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Michael D. Haughey, P.E., LEED AP, Principal
Projects
Lucile Erwin Middle School Ice Thermal Storage System, Loveland, Colorado
Design of chilled water system for a new middle school using ice thermal storage and highly innovative flexible storage and pumping system concepts. Evaluated cooling alternatives and local utility incentives for a new Thompson School District middle school. Ice storage concept is basically a demand-limit-controlled, chiller priority, ice-thermal partial-storage system. The system includes variable flow chilled water distribution and ice storage pumping for energy savings. Energy cost savings are optimized with continuous monitoring of building kW demand and modulation and shut-off of the chiller.
The system avoids and reduces the building electrical demand peak by shifting loads to the off-peak rates. This saves raw energy at the power plant as well since the utility distribution system is more efficient during off-peak. Dedicated pumps for the chiller, storage, and distribution save energy by only pumping though the active equipment and systems. Automatic modulating ice-cooling input ensures constant cooling regardless of load. To further reduce demand peaks, three of the eleven RTUs’ cooling can be load-shed.
The project started with a 279 ton cooling load. The load was reduced primarily with a lighting design change, to 190 tons. The ice storage system allowed further reduction in chiller size to 105 tons which are automatically supplemented by up to 107 tons of ice-melt capacity. The system was fully commissioned from design through final optimization after construction. Actual utility bill data show a 4.1 year simple payback period (about a 25% return on investment). The system performed slightly better than the energy model simulation.
Lucile Erwin Middle School
Ice-making chiller and ice storage tanks
Ice storage and chilled water piping
The following is a photo of the factory-assembled package of controls, pumps, valves, variable frequency crives, and core piping. The package was delivered in three sections to fit through the mechanical room door.
Factory-assembled package of pumps, controls, VFDs, and valves
Touch-screen control panel