A compressed-air energy storage system according to embodiments of the present invention comprises a reversible mechanism to compress and expand air, one or more compressed air storage tanks, a control system, one or more heat exchangers, and, in certain embodiments of the invention, a motor-generator. Each RX sends data messages to its associated computer which includes an identifier identifying the TX transmitting the TX ID message, the signal strength of the received TX ID message, and a RX identifier. The pillow’s bottom surface is opposite the top surface, follows a bottom undulating pattern in the longitudinal direction, and is uniform in the lateral direction. By selectively controlling the length of time the microvalve is actuated, a range of colored inks is permitted to be ejected from the nozzle onto the receiver.