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Dedicated Heat Recovery Virtual Chiller Provides Savings for NASA

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©2019 This excerpt taken from the article of the same name which appeared in ASHRAE Journal, vol. 61, no. 1, January 2019.

By Michael Reed, Member ASHRAE; Wade Robinson; Norm Hawes

About the Authors
Michael Reed is a contract employee at MSFC serving as the internal energy conservation engineer, Wade Robinson is a contract employee in charge of the Utility Controls System (UCS) operation and onsite programming and Norm Hawes is the UCS program manager for NASA MSFC at Aetos Systems.

NASA at the Marshall Space Flight Center (MSFC) in Huntsville, Ala., consolidated 32 building chilled water (CHW) systems into a single central chilled water plant (CCWP) in 1999. Converting existing buildings to variable flow and installation of 12 miles (19.3 km) of underground pipe, a 10,000 ton (35 170 kW) chiller plant, plus a fully automated control system was a monumental task. The team working on this forward-thinking and energy-efficient plant has continued to find ways to save money for MSFC with a central water side economizer, a thermal energy storage (TES) system for reducing the electrical peak cost, variable frequency drives (VFD) on all pumps, fans and four chillers as well as several optimization projects. The latest project, described in this article, is the installation of a Dedicated Heat Recovery Chiller (DHRC) as a virtual chiller at a laboratory building connected to the CCWP. Photo 1 shows the Propulsion Research and Development Laboratory Building 4205.

A DHRC is a chiller designed specifically to capture heat from a water source often slated to be “thrown-away” to the atmosphere or ground. This specific chiller can be operated controlling a heating or cooling load through an option selection within the chiller’s “onboard” computer. For our installation, the function selected was to control the heating side of the chiller. CCWP distributed chilled water return is the heat source for this installation. The heat side of the DHRC is used at Building 4205 to provide heat for the existing hot water system rather than use the original propane boilers.

The CCWP distributed chilled water system gathers heat from the MSFC data center, high-bay buildings, office buildings and laboratories. Even on the coldest day of the year approximately 750 tons (2638 kW) of heat is collected from these buildings. All of this heat is ultimately dissipated to the atmosphere through the cooling towers at the CCWP. This DHRC is connected to the miles of CCWP distribution piping as a supplier of chilled water to the system. The DHRC removes heat from the CCWP return water system and returns chilled water to the CCWP supply system. To the overall system the DHRC can be considered a “virtual” chiller. This is a chiller that is not located at the CCWP but is doing the same work on the same distribution system as a chiller at the CCWP.

The DHRC has been operational since July 20, 2016, eliminating propane heating and thousands of pounds of pollutants from the atmosphere. Thousands of gallons of water evaporation per year was eliminated at the CCWP cooling towers including the corresponding chemical treatment. The DHRC saves over 80% of the operating cost of the original propane heating system. In addition to fuel cost savings, the DHRC has the added benefit of eliminating the pollutants caused by burning fossil fuel and reducing water consumption.

This article will describe the system, the installation process, and some operational hurdles overcome in actual operation.


Background

The Propulsion Research and Development Lab was built in 2005 with propane as its heating source. This building was a good selection for a DHRC because of two main factors. First, dehumidification is necessary during the summer. Second, the building requires winter building heating. The MSFC energy manager was able to acquire funding from the NASA HQ energy program to install this DHRC project. To ensure its successful implementation, a group of onsite contract engineers aided by the proposing and controls engineers all worked together on the bid design.


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