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HVAC SYSTEMS


Improved building


Lighting: 16.3% DHW: 2.3%


Air handling fans: 16.3% Exterior lighting: 0%


Heat rejection: 2% Pumps: 4.1%


Cooling: 8.8%


Humidification: 0.7% Heating: 0.9%


Services: 37.2% Equipment: 11.4%


to bring the domestic hot water to a temperature of 60˚C. The heat pump chiller could also be coupled to a geothermal heat exchanger. Figure 7 shows the distribution of the


used for domestic hot water heating. Heat pumps using CO2


total energy consumption (40,000,000 kWh equivalent) between the several services of the building after improvement of the energy efficiency. The building energy usage is now in the range of 533 kWh per m2


. This is good


compared to existing health care centers, but it is still high when compared to other buildings. The analysis of the distribution of energy


Figure 7: Energy consumption distribution (improved building).


would eventually be available at the condenser of the refrigeration equipment. With a low temperature heating system (at the temperature of the condenser) used for heating, a large part of the heating loads could be supplied by recovered heat from the air conditioning loads. Figure 5 shows the hourly cooling load of a building when the HVAC systems are in operation to maximise the recoverable cooling loads The total annual cooling requirement is 17,600,000 kWh. More than 75% of that heat will need to be rejected outdoors as no heating loads are present to match the available recovered heat (mostly in summer). But all available cooling loads in


winter are a potential source for recovery and free heating. Figure 6 shows the hourly transferred


heat from the hourly cooling loads of the building. The total amount of heat transferred is 3,600,000 kWh net, which is equivalent to offsetting 5,500,000 kWh equivalent of natural gas used for heating. The remaining heating requirement after


heat recovery on exhaust and heat recovery of inside thermal cooling loads will be much less than the initial requirement of 29,300,000 kWh. The heating requirement of the energy efficient building will be 450,000 kWh). Recycled inside heat gains could also be


shows that almost 50% of the energy usage is related to special thermal (37.2%) or electrical (11.4%) equipment specifically used in hospitals. The use of steam in hospitals should be minimised and the design of the distribution system should minimise the heat losses. It is always surprising to compile the monthly summer energy usage (125,000 m2 of natural gas) of a building of this size (75,000 m2


). The energy analyst should try to


understand where this amount of energy is used. The summer energy usage for thermal requirements could easily be reduced by a factor of three.


Summary This article aimed to show the major energy consumers of a hospital. More intensive studies of each remaining major energy usage should be done to reach a very efficient building. Because of their specific services and continuous operation, hospitals are far from becoming categorised as ‘Net Zero Energy Buildings’. This concept is still possible, but is not actually financially interesting in Canada.


refrigerant could be used





Providing insights into the vast field of healthcare engineering and facility management


IFHE DIGEST 2014 39


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