Waterpower Intelligence Theater Sponsored Content Session – Petrotech + PG&E
CLEAN CURRENTS 2025
Time: 11:00 AM - 12:00 PM
Day: 10/15/2025
Room Number: Waterpower Intelligence Theater
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Presentations in this session are:
Improved Method for Emergency Stator Core Hot Spot Repair, presented by Hyrum Fairbanks, Pacific Gas and Electric Company
Innovative Pumped Storage, presented by Brett Bauer, Canyon Hydro; Lev Ring, Sage Geosystems; and Jackson Post, Petrotech
Details are described below.
Improved Method for Emergency Stator Core Hot Spot Repair, presented by Hyrum Fairbanks, Pacific Gas and Electric Company
Pacific Gas and Electric Company (PG&E) developed this method in-house and successfully used it to repair the Helms Unit 2 stator.
Background:
While the preferred method for repairing generator stator cores may be to “re-stack” the core and replace damaged laminations, it is not always cost effective to do so; the long lead time of the material, the availability of craft and experts needed to perform the work, the high cost, and extended outage required may make immediate re-stack infeasible.
A less optimal repair method that has been used in the hydro industry is to either separate the shorted laminations using a pack spreader and inserting insulation, or by using hand grinders and acid etching equipment to grind/dissolve away the damage and apply weeping epoxy to restore insulation. The disadvantage of this method is that it also requires significant outage time due to the need to repair the rough surface left behind by grinding. Acid etching takes significant time to separate laminations, and, after a retest, often the task requires multiple iterations to restore the insulation.
At PG&E, we have developed a modified repair method that combines surface machining with acid etching and weeping epoxy for faster, more effective, and more consistent repair.
Innovative Pumped Storage, presented by Brett Bauer, Canyon Hydro; Lev Ring, Sage Geosystems; and Jackson Post, Petrotech
Sage Geosystems has pioneered a novel subsurface long-duration energy storage known as Earth Storage, which turns deep, low-permeability rock into a rechargeable pressure vessel.
This system injects water into a single-well fractured reservoir until wellhead pressure is about 4,000 psi, storing potential energy by ballooning “lung” fractures against in-situ stresses. Upon release, the pressurized water drives a surface-mounted Pelton turbine to generate electricity, offering a long-duration, grid-stabilizing alternative to conventional lithium-ion batteries.
To meet the demands of this high-head, variable-flow application, Sage partnered with Canyon Hydro, whose precision-engineered Pelton turbine features a unique and robust runner design to handle the stresses of this 3-MW, 1,800-rpm application. As the reservoir pressure decreases during discharge, a VFD and Petrotech's Hydro Turbine and Balance of Plant control system provide precise control of turbine speed and generator load to maintain optimum ratio of jet velocity to runner speed.
By coupling modular, high-head hydraulics with adaptive controls, Earth Storage delivers dispatchable power, inertia, and fast frequency response—filling the long-duration gap that lithium-ion and pumped hydro cannot reliably or economically address in many markets.
Presenters
