The US Department of Energy (DOE) announced up to $30 million in funding for projects as part of a new Advanced Research Projects Agency-Energy (ARPA-E) program: Duration Addition to electricitY Storage (DAYS). (DE-FOA-0001906) DAYS project teams will build innovative technologies to enable long-duration energy storage (LDES) on the power grid.

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%.

Project teams will seek to develop storage systems that are deployable in almost any location and charge and discharge electricity at a target fixed cost per cycle. Projects will fall into two categories:

1. DAYS systems that provide daily cycling in addition to longer duration, less frequent cycling; and

2. DAYS systems that do not provide daily cycling, but can take over when daily cycling resources are either filled or depleted.

DAYS projects will explore a new design space in electricity storage that allows for strategic compromise of performance to achieve extremely low costs. The program also seeks to establish new paradigms for increasing stored energy and extending duration of stationary electricity storage systems.

The funding opportunity is open to a range of storage technology choices, including thermal, mechanical, electrochemical, chemical, and others. The DAYS program requires that all proposed storage systems be charged by electricity alone and produce electricity as the sole output.