Have you ever been woken at in the middle of the night after a long flight by the hotel mini bar? I have and I’m sure I’m not alone. These older compressor type mini bars have been around for many years but now there is a better way for hotels to conserve energy as well as give their guests a good night’s sleep.

Absorption mini bars are now becoming the industry standard but how do work and also how do they compare to the traditional compressor mini bar?

Compressor advantages:

• Normally cheaper than absorption mini bars.

• Many brands available.

Compressor disadvantages:

• The obvious one is noise. Some hotels with small rooms have reported this as their number one guest complaint.

• There are more moving parts that can wear faster reducing the mini bar’s life as well as increasing service and maintenance costs.

• Some models have to be manually defrosted that increases hotel labour costs.

• Vibration, which can cause operational problems as well as noise.

Absorption advantages:

• Silent operation.

• Long life due to low quantity of moving parts inside.

• No vibration to increase noise and wear and tear.

• More options to upgrade some brands for hotel specific purposes such as automatic billing.

• Automatic defrost a standard option.

• In summary, with an absorption mini bar you install it and forget it.

Absorption disadvantages

• Slightly more expensive than compressor type.

• Must have adequate ventilation.

• Not as many brands to choose from as compressor mini bars.

• Size 60-70l is the maximum at the moment.

So how does an absorption mini bar work?

Before beginning we need to understand there are four basic parts to an absorption mini bar. These are the reservoir absorber, the boiler pump, the condenser and the evaporator (chiller). The system works with a solution made of water, ammonia and hydrogen.

The boiler pump electrically heats up and boils the water with a high concentration of ammonia that comes from the reservoir and that releases the ammonia now in a form of gas.

The ammonia gas rises to the upper part of the system, called the condenser, where with the help of the cooling fins, it causes the temperature to drop thus condensing only the ammonia from gas to a liquid form. This liquid and highly pure ammonia is then moved to the evaporator where it meets with hydrogen at different pressure, causing the ammonia to evaporate again. It is a physical phenomenon that every time we have an evaporation there is temperature absorption.

In other words, the process pulls the heat from the surrounding area, consequently cooling the evaporator to a degree that frost is formed in the outer part of it and the temperature in the inside of the mini bar is lowered.

The evaporated ammonia, together with the hydrogen, then travels to the absorber where we have fairly pure water that, once it encounters the evaporated ammonia gas, it absorbs it. This process is what gives the system its name, since here water is absorbing ammonia. By gravity this water-ammonia solution travels through the absorber coil, absorbing as much ammonia as possible, ending at the reservoir. Once in the reservoir, the water with a high content of ammonia passes again to the boiler pump, where a new cycle then restarts.

Because of the system described above and the low quantity of moving parts these fridges can last 15-30 years at least, easily outlasting the compressor type.

Due to the cost of the fitting out an entire hotel as well as the fact it is fairly new technology it is recommended to stick with the proven brands that have long-term support as well as experience. They can advise the hotel on how to install the mini bars, as ventilation is an important consideration.

Finally there is no doubt absorption mini bars will benefit both hotel guests and staff due to silent operation, low maintenance requirements and no manual defrosting. To sum up the extra expense initially will save the hotel in the long run.

Simon Bassett - Business development manager, VingCard Elsafe