Campers have used solar energy for decades. Anyone who has hung a black plastic bag in the sun to heat water knows about free, clean solar energy. These days, the possibilities are far more advanced. Campers now have the option of using sophisticated solar panels to generate electricity, a precious resource in any RV parked off the grid.

Since the 1970s, prices for solar panels have dropped 90 percent, and panels have become more durable, lighter, and far more efficient. As a result, they are a great way for RV campers to get additional electricity or backup power.

Solar panels can be used to power appliances in your RV directly during the day or store the electricity in batteries for backup power any time you need it. There are small systems suitable for recharging a cell phone or laptop, 2,000-watt systems that automatically track the path of the sun across the sky, and everything in between. Adding solar electricity can be as simple as propping up a solar panel next to your RV or draping a flexible sheet of durable, lightweight solar film over a tent or awning.

When you use electricity generated by solar panels, you are resting your generator, saving fuel, and reducing noise. Solar panel kits for RVs are available to handle emergency battery charging all the way up to providing nearly all of an RV's power needs. Solar panels have no moving parts to wear out and are simple to maintain. They can be used alone or in combination with other energy sources, and they are silent, reliable, and long-lasting.

How They Work
Solar panels are a product of the photovoltaic effect in which layered materials such as silicon produce an electric current when exposed to sunlight. Metal contacts connecting small cells on the top and bottom draw the current off for external use.

A typical RV solar kit will include one or more solar panels that convert light into electricity, a charge controller that regulates the electricity, and wiring to connect the system to your batteries. The charge controller will prevent batteries from being overcharged once they are full and can act as a meter to show how electricity is flowing.

A good kit will also include mounting structure and hardware for the panel(s). If your RV does not already have a built-in power inverter, getting one would allow you to use battery power to run 120-volt AC plug-in appliances from home. However, appliances that use DC power (direct current) don't need an inverter. Items such as laptops, cell phones, camera batteries, and iPods can be charged directly from a panel.

Ideally, excess energy generated during the day is stored in a battery for later use. The more battery storage capacity available, the more practical a solar charging system can become. Most RVs come with at least one auxiliary battery, but more is always better, especially if you are relying on a power source that might only generate current for 5 hours a day.

Different Types
There is a wide variety of kits available, with various price points and levels of performance. Most are easy to install; producers of the kits we talked to said that 90 percent of their customers handled installation on their own. Solar power systems are modular; more panels and batteries can always be added later.

One way to go would be as simple as storing flat panels in your RV, unloading them when you camp, propping them up in a sunny location and plugging them in. You can move the panels around during the day to keep them in direct sunlight, and then stow them when you break camp.

Having freestanding solar panels is also handy in the sense that you don't have the risk of creating leaks in your roof, as you might when you install permanent panels, and you'll never have to climb up on the roof to clean the panels or re-adjust their orientation.

Price generally depends on size. We found 40x20-inch 65-watt panels that can produce a current of 3.57 amps under optimum conditions for under $400 apiece at retailer Mr. Solar.

For more power, larger Mitsubishi 175 solar modules priced at $720 apiece can generate current up to 7.32 amps. A 12-watt solar module that generates 1.28 amps, roughly 12x13 inches, would cost about $130. A one-watt module would cost as little as $25.

There are even easy-to-store 12-volt flexible solar arrays that can be unrolled in the sun for recharging RV batteries when access to AC power is unavailable. Originally designed for military use, flexible panels are now available to consumers. Power outputs range from 6 watts to 60 watts, and less than half an amp to 2.5 amps.

On the other hand, permanently mounting large panels attached to a bank of batteries is the custom way to go. For example, there might be room to mount six or more 200-watt solar panels on a 30-foot RV. Such an array could provide up to 1.2 kilowatts each hour, or 6 kilowatt-hours in a 5-hour day. We found 205-watt panels for sale at retailer Affordable Solar for $570 each, so they are not inexpensive, but they do generate a considerable amount of current. Those particular panels measure 65x37.5 inches and are almost 2 inches thick.

What You Need
Many RV owners are intrigued by the idea of using solar power for 100 percent of their needs. In some sunny locations, using a robust system of solar panels and batteries might be possible depending on how appliance-heavy your lifestyle is.

Certain high-amp draw appliances, such as air conditioning, generally suck too much power to run on the average solar system, but things like lights, computers, TVs, and game systems for a family are well within the realm of possibility. To figure out what's feasible, estimate your power needs.

We checked with Tyler Brown at Affordable Solar in Albuquerque, New Mexico, who explained how to figure how much wattage you actually use.

"Every appliance has a wattage rating," he told us. "The easiest to understand is to take a 50-watt light bulb. If you run that light bulb for 1 hour, you will have used 50 watt-hours of energy, or 50Wh. Run that same light bulb for 2 hours and you'll have used 100Wh of power. Add up all of the light bulbs in your house, plus the wattage rating on other appliances, and that's how much energy you'd use in an hour. If you can't find a wattage rating, volts times amps equals wattage."

"Once you've figured that out, the next step is to add up the hourly usage and find out how many watt-hours (Wh) you use in a day."

Kilowatt hours are the units your power company uses on your bill, expressed as "kWh used" (1,000 watts= 1 kW/1 kilowatt).

Brown told us, solar panels are rated in instantaneous wattage. So if a solar panel carries a 220w rating, it is capable of making 220wA in one hour. So let's say you are going to use 1kWh a day. Then you'd need a 200w panel getting full sun for 5 hours. Or, you could have 5 panels running for 1 hour to achieve the same.

There is usually an efficiency loss you should account for when sizing a system. So if you need 220Wh, a 220-watt panel isn't going to cut it. 220w is achieved on that panel at the perfect sun angle, perfect temperature, and at the panel output. You will have a loss factor of about .8 through your inverter as well, so take your needed usage and divide it by 0.8. In this case, 220 divided by 0.8 gives you 275w. This means you're going to need to find a panel/system rated at 275 watts.

Battery Backup
Your RV probably already has at least one auxiliary battery, which you'll be drawing on most of the time. Solar panels can help keep that fully charged during the day, but more panels and more batteries will allow you to store more energy.

To estimate how much juice a single battery can hold in watt-hours, multiply the voltage times the amp hour rating on the battery. If you have a 42-amp, 12-volt battery, you get 504 watt-hours. That means you could run a 100-watt light bulb for 5 hours before the battery would be totally dead or five light bubs for an hour apiece. It would be possible to run a 1,000-watt appliance on the same battery, but only for about half an hour.

Another way to add storage would be to add a portable battery, like the Xantrex Powerpack. This is a 60-amp/hour battery on rollers with built-in power inverter, with accessories to make it rechargeable by solar panel. It can supply both AC and DC power and is portable enough to bring power down to the beach, worksite, or campground.

However you do it, you'll want to get as many of the biggest batteries you can to store electricity for use after the sun goes down.

What's Practical?
To find out what solar upgrades can really deliver, we checked in with RV owner Mark Quasius, who shared photos of his setup for this article. He has four 120-watt Evergreen panels on his 42QRP Allegro bus coupled to an Outback MX-60 Charge Controller. For storage, he uses 12 Interstate DCS batteries, rated at 88 amp-hours apiece. He's invested about $3,000, he figures, in hardware and did his own installation. What does he get for his time and money?

"With the residential refrigerator this gives me the ability to not have to worry about running out of juice in any reasonable conditions. It also gives me the flexibility to run the genset to recharge the batteries at my convenience and removes the 'emergency' issue from the equation. It also lets me straddle any quiet time hours easily without having to be present at the coach."

His advice: "To be totally self-sufficient, you need to be a real Scrooge when it comes to using electricity, or else you will need a massive solar system. Solar power isn't for everyone. If you generally camp with hookups it's a waste of money. If you boondock frequently, having a solar panel system will extend your battery runtime and allow you to run the generator less frequently. The big advantage is that you can pick and choose when you want to run the generator set to make it more convenient for you."

So there are limitations. Keep in mind solar panels work on light, not heat, so they do work perfectly well in the winter. As electronic devices, they actually work better in cool weather. However, in the winter, daylight hours are shorter. In snowy climates, the snow must be removed to allow light to hit the collectors.

On a cloudy day, solar cell output might be reduced by half, or down to an even lower output on a very dark day. Shadows, dirt, or leaves falling on the panels will reduce output accordingly.

The energy.gov website has a map of solar power resources. It shows that the Southwest is the best place for solar, but that solar can be used practically anywhere with diminishing returns in the Pacific Northwest and Alaska. Enhancements, such as sun tracking systems, can be used to make the most of solar radiation in those areas where average sunshine is lower.

Maintenance
The panels themselves are generally quite durable with no moving parts, but the frames around them can corrode, so they should be mounted with a slight tilt so that water drains off, rather than puddle and attack the frame. Dust tends to accumulate in the lower corners of any solar panel, which can degrade performance.

When that happens, panels can be kept clean using any non-abrasive cleaner. If output drops, it's more likely that connections at the battery or fuse holders are the culprit than degradation of a panel itself.

SOURCE
Affordable Solar Inc.
800-810-9939
www.affordable-solar.com
Sundance Solar
603-225-2020
www.sundancesolar.com
Mr. Solar
888-680-2427
www.mrsolar.com
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