19-02-2013, 09:34 AM
Power Quality Utilization Guide Hospitals
Introduction to energy consumption in hospitals
This application guide describes the use of energy and the potential energy
savings in the hospital sector, on the basis of theory and practical case studies.
Hospitals represent some 6% of total energy consumption in the utility buildings
sector. Utility buildings are offices, shops, hotels, restaurants, educational
establishments and care institutions.
In order to analyse the energy consumption of a hospital in greater detail it is
necessary to identify the larger energy consumers within the hospital.
Flows of energy within a hospital
The great majority of the energy used within a hospital is purchased from outside
in the form of natural gas and electricity. A small proportion is bought in as diesel
oil. The energy bought in is converted by a number of conversion systems into
the most important internal flows of energy, namely heat, cold, electricity and
compressed air. These energy flows are used for among others the following
applications:
Heat is used in the form of steam and in the form of hot water. Steam is used for
among others the kitchens, humidification in HVAC and sterilisation. In addition
steam is used to transport heat over longer distances. Hot water is used in the
form of central heating and tap water. In many cases heat is transported from the
heat generating station in the form of steam and then converted locally into
central heating or hot tap water. Gas-fired boilers or cogeneration systems
generate the heat.
Electricity is used for a wide variety of purposes. The largest electricity
consumers in a hospital are lighting, cooling machines, air compressors,
circulation pumps, HVAC fans, medical equipment and office equipment.
Compressed air can be divided into two main categories, namely medical and
technical air. Medical compressed air refers to direct treatment and care of
patients. Examples include breathing apparatus and surgical tools driven by
compressed air. Medical compressed air is subject to very high standards for
availability and quality. Other compressed air that is not directly related to
patients falls under the heading of technical compressed air. Examples include
HVAC control systems, workshop applications or keeping containers under
pressure.
Benchmarking on the basis of energy consumption
The healthcare sector is one in which a lot of information is generally available
concerning energy consumption. This offers many opportunities for energy
benchmarking, i.e. comparing the energy consumption of different hospitals. The
parameter used for comparison in benchmarking is very important. The two
techniques most commonly used for benchmarking are the energy consumption
per square meter or per bed. With regard to these techniques it is important to
bear in mind that they are based on technical characteristics of the building. If
sufficient data are available then it is desirable to compare hospitals on the basis
of energy consumption both per bed and per square meter. One difficulty that
stands in the way of benchmarking is the degree of outsourcing in the hospital:
some hospitals contract out e.g. their catering or laundry activities, which off
course leads to a lower energy consumption by the hospital itself.
HVAC
For climate control of the various buildings and applications in a hospital there
are usually various air conditioning units available, spread over the different parts
of the building.
Depending on the application the air may be heated, cooled, humidified and/or
filtered. Cooling, heating and humidification are generally done by a central
generating station of heat and cold.
Some typical hospital applications and their particular characteristics include:
• Polyclinic and consultancy: used only during “office hours,” with HVAC to
suit the comfort of people in these areas.
• Nursing wards: continuously occupied, with HVAC to suit the comfort of the
people there.
• Laboratories, dialysis departments etc.: HVAC to control the conditions for
the medicines and the tests carried out there.
• Operating theatres and emergency ward: continuously occupied, with
HVAC to control the conditions within narrow limits of temperature and
humidity. Ventilation and filtering systems are also used to prevent
contamination.
• Administrative departments: used only during “office hours,” with HVAC to
suit the comfort of people in these areas.