Site-Integrated Electric Vehicle Charging
NREL is exploring multiple solutions for the site-level integration of electric vehicle (EV) charging at workplaces and multiunit dwellings and for commercial fleets.
Workplace charging can be a boon to those employees with EVs, but it can also impact peak loads and increase employers’ electricity costs.
Charging Technology Validation and Demonstration
The NREL campus serves as a living laboratory for electric vehicle smart charging. NREL is home to more than 100 Level 2 EV charging stations by PowerFlex, a cleantech startup that received technical assistance via the NREL-led Wells Fargo Innovation Incubator. The innovative charging stations feature an adaptive charging network with load-sharing and demand-management capabilities.
Validated by NREL, the network dynamically adapts to changing electrical demands and conditions. It uses an algorithm that adjusts the speed of the charge for individual EVs based on several factors, such as the number of vehicles plugged in at a given time, other energy demands on the system, and available power from different energy sources. This allows the laboratory to avoid peak-demand charges. It also reduces the amount of electrical infrastructure required, which helps mitigate installation, operation, and maintenance costs.
Managed Charging in Accordance with Building Loads
NREL is investigating the cost-savings potential of managing workplace charging in accordance with real-time building loads. Tapping into real-world data from NREL’s charging station installations, researchers developed and validated two innovative systems for peak-load power curtailment:
- A workplace demand-charge-management system to control EV charging stations based on aggregated building loads
- A control system to improve charge-management performance using driver-provided information about their energy needs and battery state-of-charge in conjunction with a control algorithm to rectify, if necessary, inaccurate driver inputs.
For more information, see the IEEE conference paper, Workplace Charge Management with Aggregated Building Loads.
Managed Charging Integrated with Multiple Commercial Buildings
NREL partnered with Argonne National Laboratory, Idaho National Laboratory, and Pacific Northwest National Laboratory to develop an aggregator-assisted, charge-control strategy to optimize EV charging at multiple commercial buildings. The innovative charging strategy features coordination with local-building-level controls and a global aggregator to reduce peak power loads on the distribution feeder.
Researchers investigated three charging scenarios—uncontrolled, local-building controlled, and aggregator-assisted controlled. Results indicate that precise forecasting of each building load plays a significant role in control-strategy performance. It points to the need for considering trade-offs when employing aggregator-assisted control technologies in scenarios with limited building-load forecasting capabilities.
Behind-the-Meter Energy Storage
NREL is exploring behind-the-meter storage technologies to help manage the demand-side aspects of EV grid integration. Such technologies could support the integration of EV fast chargers, photovoltaic generation, stationary energy storage, building systems, and the electric grid. Evaluation of how these technologies would integrate across the transportation and building system will be explored in NREL's Optimization and Control Laboratory.