Date of Award

Spring 1-1-2013

Document Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Michael Brandemuehl

Second Advisor

John Zhai

Third Advisor

Moncef Krarti

Abstract

Supermarkets are the most energy intensive buildings in the commercial sector, and are responsible for approximately 54.5 billion kWh of electricity annually. Refrigeration makes up approximately half of this electricity use, with store temperature and humidity having a significant impact on this. Conditioned store air exchanges both moisture and heat with the refrigerated cases, and increases in store temperature and humidity impose higher loads on the refrigeration and cause sweating and frost.

Reducing the store humidity level has been shown previously to have a positive effect on the refrigerated case energy use, however dehumidification has an energy penalty on the HVAC system.

The project assessed the potential for energy savings due to humidity in supermarkets by optimizing the design and operation of the combined HVAC and refrigeration systems. The assessment included the effects of climate, space temperature and humidity setpoint controls, HVAC system and layout, and the design, operation and layout of the refrigerated cases.

EnergyPlus was used to model a typical store, and a fractional factorial analysis was conducted to analyze the effects and interactions of a selection of refrigeration and HVAC factors. The results showed that, contrary to initial expectations, the HVAC factors had significantly less influence than had been expected. Refrigeration factors dominated all cases, and changing the zoning and humidity setpoints of the supermarket had very small influence on the total electricity use. However moving the refrigerated cases around between store zones had a significant influence. If only a limited budget is available, it would be best spent on improvements to the refrigeration system, as this will have the most significant influence on the energy use of the store.

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