The Use of the Organic Rankine Cycle in Smaller Power Plants

In a time with a very strong need to produce energy efficiently and with as less environmental impact as possible, ORC technology has grown more and more important, because it allows to use thermal energy that would otherwise be a simple wasted by-product.

Research is rapidly extending the application of the ORC technology to contexts that use fluids with low boiling points and reduced thermal gradient. Also, these fluids offer a high efficiency with smaller heat sources, compared to those of industrial processes, such as exhaust gases of large diesel engines, or organic pyrolysis.

The result is the possibility of using an ORC process in smaller plants, with power production under 50 kW and even as low as 10 kW.

The main protagonist od this evolution of ORC is the turbine, which is now highly efficient even at lower temperatures and requires less intense maintenance.

While steam is still the most utilized fluid in ORC plants, and is indeed the only type of fluid in large power plants (from 5 mW), smaller plants tend to employ alternative organic fluids, which make the management of the power plant easier and limit the need of specialised technicians.

A practical example of these new applications is heat recovery from the exhaust and cooling system of large diesel engines from 500 HP upwards. A simple calculation will give an idea of the positive impact of smaller plants. Considering that a 500HP diesel engine will generate about 800HP of heat, an ORC system with a 10% efficiency could generate 80HP of additional power, without using an extra drop of fuel.