Living the good life
The struggles of a Malmö suburb to become the blueprint for the city of tomorrow prove just how difficult a task it is.
At first glance, Sweden's Western Harbour development in Malmö looks like any other modern urban quarter. Jauntily coloured blocks of flats rub shoulders along a blustery stretch of seafront, while standalone houses and more apartments huddle in their lee around paved seating areas.
The well-stocked wine racks, chic furniture and children's toys on view behind curtainless windows suggest that it is mostly young professionals and families who are choosing to set up home here.
In the centre, an elegant twisting high-rise, the Turning Torso, acts as a landmark for the new development.
A closer look, however, reveals some unusual features. One block has a vertical grill of glass tubes fixed to its wall, which looks like an avant-garde architectural decoration. This is, in fact, one of ten solar collectors harnessing power from the Sun.
A heat pump powered by wind and solar energy is extracting warmth from seawater and the aquifer atop which Malmö sits. And a solitary wind turbine is using the stiff breeze to generate electricity. Far from being run-of-the-mill, the Western Harbour is a unique city development deriving much of its renewable energy from the Sun, wind and water.
Back in the mid-1990s, it was a very different scene. The area was a wasteland that had become progressively deserted as shipbuilding industries had closed down. When the decision was taken to build a bridge across the Oresund Strait, connecting Malmö with Copenhagen in Denmark, the city authorities felt compelled to take action. They wanted to turn Malmö from an unattractive industrial zone with high unemployment into an area that would entice visitors to stay. The way to do so, they decided, was to build an eco-friendly city quarter to serve as a showcase for sustainable living and an icon for the new millennium.
The 600 apartments built for the first phase, Bo01 (Bo means 'to live'), were to represent a 'city of tomorrow'. The houses were to include multi-storey residences, terraces and villas and be a mix of rental and privately-owned properties. The developers had to fulfil strict 'green' criteria regarding the quality of the building materials used, type of transport provided, promotion of biodiversity and sources of energy. "From the outset, the aim was to generate 100 per cent of the development's energy from renewable sources," says Richard Bengtsson, E.ON Sweden's former project manager for Energy for the Western Harbour project.
As the owner of Malmö's district heating network, supplying 90 per cent of residents with their heat, E.ON was invited to come up with a plan for providing the Western Harbour with its green energy. District heating networks are common in Sweden; rather than individual houses each using a boiler to generate their own heat, a local cogeneration plant is used. Such plants often provide higher efficiencies and better pollution control than localised boilers. "Initially, the builders thought it would be difficult to provide renewable energy, but we felt that if, for example, we fed renewable energy into the existing district heating network it should be relatively straightforward," says Bengtsson.
One of the difficulties with trying to harness energy from the Sun or wind is that outputs are not constant throughout the year. The company had long thought that the porous, water-filled limestone bedrock on which Malmö sits might provide a means to store heat. The company decided to test its theory on the Western Harbour development. If successful, E.ON's boffins reasoned, aquifers could be used to store excess heat from any source until that heat is required in winter. And that would mean that less energy would need to be produced at the coldest time of year, saving money and carbon dioxide emissions.
"We dug ten wells, 90m deep," explains Bengtsson, "Half to provide access to a 'warm' side of the aquifer and half to a 'cold'. Today, as the seawater is warmed by the Sun in summer, we pump it down and save it in the 'warm' side. Then, when we need the heat, we pump it into the district heating system. When it cools, we pump it back down into the cold side of the aquifer. And when we need extra cooling in summer, we bring this cold water into the district cooling network. As the Sun shines in through people's balconies and windows, it's heated once more and then we pump it back to the warm side. It's a continual cycle."
The aquifer store and heat pump generate between 85 and 90 per cent of the heat used in Bo01. The other 10 or 15 per cent comes from the solar collectors. These are essentially glass-topped insulated boxes, each containing a blackened copper plate that absorbs heat from the Sun, and a pipe system in which water circulates. E.ON installed a total of 1,400m2 of collectors, of two types: vacuum and regular. Of these, the vacuum type was pricier, but more efficient, and gave better than expected yields.
"You can turn the vacuum collectors so they always have the right angle to the Sun," says Bengtsson. "We noticed that there was a particularly good yield in winter from the collectors that were set vertically. This is because of the very low angle of the Sun in winter at this latitude."
Solar power is also contributing electricity to the Western Harbour development. Some 120m2 of photovoltaic panels produce energy that is fed into the existing electricity grid. Their output equates to around 0.2 per cent of the overall amount of electricity. The vast majority of the electricity comes from a single 2MW wind turbine located on an industrial site a kilometre or so from Bo01. This was the first 2MW power plant to operate in Sweden. It supplies 6,000MWh of electricity annually, to 85,000m2 of housing. "It pretty much meets all the demand for residential lighting and electricity and also powers the aquifer/seawater heat pump," says Bengtsson.
Annual energy use
When the developers were planning the Bo01 development, the average annual energy use in Malmö was 150-170KWh per m2 for heat alone. So, the energy use target set for Bo01, of just 105KWh per m2 per year for both heat and electricity, was ambitious. Surveys conducted since the residents have moved in show that the lowest energy user is the 'LB-Hus', which, when inhabited by three people, consumed 87kWh per m2 in one year. This is in spite of having a dishwasher, stove, oven, fridge, freezer, washing machine and tumble-dryer. The internal temperature is maintained at around 21°C in winter and 25°C in summer.
The house is timber-framed with a concrete slab floor. It is ventilated by an exhaust air fan, with heat recovered via a heat pump. The heat pump warms water for the taps and radiators. The walls have 300mm of insulation, the roof has 500mm and there is an additional 350mm beneath the concrete slab.
The windows have a U-value of 1.0W/m2K. This is a measure of heat loss, and represents the amount of heat lost in Watts per m2 of glass when the temperature (K) is one degree lower outside. The lower the figure the better the insulation; current building regulations in England require a U-value for glazing of 1.8, almost double that achieved in the LB-Hus.
Across the Bo01 area as a whole, the average annual energy use is higher than the planned 105KWh per m2; it in fact ranges between 70 and 300KWh per m2 per year.
And, although the area was planned to derive 100 per cent of its energy from renewable sources, that has not been achieved every year.
However, because the Bo01 supply network is connected to Malmö city's regular electricity and heating networks this is not a problem. When more energy is used than produced, Bo01 can take some of the city's supply. Equally, if Bo01's production outstrips demand it is able to feed some back to the city.
The Bo01 area has managed to produce 100 per cent of its energy from the wind, Sun and water in some years, but in others it has used more than that supplied from its non-fossil sources. In 2004, for example, Bo01 produced 11.3GWh of energy but consumed 13.4GWh. While the cooling demand of 2.1GWh balanced the supply, the development consumed 4.7GWh for heat, against the supply of 3.5GWh. The electricity produced, 5.7GWh, roughly balanced that required for residential use, but an additional 1.4GWh was needed to run the heat pump.
Bengtsson puts the discrepancy down to the fact that E.ON's engineers put so much of their efforts into developing the required new technology that they overlooked the more conventional components.
"We worked so hard with all the new technologies, such as drilling the wells into the aquifer and connecting the solar collectors to the district heating network," he says. "But what we've had problems with is the heat pump, which is just a conventional component that you can buy.
"We have decided to buy another one to replace it and installation will begin in spring. Then we'll be able to produce 100 per cent of Bo01's energy from renewables next year."