Case study: Museum HVAC upgrade requires precision control

The Art Institute Chicago has been proactive in reducing its energy usage and operating its systems efficiently. Maintaining both temperature and humidity is critical when storing and displaying artwork as they can affect the physical and chemical properties of the materials used in the artwork.

Figure 1: Chilled water supply and return temperatures at The Art Institute of Chicago show temperature differences between 7°F to 9°F before the implementation of pressure-independent control valves. After 85% of the pressure-independent control valves were installed and calibrated, temperature differences between 10°F to 15°F were realized — even greater than the temperature differences originally specified for the system. Courtesy: McGuire Engineers

High temperature and humidity can cause materials to expand, contract, warp and degrade, leading to permanent damage to the artwork. High temperatures can accelerate chemical reactions and cause paint to crack, fade or become brittle. Low humidity can cause materials to dry out and become brittle, while low temperatures can cause condensation and damage to delicate surfaces.

Figure 2: The iconic main entrance to The Art Institute of Chicago, where the installation of pressure-independent control valves in the chilled water system reduced chilled water energy usage by mitigating low delta T syndrome. Courtesy: McGuire Engineers

Maintaining temperatures within an appropriate deadband requires precision control of the cooling, heating and humidification systems.

Additionally, energy costs have only increased and demand charges by the local utility company represented approximately 22% of the energy cost in 2013 and was projected to be approximately 42% in 2016. Opportunities to reduce energy usage and increasing energy efficiency were a driving factors by the decision makers.

With a chilled water temperature difference of 7°F to 9°F and even worse during unoccupied hours, any increase in temperature difference would save both pumping energy and potentially reduce the quantity of operating chillers. The chilled water plant operated at an average of 0.93 kW/ton before any changes were made to the system.

Figure 3: The Art Institute of Chicago’s Modern Wing Building was also included in the pressure-independent control valves upgrade to reduce the central chiller plants energy usage. Maintaining strict temperature and humidity controls requires more energy than typical commercial buildings so The Art Institute has an innate interest in reducing energy consumption. Courtesy: McGuire Engineers

Pressure-independent control valves were introduced to the operating team as an opportunity to increase energy efficiency and reduce energy consumption. As a result, an implementation cost of approximately $350,000 was met with a simple payback of 2.4 years before any utility incentives. The operation of the plant was reduced to an average of 0.73 kW/ton. Temperature differences were also greater than originally specified for the system.

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