Abstract: A heat source heats air which rises in a duct having at least a one hundred meter vertical rise. Cold air enters the bottom of the duct through one or more horizontal passages containing vanes driven by moving air as a power source. The heat source may be a heat exchanger connected to an atomic reactor, a fossil fuel plant, a solar collector, or a geothermal heat supply. The heat exchanger may be located in the duct or in the one or more horizontal passages. In some applications, solar energy may directly heat the duct or a grid therein to cause an air flow.

Abstract: A control circuit for a step motor includes means for stepping the motor at a speed at which it can not be reliably stopped at a given step. The control circuit also includes a motor deceleration circuit that includes a bistable device, a pulse delay circuit with a given delay time and controlled by the bistable device, and a gating circuit all of which cooperate to decelerate the motor by supplying stepping pulses to the motor stator windings with a one step delay.