Technologies
The basic underlying technologies in the FreeSpin™ In-line Turboexpander (FIT) have been deployed by parent company Calnetix Technologies in multiple applications around the world.
The FIT consists of a high-performance, high-speed permanent magnet generator with an integrated radial in-flow expansion turbine and low loss active magnetic bearings (AMBs). The rotor assembly consists of the permanent magnet section with the turbine wheel mounted directly to the rotor hub. The rotor is levitated by the magnetic bearing system creating a frictionless interface between dynamic and static components. The FIT is designed to have the process gas flow through the system, which cools the generator section and eliminates the need for auxiliary cooling equipment. The power electronics for FIT combines Variable Speed Drive (VSD) and Magnetic Bearing Controller (MBC) into one cabinet. The VSD allows for a consistent and clean delivery of generated power from the FIT to the grid.
Components
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High-speed Permanent Magnet Generator
The permanent magnet synchronous generator is utilized in a high-speed, direct-drive turboexpander for power generation. The permanent magnet (PM) generator in the FreeSpin™ In-line Turboexpander is directly coupled to the turbine shaft and converts the rotational mechanical energy from the turbine into useable electricity via the variable speed drive. The direct-drive, permanent-magnet generator has variable speed and load capabilities and can run at speeds up to 30,000 rpm. The patented technology also offers high-speed operation, simplified controls for power generation and no maintenance.
The PM generator consist of two basic parts. A stator coil powered by an alternating current to create an electric field and a rotor made of special magnetic material that rotates within that field. The high-speed PM generators utilize the latest technology in high-strength rare-earth magnetic materials to achieve high efficiency and a high-power density. In comparison to other generator types, the PM generator has higher efficiency therefore improving the overall system efficiency and has higher power density allowing for a compact size at all power levels.
FIT Drives
The FIT units allow for consistent and clean delivery of generated power from the FIT to the grid. The output of the expander/generator is connected to the Power Electronics (PE) unit, which can be programmed to specific power requirements. The power electronics package uses an insulated-gate bipolar transistor (IGBT) rectifier to convert the variable frequency, high voltage output from the expander/generator to DC. The inverter then converts the DC to 380 VAC/480 VAC at 50 to 60 Hz for delivery to the power grid. The PE module matches its output to the power grid by sampling the grid voltage and frequency, and then changing the output voltage and frequency of the inverter system to match. Depending on the application, the FIT offers two types of drives:
FIT 300
| Machine Voltage | 0-480 VAC |
| Machine Current | 205 A (CONT) |
| Machine Phases | 3 |
| Machine Frequency | 0-833 Hz |
| Enclosure Type | NEMA 4X |
| Grid Voltage | 380-480 VAC |
| Grid Current | 190 A (CONT) |
| Grid Phases | 3 |
| Grid Frequency | 50-60hz |
| Coolant Requirement | Water 50LPM (13 GPM) @ 40°C (104°F) Max, 689 KPA (100 PSI) Max |
| Dimensions | 2130 mm H x 1380 mm W x 1000 mm D |
FIT 500
| Machine Voltage | 0-480 VAC |
| Machine Current | 450 A (CONT) |
| Machine Phases | 3 |
| Machine Frequency | 0-833 Hz |
| Enclosure Type | NEMA 4X |
| Grid Voltage | 380-480 VAC |
| Grid Current | 430 A (CONT) |
| Grid Phases | 3 |
| Grid Frequency | 50-60hz |
| Coolant Requirement | Water 50LPM (13 GPM) @ 40°C (104°F) Max, 689 KPA (100 PSI) Max |
| Dimensions | 2130 mm H x 1380 mm W x 1000 mm D |
How Machine Works
The FIT produces useable electricity by extracting energy from gas pressure let down processes. A reduction of enthalpy in the gas stream is the basis of this energy conversion. The factors effecting the change in enthalpy include pressure, temperature and flow from the inlet to the exit of the FIT. High pressure gas flows into the FIT and expands through the radial turbine wheel. The expansion energy is converted to rotational energy, which drives the shaft coupled to the permanent magnet generator. All rotating components are levitated by the active magnetic bearing system, providing frictionless or “free spinning” operation. The generator produces electricity and transmits it to the VSD, where the electricity is converted from DC to AC, and the frequency and voltage are regulated to match the local grid. After expansion, the gas exits the FIT along the same axial path for downstream processes.
Advantages
Sapphire’s FreeSpin™ In-line Turboexpander is more reliable and efficient compared to competitive products under similar working conditions. The unique advantages of the FreeSpin™ system include the following:
Proven Fuel-free Power Generation
Hermetically Sealed Module
High-speed Permanent Magnet Generator
Reliable Active Magnetic Bearings
Offset Carbon Emissions
Proven Fuel-free Power Generation
The FreeSpin™ In-line Turboexpander uses zero fuel and produces zero emissions. The simplicity of the FIT design enables a cost-effective solution for power generation. The average payback on a system is approximately one to two years, depending on the wholesale price of electricity. Calnetix’s turboexpander technology, utilized in industrial waste heat recovery systems, has accumulated millions of operating hours through its over 400 fielded units.
Hermetically Sealed Module
The FreeSpin™ In-line Turboexpander runs on magnetic bearings and is hermetically sealed into a single unit, eliminating the need for a gearbox and a lubrication system. It does not require dynamic seals, which often cause environmental hazards upon failure.
High-speed Permanent Magnet Generator
The high-speed permanent magnet motor generator used in FreeSpin™ In-line Turboexpander is simply constructed and operates with very little losses, which translates into low cost of ownership. FIT’s highly efficient motor generator has variable speed and load capabilities and provides a greater power density and a smaller footprint than conventional systems. The FIT produces power up to 280 kW at a continuous speed of 30,000 rpm and provides a system efficiency above 95 percent. Higher power models are available as well.
Reliable Active Magnetic Bearings
Active magnetic bearings offer significant advantages over conventional bearings in terms of footprint, operating efficiency, losses, remote monitoring capabilities, power consumption and reliable performance in harsh environments. While maintaining a similar cost structure to conventional oil lubricated bearing systems, the active magnetic bearings in the FreeSpin™ systems eliminate physical contact between rotating and stationary components, as well as eliminate lubrication, lubrication systems and seals, which provide users with the following benefits:
- Higher reliability
- Lower maintenance
- Longer lifespan
Offset Carbon Emissions
As global energy demand continues to increase, it is imperative for industrial and distribution processes to be as efficient as possible. FreeSpin™ systems help in recovering lost energy from natural gas and hydrogen applications, which in turn reduces CO2 emissions, increases overall plant efficiency, offsets electrical costs and generates additional revenue.
Technical Papers
- Design and Prototype Test Data for a 300kW AMB-supported Turbine Generator for Natural Gas Pressure Letdown
- Magnetic Bearing Actuator Design for a Gas Expander/Generator
- Test Results and Analytical Predictions for Rotor Drop Testing of An Active Magnetic Bearing Expander/Generator
- Development of a 125 kW AMB Expander/Generator for Waste Heat Recovery
- Design and Shop Testing of a 165 kW Cryogenic Expander/Generator on Magnetic Bearings
