WELLINGTON - Energy use by Beijing's subway system could be cut by up to 40 percent using ground-breaking technology employed by a New Zealand-China joint venture.

Wellington-based Victoria University said Tuesday that research developed by its Robinson Research Institute was part of the new multi-million-dollar joint venture deal with Milestone Science and Technology Ltd, based in Jiangsu province.

The joint venture would see the see the formation of three new companies to build new subway technology, as well portable compact magnetic resonance imaging (MRI) systems to improve medical services in remote areas of China, said a statement from the university.

Two of the companies would be based in the Jiangsu Zhongguancun Science and Technology Industrial Park as part of a superconductivity innovation center.

The third, alongside the Robinson institute near Wellington, would contract research and development from Robinson and other parts of Victoria University, and develop and manufacture HTS (high temperature superconducting) products that would be marketed by the China companies.

One of the China companies would develop the HTS flywheel, initially for Beijing's subway system, one of the city's biggest energy users, Robinson principal engineer Dr Rod Badcock said in the statement.

"The HTS flywheel is effectively an energy storage device. When trains slow down to stop at stations the flywheel will store the train's kinetic energy and can later supply it back to them to help with take-off," said Badcock.

"Currently, a great deal of energy is expended in braking and accelerating trains. With the HTS flywheel to capture and reuse this energy, the savings are estimated to be as high as 40 percent of the energy used by the Beijing subway system," he said.

"Energy storage not only represents the potential for energy saving in subway systems but also in supporting renewable energy generation. The same technology can be used to store energy generated by solar or wind, so in periods of low-energy production a store can be tapped into as needed."

The second China company would focus on the podMRI, a portable compact MRI system, which represented a significant advance for about 5,000 regional hospitals in China, Robinson director Professor Bob Buckley said in the statement.

"For many, there are barriers to moving from a low-field MRI, which is relatively low resolution but easy to install, to a high-performance high-field MRI, which can run to millions of dollars and require substantial support for installation and maintenance," he said.

"The advantage of the podMRI technology is it is low-cost, lightweight, easy to install and cost-effective to maintain, but with a substantial increase in resolution compared with existing low-cost systems."

Potential sales of the two technologies could run into tens of millions of dollars, Buckley said.

Milestone chairman Mi Wang said he saw substantial market opportunities in the podMRI.

Robinson was "one of the few places with the experience to design and build the high-speed HTS rotors needed for the subway flywheels my company is developing," Wang said.