Waste Heat Recovery
Concepts NREC, with over 60 years of turbomachinery expertise, has developed the most compact, high-speed, hermetically-sealed turbogenerator, the CN300. Nominally rated for 300 kWe, the CN300 is designed for converting low temperature heat to electric power using an Organic Rankine Cycle (ORC) process.
Increasing concerns for protecting the environment and the escalating cost of energy itself have raised interest in energy conservation to an all-time high. This interest extends to waste heat recovery systems. These systems produce electric power by converting thermal energy to electrical energy. And, when site conditions involve temperatures too low for conventional heat recovery systems, ORC processes become the best solution. These are typically defined as any heat source at temperatures below 800oF. In fact, according to one U.S. Department of Energy report, there could be as much as 1.5 to 2.0 quadrillion BTU/year of heat with temperatures below 500oF available from exhaust gas streams in the industrial sector alone. Naturally occurring heat sources may be just as plentiful.
The CN300 was developed specifically as an ORC energy recovery machine. It is a patent-pending, hermetically-sealed design, with an ORC turbine and permanent magnet generator directly coupled that improves mechanical efficiency by up to 10 percentage points over conventional designs.
The CN300 turbine is a one-to-four stage, axial, impulse rotor-nozzle design configured in a subassembly cartridge arrangement. With its flexible flow path design, the CN300 can generate up to 330 kWe over a wide range of inlet conditions. It can also be customized by changing the aerodynamic shape of the turbine’s stages of rotors and nozzle stators. The basic design accommodates a wide range of turbine rotor and nozzle cartridges, while keeping the same housing and generator. Using a standardized turbine housing and generator this way eliminates most of the non-recurring engineering and manufacturing costs that would otherwise result from designing units to handle the multitude of heat recovery site conditions.
By using magnetic bearings, all of the cost, weight, space, interconnecting controls, and general complexity of an auxiliary bearing lube oil system are eliminated. The use of active magnetic bearings also means that the separate vibration probes and/or proximity sensors that would normally be required to monitor gearbox shaft vibration levels are also eliminated.
The CN300 also has state-of-the-art electric generator drive controls. As a result, it doesn’t require an independent, electro-mechanical speed governor to safeguard against turbine over speeding.
The hermetically-sealed CN300 also eliminates the need for any shaft seals that keep the organic fluid within the ORC system’s closed loop piping.
With its inherent flexibility, the CN300 offers more power and revenue for a given heat source, greatly reduced operating and maintenance costs, increased reliability, and a significantly smaller footprint than any other ORC turbogenerator available in the world today. To consider anything else for low temperature waste heat recovery systems could be an expensive mistake.
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