by Devika Garg, researcher and writer at Sustainable Silicon Valley, 14 July 2015
Green, quiet and now a workhorse for the power grid – the electric car just keeps getting better. Range anxiety and charging hassles apart, owning an electric vehicle (EV) may finally pay off in the near future. Energy experts from Tesla, EVGrid, Google and the SLAC National Laboratory discussed how this could happen at the Silicon Valley Energy Summit (SVES) held at Stanford University.
Less than five years ago when EVs started gaining popularity, skeptics raised concerns that EVs will overwhelm the utility grid and cause blackouts. In the future, the grid could be thrust into chaos when charging tens of millions of EVs. The vehicle to grid (V2G) technology paints a different future: one where EVs could directly and indirectly help support the grid, improve stability and even earn EV owners money.
It turns out that EV batteries, when they are not being used to power a car, are good instruments to back up the grid during peak demand. A company called EVGrid has already implemented two “Battery Second Life” (B2L) systems in California in Mountain View and at UCSD in San Diego. Batteries are very effective as a power regulating solution, and “this is a revenue-generating service that the grid pays for,” said Tom Gage EVGrid’s CEO in a recent interview. Gage was a member in the panel discussion at SVES. “EVs are not just replacements for traditional vehicles”, said Gage. “They represent a way forward in the way we store energy.”
Tesla, which rolled out its $3,500 home battery (known as “the only Tesla anyone can afford”), works to capture the same market. Along with their 10 kWh residential battery, Tesla produces a 400 kWh modular utility/commercial size battery. This means that a 100 utility size batteries connected in parallel can store 40 MWh of energy, as Archan Padmanabhan, Tesla’s Stationary Energy Storage Director, revealed at The Battery Show Conference last year. The energy storage can be used by businesses to offset the grid during the most expensive daytime hours, with batteries charging during cheap night hours.
Essentially, an EV is a battery on wheels. Most cars spend about 95% of the time in the parking lot; EVs can re-purpose this time to manage the grid load and even earn money for their owners by providing energy services to the grid. The University of Delaware developed the V2G concept in 1997, and has calculated that one EV may potentially generate about $400 to $5,000 a year for its owner, depending on the energy market and the amount of time the vehicle operates in the V2G mode. Realistically, the earnings will need to be adjusted by factoring EV battery efficiency, which is about 80% today with 10-15% loss on the energy round-trip. EV owners at SVES also expressed concern over the loss in battery life over multiple charging-discharging cycles. “Vehicles and stationary batteries have different sub-chemistries,” said Padmanabhan at SVES. “We are identifying the right sub-chemistry, the ability to handle more cycles will get better over time.”
But more factors will need to be ironed out before personal EVs can be used to power the grid, range and charging stations being the top picks. “Infrastructure for charging stations has continued to increase, but not fast enough to keep up with EV sales,” said Sila Kiliccote, Demand Response Expert at Google and Smart Grid Leader at SLAC.
It is also important to understand if we can actually use these EVs as distributed storage by quantifying the services they can provide, said Kiliccote. To make V2G work well, it is best to have a predictable duty cycle on the battery and a reproducible recharge time. Buses, garbage and delivery trucks fit these yardsticks and are among the first for testing. Stanford is looking into using its Marguerite fleet for V2G adaptation. The Pacific Gas and Electric Co has undertaken the Intermittent Renewable Management project as a pilot testing ground for distributed storage. But probably the largest V2G trial right now is the one at the US Air Force base in Los Angeles, with a fleet of 29 plug-in vehicles that could potentially provide 252 kW of power on demand.
EVs need to have two-way charging systems to join the V2G movement. Currently only certain versions of the Nissan Leaf and BMW Mini E have it, more EV models will need to be equipped. “Bi-directional batteries are not that challenging from a tech perspective,” said Padmanabhan. “The economics are good and regulation is beginning to happen, at least in California.”
Undeniably, California is the first state where battery grid systems are being deployed, and where renewable energy and EVs are steadily taking over energy markets. The synergy between distributed energy and EVs is spreading its roots. V2G will make most sense for long range EVs with energy to spare, technology that will come with improved batteries. The road is long, but it is only a matter of time when EV owners and utilities will begin to collaborate for sustainability and exciting business opportunities.
Research by Natalia Timakova and Bruce Naegel.