Abstract: A machine has a potential energy raising device comprising a base container containing a liquid. A column has an upper gate at its top and a lower gate. The column extends above the base container and the column's bottom is below a liquid surface of the base container. A float is less dense than the liquid and denser than an ambient gas. A gas extraction path connects the upper gate to a pump to extract gas from the column. A guide in the liquid guides the float into the bottom of the column, so the float can float to the top of the column. A potential energy-kinetic energy conversion device near the potential raising device converts a potential energy of the float into kinetic energy when the float drops.