Long Duration Stationary Energy Storage
December 7-8, 2017 
Chicago, IL 

ARPA-E held a workshop entitled "Beyond the Hour and the Day: Long Duration Stationary Energy Storage" on December 7-8, 2017 in the Chicago, IL area.

Stationary energy storage currently plays an important role in the modern electrical grid, and it has the potential to play a much greater role.  Stationary storage enhances grid reliability and resiliency and helps manage variability in both power demand and power supply. Pumped hydro storage is the principal deployed stationary storage technology for centralized grid applications, and provides numerous services at low cost, high round-trip efficiency (75-85%), and across time scales ranging from sub-second to multi-day. Currently, pumped hydro accounts for 95% of domestic stationary energy storage capacity, but due in part to limitations in geologic siting and permitting, it is unlikely to significantly expand beyond current levels.  Meeting unfilled demand for assets like pumped hydro with new storage technologies would strengthen grid resiliency, reduce thermal cycling of conventional fossil generation, improve grid operational efficiency, and enhance the dispatchability of intermittent sources of generation.   Indeed, the rapidly falling cost of utility-scale wind and solar generation opens the possibility for these technologies, if paired with energy storage solutions with extremely low cost across a wide range of time scales, to approach operational and cost parity with conventional, dispatchable generation technologies.

This workshop convened experts in electrochemical, thermal, mechanical, and chemical energy storage and conversion to identify innovative approaches to dramatically reduce the capital costs of long duration stationary electrical energy storage systems. For the purpose of this workshop, “long duration” refers to approximately 8 to 50+ hours at rated power.  Emphasis will be placed on the marginal cost of additional energy storage in systems where energy and power are decoupled. Discussions will focus on systems that charge solely using electricity and discharge electrical and/or thermal energy. Systems delivering thermal energy are envisioned to provide distributed energy storage for commercial and industrial applications. Participants will aid in the identification of technical development opportunities and performance targets that can transform the way long duration electrical energy storage systems are designed and operated. Relevant technical areas include flow battery design and operation, electrolyte formulation, electrochemical active material chemistry, solution chemistry, organic and inorganic chemistry, separation processes, thermal system design, thermal fluids, high temperature materials, vapor compression cycles, heat transfer, cryogenics, phase change materials, thermochemical processes, turbomachinery, systems integration, and hybrid storage concepts.

Envisioned technologies should be capable of discharging for greater than 8 hours at rated power for a fixed $0.03/kWh-cycle across all hours of storage. Thus, the capital cost target for a given partition in the energy storage system is a function of that particular unit’s annual energy throughput; a higher capital cost can be justified for a highly cycled unit relative to a unit with lower annual throughput. For the purpose of this workshop, systems must be siteable and operate with a nominal round trip efficiency >50%, preferably higher. Areas of interest and targeted outcomes include:

·  New approaches to modify the scaling of bulk energy storage system cost and performance for extending economic discharge durations into the tens of hours;
·  Significant reduction in balance-of-plant costs through innovative system architectures, energy dense storage media, and inherently safe bulk storage systems;
·  Synergies between various storage media and conversion processes to reduce overall system costs;
·  Tradeoffs between cost and performance in various energy storage media and systems;
·  Other innovative approaches to long duration electrical energy storage that can meet the cost and performance targets;
·  Primary cost drivers and innovative cost reduction pathways in current bulk energy storage systems;
·  Value propositions for long duration storage technologies and electricity market structures that could incentivize their deployment

Thursday, December 7th

12:00 p.m. 
Eric Rohlfing, ARPA-E Acting Director
Paul Albertus, ARPA-E Program Director

12:25 p.m.
Marco Ferrara, Baseload Renewables
Ryan Jones, Evolved Energy
Aidan Tuohy, EPRI
Raj Apte, X
Panel discussion with presenters

2:00 p.m. Paul Albertus, ARPA-E Program Director
Jarrod Milshtein, Giner
Justin Raade, former CEO of Halotechnics
Ravi Annapragada, UTRC
Panel discussion with presenters

3:45 p.m.
Breakout Session 1: Establish performance and identify technology development opportunities for current state of the art electricity storage systems with 8 to 20 hours of duration
Breakout Group 1: Signature Ballroom 
Breakout Group 2: Medallion Room 
Breakout Group 3: Duet Room
Breakout Group 4: Leander Room

6:00 p.m.Readout and panel discussion from Breakout Session 1

Friday, December 8th

8:00 a.m.
Imre Gyuk, DOE Office of Electricity
Jay Whitacre, Carnegie Mellon University
Yet-Ming Chiang, MIT
Rob Braun, Colorado School of Mines
Josh Posamentier, Congruent Ventures

9:45 a.m.
Breakout Session 2: Identify innovative approaches to scale electricity storage systems beyond 20 h at rated power. Discuss lower limits on cost for various technology classes and how aggressive cost targets can be realized. Provide feedback on proposed program problem statement, scope, and target metrics.
Breakout Group 1: Signature Ballroom
Breakout Group 2: Medallion Room 
Breakout Group 3: Duet Room
Breakout Group 4: Leander Room 

11:45 a.m.Readout and panel discussion from Breakout Session 2

12:30 p.m.1-on-1 meetings with ARPA-E Program Director and staff