Concentration of CO2 in the Atmosphere

Emerging Air-to-water Heat Pump Technology

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Ryan Moag and Margaret Richards

Efforts to decarbonize are taking our nation’s buildings sector by storm, with New York State at the forefront of policymaking for climate-friendly buildings. Given that fossil fuel-supported building operations are responsible for 43% of New York State’s annual emissions, legislators have set in motion an effort to completely decarbonize six million buildings. The mass departure from fossil fuels is already well underway, with two million homes and buildings on track to be equipped with heat pumps for electric heating and cooling by 2030. This progress is encouraging, but the road to electrifying HVAC in New York and the nation as a whole remains a long one. As of 2020, 52% of U.S. households still use natural gas appliances for space heating. This state of affairs poses substantial technical challenges for utilities and HVAC equipment manufacturers alike.

On the utility side, grid capacity remains a substantial barrier to complete electrification; As things stand, fossil fuel appliances account for trillions of BTUs of energy consumption annually. Although heat pumps are hyper efficient, if we were to displace every fossil fuel heating system overnight, the grid capacity does not yet exist to support it. Along the same lines, a great deal of energy is wasted maintaining capacity in reserve for peak demand. During the summer months back-up generation is left idling in anticipation of spikes in cooling loads. Replacing all fossil fuel heating systems with electric systems has the potential to create a second winter-time peak that utilities will have to account for. In other words, the supply side will need sufficient preparations to accommodate a world where the energy needs of all residences are met sustainably.

This is not to say that we should be discouraged about our efforts to completely electrify HVAC in this country and abroad. Jettisoning fossil fuels from every aspect of our life remains the only real option we have. While many people are working on the issues we have raised on the utility side, it is important to remember that this transition will likely require millions of individual home owners to willingly adopt a new technology at their own expense. It can be difficult to convince people to change how they heat and cool their homes – after all, when an old system fails, homeowners tend to simply replace what was there before.

With these obstacles in mind, the rapid decarbonization of the residential energy sector will require a more holistic approach than installing an air-source heat pump in every household. While a complete revision of our energy infrastructure will bring us in sight of the finish line, if no attention is paid to the habits and preferences of the individual consumer, we may still fall short.

Air-to-water Heat Pumps

There’s a reason that split-system air-source heat pumps are at the center of state and federal climate policy. They are exceptionally efficient, cost effective, and can easily be used to retrofit most standard residences and light commercial buildings. They emit at least three times less

greenhouse gasses than the best fossil fuel sources, and their life-cycle emissions will be further reduced as the power grid shifts to carbon free electricity generation.

Government sponsored tax credits and rebates for air-source heat pumps have been instrumental in making the environmentally responsible choice financially favorable. Thus far these programs have been successful in their aim to persuade. That being said, there remain a few areas where fossil fuel systems retain an edge. For example, heat pumps can produce heat extremely efficiently, but most compressors and common refrigerants are not designed to reach the temperatures most traditional water-based space heating requires.

A heat pump system that can act as a turnkey replacement fossil-fuel boiler would enable a more rapid adoption of clean heating and cooling equipment. Hydronic (water-based distribution) space heating has long been appreciated for its exceptional comfort and effectiveness. Radiative heat transfer over a large surface can be better for people with allergies because it doesn’t distribute allergens like forced air systems can.

Until recently, ground-source heat pumps (also known as geothermal) were the primary means of providing hot-water for residential space heating using the heat pump concept.

Geothermal systems are highly effective, but they come with a substantial installation cost as a typical system’s heat exchanger requires a large trench to be dug. In recent years, a few promising alternatives have hit the market. Air-to-water heat pump manufacturers like Spacepak and Enertech have developed systems capable of providing space heating, cooling and domestic hot water in a single package. These systems can run a low-temperature radiant loop year-round without a backup. They can remain operable down to -30°F and can meet building energy demands at a level of efficiency approaching that of a geothermal system. However, these systems do not necessarily function as a direct replacement for the average boiler. With lower water temperature output, these systems often require additional points of distribution.

This means more radiators, air handlers or a larger radiant loop. These products are still an excellent choice for consumers who want climate-friendly water-based HVAC systems, but industry leaders are determined to take their designs a step further.

What’s on the horizon?

Carbon dioxide is a substance that we have become all too familiar with due to the deleterious effects of its steadily increasing concentration in our atmosphere. Ironically, it may play an important role in our transition to more sustainable heating and cooling technologies.

Carbon dioxide when utilized in a heat pump system as a refrigerant can enable heat pumps to produce much higher water temperatures. Industry leader Mitsubishi has launched a commercial hot water system using carbon dioxide to efficiently produce high volumes of domestic hot water, and a number of carbon dioxide based boiler replacements have just begun to be commercialized. In 2022, a multinational Swedish company – Vattenfall successfully launched a direct boiler replacement that is now available in its local market. It won’t be long until comparable products reach the United States. It is also worth noting that these systems come with the added benefit of using a refrigerant that has a much lower warming potential than common refrigerants like R-410a.

Heat pumps continue to defy their historical limitations as manufacturers continue to iterate on their functional designs and new competitors enter the market. Combustion processes are inherently less efficient than the vapor-compression refrigeration cycle. If heat pumps can be brought to market that can provide the same functionality as their fossil fuel equivalent, then the path to electrification begins to seem inevitable. Legislators should be swift to update existing programs to support these technologies as they are rolled out, and fortunately for those residing in New York and Massachusetts, more funding is now on the table.

For Massachusetts residents, you may be eligible for up to $10k per home for an air-to-water heat pump system through the Mass Save® Program. New York has also recently begun to weave air-to-water heat pump systems into their regulatory framework. New incentives for heat-recovery systems and heat-pump chillers through the Clean Heat Program were announced on September 1, 2023. If you’re in the market for a new boiler – first consider if an air-to-water heat pump system might be a better choice.

Ryan Moag is the Chief Operating Officer of The Radiant Store in Troy, NY.

Margaret Richards is the marketing and communications manager of The Radiant Store.


Note from author:

I’d like to include the pair of images but if we only have room for one I would like to go with the file titled “Air-to-water systems”.

A battery of air-to-water heat pumps provides heats and cools an 18,000 square foot concrete slab of the Basilica Hudson, a popular venue for performances and events in Hudson, NY. The Basilica will meet all of their energy needs this year with clean HVAC technologies powered by an on-site solar-photovoltaic system. (Courtesy photo)

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