Sweden’s Sahlgrenska University Hospital

Critical role for Trend BEMS in new hospital unit

 

The well-being of critically ill patients in a recently opened unit at Sweden’s Sahlgrenska University Hospital demands reliable and accurate control of environmental conditions within the new building. Energy saving, demand led control of the facility’s HVAC services is also necessary in order to meet consumption targets and minimise operating costs. Satisfying these different requirements is a Trend BEMS supplied and engineered by NEA Teknik AB (formerly Geamatic Styr AB), whose responsibilities also included designing the system’s control strategies and architecture.

 

Sahlgrenska University Hospital, Gothenburg, offers emergency and general care to the local region’s 700,000 inhabitants and provides specialist treatment for all of western Sweden, which has a population of 1.7 million. Opened in May of 2009, the new 312-bed care unit is part of an ongoing rebuilding and refurbishment programme at Sahlgrenska, which is one of Northern Europe’s largest hospitals.

 

The 7-storey unit houses inpatient wards and outpatient and daycare services. It was built at a cost of 500 million SEK (£45 million) – the largest investment by the hospital in 15 years - and has a floor area of 24,000m2.  Each department has open plan areas that create a welcoming and reassuring atmosphere, the wards being arranged around a central core, running up which are the lifts and stairs. Many of the patients are in a very vulnerable state. For example, some have just undergone transplant surgery, while others are suffering from serious infections or are recovering from strokes. The unit is also a centre for renal care and the treatment of blood diseases.

 

The building has no boilers or chillers, a district heating and cooling system supplying all hot and chilled water needs (via heat exchangers). Neither are there any radiators, the whole unit being served by underfloor heating and cooling. In areas with high cooling demands there are also chilled beam ceiling units. There are six main air handlers, which supply tempered air at 18oC all year round. The Trend BEMS controls and monitors all of this HVAC plant, plus the power plant-room cooling and numerous extract fans (in kitchens, pharmacies, etc). In addition, it switches the building’s lighting and monitors the medical gases. It also has a smoke management role should there be a fire.

 

On two floors of the unit there are patients who are particularly susceptible to infections. Here the air supply is purified using HEPA filters and the air change rate is extremely high. These wards have double door entries that act as airlocks and one of the Trend system’s roles is to keep these positively pressurized. There is also a general need for stable control of temperature, which is especially important in wards where the patients must be kept warm at all times.

 

Despite the building’s often high heating and cooling loads, the design of its HVAC services and the control actions of the BEMS are helping to prevent excessive energy consumption. For example, the AHUs have a sophisticated heat recovery arrangement that has proved capable or reclaiming 68% of the heat contained within the extract air. This equipment is controlled by the BEMS, which also varies the speed of the AHU fans in accordance with demand, thus making further energy savings. Moreover, the building is divided into numerous control zones, making it possible to prevent the supply of tempered air to areas that are not in use.

 

Each floor and corridor in the building has its own, independently controlled lighting profile, which dictates the illumination level (0 – 100%) provided at different times of the day according to the area’s needs. The light levels are set by a DALI lighting system. Energy efficient light bulbs are used throughout. Sahlgrenska’s aim is that the total energy used within the new unit for heating, cooling and lighting should not exceed 130kWh/m2.

 

In the event of a fire, the BEMS would close the appropriate zoning dampers in order to isolate the floor where the outbreak had occurred. The area’s AHU supply fan would be switched off and the extract kept running to evacuate the smoke. It would also bring on a large roof-mounted fan to clear any smoke from the stairwell and lift shafts.

 

The Trend BEMS comprises 23 Ethernet-linked IQ3 controllers, which together have a total of almost 1000 input and output points. There are four main control panels in the plant-rooms, plus a further 12 panels that are distributed around the building and house the IQs that do the lighting control and space temperature measurement. There is sufficient spare capacity within these panels to allow for system expansion. For example, there might be a need for more extensive temperature measurement or there could be changes within the building that necessitated the fitting of variable air volume terminal units, which the BEMS would have to control. Owing to the IQ3 controllers’ use of add-on input/output modules, any such requirements will be easy and economical to accommodate.

 

The Ethernet TCP/IP network to which all the IQs connect has been interfaced with a fibre-optic LAN that runs around the hospital. This supports a SCADA operator interface comprising two servers, one of which is used for centralised management and monitoring of the HVAC services by providing access to all BEMS monitored data and control settings. The other server covers various other systems, including the lighting, lifts, power supplies and utility metering. Authorised users can also gain full access to the BEMS by plugging a notebook PC into the Ethernet connector that is found on every panel. There are around 100 Trend IQ controllers installed in other buildings at Sahlgrenska and these too can be viewed and adjusted via the SCADA head end.

 

Unusually, NEA Teknik not only engineered the BEMS but also drew up the controls specification, a job that on a project of this scale would normally have been done by a consultant. And it developed the software driver that enabled the Trend BEMS to be interfaced to the fibre-optic network. Despite a demanding time schedule for installation and commissioning, the system was handed over on time and has fully satisfied the hospital’s expectations.

 

The main contractor on Sahlgrenska’s new care unit was PEAB, who engaged Johan Lidbeck to act as installations coordinator on the BEMS element of the project.

 

ENDS…