Scientists at the CSIC have developed a new type of heat-pump system which prevents environmental and safety problems, as it has not either greenhouse gases nor risk of Legionella. The prototypes are small and robust, therefore they can be used in transport (buses, trucks or boats), using as a source of energy the remaining heat of the exhaust fumes.

 

 Prototype of single-double effect on an air condensing unit.Heat-pump equipments for refrigeration are considered the most efficient systems. Nevertheless, they have some inconvenient. Domestic heat-pump equipments use organic refrigerant fluids which contain chlorine and fluorine, the so called HCFC and HFC. These gases, if they are released –in case of leaks or incorrect disposal-  they can be harmful for the environment. The HCFC fluids destroy the ozone layer and are greenhouse gases. The HFC fluids are also greenhouse gases. In both cases, their global warming potential is several thousand times higher than CO2. Why they are still used in spite this risk? Because they are safe for the system and for persons as they are not a potential focus of Legionella.

Other options of organic refrigerants are propane and isobutene, which have outstanding refrigeration capacities. They don’t destroy the ozone layer and their warming potential is only twice the one of Co2. But they are not normally used because they are inflammable.  

Other refrigerant fluids are ammonia and water. The use of ammonia, which is considered one of the best refrigerants, is restricted because its chemical characteristics. Water is used as a refrigerant in absorption refrigerators. The problem, in this case, is that Legionella can breed in water condensing machines. Legionella is a bacteria which normally grows in piped water systems, cooling towers, and causes the infectious and serious disease legionellosis. For this reason, water condensing heat-pumps are not allowed for domestic uses and they are used only in buildings and facilities with strict security control.

It is possible to have a heat-pump system safe for both the environment and people? A scientific team at the CSIC has developed an absorption refrigeration system based on the use of lithium bromide and water. Marcelo Izquierdo, at the Instituto de Ciencias de la Construcción Eduardo Torroja, is the main scientists of the project. He explains: “The lithium bromide-water solution is easy to be obtained and has a longer lifespan than other refrigerants nowadays in the market. Besides, it works normally at a lower pressure than atmospheric, therefore if there is a breakage or a crack in the machine, the fluid wouldn’t spill”. Other advantages are that it doesn’t pollute the atmosphere and it has not any direct warming effect. If the machine is an air condensing one, it has neither the risk of Legionella. Double-effect prototype.

The prototypes can also be powered by solar energy and they use 85% less water than the current condensing water systems

Several prototypes of different sizes have been developed and are being tested now at the  research station for solar energy of the Instituto Eduardo Torroja, in Arganda del Rey,  Madrid. The system has shown to be effective with temperatures outside of 42ºC. Something to highlight is that the developed prototypes have a cooling capacity of few kW, which is very similar to the capacity of domestic systems. The prototypes can also be powered by solar energy and they use 85% less water than the current condensing water systems. In combination with solar energy, they can be used as heating and hot water system.

As the prototypes are small, they could replace the conventional mobile systems based on HCFC and HFC, which are used for ships, buses or trucks. “The prototype we have created can use the remaining heat as a source of energy”, explains Marcelo Izquierdo. “In a bus, for instance, one of our systems could work using the remaining heat of the exhaust fumes as a power source”.  The developed prototype can also work with biomass, natural gas or liquefied petroleum gas.

The idea of using lithium bromide and water in refrigeration is not new. Nevertheless, this is the first time that an efficient prototype, with a good performance and similar size and price to current systems, has been developed. The prototypes have been patented by the CSIC and now industrials partners are sought.

Contact:

Marisa Carrascoso Arranz
Área de Ciencias de Materiales
Vicepresidencia Adjunta de
Transferencia del Conocimiento
Consejo Superior de Investigaciones
Científicas (CSIC)
Tel.: + 34 – 91 568 15 33
This email address is being protected from spambots. You need JavaScript enabled to view it.