Energy usage and efficiency in hospitals, clinics and medical facilities



Medical facilities are by nature intensive energy users as they work on a 24-hour, seven-days-a-week basis. Energy is used for heating, sterilisation, lighting, air conditioning, cooking and other functions such as radiology, therapy, surgery, etc.  

Healthcare is regarded as the second highest energy-intensive building related industry. Many of the systems used are based on obsolete and wasteful techniques. Recent studies have shown that significant savings can be achieved by adopting more efficient systems.

A recent article suggests that the average hospital bed consumes as much energy as several residential buildings, if one takes the total energy consumption of the facility and divides it by the number of beds [1]. Medical care and hospitalisation are becoming more and more expensive, so any savings which reduces the cost of bed occupation is welcome. The energy use intensity (EUI) for hospitals ranks just behind the food service sector, and outpatient healthcare facilities use is somewhat lower. The EUI of hospitals and other inpatient healthcare facilities is nearly three times that of typical commercial buildings.

Energy consumption

As a means of comparison, energy consumption is measured is measured in kWh per bed or GJ per bed, and can be reported on either a daily (kWh/bed/day) or annually (GJ/bed/year). The typical consumption figures will vary with the type of facility, and this system is most useful for establishing benchmarks for improvement. Benchmarks vary between the type of care facility, the size of the facility, and so on. Sometimes the consumption per unit floor area is used, but this does not give an indication of the usage.

Energy usage in hospitals has been the subject of numerous studies. Table 1 lists some of the results for south African hospitals.

Table 1: Energy consumption per bed per day (various sources).
Study Total number of beds Total energy consumption/bed/day (kWh) Electrical energy consumption/bed/day (kWh)
Groote Schuur Hospital [1] 945 Data unavailable 92
Worcester Hospital [1] 269 Data unavailable 61
Laingsburg Hospital [1] 20 Data unavailable 43
Netcare SA (total) 10 000 83 61,6

It can be seen from Table 1 that energy consumption/bed varies with the type and size of hospital. The Western Cape provincial administration HC[1],  has set a target of 35 kWh/bed/day ( electrical) , which gives 1050 kWh/bed/month, more than many average households.

Energy usage analysis

Typical energy users are as follows

  • HVAC: Cooling, air compressors, circulation pumps, HVAC fans, medical equipment and office equipment
  • Heating: Steam is used for the kitchens, humidification in HVAC,  sterilisation and to generate hot water
  • Lighting: Wards, examination, rooms, operating theatres and other areas
  • General: Office equipment, ancillary building equipment and other machinery.

Fig.1 shows some estimates of where energy is used in a typical hospital. Air conditioning and ventilation comprises the biggest user of energy, followed by heating.

Energy monitoring and analysis

In order to be able to reduce energy consumption in a hospital, it must first be measured. In addition to this, the data provides information pertaining to costs and emissions. This, in turn, provides the foundation needed for making optimised decisions for long term energy reduction and profitability. Progressive technologies for energy savings have to be developed on an ongoing basis. The knowledge and the experience required to analyse a hospitals energy consumption in a meaningful manner is available and can result in the compilation of benchmarks, which can be used as the foundation for optimisation. Energy monitoring needs to be done over a long period, at least a full year covering all seasons.

Central heating system

The central heating system is used to provide both hot water for washing and space heating, and low grade steam for sterilisation, cooking etc. Most larger hospitals rely on a central boiler system to generate steam which is distributed to the various functional units. Boilers are the biggest single energy consumption item in many provincial and state owned hospitals. Older designed facilities used steam as a means to provide heat for space heating, sterilisation (autoclaves), cooking and other items. The centralised supply of heat proved to be the most efficient in the past and many south African government hospitals are fitted with coal boilers.

The requirement is for low quality (low temperature) steam and boilers used are of the coal grate feed type. Coal boilers are inefficient in operation and emit pollutants as well as carbon dioxide, and have a further problem with ash disposal. They are not used for incineration of medical waste as is commonly believed. One of the problems is delivery and payment for fuel. Coal is delivered in batches and must be stored on site, and payment is made for delivery. Variation in quality can give a control problems.

There are several approaches to improving the energy efficiency of the heat source in hospitals. Heat from the boiler flue gas is not recovered and exits into the atmosphere, a potential source of saving. Steam and hot water circulation systems also result in energy losses. While boiler improvement can be a source of energy savings, the heat distribution and utilization system can be upgraded with good results.

Efficiency improvements Boilers require regular maintenance throughout the year, and savings can be realised by an effective maintenance and inspection program, not only of the boiler but of the steam system as well. Modern boiler combustion monitoring and control systems are available which can optimise boiler operation.

Change to gas fired boilers

Changing from coal fired to gas fired boilers is a common approach today. There is a program underway to convert all of the coal fired boilers in Gauteng provincial hospitals to gas fired [2]. Gas energy prices are regulated by Nersa, and hospitals can also ensure better budgeting. The exhaust gas can also be connected to a heat recovery system that can be used to generate chilled water by absorption chilling. Seventy-seven old coal-fired boilers in 25 hospitals will be replaced with dual-fired diesel/natural gas boilers. In addition, the department says feasibility studies are also under way to establish a gas pipeline to support the boilers as well as tri-generation plants at the hospitals.

It is not always necessary to replace the boiler completely, as changing a coal fired boiler to gas fired can be can be accomplished easily. The majority of the important components can be retained, depending on the age and design of the boiler [4]. An increase of efficiency of 15 to 30% is possible, simply due to the fact that removing the grate and ash catcher leaves more space for the burner and flame, and there is not heat loss from hot ash leaving the boiler [5]. In addition, conversion to gas firing allows tighter controls over combustion and fuel and air supply, to allow the boiler to operate at the optimum point for different loads.

Fig. 1: Typical energy use spectrum [1].

CHP for hospitals (co-generation and tri-generation)

Hospitals that use boilers to provide steam and water heating could benefit from CHP systems using natural gas-to-power generators and the exhaust gas to provide heat. The CHP system can provide a portion of the hospitals electricity demand as well as steam and chilled water. Several hundred CHP systems are installed in hospitals worldwide using one of the following options:

Gas from internal combustion engines, coupled to a generator-exhaust gas, is passed through a heat recovery system which generates hot water, and can also provide chilled water. This option is suitable for installations with a lower electrical and heat load.

  •  Gas turbine generator: The outlet gas is fed to a heat recovery system where  it is used to produce steam , which in turn is used to produce hot water- this replaces the hospital boiler system, while generating electricity at the same time.
  • Biomass and hospital waste-fueled steam boiler driving a steam turbine coupled to a generator. Exit steam from the turbine passes through a heat recovery system, which generates low grade steam and hot water.

In addition to saving costs, the CHP plant acts as a standby electricity source in the case of grid failure. In the case of failure the CHP can act as a bridging supply while other standby plant starts up.

Lighting

Lighting consumes a large portion of the energy used in a hospital. Replacement of older lighting systems with more efficient CFl or LED lighting, as well as lighting control systems, can result in significant savings in energy as well as offering better control over lighting levels, with an improvement in patient comfort.

HVAC

Hospital buildings are one of the few types of building that run at full scale 24 hours a day. Unlike other buildings, HVAC in hospitals require not only comfort but also safety and hygiene. Hospitals need to maintain the temperature, air quality, air flow, and humidity to create the most comfortable environment possible for the patients. Ventilation in hospitals also work to control hazards, because there are frequently fumes, airborne pathogens and chemicals in the air that could cause harm if not properly dealt with. Different areas of a hospitals have different air conditioning systems, depending on the function. Different parts of a hospital have different needs an operating room

Depending on the climate, between 35 and 60% of the annual energy costs of the typical healthcare facility are related to the operation of the HVAC systems [3]. Increasing demand for comfort in rooms coupled with high internal loads has led to a significant increase in cooling requirements. [2] As a result, hospital heating and cooling systems which rely on conventional heating, ventilation and air-conditioning (HVAC) units are both energy intensive and expensive [2].

External loads

External loads are mainly due to solar building loading and reduction will require modification of the building such as window louvering, etc.

Internal loads on HVAC

The internal load on a hospital room has several sources.

  • Patients: The heat gain from healthy people varies from 70 W ( sleeping) to approx. 100 W ( awake. ) An ill patient may generate more due to fever or inflammation. The patient occupies the bed 24 h/day. In addition there are meals to consider which add heat. The patient heat load cannot be reduced. By comparison each patient generates as much heat as 8 to 10 CFL lighting units. If staff and visitors are considered then ward occupancy/m2 may be higher than office occupancy/m2. In a 600 bed hospital the patients will generate 60 kW of heat.
  • Lighting: Without lighting control systems, light are generally left switched on for a large portion of the day in wards and in some areas are on permanently. Older hospitals were designed for incandescent or fluorescent lights. A change to modern CFL or LED lighting reduces the heat load due to lighting considerably.
  • Medical apparatus and machinery: This consists of monitors and other devices. In an acute ward each bed would be monitored. The heat load from such devices cannot be avoided or reduced.

In addition to wards there are loads in operating theatres, offices and other common areas which must be taken into account. Wards occupy most of the floor area of a hospital and constitute the biggest HVAC load.

Fig. 2: Whole building design approach to renovations and expansions.

Contamination and infection control

In addition to comfort, the HVAC system has to ensure contamination and cross-infection control, which requires additional energy-consuming equipment as well as a much higher percentage of fresh air than conventional HVAC systems. The arrangements for HVAC will vary from ward to ward and treatment and procedures rooms, such as operating theatres. Many hospitals use once-through systems for general HVAC and this can consume a large amount of energy depending on the difference between outside air temperature and inside room temperature requirements..

Airborne transmission occurs when either airborne droplet nuclei or dust particles disseminate infectious agents. Droplet happens through nuclei or dust. Nuclei are smaller droplets of bacteria or viruses caused by the high velocity with which coughing and sneezing. In this case the control of ventilation and air handling is very important to prevent nosocomial airborne transmission of microorganisms. Sterilisation equipment is used with both recirculated air and fresh air intake and this adds to the energy load.

Room pressurisation

The significant airflow requirements and high air changes per hour that are necessary to maintain sterile and healthy environments are also the major contributor to the significant energy usage of healthcare facilities. As a result, the HVAC systems not only use higher fan energy to move the air from the air-handling system, but these also use significant energy to cool and dehumidify outdoor air to maintain space temperature and humidity requirements. It is important to build the spaces tight and avoid over pressurisation [3].

Displacement ventilation

Consider using a displacement ventilation system rather than traditional overhead ventilation. Such systems have the potential to improve both energy efficiency and infection control  . Based on a relatively new technology, displacement ventilation systems introduce cool air at low velocity, improving ventilation effectiveness within the occupant zone. As a room becomes warmer through use, the air, and its contaminants rise and are evacuated. Additional benefits of displacement ventilation include:

  • Saves energy by reducing ventilation air change per hour (ACH).
  • Decreases ducts, saving floor-to-floor height.
  • Reduces chiller lift and improves efficiency because supply air temperature is higher.
  • Recent findings (based on actual measurements) indicate that displacement ventilation with 4 ACH provides the same or better air quality for patient rooms than mixing ventilation at 6 ACH. [4]

Major renovations and expansions

When undertaking renovation or expansions of the HVAC system, hospitals benefit by using a whole building system design approach. Load reducing strategies such as lighting replacement and building alterations, will decrease the HVAC load, and should be considered before the HVAC (Fig. 2).

Optimising the HVAC system after load-reducing strategies have been implemented. This is because retrofitting facilities for energy efficiency, upgrading lighting and windows, for example, will affect heating and cooling requirements.  Reducing use of 100% outside air in non-medical spaces (i.e., offices and storage areas) can result in substantial savings on construction and operations costs.

Alternative energy sources

Solar water heating

Solar water heating is being considered as an alternative to fossil fuel heating in a number of hospitals. The effectiveness and the practicality of using SWH depends on the structure of the building, particularly the roof, and the existing hot water reticulation system.  A system consisting of 92 collectors has been installed at the Netcare Union hospital in Gauteng and is expected to result in a >80% savings in water heating costs.

Rooftop solar PV

Rooftop and parking area solar PV is being installed widely at hospitals and medical centres. The advantage of solar PV is that the visitor parking areas can be used to accommodate panels, as well the building rooftops. Solar PV also matches the load profiles of medical centres, which generally do not operate at night.

References

[1] A Cunningham: “ Designing energy efficient hospitals ? First let’s give you the facts on existing performance” Western Cape Government Health Department, 2015.
[2] Netcare: “Environmental report 2016”
[3] J Fraile: “A Boiler Room in a 600-Bed Hospital Complex: Study, Analysis, and Implementation of Energy Efficiency Improvements”,  Energies 2014, No. 7.
[4] A Bhatia: “Heating, ventilation & air conditioning design for hospitals & healthcare facilities”, PDH online learning.
[5] NREL: “Healthcare Facilities: Advanced Energy Retrofit Guide: Practical Ways to Improve Energy Performance”,  www.nrel.gov/docs/fy13osti/57864.pdf
[6] USDoE: “Hospitals Discover Advantages to Using CHP Systems”,  www1.eere.energy.gov/buildings/publications/pdfs/alliances/hea_chp_fs.pdf
[7] Discussion with suppliers at SAGA conference on combustion, Pretoria, March 2018.

Send your comments to energize@ee.co.za

The post Energy usage and efficiency in hospitals, clinics and medical facilities appeared first on EE Publishers.

Source: EE plublishers

More news