Electromechanical flywheel with evacuation system

1. An electromechanical flywheel with a molecular drag pump comprising:

a cylindrical motor-generator rotor surrounding a motor-generator stator;

the motor-generator rotor encircled by and fixed to a cylindrical flywheel mass;

a central axis about which the motor-generator rotor and flywheel mass rotate;

a planar drag pump including a labyrinth ring with an annular working surface;

the working surface in a plane about perpendicular to the central axis and centered on the central axis;

the working surface spaced apart from an end surface of the flywheel mass by a drag pump gap; and,

an elevator that moves the working surface toward the flywheel mass end surface when the gap is larger than a first selected dimension and that moves the working surface away from the flywheel mass end surface when the gap is smaller than a second selected dimension.

2. The electromechanical flywheel of claim 1 wherein the labyrinth ring is located between the flywheel mass end surface and an elevator support located above the flywheel mass end surface.

3. The electromechanical flywheel of claim 2 wherein three elevators are equally spaced around a circumference of the labyrinth ring.

4. The electromechanical flywheel of claim 1 wherein the elevator includes an electromagnetic actuator, the actuator comprising an electrical coil surrounding a back iron arranged to magnetically attract a platen coupled via a link to the labyrinth ring for adjusting the gap.

5. The electromechanical flywheel of claim 4 wherein the link passes through a hole centrally located in the back iron.

6. The electromechanical flywheel of claim 5 wherein the elevator includes a spring that encircles the link and urges the platen away from the back iron for increasing the gap.

7. In an electromechanical flywheel with a molecular drag pump, a method of moving a gas from a flywheel mass periphery toward a flywheel mass axis of rotation, the method comprising the steps of:

providing a cylindrical flywheel mass for rotation about a central flywheel axis;

forming a planar drag pump including an annular labyrinth ring that spaced apart from an end of the flywheel mass by a drag pump gap;

during operation of the drag pump, moving the gas along a gas path including a first path portion with a first path direction followed by a second path portion with a second path direction;

wherein the first path portion is a space encircling the flywheel mass and the first path direction is parallel to the axis; and,

wherein the second path portion is a space that does not encircle the flywheel mass and the second path direction is perpendicular to the axis.

8. The method of claim 7 further comprising the steps of:

providing a labyrinth ring elevator;

for increasing flywheel mass angular speeds, compensating for flywheel mass contraction by moving the labyrinth ring toward the flywheel mass end to maintain a substantially constant drag pump gap; and,

for decreasing flywheel mass angular speeds, compensating for flywheel mass expansion by moving the labyrinth ring away from the flywheel mass to maintain a substantially constant drag pump gap.

9. In an electromechanical flywheel, a method of configuring rotating parts that is enabled by a variable geometry drag pump, the method comprising the steps of:

providing a flywheel mass made from a carbon composite;

providing a rotor made from a metal;

encircling the rotor with the mass;

engaging the rotor and the mass via an interference fit therebetween;

providing a variable geometry planar drag pump with a drag pump gap between a labyrinth ring and an end of the flywheel mass; and,

during variable speed operation of the flywheel mass in an evacuated space, controlling the drag pump gap to limit the temperature rise of the flywheel mass.

10. The method of claim 9 wherein the labyrinth ring lies in a plane perpendicular to a flywheel mass axis of rotation and three electromagnetic elevators provide for moving the ring along the axis.

11. The method of claim 9 wherein the labyrinth ring moves to adjust the drag pump gap in response to angular velocity of the flywheel mass.

12. The method of claim 9 wherein the labyrinth ring moves to adjust the drag pump gap in response to a sensor measurement that indicates the gap.