As Canada searches for cleaner ways to generate electricity, attention has turned to the vast store of heat that lies deep beneath the ground. Nowhere in the country is that heat easier to reach than in the sedimentary rock of southern Saskatchewan, near Estevan, where old oil wells long ago revealed how warm the deep layers become. The idea is not new: hot springs have been piped into spas and greenhouses in western Canada for generations. What is new is the scale of the ambition, as engineers now hope to drill several kilometres down and draw up enough heat to spin a turbine.

Geothermal energy holds clear advantages over wind and solar power. Unlike sun and wind, the warmth of the deep rock never fades; it flows day and night, in every season, which makes the supply of electricity steady and reliable. A geothermal plant burns no fuel and releases no greenhouse gases once it is running. The wells and machinery occupy only a small patch of land, far less than a wind or solar farm covers, and much of the equipment sits underground, so it does not crowd the horizon. Because the heat is always there, operators can count on a plant to run around the clock.