# Analysis of Disinfection in Greenhouse Soils with Medium-Temperature Steam Produced by Solar Energy
## 1 Introduction
### Solar Energy Concentrating Systems  
The search for technology for producing energy through renewable resources has been developing for several decades. The use of wind energy, biomass, geothermal energy and, above all, solar energy has made great advances and improvements. After obtaining energy through renewable energies, the application of these methods in other areas of knowledge was begun, seeking to use them in other processes and systems in order to replace the energy produced by hydrocarbons that come from non-renewable resources and that significantly pollute the environment. There are three methods of generating energy from solar radiation: thermal, photovoltaic and thermoelectric. The systems can also be classified according to the temperature they work at--for example, low, medium and high [34]. In low-temperature thermal systems, a solar collector transforms the incident solar energy into another form of useful energy, and the thermal transfer is carried out from an energy source (the sun) to a fluid, without the concentration of solar energy. The incident flux can be of the order of 1 kWm\({}^{-1}\); radiation is used in a wavelength range of \(\lambda\) = 0.3 \(\upmu\)m and 3.0 \(\upmu\)m, with temperatures between 40 \({}^{\circ}\)C and 120 \({}^{\circ}\)C. These collectors use both direct and diffuse solar radiation and do not require solar tracking systems. Its applications are focused on water heating systems, building heating and air conditioning. In the case of medium-temperature systems, reflective concentrators (for example, parabolic cylindrical concentrators, PCC) are built using large optical surfaces, such as mirrors or prisms. The overall reflectivity of the system is of the order of 90%. In these systems, only the direct component of the radiation is exploited. Optical systems are used to increase the intensity of the solar radiation that is directed on a receiving surface that absorbs it. It is necessary to follow the sun and for the flows to not be stationary. These systems are composed of two fundamental parts, the concentrator and the receiver, and can reach temperatures from 100 to 400 \({}^{\circ}\)C and produce working steam that can be used in turbines for the generation of electrical power and other processes [35]. For high-temperature systems, high-temperature solar thermal power plants are used for the transformation of solar energy into electricity through a thermodynamic cycle; these reflect the direct solar radiation that affects them in a receiver located high above the ground, in which the mirrors are located so that all the energy is transported at the same time by radiation [36; 37; 38; 39]. For all of the above, since medium-temperature systems such as PCC can be used to produce working steam, we propose using this steam to disinfect greenhouse soils. The output of the system will no longer be to produce electrical energy but to carry out a constant exposure of vapor to greenhouse soil with temperatures above 100 degrees. On one hand, the latter allows for the elimination of weeds and bacteria, and on the other, it also stands as an alternative to the solarization method that uses pollution and involves difficulties in removing the plastic. Finally, by using a PCC, one can control the temperature, pressure and steam output flow through the system instrumentation, which is not possible with the conventional ecological method. This allows for the standardization of the disinfection process and crops' growth. On the other hand, it is evident that the steam production of a PCC has its greatest efficiency in the months of high direct radiation, that is, from March to June of each year. Nevertheless, in this work, we also seek to demonstrate that the disinfection process using this technological proposal is efficient even in the months of low direct radiation.