Buildings account for about 40 % of national energy consumption, and hospitals represent about 6 % of the total energy consumption in public buildings in Norway. Hospitals are the building category with the highest specific energy consumption. A large university hospital uses twice as much energy per square meter compared to commercial buildings. Large university hospitals recently built in Norway have annual energy consumption between 300-400 kWh/m² (25-35 Btu/s.ft²).

Conversion and utilization of surplus heat sources represent well-known technologies and are under constant development. In large building complexes, with many thermal energy streams, there is a significant potential for coordinated production, storage, and distribution of energy.

Our study has developed new methods for the operation of interacting simulating models. These methods provide tools for optimization of combinations of different integrated energy systems. The main design issues we address are hydronic flow systems and the sizing of thermal storage systems. The hydronic layout is important with this respect to utilization of energy i.e. water temperature, but we also show the importance of control strategies on energy savings. A proposed new hydronic layout and control design is described in this paper, as applied to heating, cooling and storage systems in an arctic Scandinavian environment.

Heat recovery of surplus heat or cold energy streams in large hospitals come from internal loads like equipment, and lighting systems, They canby directly related to the occupancy and demand of the HVAC refrigeration or ventilation systems. The potential for energy synergies in these type of buildings is dependent on the available surplus heating/cooling source at a given time. For building types, such as hospitals, where the need for heating and cooling is high and not necessarily matching the surplus heating and cooling production, thermal storage is the most relevant technology to deliver the advantages of heat pumps and chillers. Research on thermal storage solutions for hospitals has mainly focused on the storage system and not considered the total energy system. We haveanalyzed different temperature levels for supply and return heating water system as a function of outdoor temperature, different temperature levels for cooling supply and return, and design parameters for a typical geothermal storage volume. System efficiency will be sub-optimal if interdependence of these subsystems is not considered.