DOE Report: High Efficiency HVAC Systems
In 2017, the U.S. Department of Energy’s (DOE) Building Technology Office (BTO), a part of the Office of Energy Efficiency and Renewable Energy (EERE), engaged Navigant Consulting, Inc. (Navigant) to study and develop a report on heating, ventilation and air conditioning (HVAC) systems for commercial buildings. The final report - Energy Savings Potential and Research, Development & Demonstration (RD&D) Opportunities for Commercial Building HVAC Systems, is an update to a 2011 report of the same name and incorporates new market information, technology trends and BTO research priorities.
The main objectives of the study were to identify a wide range of technology options that could reduce commercial HVAC energy consumption; characterize these technology options based on factors affecting end-user acceptance and the ability to compete with conventional HVAC technologies; and make specific recommendations to the DOE and other stakeholders on potential RD&D activities that would support further development of the most promising technology options.
According to the U.S. Energy Information Administration's (EIA) 2017 Annual Energy Outlook (AEO), the U.S. commercial building sector will consume approximately 17.83 quadrillion Btu (Quads) of primary energy in 2017. As shown in Figure 1, HVAC systems will consume 5.35 Quads, which is 30% of the total commercial building energy consumption.
Navigant identified more than 300 technology options that showed promising potential to reduce the energy consumption of commercial HVAC systems, and selected a subset of 84 technology options for further, more thorough evaluation. A final set of 18 high priority technology options was selected for even more evaluation and grouped into the following categories based on similarities:
- Technology Enhancements for Current Systems improve the performance and energy efficiency of the current generation of HVAC equipment and systems.
- Alternative Electrically Driven Heat Pump Technologies provide heating or cooling more efficiently, using advanced vapor-compression or non-vapor-compression technologies, and use electricity as the primary energy input.
- Alternative Gas-Fired Heat Pump Technologies provide heating or cooling more efficiently, using a thermally activated heat pump cycle, and use natural gas as the primary energy input.
- Alternative System Architectures provide localized comfort to building occupants to reduce the operating requirements for traditional HVAC systems.
Table 1 lists the high priority technology options, their estimated technical energy savings potential and their final ranking.
Figure 2 highlights the technical energy savings potential of the high priority technology options, by technical maturity. Most technologies could provide approximately 10% energy savings for U.S. space cooling and heating energy consumption for commercial buildings (3.81 Quads/yr. for space cooling and heating, 5.35 Quads/yr. total). Most technologies only provide energy savings for either space cooling or space heating, but some cover all of commercial HVAC energy consumption. HVAC energy savings opportunities for commercial buildings exist across all technical maturity levels, with several technologies in the initial stages of commercialization.
Once fully developed, these technologies are projected to be suitable and attractive for commercial buildings based on their scores in cost and complexity, non-energy benefits, and peak-demand reduction potential.
Cost and Complexity
Most researchers project reasonable payback periods for these technologies, especially for buildings having high HVAC loads because of their operating hours and/or climate. Regarding complexity, building owners and HVAC system designers value technologies that can easily integrate with existing buildings, do not require substantial changes to building envelopes or distribution systems, have limited size and weight concerns, and do not increase operational or maintenance complexity. Nevertheless, most of the technologies profiled here are in the early-stages of development, and reliable estimates of equipment cost, installation requirements, operating and maintenance costs, etc., are unavailable.
Non-Energy Benefits
Beyond energy savings, each of the high priority technology options provides other benefits that may be attractive to building owners and operators. Benefits such as improved occupant comfort, better indoor air quality (IAQ), lower equipment noise and vibration, and the ability to use zero- or low-global-warming-potential (GWP) working fluids, could support the increased market adoption of these technologies. Many end-users would view comfort and IAQ benefits as having the same level of importance as energy savings.
Peak Demand Reduction
Reducing electrical demand from HVAC systems during peak hours is increasingly important for electric utilities and other stakeholders, as late-afternoon cooling loads often strain the existing capacity of the electrical grid or the availability of power. This can be reflected as higher prices – demand charges or time-of-use prices – for the end-user. Technologies that can reduce electricity capacity requirements by using natural gas (e.g., gas-fired heat pumps) or shifting electricity consumption to off-peak hours (e.g., battery storage for personal comfort devices) would have a significant benefit to both grid operators and, through lower demand charges or peak-hours consumption, building owners. In addition, utilities with high electrical heating adoption on their system experience winter peaking events, and technologies that offer electricity savings during peak winter events are also valuable.
Take a deeper dive into these 18 high efficiency HVAC technologies and access the full report at https://www.energy.gov/sites/prod/files/2017/12/f46/bto-DOE-Comm-HVAC-Report-12-21-17.pdf.