Ultra-micro gas turbine generator

A method of forming elements of a gas turbine, the method comprising:

• forming an impeller element comprising a turbine and a compressor formed on a hollow shell structure, the hollow shell structure enabling a flow of air inside the impeller element,
• an impeller element constructed of a single piece of material, and having a hollow shell structure comprising a compressor element and a turbine element, the hollow shell structure having an interior comprising a cavity portion and a hollow axial bore portion, the cavity portion having a diameter greater than the largest diameter of the hollow axial bore portion,
• at least one bearing configured to support the impeller element such that the impeller element can rotate about its axis, and
• a combustion chamber external to the impeller element, and adapted to receive a fuel/air mixture whose combustion products are directed through the turbine element,
• wherein the hollow axial bore portion comprises an axial inlet opening that is concentric to the cavity portion of the impeller element and adapted to enable a flow of air to pass from the outside environment, along the length of the hollow axial bore portion, and through the cavity portion of the impeller element, and
• wherein the impeller element is formed by an additive manufacturing method.