Renewable + Storage Grid

Storage as far as the eye can see.

In Solar and Storage Marketing we estimated the cost of transitioning a Maryland residence with an existing 18.5 kW solar PV system connected to the utility grid to operate reliably off-grid during recent winter storm Fern, which reduced solar system generation to near zero for a period of 10 days. The system would have required approximately 1,100 kWh of electricity storage capacity to continue normal operation over the 10-day period and increased solar generation capacity to recharge this storage capacity rapidly before the next weather event.

The requirements of this residence are a microcosm of the requirements of a fully renewable plus storage grid for a state like Maryland during a massive winter storm such as Fern. Maryland’s annual electricity consumption is approximately 60 TWh. Estimates of the storage required to support a reliable renewable plus storage grid in the US Northeast are approximately 25% of annual generation, or approximately 15 TWh. Storing this quantity of electricity with current technology batteries would require approximately 4,000,000 Tesla Megapacks or equivalent at a cost of approximately $1.4 million per Megapack.

Renewable activists are quick to suggest that this amount of storage would not be required and that Maryland could rely on imports of electricity from adjacent states. However, this assumption rests on three critical factors: the geographic extent of the major winter storm in question; the availability of sufficient excess generating capacity in adjacent, unaffected states; and, adequate capacity of the transmission interconnections. This appears to be a dangerous assumption since adjacent state utilities would be unlikely to have sufficient surplus capacity during their own winter peak periods to satisfy the peak winter requirements of Maryland, since this capacity would be required on only rare occasions and solely for export. The existence of sufficient transmission interconnection capacity is also unlikely, since it would only be required on rare occasions.

Maryland is a member state of the Regional Greenhouse Gas Initiative and is actively encouraging the transition from fossil fuel generation to renewables plus storage. However, emphasis has been on renewable generation. Little attention has been paid to the storage requirements since sufficient conventional generation capacity is currently available to provide backup during periods of low/no renewable generation availability. However, ongoing efforts to discontinue use of existing fossil generation during a period of relatively rapid electric load growth is moving Maryland toward relying on renewable generation capacity to meet peak electricity needs, which would require that the renewable capacity necessary to meet peak demand be firmed with adequate electricity storage capacity.

Currently available short-duration storage systems such as the Tesla Megapack would probably be acceptable for peak shaving applications early in the transition. However, as transition progresses, medium-duration and long-duration storage solutions would be required to effectively compensate for multi-day interruptions and seasonal variations in renewable generation performance. Pumped hydro storage would likely be a suitable medium-duration storage approach, though proposed pumped hydro systems have met with public resistance. Green Hydrogen production and storage has been suggested as a long-duration storage option, but its capital and operating costs are currently excessive.

Originally published here.