Report Shows UV Provides Energy and Cost Savings
Source American Air & Water, Inc.
Dr. Kowalski, PE, Ph.D., Penn State University, developed a strong report that shows UV can be cost justified as a capital expenditure by the savings it provides. The UV installations provide savings in energy and maintenance costs as well as enormous benefits of a healthier indoor environment.
The report reviews the history and current literature on ultraviolet germicidal irradiation (UVGI) cooling coil disinfection and summarizes the available information on laboratory and field testing of UV installations. Information on the energy savings and payback period of cooling coil irradiation are provided along with examples of the computation of typical payback periods.
The report shows that irradiating cooling coils with UV will virtually prolong the life of the HVAC system. The study includes results from existing laboratory and field tests on UV equipment as well as analysis of UV effectiveness for cooling coils disinfection. It provides formulas for calculating return on investment (ROI) and the savings in energy and dollars from improving the efficiency and extending the life of coils. It can reasonably be expected that typical UV installations will produce payback periods of two to four years. That is, the cleaning action of UV on fouled coils is so effective and the reduced maintenance costs and the savings in energy are so significant that the retrofit of a UV cooling coil system typically pays for itself in about two to four years.
The report shows an example where the payback period is achieved in only eight months. The energy savings results from two effects – the reduced pressure loss through the coils and the increased heat transfer in the coils when the fouling film is removed. Both of these can be significant, as can the reduction or elimination of maintenance for the cooling coils. Since the coils will be maintained in a clean condition, there is virtually no requirement for periodic cleaning.
The economic savings that can result from the installation of a UV cooling coil disinfection system can be estimated by comparing the operating costs after installation with the operating costs before installation, minus the cost of installing and operating the UV system. Ideally, operating data would be drawn from field test results. This necessitates installing a UV system. Little published data is available for installed systems, but there are testimonials suggesting UV disinfection systems are fully capable of restoring a fouled cooling coil to approximately the original design operating conditions. The cost savings will then depend on how much coil fouling has occurred and how far the system capacity has been diminished in comparison with the original design conditions.
The elimination of microbiological fouling of the cooling coils can be demonstrated through surface sampling before and after installation of the UV system. An alternative indicator of the effectiveness of UV germicidal irradiation could be coil performance, since the elimination of surface contamination should theoretically restore cooling coil performance to original design values.
Source: American Air & Water, Inc.