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Research sparks new power savings in the University Library

University of Bath researchers have discovered a way of saving electrical power by running their library's computers on a direct current.

Students in the library using computers
University students use computers in the library, connected to a local direct current (DC) network.

Using a single central converter

In most UK homes the electricity is delivered as alternating current (AC), but computers, consumer electronics and some types of lighting require energy in direct current (DC) form.

Each device has an inverter inside it, which converts AC into low-voltage DC, but this isn't a very efficient way of using energy. When you convert from AC to DC there’s a small electrical loss in the form of heat.

In partnership with RWE npower and Western Power Distribution, a team of our researchers explored how using a single, central converter could make energy and cost savings.

Simpler design, greater security

Our researchers converted one of the University’s library computer laboratories to a DC rather than AC supply.

During a six-month trial, 50 modified computers and monitors were installed and powered from a specially created DC network relying on a central localised converter.

The team tested the feasibility and potential benefits of the DC approach, to evaluate the potential for operating an equivalent localised DC network on a light industrial scale.

Further work, funded by RWE npower and Western Power Distribution, added battery storage management and LED lighting to the DC network.

The new DC network offers greater security as DC power supply units have a simpler design, with fewer parts that could fail and need replacing. The system at the University can run independently from the grid for up to eight hours if there is a power cut.

Energy consumption halved

The project found that the DC network and associated computers used about half as much electrical power as the AC-powered computers they replaced - which could lower the University's energy costs by £25,000 a year.

The ‘smart’ management of AC mains supply is now being explored, by extending the original installation to include DC-powered LED lighting and battery management.

The user experience, potential cost and power savings, and enhanced security of supply will be explored further as part of a new project in collaboration with Western Power Distribution, Knowle West Media Centre, Siemens and Bristol City Council.

The team has subsequently written network charging methodologies for several generating companies. A study by electricity watchdog Ofgem said their ideas could save £200m in long-term development costs.

Advantages of DC over AC

  • By storing DC power in batteries, a back-up supply is made available to supply devices with power during peak charging times or when main power fails
  • These batteries can be charged using low-cost electricity, or powered by renewable energy devices such as wind turbines and solar panels
  • This level of energy security would be essential for someone relying on medical equipment, security systems or even lighting, and is much simpler than using a generator
‘This project has given RWE nPower and the University of Bath an excellent framework for exchanging knowledge that we have developed, either independently or jointly. This framework enables us to develop those ideas together, in confidence.’
— Jacob Allinson, Electrical Engineer, RWE npower

Researchers talk about our local DC network

Our researchers have discovered a way of saving electrical power by running their library's computers on a Direct Current.