**3. Analysis of results**

The original energy consumption of the process is 880.202 kW for 5 h/day with a generation of CO2 emissions of 312.7 tons/year (893.40 kg/day). The average price of natural gas reported worldwide for 2020 was 0.047 USD/kWh [20]. While the reported price of the same fuel in Mexico, for first month of 2019, was 0.3589 USD/ kWh [21]. As can be seen, they present a significant difference that will directly impact the investment recovery time. It should be noted that the price of natural gas in Mexico has varied significantly from January 2019 (0.3589 USD/kWh) to December 2020 (0.024 USD/kWh).

When analysing the match between the energy requirement of the process and the availability of solar energy, it was determined that it is 2 h. However, there is availability of solar thermal energy at the target temperature for 1 h more that can be used as most convenient in the operation of the solar thermal device. To supply the entire thermal load and cover the remaining three hours, a storage tank of 32.58 m<sup>3</sup> is required.

In scenario 1 it is considered that there are no restrictions due to limitation of available area and capital investment. When carrying out the integration of energy, the requirement of the hot utility is reduced by 61.4%, the rest can be provided with solar thermal energy and the generation of greenhouse gases is zero. The total cost of the integrated system (heat recovery network and solar thermal installation) is 1,995,266.49 USD. If the investment is made for 25 years, the cost is 145,488.85 USD/year. The payback for the integrated system is 27.56 years (according to international data) and 3.6 years (Mexican data). When considering only the solar thermal installation, the payback is 5.99 years (according to the international estimate) and 0.78 years (according to the national evaluation).

In scenario 2 there is an available area restriction of 50% (650 m<sup>2</sup> ). The resulting network, depending on the available space, presents an arrangement of 11x29 with a thermal load of 181.45 kW that can supply 2 h of the thermal requirement of the process. The supply of the thermal load for those 2 h can be given directly from 11:00 h - 13:00 without storage or, it can be supplied from 8:00 h - 10:00 h with storage. Based on the economic aspect for scenario 2, the supply of the thermal load will be for 2 h without storage. The cost of the integrated system is 1,750,541.36 USD with a reduction of 12% compared to scenario 1. CO2 emissions into the atmosphere are 60.36 tons/year. The payback of the integrated system is 24.17 years (according to the international price of gas) and 3.166 years (according to the national price of gas). The payback of the solar collector network is 2.61 years (according to the international gas price report) and 0.34 years (for the national gas price reported).

*2.6.2 Environmental impact assessment*

*Solar Cells - Theory, Materials and Recent Advances*

Union [19].

**3. Analysis of results**

32.58 m<sup>3</sup> is required.

price reported).

**468**

December 2020 (0.024 USD/kWh).

Currently, solar thermal technology is competitive against those that operate with fossil fuels, however, the negative environmental impact generated by these energy sources is global and tangible. One of the most well-known parameters is the quantification of CO2 emissions as greenhouse gas, however, they are not the only gases emitted, in addition, there are other no less important parameters that are not considered. In this study, only the tons of CO2 that are ceased to be emitted into the atmosphere are quantified when integrating solar thermal energy into the process. The factor of 0.203 kg CO2/kWh is considered for fixed combustion equipment that works with natural gas as fuel, this data is reported for the European

The original energy consumption of the process is 880.202 kW for 5 h/day with a generation of CO2 emissions of 312.7 tons/year (893.40 kg/day). The average price of natural gas reported worldwide for 2020 was 0.047 USD/kWh [20]. While the reported price of the same fuel in Mexico, for first month of 2019, was 0.3589 USD/ kWh [21]. As can be seen, they present a significant difference that will directly impact the investment recovery time. It should be noted that the price of natural gas

When analysing the match between the energy requirement of the process and the availability of solar energy, it was determined that it is 2 h. However, there is availability of solar thermal energy at the target temperature for 1 h more that can be used as most convenient in the operation of the solar thermal device. To supply the entire thermal load and cover the remaining three hours, a storage tank of

In scenario 1 it is considered that there are no restrictions due to limitation of available area and capital investment. When carrying out the integration of energy, the requirement of the hot utility is reduced by 61.4%, the rest can be provided with solar thermal energy and the generation of greenhouse gases is zero. The total cost of the integrated system (heat recovery network and solar thermal installation) is 1,995,266.49 USD. If the investment is made for 25 years, the cost is 145,488.85 USD/year. The payback for the integrated system is 27.56 years (according to international data) and 3.6 years (Mexican data). When considering only the solar thermal installation, the payback is 5.99 years (according to the international esti-

network, depending on the available space, presents an arrangement of 11x29 with a thermal load of 181.45 kW that can supply 2 h of the thermal requirement of the process. The supply of the thermal load for those 2 h can be given directly from 11:00 h - 13:00 without storage or, it can be supplied from 8:00 h - 10:00 h with storage. Based on the economic aspect for scenario 2, the supply of the thermal load will be for 2 h without storage. The cost of the integrated system is 1,750,541.36 USD with a reduction of 12% compared to scenario 1. CO2 emissions into the atmosphere are 60.36 tons/year. The payback of the integrated system is 24.17 years (according to the international price of gas) and 3.166 years (according to the national price of gas). The payback of the solar collector network is 2.61 years (according to the international gas price report) and 0.34 years (for the national gas

). The resulting

mate) and 0.78 years (according to the national evaluation).

In scenario 2 there is an available area restriction of 50% (650 m<sup>2</sup>

in Mexico has varied significantly from January 2019 (0.3589 USD/kWh) to
