Advantages of Small Scale Solar
Some people believe that installing a home solar generating system is an all or nothing proposition. You either “go solar” in a big way or it’s not worth considering. However, this article will show that even the smallest solar generating system can provide huge advantages in terms of providing emergency power when you need it.
PART II IN A SERIESThis article represents Part II the our exclusive series, “Home Grown Energy.” If you missed Part I, go here and read Home Grown Energy.
In this article, we’ll explore the relative merits of two types of “small scale” solar generating systems, namely permanent vs. portable systems. The intent of this article is not to tell you what type of system to buy, or how to install it. The purpose is to illustrate what is possible with small scale solar, based on my own experience. Hopefully, the information you gain from this article will facilitate your discussion with a professional solar installer.
Option #1 Permanent System
‘Whole House’ Solar for $2,000* *Equipment cost, excluding laborThe capacity of this “starter” system is enough to power lights, most power tools, small appliances, TV’s and so forth. As your appetite and interest in solar energy grow, you can easily add more solar panels to the core system. Our example system consists of:
• Six 100 watt solar panels (monocrystalline), 60 amp charge controller, cabling and connectors $949
• Three 114 amp hour deep cycle batteries $300
• 2,500 watt modified sine wave power inverter $200
• Generator transfer switch $382
• Gas generator (1,400 running watts) $169
Why Do You Need a Gas Generator?During periods of cloudy weather when solar energy is not available, a gas or propane generator can be used to power various tools and appliances while also charging your storage batteries. I bought a small, 1,400 watt generator on sale for $139.00. Although you may prefer a larger generator, this small unit suits my needs. It fits easily in my car should I need to take it somewhere.
Gas generators can be difficult to start in cold weather. In winter I can carry this small unit indoors to let it warm up to room temperature. Then I take it outdoors and it usually starts with one pull.
NEVER run a generator inside living areas, or in the garage or basement. Always run it outdoors, far from dryer vents and widows where exhaust gas may enter the home.
Generator Transfer SwitchOne thing that a solar panel system and a gas generator have in common is that both can take advantage of an extremely useful device called a Generator Transfer Switch (GTS). Connected directly to your home’s electrical panel, the transfer switch enables you to:
• Legally feed your generated power into your home’s existing wiring.
• Leverage your solar system’s power. A GTS enables you to use your small solar system to power appliances anywhere in your home, although not necessarily at the same time. You simply flip switches on the GTS to select those circuits that you wish to power with solar energy. When you “switch on” solar for a particular circuit, you automatically switch off grid power to that circuit. The photo at right shows a GTS, which is wired directly to the home’s circuit breaker box.
There is an alternative to the transfer switch, which is called an generator interlock. Although it is less costly, it does not provide the ability to direct power to individual circuits as easily as a transfer switch. Finally, installing a transfer switch eliminates having to run extension cords from your solar or gas generator to appliances and lights that you wish to power. The last thing you want to do in an emergency is to create a fire or tripping hazard that results in bodily injury.
Qualified Electrician Required!Because you are wiring your solar system into your home’s existing electrical wiring, you should have a qualified electrician install the generator transfer switch. Codes may require that an electrician oversee other aspects of your solar installation as well. To get the professional help you need, here are two possible approaches that you can take.
A Note About Inverters
The inverter included in our parts list is a "modified sine wave" inverter, which will power most appliances and power tools without a problem. However some sensitive electronics may have an issue. An upgrade to consider is a "pure sine wave inverter" which provides power that more closely approximates that of the power grid.
Plan ATalk to a local solar installation company; there are lots of them around these days. Explain the small system that you have in mind and indicate that you are open to the possibility of expanding the system. They may be willing to work with you in the hope of eventually installing the larger system. Their knowledge of large-scale systems can help ensure that most of the components they install for you now will be compatible with the expanded system you may choose to install at a later date.
Note that the solar company will likely try to talk you into installing more solar panels and batteries than are suggested in this article. They may even propose a large “net metered” system that doesn’t require storage batteries (not recommended, since that means no backup power).
Keep an open mind and listen to everything they have to say. It’s all part of your “solar education.”
Plan BTalk to a licensed electrician. First, explain that you want him (or her) to install a generator transfer switch. The electrician may already have experience installing such devices, since people have been using them for years for their gas generators.
After some conversation, explain what you want to do in terms of the solar system itself, and that you would like assistance on that end as well to insure that the system is properly grounded and so forth.
You can usually download installation manuals from the manufacturer’s website, which explain the installation process for various system components. Installation of these components is generally a simple process.
Explain that you can purchase all of the solar components required, and ask the electrician to review your list of materials before you purchase them.
If the electrician has no solar experience, that could prove to be a good thing. He might be willing to cut you a deal to get his first solar installation under his belt!
Battery ConsiderationsThe recommended storage batteries in our example system are three 114 amp hour deep cycle batteries. Never use car batteries in your solar installation; they will probably be dead in a few months. Deep cycle batteries are designed for hundreds of recharging cycles and should last for years.
Some batteries that are called “deep cycle” are actually hybrid batteries that are used for starting engines and limited deep cycle applications. To identify a “true” deep cycle battery, it should have an amp-hour (Ah) rating shown on its label. Avoid batteries that make reference to “cold cranking amps.”
Note that I chose to use inexpensive deep cycle batteries in this example, which are available at local big box stores for about $100 each (compared to top-of-the-line batteries costing $300 or more).
Can Those Incandescents!
Before installing any solar energy system, you’ll want to make sure that electrical devices in your home are not wasting energy. At the top of your list should be getting rid of those old-style incandescent light bulbs and replacing them with energy-efficient LED’s. Check out the variety of LED bulbs available at www.eepsales.com.
My rationale for using inexpensive batteries is this: Should you decide to upgrade your system in a few years, you’ll have to replace the batteries because you can’t connect old batteries to new ones. Since you only paid $100 for each battery, it shouldn’t be a big deal when you have to chuck them. You can probably get money for the lead cores when you return the old batteries to the dealer.
Get Rid of ‘Energy Vampires’
Some computers, TVs and other household devices continue to draw power even when they are turned off. A ‘Kill A Watt’ meter can hunt down these “energy vampires.” Once identified, you can connect these devices to power strips that enable you to switch off power to the devices when not in use.
The picture on the left is a frame design that works well for a simple ground mounted system. The frame can be made of wood, metal or PVC pipe.
For roof mounts it is best to mount the panels on a rack, so that you don’t have to drill as many holes through your roof shingles. Racks also allow ventilation under the solar panels; solar panels produce less electricity when they get hot.
Option #2 Portable Power Station
‘Power to Go’ for $500 to $2,000One very easy way to get involved with solar power is to buy a “portable power station.” These compact units have the battery, inverter, volt meter and other components built in. The portable units are often sold with one or two small solar panels. Power stations can be charged with AC power as well.
Portable power stations typically have AC, DC and USB power ports. While most of these portable units don’t have the capacity to run a table saw, they do a great job of powering lights, radios, cell phones, laptop computers and even small TVs and DVD players. Larger, more expensive models can power such things as portable refrigerators and most power tools.
Besides emergencies, portable power stations are great for recreational use, such as camping.
5¢ Solar Alignment ToolWhen using a portable power station you can tweak up to 20% more energy from the system by periodically adjusting the solar panels as the sun tracks overhead.
Let’s say you’re at the beach, and your portable power station is powering a refrigerated cooler. Just prop up the solar panel against the cooler, picnic basket or whatever else is at hand. Next, take an ordinary pencil. With one hand hold the pencil, eraser side down, on the solar panel so that the pencil is perpendicular to the surface of the panel. With the other hand, adjust the angle of the panel until the shadow of the pencil disappears; this indicates that the panel is in optimal position facing the sun.
For larger permanent installations, solar tracking systems are available that use GPS and other means to automatically align panels to the sun as it moves overhead. Solar tracking mechanisms aren’t absolutely necessary, since most solar panels have dimpled surfaces to help capture the sun’s rays at various angles even when the panels remain stationary.
Living Off the Grid Even with a small solar energy system, you can experience the challenge of “living off the grid” whenever you wish. Just use the Transfer Switch to toggle the grid on and off at will, keeping the sun, and the power company, at your beck and call.
For more information about solar energy visit: www.energy.gov.
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