Substitutes for Potent Greenhouse Gases

Appendix A: List over refrigerants and refrigerant mixtures

In the below table the most common refrigerants, consisting of single substances, are stated:

From below mentioned table various refrigeration mixtures in the 400-serie (zeotropic mixtures) appear. Calculation of the ODP and GWP values is possible according to the values in the table for single substances, as the ratio of mixture according to single substances is weighted.

Refrigeration mixtures in the 500 serie (azeotropic mixtures) appear from the following table:

Appendix B: Commercial refrigeration systems

The commercial refrigeration systems installed in retail stores, supermarkets, restaurants, computer centres etc. account for the most important economic area within the refrigeration industry. In addition, the widest range of applications lies within this area. On this background various conditions like prices, energy consumption, refrigerant leakage and the TEWI value (Total Equivalent Warming Impact) will be elucidated in this appendix.

In chapter B.1 a price comparison between liquid chillers using R-404A, hydrocarbons and ammonia is made, whereas conditions like energy consumption, refrigerant leakage and the TEWI value for supermarkets systems are addressed in chapter B.2. In chapter B.3 detailed price differences between a traditional refrigeration system and a similar refrigeration system using hydrocarbon refrigerant are shown.

B1. Comparison of prices between ammonia, hydrocarbon and HFC refrigeration systems (liquid chillers)

The comparison will be based on liquid coolers (chillers) and on this background price differences and the reason for such will be analysed. An estimate of how prices are expected to develop in the future is given.

Today HFC and ammonia refrigeration systems are produced in large quantities. Basically, the HFC refrigeration systems use the same technology as CFC and HCFC refrigeration systems, and ammonia refrigeration systems have been produced for more than 100 years. Recently, ammonia has been replaced by artificial refrigerants, however application of ammonia is rapidly in progress within the field of large liquid coolers, air conditioning etc.

Compared to this, the use of hydrocarbons is relatively new within the area of commercial refrigeration systems. Some of these are produced in Sweden and Germany, where quite a number of refrigeration systems operating on propane or propene has been installed. These systems are produced in small quantities and compared to HFC refrigeration systems prices continue to be relatively high. A rapid improvement of competitiveness could be possible.

Haukås
A report for SFT, Norway (Report 97:32, SFT) has been prepared by Hans T. Haukås. This report includes prices on various types of refrigeration systems.

According to Haukås the following prices for systems over 10 kW are to be taken into consideration:

- a 12.5% price increase for refrigeration systems using HFC-134a compared to systems using R-404 or R-507

- a 10-40% price increase for liquid cooling aggregates using ammonia or hydrocarbons compared to systems using R-404A or R-507

- application of ammonia or hydrocarbon requires a certain extra charge for machine room safety

According to Haukås, the figures should be regarded as guides and some examples deviate on both sides of the scale. As far as large refrigeration systems are concerned, application of ammonia will be directly competitive. No investigation has been carried out as far as application of hydrocarbons is concerned.

Grødem
In the trade magazine ScanRef (Scandinavian Refrigeration 3/98) Bjørn Grødem, also from Norway, states that the above price differences are somewhat lower. Grødem=s statement is based on German investigations of refrigeration systems for supermarkets, where comparisons between indirect cooling with R-404A, ammonia and hydrocarbons have been made. Prices have been compared with a direct R-404A refrigeration system as well.

Table B.1: Price comparison between different types of supermarket systems. According to Grødem, ScanRef 3/98. Index 100 is the value for direct cooling with R-404A.

As can be seen in table B.1, direct refrigeration systems are the most competitive. In addition, only a limited price difference between the indirect systems appears. In particular, only a small price difference (a minor percentage of the total costs of system) appears when comparing the R-404A and the hydrocarbon system.

Estimation of prices for hydrocarbon refrigeration systems
In co-operation with Alexander C. Pachai, AirCon A/S, Denmark, DTI Energy has made an analysis of future prices for hydrocarbon systems compared with a similar HFC refrigeration system.

The analysis assumes a large-scale production of the hydrocarbons systems similar to the present production of HFC refrigeration systems, thus achieving large-scale production benefits. The analysis also assumes that authorities have issued explicit guidelines on the building of hydrocarbon systems and that fitters have been properly trained in handling hydrocarbons. These requirements prevail in Sweden, where the company Bonus Energy AB builds hydrocarbon refrigeration systems, but not in other Nordic countries.

Components
Most of the components used in a hydrocarbon system are similar to the ones used in an HFC refrigeration system, and thus the price level will be identical. However, a certain price difference prevails for automatic controls. Application of explosion-safe components like differential pressure controllers, thermostats, terminal boxes, relays and ventilators, registered in the IP 44 safety category, is demanded. In Denmark the IP 23 safety category is normally used for commercial refrigeration systems, but this category is not sufficient for use of hydrocarbons. An example of a 14 kW refrigeration system is shown in chapter B.3, where the prices of component are shown as well. From this example a 4.3% price difference occurs, however this difference will be reduced for large systems.

Assembling
In hydrocarbon systems all joints and connections must be soldered. HFC refrigeration systems may be connected either by means of soldering or by use of screw fittings. Although the soldering process will require more working hours, this is expected to be equalised by decreased material consumption (i.e. screw fittings). Additional costs are expected in the range of 0 - 1%. The time used for leak detection is similar to that used for an HFC refrigeration system.

Safety
In the case of indoor machine room installation of the refrigeration system, the presence of a gas alarm at ground level is required. In case of outdoor or semi-roof installation, this precaution may not be necessary. The same requirements are valid for an HFC refrigeration system, which ought also to include a refrigerant leakage detector. The price for a gas alarm and the associated ventilator amounts to approximately DKK 6000 (list price).

Education
To secure that fitters are duly skilled for proper handling of hydrocarbons, establishment of a training system is required. Until now this is only the case in Sweden.

Equipment
For proper hydrocarbon handling, the assembling company needs suitable equipment.
The price of a hydrocarbon leak detector is almost similar to the one required for artificial refrigerants, e.g. HFC, which is also the case with a hydrocarbon charging aggregate. In addition, an explosion-safe vacuum pump is required, the price of which will be approximately 50% higher than the price of a traditional pump (list price is approximately DKK 7150).

For some time, the Danish transport requirements for pressure bottles containing hydrocarbon refrigerant have been the cause of confusion. According to previous advice issued by the Danish Society for Gas Technology, gas bottles should be placed in safety rooms in the service cars. Consequently, the requirements will differ from those of other gas bottles, e.g. acetylene for welding and soldering processes. At the moment, DTI Energy is investigating these requirements.

Conclusion
It has been concluded that the price of hydrocarbon systems is somewhat higher than that of similar HFC refrigeration systems. The price difference ranges between 10-40%, however, nothing will prevent a significant decrease of this in the future. Compared to a HFC refrigeration system, components for a 14 kW output hydrocarbon system are about 5% more expensive. In addition, due to the assembling process a 1% price increase will appear, including a possible additional charge for detector installation. However, use of detector is also recommended for HFC refrigeration systems.

Supermarket hydrocarbon refrigeration must be carried out by means of indirect cooling. Thus, the difference from an HFC refrigeration with direct system systems becomes more significant.

Estimation of future prices for ammonia refrigeration systems
Today ammonia refrigeration systems are competitive when taking systems larger than 100 kW into consideration. However, this is not yet the case with small and medium sized refrigeration systems, a fact, which can be changed. Not until recently has the use of ammonia in small and medium sized refrigeration systems been in focus and the number of available compressors is increasing.

However, the price level of these continues to be higher compared to prices of similar compressors for HFC refrigerants, but it is likely to believe that price equalisation will be generated by means of production of larger quantities. Furthermore, as far as pipe systems are concerned, new assembling methods are being developed to obtain lockring or fittings as an alternative to soldering.

B.2 Energy consumption and TEWI for commercial refrigeration systems based on supermarket refrigeration systems

From January 1994 the assembling of new commercial refrigeration systems using CFC refrigerant (CFC-12, R-502 etc.) was prohibited in Denmark. In new refrigeration systems the use of HCFC will be prohibited from January 2000. From January 2002 this will include application of new HCFC for service purposes as well.

Hence, HFC based refrigerants including HFC-134a, R-404A or possibly R-407 are used in most of the new supermarket cooling cabinets and other commercial refrigeration systems.

Direct cooling is used in supermarkets in Denmark and Norway, whereas the use of indirect cooling is becoming more frequent in Sweden, Germany and other countries. In Sweden new supermarket refrigeration systems must be provided with indirect cooling. According to the Swedish Refrigeration Standard, a partly indirect refrigeration system is required for filling charges between 10 and 30 kg. Traditionally, an indirect system will be used for cooling and a direct system will be used for freezing.

Filling charges over 30 kg require a completely indirect system, i.e. indirect systems for both cooling and freezing.

For direct supermarket cooling, liquid refrigerant will flow in long pipe systems to the cooling places, e.g. cooling or freezing storage, milk cooling cabinets, cold stores etc. Afterwards the evaporated refrigerant is led back in other pipe systems. In a medium sized supermarket, with cooling required at 30-40 different locations, there are often kilometres of refrigerant pipes and hundreds of pipe connections.
A certain amount of leakage is almost impossible to avoid in these pipe systems. Leakage will often occur in valve gaskets and connections, or by direct accident caused by broken pipes. Previously, the assumed leakage rate of these systems amounted to 20-30% of the annual filling charge.

Great efforts have been made within the trade to improve the quality of new systems, and hence a considerable reduction of the leakage rate is assumed. IPCC's guidelines from 1996 state an annual average leakage rate of 17%. However, a 100% tightness of the systems is not technically possible. The exact figures are not known, however an annual 10% leakage rate for supermarket systems with direct cooling is assumed.

It is less expensive to produce a refrigeration system with direct cooling than a similar system using indirect cooling. According to Haukås the price is 20% higher, whereas Grødem mentions a 15-20% price increase of the indirect system.

This price difference is due to the slightly higher prices for pipe systems. Investment in circulation pumps for the secondary refrigerant is necessary. In addition, investment in additional heat exchangers between the primary and secondary system is required.

On the other hand a considerably smaller amount of refrigerant is required (often 15-20% depending on the amount in a direct system) and the leakage rate will be much less, often only 5%.

Energy consumption
The precise energy consumption in the various systems is hard to predict, as it depends on the retrofitting rate of the individual systems. However, Bjørn Grødem has tried to estimate some figures in ScanRef 3/98, which are as follows:

Table B.2: Energy consumption for different supermarket refrigeration systems. The source is similar to that used in table B.1. However, it should be emphasised that this example is not necessarily valid for all systems.

The energy consumption is slightly higher for the indirect systems due to the thermodynamic loss from temperature differences in the heat exchanger between the primary and secondary refrigeration system and the pumps' energy consumption. This will to some extent be balanced by improved efficiency of the hydrocarbon and the ammonia refrigeration system.

It is estimated that the design of hydrocarbon refrigeration systems soon will result in energy consumption for indirect systems, which does not exceed the consumption for direct systems. Use of components (compressors), which have been optimised according to the refrigerant, is required. Previously, R-22 components for propane or propene have been used. Through this optimisation the difference between direct HFC systems and indirect hydrocarbon systems will be significantly less.

New secondary refrigerants will be available on the market in the future, including ice slurry for refrigeration purposes and CO2 for freezing purposes. Hence, in comparison with direct HFC systems an improvement of the energy consumption used for indirect systems using ammonia or hydrocarbons is expected.



Contribution to the green house effect, TEWI
Refrigeration systems contribute both directly and indirectly to the green house effect. Direct contribution is caused by leak of refrigerant, e.g. R-404A, which has a GWP (Global Warming Potential) of 3260, compared to CO2, which has a GWP of 1.

The indirect contribution derives from electricity consumption. If electricity is generated at coal fired power plants, as is the case in Denmark, the CO2 emission from the power plant's stack corresponds to 0.8 kg of CO2 per kWh of electricity.

The TEWI value (Total Equivalent Warming Impact) combines both direct and indirect contributions, i.e.:

TEWI = GWP * M + ALFA * E

where

GWP is the GWP factor of the refrigerant;
M is the amount of refrigerant, leaking from the refrigeration system;
ALFA is the amount of CO2, which is generated during electricity production (kg of CO2 per kWh);
E is the electricity consumption of the refrigeration system.

Example
An example of a typical supermarket refrigeration system is given below. The example, which is typical for countries with direct cooling as standard, comprises a medium sized supermarket (e.g. Danish supermarket such as >Kvickly=, >Føtex=) with a sales area of 1000-1500 m2.
The total refrigeration efficiency is 100 kW and the system is provided with direct cooling. The refrigerant charge is 300 kg of R-404A.

The annual energy consumption of the refrigeration system is 170,000 kWh, whereas the leakage rate is 10% of the annual charge, i.e. 30 kg.

TEWI calculation stating yearly operation of the refrigeration system:
Direct yearly contribution to the green house effect:
M * GWP = 30 kg of R-404A * 3260 (kg of CO2/kg of R-404A) = 97800 kg of CO2 = 97.8 tonnes of CO2.

Indirect contribution to the green house effect: ALFA * E = ALFA * 170,000 kWh.

Table B.3: Contribution to the green house effect for the refrigeration system stated in the example. This example is for direct cooling with R-404A.

According to the example the 100% coal-fired power station accounts for the direct contribution to the green house effect (approximately 42% of the total TEWI contribution).

In the example with 50% coal and 50% hydroelectric power supply the share accounts for 59%. According to the example the share of hydroelectric power supply accounts for 100%. It should be mentioned that other environmentally related problems occur in connection with hydroelectric and nuclear power. In this example only the green house effect is included.

It has often been said that the refrigerant share of the TEWI value is very limited. However, this does not seem to be the case with supermarket refrigeration systems using R-404A and direct cooling. The refrigerant accounts for a considerable share of the total impact of the green house effect.

When using a hydrocarbon or an ammonia refrigeration system in the same supermarket, a considerably lower green house impact will be achieved, despite the small increase of energy consumption shown in the following table.

Table B.4: The TEWI value for a supermarket refrigeration system using propane and indirect cooling, c.f. table B.3. It should be mentioned that calculations are only related to the contribution to the green house effect. This example may not necessarily be representative for other commercial refrigeration systems.

According to the values shown in table B.4 the total impact of the green house effect is far lower for a hydrocarbon or ammonia refrigeration system using indirect cooling than for an R-404 refrigeration system using direct cooling. The result is independent of electricity production methods.

B.3 Differences in traditional and in hydrocarbon refrigeration systems

In this chapter the price differences between components for HFC and hydrocarbons systems are described.

Components in a traditional refrigeration system
The design of a traditional refrigeration system is often very simple. In many cases a thermostat equipped with an on/off signal is used. If the system is provided with an air-cooled condenser, application of a differential pressure controller to obtain suitable condensing pressure during cold intervals is frequently used.

Most of the components that can ignite a spark are categorised under the protection classification IP 23 or the like, which also implies fans. In many cases the terminal box of the compressor, which contains the starting relay or other relays than can cause a spark, are included as well. In Denmark no rules concerning the application of twin diaphragm differential pressure control for chemical refrigerants prevail. As a consequence, these are not commonly used, although their application may reduce emission of potent green house gases. This is also the explanation of their extent of use in Germany.

Price differences between IP 23 and IP 44 or above
In connection with hydrocarbon refrigeration systems it is required as a minimum that equipment is categorised under the safety classification of at least IP 44 or even above. IP 54 and IP 55 are becoming a standard, wherefore products of this class are normally easily obtained.

The definition of safety classification requires some knowledge about the relevant nomenclature. Briefly, on a scale from 0 to 6 the first number indicates dust-proofness. The second number indicates water-proofness also on a scale from 0 to 6. Thus, an apparatus categorised under IP 23 is not quite dustproof and will only tolerate water spray, whereas an apparatus under IP 66 remains tight when exposed to water through a certain period and depth. Further details concerning this matter is described in an European standard.

Considering the system mentioned in the example, prices are indicated in the following table for a system provided with a suitable casing and improved level of safety.
Table B.5: Comparison between components for a traditional HFC refrigeration systems and similar hydrocarbon systems. The refrigeration performance is app. 14 kW.

According to the example, a slight price difference appears for the entire system.

Whereas the price of some components in the high protection class is more than twice as much as the others, the most expensive components in the system are not more expensive, thus eliminating to some degree the price difference. The same type of components is used despite the size of system. Should the price of compressor, condenser and evaporator be more than doubled, the additional price for the subcomponents will be insignificant compared to the total price. According to the example, only a 5% price difference for the components alone is registered.

However, it should be emphasised that apart from Sweden the end-users in the Nordic countries may choose between an HFC refrigeration system with direct cooling and a hydrocarbon using indirect cooling. In this case the price difference will be higher, see table B.1.

As Swedish systems traditionally use indirect cooling. a lower price difference will be registered in this case.

Appendix C: Sabroe Chillers with NH3 refrigerant, installed in Denmark 1990-1998

Appendix D: Gram Chillers (York International) with NH3 refrigerant, installed in Denmark 1992-1998

Appendix E: Bonus Chillers with Hydrocarbon-refrigerant, installed in Sweden 1996-1998