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Solar Power Purchase Agreements

If you are looking for the benefits of solar electricity with little to no upfront cost, minimal risk, and no maintenance responsibilities, you may want to look into a Solar Power Purchase Agreement (SPPA).  The sections below begin with a short and simple summary under each heading, followed by a more in-depth explanation to aid in understanding this solar option. What is a normal Power Purchase Agreement (PPA)? A PPA is an agreement in which the customer agrees to buy electricity from a power source at a particular rate per kilowatt-hour (kWh). Everyone who buys electricity from a utility company such as PG&E or Southern California Edison enters into a PPA without much choice in the matter.  You agree to pay for the generation, transmission, and distribution of the electricity from their power plant in a tiered rate schedule per kWh for an indefinite amount of time.  Typically, these rates increase every year in proportion to the utility’s increasing costs. The Public Utilities Commission (PUC) sets a limit to how much profit these companies make every year, so their increasing costs are caused by anything from increasing salaries and pensions to making repairs caused by weather, accidents, or the aging infrastructure of the grid.  Whatever the cause of the increasing cost of electricity, homeowners have little choice but to continually pay more for what they use, or use less grid power.  The latter choice is where solar options (purchase, lease, or PPA) come in. What is a Solar Power Purchase Agreement (SPPA)? An SPPA is similar to a PPA, except that the source of power is located on the homeowner’s property, and the agreement often includes a contracted increase in rates as well as an amount of time the user agrees to purchase the power. An SPPA is an agreement in which a third-party owns, operates, and maintains the photovoltaic system, and a host customer agrees to have the system installed on their property. Homeowners simply purchase the electricity utility-style from the solar services provider for a predetermined period rather than purchasing the system itself.  This framework is referred to as the “solar services” model, and the developers who offer SPPAs are known as solar services providers.  There are several other players involved in this model. The utility company continues to provide part of the host customer’s electricity.  The equipment manufacturer provides the hardware for the system, which the installers implement and maintain.  Investors, such as US Bank, provide the capital for the equipment.  A seperate special purpose entity manages the solar electricity payments, tax benefits, depreciation, ownership and leasing between the solar services provider and investors. SPPAs enable...

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Pure Sine Wave Inverters vs. Modified Sine Wave Inverters
Jun19

Pure Sine Wave Inverters vs. Modified Sine Wave Inverters

True Sine Wave or Modified Sine Wave?Because the AC electricity from the electric grid is in the form of sine wave, the inverters we use aim to produce a current that is as close to sine wave as possible.  While modified sine wave inverters present an inexpensive alternative, there is no comparison to the clean, undistorted sine wave provided by pure sine wave inverters.   Pure Sine Wave Inverter    A pure sine wave inverter, also known as a true sine wave inverter, produces a clean, undistorted electrical output.  Depending on the manufacturer of the product, pure sine inverters have a perfect sine wave output that’s in phase with the AC grid of the utility company.  Because of the sinusoidal form, pure sine wave inverters are used for grid-tie solar systems and work for virtually any AC load.  Cotek SK3000-148, 3000 Watt 48V Pure Sine Wave Inverter Because they produce no harmonic distortions in the frequency, pure sine wave inverters allow any electronic device to function well without overheating or creating an irritating “buzz” sound.  Though pure sine wave inverters are undoubtedly the best and most versatile kind of inverter, they are more expensive than modified sine wave inverters.   Pure sine wave inverters are necessary for highly sensitive products such as digital clocks, audio equipment, and video-game consoles.  As a general rule of thumb, if you’re powering any electronics, you’ll probably want to stick with a pure sine wave inverter.  The image below displays the difference between a pure sine wave and a modified sine wave.   Modified Sine Wave Inverters   The cheaper alternative to a pure sine wave inverter is a modified sine wave inverter.  A modified sine inverter converts DC electricity to a nonsinusoidal AC wave that is “modified,” or distorted.   When an inverter produces modified sine wave, the voltage output (represented in the Y axis of the image) essentially jumps from zero volts to positive, where it plateaus and drops back to zero, to negative voltage, and then back to zero again. This is signified in the image by the squared edges seen in the modified sine wave, which is contrasted by the smooth oscillation of a voltage that is produced by a pure sine wave inverter.  The modified sine wave is a stepped waveform that is designed to mimic a true sine wave.  Because it is not a clean form of energy, modified sine wave does generate a certain kind of interference called harmonic distortion (though not as much as a square wave). Modified sine wave inverters can work for the majority of low-end appliances, but take caution when using them for your...

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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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