Evaluating Energy Storage for Summer Grid Resiliency

By Philippe Bouchard, Senior Vice President of Business Development and Marketing, Eos Energy Storage

The electrical grid needs to be designed to meet demand surges during the hottest hour of the hottest day of the year. With every summer setting new records for extreme heat, demand surges are becoming increasingly formidable – and sometimes impossible – to keep up with. This summer, utilities in places including Arizona and Northern California reported all-time high demand, with grid failures abounding across Oregon, San Francisco and many other heat wave-stricken regions. We can expect soaring summertime demand and struggling grids to become a regular occurrence.

Traditionally, utilities have relied on peaker plants – often fossil fuel-powered – to keep up with ballooning summertime demand. These plants, which only operate a few times a year, augment transmission and distribution capacity, requiring utilities to anticipate load growth decades into the future. These efforts represent huge investments that do not improve the overall efficiency and sustainability of the grid.

However, we are beginning to see less of a need to rely on inefficient, gas-powered peaker plants as we find a more economic, more versatile, and cleaner means of combatting summer grid strain in utility-scale energy storage. Now running down a rapidly descending cost curve, utility-scale batteries are being deployed by utilities and developers to balance heightening power demands and meet locational capacity needs. These strategic, long-term storage deployments are leading power companies all along the supply chain to rethink the existing strategy of building oversized generation and T&D capacity to meet future demand. For example, pairing storage with utility-scale photovoltaics, which are now cost-competitive with fossil fuel generation, transforms a once-intermittent resource into a meaningful alternative to gas-fired peaker plants.

The Ideal Battery for the Job
The growing role of storage holds great potential for drastically improving the way the grid accommodates the hottest hour of the hottest day. However, not all batteries are created equal, and certain attributes make for better performance and effectiveness under the strain of peak summer demand. Changing climates and record-setting heat present their own challenges for storage technology. These are top factors to keep in mind:

Operating Range
This one is pretty straightforward but worth including up front: summer will test and in many cases breach the upper limit on some battery systems’ operating range. If this is the case, consider the costs for heat-resistant enclosures, HVAC systems, more stringent fire suppression, more complex battery management controls and other measures that keep systems cool enough to prevent thermal runaway. The expenses can add up quickly, so looking into systems that have a broader range and run in the heat with limited need for the assistance of additional equipment pays dividends in the long term.

Increased fire hazard is a reality of summer for the foreseeable future, especially with the amount of aging and degraded energy infrastructure still online. This was the suspected reason behind widespread outages in Los Angeles earlier this month. In these situations, the chemical makeup of on-site batteries becomes a factor. Highly toxic and flammable battery materials can quite literally fan the flames when equipment malfunctions, and can amplify disasters. Take the example of a battery room that caught on fire at a Hawaiian wind farm: firefighters on the scene were sidelined from putting it out for seven hours due to concerns over being exposed to the highly toxic batteries.

Duration of Discharge
Determining the optimal duration of discharge for battery systems becomes more important during extreme heat. Does it make more sense to string together a series of shorter-duration batteries or deploy fewer systems that are optimized for four to six hours of discharge? The decision comes down to a thorough understanding of demand curves for the hottest days of the year.

In this regard, it’s also important to consider the main use case a battery is built for. Is it more geared towards short discharge and frequency regulation, or is it meant to function as a resiliency asset that can supplement and even replace baseload generation for hours on end? Not every battery’s intended use case aligns with utility needs.

Levelized Cost of Storage
This is the factor that takes all other parts of the framework into consideration by providing a figure for cost of ownership over the lifetime of the system. A higher upfront capital expenditure could pay off in the long run through lower operations & maintenance costs or by eliminating the need for secondary safety and cooling equipment. The opposite could be true of a solution with a lower initial cost. Batteries for summer resiliency must continue to operate effectively year after year under punishing conditions, making a comprehensive calculation of its cost of ownership over time an essential part of the decision-making process.

These characteristics provide a basic framework for assessing energy storage solutions that strengthen the grid for summer. By finding the right balance according to use case and project requirements, storage can live up to its potential for making the grid a more resilient, efficient and sustainable network even in the face of extreme demand and conditions.


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