News / 16.6.2015

District cooling captures significant amount of renewable solar heat

In the SunZEB research project, VTT Technical Research Centre of Finland studied the new opportunities offered by dense urban construction in the utilisation of renewable energy, recycling of energy flows and emissions reduction.

The year-long study confirmed that district cooling can be used for capturing a significant amount of heat from buildings and reusing it in the district heating network. A substantial amount of this heat is renewable energy from the sun.

According to the study, renewable energy collected by the building, large window surfaces, pleasant indoor air and energy efficiency can be combined in an economical way. On the other hand, a solar heat system as a separate solution turned out to be uneconomical, and finding the space for the system can also be problematic in an urban environment.

In terms of land use planning the study examined the new residential areas of Kalasatama and Jätkäsaari. In new inner city areas, the structure of blocks is urban and closed, however, affording more open aspects at least in one direction. This creates opportunities for the utilisation of passive solar energy, for example, with the use of windows. Passive solar energy has greater potential than solar heat collectors installed on the roof.

– The key result is the significance of overall planning in an urban system, says Jouni Kivirinne of Helen Ltd. – If you examine just a single building, the heat loads of the sun remain unutilised. More extensive, system-level studies showed that heat removed from indoor spaces by cooling can be utilised in other properties. In building design, the needs and possibilities of the entire area must be taken into account instead of those of individual properties.

The SunZEB concept provides a good opportunity for future energy solutions. Overheating and glare caused by the sun must be managed with building technology. Simulations in the research project used statistical weather data for 2030, taking account of annual rise in the average temperature due to climate change. On the basis of the simulations, the cooling need of office and residential buildings will grow and their heating need will be reduced.

– The building technology solutions used in the simulations represent current technology, but their use especially in residential construction is still limited. As expertise in new technologies grows and these technologies are more widely introduced, they will bring extra dimensions to architecture, construction and good indoor climate, says Jouni Kivirinne.

In terms of emissions, energy production must be examined as a whole while making sure that increasing use of renewable energy will not result, for example, more unfavourable CO2 environmental impacts than electricity generation in a combined heat and power plant.

The report is available in full on the VTT website at  

The partners in the SunZEB – PlusEnergy in the City project were:
Helen Ltd
Skaala Oy
Projectus Team Oy
Uponor Oy
Confederation of Finnish Construction Product Industries
Finnish Energy Industries
Turku Energia Oy
Tampereen kaukolämpö Oy
Hyvinkään lämpövoima Oy
Ministry of the Environment
Ministry of Employment and the Economy
FiGBC ry

The study was conducted by:
VTT Technical Research Centre of Finland
Aalto University
Architectural Office Kimmo Lylykangas