Research GAHP Screening Criteria & Design

This Gas Emerging Technology (GET) project includes research into site screening criteria and sizing methods for gas absorption heat pump water heaters (GAHPs). GAHPs have been around for many years, but the application of this technology to domestic hot water (DHW) systems is novel and presents several challenges. Legacy DHW heaters are often sized for the maximum expected DHW load and can meet the maximum and minimum expected DHW loads. GAHPs, on the other hand, require a minimum DHW load to function optimally with a fixed baseline load and are recommended to be sized to 40-60% of the DHW load. There is evidence that the DHW heater/boiler sizing methods currently in use overestimate DHW load, which becomes a problem when the GAHP requires a minimum load to function properly. Further complicating matters is the fact that many DHW retrofit projects in the multifamily segment are completed by contracting companies who do not have engineering staff to run DHW sizing calculations or come up with new designs for each retrofit project. Contractors generally rely on outside engineers or manufacturers to provide them with recommended DHW heater/boiler capacities and designs. Additionally, contractors need to have rough ideas of project costs up front to sell a project to a multifamily property. In order for the GAHP to be successful as an energy efficiency (EE) measure in the California multifamily market, the contractor community needs to be provided with tools to quickly screen sites for GAHP retrofits and determine the appropriate number of GAHPs to install and appropriate system design. This project seeks to bridge that gap by researching existing methods of DHW sizing, researching what information contractors can typically collect, and providing recommendations for site screening criteria and GAHP sizing and design.