Introduction
In October 2022, Salt River Project launched the SRP EV Smart Charge program. The program’s central goals are to demonstrate distribution-level asset protection, daily load management through electric vehicle telematics, and increase demand response capacity by reducing the peak loads created by EV charging across distribution assets.
Effective managed charging prioritizes drivers’ needs and ensures that vehicles are properly powered when needed, while concurrently allowing a utility to control, delay, or curtail EV charging to meet grid needs. Addressing bulk system needs, such as reducing or avoiding the curtailment of renewable energy generation and shedding load during times of grid stress, is a critical consideration and often a first step in optimizing EV charging.
Managing EV charging with just bulk system benefits in mind, however, can have unintended consequences on local distribution systems. If the majority of residential EV customers are on a time-of-use (TOU) electric rate and everyone schedules their charging as soon as the off-peak period begins, the large spike in energy demand from their vehicles simultaneously initiating charging would create a ‘secondary evening peak’ or ‘snapback’. This problem becomes especially acute when EV clusters appear and secondary peaks are localized, putting unplanned strain on local distribution infrastructure.
However, findings from this program indicate that the typical EV is plugged in at home for around 12.5 hours per day, but only needs around 2.5 hours per day to charge. Utilities can leverage this charging flexibility to shift EV charging load to more optimal time periods. To avoid the snapback phenomenon, utilities can apply a load-balancing technique that considers a group of EVs served by the same distribution infrastructure and ensures vehicles charge at varying times.
The SRP EV Smart Charge Program is a scalable, multi-phased managed charging program that employs telematics-enabled managed charging for active load management and demonstrates distribution-level asset protection ability. This program leverages WeaveGrid's patented solution called Distribution Integrated Smart Charging Orchestration (DISCO) to optimize EV charging. The DISCO platform collects driver preferences (e.g., level of charge needed by a specific time), monitors vehicle telemetry data for all program participants, and then synchronizes charging schedules for all related vehicles under management.
Widespread EV adoption presents an unprecedented infrastructure and cost risk to the distribution system. The SRP EV Smart Charge Program seeks to better understand the effects of and opportunities for EVs at the distribution-level.
Goals
This multi-phased program targets the following goals:
- Collect smart charging EV usage information to inform program cost effectiveness, grid planning, and future program design.
- Daily load management through actively managing home charging to avoid on-peak charging while meeting each driver’s requirements.
- Demonstrate distribution-level asset protection by minimizing peak EV charging loads for groups of vehicles served by the same distribution asset.
- Better understand and analyze grid reliability strategies using EVs as variable grid assets through the capacity for demand response through the program.
Methodology
The SRP EV Smart Charge Program employs a three-phase design. In phase one, 250 eligible SRP electric vehicle drivers were enrolled into the managed charging program. With drivers’ vehicles connected through telematics, WeaveGrid then built a baseline understanding of customers’ charging habits by monitoring charging and providing insights and analytics back to SRP. Having quickly reached full enrollment, the program moved into phase two, in which WeaveGrid leveraged vehicle telematics to actively manage vehicle charging, optimizing charging in line with customer preferences, utility price signals, and customer rates.
In the third phase of the program, SRP and WeaveGrid demonstrate distribution-level asset protection through optimization for peak load reduction in asset operations through leveraging WeaveGrid’s DISCO technology. This phase allows SRP to meet drivers' charging needs while studying how EV charging can be optimized to meet grid constraints and support protection of distribution assets.
Operationally, SRP has created eight groups, varying in rate composition and other key characteristics (e.g., residential solar customers). SRP designed vehicle groupings to include a comprehensive spread of charging behaviors and a limited window for accommodating off-peak hours. They are also designed to mimic real world scenarios experienced by circuits and feeders in service of asset protection design. SRP curated these groups in alignment with the program objectives. By carefully designing each cohort, SRP can maximize the information gathered in these early load-balancing tests.
In all stages and groups, SRP has and will continue to collect and analyze smart charging EV data to inform program cost effectiveness, grid planning, and future program design.
Program Status and Results
WeaveGrid and SRP exceeded the program’s EV enrollment target in four days. Phase 1, which built a baseline understanding of customers’ charging habits by promptly monitoring charging and providing insights and analytics, commenced in October 2022 and concluded in January 2023. Phase 2, which ran from January 2023 to early May 2023, involved active managed EV charging to meet driver needs and optimize charging to a driver’s TOU off-peak windows and a utility signal. As of May 2023, the EV Smart Charge Program has entered Phase 3, in which SRP demonstrates distribution-level asset protection through co-optimizing EV charging for customer preferences, customer rates, and peak load reduction in asset operations. This program design allows SRP to perform load management through telematics, achieve asset protection goals, and increase demand response capacity by reducing peak loads created by EV charging.
Early results from Phase 3 indicate EV charging can be managed inline with distribution constraints without compromising customer experience. In June 2023, vehicles enrolled in an EV Smart Charge group with DISCO enabled consumed 60,609 kWh of energy at their homes, accounting for 85% of all their charging. Using WeaveGrid’s DISCO managed charging solution, 97% of all home charging occurred outside of on-peak periods amongst the customers on a time-of-use rate. The remaining 3% of home charging occurred during on-peak periods not as a result of load balancing, but due to other factors, primarily driver preferences. For the 97%, SRP was able to balance charging across the off-peak period, flattening load and preventing a snapback at the beginning of the off-peak period.
By balancing charging this way, SRP found that groups with DISCO reduced aggregate peak load by 27%, or 93 kW, on average during the first month of operation. These groups saw an average aggregate peak load that typically ranged from 209 kW to 269 kW.
To explore the capabilities of DISCO, vehicle groups of varying sizes were created, ranging from five to 100 vehicles. Additionally, some vehicle groups also had varying rate schedule makeups; some were weighted towards customers on flat rates and others towards time-of-use rate customers. DISCO performed well across all groups, achieving a reduction in the average daily peak load for all groups. This behavior signals DISCO’s increasing efficacy and importance in a world with rapidly increasing EV adoption.
The SRP EV Smart Charge Program utilizes WeaveGrid’s DISCO algorithm to demonstrate that distribution-integrated smart charging can be leveraged as an effective load shaping tool without negatively impacting customer experience. These reductions in peak load will allow SRP to prevent asset overload and the need for additional infrastructure investments by prolonging service life of existing distribution assets.
Program Next Steps
The SRP EV Smart Charge Program will continue in its current form through the end of 2023. The program will continue to gather data and learn from continued program engagement with participants, including gathering data on customer satisfaction, load shifting, peak load reduction and the impacts of customer behavior and preferences on performance. Additionally, SRP will be focused on reporting results from six months of the pilot, and seeking approval to expand the program to reach more customers and measure its impact at scale.
Conclusion
As residential EV adoption grows rapidly, managing distribution costs is critical for utilities to maintain affordable reliable power. The SRP EV Smart Charge Program aims to determine how to best optimize EV charging for distribution constraints, by leveraging intelligent optimization to create more value streams for EVs like unplanned cost avoidance. Throughout this program, SRP hopes to gain a better understanding of the impact of EV charging on the grid and determine strategies to avoid or lessen costly infrastructure upgrades through the load created by EV charging, while reducing both pricing and snapback.
SRP is committed to creating a streamlined and optimized charging experience for enrolled participants, while concurrently supporting grid reliability and mitigating grid strain. SRP is committed to enabling 500,000 electric vehicles (EVs) in territory by 2035 and aims to have 90% of these vehicles utilizing managed charging. Furthermore, SRP aims to meet customers’ diverse charging needs while demonstrating distribution-level asset protection – As the early results indicate, SRP is already seeing success here. In partnership with WeaveGrid, SRP is well on the way to better understanding the effects of and opportunities for EVs at the distribution-level and preparing for widespread EV adoption in Central Arizona.