Uninterruptible power supply utilizing thermal energy source

Uninterruptible power supplies are provided that utilize a material to provide a source of thermal energy that may be converted to electrical energy to produce backup electrical power for a load. In some embodiments, a hot tank assembly is utilized to hold a liquid heated to a predetermined temperature. A closed-loop pipe containing, water for example, is immersed in the heated liquid. Upon the loss of primary power, the water flows into the heat exchanger where it is raised above its boiling temperature. The steam is then passed to a heat engine (e.g., a turbine-based system) that converts the heated steam to mechanical energy by causing the heat engine rotor to rotate. A generator is physically coupled to the heat engine so that the rotation of the heat engine rotor drives the generator. The generator produces AC power which is converted to DC and again back to AC before being provided to the load. In other embodiments, a solid mass, such as a block of iron, is heated to a predetermined temperature. The heat from the solid material is then converted to electrical energy for the load.