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Earth Notes: Solar Power

Ancient doorways at Chaco Canyon's Pueblo Bonito.

Flagstaff, AZ – Earth Notes: Solar Power

Centuries ago, the builders of Chaco Canyon's Pueblo Bonito knew the secrets of solar heating and air conditioning without complicated equipment, fuel, or electricity.

They oriented their pueblo's curved wall opening to the south, like a parabolic mirror. They designed their beehive of 700 rooms with four stories at the wall's northeastern end, but only one story at its southern end. This stair stepping reflects the winter sun's morning energy from house fronts onto the central plaza, where cooking and many other activities took place.

By sundown the solid masonry had absorbed enough heat to warm the rooms through most of the night. In the summer, the shadow of the cliff against which the pueblo nestles shields the plaza from sun glare for much of the day.

The building's sheer size also produces relatively stable conditions: despite wild temperature swings outside, room temperature varies on average only about ten degrees Fahrenheit.

Modern homeowners in the Southwest are well advised to learn from these eleventh-century architects. We can take advantage of the low-angle winter sun by orienting buildings appropriately, using large windows in south-facing walls. We can use the insulating properties of such natural materials as adobe and straw to keep rooms cool during the day and warm at night.

Building with solar principles makes sense in the Southwest. But so could using solar energy to create electricity. Together, it's estimated direct and indirect solar power could supply as much as 20 percent of the nation's energy needs.

-Michael Engelhard