The rapidly rising cost of A/C energy is a problem for hospitals everywhere, and McAllen, Texas is no exception. In a town where 90+o F days are common year-round, and the mercury can top the 100o F mark even in winter, the seasons might be described as "hot and hotter". But at McAllen's Rio Grande Regional Hospital, an HCA-affiliated hospital with 320 beds, administrators are staying cool with the knowledge that - even in the face of a 33 percent utility rate hike - their electric bill has declined over the past two years. What accounts for this phenomenon? "We attribute it to the incorporation of UVC lights from Steril-Aire, Inc. (Burbank, Calif.) into the air handling systems," says Oscar Molano, director of plant operations for the hospital.
"We were looking for a way to save on A/C energy costs without compromising air quality or patient comfort," Molano explains. Working with Rio Filter Supply Company (Harlingen, Tex.), he learned that high-output ultraviolet-C band or "UVC" devices have become a popular addition to new and existing HVAC systems because of their multiple performance benefits.
The energy emitted by the UVC devices is the most germicidal in the ultraviolet spectrum. Properly installed in air handlers, high-output UVC lights penetrate even the tiniest microbes to destroy their DNA and RNA, killing or deactivating them. In this manner, the lights effectively degrade mold and other organisms that grow deep inside HVAC systems as well as airborne microbes that circulate through these systems to the occupied space.
Decades-old studies have shown that even a microscopic layer of organic buildup on A/C coil fins can create a noticeable drop in system efficiency. By eliminating this buildup and preventing its recurrence, Steril-Aire UVC devices keep coils continuously clean. This, in turn, lowers HVAC energy costs by improving heat transfer and increasing net cooling capacity.
At Rio Grande Regional, 17 air handling units (AHUs) are nine years old and range from 20 - 80 tons. Nine AHUs are four years old and are 70 - 80 tons. After reviewing the potential benefits, Molano approached the hospital's CEO and received approval to retrofit the 26 AHUs with UVC on a phased basis. "We started early in 2005 and converted one or two AHUs every month thereafter," says Molano. The devices used are Steril-Aire DE (double-ended) Series UVC EmittersTM, which are designed for installation in large commercial HVAC systems.
$500K savings projected
"As our UVC retrofit program has progressed, we have seen a continuing and dramatic improvement in energy performance," says Molano. He cites the following:
- Before any UVC devices were installed, the four 465-ton chillers serving the hospital were running at 99 percent capacity. Chilled water "in" measured at 43o F, chilled water "out" at 64o F.
- About 18 months later, after most of the AHUs had been equipped with UVC, the same chillers were running at only 62 percent capacity. Chilled water "in" remained at 43o, but chilled water "out" temperature had decreased to 53o F, an 11-degree drop.
- During that period, electrical usage (in kilowatt hours) declined 20.64 percent. This essentially cancelled out an equivalent rise in utility rates from $.06 per kWh to $.08 per kWh. As a result, with the addition of UVC throughout the hospital in 2005 and 2006, the electrical energy costs from 2005 to 2006 remained at a constant average of $166,900 per month.
- By fall of 2006, as Rio Grande was wrapping up the conversion to UVC, they determined that the hospital was now too cold, even with the chillers running at reduced capacity. In late October they shut down two chillers completely, along with the accompanying chilled water pumps, condenser water pumps and cooling towers. The two operating chillers are now running at 80 percent capacity, with chilled water "in" at 43o F and chilled water "out" temperature at 60o F. Kilowatt hours continued to decline, and from January through May 2007, energy expense was down $240,885 compared to the same time period in 2006. Based on this trend, annual energy savings in the $500,000+ range can be projected.
"Needless to say, the recent cutback to two chillers will bring even more significant reductions in our energy cost," says Molano. "UVC technology has made a remarkable difference here. We used to need four chillers even when the temperature outside was 70 degrees, and now two chillers do the job at 90 degrees."
IAQ, maintenance benefits
UVC energy destroys airborne microbes, including all types of viruses and bacteria. It thereby helps to maintain cleaner indoor air and reduce the risk of cross-infection in healthcare facilities. Though Rio Grande has not yet studied this aspect of UVC performance, some hospitals have reported reductions in nosocomial infection rates since adopting the technology.
UVC also helps control indoor humidity and comfort levels by keeping air conditioning components running cleanly and efficiently and improving airflow through the coils. All 26 AHUs are now running in "as new" condition. Every coil and drain pan is pristine clean. "Our nursing staff, patients and others seem very happy with the air quality in the facility," Molano states.
HVAC maintenance has also been enhanced. Though the hospital still does occasional pressure-washing of A/C coils with water, they have eliminated the use of acid for cleaning. In addition, drain pans stay clean and free of organic debris, so no further cleaning of these components has been needed. Rio Filter Supply performs all services on UVC Emitters including periodic checks and measurements of performance."Of course, we are pleased about the enhancement to our already good IAQ, and with the ability to reduce or eliminate certain maintenance tasks. But right now, the energy savings we are achieving with UVC are first and foremost. This technology has tremendous potential for all types of buildings and homes," Molano concludes.