ARPA-E Archived Funding Opportunities

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  DE-FOA-0001906 DURATION ADDITION TO ELECTRICITY STORAGE (DAYS) Funding Opportunity Announcement (FOA) 6/15/2018 05:00 PM ET 7/2/2018 05:00 PM ET


The Duration Addition to electricitY Storage (DAYS) program will pursue new long-duration electricity storage (LDES) technologies with discharge durations that range from 10 to approximately 100 hours at rated power. Such “long” durations are beyond the requirements for intra-day (“daily”) energy time shift and many other stationary electricity storage applications common on the grid today. ARPA-E believes durations at rated power of 10 to 100 hours are relevant for needs that go beyond daily cycling but are short of seasonal energy time-shift applications. Long-duration storage applications present new forms of technical challenges associated with exceptionally low lifetime cost requirements (including both capital and operating expenses), particularly for the energy storage media and related components. However, the lower number of cumulative cycles, acceptability of slow ramp rates, and other relaxed performance requirements that are associated with long durations and infrequent cycling provide opportunities for design tradeoffs that may be leveraged to reduce costs and realize economically-viable LDES systems.

The primary objective of the DAYS program is the development of LDES systems that deliver electricity at a levelized cost of storage (LCOS) of 5 cents/kWh-cycle across the full range of storage durations (i.e. 10 to approximately 100 hours). This requirement results in a target lifetime cost that decreases with increasing storage duration, a marked divergence from many existing storage cost targets that focus on a single duration and thus a single cost metric. The LCOS target of 5 cents/kWh-cycle likely requires system round-trip efficiencies greater than 50%.

For this focused program, ARPA-E expects chemical, electrochemical, thermal, and mechanical technical approaches to potentially address this problem statement. The DAYS program requires that all proposed storage systems be charged by electricity alone and produce electricity as the sole output.

If successful, the DAYS program will provide new forms of stationary electricity storage systems that enhance grid resiliency, provide low-cost capacity, support the transmission and distribution infrastructure, enable a greater share of low-cost, intermittent sources of wind and solar in the future generation mix, along with other benefits.

FAQs are regularly updated. To access the most recent responses to questions, visit the FAQs webpage


  • DAYS - FOA Document - Modification 02 (Last Updated: 5/21/2018 11:23 AM ET)
  • DAYS Technical Overview Document (Last Updated: 5/21/2018 11:24 AM ET)

Previous Versions

  • DAYS FOA Document (Last Updated: 5/1/2018 10:46 AM ET)
  • DAYS - FOA Document - Modification 01 (Last Updated: 5/2/2018 02:41 PM ET)
  • DAYS Technical Overview Document (Last Updated: 5/1/2018 10:20 AM ET)

Application Forms and Templates

The following forms and templates may be used as part of the application submission. Note that these forms and templates do not necessarily constitute all the documents required for a complete application. Please refer to the 'Application and Submission Information' of the published announcement to learn more about the required application content requirements.

View Application Forms and Templates

Full Application

  • DAYS - Technical Volume Template (Last Updated: 5/1/2018 10:06 AM ET)
  • SF-424 (Last Updated: 5/1/2018 10:07 AM ET)
  • Budget Justification/ SF-424A Workbook (Last Updated: 5/1/2018 10:07 AM ET)
  • Budget Justification/ SF-424A Workbook Guidance (Last Updated: 5/1/2018 10:08 AM ET)
  • Business Assurances & Disclosures Form - Template (Last Updated: 5/1/2018 10:08 AM ET)
  • Business Assurances & Disclosures Form - Sample (Last Updated: 5/1/2018 10:08 AM ET)
  • Summary Slide Template (Last Updated: 5/1/2018 10:09 AM ET)
  • Summary For Public Release Template (Last Updated: 5/1/2018 10:09 AM ET)
  • Replies to Reviewer Comments Template (Last Updated: 5/1/2018 10:12 AM ET)

Contact Information

    Please contact the email address above for questions regarding ARPA-E’s online application portal, ARPA-E eXCHANGE.
    Please contact the email address above for questions regarding Funding Opportunity Announcements. ARPA-E will post responses on a weekly basis to any questions that are received. ARPA-E may re-phrase questions or consolidate similar questions for administrative purposes.

Submission Deadlines

  • Notice of Intent Deadline: 6/15/2018 5:00 PM ET
  • Full Application Submission Deadline: 7/2/2018 5:00 PM ET
  • View Full Application Reviewer Comments Period: 8/10/2018 5:00 PM ET – 8/16/2018 5:00 PM ET