A typical commercial rooftop air-conditioning unit (RTU) Credit: Oak Ridge National Lab

A typical commercial rooftop air-conditioning unit (RTU).

Credit: Oak Ridge National Lab
Chart showing ratios of energy efficiency ratings at integrated energy efficiency rating conditions, DR-55 vs. R-410A

Lead Performer: Oak Ridge National Laboratory - Oak Ridge, TN
Partners: Trane Company, Ingersoll Rand Inc. - Davidson, NC
DOE Funding: $1,914,000
Project Term: October 2011 - October 2016

Project Objective

The outcome of this project will be the development of a rooftop air conditioning unit (RTU) providing cooling capacity above 150,000 Btu/hr with an Integrated Energy Efficiency Ratio (IEER) of 22 (at the AHRI 340/360 rating conditions). ORNL will work with Trane Company, Ingersoll Rand Inc., to design an innovative system configuration and select high efficiency components. Using the DOE/ORNL Heat Pump Design Model (HPDM), numerous system configurations will be modeled and evaluated to conduct design optimizations to develop an RTU reaching the IEER goal with minimum cost premium.

Lab breadboard and production ready prototype units will be constructed by Trane. Controlled testing of the lab breadboard unit at ORNL will be used to verify the key performance targets. The test data will be used to calibrate the HPDM and produce performance maps for building energy simulation and energy savings assessment. Payback periods will be estimated by comparing projected savings with cost figures provided by the manufacturer. ORNL will extend the design to cover a whole product series ranging from 10-ton to 20-ton cooling capacity. In addition, ORNL will conduct field testing for one RTU in ORNL’s Flexible Research Platform.

Project Impact

More than half of U.S. commercial building space is cooled by RTUs. Existing rooftop HVAC units consume more than 1.3% of total US energy annually (1.0 Quad source energy). If built to meet the target specification of 22 IEER, ORNL estimates that these units would reduce energy use by as much as 50% over current standards. Nationwide, if all 10 to 20-ton RTUs met the IEER goal, ORNL estimates businesses would save over $1 billion each year in energy costs, helping American companies better compete on a global scale.


DOE Technology Manager: Tony Bouza
Performer: Bo Shen, Oak Ridge National Laboratory

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