The existing district-heating network at Trondheim has been extended by 12 km of pipelines and a waste incineration plant within the CONCERTO program. This increases the annual heat production by about 200 GWh, which equals to the heat demand of about 15,000 homes. Two absorption chillers have been installed at St. Olav Hospital, generating cooling energy from the above mentioned district heat. An “energy conversion plant”, which is fed by thermal energy of 6 MW, provides 3 MW of absorption cooling power.
In the field of buildings the Eco-City initiative at Trondheim deals with the construction of 350 new dwellings, having a total floor area of 22,400 m². Additionally 24 old dwellings (900 m²) are being eco-refurbished. In the public sector three schools (altogether 17,600 m²) will be refurbished and two new schools will be built. The new built “Nardo” school e.g. is equipped with a heat recovery ventilation system of 80 to 85% efficiency. The new built “Ranheim” school (Picture 1) has a gross floor area of 6,800 m² and is supplied by two sea-water-driven heat pumps of 150 kW each.
One commercial and cultural building of 3,000 m² is retrofitted and a part of a new hospital (94,000 m² out of 200,000 m² total size) is supported within CONCERTO.
Within the demonstration objects 300 kW of heat pumps and 1,000 kW of biogas boilers are supposed to be implemented in total. Map 1 shows a good overview of the demonstration activities.
Ranheim“ School
The “Ranheim Skole”, opened in fall 2010, (Picture 3) is a new public building at Trondheim with two storeys and a total gross floor area of 6,800 m². It provides space for 650 students. There is the actual school building and a sports arena, each supplied by a 150 kW heat pump. Sea water is the heat resource for those heat pumps, which deliver thermal energy for heating and domestic hot water preparation (Picture 4).
The building envelope reaches very good insulation values (Table 1) and a mechanical ventilation system with VAV (variable air volume) in the classrooms and other areas with intermittent operation provides the needed air for a good indoor air quality. A heat recovery system with 80% efficiency reduces ventilation heat losses. By these measures a calculated energy demand for heating of 43.4 kWh/m²a could be achieved.
Energy meters for the heat pump, electricity main supply and for the heating have been installed and already provide results (Figure 1).

Figure 1 - Energy consumption of Ranheim school in 2012/2013

Table 1- Insulation quality of building envelope
Absorbtion cooling at St. Olav Hospital
The first part of the absorption refrigeration system at the new St. Olav's Hospital was commissioned in 2004. The purpose of the installation was to reduce the use of the electrically driven compression chillers. The utilisation of the absorption refrigeration system increased with rising number of connected buildings, and in 2007 the total cooling demand was 6.6 GWh. Free cooling plus absorption cooling covered 97% of this need and compressor refrigeration chillers provided peak load energy accounted for 3%. In 2009, the hospital's construction phase 2 was completed, and cooling demand increased to 10 GWh/year.
The absorption chiller machine was by then too small, so that 10% of the cooling load had to be covered by electrically driven compressor chillers. In winter 2009/2010 Statkraft Varme decided to build another absorption chiller, driven by waste heat via district-heating. It was decided to install a new 3 MW absorption chiller (Picture 4), similar to the one installed in 2004, to reduce the use of electrically driven chillers again and for achieving the most environment-friendly refrigerant production at St. Olav's Hospital.
The energy production was monitored during the last years, so that the impact of the new chillers can be clearly seen. (Diagram 2).

Diagram 2 - Overview of total produced energy 2007, 2009 and 2012
Biogas Boiler at „Ladehammeren“ sewage plant
A biogas boiler of 1 MW power has been installed at the sewage treatment plant. It is owned by Statkraft Varme AS and had a total investment of 712,500 Euro. It feeds surplus energy from the treatment plant into the district-heating when available. The intention of the project was to exploit waste heat source (excess of biogas) and thereby replacing oil and natural gas peak load by district heat. The Ladehammeren purification plant (LARA) has an average biogas production of 2,750 m³ a day. This corresponds to approximately 6.5 GWh per year. LARA uses approximately 3.1 GWh itself, while 3.4 GWh of gas were flared each year. Picture 5 shows the boiler and the burner. Picture 6 shows the technical room with the heat exchanger for district heating.

Diagram 3 - Energy delivered from biogas boiler into district-heating from 2010 until 2012