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Natural gas heat pumps: The next (r)evolution in natural gas technology

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For several decades, heat pumps have been closely associated with electrical energy. However, the evolution in natural gas technologies and the fight against climate change could help natural gas heat pumps play an increasingly important part in the efficient solutions market.

Toward a low-carbon economy
In 2018, in the wake of the publication of the Pan-Canadian Framework on Clean Growth and Climate Change, Canada and the provinces presented a road map that set ambitious targets for the energy performance of buildings. These targets specifically aim at 100%+ efficiency in space and water heating systems in Canada by 2035. To accomplish this, governments are encouraging the development of natural gas heat pumps for commercial and residential applications.

Collective energy
Given this, some interested parties, including natural gas distributors, drew up their own road map with the objective of offering their customers an efficient and cost-effective solution. In collaboration with manufacturers and research centres, several initiatives were undertaken with the goal of developing a new generation of ultra-efficient natural gas appliances. So where are we now? What are the most promising technologies? That is what we will examine in the following paragraphs.

Vapor compression heat pumps
Most electric heat pumps rely on a vapor compression cycle, usually based on using a refrigerant from the hydrofluorocarbon (HFCs) family. Natural gas heat pumps based on the same principle replace the electric motor by a natural gas motor that drives the compressor. Several manufacturers are today marketing this type of natural gas heat pumps, including Sierra from Mestek, Ilios from Tecogen, Yanmar, as well as M-Trigen. These are mostly destined for the commercial market and some manufacturers also offer models with variable refrigerant flow.

Absorption heat pumps
Absorption heat pumps are probably the best known since their cooling cycle is well understood. First designed to meet the needs of industrial, commercial and institutional customers, today their development targets smaller capacity appliances designed for the residential market and small commercial spaces, offered at a lower cost. These appliances are installed outdoors and most use a mixture of ammonia and water, a refrigerant that does not emit GHGs. Stone Mountain Technologies (SMTI) is currently working on an optimized lower-priced appliance that could be marketed by 2022.

Thermal compression heat pumps
Lastly there are thermal compression heat pumps, a technology under development, even though this type of heat pump is already on the market in France, using CO2 as the refrigerant. In the U.S., Thermolift is in the pre-marketing phase of a thermal compression heat pump using helium, and it has begun a demonstration project in British Columbia with residential and commercial customers.

“Four-season” performance
Unlike electric heat pumps, which need an auxiliary heating system to maintain their capacity in cold weather, natural gas heat pumps can maintain their capacity even in a deep freeze, as Figure 1 shows. Thermolift has published results that show 100% of capacity over a wide range of temperatures and stable efficiency above 130%.

Figure 1
Figure 1

Energy savings along with reduced GHGs
Given their level of performance, high efficiency natural gas heat pumps should generate energy savings of 25-45% compared with condensing natural gas appliances. This technological evolution represents an important milestone and a promising track in the race to reduce GHGs. Also, using renewable natural gas (RNG) to run these heat pumps can enhance the environmental benefits such appliances offer.
Here are some examples of products already available or in development.

Manufacturer

Type

Status

Uses

Sierra (Mestek)

Vapor compression

Marketed

soleil-flocon-goutte_102x40

Yanmar

Vapor compression

Marketed

soleil-flocon_102x40

Illios

Vapor compression

Marketed

soleil-goutte_102x40

Thermolift

Thermal compression

Pre-marketing

soleil-flocon_102x40

boostHeat

Thermal compression

Marketed in Europe
In tests in N. America

soleil_102x40

Robur

Absorption

Marketed

soleil_102x40

SMTI

Absorption

In development

soleil-goutte_102x40

34_2_3_175x75_legende_EN_epr02

Complementary solutions
As well as their advantages in terms of performance and reduced GHGs, natural gas heat pumps are not affected by electricity demand peaks, unlike electric heat pumps that in cold weather may need an auxiliary heating system that also runs on electricity. Just like other natural gas appliances, natural gas heat pumps – all technologies taken together – is a complementary solution to managing electricity peaks.
Also, combining natural gas and electricity solutions, i.e. using the right energy at the right place at the right time and at the best cost, means increased resilience – a tremendous asset in the fight against climate change.

In conclusion
Natural gas heat pumps link performance and efficiency with environmental benefits – and the marketing outlook is promising. Keenly interested in this technology, Énergir is working on developing and marketing it in collaboration with other natural gas distributors and manufacturers. It fits in well with our aim to propose innovative solutions to our customers to help them remain competitive while reducing their energy consumption and their GHG emissions at the same time.

Natural gas and energy efficiency: A little history

The energy efficiency of natural gas appliances, such as the warm air furnace and hot water boiler, have been improved over the years as a result of various influences: the oil crisis of the ’70s, the fluctuations in the cost of energy in the 2000s, and the environmental concerns omnipresent today.

This efficiency has currently reached more than 90%. To get here, different materials and configurations had to be developed to be able to recover latent energy from combustion products. During the 1990s, condensing appliances (efficiency > 90%) made their appearance. First seen as marginal and not very cost-effective, given the competitive situation of natural gas, they have become much more affordable since the early 2000s because of the fluctuations in energy prices and the creation of energy efficiency programs that have made their acquisition easier.

Recent regulatory changes impose a minimum performance of 92%, which will soon rise to 95%. The increase in the level of efficiency of condensing appliances is now measured in percentage points and has reached a maximum of 99%, due to improvements in both controls and heat exchangers.

To reach the next level, i.e. 100% and over, technological improvements must now build on new fundamentals, like those used in heat pumps.

Marc Francoeur, Eng. CEM, LEED PA
Chief Advisor, Technology Development
Commercialization & Technology Intelligence

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