Power Line case study: saving energy in hospitals can pay dividends

Editor's note: If you're looking for customers with the potential to realize substantial energy savings, you might want to look at hospitals. Western's Power Line answered this question about energy efficiency in hospitals in May 2000. Many of the suggestions apply to other large institutions, as well. If you have questions about specific types of projects, please call the Power Line at 1-800-769-3756.

Question:
Do you have general information about conservation, efficiency, and preventive maintenance for HVAC systems in hospitals?

Answer:
You are wise to be asking this question because hospitals have high utility costs. The average energy use when measured on a per-square-foot basis varies greatly, depending on age and type of facility, number of beds, laundry use, emergency care and intensive care, surgical operation, kitchen use, etc.

Historical data shows that hospitals use anywhere from a low of 200,000 Btu/SF per year to more than 500,000 Btu/SF per year, with the median energy use being about 350,000. This data is from the early 1990s. We have not been able to find any recently published information.

Earlier data from the mid 1970s showed higher average energy use per square foot (around 480,000Btu/yr), but building use and types of mechanical and ventilation systems were much improved from 1975 to 1990. Nonetheless, there are still many efficiency improvements that can be made with improved systems and control technologies.

A report published by CADDET in 1996 titled "Energy Savings in Hospitals" noted the following averages for hospitals in colder climates. Of all energy used, about 40 percent is electric and 60 percent is other fuels. Of all energy use in hospitals, up to one-third goes to space heating, up to a quarter goes to hot water heating, 10 to 15 percent goes to ventilation air treatment, 15 to 20 percent goes to lighting, and the rest goes to other process uses. Cooling loads vary with climate and trade with space heating loads.

Regarding energy use in nursing homes and convalescent centers, nursing homes have been compared to hotels in energy use because of the similarity in sleeping rooms and their relationship to service areas.

There are many similarities in design as far as layout, windows and exterior exposure, relationship to bathrooms, housekeeping and laundry, lighting and mechanical systems.

Average energy use for nursing homes was 92,000 Btu/SF per year compared to 96,000 Btu/SF per year for hotels. Unfortunately, this average is not broken down by fuel type. Wings of hospitals that house patient care facilities might experience similar energy use.

Specifics on conservation and efficiency

Auditing: Auditing an existing facility is always a productive activity. If nothing else, it gives you a list of connected loads you can use for planning and justifying maintenance activities. There are many ways to perform an audit.

The list of connected loads you generate from that audit should contain hours of operation. From that you can look at managing your loads.

In conjunction with your audit you will want to do some energy accounting to see what your energy use profile looks like. In addition to an annual or two-year profile, you can do weekly, daily, or even hourly use profiles by having someone record your meter readings on a weekly, daily or hourly basis and notate periods of heavy or light use.

The profiles should match with your listed hours of operation for various equipment. If it does not, further investigation is needed.

Load Shedding: Load shedding is used to reduce your rate of electrical energy use to the minimum rate during the hours your utility company charges the highest for electrical demand.

Some companies have a time-of-day demand rate and others charge for the highest rate used during the entire billing period. If you have time-of-day rates, try to operate equipment during off peak period. If you are charged for the highest rate during the billing period, figure out what the highest combination of equipment is that you must operate at the same time, and try to operate all other equipment at other times so the peak is not exceeded.

Some utilities have higher rates during certain months; it may not be possible to curtail some equipment operation for months at a time, but it might be explored.

Lighting control: You mentioned that you?ve done a lighting and control retrofit project. You can calculate the savings by going back and monitoring hours of operation to make sure the controls are working.

Variable speed motors: During the audit you may find a number of fans and pumps that are candidates for variable speed control.

Ventilation systems usually have opportunities for energy savings because they are usually sized for maximum ventilation rate and some of the time the spaces are not even occupied.

Sometimes air flow rate is already controlled by inefficient throttling dampers or less efficient inlet guide vanes, both of which can be replaced with variable speed motor drives. These are opportunities to provide variable speed controls for maximum exhaust when needed and provide minimum ventilation when that is all that is needed.

Many pumping systems for heating water and chilled water systems are also candidates for variable speed drives because they are sized for peak design load and could operate the rest of the year at reduced loads.

Emerging technologies

In addition to findings from your audit, there are a number of emerging technologies that can be looked at for conservation and energy savings, especially if you are planning a renovation anyway.

The following items are some of the possibilities:

• If you have a central chilled water system, chillers have become much more energy efficient (up to a 40-percent reduction in kWh/ton) in the last 10 years. Variable speed drives to match loads on cooling tower fans and chilled water pumps can also save operating cost. If you have large year-round chiller use, as well as boiler use, an absorption chiller might be a consideration.
• A combined heat and power system might be a very cost-effective installation if you have a high base electrical load and a constant heating load. Small electrical generating gas turbines can be installed to generate a steady amount of electricity and the exhaust heat from the turbine can be used for a year-round heating load such as hot water. Microturbines are available as small as 30 kW and regular gas turbines are available from about 250 kW and up in size. Combined heat and power systems are up to 80-percent efficient. Heat recovery is something that should be investigated on all building HVAC systems with 24 hour a day operation. Heat (or cooling) can be recovered from exhaust air and ventilation air streams to be used in preheating or precooling incoming ventilation air.
• If you have areas being remodeled that require special air treatment, such as dehumidification for surgical suites, consider the use of desiccant dehumidification that can lower humidity levels more cost effectively than overcooling to dehumidify and causing occupant discomfort.
• Boiler burners and controls have improved significantly over the last decade. If you are looking at modernizing the heating plant, investigate upgrading burners and controls and consider oxygen monitoring and trim control to minimize excess air. If renovating boilers, consider heat recovery on boiler blowdown and possibly an economizer on the exhaust flue.
• Lighting systems are continually improving in efficiency with the development of higher efficacy lamps and electronic ballasts. Dimmable fluorescent ballasts are about $10 more than standard electronic ballasts and can be cost effective in combination with daylight sensors to reduce lighting in larger areas when daylight is available. Dimming can also be manually controlled to reduce light levels when not necessary. Occupancy sensors for lighting control on randomly occupied rooms should be considered.

Preventive maintenance

After assessing and upgrading your equipment, it's time to get proactive with prevention. Preventive maintenance and proactive testing can give a facility security against future problems. In addition to the standard cleaning of HVAC components and assessment of interior elements, preventive maintenance includes ensuring that maintenance personnel?s knowledge is up to par with complex equipment.