Surface area needed to power the world with solar?

How much surface area would be needed to power the whole world with solar panels? 496,805 Square kilometers or 191,817.483 square miles Just to give you an idea of what this would actually look like, take a look at the image below. This info-graphic shows the cumulative surface area required to power the entire planet with solar in 2030 (678 quadrillion BTU), given that solar panels will have 20% operating efficiencies.  This includes all electrical consumption, down to machinery and...

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