A power inverter on a free-standing solar plant. Batteries are just one part of a power storage system. The inverter converts DC electricity coming from solar panels to safer, usable AC current.
As the number of solar panels on business and home rooftops multiply, America's power grid is bearing an electrical load that it was never designed to handle: the bidirectional power transfer.
"There's no grid system in the world designed for that," said Anise Dehamna, principal research analyst at Navigant Research. "Every grid has been designed for unidirectional flow of energy -- from transmission to distribution to the end user."
With bidirectional power transfer, the utility sends power to the customer, but with solar panels, the customer can then send excess power back to the utility.
There are two ways to address the increasing electrical load on the grid: an enormous and costly region-by-region infrastructure upgrade, or batteries that can store power and reduce peak load demand on the grid while improving overall system efficiency, according to Dehamna.
Lithium-ion battery systems, which have become the de facto standard for homes and utilities, like the ones Tesla is planning to announce this week, will enable electricity generated through renewable power, such as wind and solar, to be stored on site.
The power stored in battery systems can be used during peak load hours during the business day in order to reduce draw on the grid. Battery capacity can also be used when power isn't being generated by renewable systems, such as at night and during inclement weather. That also reduces grid demand.
Regions are already suffering from backflow issues
Utilities in regions where solar and wind has grown faster than others are already grappling with the consequences of "backflow," or electricity that's sold back to grid utilities from distributed renewable power generation systems.
The first-ever "Quadrennial Energy Review" report released last week by the White House called for "significant change" to America's aging energy infrastructure, including long overdue upgrades to the U.S. electrical grid to keep up with changing energy needs.
In 2014, renewable energy sources accounted for half of new installed electric-generation capacity, and natural gas units made up most of the remainder. Coal and petroleum consumption was flat. Electricity generation from wind grew 3.3-fold between 2008 and 2014, and electricity generation from solar energy grew more than 20-fold.
In Hawaii, for example, 12% of homes have photovoltaic, or solar, panels -- by far the greatest number for any U.S. state. Residents are dumping so much extra electricity onto the grid that it's struggling to handle the increased capacity. The Hawaiian Electric Company said backflow can destabilize the system.
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