Power Up: How Storage Changes Solar’s Game

On July 1, the results of a study ordered by the California Public Utilities Commission on “Effective Load Carrying Capacity” (or, ELCC) across various solar and wind renewables projects were released. 

ELCC is a measure, in percentage terms, of how much of a given facility’s theoretical generation capacity is available when people actually need it, expressed as a percentage (and clearly, the higher the percentage availability the better).

In other words, if I have a power plant rated to deliver 250 megawatts, the ELCC is the percentage of that 250 megawatts that is actually available to me when I come looking for energy.

Unsurprisingly, fossil fuel plants carry very high ELCC ratings (a modern natural gas combined cycle plant is typically assumed to operate at 100% ELCC) because they can literally be “turned on” at full capacity when the grid needs power.

Solar’s achilles heel has always been low ELCC ratings relative to not only fossil fuels, but even relative to wind, precisely because in many markets electricity demand tends to spike just as the sun sets (as it happens, there’s no way to turn the sun “on”).

The CPUC’s study shows that storage, for solar, is a game changer, and here’s why: 

  • Without storage, the average ELCC value for wind plants was found to be 30%, whereas the average value for tracking photovoltaic solar installations was just 5.8% 

  • Co-locating 4 hours’ worth of storage capacity at wind sites increased the ELCC to 62%

  • And, adding 4 hours of storage to a solar site increased the ELCC jump to 99.4%: nearly a 20x increase in ELCC and on par with fossil generation

The implications are clear: the marriage of solar with storage has the capability to reliably meet energy demand, terrific news that will drive increased adoption of renewable energy solutions. At the same time, and like any marriage, for the partnership between solar and storage to be productive over the long term, there are multiple considerations to take into account. 

As Candela’s head of Origination and most customer-facing advocate, I’ve spent over 20 years developing utility scale projects since the inception of the renewables industry, and my primary focus has been to ensure that  the solutions we bring to our clients represent an optimal combination of proven underlying technology, cost efficiency, and the right solution for a given use case  - which is not always straightforward.

In subsequent posts, my colleague Geoff Baxter will explore the multiple factors at play when it comes to getting storage right. Modern storage solutions can involve a lot more than just batteries: innovative approaches have advanced storage by using molten salt (heated to one thousand degrees), giant flywheels, gravity towers, and even liquid air.

Candela’s management team has led the development of the first large-scale solar PV projects across the country over the last decade. Since our founding in 2018, we have included storage in our portfolio of solutions available to our customers. From providing an evening peaking resource to offset the use of high cost, high carbon gas peakers, to creating a generation profile shaped to meet our customer’s needs, we know large scale solar PV coupled with cost effective storage technologies will provide the value and flexibility demanded by the current energy market and our customers. 

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