Industry Focus Renewable Energy
Successful trials of new technology R
ecent tests carried out at a GE Power Conversion facility in Rugby has resulted in success- ful trials of Hydrogenie, a power generator incorporating ground breaking technologies that enable highly efficient production of electricity in a small space. Hydrogenie makes use of supercon- ductors instead of copper for the rotor windings on the motor, operat- ing at 43 Kelvin, or -230°C. It was tested late last year up to and beyond its full rated load - 1.7MW spinning at 214rpm - and met expectations and design predictions. Until recently, superconductivity could only be achieved at around 4K (-269°C). However, new ‘high tem- perature superconductors’ (HTS) exhibit the phenomenon at much higher temperatures. Such machines will need less complex insulation systems and less powerful cooling than used hitherto on devices such as medical MRI magnets.
“This technology is a true break- through,” commented Martin Ingles, Hydrogenie project manager at GE Power Conversion. “It could radi- cally improve the efficiency of equip- ment producing electricity from water and from wind, and may also be suitable for further applications down the road.”
Latest superconductors are made by depositing a superconducting layer of ceramic onto a relatively cheap base metal. They have virtually no resistance to electrical current when cooled to very low tempera- tures, so windings can be made with wires having a cross section around two percent of that of a conventional copper wire winding.
More windings can be fitted into electromagnet coils, resulting in a higher power magnet that is sub- stantially smaller or lighter than before. Superconductivity offers significant advantages in efficiency, and significant weight reductions compared with conventional machines. The greatest benefits in terms of size and mass reduction are for applications where high torque machines are typically used, most likely as a direct drive application in installations such as wind tur- bines, ship propulsion or run-of- river hydro plants.
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GE’s Power Conversion business has taken an important step in testing a viable way of producing large amounts of electricity from renewable resources using superconductors running at relatively high temperatures
reality. GE’s Power Conversion busi- ness did much of the development of the Hydrogenie 1.7MW 214rpm HTS generator as part of the EU Framework Programme 6 funded project that ran between 2006 and 2010.
Foundations for research The successful completion of the Hydrogenie project will set the frame- work for continued research and development in the study of super- conducting machines. One specific area that may potentially benefit in the future is the upgrading of older run-of-river power plants. Coupled with running the machine/turbine at variable speed the benefits could allow efficiency improvements of up to 12% at part load.
The technology building blocks developed as part of the project will also be used in other businesses where high torque and slow speed machines are in use. The most immediate areas of demand are in wind power generation and in marine propulsion.
Problems overcome
GE has conquered significant techni- cal challenges relating to the cryo- genic cooling and thermal insulation required to keep the superconductors at the required temperature. Extremely cold helium gas is piped through a rotating coupling into the machine rotor and then circulated around the individual coils. “It’s rather like trying to keep ice cubes frozen on a rotisserie in a very hot oven,” added Ingles. “Except that our rotisserie is rather high-tech.” The rotor is located inside a vacuum, but still has some direct contact, via its shaft, with the outside world. This cre- ates issues relating to the massive tem- perature differences along the shaft. The machine incorporates a patented method for transferring torque from cold HTS coils to the machine rotor. Low resistance thermal joints and assemblies ensure that low cooling power is required to cool the coils. In fact, the machine demon- strates all of the technologies required to make HTS machines a commercial
Above: GE’s superconductive technology research offers significant advantages in efficiency as well as size, mass and weight reductions compared with conventional machines
A superconducting wind turbine gen- erator may permit significant reductions of mass mounted on the tower, thus helping to reduce the cost for the tower itself and its foundations. Recent stud- ies conducted for GE Power Conversion show that the lifetime energy saving for a superconducting wind turbine com- pared to a conventional machine could be as much as 20% - for offshore or desert machines above 10MW. On ships, HTS technology com- bined with DC or variable AC systems can result in up to four percent fuel savings, while the reduced size of the motors will be attractive to naval architects leaving more space for pay- load or passengers.
Other partners in the EU Framework Programme 6 funded pro- ject, ‘Development and field testing of a compact HTS hydro power genera- tor with reduced investment costs, lowered environmental impacts and strongly improved performance to reduce the price per KWh’ were Zenergy Power, KEMA Nederland, Stirling Cryogenics & Refrigeration, Silesian University of Technology, Cobham CTS, and E.On Wasserkraft.
GE Power Conversion
www.gepowerconversion.com T: 0800 800 4857
Enter 211 NOVEMBER/DECEMBER 2013 Automation
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