Integrated Ice Storage/Sprinkler HVAC System Sharply Cuts Energy Costs and Air-Distribution First Costs

Abstract

Integrated ice thermal storage/sprinkler HVAC systems developed and applied by the author in several commercial applications shift a major portion of electric utility demand to cheaper off-peak hours, while also reducing significantly the first cost of distribution ductwork. Savings of up to 80% in primary duct and air handler costs (compared to a traditional all-air HVAC system) partially offset the first cost of ice storage equipment, which in turn permits a 50% reduction in utility energy costs for air conditioning in some facilities. The basic ice storage/sprinkler HVAC system is described as well as optional subsystems, such as cogeneration, that are cost-effective under certain conditions. The system's design parameters, psychrometric process, and thermodynamic characteristics are presented and two installations are described, a 223,000-sq ft shopping center and a 150,000-sq ft, two-story retail store. Reductions in the size and first cost of primary air-handling equipment and ductwork are achieved by distributing a small quantity (0.1 to 0.2 cfm/sq ft) of very dry, 40°F primary air. All dehumidification is handled by the ice-chilled primary air, which is distributed in variable, volume, determined by the space dehumidification requirement, to fan-coil induction terminal units. The primary air is mixed with fan-induced room air in the terminals prior to distribution to the space at a constant volume. The fan-induction terminals contain cooling coils connected to the integrated sprinkler system, which circulates chilled water from the central plant through the coils when additional sensible cooling is required. This chilled water is at a thermodynamically efficient elevated temperature (58-68°F), since it handles sensible cooling load only.