The Co-operative Bank

Air-driven UPS lowers Co-op's carbon profile

A new data centre for the UK’s Co-operative Bank is the first to deploy a 'green' uninterruptable power supply (UPS) that uses compressed air to generate the initial replacement electricity.

The system, called Air-DRUPS, cuts in if mains power is lost, and uses a series of scroll generators driven by compressed air to provide an emergency supply until the back-up generator starts. The Air-DRUPS technology was developed by critical power supply solutions firm Socomec UPS working with back-up power equipment vendor Pnu Power and data centre design and build specialist DC Environmental Services.

“When power is required, [the energy in] the compressed air is immediately converted to electricity by driving it through a scroll expander, in turn driving a DC generator,” said Socomec UPS UK sales director Peter Chai-Tsai. “Ultra-capacitors support the DC bus for a short period until the scroll generators are up to speed; that takes less than 200ms. The compressed air system provides a minimum of 30 seconds of back-up time at full load (over a minute at 50 per cent load), sufficient to attempt to start a diesel generator more than once. The second start can also be an air start, providing a different type of technology, and therefore adding resilience to the system.”

Although the initial capital outlay is comparable to similar UPS systems (but higher than those using batteries), says Socomec UPS, the total lifetime cost of compressed air technology is lower, because compressed air batteries do not require component changes during the system life. They can also operate at higher temperatures, which can have an effect on data centre air-conditioning requirements. Moreover, compressed air batteries use ‘negligible’ power on standby, with a minimum 20-year service life, the company adds.

The Co-operative Bank is operated by the Co-operative Group, the UK’s largest mutual business, owned by almost six million consumers. The new facility is based in the bank’s Stockport Pyramid building in Greater Manchester. “The Co-operative is always looking at ways in which we can reduce our carbon footprint, and we wanted to find a greener UPS system that would make the lead acid batteries obsolete,” commented Co-operative Estates managing director Martyn Hulme.

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