Fourth-grader Patrick White thinks his new subterranean school, Terraset Elementary in Reston, is terrific. But he's thought about the unthinkable: "If there's an earthquake, I'll go back to my old school."

Patrick White notwithstanding, there wasn't much thought about earthquakes at Terraset yesterday when it opened its doors to 850 Fairfax County pupils, many of whom had been going to school in trailers and other temporary buildings since September.

Designed to be heated by solar power and built into a hill to conserve energy, Terraset has become a showcase for the Fairfax school system, which has had to retrench its building program because of voter resistance to bond-financed construction.

In fact, Terraset, which is attracting media attention from around the nation because of its energy-conscious construction, had to be built with bonds sold by the Virginia Public School Authority because Fairfax voters said no to a local bond issue that would have financed the school.

Terraset won't start capturing the sun's rays and converting them into energy to heat and cool until mid-April, when all the equipment is installed, and the heat-reclamation system won't be fully operational until next month. But pupils, teachers and visitors found plenty to marvel about as they explored the curved corridors.

Built in the "open plan" design, Terraset has four "learning centers" instead of classrooms, all of them with curved walls to reduce dead space that has to be heated. Architect Douglas N. Carter, relying heavily on advice from teachers, designed the learning circles so that each has small, intimate areas for students who can't learn well in an open environment.

The graphics, bold solids and stripes with outsized numbers identifying each learning center, reflect the growing trend away from the institutional look in schools.

There also are walls with large port-hole cutouts, a library with a skylight set into a convex ceiling and pedestrian bridges connecting the school to the parking area.

At the main approach to Terraset is a canopy of bright orange tubular girders that will hold the solar collectors. Under this canopy is the entrance. Covering the entire roof is three feet of earth - a shield against summer's heat and winter's cold. Though largely underground, the building has broad windows cut into the hill that provide a view in three directions.

It's possible that only a trip to Willie Wonka's chocolate factory would have opened eyes wider or evoked more oohs and ahs. Principal Margie W. Thompson, excited as any of her pupil, led a group of them in an impromptu snake dance around the basketball court in the gymnasium.

Spotting physical education teacher Dan Durbeck, she shouted across the tile floor, "Is this the way you do it, Mr. Durbeck?"

Dressed in an orange and yellow Terraset, T-shirt, Alton C. Hlavin, head of the Fairfax school system's construction program, tried valiantly to explain the complicated energy conservation system in 30 seconds or less for television reporters.

But the politics of school construction was never far from his mind. Surveying the purple carpeted corridors, he said, "All this 'eyewash' amounts to .0001 per cent of the total cost. The graphics cost $1,200. The walls are concrete blocks that have been painted. You don't have to pay a lot to get something that looks good."

Excluding the solar-heating hardware, which is being financed by a $600,000 grant from the Saudi Arabian government, Terraset cost between $35 and $36 a square foot to build, compared to the $32 to $33 per-square-foot cost of a conventional school, according to Hlavin. The total cost is $3.4 million.

Some of the extra money went into the heat reclamation system, which is expected to result in a $20,000 annual energy saving. That means, Hlavin said, that the system should pay for itself in 10 years, or less, if the cost of electricity continues to rise.

Some reclamation will come from recycling the heat from lights and human bodies. But most will come from saving the heat thrown off from air-cooling machines and using it to heat stored water that is then used to warm the building.

The solar system, when it is operational, is expected to result in another $10,000 annual saving. Thus, while a conventional school the same size would consume $40,000 worth of energy annually, Terraset would use only $10,000 worth - assuming all the systems work as anticipated.

In the morning, school system engineer Anthony A. Martin, who manages the Terraset conservation program, checked the school's electric meter, then drove off to nearby Hunters Woods School, which was built with conventional heating methods.

"We're going to have a race," he said, "and just see who can come in first" - to use the least amount of energy.