How can I build a small solar power system for backup power during emergencies?
Putting together a system that provides enough solar power to run a few key appliances during a power outage is certainly possible — and it’s also a fun and educational project.
Small backup solar power systems consist of a photovoltaic (PV) panel or two to generate the electricity, a battery to store the energy, a charge controller to keep the PV panel from overcharging the battery, and an inverter that converts the battery voltage into regular 120-volt alternating-current (AC) house power. All of these parts are easy to find, and connecting them is simple and safe as long as you follow the instructions. (You can also tap into easy, DIY solar-powered lighting — read more at Easy DIY Solar Lighting.)
Many variations of DIY solar power systems are possible, but the table below will give you a starting point. The equipment brands I chose are just examples. The batteries in these systems are oversized to allow for poor sun conditions, and you should only drain the batteries to their minimum capacity if you are confident that power will be restored promptly. Some off-grid folks who are careful about power consumption live year-round on systems no larger than the “Larger system” outlined below.
One good way to find a set of components is to search online for RV or cabin PV systems. Many suppliers sell kits of compatible components in various sizes.
You should keep the system’s batteries fully charged at all times, both to keep the batteries healthy and to have as much stored power as possible at the start of an outage. You can also find packaged systems that come assembled and wired except for the battery, which you can buy locally. This saves you the job of putting the system together yourself, but the price can be quite steep. And be careful — these systems are often advertised by the size of the inverter they use. Knowing the size of the PV panel and battery is much more important, as these determine what you can power and for how long, so be sure to look at the actual size of the PV panel and battery storage that any system supports.
These systems all use 12-volt lead-acid batteries, which store a great deal of energy that a short circuit can release very rapidly. This rapid release can cause injuries, damage to the system’s parts, and fires, so use the same kind of precautions you would use if you were working around a car battery. Batteries give off hydrogen gas while charging and should thus be charged in an area with decent ventilation. Always read the manuals for the parts before putting together the system.
DIY Solar Power System Options
||What Will It Power?
|Minimum system (16 hours to fully recharge; provides 800 watt-hours)
A 7-watt LED light for 114 hours; a 20-watt LCD TV for 40 hours; or both for 30 hours
• Generic 60-watt. 12-volt PV panel
• 5-amp Morningstar SunGuard charge controller
• 12-volt, 80-amp-hour Interstate SRM-24 deep-cycle battery
• 150-watt modified sine wave Tripp Lite PV150 inverter
|Larger system (7 hours to fully recharge; provides 2,200 watt-hours)
A 7-watt LED light for 314 hours; a 20-watt LCD TV for 110 hours; a 50-watt fridge for 44 hours; or all three for 29 hours
• 430-watt DMSolar 145 PV panel (three 12-volt panels, 145 watts each)
• 30-amp Morningstar ProStar charge controller
• Two 6-volt, 225-amp-hour Trojan T-105 golf cart batteries
• 1,000-watt modified sine wave Tripp Lite PV100 inverter
— Gary Reysa