Pritchard engines are referred to as ‘external’ combustion engines. The fuel is combusted in a furnace. The heat released is used to produce steam that drives a piston up and down. Fuel is not exploded inside a cylinder as it is in the conventional ‘internal’ combustion engine.

All of the original engines that gave rise to the industrial revolution of the 18th and 19th centuries were external combustion engines. Furnace systems were already very advanced by the 18th century having been perfected over many hundreds of years before that in foundries and smithies. Internal combustion engines were only developed at the very end of the 19th century.

It is a well-established engineering fact that external combustion engines such as the Pritchard units produce as little as one twentieth of the emissions of a similar size internal combustion engine.  The reasons for this are numerous and the results vary depending on engine design, fuel type, load and other factors.  Essentially, the external combustion engine delivers a more efficient combustion process that greatly reduces the production of toxic particulates, unburnt hydrocarbons, carbon monoxide and nitrous oxide.

It should be noted that nitrous oxide is a far more potent greenhouse gas than carbon dioxide.

Greenhouse gas emissions from Pritchard Power Systems are reduced to negligible levels when using cultivated crop fuels, and are also low when using fossil fuels.

Of course a Pritchard engine driven by steam generated from solar heat would cause no pollution of any sort.