02 Ammonia – A Natural Refrigerant

eurammon-Information No. 2 / Updated version, May 2011
 

Ammonia – A Natural Refrigerant
Environmentally friendly, economically efficient
Our developed society depends on industrially produced refrigeration. Whether at home, in
the production and storage of foodstuffs like frozen foods, yogurt and coffee, as part of
industrial production processes in the automotive and chemicals/pharmaceuticals industry,
or in air-conditioning systems – refrigeration is a central element everywhere. Industrially
produced refrigeration is what makes a modern lifestyle possible. And natural refrigerants
such as ammonia, carbon dioxide and hydrocarbons are an integral element in refrigeration.
Natural refrigerants have been used to produce cold energy – mainly in food production and
storage – since the mid-19th century. Ammonia (NH3) in particular has proven its worth in
industrial refrigeration for over 120 years. Although “safety refrigerants“ – such as the now
illegal CFCs – were increasingly used in plants built in the 1950s and ‘60s, ammonia has
always managed to prevail in industrial refrigeration technology. Due in great part to the
environmental debate surrounding ozone depletion and global warming, ammonia’s share in
the market for refrigeration technology is on the rise again, and companies of long-standing
tradition and experience prefer to work with ammonia.
 

Compelling Characteristics
Ammonia is a colourless gas that liquefies under pressure and has a pungent odour. In
refrigeration technology, ammonia is known as R 717 (R = Refrigerant). Although it is
synthetically produced for use in refrigeration, ammonia is considered a natural refrigerant
because it occurs in nature’s material cycles. Ammonia has no ozone depletion potential
(ODP = 0) and no direct greenhouse effect (GWP = 0). Its indirect greenhouse effect
contribution is also very limited due to its high energy efficiency. Ammonia is combustible
only to a limited degree; its ignition energy is 50 times higher than that of natural gas and
ammonia will not burn without a supporting flame. Due to the high affinity of ammonia for
atmospheric humidity it is rated as “hardly flammable”. Ammonia is toxic, but has a
characteristic, sharp odour with a high warning effect. It becomes noticeable in the air at
concentrations of just 3 mg/m³ ammonia. This means that ammonia becomes evident at
levels far below those which endanger health (> 1,750 mg/m³). Ammonia is lighter than air
and therefore rises quickly.
eurammon-Information No. 2 / Updated version, May 2011
Ammonia is also an ideal refrigerant from a climate protection point of view, as it contributes
neither to ozone depletion nor to global warming. Of all known refrigerants, ammonia
requires the lowest primary energy input to create a given refrigerating capacity, thanks to its
excellent thermodynamic properties. This means that its indirect global warming potential is
also very low. Thus, plants that use ammonia as opposed to other refrigerants have a better
TEWI (Total Equivalent Warming Impact). The TEWI is the sum of the direct global warming
impact – caused by the refrigerant lost through leakage and recovery – and the indirect
global warming impact, in relation to the energy used over the life of the plant.
Ammonia is sustainable not just from an ecological, but also from an economic point of view.
Unlike synthetic refrigerants, it is an inexpensive feedstock. The difference in price becomes
evident when initially charging a plant, but also and especially when topping off leakage
losses. Experts assume annual losses of between 2 and 17 percent for ramified industrial
refrigeration plants, depending on a plant’s age and condition.[1] In addition to their high
cash costs – for instance, the HFC refrigerant R 404A is much more expensive than
ammonia – the HFC leakage naturally also puts a considerable strain on our climate.
 

Energy Savings with Ammonia
Plants that use ammonia also have an edge when it comes to overhead or running costs.[2]
Beyond the lower cost from leakages, reasons include lower maintenance expenses and –
especially for industrial plants – reduced energy consumption. Ammonia is one of the most
efficient refrigerants around, resulting in low energy costs. And finally, there’s the
inexpensive disposal when a plant has reached the end of its life.
Ammonia’s virtues as a refrigerant have opened up whole new fields of application. In light of
carbon dioxide emissions trading, which forces operators to curb their energy use, many
operators are choosing ammonia refrigeration plants. Today, ammonia is used in such
widely different fields as process refrigeration, air-conditioning in airports, office buildings
and production halls, and sports and recreation facilities. Indirect refrigeration systems and
cascades, e.g. using carbon dioxide as the low-temperature refrigerant, now prevail in plant
design. The advantage: ammonia charges are kept low, and the refrigerant output is
delivered to the consumer loads via coolants like carbon dioxide and glycol water.
eurammon-Information No. 2 / Updated version, May 2011

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Properties of Ammonia