Imagine an engine that's 30 percent smaller than a traditional piston design of like output, and that runs smoothly, with less noise and vibration. Plus, it burns several types of fuel. That's the Global X rotary engine, which was recently demonstrated powering a 3.2 KW generator.

The Global X rotary engine is a non-Wankel development. Global NRG is using the new engine with a 3.2 KW alternator application to showcase its power-to-weight capabilities.

The Global X Mini has nearly 2 horsepower per pound (3.3 kW per kilogram). It's 30 percent smaller and lighter than the equivalent spark-ignited gasoline engine it replaces, and can be up to 75 percent smaller than a like-output diesel engine.

Even better, the engine's design means that it has no poppet valves and exhaust is balanced through over-expansion, removing the need for a muffler. The X rotary engine can be as much as 20 percent more fuel efficient than its gasoline counterpart and 50 percent more efficient than an equivalent diesel engine. What's more, the Global X engine can be powered by gasoline, diesel, natural gas, biogas or JP-8 fuel. The design, is scalable from 1 horsepower to over 1,000.

One of the secrets in the X Engine's design is the unique rotary cycle. Unlike a Wankel rotary, which uses a triangular center rotor, the X Engine has an oval-shaped rotary which rotates in a cloverleaf-like core. This creates higher compression with better seals and exhaust pressure. It also creates a larger expansion volume than compression volume, similar to the high-efficiency Atkinson Cycle engine used in hybrid vehicles.

The design of the X Engine also allows for cycle skipping for lower-output needs and low-RPM power. In larger versions of the engine, water can be injected into chambers after the exhaust cycle to cool the engine when under high loads.

The engine being used in the biogas generator is a four-stroke 70cc version that produces about 4.3 horsepower (3.2 kW) at 10,000 rpm. Global NRG expects to have the engine producing 5 hp (3.7 kW) soon.