PUMPED STORAGE HYDRO

ABSAROKA ENERGY

NorthWestern Energy Resource Technology

Forum

November 29, 2017

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Storage Technology Comparison

Source: Bloomberg New Energy Finance Database “The future of Energy Storage Technologies and Policy”

99% of Storage is Pumped Hydro

REVERSIBLE TURBINE

Motor Generator

Reversible PumpValve

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TERNARY PROVEN TECHNOLOGY(Gordon Butte Pumped Storage Hydro)

TERNARY “BEST IN CLASS”

FIXE

DSPE

ED

VARSPEED

TERN

ARY

100%

50%

0%

-100%

POWERVARIATION

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ULTIMATE FLEXIBLE CAPACITYPSH can move faster (20 MW/sec) than gas (40 MW/min)

TYPICAL UTILITY DISPATCH MODES

LEAST COST – prioritize the dispatch of the least cost

resources to serve the load.

ENVIRONMENTAL – prioritize the most

environmentally friendly resources to serve the load.

SYSTEM RELIABILITY – prioritize the dispatch to

provide the most stability and security to the system.

COMPLICATIONS - must run facilities, PURPA

contracts, run-of-river hydro

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Source: Energy + Environmental Economics “Gordon Butte Pumped Storage:

Colstrip 1&2 Replacement Analysis”

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ANCILLARY SERVICES■ Inertial response

■ Governor response, frequency response, or primary frequency control

■ Frequency regulations, regulation reserve, or primary frequency control

■ Flexibility reserve

■ Contingency spinning reserve

■ Contingency non-spinning reserve

■ Replacement / supplemental reserve

■ Load following

■ Load leveling / energy arbitrage

■ Generating capacity

■ Reduced environmental emissions

■ Integration of variable energy resources (VERs)

■ Reduced cycling and ramping of thermal units

■ Other portfolio effects

■ Reduced transmission congestion

■ Transmission deferral

■ Voltage support

■ Improved dynamic stability

■ Black start capability

■ Energy security

www.gordonbuttepumpedstorage.com

Rhett Hurless/ Sr. VP President &

COO

(406) 585-3006