As automakers roll out plug-in hybrid electric cars over the next few years, linking them to the grid will be a critical step in determining their ultimate efficiency.

Increased energy security and independence, petroleum reduction and greenhouse gas reduction are among the potential benefits if the infrastructure is properly installed to handle the extra load on the grid, experts say.

Plug-in vehicles are expected to roll out regionally, and in small numbers. "As these cars come on board, there will be very little short-term impact on the grid," says Larry Alford, manager of distributed generation at Austin Energy. "According to a California Edison study when [GM was] doing the EV1, 20 percent of the fleet could be plug-in hybrids with no adverse grid impact. At some point beyond that it becomes an issue."

Austin Energy is currently evaluating PHEV's value in sharing power, using smart-grid communication to deploy technology from V2Green, a startup communications company. Vehicle-to-grid (V2G) services provide two-way communication between PHEVs and the power grid, helping utilities manage electricity flow to and from vehicles. The real-time data sharing can minimize grid stress and use the vehicle's battery storage to buffer power generated by intermittent renewable energy sources, such as wind and solar power.

The existing electrical infrastructure can handle the PHEV load demand, but only if customers recharge the batteries during off-peak times, says Nathan Mitchell, director of engineering and operation services for the American Public Power Association.

Concerns about vehicles tapping into the grid during peak power consumption will increase as more PHEVs appear. This could require the building of additional power plants and even a reconfiguration of the transmission/distribution infrastructure. According to a study completed earlier this year at the Oak Ridge National Laboratory, within 20 years most regions of the country will need to add capacity to provide for charging PHEVs.

Charging Stations
Public charging stations are also needed because half of the U.S. population lives in multi-family dwellings or park on the street and do not have a home garage, says Bill Boyce, electric transportation supervisor for the Sacramento Municipal Utility District (SMUD). That will require infrastructure upgrades, says Boyce, adding that new construction may have to assimilate different wiring options to accommodate plug-ins.

According to the U.S. Department of Energy data, only two states -- California and Massachusetts -- have more than 10 public electric charging stations, and most have none (see map above).

Public charging stations would cost approximately $50,000 each, with one station required for every 1,500 vehicles, according to research from the Rocky Mountain Institute. Meters with bi-directional communications would cost approximately $400, while a charging timer would cost around $50.

Coulomb Technologies recently unveiled a smart PHEV charging infrastructure for public stations that incorporates payment systems and communications technology to interact with the utility grid. Earlier this month the company announced a partnership with Gilbarco Veeder-Root, a fuel equipment and payment systems vendor, to co-develop charging infrastructure products.

CEO Richard Lowenthal says there are only 54 million garages in the United States to accommodate the roughly 247 million passenger vehicles out there, necessitating charging options for municipalities and parking lot owners.

Coulomb's Smartlet Charging Stations allow subscribers to locate a public charging station, using GPS or through GM's OnStar service. A smart card or key fob is used to unlock the door and begin charging. When charging is complete, the subscriber swipes the card or fob to unlock the door, with the billing data transmitted wirelessly to the utility.

Although the city of Sacramento built many public charging stations for its test of plug-in hybrids, most people opt for workplace and home charging, according to SMUD's Boyce. To discourage consumers from charging at peak times, time-of-use rates or customer incentives would be needed, he says. California officials discovered that by offering incentives, 80 percent of the vehicles charged during off-peak hours.

Utilities are upgrading their resource management capabilities to adapt to renewable power with smart grid technology. However, Kurt Stogdill, Austin Energy’s program manager for innovation and opportunity development, doesn't think upgrading the grid is required.

"We probably don’t need a smart grid to accommodate a significant penetration of PHEVs," Stogdill says. "We could implement smart charging with a charge management system independent of the grid, with communications such as radio or cellular, provided vehicles are capable.

Utilities also look to tie customer billing for vehicle charging into the smart grid, which could identify a car as it charges at different locales and send the bill to the driver’s home.

In another scenario, utilities would sell metered power to "box stores" such as Wal-Mart, with consumers paying for power by inserting coins or swiping a card. However, that would require fast-charging technology since recharging empty car batteries through a standard 110-volt would take several hours, probably a strain for people used to gassing up in five minutes.

The ability to adapt regional power systems for PHEVs may depend on the type of utility located in a specific place. Deregulated private utilities may face more of a challenge than municipal utilities, since they do not control their supply chain.

"Austin Energy is a municipal utility that is vertically integrated, so we can handle these issues much easier than most utilities in Texas that are deregulated," Alford says. "Because the different sections of their supply chain (such as wire and transmission line owners) cannot even talk to each other, it’s much harder for them to do that."

Alford expects to meet with Department of Energy officials Oct. 8 to determine what alliances can be created among power companies, governments and business communities to accommodate PHEVs.

There will also need to be discussions about regulations, standard laws and rules, according to Alford. Those efforts will focus on a standard protocol to guarantee seamless communications between utilities and vehicles, regardless of the latter's manufacturer.

"A lot of rules are being written on the front end with an idea about what things will look like on the back end," Alford says. "When there’s mass deployment, standards and practices need to be in place at that time."

(The Rocky Mountain Institute is holding a charrette workshop in Portland, Oregon on October 8-10 to discuss how to integrate plug-in hybrids into that smart grid. Matter Network is covering the event .)

The arrival of PHEVs should offer utilities increased revenue opportunities from power sales and can improve a system’s load profile to make it more efficient and balanced, says Mike Rowand, director of advanced technologies for Duke Energy.

However, clean air and not profit is SMUD's motivation for developing charging stations, says Boyce. The reduction in burning fossil fuels by switching to PHEVs is expected to be "huge," he says.

By recharging instead of pumping, consumers benefit by purchasing the equivalent of a gallon of gas for less than $1, Boyce says. "Money spent on electricity will stay in the community instead of going for imported oil. It helps the overall community get much better economically and leads to sustainability."

So, despite all the challenges of integrating PHEVs, Rowand says, "The potential benefits make it worthwhile."

(Photo via flickr)

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