Often when electric vehicle charging comes to mind, it is a one way operation in that the charger draws energy from the grid or an attached renewable energy source to power up a car such as the Nissan Leaf. These same chargers though could soon meet local needs for energy in a first of its kind pilot project going on in Colorado.
At the end of August, according to engineering firm Burns & McDonnell, a team installed a system of bidirectional, fast-charging stations for a fleet of plug-in electric vehicles at Fort Carson, Colo. This first of its kind system will push power back to the base microgrid when needed to either meet installation demand or improve overall power quality. It is part of an ongoing microgrid project at Fort Carson known as Smart Power Infrastructure Demonstration for Energy Reliability and Security (SPIDERS).
In terms of technical functionality, the bidirectional charging units, said those behind them,
are capable of providing up to 300 kilowatts (kW) of power to plug-in electric vehicles and also can discharge a like amount of stored energy from the vehicle batteries to the grid or microgrid via Society of Automotive Engineers (SAE) standard J1772-compliant bidirectional charging cables. The vehicle-to-grid (V2G) charging includes power factor correction, which is a growing concern at locations such as Fort Carson that are experiencing a growth in on-site solar power generation, resulting in utility rate penalties.
Each of the five chargers have been tested to charge and discharge at full capacity of 60kW, and have imported and exported a combined 394 kVAR (reactive power that diminishes the real power capacity of transmission lines) to the local grid even when electric vehicles are not connected to the chargers. This provides a 24-hour-per-day benefit to Fort Carson by absorbing VARs from the grid, thus increasing the power factor of the loads at Fort Carson and making the transmission of power from the local utility more efficient and less costly.
The chargers are also integrated into the SPIDERS backup power microgrid, which allows the installation to utilize a fleet of bidirectional-capable electric vehicles as energy storage devices that, in conjunction with diesel generators and a 2-megawatt (MW) solar photovoltaic array, increases the reliability and efficiency of backup power systems to critical facilities at Fort Carson.
Vehicles being used in conjunction with this installation are being provided by both Boulder Electric Vehicle and Smith Electric, the latter of which is also involved in a pilot project in Houston, Texas replacing diesel delivery vehicles with all-electric medium- and heavy-duty models. The electric vehicle companies have separate agreements with the U.S. Army’s Construction Engineering Research Laboratory (CERL) and Tank Automotive Research, Development and Engineering Center (TARDEC), while overall project management is being handled by he U.S. Army Corps of Engineers (USACE), Omaha District, and includes technical guidance from CERL and TARDEC.