MIT sets targets for energy storage to aid renewables

Source: Umair Irfan, E&E reporter • Posted: Thursday, June 23, 2016

Storing electricity adds value to intermittent renewable energy, and a new study could help investors figure out where to place their bets on storage technology development.

Lulls in wind and sunshine present a challenging problem for utilities that need to deliver stable power. Storing electrons for later — whether using batteries, flywheels or pumped hydropower — would help shave peaks and fill valleys in power production.

However, much of the technology on the market isn’t ready for prime time, often too expensive or falling short in some critical performance metric.

“One of the major technology challenges of scaling up renewables is developing economically feasible energy storage,” said Jessika Trancik, assistant professor of energy studies at the Massachusetts Institute of Technology.

In a paper published last week in the journal Nature Climate Change, Trancik looked at the idea of using stored energy to sell additional electricity on the grid when prices are high. This is likely a better business case for energy developers than simply smoothing output from generators, since wind turbines and photovoltaics are often plugged directly into the grid.

“We’re asking the specific question, ‘Can storage add value to solar and wind for the developer?'” Trancik said.

In particular, she examined the roles of power and energy in storage technologies. Power is the rate at which work is done, and energy refers to the total amount of work done. A storage technology like lithium-ion batteries tends to have relatively high energy and low power, while the situation is reversed with flywheels.

Drawing on real-time energy prices, regional markets, and availability of wind and solar power, Trancik and her team calculated what circumstances would have to align in order to make energy storage a viable investment for energy developers. They examined Texas, California and Massachusetts as their case studies.

High-energy systems like pumped hydropower and compressed air caverns that can deliver energy over a long period of time emerged as winners, providing a solid payback to investors. Batteries became suitable in regions where geography can’t accommodate a pumped hydropower station.

These winners held up across different power markets with varying prices. This is because energy-use patterns and electricity price surges remain largely consistent as people go to work on weekdays and come home in the evenings, creating a generally similar demand cycle.

Whether an energy storage system is a worthwhile investment still depends on the region, but the findings establish the energy market’s goal posts, giving investors a better sense of what kind of technology and price targets they should aim for and the trajectory they should take.

“The clean energy transition will not happen unless investors opt in to clean energy technologies,” Trancik said.

Erin Baker, a professor of mechanical and industrial engineering at the University of Massachusetts, Amherst, who was not involved in the study, said the report offers a new perspective on energy storage development. Typically, new storage technologies are driven by scientists from the bottom up, but the paper gives a sense of the market drivers from the top down.

“We haven’t really seen a user-driven push for improving storage in the electricity industry,” Baker said.

However, she noted that the scope of the paper is limited to using storage to sell at peak energy prices. “What makes this all so complicated is that there are lots of different uses for storage,” she said.

Energy storage systems can help shave peak demand, resolve intermittency and provide frequency regulation on the grid. All of these services have different technical requirements, and energy markets value them differently, so depending on the use case, another storage technology could emerge as a winner.