Powerhouse Brattørkaia: The World’s Northernmost Energy-Positive Building
July 7, 2021
As the world’s northernmost energy-positive building, Powerhouse Brattørkaia intends to set the benchmark for the construction of sustainable buildings: one that produces more renewable energy than it consumes throughout its lifespan, including construction, operation, demolition and embodied energy. It is the third in the Powerhouse series of energy-positive edifices conceived by a multidisciplinary collaboration of industry partners consisting of Norwegian architectural and design practice Snøhetta, property developer Entra, construction and development group Skanska, environmental organisation ZERO and engineering and architectural consultancy Asplan Viak.
The projects have provided the consortium insight into natural ventilation, optimised design for solar harvest and the reduction of carbon and energy consumption. Rune Grasdal, Senior Architect and Project Manager of Snøhetta, says, “Building energy-positive buildings is an extremely challenging task. No architectural practice, entrepreneur or developer could handle this individually. One of the key aspects of the Powerhouse alliance is that we are able to compose such strong teams with exceptional knowledge and experience of how we can build more sustainable buildings.”
Located in Trondheim, Norway, 63 degrees north of the equator, with greatly varying seasonal sunlight, the site of Powerhouse Brattørkaia was carefully selected for maximum exposure to the sun throughout the day and seasons, and is an example of how to collect and store solar energy under difficult conditions. The BREEAM Outstanding-certified, harbourside building featuring a black aluminium façade houses office spaces for diverse commercial tenants, including construction and shipping firms, a significant public programme, a café and a visitor centre on the ground floor open to the city inhabitants and school groups as an educational resource, which explains the Powerhouse energy concept and supports public knowledge as well as discourse on sustainable building strategies for the future.
“For the past 12 years, we have had a strong focus on environmentally-sustainable designs, particularly through our Powerhouse projects, which span schools, offices and retrofitting projects,” Grasdal remarks. “For over a decade, we have researched and experimented with energy-positive structures that are net carbon neutral over their life cycles. A key focus of ours has been to design buildings that pay back their CO2 footprint over their lifetime by returning clean energy to society, offsetting the fossil energy that otherwise exists in the energy grid. Our ‘form follows environment’ philosophy means that the design thinking of today should focus on environmental considerations and reducing our footprint first, and have the design follow this premise.”
Powerhouse Brattørkaia has three aims: to maximise the amount of clean energy produced by the building; to minimise the energy required to operate it; and to be a comfortable, enjoyable space for users.. Focused on occupant well-being, it balances fresh air and thermal comfort with extreme energy-efficiency. Air is released close to the floor at low speed, while extraction happens centrally by suppression in the stair shafts. The structural system is made of thermal mass exposed through strategic cut-outs in the ceiling, which absorbs and retains heat and cold to regulate the temperature without using electricity. Generating more than twice as much electricity as it consumes daily, it will supply renewable energy to itself, neighbouring buildings, electric buses, cars and boats through a local micro grid, acting as a small power plant in the city centre. Stored surplus energy in the summer months of almost total daylight is used in the dark winter months. Over its 60-year lifetime, the building is estimated to produce about 27 million kWh. Its slanted, pentagonal roof and upper façade are clad in 2,867 square metres of solar panels, which harvested 460,000 kWh in the first year. Calculated operational energy use for the first year is 478,288 kWh (equipment included), and 398,573 kWh/year from the second year onwards.
Excluding equipment, the average predicted demand throughout Powerhouse Brattørkaia’s lifespan is about 220,000 kWh/year, which is 80 per cent less energy to cover heating, cooling, ventilation and lighting needs compared to a typical new office building in Trondheim, while embodied energy corresponds to about 255,000 kWh/year. The proportion of embodied energy is therefore greater than operational energy, which is highly unusual. The reason is the extremely low energy demand to operate the building, thanks to optimised solar production and daylight utilisation, and minimised use of materials and embodied energy. For example, the hybrid concrete—boasting carbon values over 60 per cent lower than industry standards—was developed specifically for the project by Sverre Smeplass, Skanska’s in-house expert and concrete professor. “The key to success lies in integrated, holistic solutions,” explains Bjørn Jenssen, Chief Advisor at Skanska Technique. “Less is more is a well-known concept, but to achieve ‘more’ with ‘less’ requires interdisciplinary knowledge. For example, an important point of knowledge about technology is not to use more technical installations, but to use less and correct technical solutions to achieve an even better result.”
The reduced demand regarding both operational and embodied energy is what makes it possible to balance the entire demand through solar power. Various technologies greatly reduce daily energy use: insulating the building for maximum efficiency, intelligent solutions for air flow to decrease the need for heating, heat recovery solutions for ventilating air and greywater, seawater for heating and cooling and installing only energy-efficient electrical appliances. Daylight is optimised in the building design to reduce artificial light use. Large glass windows and a skewed aperture in the middle of the sloping roof allows daylight into every floor and reveals an atrium that acts as a public garden with horizontal glass windows on the sides like a skylight above the canteen below, while offering tenants wonderful city views.
Powerhouse Brattørkaia has been able to reach its energy goals for the first year of operation except for its lighting system. The building adopts the advanced ‘liquid light’ concept, where artificial light dims up and down according to user activity and movement, often referred to as ‘smart building technology’. Even though the LED lights are extremely efficient, the solution consumes a lot more energy than expected, as all the switches and occupancy sensors have a relatively high energy demand, even when the lights are off. “Consumption at night is almost half of daytime consumption, even with no lights on at night,” Jenssen admits. “We broke our own less is more rule with this system design. A simpler control system, using a little more light daytime, but with little energy waste to operate sensors and switches, and enabling full shutdown at night, would have performed much better. The same goes for plug loads, like AV systems, that show surprisingly high consumption on standby. High-tech solutions that seem fancy and futuristic are not necessarily ‘smart’.” Entra is in dialogue with several suppliers and producers to investigate different solutions that might reduce energy for lighting and incorporate better use of daylight.
Overall, there has been tremendous interest in Powerhouse Brattørkaia from Europe, Asia and the United States. “Hopefully the project will inspire others to take on projects like these outside of Norway,” Grasdal concludes. “We have proven that these structures can be built with existing technology, and we aim to scale up this strategy to the rest of our portfolio and ultimately the rest of the building industry.”
|Project Name||Powerhouse Brattørkaia|
|Site Area||Trondheim, Norway|
|Completion Date||August 2019|
|Site Area||18,400 square metres|
|Gross Floor Area||17,800 square metres|
|Building Height||39.3 metres|
|Mechanical & Electrical Engineers||Asplan Viak; Skanska; Sweco|
|Civil & Structural Engineers||Asplan Viak; Skanska|
|Images/Photos||Ivar Kvaal; Synlig|