Energy

This is how DTU Nanolab saves electricity

The cleanroom uses plenty of electricity to keep the air particle-free, but consumption can be cut by 10 percent by, among other things, adjusting the level of ventilation.

DTU Nanolab's head of operations Leif Steen Johansen (right) and facility manager Jan Vasland Eriksen are working to cut 10 percent of energy consumption by optimizing the ventilation system in the cleanroom, where micro- and nanoelectronics are produced. — DTU Nanolab's Head of Operations Leif Steen Johansen (right) and Facility Manager Jan Vasland Eriksen are working to cut 10 percent of energy consumption by optimizing the ventilation system in the cleanroom, where micro- and nanoelectronics are produced.

Monday 28 November 2022

Nasrin Billie

The air in DTU Nanolab's cleanroom is replaced with clean air up to 200 times per hour using a comprehensive ventilation system.

Air purification is important, because structures down to 10 nanometres—such as photodiodes and chips with sensor function—are produced in the cleanroom. If the cleanroom air is not kept completely clean, this may damage the highly sensitive micro-electromechanical systems.

But now—in the period from 6 p.m. to 6 a.m.—DTU Nanolab will power down the motors running the ventilators to save electricity at a time of high energy prices. DTU Nanolab's total energy consumption is around four gigawatt hours a year.

"By reducing the speed of the ventilators and lowering the recirculation by 30 percent in the cleanroom, we can reduce our energy consumption by 68 percent between 6 p.m. and 6 a.m.," says Head of Operations Leif Steen Johansen.

Same level of safety

Together with Facility Manager Jan Vasland Eriksen, the operations manager ensures that the air quality complies with the ISO 14644 standard for a clean room by continuously measuring the concentration of particles.

“The cost is a potentially lower degree of purity. We don’t compromise on safety,” says Head of Operations Leif Steen Johansen about DTU Nanolab’s latest energy saving initiative.

The 40–50 users who work in the cleanroom on a daily basis are the biggest source of pollution. They include students, researchers, operational staff, and company employees who rent space in DTU Nanolab to use the facilities. They all submit particles such as hair, dandruff, and dust into the air, which may be deposited on the micro and nano devices and destroy their function.

Therefore, DTU Nanolab is reducing the cleaning measures during the evenings and on weekends, when there are fewest people in the cleanroom.

The majority of DTU Nanolab's 1350 square metres consists of pipes. "We have pipes that connect other pipes on several other lower levels. Every time you have bends on pipes that go from one level to another, you have a loss of pressure. That loss is primarily flow-driven. When we lower the flow—that is the air recirculation—the loss in the pipe system is reduced,” says Jan Vasland Eriksen.

Less pressure loss

DTU Nanolab is located at Ørsteds Plads on DTU Lyngby Campus. A building of 1350 m2 spreading across three floors above ground as well as a basement. What you cannot see from the outside is the ingenious system of ventilation ducts, pipes, cables, and technical installations that make up the entire first and second floors and ensure a constant recirculation of the air in the cleanroom.

When DTU Nanolab lowers air recirculation, it affects the pressure in the ventilation system. The loss of pressure inside the pipes is reduced, and the ventilation system will work less hard to clean the air and therefore consume less power.

In addition to lowering the air circulation, DTU Nanolab also plan to replace the filters that the air passes through before being blown into the cleanroom. They exchange the filters with some that offer lower pressure loss.

"We’ve already done this in parts of the cleanroom, but we would like to extend it to the rest of the cleanroom, which is a bit older,” says Leif Steen Johansen.

Biggest energy saving measures

Together, the two energy efficiency initiatives, lowering the air circulation and replacement of filters, will provide the biggest energy consumption savings at DTU Nanolab, according to the two technicians.

“Overall, with the measures we’re taking, we hope to be able to save up to 10 per cent of our total energy consumption, which is around four gigawatt hours a year,” explains Jan Vasland Eriksen.

At current electricity prices—for example DKK 4 per kWh—this equals savings of DKK 1.6 million.

In connection with a minor refurbishment and programming, the ventilation units have now been connected to Campus Services CTS system, which is a building control system. This enables Campus Service to control the main ventilators and Fan Filter Units (FFU) centrally. This also means that DTU Nanolab does not have to reduce the flow manually in the evenings and on weekends.

DTU Nanolab's other energy saving measures

Releases air humidity

Today, DTU Nanolab controls air humidity very strictly in the cleanroom, which entails that the air humidity must be within fx 45 percent relative air humidity because there are some special processes running that need to use the water that is in the air. This costs a lot of energy. Together with Campus Service, DTU Nanolab is currently examining whether it is possible to reduce moisture control in those places where there are no special processes.

Replaces 640 fluorescent tubes

DTU Nanolab is currently replacing 640 fluorescent tubes with LED fittings. This results in an energy consumption reduction of 50 percent in regard to the lamps. In addition, further savings are achieved by switching off the lights when the cleanroom is not in use. The next phase is to set up light sensors in the cleanroom that can switch off the light automatically. The lamps are controlled centrally. The users of the cleanroom cannot turn the lights on and off themselves.

Access control

To access the cleanroom, the users must pass their DTU card through the card reader, which registers who and how many are inside the cleanroom. DTU Nanolab will also use this information to register when the last person has left the cleanroom, so that air purity and lighting can be reduced as needed.

Vacuum pumps

Two out of the four gigawatt hours that DTU Nanolab consumes in one year are consumed by machines inside the cleanroom. The vacuum pumps account for the primary electricity consumption, and here it is also possible to reduce the speed and use a standby function, so that the pumps run slower and consume less nitrogen, when they are not running a process.

Topic

Security of supply and efficiency

Europe is in an energy crisis. Gas and electricity shortages have put the spotlight on how we can reduce our energy consumption and develop new technologies that can help to provide us with safe, effective energy supplies in future.

Contact

Leif Steen Johansen Head of Operations, Ph.D. DTU Nanolab - National Centre for Nano Fabrication and Characterization Phone: +45 45255713 Mobile: +45 25348992 lesjo@dtu.dk

Jan Vasland Eriksen Facility Manager DTU Nanolab - National Centre for Nano Fabrication and Characterization Mobile: +45 22157001 jver@dtu.dk