Users in this sector include chemical, pharmaceutical and oil and gas
companies.
Users in this sector include chemical, pharmaceutical and oil and gas
companies.
Ammonia has been the refrigerant of choice in this sector for many years
before the CFC restrictions came into force. The vast majority of US
cold stores and over two thirds in Germany are already using ammonia .
The technical feasibility and commercial availability of ammonia is well
demonstrated. Almost all of Nestle's systems worldwide are now running
on ammonia. Unilever has made a complete switch to ammonia, as has Ciba
Geigy in Switzerland.
Approximately 50 per cent of HFC-134a production is for automotive air
conditioning, 15 per cent for domestic refrigeration, and most of the
remaining 35 per cent for commercial and residential air conditioning
and supermarket refrigeration.
Car air conditioning systems require a relatively large volume of
refrigerant charge, and since the systems regularly leak, they need
constant recharging. Approximately "65per cent of the cooling agent in
mobile air conditioning leaks away unavoidably." * Refrigerant loss in
a typical car air-conditioning unit occurs within two to five years, and
on average, when a car is brought in to a garage for A/C service, only
about 40 per cent of the original 2kg charge is left. ** This
guarantees on-going business for the refrigerant suppliers. Little
wonder that the chemical industry views the possibility of an
alternative technology penetrating the mobile air-conditioning market
with a great degree of trepidation.
A major obstacle to environmentally safer technologies penetrating the
automobile air conditioning market is that during the past few years
many of the major car manufacturers have already invested into
converting to HFC-134a . Clearly, from an environmental perspective,
this has been a bad decision, which needs to be quickly rectified by
these companies switching to safer technologies.
Mobile hydrocarbon air conditioning is feasible, and has been used in
the UK, US and Australia. The technical requirements of mobile air
conditioning are slightly different from that for static systems.
Different compressor and flexibility of piping is required.
Nevertheless, with established refrigerants like ammonia and
hydrocarbons the technical problems are less of a barrier to the
development of safer alternatives then are the regulatory measures,
insurance and safety concerns, and consumer acceptability.
There are a number of advantages to hydrocarbons in mobile
air-conditioning. It is significantly (75per cent) cheaper to change
over from CFCs to propane/butane than changing to HFC 134a. $50.00 per
vehicle with hydrocarbons, compared to $200 with HFC 134a. The amount
of refrigerant charge using hydrocarbons is less than half required with
CFCs and HFCs. Hydrocarbons increase the cooling capacity of the system
by about 10 per cent and have fewer toxic combustion products than
CFC-12 and HFC-134a.
Calor Gas has recently completed a risk assessment using their
hydrocarbon (CARE) products in mobile-airconditioning, and is presently
conducting field-tests.
Researchers at Sintef Refrigeration Engineering, the Norwegian Institute
of Technology have successfully tested a Mobile Air Conditioner (MAC)
using CO2 as the refrigerant.
There are also alternatives to vapour compression cooling. Zeotech , a
company based in Munich, has already installed an air conditioning
system on German Railways using a zeolite/water adsorption cycle.
Zeotech hopes to have a system for buses and lorries on the road soon.
A US company Climatran, has installed a system in over 500 buses which
uses an evaporative cooling technology - cooling the air by evaporation
of water.
** Makhijani and Gurney, 1992 [return]