AC solar panels are increasingly capturing attention – so what are they, how do they differ from standard modules and what are their reported advantages?
Traditional solar panels output Direct Current (DC). DC electricity can not be used directly by common household appliances or fed into the mains grid; so it first needs to be converted to Alternating Current (AC). This is somewhat of a waste as many appliances and gadgets then convert the AC current back into DC internally.
One of the reasons AC is the current of choice around the world is AC is more suitable for transmission over what can be quite long distances from a power generating station to the end consumer, although High Voltage DC (HVDC), different to “normal” DC has proven itself even more superior over even longer distances.
The conversion of the DC current produced by solar panels to AC for residential applications is performed by a solar inverter – which up until recently has typically been a large, expensive and separate component located a short distance from the solar panel array. A number of solar panels may be routed through a single inverter.
AC solar panels still output DC; However, instead of the solar inverter being a large box separate to the panel, on the back of AC solar modules is a micro-inverter that converges the DC to AC.
The reported benefits include simpler and safer installation, improved electricity harvest and the elimination or reduction of other componentry.
In a standard solar array scenario where multiple panels are connected to a single inverter, one shaded panel can affect on the overall performance of that array – the embedded microinverter arrangement also addresses this issue.
While micro inverters have been available for some time as an add-on fixed to the racking benefit the solar module, one of the first companies to roll out “true” AC Solar Panels for the general market was AU Optronics (AUO) in 2011.
The AUO Unison module incorporates micro-inverter technology from SolarBridge and according to the company increments system performance by up to 25% through reducing the overall impacts of system shading, soiling and degradation losses.
Another popular micro-inverter being incorporated directly into solar modules are the units created by Enphase. Enphase announced it had shipped over 1 million microinverter units by late 2011.
While AC solar panels are not readily available in countries such Australia as yet, as micro inverter technology evolves and proves itself to be viable in various climates, we can expect to see many more AC solar modules appearing in solar farms and on rooftops around the world.