A modern steam engine, from Cyclone Power Technologies
CPT has two different engines: a high temp, hi pressure, hi efficiency one (~ 30%) and a lower temp (~15% eff) one, called the WHE. Other advantages over IC engines include multi-fuel, no need for transmission (related to torque curve of Rankine cycle.), no precise air-fuel mixture, no oil changes (water lubricated).
The Cyclone Waste Heat Engine (WHE) is a self-starting engine that operates in a low pressure, low temperature range. This feature allows the engine to run on waste heat emanating from an external source, such as the exhaust from an internal (or external) combustion engine, or the direct burning of biomass (i.e., processing garbage into methane would not be required). The Waste Heat Engine is also designed to run efficiently on solar heat without the installation of costly photovoltaic panels.
Another major commercial application includes solar-power generators for homes or businesses. By attaching inexpensive panels to a roof, enough heat can be produced to run the Waste Heat Engine. Cyclone believes that such a system could be installed at a price of approximately 20% of the cost of comparable photovoltaic panel systems, while also providing home owners with a back-up power supply. Excess electricity could be directed back to the power grid for electrical power credits
Cyclone power email (They are still in R&D, expect to be on the market in 2013-2014…)