Tomorrow, GE chairman and CEO Jeffrey Immelt will announce that his company — the fifth largest in the U.S. — is devoting itself to what it calls "ecomagination": the growth of clean energy, clean water, and related technologies.

This is a very big deal, about which Grist will have more to say. For now, go read Joel Makower, who — as with most big moves in the sustainable business sphere — has been working on this behind the scenes.

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Ecomagination, says Immelt, aims to "focus our unique energy, technology, manufacturing, and infrastructure capabilities to develop tomorrow’s solutions such as solar energy, hybrid locomotives, fuel cells, lower-emission aircraft engines, lighter and stronger materials, efficient lighting, and water purification technology."

By almost any measure, it’s a bold move. For GE, the fifth-largest U.S. company, it represents a strategic shift that could catalyze competition among some of the world’s largest companies to accelerate the emerging clean-tech economy.