Qualla: Mount Signal Solar

Mount Signal Solar: Introduction

Wed, 01 Apr 2026 00:00:00 GMT

From the air, the Mount Signal Solar facility looks like a strange agricultural development: regular rows covering mile after mile of the southern Imperial Valley, west of Calexico near the Mexican border. Up close, the rows resolve into more than three million thin-film solar panels tracking the arc of the sun on single-axis mounts, converting the intense desert radiation into electricity that flows north to San Diego and east to Southern California Edison's grid. At 794 megawatts peak capacity, Mount Signal Solar is among the largest photovoltaic power stations on Earth — built in three phases over nearly a decade on land the environmental groups supporting it described as low-productivity farmland.

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Mount Signal Solar: From Stirling Engines to Solar Panels

Wed, 01 Apr 2026 00:00:00 GMT

The facility's history began with a different technology. The California Energy Commission approved a project called SES Solar Two on September 29, 2010 — a power station designed around Stirling engine technology, which converts heat from focused sunlight into mechanical power. ...

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Mount Signal Solar: Phase One: The World's Largest Tracking Solar Farm

Wed, 01 Apr 2026 00:00:00 GMT

Construction on the first phase began in 2012, and Mount Signal 1 came online in 2014, providing 266 megawatts peak (206 megawatts AC) to San Diego Gas and Electric under a 25-year power purchase agreement. More than three million thin-film cadmium telluride photovoltaic modules ...

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Mount Signal Solar: Phases Two and Three

Wed, 01 Apr 2026 00:00:00 GMT

Phases two and three expanded the facility for Southern California Edison under separate power purchase agreements. Phase 3 — a 328 megawatt DC (254 megawatt AC) installation on 2,000 acres — came online in July 2018, using First Solar's Series 4 thin-film panels and Nextracker's...

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Mount Signal Solar: Thin-Film Technology at Scale

Wed, 01 Apr 2026 00:00:00 GMT

The choice of cadmium telluride thin-film panels from First Solar for the initial phase reflects a deliberate technology selection. CdTe thin-film panels produce electricity differently from the crystalline silicon panels that dominate the residential solar market: a thin semicon...

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Mount Signal Solar: Desert Power

Wed, 01 Apr 2026 00:00:00 GMT

The Imperial Valley's solar resource is exceptional: high insolation, low cloud cover, and the flat terrain that makes large-scale ground-mounted installations practical. Mount Signal 1's reported capacity factor of 29.7% — meaning the plant produces roughly 30% of what it would ...

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