Proe Power Systems, LLC

”Making Thermodynamics a Household Word” ®

Proe Afterburning™ Cycle:
a Clean, Low Cost Alternative to
Fuel Cells and Stirling Engines

Modern Materials and Thermodynamics Applied to 19th Century Engines to Meet 21st Century Emission and Fuel Economy Requirements

1890PumpProe Power Systems' Proe Afterburning™ Cycle Engine builds upon technology developed and proven by George Brayton and John Ericsson, both brilliant 19th century engineers who successfully pioneered modern engine development (see the Brayton and Ericsson page for more information).  George Brayton provided the engines that propelled the US Navy’s first submarine, Holland, and John Ericsson is best known as the designer of the civil war ironclad battleship Monitor. In the days before the now familiar automotive-type gasoline (Otto Cycle) engine, several companies made very successful "constant pressure combustion” engines that were based on Brayton’s and Ericsson’s innovations. Unlike gasoline or Diesel engines that produce power by the pressure from burning gases in a cylinder, these engines produced power by compressing air in one cylinder, heating the air, and then expanding it in a larger cylinder.  Brayton’s engine directly heated the air in a burner between the cylinders.  Ericsson’s engine indirectly heated the air, both between the cylinders and within the larger cylinder.  Thousands of these engines were used in the late 19th century for pumping water and powering machinery.   The Otto Cycle gasoline engine eventually overwhelmed the early Brayton, Ericsson and other engines for everyday powerplants.  However, the Brayton engine is still highly successful, with pistons and cylinders replaced by rotor blades, as the modern gas turbine jet engine.  Ericsson’s contributions are also still highly evident in the recuperated, intercooled, and reheated versions of modern gas turbine engines.

The need for low emissions and fuel consumption has renewed interest in Brayton and Ericsson reciprocating engines.  Unlike internal combustion engines, they have continuous and constant pressure combustion that can be made very clean burning. Unlike turbine engines, reciprocating versions of these engines can be made and maintained in automotive type production and maintenance facilities; resulting in a much lower initial investment and long term operating costs.  Proe Power Systems has taken the reciprocating Brayton and Ericsson Cycle into the 21st century by: by utilizing 21st century heat transfer techniques; by applying modern stainless steel materials; by developing the low-pressure, continuous, Afterburning combustion process and by inventing the Proe 90TM recuperator.

A Breakthrough Technology:

The patented Proe Afterburning™ Cycle Engine effectively integrates the combustion and power producing processes. The resulting engine is capable of high thermodynamic efficiency with complete, continuous, and clean combustion.  It not only works as an efficient stand-alone engine capable of efficient power generation from gaseous, liquid and solid fuels but is uniquely qualified for Symbiotic™ waste heat recovery – a process than not only provides mechanical or electrical power from waste heat, but improves the efficiency and emissions of the original combustion process itself.

Fuel Cells Aren’t the Answer: Our new innovations are a step forward in development of the Proe Afterburning™ Cycle engine as a low cost fuel cell alternative. Fuel Cells are very efficient and have no significant emissions when fueled by hydrogen gas. However, when using fuels available in today's infrastructure (gasoline, propane, LPG etc.) fuel cells not only require an expensive fuel cell stack with hydrogen, air, and water control systems but also a reformer to extract the hydrogen from the fuel. The carbon portion of the fuel cannot be used by the fuel cell stack and is wasted by being exhausted from the reformer as carbon dioxide. Proe Power Systems' Proe Afterburning™ Cycle Engine has equivalent fuel efficiency and exhaust emissions at a much lower initial cost. The engine is less complex than current automotive engines but has the patented, low pressure, continuous combustion process that produces lower emissions than any competitive power system.  For comparison data, click on the Fuel Cell comparison page.

Stirling Engines Aren’t the Answer Either: The Proe Afterburning™ cycle provides the means to achieve the high efficiencies that were promised by Stirling engines but have never been achieved in practice. Stirling engines have a major efficiency loss: their external burners must heat the combustion air from cool room temperature to the high engine operating temperature – an extremely wasteful combustion process.  The Proe Afterburning™ Cycle’s patented regenerative heating process allows combustion to be initiated at the high temperature of the expander exhaust and makes all the heat of combustion available to the cycle.  This breakthrough difference vastly improves fuel efficiency and makes the Proe Afterburning™ Engine a practical means to achieving a highly efficient, clean combustion engine.

The Proe Afterburning™ Cycle Engine also avoids the problem the Stirling Engine has in becoming "heat bound". An open cycle, such as the Proe Afterburning™ cycle and standard car and truck engines, receives a fresh charge of cold air and exhausts warm air during each cycle. The temperature difference between inlet and exhaust represents heat that, even though unavailable for making power, must be rejected to allow the engine to continue to run. The closed Stirling cycle also has to reject a corresponding amount of heat, but lacking a fresh air intake and exhaust, must reject all that additional heat through the engine walls. For this reason, the cooling system on a Stirling engine must be about 4 times larger than the cooling system for a corresponding Proe Afterburning™ Engine.  (For more on the thermodynamics of Stirling and Proe Afterburning™ engines see the Stirling Comparison Adobe File.)

The Stirling cycle has a final significant practical engineering problem – it is unable to generate practical power levels unless it uses a pressurized, high heat capacity, gas as its working fluid.   The usual working gases are helium and hydrogen, both of which are difficult to retain in a high temperature seal environment.   For this reason, Stirling engines are generally connected to regulated welders’ gas bottles to continuously replenish the hydrogen or helium lost through the seals.  (Of course there are safety concerns with hot high-pressure hydrogen leakage near a burner.)   One company has even tried the more expensive, complex, and less reliable approach of adding a water electrolysis unit to generate the hydrogen needed to offset their leaky seals.    Conversely, the Proe Afterburning™ engine, like aircraft and automotive engines, is able to produce effective and efficient engine power levels by simply using the air for its working fluid.   No new technology is needed to seal our engines.  Conventional, low cost, and well proven rings and valves; as commonly found in air compressors and automotive engines; are all that are needed to provide highly effective sealing.

New Technology Using Conventional Engine Parts:  The Proe Afterburning™ Cycle Engine uses simple, conventional, engine components to provide an engine having low fuel consumption while meeting 21st century environmental requirements. Although well suited to gasoline fuel, the cycle is ideal for alternative fuels such as CNG, Propane, Wood Chips, and Hydrogen. Powerplants using this cycle will soon become viable, low-cost, alternatives to fuel cells, diesel engines and gas turbine engines.

All components of both the Proe Afterburning™ Cycle Engine and its Proe 90TM recuperator can be manufactured in any machine shop capable of rebuilding an automobile engine. The simple construction allows small manufacturers to effectively enter the 21st century power market with minimal new investment while still producing powerplants having efficiency and emissions performance competitive with fuel cells or microturbines.

Distributed Power Generation, Combined Heating and Power, and Village Power:

The Proe Afterburning™ Cycle is ideally suited to Distributed Power Generation. The high efficiency, low emissions, ability to use a wide variety of fuels and simplicity of construction will soon make it the engine of choice for these applications. The engine's ability to directly and cleanly combust solid fuels and cellulosic biomass without the need for complex and costly gasification or digestion allows the engine to be directly fueled by readily available renewable resources and is an excellent match to Village Power requirements.

Current Projects:

Front Isosmall.jpgProe Power Systems will soon introduce the PPS 250tm solid biofuel powerplant.  This powerplant will revolutionize the biofuel power generation market by its combination of low initial cost, efficient use of virtually unprocessed biofuel, low maintenance, and highly reliable service.  The powerplants will produce a nominal 250 kWe of electric power and approximately 450 kWt of heating (i.e. 2000 gallons of hot water per hour) for CHP. They will also be capable of efficient load following from 30 to 280 kWe.  Look for additional information in the near future.

Further Information:

Proe Afterburning™ Engine technology has developed from Proe Power Systems’ innovative work on the Afterburning Ericsson Cycle Engine.  Significant improvements have recently been made that resulted in the evolution from the Afterburning Ericsson cycle to the Proe Afterburning™ cycle.   An Afterburning Ericsson Cycle Engine TechPak is listed with, the marketplace for licensable technologies from all over the world. (The Afterburning Ericsson Cycle Engine was selected as a NASA Featured Technology.)  Proe Power Systems presented the Afterburning Ericsson Cycle Engine at the Society of Automotive Engineers’ 1999 Future Transportation Technology Conference and a paper on the Proe 90tm gas turbine recuperator was presented at the 2002 American Society of Mechanical Engineers Turbo Expo. Additional information is available from:



Richard Proeschel, P.E.
Chairman & Program Manager
Proe Power Systems, LLC
5072 Morning Song Drive
Medina OH 44256-6747
Phone: (800)315-0084 ext. 600
International Phone: 1-(330)723-4469 ext. 600
Fax: (330)723-4469



·         Proe 90TM Gas Turbine Recuperator Page

·         Proe Power Systems HRPGTM Heat Recovery Power Generator Brochure  (Adobe pdf file)