University DC network could save money and energy

Researchers at Bath University are attempting to resurrect low-voltage direct-current power transmission in order to save money and energy.

The university is building a DC local network in part of its library to power specialised desktop computers, which use less energy than traditional machines powered by the alternating current that supplies houses and businesses.

The DC system prevents the power supply from being distorted, a common problem with AC computers that causes greater energy losses. Utility companies often fine organisations with many computers for causing large distortion problems.

Using DC will also allow the university to add batteries to the network, charging them at off-peak times when tariffs are lower and using the cheaper electricity during peak times.

‘The biggest opportunity to do this will be in the commercial sector, on sites where there is a lot of computing equipment,’ project co-leader Dr Miles Redfern from the university’s electronic and electrical engineering department told The Engineer.

‘We don’t see this going into the mass market where people want convenience and the 13A AC socket is too well established. But doing it in this concentrated way doesn’t demand a radical change of assets.’

While DC networks were the first form of commercial electricity distribution, AC quickly became the near-universal way of transmitting power because it tends to lose less energy as heat and the voltage can be easily stepped up or down with transformers.

DC is used to transmit power at high voltage over large distances and other local DC networks have existed in the past but almost all have now disappeared from the UK, according to Redfern, because of the historical dominance of AC.

The DC computers, supplied by Stafford-based Stone Group, have a better power-management system than typical AC computers, reducing peak power usage from around 350W to 35W and average usage by 50 per cent.

Traditional computers also tend to draw power intermittently, which distorts the AC power supply’s waveform and increases its frequency, causing more energy to be lost as heat.

‘The DC computers are less noisy, are better for the environment and smaller,’ said Redfern.

With the help of electricity firm RWE npower, the university has already begun installing the 50 computers and new wiring system, which will operate alongside the traditional network so that staff can continue using other appliance that run on AC.

Redfern and his colleague Professor Raj Aggarwal have received £80,000 from the university to install and run the network for six months to test its feasibility and potential energy, financial and environmental benefits.

Using DC could also make it easier to integrate solar-power generators and LED lighting, which produce and run on DC, respectively, into the network.

‘If it were rolled out across the university it could immediately save around £25,000 in efficiency,’ said Redfern. ‘It’s not earth-shattering science, it’s just re-engineering.’

Bath University library