Saturday, November 20, 2010

Energy Storage and PV Tied to EV Charging

John Gartner of Pike Research reports that two charging companies, Eaton and AeroVironment, are working to incorporate energy storage solutions into the charger (see EVs a Portal to Distributed Storage). "Putting storage into the charger rather than using the vehicle for power to the home will preserve the life of the EV’s batteries and can capture cheaper energy even if the vehicle is not plugged in," he says. The storage batteries could be lithium ion (in the future from the vehicles after their useful life), as well as less costly nickel metal hydride or advanced lead acid batteries.

These batteries could also be integration with a photovoltaics/solar power installation. Earlier this year, Eaton announced that is was working on a prototype integrated solar-assisted electric vehicle charging station to be erected at the Electric Power Research Institute (EPRI) research laboratory in Knoxville, Tenn. The project also involved the Tennessee Valley Authority (TVA). Additional stations are planned for Oak Ridge National Laboratory, Nashville, Chattanooga and another site in Knoxville.

“Solar-assisted electric vehicle charging stations are a crucial step toward the development of a regional system of clean fuel for electric vehicles,” said Tom Schafer, vice president and general manager, Eaton’s Commercial Distribution Products Division.

The collaboration comes on the heels of Eaton’s creation of a new business unit that will be responsible for the overall direction and profitable growth of the emerging electric vehicle and transportation infrastructure business within Eaton’s Electrical Sector. Eaton has named Tim Old the new business unit manager of this new Electric Transportation Infrastructure unit.

The prototype charging station used by EPRI and TVA, also known as a Smart Modal Area Recharge Terminal, or SMART™ station, will provide information on energy usage, the time when the equipment is used, the amount of solar-generated electricity produced and stored, and the potential impact of load clusters - when several vehicles are refueled at the same time - on distribution system reliability.

The collaboration will create a model charging facility that will charge electric vehicles quickly and reliably, and it will produce data to assist in implementing key components of a smart electrical grid. These components could include integrating renewables onto the grid, utilizing a battery storage system, assessing the impact on reliability of a distributed resource generation, testing advance metering infrastructure and analyzing electric vehicle supply equipment.

Eaton recently announced a deal with Mitsubishi Motors North America, Inc., (MMNA) and tech services provider, Best Buy. For residential electric vehicle customers, Best Buy's Geek Squad will provide site analysis and work to manage electrical home infrastructural upgrading and installation by licensed electrical contractors of Eaton's advanced Level 2 (220V) charging hardware for Mitsubishi's "i" powered by MiEV electric vehicle, which goes on sale in fall of 2011.

In addition, Eaton will provide both the electrical infrastructural support and Level 2 chargers to MMNA's dealerships. These 220V (15A) charging stations can be installed in a home's garage and help reduce the charging time of Mitsubishi's lithium-ion battery-powered vehicle by 50% versus a standard 110V electrical outlet. Given its battery size, Mitsubishi "i" customers can have the choice of only applying existing Level 1 (110V outlet) equipment, or the faster Level 2 charging which can affect a complete charge in about 7 hours.

Some basics on charging (courtesy of AeroVironment): You’ll often hear a particular charging regimen described by its charge “level” – Level 1, Level 2, or Level 3. These different charging schemes are distinguished by their utility requirement and total time for a full charge – and each fills an important niche.

“Level 1” AC charging uses a standard 120V outlet and takes 11 to 20 hours to charge a depleted EV. Level 1 charging systems are designed to be portable and used in the case of an on-road emergency, when the driver is running low on charge and needs to plug into a readily available outlet.

“Level 2” AC charging docks and stations deliver AC power reliably and safely to the electric vehicle. The power from the Charging Dock is fed to the car’s on-board charger. An on-board charger is small enough to be integrated into the car and, with the Level 2 off-board Charging Dock’s help, can power up the battery in 3 to 8 hours – usually at home when the driver is sleeping. This convenient charging regimen is often called opportunity charging, because it calls for recharging during "opportune" down time such as sleep, work, or play. Some charging docks feature robust communication capability and can “plug in” to the Smart Grid.

“Level 3” DC charging stations use greater amounts of power and current to bypass the vehicle’s on-board charger with a fast and reliable DC charge in minutes instead of hours. According to the AeroVironment website, the company's DC charging solutions have been vetted for more than a decade in heavy-duty industrial applications – including auto plants, airports, and retail distribution. They say level 3 DC charging is suited for public charging infrastructure; charging large vehicles with big batteries such as buses; and commercial or service fleets with very little recharging downtime.

Pike's Gartner notes that for commercial fast DC chargers, incorporating battery storage could be a way around impacting peak demand. "In addition to also storing excess solar power, commercial customers could use the charger/storage system as emergency power and to similarly purchase energy when it is the cheapest and quick charge their fleets on demand without worrying about cost or impact on the grid," he writes. "Charging just one vehicle at this rate is equal to approximately 43 vehicles being charged via Level 1 (aka standard household current) or 9-18 vehicles at Level 2 using charging equipment. Complicating matters is that DC charging is by necessity immediate – delaying a 15-30 charge defeats the entire purpose. Plus, these charge locations are likely to be at truck stops, gas stations, or mini-marts, which aren’t places that most folks plan on spending a lot of time."


  1. "Putting storage into the charger rather than using the vehicle for power to the home will preserve the life of the EV’s batteries and can capture cheaper energy even if the vehicle is not plugged in,"

    I'm not sure I can see any sense in this approach as far as charging the EV. You've got the extra expense of the temporary storage batteries and one more energy loss in charging a second set of batteries.

    Besides, most cars are going to be plugged in at night when power is cheaper.

    As for individual home storage, I don't see that being efficient either. (Saying that as someone who has been off the grid for a couple of decades.)

    Better to have 'neighborhood' storage. That could soak up any extra residential PV during the day and carry some nighttime wind forward to peak hours. And could be professionally monitored/maintained.

    Distributed storage makes a lot of sense when it can reduce the need to upgrade transmission lines, but too much distribution is likely to mean lots of poorly maintained systems and installing extra equipment such as inverters in each house.

    Furthermore, how many people would invest the money in a home storage system?

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