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Sizing Your Solar Power System
Oct10

Sizing Your Solar Power System

You know you want to install solar, but how much solar do you want to install? There are many factors to consider when making decisions about system size. The system size will be dependent on how much energy you want to generate. If you are doing a grid-tied system, you will start by looking at your electric bills. You should add up the last 12 months of electric bills so you have your annual usage. If you only use one month or one season, you can end up way off because your electric needs can change dramatically from summer to winter.  Sample Electric Bill – look for the kWh! Once you know your annual usage, you should ask yourself some questions. If you have solar on your roof and you’re no longer paying crazy high prices for every kilowatt hour (kwh), what might you do differently? Would you turn the air conditioning setting down a couple of degrees so you never break a sweat? Would you buy an electric car? Do you have any other plans like installing a swimming pool? If you answered yes, then you will want to add some kwh to your current usage to account for the additional air conditioning run time, the electric car, the swimming pool or whatever else you might dream up that will use extra electricity.  The next big question is how much of this projected energy usage do you want the solar to offset. This will depend on your electric rates and how your electric provider deals with net metering. If your local utility company gives you full retail credit for every kwh that you feed into their system then you should consider a system that generates close to 100% of your projected usage. Going over 100% is generally not beneficial as most utilities will not pay much for the excess power generated over the course of a year.  Sample electric bill before and after solar If you are sizing an off-grid system, you will have to do a little more work to get your projected usage.  You will need to make a list of everything that will use electricity. Then you have to determine how many watts each of those items will use and how many hours you plan to run them. You can multiply the watts by the hours to get watt hours. Divide the watt hours by 1,000 and that will give you the kilowatt hours (kwh). Now you know what you need to generate but that still doesn’t exactly tell you what size system to install.  Because there are so many factors (like location, weather and...

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How Solar Works
Oct09

How Solar Works

If you look at the roofs around you, you will see that more and more people are installing solar but what is it all about and how does it work? The point of installing solar is to save money, but that is the end result and we should start this story at the beginning.  The solar panels are officially called photovoltaic modules. Photovoltaic is really hard to say, so most people call them PV modules or just go with the commonly accepted and less technical name “solar panels”. The solar panels should be installed at a good angle to the sun which is generally going to be south. East or west also works with west having an advantage of producing more energy in the afternoons which is desirable if you are on a Time-of-Use electric rate (you can see our other articles for more details on that). Most people install the solar panels on the roof but if you have the space, you can install them on a ground-mount rack.  Roof vs ground mounted solar When the sun hits the solar panels, they produce DC electricity. When you buy the solar panels, you will also want to get an inverter (or microinverters) to convert the DC power to AC power. In a Grid-tied system (which is the kind you want for your house unless you are not hooked up to the electric company), that inverter (or microinverters) will be connected to the main service panel of your house.  The power from the solar will flow to all the lights and appliances in the house and any excess power that you don’t use will flow out to the grid, spinning your meter backwards. Your electric company will give you credits for that energy that you give them and apply those credits to the energy that you use at night when the solar isn’t producing.  The amount of credit that you get for the energy you feed into the grid depends on your utility company. In some places customers get full credit, so for every kilowatt hour (kwh) you feed in, you get a kwh back later. In other places, you get less than full credit, but it is still a worthwhile amount. In the end, no matter where you are, every solar panel will lower your electric bill a little bit more which is why solar is a great investment. But, there is a limit to the savings. You can only save the amount of your electric bill. Except for very unusual circumstances, you will not be paid more than a few pennies, if anything, for excess energy generated over...

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Sunshine on a Cloudy Day – Why Solar Still Works in Clouds, Rain, or Shine
Sep30

Sunshine on a Cloudy Day – Why Solar Still Works in Clouds, Rain, or Shine

When it comes to generating power from the sun, there’s a misconception that home solar systems don’t work in cloudy weather. However, ask anyone who’s ever gotten sunburned when it is cloudy out, and they will tell you a different story. That’s because solar radiation, better known as Ultra Violet rays, can penetrate clouds and produce energy. Depending on the type of cloud cover, solar panels might produce 10-25% of their rated wattage. Thanks to significant increases in panel efficiency over the last decade coupled with their declining prices has allowed homeowners to install more panels for less, reducing the weather’s gross impact in performance. Solar panel efficiency has increased over time Solar panel pricing has decreased over time Famously gray cities such as Seattle and Portland are among the top 20 leaders in America in terms of solar capacity. Washington’s generous payback incentive and net-metering policy have helped encourage the adoption of solar, allowing homeowners to benefit from reduced electric bills and a greater confidence in their self-reliance should a power outage occur.  Similar to cloudy days, solar panels also work in the rain. Counter intuitively, the rain can actually benefit panels, by washing away dust and dirt debris on panels, allowing them to perform better when the sun peaks back through.  Homeowners planning for solar in a cloudy, rainy, or even seasonally snowy environment, should consult with a solar expert to size their system and design a solar array specific for their geographic location. Basic calculations to gauge a system’s size can be made with the following formula: Array Size (kW) = (Annual kWh usage) / (365 days/year) / (Solar Hours – 1.5/day) / (0.82 derate factor)  How Many Sun Hours a Day Do You Get?Zone 1      6 hoursZone 2      5.5 hoursZone 3      5 hoursZone 4      4.5 hoursZone 5      4.2 hoursZone 6      3.5 hours Since systems will usually yield less energy during the winter months, its safe to subtract ~1.5 solar hours to account for decreased sunlight and ensure your system will meet all your power needs. Home solar supplier GoGreenSolar carries panels that are best suited for cloudy, rainy or even snowy conditions —  Hanwha Q Cells, NEO and LG Solar are among the top performers in adverse conditions. To figure out what solar panels and system array is best for your home call for a free consultation:...

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Best Battery Types for Solar
Aug06

Best Battery Types for Solar

Installing batteries with solar is necessary on off-grid systems if you want power at night and also becoming more popular on grid-tied systems. Choosing what type of batteries to install can be a bit complicated so this article will cover the basics for you. The batteries that are most commonly used for solar are lead acid and lithium chemistries. No matter what, you will want to choose a “deep cycle” battery that is rated in amp hours (AH) and not a starting battery that is rated in cold-cranking amps (CCA). Car batteries are great for providing a lot of amps really fast to start a motor but they don’t do well with the long, slow draw of running the lights, TV and refrigerator in your home or off-grid cabin. If it is the zombie apocalypse and car batteries are all you can find, they will work but they aren’t the best choice for the application. Let’s start with lead acid batteries which can be broken down into the two basic types of flooded and sealed. Flooded batteries will be less expensive but they require maintenance and ventilation. When you purchase flooded batteries you are committing to adding distilled water to the batteries on a monthly basis. Without the added water, they can run dry which means they lose all charge and are likely to never hold a charge again. If you are not good at regular maintenance, buying these batteries can be a costly mistake. Even if you get the self-watering kit that does the work for you, you still need to maintain water in the reservoir and check to make sure the kit is correctly maintaining the water levels high enough. The ventilation requirements are also very important to consider because these batteries will vent hydrogen gas which is poisonous and flammable. Installing these batteries in your living space or anywhere there might be an open flame could have some nasty results. Sealed lead acid batteries are a little pricier but solve the unpleasant issues of the flooded batteries. You do not have to add water to them, they do not vent large amounts of poisonous, flammable gas and they can also be installed on their sides without worries about hazardous chemical leakage. The most available types of sealed batteries are gel and AGM. These are also often referred to as VRLA for Valve regulated lead acid batteries. Even within the categories of sealed and flooded lead acid batteries, there are different technologies being employed. For example, the Outback EnergyCell Non-Carbon batteries are a type of enhanced sealed lead acid batteries that have improved charging efficiency and a...

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Optimize Your Solar Production
Jul24

Optimize Your Solar Production

The price of solar panels has come down significantly but that doesn’t mean you still shouldn’t try to get the most energy possible from them. The key to optimizing solar panel production is in the installation. We all know to install the solar panels with blue side facing up, but there is a little more to it than that. It is all about the direction the solar panels are facing (often called Azimuth by people in the solar industry) and the tilt angle which would be the angle from horizontal. If a solar panel is oriented so that the sun hits it directly at a 90 degree angle, it will produce the most possible power but the sun is a moving target. Not only does it move across the sky throughout the day, but it is higher in the sky in the summer and lower in the sky in the winter. Many people don’t realize in North America in summer, the sun rises in the Northeast and sets in the Northwest. In the winter that becomes is Southeast and Southwest. It only rises due East and sets due West on the Equinoxes in March and September.  In order to keep up with the sun, many people think they should make the solar panels move. Solar panel tracking systems have been around for a long time, but they aren’t necessarily practical. For one thing, it would look pretty silly to have one on your roof, not to mention the structural and wind load issues you would be dealing with. Ground-mounted solar tracking systems are a possibility, but you are adding moving parts that typically have 5 year warranties and lots of maintenance to an otherwise passive system with a 25 year warranty. The bottom line is that even if you have room to install one in your yard, a solar tracker will be expensive and a pain in the neck. You might gain 20% production, but it would be cheaper and easier to just install 20% more solar panels. So now we are back to talking about what fixed orientation gets you the best bang for your buck. The short answer is to face you solar panels due South at tilt angle slightly less than your latitude. That means if you are as far South as San Diego it would be a tilt angle of 32 degrees and if you are up North in Seattle it would be a tilt angle of 47 degrees. If you want to be very particular about it, a lower tilt angle will give you more power in the summer when the sun is higher...

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Solar Panel Certifications Demystified
Jul17

Solar Panel Certifications Demystified

With dozens of brands of solar panels on the market, choosing which one to buy can be a conundrum. One of the things you that may help you navigate this field is to understand the various certifications that are given to solar panels and all the acronyms that go with them. UL (Underwriters Laboratories) is a global independent safety science company with more than a century of expertise innovating safety solutions. The first thing you need to know is the difference between a “standard” and a “certification”. Standards are design qualifications written by entities like Underwriters Laboratories (UL), International Electrotechnical Commission (IEC) and International Organization for Standardization (ISO) whose acronym makes better sense in other languages. When a solar panel receives a certification, it means that a recognized, approved lab has tested that solar panel to make sure it meets certain standards.  UL 1703 is the set of standards for safety for flat-plate PV Modules Let’s look at UL 1703 as an example. Officially published by Underwriters Laboratories, UL 1703 is the set of standards for safety for flat-plate PV Modules (aka the commonly used solar panels with the glass on the front). Cities and counties in the United States will only provide installation permits for systems that have solar panels that have the UL 1703 certification. This means that a manufacturer must send their solar panels to a Nationally Recognized Test Laboratory (NRTL) like Underwriters Laboratories, Intertek, TUV or CSA Group to have it tested. If it passes the test, that lab will provide a certification that the solar panel meets the UL 1703 standard. This process is also called UL listing and when the solar panel gets its official certification the manufacturer can say it is UL Listed. A UL Listed solar panel will have a special “mark” on its label from the NRTL that certified it. TÜV Rheinland is the leading provider of product testing and certifications for the worldwide marketplace.  While getting the UL 1703 Listing is a requirement, the solar panel manufacturers can step up their game and have the lab also test for other standards like IEC 61215 standards for durability and performance for standard monocrystalline and polycrystalline PV module. The IEC 61646 is a similar set of durability and performance standards for thin film PV modules. There are also very specific standards like IEC 61701 that includes salt mist corrosion tests (which you should look for if you are installing your solar panels on your beach house) or IEC 62716 that includes ammonia corrosion tests (in case you are installing your solar panels in agricultural environments).    PVEL is the independent lab for the...

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