Seminar 62 - Thermodynamic Limits for Buildings

Track: Fundamentals and Applications
Sponsor: 7.4 Exergy Analysis for Sustainable Buildings (EXER)
Chair: David Vernon, Associate Member, UC Berkeley Center for the Built Environment, Berkeley, CA
This seminar addresses the issues mechanical system design engineers encounter in daily situations, but cannot appropriately address with energy analysis only. Since exergy analysis enables the comparison of different forms of energy and different energy qualities, it makes it possible to optimize the performance of an HVAC system holistically, including fan and pump powers. This seminar includes presentations from practitioners and from researchers, and covers the applicability of exergy analysis in optimizing the HVAC system performance, and how we can use exergy analysis to reach net zero energy or exergy building targets.

1. Thermodynamic Limits for Air-Conditioned Buildings
William Kopko, Member, Johnson Controls, Chiller Solutions, Technology and Innovation Group, New Freedom, PA
For commercial buildings built to modern energy codes, fan and pump energy usage frequently exceeds that of compressors. For large chillers, codes require a design efficiency of approximately 60% of the Carnot limit, but fluid flow in a building does not face similar thermodynamic limitations. For example, duct pressure drop is roughly proportional to duct length over diameter to the fourth power, which means that duct pressure drop and corresponding fan energy can approach zero with appropriate duct design. In addition, reducing the indoor fan power reduces the cooling load, an effect that is generally ignored in building energy analysis.

2. Exergy in Air Conditioning
Mike Trantham, Member, IMI Flow Design, Dallas, TX
A few simple calculations based on the Carnot cycle show that thermal control of buildings, even given the same heat loads, could happen with less energy input than current systems consume. Exergy analysis is used to numerically calculate losses in a cooling system. Every time heat is transferred across a temperature differential, work that could have been done is lost. Similarly, every time work becomes heat, that work cannot practically be retrieved. By identifying and numerically comparing various losses, one can identify primary targets for improvement in the effort to achieve net zero energy or exergy buildings.

3. Holistic Analysis of HVAC Systems Using Exergy
Ongun Berk Kazanci, Ph.D., Associate Member, Technical University of Denmark, Kgs. Lyngby, Denmark
Exergy analysis enables the comparison of the effects of operating temperatures on system performance and different forms of energy flows (e.g. heat and electricity), allowing for a holistic system analysis. This presentation outlines the main principles of exergy analysis and presents the results from the comparison of different heating and cooling systems using exergy.

Presented: Wednesday, January 24, 2018, 9:45 AM-10:45 AM
Run Time: 60 min.

This is a zip file that consists of PowerPoint slides synchronized with the audio-recording of the speaker (recorded presentation), PDF files of the slides, and audio only (mp3) for each presentation.