Currently, increasing world population demands a higher cement production. Therefore atmospheric emissions and energy consumption become two of the most important environmental and economic issues. Fuel and electricity consumption for the production of cement represent 40% of the total production cost . It is known that cement production is an energy-intensive process which contributes with approximately 5% of the worldwide carbon dioxide (CO2) emissions  .
By using Concentrated Solar Thermal (CST) at the calcination process in the cement production line, CO2 emissions can be reduced by 40% and savings of up to 60% through fuel substitution can be obtained if all the fuel used at the calcination step is substituted.
The aim of the study is not to propose a detailed design of the solar process but to examine and quantify the various options in order to define the favorable economic conditions and the technical issues to face in a conventional cement plant aiming: substituting energy sources and achieving continuous operation of the cement plant employing a hybrid mode.
Three options related with how to apply the CST technology were evaluated. The best solution is a Central Tower with Solar Reactor at the Top of the Tower since it allows energy substitution with high thermal energy efficiency. This implies, compared with the other options, the minimum changes in the process.
Several energy substitution scenarios are investigated considering different energy losses and amount of energy to be replaced. It was found that the solar energy availability is not a constraint, meaning that from the technical point of view it is possible to replace up to 100% of the energy requirements for the calcination process.
Economic results are promissory since the application of the proposed approach (Go Process) became attractive. The Payback Time (PBT) obtained (from 6 to 10 years) is lower when it is compared with the PBT for applications of CST for electricity production. Besides, the IRR values obtained (from 8% to 11%) are adequate in accordance with the typical values expected by most of the equity investors in renewable energy projects (between 8% and 12%) .
It is expected that CST technology will become more attractive and profitable due to economic aspects like increments in fossil fuels and alternative fuels cost and the current deployment of the CST technology to produce electricity. Other aspects such as more strict legislation related with CO2 emissions combined with encouraging legislation to use of renewable energy also play an important role in the economic attractiveness of the proposed application.