Desiccant HVAC systems for commercial buildings

Abstract

HVAC systems with desiccant wheel (DW) are energy efficient, with a low ambient impact, and can be profitable if compared to traditional systems. They also allow a better indoor air quality. In this paper the summer operating costs of both the desiccant and traditional systems are obtained using three software codes. Two are based on DOE calculation engine (PowerDOE and DesiCalc™), one (DTPE) is an autonomously developed code, based on a subdivision of the psychrometric chart in zones, each one corresponding to a different air handling. DOE and DTPE take into account the most recent DW performance values. Calculation assumes hourly weather data extracted from the European file named “Test Reference Year” (TRY) and appropriately processed. With reference to operating costs of the desiccant systems in summer Italian conditions, for a retail store application, interesting savings (up to 35%) are obtained, as well as reduction in thermal cooling power (up to 52%). Starting costs of the desiccant system are generally greater with respect to the traditional system; considering the present costs of the Italian market, a simple payback of about 5–7 years is obtained. If slightly de-rated DWs are considered, the payback attains lower values, near to 3–4 years.