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Central Inverter vs. Microinverters: The Pros and Cons

So you’re installing a photovoltaic (PV) system.  Do you go with microinverters or stick with a central inverter? What does an inverter do? The task of an inverter is to convert the direct current (DC) electricity produced by your solar panels into alternating current (AC), which is needed for the overwhelming majority of electrical devices.  The AC power that isn’t used by your home is back-fed into the utility grid, hence the term “grid-tied.”Click here to learn about the basic components of a PV system. Microinverters Microinverters convert the DC electricity from each panel into usable, grid-quality AC electricity.   They attach behind individual solar panels in the array, allowing each module to operate independently instead of optimizing for the “weakest link.”  Turning the solar panels’ DC electricity into AC at a modular level means there is no single point of failure and you’re maximizing the potential output of your system. Because of this, microinverters are particularly advantageous for systems in locations that have shading or some potential coverage (i.e. dirt, snow, chimneys, etc). Microinverters also use a technology called Maximum Power Point Tracking (MPPT), which optimizes the electricity output by responding to the varying levels of light every couple of minutes. In addition to maximizing the yield of your system, micoinverters’ easy design, installation, and scalability have made them popular for residential applications.   Besides getting up on a roof and pulling a permitting, adding to your existing system with microinverters  like the Enphase M215 microinverter should be little trouble.   Each microinverter has its own IP address so it can be monitored remotely with web-based software.  Microinverters also allow for module level monitoring and comprehensive analytics, making it possible for you to view how much energy is being produced by each solar panel. The main disadvantage of microinverters is the price tag- they still cost more per Watt than central inverters.  Critics of microinverters have also made note that these sensitive electronics can exposed to elevated temperatures on the roof and there is lack of field data to go along with their 25-year warranty. Enphase Energy currently dominates the microinverter market and has been increasingly popular for residential applications, particularly in California.   Enphase offers a twenty-five year limited warranty on their microinverters. Microinverters are recommended for residential and DIY solar applications, especially if there are shading concerns or there’s a chance of expanding the system in the future. Pros: • Easy design, installation, & scalability • Maximum Power Point Tracking (MPPT) • Optimized for shading • Remote monitoring capability Cons: • Less of field data • More expensive • Relatively new technology Central Inverter Traditionally, central inverters have...

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Monocrystalline or Polycrystalline?
Jun01

Monocrystalline or Polycrystalline?

Most solar modules used today are either polycrystalline or monocrystalline, otherwise known as mono and poly. So what is the difference between poly and mono? For the sake of brevity, the difference between the two is that monocrystalline is composed of a single crystal of silicon, while polycrystalline is composed of many crystals.  Generally speaking, mono solar panels are more efficient but poly solar panels are a better use of your money. Monocrystalline Monocrystalline, which is also called mono or single crystalline, is the older of the two technologies and has been around since 1955.  Monocrystalline is still used to manufacture photovoltaic cells today and is arguably the most efficient material available. A monocrystalline solar cell is composed of a single crystal of silicon, a purity that can be identified by a dark, even coloring.  Extensive filtration is required to purify the silicon so it can be used for monocrystalline solar cells.   A single monocrystalline silicon seed crystal is slowly pulled from the high-heat molten silicon.  As it’s drawn upwards, the silicon cools and solidifies as a single ingot.  This cylindrical ingot is then sliced into thin pieces that are then cut into the cell shapes you see on a monocrystalline solar panel. Monocrystalline solar panel panels will typically have higher efficiency rates (15-20%), converting energy particularly well in low-light and lab conditions.  Mono panels will generally have higher nameplate ratings than poly.  Because monocrystalline solar cells usually have higher efficiency, these solar panels will make good use of limited roof space. The biggest draw-back is cost.  Mono solar panels come at a premium so unless you’re particularly limited on roof space, they’re not the best use of your money. Pros: • High efficiency • Good for limited space • Performs well in low-light conditions Cons: • High Cost • Sensitive to soiling and shade • More silicon is wasted in the manufacturing process Polycrystalline Polycrystalline, which is also called poly or multicrystalline, has been used since 1981.  Until recently, polycrystalline solar panels were easily identified by their solar cells that have a textured look resembling a granite countertop or shattered glass.  Most poly solar panels just have a dark blue color now. Polycrystalline cells are composed of multiple silicon crystals, which is a cheaper way to manufacture solar modules.  Polycrystalline cells are commonly made with a cast of molten silicon.  When these cells are being created, they cool faster, creating smaller crystals.  Just remember that poly means many because it has many crystals.  Because poly solar panels are easier to produce, they’re less expensive – making them the ideal choice for most people.   Though monocrystalline is still...

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LA Solar Incentive Program and Feed-in Tariff Program

For those of you who may not know, the Los Angeles Department of Water and Power has developed a Solar Incentive Program (SIP) to support solar energy in Los Angeles. This Solar Incentive Program can help you with the cost of installing a new solar system.  The Solar Feed-in Tariff Program, which allows owners of large-scale on-grid solar systems to sell back unused energy, is currently in the works. This Solar Incentive Program was created to help meet the aim of Senate Bill 1, which is essentially an extension of the California Solar Initiative (CSI) and the Energy Commission’s New Solar Homes Partnership (NSHP).  Basically, the goal of this program is to promote solar for LADWP customers to help California reach its energy goals.  By providing a financial incentive to homeowners who install on-grid photovoltaic systems, LADWP hopes to encourage homeowners to invest in solar energy.   LADWP customers who have photovoltaic systems installed can receive a lump sum payment upfront based on the anticipated performance of their new system. To calculate an estimate of the Expected Performance Based Buydown (EPBB), LADWP’s website has an online calculator. This provides an idea of the energy production, annual kWh, CEC-AC rating, Design Factor, CSI rating, and incentive amount.  With this information, LADWP is able to figure out how much money to pay the customer upfront. There are benefits that go beyond this one-time payment.  According to the LADWP website: “Customers who qualify and complete an installation are provided with a ‘net meter’.  When a customer’s solar system produces more energy than they use, the excess energy is calculated as a credit on their bill, and their meter will run backwards.” This means that when an LADWP customer’s solar system is producing excess energy, it goes back into the grid.  The meter runs backwards and LADWP is then able to credit their customers with energy towards their electricity bill.  Conversely, LADWP is presently developing another system to promote the use of solar technology through the Solar Feed-in Tariff Program, also known as the CLEAN LA Program.  Though Solar Incentive Program customers are not qualified for the CLEAN LA Program, this particular program is designed primarily for larger-scale commercial use.  Through this Feed-in Tariff system, customers who produce 30kW and higher, can enter a contract to sell 100% of the energy produced at their facility to LADWP at a fixed rate for up to twenty years. Here’s a brief run-down of how the preliminary stages function: application process: To qualify for this program, applicants must go through a six-week application process.  Applicants provide the base price for the energy, proof of site control, and complete facility and one-line diagrams.  They...

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Free Energy Classes by Southern California Edison

Did you know that every time you pay your electricity bill in California, Edison uses some of that money to provide the public with educational workshops?  These classes are a unique opportunity for everyone to learn how to save money, energy, and the planet. We recently attended a class about plug-in electric vehicle chargers at Southern California Edison in Irwindale, California.  When we first arrived, we sipped on coffee and walked around the interactive lighting display, which has an assortment of lamps for commercial and residential use. Prior to the class itself, we went on the “Smart Energy Experience” tour, which is essentially a tour through a model home designed to demonstrate how Edison plans to help consumers actively monitor their energy consumption in real-time. Our tour guide also explained how energy saving incentive programs can work for Edison customers. The futuristic “smart” electric meters and appliances will make it easier than ever to monitor and successfully reduce energy usage.  Our tour guide talked about the appliances and fixtures that the model home featured. Our tour guide went over all the changes the average household can make to create a more eco-friendly, cost-effective lifestyle. This model home had recycled glass countertops, bamboo floors, and a washer-dryer combo that communicates electronically to pre-set dry cycles. Our tour guide also explained how energy saving incentive programs work. Implementing natural light in the home is a powerful way to save energy. Check out this solar light pipe that utilizes natural light in the home!Edison offers a wide range of introductory and specialized classes that range from from LED lighting, to heating and refrigeration.  Be sure to sign up for a few of these free workshops and learn how you can save energy. Don’t forget to take the “Smart Energy Experience” tour before your class!...

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How much is a solar panel system for a 2,700 square foot home?

Everyday I get at least one email from a customer that asks, “How much is a solar panel system to power a {insert number of square feet here} home?” It’s quite impossible to quote you the size of system that will meet your goals without understanding your individual project site and needs. People who ask this question to me have not done enough research and typically indicate that they are just starting to explore solar power. More than often I lead customers who ask that question to the solar power calculator since it helps them realize all the variables required to figure out how many solar panels you really need. The following reasons are why I can’t give you clear cut answer to, how many solar panels you’ll need for a 1,ooo square foot home: #1 – The size of your home is not as important as how many kWh (kilowatt-hours) per year. This information can be found your last 12 months of electric bills #2 – Typically grid tie solar panels are used to offset your highest cost of electricity if your being charged on a tiered rate structure by your utility company. Solar panels are most cost effective if you use them to stay out of consuming electricity in higher tiers. Therefore not always do people purchase a system that “eliminates their entire bill”. #3 – Your location matters, in particular if there is shading due to trees, vents, chimneys, other buildings..etc. You’ll need more solar panels to meet your goals if you have to compensate for unavoidable shading. Different places across the world have variances in the number of sun hours they receive per day, which has an influence in the number of kWh you can generate per year in your location. Also the orientation #4 – what’s the intent of your solar electric system? Is it just to get started? Some people are satisfied to get started with a small solar electric system and then add more panels to their system later to keep the upfront investment of the system as low as possible to get started. The great aspect of a solar electric system it’s completely customizable to your requirements, particularly your budget. I hope this post highlights the most important key points that need to be analyzed before you can figure out how many solar panel you’ll need. got any...

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economic recovery act of 2009 helps you buy solar

The American Recovery and Reinvestment Act of 2009 passed earlier this year resulted in historic events for the solar power industry. But I noticed that many people out there are still not aware of the benefits. Today I want to highlight the key benefits this legislation has brought to people and organizations who choose to invest in solar panels. tax paying corporations now qualify for a 30% federal tax grant in lieu of a tax credit. A “tax grant” works similar to a rebate in which the U.S. Treasury Department will send a corporation 30% cash payment based off the final cost of the system. This is a limited time offer, only solar electric systems which commence installation before the end of 2010 will qualify. 50% bonus depreciation has been extended for corporations who install solar panels by the end of 2009 $2,000 tax credit cap has been eliminated for solar hot water systems, now solar thermal panels can qualify for the full 30% tax credit. There are many more provisions in the law that helps develop renewable energy technology, SEIA (solar energy industry association) has put together an executive summary that’s really helpful, check it out...

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