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The ability to recharge batteries from renewable energy sources is only part of the reason that off-grid living is now a practical reality. Batteries alone will not provide the comforts and conveniences of modern living. To take full advantage of an independent electrical system, a DC to AC inverter is essential.
Demystifying Inverters
Most inverters are used in conjunction with a battery bank or some sort. Batteries are the heart of an inverter-powered electrical system, sorting power for use on demand. The most basic way to draw electrical power from a battery is direct current (DC) at the normal voltage of the battery. Your car radio, for example uses 12 volts DC (12Vdc), the same as your car battery. Many off-grid electrical systems (those not powered by electricity from a utility company) use 12-volt DC power to run simple loads such as lights. (Any consumption of electrical power is called a "load.") Such systems are commonly referred to as low-voltage DC systems. Powered by a 12-volt DC system, you can enjoy the benefits of electric lights, entertainment systems, laptop computers, and other devices that can be operated off a car battery. However, you can't run power tools, kitchen appliances, or office machines, without the help of some device that generates "household" electricity. In North America, 120 volts alternating current (120 Vac) is the standard. In many other countries, 230 volt 50Hz is the norm.
To run your standard appliances, one alternative is an engine-powered generator. Fire it up and as long as it is running (noisily), you can use your appliances and tools. But as soon as you turn it off -- or it runs our of fuel -- the electricity stops.
Another alternative is to produce 120/230 Vac from the batteries using an inverter. An inverter is a device that converts battery power (DC) into alternating current (AC) of a higher voltage. DC-to-AC inverters have been around a long time. Energy loss in this conversion process at first was very high: the average efficiency of early inverters hovered around 60%. In other words, you would have to draw 100 watts of battery power to run a 60-watt bulb. A new way to build inverters was introduced in the early 1980's. These fully solid state inverters booted efficiency up to 90%.
One note of caution: when connected to an electrical grid, it's easy to be casual about electric consumption. As long as you can afford it, the thinking goes, the utility company probably won't run out of power. With a battery, however, the quantity of electrical power is finite. You need to calculate and monitor your electrical consumption if you don't want to run the batteries down. You can use our online system sizing worksheet to calculate how much power you may possibly need.
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