Grid-Scale Storage Dispatch: Battery vs Pumped Hydro vs CAES

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Grid Conditions

Renewable volatility 45%

Demand peak sharpness 50%

Battery bank size 40 MWh

Simulated days per minute 2.0x

Storage State of Charge

Battery0%

Pumped hydro0%

CAES cavern0%

Today's Dispatch Result

Curtailment avoided

0 MWh

Curtailed anyway

0 MWh

Round-trip efficiency

—

Unmet demand

0 MWh

How it works

Every simulated hour the dispatcher compares generation to demand and moves the three storage technologies in merit order — fastest, most efficient response first:

net(t) = demand(t) − [solar(t) + wind(t)]
net > 0  → deficit  → discharge battery, then hydro, then CAES
net < 0  → surplus  → charge battery, then hydro, then CAES

Each technology has its own power rating (MW, how fast it can move energy), energy capacity (MWh, how much it can hold) and round-trip efficiency η — the fraction of stored energy you get back:

energy drawn from store  = delivered energy / √η   (discharge)
energy added to store    = surplus energy × √η    (charge)

Splitting η into equal charge/discharge legs (√η each way) is the standard approximation for cycle efficiency. Battery ≈ 90% round-trip and reacts fastest; pumped hydro ≈ 80% with a large reservoir; compressed-air energy storage (CAES) ≈ 65% because heat is lost when air is compressed and must be reheated on release — cheapest per MWh of capacity but the leakiest.

Curtailment avoided — solar/wind energy that would have been wasted (no buyer, no storage room) but was captured because a tank still had headroom.
Curtailed anyway — surplus that arrived faster than all three technologies combined could absorb it.
Unmet demand — a deficit that remained after every store ran empty; the real-world equivalent of a rolling blackout.
Battery bank size — resize the fastest-responding tank and watch how much curtailment and unmet demand it alone can remove, holding pumped hydro and CAES fixed.

This merit-order logic mirrors how real grid operators (CAISO, National Grid ESO) schedule storage fleets: cheap, fast, high-efficiency assets absorb the first slice of every swing, while large, slower, lossier assets soak up what's left.

Solar / wind supply City demand Charging flow Discharging flow

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