Our first hypothesis was that the bubble pump would not function below 100°C. It can be seen from Figure 12 below that while the bubble pump was below 100°C the cool side temperature was rising, but when the bubble pump temperature exceeded 100°C, the cool side temperature began to fall.

Secondly, we wanted to see how cool we could get the cool side of the refrigeration system using the solar collector of limited size. As can be seen from Figure 13, a temperature difference of 20°C between the atmosphere and the cool side was maintained with the bubble pump being at 120°C. It is worth mentioning that all tests were done between 10 am and 2 pm, for optimal solar heating.

Figure 13: Relationship between bubble pump and the cool side temperatures Economic considerations

Preliminary financial calculations showed that if the refrigeration system is to use electricity, it will cost about 17000 QR in the span of the next twenty years (not including the rise of gas prices). On the hand, the solar-operated refrigeration system will incur some initial cost, but this cost will decline to almost zero after all capital is paid for.

Conclusions

The intention of the present work was to study the viability of using solar thermal heat absorption refrigeration technology in Qatar. From the preceding it is established that cooling using solar thermal heat is indeed possible to accomplish in Qatar, but the initial installation costs may currently be prohibitive. It is believed that this could be a viable application, but it is need of further attention and development to reduce installation costs.

Recommendations

As a result of the experience gained during the present experimental work, it is recommended that research in this area continue in the state of Qatar. Specifically, it is recommended that the project be taken to a further level, and a new student be assigned to perform the following tasks.

1. A heat absorption refrigeration system be constructed that is specifically designed to accommodate larger solar panels.

2. Further investigation is done to determine possible cost advantages of building a hybrid compressor/thermal absorption refrigeration system for day/night use.

3. A large scale application be built and tested to determine sizing requirements for typical room sizes in Qatar.

References

[1] Shipman, B. C.; 1936, Air Cooling and Conditioning Apparatus and System, U. S. Patent #2 058 042.

[2] Erickson, Donald C (2007) Extending the Boundaries of Ammonia Absorption Chillers, ASHRAE Journal.

[3] Uli Jakob et al, (2007) Experimental Investigation of Bubble Pump Performance for a Solar Driven 2.5 KW Diffusion Absorption Cooling Machine, Heat Transfer in Components and Systems for Sustainable Energy Technologies, Chambery, France.

[4] David W. Bridger and Diana M. Allen, 2005, “Designing Aquifer Thermal Energy Storage Systems” ASHRAE Journal, Vol. 47, No. 9, September 2005.

[5] Klein, S. A., Reindl, T. D., 2005, “Solar Refrigeration” ASHRAE Journal, Vol. 47, No. 9, September 2005 Acknowledgment

This publication was made possible by a grant from the Qatar National Research Fund. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the Qatar National Research Fund.