Solar power might be a shining example of a great renewable-energy source. But combined with existing infrastructure, it’s wreaking havoc on California’s electric power grid. So much so the problem already has a popular name: The California Duck Curve.
Here’s why. When legislators in the Golden State passed a climate-change law mandating that California gets a third of its electricity from renewable energy by 2020, they were hoping to encourage residents to install solar photovoltaic cells.
It worked. Solar panels now blanket the roofs of homes and commercial buildings. Passengers flying to Los Angeles can see giant solar farms glittering in the Mojave Desert below.
But there is a hitch. California’s famous sunshine helps produce lots of solar electricity during the day—when demand is typically low. Usually, demand for power peaks in the morning, when people are getting ready for work and school. Then they leave home for the office, causing power usage to drop off in the middle of the day. Later, when they return home, there’s a peak between 7 and 9 p.m. as they cook dinner and watch TV or use computers.
This use pattern typically creates a gentle wave-like dip, but because of the growing popularity of solar power, that demand trough during the day is getting deeper. When plotted on a graph, this creates the sagging belly of the duck. Then, when the sun goes down, the demand for power from conventional power plants quickly ramps up.
Mike Unum, a senior product manager with GE Grid Solutions, which provides advanced products and services that enable more resilient, efficient and reliable power systems, says that as people install more solar panels, the problem is only going to get worse. This is a problem since most conventional power plants aren’t like light switches that can be easily turned on and off or even dimmed.
Nuclear power plants produce electricity 24/7 with limited capability to ramp up or down. Fossil-fueled plants can modulate their output, but turning them on and off can be a multiday process depending on the specific power plant technology involved. (Gas-fired power plants are the most flexible.) All this means that going from the trough to the top of the duck’s head on a daily basis is a complex task.
But there are things that can be done to help kill the duck. Initiatives such as the shift toward energy-efficient LED lighting can help reduce the peak. Demand-response programs and rate reforms also can help shift the load to different times of day. They can encourage people to avoid using energy-gobbling electronics and air conditioning during peak hours as California does when it issues a “flex alert.”
But some of the best solutions to the California Duck Curve problem may come from breakthroughs in energy-storage technology. The ability to efficiently store power during low-demand hours and withdraw it during high-demand hours would allow the curve to be flattened even further.
Software also will play a big part. It could monitor and coordinate the control of a large number of distributed energy resources ranging from solar, wind, gas to hydropower. Since many of these sources are owned by third parties, we will need advances in communication, visualization and optimization software to get them working together.
But things are changing. Distributed energy resource management software, such as the kind GE is piloting domestically and in Europe, will provide operators with the requisite tools to mesh consumption information from smart meters with load forecasts and status updates from the grid.
Platforms such as Predix—GE’s operating system for the Industrial Interenet— will also play a big role. All of the solar panels, thermostats, power plants and grid technologies will have to be able to share information, and engineers will have to quickly analyze that data to know how much energy should be going where at any given moment. “Ultimately these types of technologies are going to allow us to coordinate all of these devices,” says Unum. “Think about tens of million of devices. Think about if everyone had solar power and a battery—how would we manage that?”
As more third parties move into the power space, expect to see more creative solutions for problems like the ones California’s energy generators are currently facing. “The rules haven’t been defined yet,” says Unum, “and that’s really the interesting part.”