SUSTAINABLE HEALTH CARE ENVIRONMENTS DESIGNING ENERGY EFFICIENT AND HEALTHY INDOOR CLIMATE

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1 SUSTAINABLE HEALTH CARE ENVIRONMENTS DESIGNING ENERGY EFFICIENT AND HEALTHY INDOOR CLIMATE J Fredrik Karlsson Sweco Systems AB Vattengränden 14, SE Norrköping, Sweden fredrik.e.karlsson@sweco.se ABSTRACT Health care buildings, e.g. hospitals, are buildings that are built to stand for several years. They could therefore serve as good examples of sustainable architecture, and low-energy demand. In Sweden there are, at present state, several construction projects regarding new hospitals. In this paper two of the largest projects are described, both of them with ambiguous goal for sustainable buildings. The first projects is situated in Stockholm and will be the largest hospital in the Nordic countries with an area of about m 2. The other project is a m 2 expansion of an existing university hospital. Both projects focus on decreasing the demand for energy but as they have different prerequisites in respect of surrounding energy systems, previous policy decisions by the organizations and different design, the final solutions are different. 1. INTRODUCTION Health care environments are essential for a sustainable development of society, especially from a social point of view. Health care buildings, e.g. hospitals, are buildings that are built to stand for several years. They could therefore serve as good examples of sustainable architecture, and low-energy demand. Due to increased need for health care and the fact that the main part of Swedish hospital buildings were built in the 60 s and the 70 s and need to be refurbished there are several construction projects regarding new hospital buildings in Sweden. Most of them endeavor for high energy efficient standard. In this paper two new construction projects in Sweden are described as examples of health care buildings that will stand as examples of energy efficient buildings. 2. SUSTAINABLE HEALTH CARE ENVIRONMENTS Sustainable health care environments includes healthy indoor climate. Design of health care buildings is connected to regulations and standards but also, as in every project, there is a need for an integrated design between different professions. The scope of the energy profession is wide and connected to most other professions, such as architectural, construction, and heating, ventilation and air conditioning (HVAC)- design. Energy efficient measures will in most cases improve indoor climate. Especially measures of thermal insulation, heat recovery in ventilation systems, accurate control system and energy efficient lighting. Improved thermal insulation will decrease demand for heating power and improve indoor temperatures mainly during wintertime. In cold climates low ventilation rates or efficient heat recovery are essential to not exceed energy targets but still provide for fresh air supply. Accurate control system will improve temperature control in rooms, which will lead to temperatures that are closer to peoples comfort temperature. Energy efficient lighting system will 1

2 decrease surplus heat that will cause over-heating problems during summertime. 2.1 Energy demand in hospital buildings According to a survey study of energy demand in Swedish health care buildings (1) these buildings use about 2.8 TWh of heat, 63 GWh of district cooling and 1.7 TWh of electricity in Thus, the health care sector stands for about 3 % of the total energy demand for buildings in Sweden. storage. When these systems are not enough to cover the heating and cooling demand the energy is purchased from a district heating network and a district cooling network respectively. Fig.1 shows the energy system of Nya Karolinska Solna. In addition, the bore holes gives the opportunity to recover cold from the wintertime to summertime and heat from summertime to wintertime and thus decrease the demand for bought cooling as well as bought heat. A survey of energy demand for hospitals in several OECD countries, made in the mid 90 s, shows the energy demand per square meter and beds, respectively (2). The study shows that there is a great difference if floor area or amount of beds are used as unit. In Sweden floor area is usually larger than in other countries. A comparison between a hospital in the UK and Sweden shows that the specific energy for space heating is similar, but if space heating is divided by patients the Swedish hospital uses almost eight times more energy. The two buildings are similar regarding thermal insulation. 3. PROJECT DESCRIPTIONS 3.1 New Karolinska Solna, Stockholm The New Karolinska Solna (NKS) project is a new Swedish national hospital of about m 2. The building is using a double-glace façade to improve thermal insulation but still have the opportunity to use lot of glazing. The relation between façade area and building volume is 0.6, which gives a low need for thermal energy despite of a common insulated building fabric and a glazing structure. The heat recovery is based on water-coupled heat recovery with a thermal efficiency of 73 %. This kind of recovery system is secure for not distribute any air-borne disease. The building will use a very efficient high temperature cooling system and a low temperature heating system. Comfort cooling is produced by preheating of ventilation air up to outdoor temperature of 13 C. The energy production is mainly based on three geothermal heat pumps which utilize the simultaneously heat and cold demand in the hospital as well as the stored heat and cold in a bore hole Fig. 1: Energy supply for Nya Karolinska Solna. Dark grey arrow is heating, light grey arrow cooling and black arrow is electricity. 3.2 University hospital of Linköping The expansion of the University hospital in Linköping is a project with ambitious environmental goals. The building is of about m 2. This project has a goal of total annual energy demand (including operational energy) below 100 kwh/m 2. The building fabric is well insulated with U-values for walls about 0.12 W/m 2, K. Ventilation heat recovery is using recovery wheel, which gives a heat recovery rate of about 83 %. This kind of system is not that secure as the water-coupled heat recovery used in Nya Karolinska Solna, but the risk is considered very low. In addition, this building also has a good area-volume ratio, about 0.6. It also utilize façade and roof mounted PV panels (about 1000 m 2 ) and a bore hole system with 45 holes to store free-cooling from winter time to summer time. The cooling energy is from preheating of supply air during wintertime. District heating and cooling is supplied from a district heating network with a combined heat and power (CHP) plant. Cooling is produced by absorption chillers heated by district heating. Fig. 2 shows the energy system of University Hospital of Linköping. 2

3 comfort cooling system during summertime. By using a heat pump the temperature amplitude in the storage is larger and the storage can be used for higher temperatures during summertime Fig. 2: Energy supply at University hospital in Linköping. Dark grey arrow is heating, light grey arrow cooling and black arrow is electricity. 3.3 Comparision The two projects presented above represent two different views on energy systems. For the Nya Karolinska Solna project it was important to be independent of the district heating network company but still keep the amount of bought energy low. The strategy was then to invest in an efficient energy central that transform electricity into heating and cooling through the heat pumps combined with the bore holes. In Linköping there are good relations between the district heating network company and the Country Council in Östergötland. Thus, district heating and district cooling should be the first choice, as district heating is produced in a CHP-plant with high efficiency. More focus was then put on lowering demand by means of well insulated construction and efficient heat recovery High recovery rate in water based heat recovery The high recovery rate in New Karolinska Solna is obtained by large air handling units with air velocities close to 1 m/s to improve the heat transfer from heat and cooling coils to ventilation air. This can be compared to ordinary velocities of 3 m/s Bore hole storage In both projects a bore hole storage is used to store energy from winter to summertime and vice versa. In the Solna project a heat pump is used to produce heat during wintertime while cold is stored in the storage. In the other project no heat pump is used. Instead this storage is used to pre-heat ventilation air during wintertime and stored cooling energy is used in the Predicted values Nya Karolinska Solna is a hospital with more advanced health care including more operational theaters, radiology department and other departments with high demand for ventilation, cooling and heating. In the table below the two projects are compared for some energy related points of views. Predicted values are derived from building energy simulation models. TABLE 1: COMPARISION BETWEEN THE TWO PROJECTS. Parameter Stockholm Linköping Area m m 2 Average U-value 0,48 W/m 2, K 0,4 W/m 2, K Temperature 73 % 83 % efficiency heat recovery ventilations system Predicted energy 66 kwh/m 2 44 kwh/m 2 demand for heating including DHW Predicted energy 25 kwh/m 2 5 kwh/m 2 demand for cooling Predicted energy 30 kwh/m 2 11 kwh/m 2 demand for facility energy (fan motors, pumps etc) Predicted energy 55 kwh/m 2 54 kwh/m 2 demand for lighting and operational energy Predicted supply of 26 kwh/m 2 36 kwh/m 2 district heating Predicted supply of 8 kwh/m 2 1 kwh/m 2 district cooling Predicted supply of 97 kwh/m 2 65 kwh/m 2 electricity Predicted supply from renewables (Bore holes without heat pump, PV-panels) - 11 kwh/m 2 4. INDOOR CLIMATE IN HEALTH CARE BUILDINGS Indoor climate in health care buildings have been studied by (3), (4) and (5). In these studies an indoor temperature of about C has been preferred by 3

4 both patients and staff, despite the latter group are more active. All studies show that indoor climate is often rather dry. In cold climates many health care buildings does have low relative humidity levels during wintertime because of high ventilation rates and dry outdoor air combined with low moisture supply indoors. Indoor climate can be surveyed using measurements or by questionnaires that ask questions about sensation of indoor climate and symptoms that are related to the physics of indoor air. A symptom index (SI) can include symptoms such as fatigue, headache, eye disorders, cough, dry hands etc. Each symptom is described by the frequency of answers describing problems in percent, and the index is the arithmetic sum of each symptom. In total there are 12 symptoms included in the index (5). Other indicators can be used to visualize differences to national values or improvements over years. 4.2 Predicting indoor climate During the design phase it is not possible to ask the ward staff or the patients about their sensation of indoor temperature. The designer relies on calculations and simulations of indoor climate parameters. In most case indoor and operative temperature are calculated but also daylight, sound levels, and solar gain. All these parameters have been studied in both projects. The NKS project has bigger window area and thus the operative temperature (which includes the radiation temperature from the glazing) is a little bit lower. The two graphs below show results from climate simulations using IDA ICE Another index describing indoor climate is the working environment index (AMI from the Swedish word for working environment). This index is including 12 working environment problems that are summed up for calculating the index. 4.1 Describing indoor climate and energy performance In most studies either energy performance or indoor climate performance are taken into consideration. Some energy efficiency measures can have impact on indoor climate and other does only affect energy performance. As a tool to describe different kind of performance a graph with four indicators was used by (5). The graph (Fig. 3) shows symptoms index (SI), Amount of electricity use by square meters (El), working environment index (AMI) and CO 2 -emissions (CO2) from total energy demand. The dotted line in the figure below show Swedish average values and a hospital or ward can be compared to this average value. CO2 SI 1 0,8 0,6 0,4 0,2 0 AMI Fig. 3: Example of graphical representation of energy and indoor climate performance (5). El referensdata Fig. 4: Predicted air temperature and operative temperature during wintertime for the NKS project. Mean air temperature at 21 C, Fig. 5: Predicted air temperature and operative temperature during wintertime for the Linköping project. Mean air temperature at 22 C. As shown in Fig. 4 and 5 the difference between air temperature is almost 1 C in a ward room at Nya Karolinska Solna, but almost zero at University hospital in Linköping. Linköping does utilize a better insulated construction, which will improve thermal sensation of the occupants. 4

5 5. BUILDING MANAGEMENT Neither the less the building design is energy efficient it has to be managed in an efficient way. As hospital buildings are using a large amount of installations the building manager needs help to manage the building properly. In a health care building there are thousands of signals that can be connected to alarms, and used in the follow-up of energy demand. In most case only a small amount of signals are used in daily work. During the design phase this should be considered and in both projects there is collaboration between the design team and the building management company to achieve a design that is well-known and designed to fit daily work. One way to achieve this is to implement a system that indicates not only the present state of valves, temperatures etc but also indicates trends over time and if the trends show inappropriate functionality of the systems. 6. DISCUSSION The two examples of hospital projects, described above, show two different strategies to achieve energy efficiency. The New Karolinska Solna project has put effort in an efficient local energy production strategy with heat pumps that utilize the simultaneously heat and cooling demand in the main hospital building. The Linköping project has a well insulated fabric and efficient heat recovery in the ventilation system but utilize district heating and cooling as main energy sources. According to predictive calculations both projects will have similar indoor climate, which is appropriate to common temperature levels in health care areas. The project in Linköping may have fewer problems with operative temperature during wintertime due to better insulation and less glass area in the ward rooms. It is important to maintain an energy efficient hospital after the design phase. Both nursing staff and facility management staff are involved in the operation of the building and should thus have the possibility to maintain the system. Nevertheless, the user of a building could not change everything as for example the window area, the solar shading system etc are already decided and implemented. rate in ventilation systems and systems that utilize the simultaneously heat and cooling demand. In addition, well insulated building bodies will improve indoor climate in respect of thermal climate. Renewable energy, such as PV-panels and solar heating systems should be implemented in hospital projects with high energy standards. 7. ACKNOWLEDGMENTS The author would like to acknowledge Swedish Hospital Partner and Skanska AB for collaboration with Nya Karolinska Solna, and the Country Council in Östergötland for information about the University Hospital in Linköping. This paper has been prepared with economical support of Sweco System AB. 8. REFERENCES (1) SEA, Energianvändning i vårdlokaler (Energy demand in heath care buildings)- Förbättrad statistik för lokaler, STIL 2, ER 2008:09. Swedish Energy Agency, 2008, Eskilstuna. ISSN In Swedish (2) Jakélius, S. Learning from experiences with Energy Savings in Hospitals, CADDET Energy Efficiency Analysis Series No. 20, (3) Ekbom, J. User Perception of Climate in Hospital Wards An Analysis of Thermal Climate and Air Humidity Demands. Doctoral Thesis, Chalmers technical university, ISBN (4) Cehlin, M., Moshfegh, B, Karlsson, F. and Larsson, U. Analysis on Thermal Comfort for a Hospital Building by Multi-zone Modeling Summer Condition. World Renewable Energy Congress X and Exhibition, WREC, (5) Cehlin, M and Karlsson, F. Komfort- och inomhusmiljö-konsekvenser av strukturerad energieffektivisering för vårdlokaler (Consequences on comfort and indoor climate by energy efficiency measures), IEI-R--09/0056 SE, Linköping University, In Swedish The two projects described in this article shows that special effort should be spend on high heat recovery 5