It's Monday. The largest battery in the country may have gone up without a ribbon cutting, a press release, or a straight answer about its size. Counting shipping containers from orbit is now energy reporting.
In today's edition:
🔋 Big Story: xAI quietly assembles a Megapack fleet in Memphis
🔌 Quick Hits: DC breakers, a borehole reactor, a 206 Wh/kg sodium cell
💰 Capital: the Pentagon's $5B compute loan talks
📋 Policy Watch: a vacated DOE must-run order
📊 Chart of the Day: ERCOT's load record, again
🗓️ Upcoming In-Person Event: Global Capital in Energy Tech
Grid Innovation Hub, presented with Cathay Innovation
Thursday, October 1, 4:00 to 7:00 PM PT · Cathay Innovation, 101 Mission St, San Francisco
Grid Innovation Hub and Climate Capital Strategist MJ Willmore are putting 100 investors, founders, and operators in one room with Cathay Innovation, a global fund backing energy tech from the US to China. A fireside chat with Cathay partner Matthieu Soulé on where cross-border capital is moving, then panels on software and AI, and on infrastructure and data centers.
This is an invite-only gathering and registration is approval-based, so space is limited, but Grid Innovation Hub subscribers are highly encouraged to register.
The Big Story
xAI builds a Megapack fleet behind the meter in Memphis
Canary Media counted 720 Tesla Megapacks in July 11 satellite imagery of xAI's Colossus 2 data center outside Memphis, a fleet the outlet estimates at roughly 2.8 gigawatt-hours and between 720 and 1,400 megawatts depending on the model. Executives put it higher. xAI developer Riley Trettel told the TVA board in August the site holds 3.3 GWh, enough, he said, to power Memphis for two hours, and MLGW CEO Doug McGowan said in early September he believed 2,000 MW sat behind the meter. Neither xAI nor TVA would confirm a figure. If the larger numbers hold, the site passes California's Edwards and Sanborn, at 3,287 MWh, as the country's biggest grid battery.
"It's the world's largest supercomputer today, but it's also got the world's largest grid-connected battery system."
MLGW cleared the site through a power interruption program requiring enough behind-the-meter generation and storage to come off the grid for four hours during curtailment, McGowan said.
TVA's board approved a direct grid hookup on August 20, the day Trettel described the fleet to directors.
Tesla filings show xAI bought $430 million of Megapacks last year, and another $405 million in the first half of 2026.
Sixty-nine mobile gas generators ran at Colossus 2 in July without air permits, on the argument that they are mobile; the Southern Environmental Law Center has sued.
Source: Canary Media
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Quick Hits
Technology milestones from across the grid
Five technology stories from across the stack, from silicon carbide breakers to a reactor down a borehole.
SolarEdge and Infineon expanded their partnership on silicon-carbide JFET solid-state breakers for 800-volt DC distribution, the architecture hyperscalers are adopting to cut conversion losses in AI halls. Smart Energy International
Deep Fission lowered a full-size prototype canister for its underground Gravity reactor into a borehole and retrieved it with standard drilling rigs, the step its siting case rests on. World Nuclear News
Chinese researchers reported a 15.8 amp-hour sodium-ion pouch cell at 206 watt-hours per kilogram on an iron-mediated cathode, with 99% redox reversibility, nearing LFP density. ESS News
Oracle issued an RFP for 2 GW of new renewables and pledged a public environmental-data dashboard for Project Jupiter, its answer to opposition to the site's gas microgrid. Latitude Media
The DOE's geothermal office launched a $300,000 GEMS Prize for algorithms that can pick hidden geothermal systems out of GeoDAWN survey data over Nevada. ThinkGeoEnergy
The Capital Stack
Pentagon weighs a $5 billion loan to an AI compute developer
The Pentagon's Office of Strategic Capital is in talks to lend Fluidstack roughly $5 billion, according to a report relayed by Data Center Dynamics. A loan that size from a defense-industrial financing office opens a new category of public capital for AI data center buildout, alongside the DOE's loan programs rather than inside them. Nothing is signed, and neither party has confirmed it.
Source: Data Center Dynamics
Also in the capital stack:
Oklo signed a $1 billion at-the-market equity agreement with ten banks, replacing a program that already raised about $1 billion, a second shelf for a reactor developer years from revenue. Benzinga
The Hydrogen Council and McKinsey put committed clean hydrogen investment past $130 billion across 570-plus projects, roughly 90% of them operating or building. Smart Energy International
Policy Watch
The D.C. Circuit vacated the DOE's Section 202(c) order keeping Consumers Energy's Campbell coal plant online, weakening the footing of the department's other must-run orders after what Utility Dive put at $259 million in compliance costs. Utility Dive
Maryland faces calls from 60-plus groups for a statewide data center pause after 14 of its 24 jurisdictions adopted temporary bans, a siting bottleneck that bites before generation. Inside Climate News
Chart of the Day
ERCOT's summer load keeps setting records
ERCOT's hourly load averaged a record 74.5 GW in the week ending August 22, 10% above summer 2025's best week and 6% above the 70.0 GW record set in 2023. Six straight weeks cleared that old mark.
Source: EIA Today in Energy · September 3, 2026
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