The sun's energy, renewable and universal, is made available to the refrigeration industry with the aim of conserving the natural resources that today are on the way to being depleted.
by María Cecilia Hernández
Until a couple of decades ago using solar radiation to produce cold was a far-fetched idea. At present, the global trend points towards the use of renewable natural resources to meet the needs of human beings without negatively affecting the environment.
In that sense, technological and scientific advances in how the energy produced by the sun can be used, inexhaustible and powerful, have put on the HVACR scene the immense possibilities and benefits of solar cooling.
"Within the applications with solar energy, that of refrigeration is one of the most important and interesting due, on the one hand, to the technological challenge involved in developing systems of this type, and on the other, to the fact that in this application the two fundamental elements coincide for a good development and a firm market to be established, these are availability and need. That is, the more radiant energy flow reaches a certain place, the higher the ambient temperatures and, therefore, the more cooling or cooling is required," said Sofanor Alarcón, Business Development Manager of JCI Manufacturing Facility Services, Mexico.
The expert complemented his vision with a concrete example: "it is known that in tropical countries almost no meat and milk are consumed among other short-lived products, because they decompose very easily and most people with limited economic resources do not have adequate refrigeration systems for their conservation. It is also known that in these same countries much of the fruit and vegetable harvests are lost for the same reason."
As explained by Alarcón, the ability to store solar thermal energy is essential to continuously deliver energy that is stored in a fluctuating way, as is the case of solar energy. For the process it is very important to understand that what is stored is not precisely thermal energy since it is not conserved in the form of heat; but what is obtained is a chemical energy.
Refrigerate with the sun?
Experts from the engineering area of the company Trane, specialized in the HVAC market, explained to ACR LATINOAMÉRICA that a solar cooling system is made up of several elements, each very important:
* Solar collector, responsible for carrying the ammonia solution - water at temperatures of 80°C, to produce ammonia vapor during the day.
* Rectifier, whose function is to prevent the water vapor that forms in the solar collector from passing to the rest of the system due to the expansion property.
* Condenser, which serves to condense the vaporized ammonia to room temperature, using water that we will have stored in the condenser tank.
* Receiver, used to accumulate liquid ammonia before evaporating overnight.
* Heat exchanger, which cools the liquid ammonia vapor in the hall. Before it goes through a valve to get a better cooling effect
* Evaporator, whose objective is to cool the liquid for use in the cooling process. During the night we let the ammonia evaporate to absorb the heat and thus achieve the cooling effect.
Implementing a cooling system by means of solar energy in any context, whether residential, industrial or commercial, represents great benefits. This is confirmed by César Alejandro Isaza Roldán, professor and researcher of the Energy and Thermodynamics group of the Faculty of Mechanical Engineering of the Pontifical Bolivarian University of Medellín (Colombia), when he expresses that solar cooling brings environmental and economic advantages that are very difficult to achieve with other conventional systems.
"It is a renewable energy and arguably unlimited, it does not pollute since the refrigerants that are used do not produce an environmental impact. It is ideal for rural areas where, due to different circumstances, electricity does not reach. In these places far from the big cities, having a cooling equipment that works with solar energy makes it possible to develop a production process, since the investment can be recovered quickly, "said the academic.
In that sense, when asked about the cost of one of these equipment, Isaza said that the investment that must be made is, at least, four or five times greater than the cost of conventional refrigeration equipment. That is, it is equivalent to about US $ 2,500, while equipment that operates with electric power has a cost between US $ 500 to US $ 1,000.
According to César Alejandro Isaza, "there has been an important boost in the market for refrigerators that work with photovoltaic panels because they have decreased their price in recent months. The Chinese, for example, have developed relatively inexpensive equipment that comes with the complete system and is available for a reasonable price."
Positioning in the Latin market
In Central and South America this is a nascent market whose main penetration has occurred in regions where the arrival of electricity is deficient or none. "Solar refrigerators have arrived in the region to keep vaccines in correct conditions, especially in isolated areas in South America," said Sofanor Alarcón.
The entrepreneur also said that "for there to be a massive adoption of this type of systems, we need technological development to be increased according to the yields and efficiencies that are achieved with standard electric cooling systems. That there is reliable information on thermal yields, capacity and battery life, as well as solar absorption panels, so that consultants, engineers and customers can be sure of the investment they are making. In commercial and industrial refrigeration for lithium bromide or ammonia absorption chillers, the requirements indicated above are already well developed and with very good reliability."
For his part, César Isaza believes that in Latin America there has been an important boost in photovoltaic systems. However, "in absorption systems, at least in refrigeration, I think there is still a long way to go, the market is in the development stage. In some French universities, some products have been released for ice production with intermittent adsorption systems, but that implies certain conditions for users to get used to this type of technology."
Another market that has experienced some development is that of solar air conditioning. Isaza indicated that in Europe the installations of solar air conditioning equipment have increased by almost 20% and a dozen companies have appeared that manufacture and market equipment that works exclusively with solar energy, since in that continent there are few sources of electrical energy and the use of air conditioning currently represents 15% of the total world consumption of electrical energy.
"Reducing these consumptions is urgent. I would believe that in the term of two or three years that market will be moving to Latin America where there are better solar radiation conditions and there are greater needs for air conditioning. There are still missing but there are good prospects, talking about solar cooling," said the researcher.