Courtesy Better Energy Systems/Flickr
Using the sun for more than just growing your fruits, vegetables and herbs can be a great sustainability step on your urban farm. However, numerous issues might put a damper on permanent photovoltaic (PV) systems that generate electricity directly from the sun. Perhaps you don’t have enough sunny space, lack access to a rooftop, or you live in a place where solar incentives are limited.
Getting a portable PV system can be a better choice. Rather than power your entire home, small portable PV systems provide a convenient and accessible source of electricity to keep a few of your electronics going temporarily when you’re on the move.
How Portable Solar Power Works
Like a permanently mounted PV system, a portable solar-electric system use one or more solar panels (also called “modules”) to transform sunlight into electricity. Most systems include a battery to store the generated electricity, plus assorted wires and adapters to connect the different elements together and to your electronic equipment. A charge controller is included with larger systems to optimize battery and panel performance.
Maybe the most important element of portable PV systems is the carrying case, usually a backpack or bicycle bag for practical transport. If the system is large and heavy enough, the carrying case could be a handcart or vehicle trailer.
While the solar modules are relatively lightweight, the batteries are not. The more solar panels you have, the larger—and heavier—the battery must be to store the electricity generated.
Like any PV system, the effectiveness of generating electricity comes down to the availability of direct sunlight. You need to be able place the solar panels directly facing the sun. They work best if you can adjust the pitch of your modules to be perpendicular to the sun and follow its path across the sky throughout the day. Unfortunately, placing a portable PV system next to a bright, sunny window won’t cut it. It needs to be outside in direct light.
Of course, the amount of electricity needed varies with the device individual device, as well as the duration and scope of its use. As many of us have discovered, there’s nothing like a graphics-intense video game on a laptop to quickly drain a battery. Beyond the scope of the device, many technical issues are also related to energy loss in conversions or with inverters, as well.
Choose the Right Size
Power potential of PV systems is measured in watt-hours and is one general way of comparing them. The system design or inverter capability will determine what type of equipment you can run with your portable PV system. The amount of watt-hours in your battery (or batteries) determines how long you can run your appliances. Your challenge is to figure out what size system you need.
The smallest PV options are quite compact. For the pocket-sized Classic2 from Solio, simply unfurl the three small modules, insert a pencil through a hole in the center and face it toward the sun outside on a bench or patio to recharge the lithium battery inside its polycarbonate case. Solio’s flat Xcellerator with Hub accomplishes about the same thing. Both 5-watt units run about $100 each.
With a 6-watt “Pocket Panel” from PortableSolarPower.biz, you can recharge a cell phone, smartphone or e-reader by hooking fold-up modules to your phone through a USB port. Use your phone on a sunny day, and charge it at the same time with the Pocket Panel, no batteries needed. These types of nonbattery systems start around $90.
Folding to the size of a book, the Guide 10 Plus Adventure Kit from GoalZero is a 7-watt system, featuring a AA rechargeable battery pack, USB input and LED flashlight; it runs about $125. The 1.5-watt USB+AA system made by PowerFilm Solar includes a small, thin-film array that charges two AA batteries in four hours or less and folds down small enough to fit in your pocket. Well-suited for a smartphone, this USB solar charger runs about $100.
To recharge a couple of small electric devices, the slightly more expensive Solargorilla from Powertraveller may do the trick. Basically a PV module encased in rubber, the Solargorilla recharges USB-compatible gadgets and provides a 20-volt power socket for laptop recharging. These run about $240.
For keeping your cell phone, smartphone, tablet and laptop consistently charged, you’ll need a 10- to 25-watt system that comes with a more substantial battery storage capacity. Because your portable devices have different energy needs and varying connection ports, most of these PV systems include a pack of adapters designed to allow you to recharge your specific device. Some of these systems also provide the means to recharge the PV system’s battery from vehicle cigarette lighters or wall outlets. This added power and function still comes with an affordable $300 to $400 price tag.
Put It to Work
To figure out which portable PV system is right for you, you’ll need to sort out your intended goals for the system. It’s all about the amount of energy, or load, needed to power a particular device. Some require a large amount of immediate electricity to start up, while others demand a nominal, constant amount of energy during operation.
There’s a huge difference in portable power options—in cost, energy capability, storage capacity, size, weight and ease of portability—from keeping a cell phone topped off to covering your family’s basic energy needs during an emergency. The key for portable solar power to be effective is matching the demand of your devices with an appropriately sized system.
Portable solar power allows for the freedom that comes with our increasingly mobile and wired society. You just need to select the system that’s right for you.
Learn more about solar power on UrbanFarmOnline.com:
- Lease Solar Panels
- DIY Solar Oven
- Kentucky’s First Solar-Powered Hospital
- Green Zoo Builds Urban Solar Canopy
- Gas-Free Urban Transportation
About the Author: John Ivanko co-authored ECOpreneuring (New Society Publishers, 2008), Farmstead Chef (New Society Publishers, 2011) and Rural Renaissance (New Society Publishers, 2004) and operates the award-winning Inn Serendipity, completely powered by the wind and sun.