A study from the University of Delaware counters the usual argument that renewable energy is too expensive and unreliable to fully power the US electric grid.
According to researchers, by 2030, renewable energy can supply electricity 99.9% of the time at costs comparable to today's prices.
The key is the combination of renewable energy sources and energy storage, "which we did by an exhaustive search - and to calculate costs correctly," says Willett Kempton, professor at Univerity of Delaware's College of Earth, Ocean, and Environment.
Using a computer model of the PJM Interconnection, which covers the grid in 13 states from New Jersey to Illinois - 20% of the US grid - researchers analyzed 28 billion combinations of renewable energy sources and storage mechanisms. They were tested for four years of historical hourly weather data and electricity demands.
Rather than trying to match electricity generation with demand, researchers focused on how to best minimize costs. It's cheaper to produce more electricity than what's needed during periods of average demand than to store excess power to be used during periods of high demand.
That's because storing energy adds a lot of cost to the system. For every additional hour of energy stored, bigger batteries or hydrogen tanks are required.
"For example, using hydrogen for storage, we can run an electric system that today would meet a need of 72 GW, 99.9% of the time, using 17 GW of solar, 68 GW of offshore wind, and 115 GW of inland wind," says researcher Cory Budischak at Delaware Technical Community College.
200 large wind turbines or 250,000 rooftop solar systems produce 1 GW of electricity.
Researchers achieved reliability of renewables by using diverse sources over a larger geographic area and employing storage solutions. Fossil fuels were need as a backup for just the last few percent of the time.
In terms of achieving cost parity without government subsidies, researchers included fossil fuel costs projected in 2030 that encompass the cost of fossil fuels and their documented external costs such as human health effects from air pollution. Projected capital costs for wind and solar in 2030 are about half of what they are today.
"Aiming for 90% or more renewable energy in 2030, in order to achieve climate change targets of 80%-90% reduction of the greenhouse gas carbon dioxide from the power sector, leads to economic savings," conclude the authors.
The research enhances that released by the National Renewable Energy Laboratory (NREL) a few months ago that shows renewable energy can supply 80% of US electricity demand by 2050. "The technology needed is available today and is more than adequate combined with a more flexible electric system," they concluded. Another report shows how the world can get 95% of electricity from renewables by 2050.
Here is the study: