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Grid-Tied and Off-Grid Solar 101
Jun28

Grid-Tied and Off-Grid Solar 101

Will I need batteries for my solar system?  How much does it cost to go completely off the grid? Let’s take a look at main differences is between a “grid-tied” solar system and the less common “off-grid” solar system. Grid-tied Solar Most photovoltaic (PV) systems are connected to the utility grid, hence the name “grid-tied.”  When your solar system is connected to the grid, you still have access to energy after dark without batteries.  Your grid-tied system simply pulls the electricity you need from the utility grid.   Here’s how it works:   A group of solar panels, known as the array, generate direct current (DC) electricity.  An inverter changes the DC electricity into alternating current (AC) electricity, which is the grid-quality electricity that comes from the power outlets in your home. When the grid-tied system produces more energy than your home is consuming, the excess electricity is sent into the utility grid, spinning your meter backwards as credit toward your next electricity bill.  When your load requirements exceed the electricity being produced by your photovoltaic (PV) system, your home will draw electricity from the grid.  This is called net metering. Grid-tie solar systems are a cost-effective way to reduce your net energy consumption. Grid-tied solar systems are ideal for those whose utility provider bill them according to a tiered rate structure –  where rates you pay are higher when you’re consuming more energy (kWh). Grid-tied solar gets you out of the higher tiers on your electric bill to save you money. If you need help designing a grid-tied solar system, request a no obligation quote today. Will I still have power during a blackout? Not with a grid-tied PV system.  You’ll still experience blackouts when the power goes out in your neighborhood because your are connected to the utility grid.  Sending electricity into the grid during a power outage would be especially dangerous if the utility company has workers repairing power lines. For most people, a power outage here and there isn’t too much of a concern.  Just keep your refrigerator closed and charge your iPhone with a JOOS Orange Portable Solar Charger. But what about Armageddon? Or the zombie apocalypse?! I’ll need power to fight off the living dead! If you live in an area that is plagued by frequent blackouts, hurricanes, or maybe the living dead chewing on power-lines, battery backup may be an option for you. Keep in mind, battery backup is for critical loads, or the appliances that are imperative to survival.  So you really can’t blast the AC and leave the television running 24/7 in the aftermath of a natural disaster. In most cases,...

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Nitty Gritty Details

What’s the Difference Between a Solar Lease and a Solar Power Purchase Agreement? For those of you who are comparing different options for going solar, your main choices are purchasing a system as an addition to your home, buying a new or upgraded home with solar already integrated as a feature, buying your electricity utility-style through a solar power purchase agreement (SPPA), or signing up for a solar lease.  The latter two choices are very similar and require a closer look to distinguish one from the other.  (For a comparison between purchase options and SPPAs check out this article.) Sleek solar tiles from Applied Solar. To start off, it’s important to cover the basics of how both financing models work.  The SPPA option has been described in detail in this article, but for now it’s best just to cover the practical details of how these agreements function: SPPA stands for “Solar Power Purchase Agreement.” The SPPA provides the benefits of solar with little to no upfront cost (usually between 0-$2000). The agreement is usually termed for 15-20 years, and is transferable to another owner or home. A solar services provider charges a set rate per kilowatt-hour. The electrical rate can remain flat, but is more commonly contracted with a fixed annual increase of around 3%. The solar utility maintains, monitors, and insures the system over the term of the agreement. The solar utility that purchased the panels benefits from the Federal Investment Tax Credit (ITC) and any Renewable Energy Credits (RECs) that are generated. The installer (sometimes separate from the solar services provider) receives any available money from state rebates (which means the homeowner didn’t have to pay part or all of the cost of installation). Most SPPAs have options to buy the system throughout the term of the agreement or to pre-pay for all of the remaining electricity at a discounted rate while deferring the responsibilities of ownership to the solar utility. The home is always tied to the grid, so any excess electricity used beyond what the panels produce is purchased from the grid utility. Homeowners that want to pursue this option must be properly qualified with a minimum amount of monthly electricity usage, proper sun exposure and roof orientation as well as excellent credit (usually FICO 680 or better). A handy illustration of how an SPPA integrates into the grid electricity system. Next up, the solar lease has become a popular option because, like the SPPAs, homeowners don’t have to buy a system.  They just make a monthly payment and receive the benefit of clean electricity. Here’s the skinny on leases: There is commonly no upfront cost....

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Volunteer with GRID Alternatives!

Established in 2001, GRID Alternatives is a nonprofit organization that provides low income communities access to solar energy.  GRID Alternatives was founded by two engineers who are driven to make clean energy accessible to the low-income communities that need solar energy the most.  The people at GRID Alternatives are on a mission “to empower communities in need by providing renewable energy and energy efficiency services, equipment and training.” In addition to helping families produce their own solar energy, GRID Alternatives provides a unique educational experience for its volunteers.  Unemployed and underemployed individuals from the community are encouraged to cultivate a valuable skill-set through volunteer and team leader programs. By working on installations for the Solar Affordable Housing Program, volunteers get hands-on experience and networking opportunities that they couldn’t get anywhere else.  Through GRID’s Team Leader program, volunteers have the opportunity to become certified PV installers with the North American Board of Certified Energy Practitioners.   A GRID volunteer can use this real-world experience to get their foot in the door of businesses in the solar industry. The unique environment created by GRID Alternatives draws in people from all walks of life. Environmental activists, students, engineers, and professionals in the solar industry are just some of the people that volunteer with this nonprofit organization.  Everyone comes together to help the community, learn new skills, reduce CO2 emissions, and sweat bullets in the California sun. I recently had the opportunity to go on a volunteer installation with GRID Alternatives.  The mission was to install a 2.3 kW AC system for a low income home in Long Beach, California. The first day of the installation began at 8:30 am on a overcast Tuesday morning.  Shortly after the last volunteers arrived, we introduced ourselves and the project supervisor went over some basic safety precautions. While the ground team was busy prepping and splicing the ProSolar rails, several of us got up on the roof to determine how the array could be configured in compliance with the regulations in the city of Long Beach.  As the morning clouds burned off, we quickly realized that the sun would not spare us.  After taking measurements and marking the lay-out that was established by GRID team leaders, we drilled into the rafters where the ProSolar FastJack Stand-offs would soon be mounted.  Around each hole that was drilled, we cut a few inches of the surrounding roof to make room for the flashing.  After bolting the base of the standoff with caulking and inserting the flashing under the top layer of the roof, we screwed in the ProSolar FastJack Stand-off.  We then sealed a fitted washer over the flashing...

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How Long Will Solar Modules Last?

What is the life expectancy of a solar module?   When customers invest in a solar system, they often wonder how long their modules will continue to provide energy and how much they will yield over time.   Over the years, all solar panels will degrade somewhat, but crystalline silicon panels have a much slower rate of degradation than thin film modules. This means crystalline modules will work better for longer.    It’s common for crystalline modules to come with a warranty for twenty to twenty-five years, guaranteeing that the panels will be effective throughout the duration of the warranty.   For a module to be deemed “effective” by most manufacturers, it must operate at least 80% of its rated peak output.     Given the anticipated loss of efficiency between 0.5% to 1% every year, manufacturers are able adjust their warranties according to the calculation of a module’s expected performance over a period of time.  The module’s peak output will usually decline to about 80% at the end of a the two-decade warranty.  This is why crystalline modules are frequently guaranteed for this time-frame.    A solar module does not suddenly become useless, but instead has an output that steadily declines over a number a decades.  For this reason, a well-maintained, high-quality panel will often outlive its guarantee.  Solar panels can continue to adequately operate for a decade or two after their warranties expire.  There are plenty of solar panels that have been producing energy since the 1980s.  If your system is producing enough energy to meet your needs, there’s no sense in replacing these older panels.    Powerboost Solar Panel Cleaner Solar modules have no moving parts, so they require minimal care to remain functional.  Though other components of a solar system will probably need to be replaced after ten years or so, there are a few things you can do to make sure your solar panels continue to produce energy for a long time.  Be sure to trim surrounding trees that might shade your array.  Regularly remove leaves, snow, or any other debris collected on the modules that might prevent them from receiving maximum exposure to the sun’s light.  You should also clean your panels with some frequency, especially if you live in an area where bird droppings are rampant!  To make this process easier, you can pick up a Solar Panel Cleaning System Kit.   Selecting a high-quality manufacturer will also serve you well long-term.   A dependable manufacturer will be sure to encapsulate the modules’ metal and silicon appropriately, ensuring that you’re not working with faulty equipment from the start.  If your modules aren’t securely encapsulated...

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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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