In a report written to support the New York State Department of Environmental Conservation (DEC), industry experts concluded that investments must be made in alternative heat pump designs such as hydronic loop systems to facilitate the transition to natural refrigerants in this equipment, particularly propane (R290).

These “indirect systems,” such as chillers and air-to-water heat pumps, which are commonly employed in Europe, “can leapfrog to natural refrigerants more easily and be used for combinations of purposes (e.g., space heating, cooling, and domestic hot water),” the report said. These systems keep the refrigerant outside the facility and use either water or a glycol/water mix for heating or cooling inside.

This technology presents a unique opportunity, the report added, “for holistic decarbonization to simultaneously tackle direct (refrigerant) and indirect (energy-related) GHG emissions by minimizing energy consumption as well as the number of appliances that are added to the grid while removing several fossil fuel-based appliances.”

Published last September, the report titled “New York State Assessment of Natural Refrigerants,” was prepared by consulting group êffecterra (with Richie Kaur of êffecterra as corresponding author) based on eight technical working group meetings convened to discuss the opportunities and barriers for the adoption of natural refrigerants in New York State. The working groups included climate science and policy experts, manufacturers and suppliers of equipment that uses natural refrigerants, design and engineering consultants, safety standards and building code experts, nonprofit policy advocacy organizations and representatives of end users, as well as New York State and City officials.

The New York State DEC is currently accepting comments on its ambitious proposed rule amending regulations of HFCs, which would include GWP limits of 10 for many new HVAC&R systems by 2034 and help foster the adoption of natural refrigerant-based applications.

Comments can be sent to Suzanne Hagell at climate.regs@dec.ny.gov, with “Comments on Part 494 HFC” in the subject line of the email, until 5 pm EDT on March 19, 2024. A public comment hearing on the proposed rule will be held via electronic webinar on March 13, 2024 at 2 pm EDT.

Paradigm shift

The report pointed to a “paradigm shift” that would be needed to deploy natural refrigerants in air-conditioning and heat pump equipment. “Innovations in system design and the ability for systems to effectively be retrofitted are essential to transitioning to ultra-low-GWP natural refrigerants in AC and heat pump equipment,” it added. “This is also the sector that needs a transition the most if we are to maximize the climate benefits from building electrification and adoption of heat pumps.”

Common AC system architectures currently used in the U.S., such as central ducted residential AC and VRF (variable refrigerant flow) systems, are “not conducive” to the use of natural refrigerant alternatives because they don’t allow “drop-in” retrofits. Thus, to use natural refrigerants in heat pumps while minimizing safety risks, investments must be made in both alternative system designs (such as hydronic loop systems) as well as innovative retrofits, such as the reuse of existing refrigerant copper piping as water piping in air-to-water heat pumps.

The report identified several key advantages of integrated/combination indirect hydronic heat pump systems:

● Integrated/combination indirect heat pump systems using natural refrigerants that perform multiple functions – such as space heating, cooling and domestic hot water – can simultaneously reduce refrigerant impacts, replace multiple fossil-fuel based systems at once, minimize the number of electric appliances, and help potentially mitigate the urban heat island effect.

● For multifamily homes, the source of heat for integrated indirect heat pumps could be neighboring water bodies.

● Indirect systems use less refrigerant than corresponding direct expansion systems while serving the same heating/cooling load; this mitigates safety risks and direct refrigerant emissions, allowing the use of natural refrigerants in indirect system architectures.

● Indirect systems allow for capture of waste heat which can be used when needed to meet simultaneous cooling and heating needs.

● Indirect systems are suitable for load shedding or demand responsiveness because the secondary loops act as “thermal energy loops” that can function even when power is shut off (for some time).

● For parts of the U.S. where radiant heating systems are still widely used (such as Northeastern states), indirect systems are a relatively simpler retrofit solution since these can be added into existing buildings and connected with existing radiant heating systems.

● Use of integrated indirect heat pumps can help address workforce shortages while stimulating job growth in multiple labor sectors. For example, installation of indirect or hydronic loop systems requires plumbers to lay the secondary fluid loop, while the heat pump system is self-contained and relatively simpler to install and maintain, thus reducing the strain on the HVAC technician workforce.

● Due to their superior thermodynamic properties as refrigerants, an indirect system using ammonia or propane can be more energy-efficient than a direct HFC system serving the same cooling load.

● Coupled with building decarbonization and electrification efforts, the use of natural refrigerants like hydrocarbons in heat pumps will help remove very large amounts of flammable fossil fuels that are continuously combusted and replace them with much smaller amounts of highly energy-efficient natural refrigerants which, if maintained well, will rarely or never need to be replenished.

The report noted that outdoor indirect systems, such as rooftop chillers, may be able to use R290 as early as 2026, if relevant proposals are approved by safety standard committees. “The main reason the process is moving faster for these systems is that they minimize the risks related to the flammability of A3 refrigerants by using relatively smaller amounts of refrigerant and locating them outside the building, away from occupied spaces and dwellings,” it said. Other AC and heat pump equipment may be able to use R290 by 2030, “provided undue delays at state and local levels are minimized.”

It will most likely not be until “2025 or later” before an ASHRAE standards committee approves the use of up to 4.9kg (10.9lbs) of A3 refrigerants like propane in outdoor (indirect) heat pumps and air conditioners in the U.S., according to Jim VerShaw, chair of ASHRAE’s SSPC (Standing Standard Project Committee) 15.2 and Chief Engineer, Residential HVAC for Trane Technologies. SPCC 15.2 oversees ASHRAE’s 15.2-2022 Safety Standard for Refrigeration Systems in Residential Applications. The proposed amendment to increase in the charge limit for A3 and A2 (less flammable) refrigerants falls under Addendum E.

The Environmental Investigation Agency (EIA) has given its support to allowing up to 4.9kg of R290 in outdoor heat pumps and air conditioners in the U.S.

“Indirect systems can leapfrog to natural refrigerants more easily and be used for combinations of purposes.”

New York State report prepared by êffecterra