A Working Lab

One of the world’s biggest DC installations

The office building A Working Lab is part of the Johanneberg Science Park at Chalmers in Gothenburg. It serves as an arena for innovation in the field of built environment and learning environments, and is a physical link between academia, business and society. The building has been awarded Gold certification by the Sweden Green Building Council and is currently the most intelligent building in Akademiska Hus’ property portfolio.

Within the framework of the FED project (Fossil-free Energy Districts), Akademiska Hus has tested new solutions that aim to create conditions for a totally fossil-free society. In brief, they make use of all the surplus energy through microgrids that transfer the energy between about 50 different buildings in the area, distributing it to where it is most needed.

The innovation projects include several interesting examples – such as a grid for direct current (DC) from solar cells with battery storage, as well as a property built with minimal climate impact and with no need for construction tents.

“A DC grid makes it possible to take maximum advantage of the solar-produced electricity from the roof, as power losses in the conversion process between direct current and alternating current basically disappear completely,” says Jonas Hansson, innovation leader for the project in the innovation arena A Working Lab. “We also want to take advantage of the solar cell around the clock, and do so through a battery store in which we save any surplus from the hours of sunshine during the day. These solutions provide more even energy consumption and enable peak shaving,” continues Jonas.

The project has faced a number of challenges, which collaborating actors Akademiska Hus, RISE, Ramböll and Afry have had to deal with. One of the challenges was to find suppliers who can provide A Working Lab with products that are compatible and can be operated directly with direct current from solar cells and battery storage.

A number of products were identified as possible direct current power consumers – including fan units, pumps, hot water heaters, control and regulation systems, access control systems, emergency lighting, general lighting, IT switches and vehicle charging.
Due to difficulties in matching the right voltage level, it was eventually possible to power fan units and general lighting by direct current. There are also examples of products that can be powered directly by direct current, such as mobile phones, computers, USB-powered computer accessories, desktop lamps, photocopiers and coffee machines.

The eventual solution was bidirectional inverter developed by the Swedish technology developer Ferroamp. EnergyHub is an inverter that can convert direct current to alternating current, and vice versa.

– This property built by Akademiska Hus is a good example of what we want to achieve with our system solutions. As the cost of distributing electricity increases, while the need to use more clean electricity for, among other things, the expansion of electromobility increases, so does the need for local solutions to manage power peaks

Björn Jernström, founder and CTO at Ferroamp

“We know that in some cases it’s not economically feasible to extend services, dig up roads and pay for expensive subscriptions and for electricity consumed. In such cases, solar panels on rooftops and DC grids, together with solutions for phase balancing and battery storage that we develop, are part of the solution. The loss of power will be minimal and the property owner will have both the power and the means to take financially and environmentally sustainable action. As far as we’re aware, this is the biggest commercial property in the world to have been built with direct current technology,” continues Björn Jernström.

The DC-powered electrical system faced additional challenges, such as finding luminaires and fan motors that can handle 760 Volts DC, which is the voltage that the EnergyHub system handles. A search was conducted for standard products that could utilise this voltage level directly, without conversion losses.

A standard fan for the ventilation unit that can handle 670 Volts was eventually found – but not one that could handle 760 Volts. In this context, an ESO unit (Energy Storage Optimiser) from Ferroamp came in handy. It is normally used for battery storage, and after some adjustments it was able to reduce the DC voltage to 670 Volts.

For the lighting in the building, the DC system’s centre of symmetrical balance could be used, i.e. where 760 Volts is divided into the two voltage components +380 Volts and -380 Volts, and where the market offers lighting fixtures for LED luminaires that can handle the voltage range 380-400 Volts DC. It was now possible for the entire building’s general lighting to be run on direct current.

There are now two parallel grids and distribution boxes in the building – partly for standard alternating current and partly for direct current. The DC grid has also been supplemented with a 300 kWh battery storage unit, supplied by Ferroamp, with its own ESO units, and which is adapted to the property’s EnergyHub system.

It is evident that A Working Lab in Johanneberg Science Park is ready to face the future, with the vision of becoming the leading long-term arena in which innovations are tested in a number of areas. The building has Gold certification from the Sweden Green Building Council, with energy consumption <35 kWh/sq.m./year excluding tenants’ energy consumption, thanks to high ambitions in terms of climate adaptation, resource efficiency and a low carbon footprint.