Thermal Energy Demands in Dairy Farms – Bolivia
The global trend that promotes the reduction of the harm emissions it is related to the management of the energy systems in terms of their efficiencies, more efficient system fewer fuel consumption and for instance fewer emissions to the atmosphere. Most of the conventional systems for refrigeration, like the compression system, have been developed during the last years achieving better efficiencies, however the system itself reached at one point where the improvement of the system is more difficult, most of these systems require electricity as an energy source, electricity access is other problem that does not permit to have the conventional compression system working continuously in warm, isolated areas. These reasons promote the search for other alternatives.
CCHP systems becomes an interesting option to meet numerous energy demands, the same system can provide electricity and heat, from them can be obtained cooling, heating, and other services as well. When an Externally Fired Microturbine is used as a driver of the system the advantages increase because of its capability to work with a large amount of fuels, liquids and gasses, these can be used in the atmospheric combustion process, asides of the Thermo-Solar energy. This system is able to operate independent of the grid saving energy. When the CCHP system provide more than three services it can be called a Polygeneration system, this system can be greatly applied in isolated villages where the grid access is difficult to reach because the large distances from the electric grids, for instance the lack of many services is present. Decentralized Power Systems (DPS) are an interesting option in these cases; it means to generate energy in the same place of consumption using the energy sources available and accessible, the application of DPS is not limited just for that, they can also be used in places where exist electric grid but the cost is expensive and/or the reliability is low, this installation is independent, auto-sufficient and, at the same time, can generate profits selling the excess energy trough the electric grid.
As it was mentioned EFMT has big fuel flexibility due to the combustion process that takes place outside of the thermodynamic cycle. The fuel has to be chosen according to its availability in the place of application. In this study the use of Biogas is proposed due to the capability to produce it in the Dairy Farms (or arranged an association between farmers for Biogas production) from the waste matter of the cows. After the Biogas is obtained this is used to drive the EFMT, the outputs of this process are electricity and heat, most of the latter is then combined with an absorption chiller system to obtain refrigeration for the milk, the remaining heat is for heating water that is necessary for cleaning equipment and tools inside the farm.
This study was developed in the central part of Bolivia where near the populated cities there are still farmers who live concentrate in the same geographical area, currently most of them have access to the electric grid, and they have conventional refrigeration systems (compression) for the storage of milk which is critical however it depends of the reliability of the electric system. When the production of milk in a farm is near 2000 liters per day, the farmers have their own storage facility if not they have an small association and own their common storage center where many farmers carry the milk every day, they reach a production of 3500 liters per day in some cases. The milk company picks up the milk every day. Dairy Farms require reliable and continuous refrigeration systems, in this sense, new alternatives are important to explore. Two are the major thermal demands identified in this case study, first refrigeration for milk storage and heat water for sanitary cleaning purposes.
