IHS reports the United States continues to be the biggest market for microinverters and power optimizers, due to its booming residential and commercial markets. IHS forecasts U.S. market will increase by 76%, reaching just under 1.8 GW in 2015.
Solar modules in an array are connected in a series, like batteries. The array is producing optimally when all modules are performing the same. But what happens when temperature changes, or fall leaves, winter snow or shade covers part of a module, causing it to underperform? The module not only outputs less energy, it can also heat up and drag down the performance of the other modules by constricting the flow of energy through the array. This can cause the array to lose power. However, this is where power optimizers can help.
Power optimizers are DC/DC converters attached at the module level. Installers can connect optimizers on-site, or manufacturers can connect them to the module in the factory, replacing the traditional junction box. Power optimizers can correct for module “mismatch” by allowing each module to function at its maximum power point (MPP) and then converting the energy to the optimal voltage and current for the array. This enables the entire array to harvest more energy.
“Optimizers increase the maximum power point tracking (MPPT) of inverters,” Mark Kanjorski of Ampt told Solar Power World in a podcast. Optimizers constantly monitor the array voltage and current and work to mitigate mismatch effects so that each module can operate at its maximum power level. This results in optimal energy harvest. “Higher MPPT resolution or granularity helps the system recover more energy that would otherwise be lost from electrical imbalances due to environmental mismatches. This results in greater energy production.”
Traditional inverters monitor the AC output side of the array and in some cases may provide string level data. However, they do not provide enough data to detect problems at the module level and maintain production levels. This can lead to energy losses that are invisible to system owners and difficulties in diagnostics for maintenance personnel. Power optimizers, in combination with a monitoring system, can provide greater transparency into system performance, pinpointing any issues from a remote location. This enables more efficient maintenance and higher system uptime.
“Power optimizers perform monitoring at the module level so you can see the performance of each individual module,” said Peter Mathews, North America General Manager at SolarEdge.
Power optimizers in combination with a fixed string voltage inverter also enable more flexible system design with fewer components.
“Power optimizers only deploy minimal electronics on the rooftop to handle the MPPT and DC to DC conversion, leveraging a centrally located inverter at the end of the string,” said Mathews. “This allows installers to reduce hardware, improve reliability, and slash costs. By eliminating any string-design constraints that would decrease the size of a PV system, power optimizers also allow designers to install more modules on the rooftop. For installers, this means increased revenues. For end-users, the added system output equates to lower electricity bills.”