CPE’s innovation begins with the modification of a classic gas Stirling heat engine into a hydraulic version that uses a benign working fluid in a supercritical state.
CPE’s conversion engine will use several slow-moving piston assemblies driven by a highly expansive working fluid.
Unlike conventional ORC engines, the CPE engine’s working fluid does not change phase during the engine cycle, thus conserving energy.
This design can produce very high pressures. Here is how it functions:
- Heat Source Activation:
A Sub-boiling thermal source fluid enters a heat exchanger, transferring its energy to the primary working fluid. In certain applications, an intermediate closed-loop working fluid can be used which then transfers heat to the primary working fluid i.e. a 2-stage system.
- Pressurization of Working Fluid:
The highly expansive working fluid then drives a piston which pressurizes hydraulic fluid typically between 2,000 – 5,000 psi (13.5 – 34.5 MPa). The engine operates without exhaust, odor, vibration or noise.
- Energy Conversion:
Pressurized hydraulic fluid from multiple pistons is combined to create a steady flow, which directly drives a hydraulic motor to spin a generator and produce electricity.
- Cooling and Reset:
At the end of the power stroke, a cooling cycle reduces the working fluid temperature and resets the piston, allowing the process to repeat seamlessly, approximately one to three cycles per minute.
Key Innovations:
Elimination of Turbines, Screw Expanders and Mechanical Transmissions:
It’s simplicity reduces maintenance costs, increases lifespan (projected 40 plus years) and reduces total cost of operation.
Slow, Powerful Piston Strokes:
The individual piston assembly design, at ~ 8 ft (2.5 m) in length, moves slowly while producing very high pressures. The expected cycle time ranges from one to three cycles per minute, resulting in low wear and tear on piston components.
Hydraulic, Mechanical Solution:
The CPE engine design will use common industry standard mechanical / hydraulic / electrical systems lowering complexity and allowing easily sourced components anywhere globally. This will allow for easy commercial standardization.
Special Working Fluid:
a key to the engine’s efficiency is a proven benign special working fluid which is maintained in a high-pressure, supercritical state to enhance its thermal expansion rate in the Sub-boiling temperature range without changing its phase.
Rapid On/Off Capability:
The CPE engine can be designed to cease operation immediately and restart within a few minutes. This would make it ideal for stabilizing power grids using intermittent renewables.
Efficient Cooling:
CPE’s engine should operate efficiently with much less water consumed than is required for conventional ORC and other alternative engine types.
Modular Design:
As designed, individual heat exchanger and piston assemblies could be isolated enabling easy component maintenance or even replacement during continuous operation of the remaining engine cylinders; a unique feature.