Alternating current powers the modern world and is the energy source our home appliances and conveniences are designed to use.
AC is used primarily because of the ease in which its voltage can be controlled; higher for long-distance transmission, lower for use in our domestic equipment.
However, with the advent of the latest development in alternate energy technology, we now have infinite control of direct current.
DC current has the advantage of being storable and in an off-grid or backup system, energy has to be stored during productive periods for use when the sun and wind harvest is minimized.
In an off-grid system, solar photovoltaic panels and wind turbines are used to harvest these natural forces and convert them into usable electricity.
All photovoltaic panels produce DC, whereas wind turbines can produce either AC or DC as size and need determine.
Once the energy is stored as DC, then what? The home appliances as mentioned above are AC.
This is where the inverter comes in. The inverter takes the direct current voltage and converts it to 120-volt alternating current.
AC current at 120 volts is fine for a cabin or small home with a shallow well where you can get away with a 120-volt AC water pump, etc., but what if you need a 240-volt water pump?
In the earlier systems you could provide that in two ways, the first is with the two inverters, one synchronized with the other, powering one leg of AC current each.
The alternative was the use of a generator for the large loads.
The two “parallel” inverters had the disadvantage of extra expenditure, both in initial purchase and installation, and you were limited to either on-grid or off-grid applications as few inverters could do both.
Recently the technology has progressed to the point that inverters are now available that can produce “split phase” voltage, in other words one inverter can provide you with 240-volt AC. These machines are advanced to the stage of being either on-grid, off-grid or can be used as backup systems.
Split phase inverters can accept multiple inputs from solar charge controllers, accept turbine power in alternating current, and have load ratings as high as eight kilowatts.
Previously, “single phase” inverters where limited to 4,000 watts in any one unit configuration.
Split phase inverters can be AC coupled to wind turbines, giving them even more versatility, and with load sharing capability the wind turbine can run your household loads while it charges your batteries.
Like single phase inverters, split phase inverters can also be paralleled to produce up to 24kW, which make them suitable for homes with large shops, farms or lodges with large power demands.
Versatility has been built into these machines, enabling them to meet a variety of situations and demand.
The caveat: as with all new technologies, from tablet computers to blue ray devices, initial availability is an issue, but it’s guaranteed that manufacturers are racing to meet demand.
Lorne Oja is an energy consultant, power engineer and a partner in a company that installs solar panels, wind turbines and energy control products in Central Alberta. He built his first off-grid home in 2003 and is in the planning stage for his second. His column appears every second Friday in the Advocate. Contact him at: lorne@solartechnical.ca