Aqua Ammonia Explained

Last month, I read an article on Ammonia 21 on how a curling rink in Canada has been equipped with North America’s first aqua ammonia refrigeration system. I reached out to Art Sutherland, the President of Accent Refrigeration, the designer of this low-charge, green system, to find out more.

Accent Refrigeration is renowned as a first class ice arena designer, manufacturer and installer, focusing on affordable, high-efficiency refrigeration solutions for their customers. For three decades they’ve been involved with projects as diverse as small town rinks to the world stage of the Winter Olympics and Sutherland is continually pushing his team to improve and innovate – especially in the quest for safe, natural refrigerants and smarter, more efficient ice arenas. Accent has dabbled in CO2 arenas (South Africa and Alaska) — but this aqua ammonia project seems to have taken the complex task of refrigeration, heat reclaim and safety to a completely higher level of efficiency and sustainability.

Sutherland, who is “running a hundred miles an hour this year” (as you can imagine) found some time to send me some information on the project for the Chilliwack Curling Club in Chilliwack, BC. The new building, with eight curling sheets on 23,000 square feet of refrigerated floor, opened in November, 2018, replacing a 6-sheet facility which the Club built in 1954. The Club has 650 active members and 1,500 shareholders, and has been in operation since 1952.

In a nutshell, what Accent designed is a split-header, ultra-low charge indirect refrigeration system (2×50 lbs. of ammonia) as the primary refrigerant, using aqua ammonia (ammonium hydroxide) – a water solution consisting of 12% ammonia – as the secondary refrigerant. Although this technology is new to North America, it’s been used for over 10 years in Asia and Europe. Here’s how it’s working at the Chilliwack Curling Club:

Split-header

Let’s start with the split header.

The split refrigeration header design is a configuration that offers some significant lifetime and cost advantages. The split design means there are two chillers, two condensers, two compressors, and two pumps which provides 100% redundancy if there is a failure of any of the components. By distributing the ammonia charge between two chillers, the split header design avoids the mandatory staffing requirements a common header system would require. The condensers act as 100% energy recovery heat exchangers, used for heat throughout the facility. Finally, there are very short, all-welded piping runs between the chiller, compressors, and condensers, minimizing any chance of leaks.

Using the non-corrosive aqua ammonia as the secondary coolant also has advantages. To put it into perspective, the 12% solution is slightly stronger than the all-purpose cleaner (10%) you would buy at your local hardware store. Equally impressive is the viscosity of the aqua ammonia: since it’s lower than brine or glycol, less horsepower is needed from the pumps. And it’s cheap — a fraction of the cost of ethelyne glycol.

Chilliwack Curling Club’s facility manager, Bruce Renwick, was quoted in The Progress:

“At the old building we ran a 15 horsepower brine pump, and here, with 40 percent more floor space we’ll run six horsepower.”

Bruce Renwick, Facility Manager, Chilliwack Curling Club

Using aqua ammonia as the secondary also makes a difference to how the piping grid for the refrigerated floor is constructed. Instead of using low density polyethylene pipe (LDPE) secured by clamps, this floor uses fusion-welded High Density Polyethelene (HDPE) pipe which is practically indestructible. Sutherland says these pipes will “last the life of the building — without any leaks.”

The Chillers

The Finnish-made Vahterus chillers are high-efficient. Their sealed plate and shell design operate at very close approach temperatures to keep the suction pressure and efficiency at the highest possible levels. Each chiller has an inspection port, eliminating the cost of disassembling for inspection (as shell and tube heat exchangers require). And they’re gasket-free, eliminating the cost of gasket replacement that a plate and frame would require.

The floating plate stack is constructed like an accordion and is not affected by freezing, another significant advantage. When combined with aqua ammonia, long-term corrosion poses much less of a problem in comparison to traditional chillers.

Small and Safe

The compact size of the chillers and the low charge of the ammonia are huge benefits, according to Sutherland. “Since the chillers are smaller than a half the size of an oil drum, physical space is not an issue,” Sutherland says. “But best of all, the refrigerant charge is less than 50 pounds. In the unlikely event that the chiller ever leaked the entire ammonia charge into the secondary side, it would increase the aqua-ammonia concentration by less than a quarter of a percent, which would not require any expensive remediation whatsoever. “

In the unlikely event that the chiller ever leaked the entire ammonia charge into the secondary side, it would increase the aqua-ammonia concentration by less than a quarter of a percent, which would not require any expensive remediation whatsoever.

Art Sutherland, Accent Refrigeration

The Pumps

The low viscosity of the aqua ammonia combined with a low chiller pressure drop and the reverse return header design all translates into a secondary pump with a very small, 3 HP motor. That’s less than a third the 9.5 horsepower required for ethelene glycol. These smaller pumps will make a huge difference to the club’s energy spend, a projected savings of 5000 less kilowatt hours per month in comparison to a traditional system.

The Condensers

The system uses close approach, fluid-cooled plate-style condensers mounted within feet of the compressors. The type and location of the condensers result in many advantages. First, the refrigerant charge is less than 1/10^th of that needed for an evaporative condenser. Next, the short piping run reduces the ammonia piping by 90% and the all-welded construction eliminates leaks.

These condensers serve a double duty in that they provide 100% energy recovery with no need for a dedicated heat recovery condenser. Condensing temperatures can be maintained at 76°F while providing fluid temperatures of 70°F to heat the curling club ice house instead of fossil fuels.

The Compressors

As for compressors, Accent chose the Mycom 2M reciprocating compressors from Mayakawa which Sutherland says are the most efficient in the refrigeration industry. When combined with the close approach chillers and condensers, the result is phenomenal energy efficiency in comparison with any system used today. Operating at a low speed of 700 RPM with the very favorable compression ratios provided by the high-efficient condensers and evaporators, the compressors will provide many years of maintenance-free service.

Heat Recovery

The Munters Desiccant Dehumidifier also functions as the ice house’s heating system through the harvesting of waste heat from the ice plant. According to Sutherland, when there is an opportunity to use low grade heat, an ammonia system operating at low condensing temperatures is far more efficient than any other refrigeration system used in the industry today.

“A curling club provides an ideal opportunity to use low grade heat for keeping the ice house warm and comfortable for the curlers,” Sutherland says. “The refrigeration system can operate at a very efficient 75°F condensing temperature, while providing a heating fluid of 72°F and a supply air temperature to the curling club of 65°F.”

Improved System Safety

In addition to the drastically reduced refrigerant charge and the split system design, there are several safety features with this system that have not been commonly implemented in the past. Rather than having an open balance tank venting into the room, the system utilizes a pressurization tank which maintains a very small, 3 psi pressure on the inlet of the pump. The secondary side of the system is protected with pressure relief valves so in the unlikely event of an over-pressurization on either the primary or secondary sides, the pressure is safely relieved away from operator or public exposure.

Improved System Performance

The total system performance is realized at the design stage through optimizing the balance of the components into a harmonized system that is extremely efficient. When the chiller and condenser are selected for very close approach temperatures and combined with a slow operating Mycom M compressor, the refrigeration Coefficient of Performance (COP) is elevated to a phenomenal 6.2 (one watt of electricity consumed to do 6.2 watts of refrigeration). This is double the electrical efficiency of systems of 10 years ago and 50% better than leading CO₂ and synthetic refrigeration systems. When the low grade heat is used to warm the ice house, the total COP increases to 13.4.

The outcome is a system that makes great ice with an exceptional level of electrical efficiency, thermal efficiency, reliability, redundancy, and the highest level of safety obtainable.

Chilliwack Curling Club’s facility manager, Bruce Renwick (above) says that he is more than excited to have a plant that is using cutting edge technologies and a super-green brine not used in North America before.

“The curlers are loving the ice and the sheets are booked solid through to spring,” says Renwick.

More Info

For more information, you can download Accent Refrigeration’s brochure (Accent Refrigeration – Chilliwack Curling Club First To Use Aqua Ammonia) here. Or you can contact Art Sutherland at +1-250-478-8885.