Concentrating Solar Power Systems: a review of their applicability in Colombia

This paper evaluates the applicability of centralized concentrating solar power systems in Colombia. For this purpose, these systems have been classified into four subsystems: parabolic trough, linear Fresnel, parabolic dish and tower. Each is explored for its suitability by meeting a set of six attributes. A bibliometric analysis process was developed using the Scopus database and the VOSviewer software to present the potential of each subsystem evaluated through an evaluation matrix. The analysis of the subsystems and attributes was carried out through the formal concept analysis methodology 8FCA). To facilitate data processing, the open access software concept Explorer is implemented. The analysis shows that parabolic trough technology is more widely used worldwide than the other three technologies evaluated, and its maturity makes it possible to plan centralized and decentralized projects in developing countries. The bibliometric analysis integrated with the applied FCA methodology has proven to be useful for the evaluation of technological typologies and serves as an alternative to develop theoretical studies that group and link different options as a model to evaluate a deterministic set of attributes.


Introduction
Climate change is perhaps one of the greatest challenges facing the human species today and may be the result of natural causes or human influence.The latter produces the climatic alterations with the highest levels of incidence due to the use of fossil fuels for decades, affecting diverse weather patterns that directly incur in problems such as global warming.However, human beings must maintain a quality of life and economic development; therefore, the use of fossil fuels has been helpful for human survival and development [1].
The use of fossil fuels has increased in recent decades with industrial development and population growth.It is estimated that in one-year human beings consume what nature has processed for a million 1299 (2024) 012009 IOP Publishing doi:10.1088/1757-899X/1299/1/012009 2 years and currently, more is consumed than nature is able to process, projecting an irreversible shortage in the future.Additionally, its use generates problems such as: alteration of the greenhouse effect, acid rains, social problems worldwide, among others.[2].
According to the International Energy Agency, in the year 2021 the emissions of Carbon Oxide (CO2) related to energy will grow by 5%, being CO2 one of the gases with the highest generation in the world due to the burning of fossil fuels and, at the same time, the one that has the greatest impact on global warming [3].In order to stabilize gas concentrations in the world, the United Nations Conference on Climate Change was held at the United Nations Headquarters in New York, USA.(CP26), was held to review the actions of the countries worldwide that adhered to the Paris Agreement (COP21) and to ratify the commitment of all to reduce the consumption of fossil fuels and the use of renewable energies as an alternative to mitigate climate change [2].
Consequently, the use of renewable energies has increased in the last decade and technologies that take advantage of sources such as: sun, wind, biomass, water, heat, among others, have been implemented in some sectors worldwide in a centralized and decentralized manner for energy production, highlighting the use of solar radiation as one of the main sources of electricity and heat generation.However, the process is increasing in developed countries, with the opposite scenario in developing countries [4].
Currently, the largest power generation plants using renewable resources use photovoltaic panel technology [5].However, there are technologies such as concentrating solar power systems that also take advantage of solar radiation and are a viable alternative for centralized energy production in the world (largest number of plants in the U.S. and Spain), projected to be able to supply 6% of the world's demand in 2030 and 12% in 2050 [6].
For the theoretical development of this document, the solar concentration technologies will be evaluated, applying a bibliometric analysis by means of VOSviewer software, the information obtained will be evaluated by means of the method of formal analysis of concepts [7] [8] and the use of the software concept Explorer [9], relating attributes and objects, simplifying information processing.With this in mind, the objectives of this work are: i. Define the attributes that satisfy each of the concentrating solar technologies.ii.
Develop a review of the academic literature through databases and specialized software to evaluate the objects under the established attributes.iii.
Discuss the relationship between the technology and the attributes established through the use of formal Concept Analysis.For this approach, the document is organized as follows.Section 2 presents the methodology, defining the bibliometric search string, as well as the attributes and assigning to each technology an object for the development of the formal concept analysis.Section 3 covers the literature review on solar concentrators, focusing on the level of compliance with each of the attributes.Section 4 presents the critical review using the Concept Explorer tool and the formal concept analysis method.Finally, section 5 presents the most relevant conclusions of the study.

Methodology
The formal analysis of concepts is an objective analysis based on a series of attributes and objects, which allows us to relate them and determine which objects comply with a greater number of attributes, showing the attributes they share among them [8].Consequently, the existing types of CSP solar concentrators will be related as objects and it will be analyzed whether they meet the following attributes in order to comply with the objectives outlined.It is important to note that, to a certain extent, the author of this paper has taken the following attributes as guidelines to identify the technology with the greatest potential worldwide that adapts to Colombia's needs.Initially, a specialized bibliometric analysis was carried out to identify the articles with the highest incidence in the subject of study in order to feed the FCA methodology.The database used was Scopus and the program used to manage the information was the VOSviewer software, as shown in Figure 1.For its part, the formal analysis of concepts is based on the fulfillment, to a greater or lesser extent, of a series of attributes with respect to a series of objects [13].The following are the attributes that each carbon sequestration technology system must meet: A1.Cost: will meet the criterion of the two technologies with the lowest initial investment cost.A2.Technology complexity: the two technologies with the lowest maintenance and operation requirements will meet the criterion.
A3. Maturity: will meet the highest maturity level of the four technologies.A4.Life cycle: will the technology comply with a more favorable life cycle assessment (LCA) A5.Implementation area: meet the two technologies with the lowest land use for operation, with high yield levels A6.Weather Conditions A7.System efficiency: the two most efficient technologies will meet the highest level of efficiency; the concentration ratio will be measured.
Considering the objects and attributes, each object is evaluated by each of the attributes listed above.This will result in a matrix that will feed the concept Explorer tool, allowing a qualitative evaluation of the information [9].

Global Warming in the world
Today, the planet is highly dependent on solutions to existing environmental problems that have become more acute in recent decades [10].Soil contamination, air pollution, scarcity of drinking water, population increase, decrease of fertile land for cultivation, deforestation, cattle raising, among others, are direct causes of climate change and global warming [11].The need for energy access throughout the world to maintain quality of life and technological development requires a supply of electrical and thermal energy.To cover this energy demand, an accelerated consumption of fossil fuels has been generated, generating as a negative effect the production of gases that affect the greenhouse effect, aggravating and precipitating global warming [1], environmental challenge facing the planet today.
The condition of the environment is one of the major concerns of governments around the world, due to the high levels of pollution that have an immense impact on people's quality of life [12].The industrial revolution was the turning point at which greenhouse gas (GHG) emissions into the atmosphere began to skyrocket.Figure 2 shows the trend of CO2 accumulation from 1958 to 2020 and shows a marked increase in recent decades, with CO2 being one of the gases produced by the burning of fossil fuels and perhaps the gas with the greatest impact on global warming [2].GHGs are produced naturally and are essential to maintain the planet earth in ideal conditions for humanity to survive, however, the excessive production of gases, deforestation and large-scale agriculture have directly intervened in this natural process, causing environmental phenomena that directly affect human life.he most abundant GHG is carbon dioxide (CO2), which results from the burning of fossil fuels, used for example worldwide for the mobility of transport vehicles [13].
Based on the report presented by Foster and Elzinga on the UN website it is highlighted that: "Fossil fuels currently comprise approximately 80% of current global primary energy demand and the energy system is the source of approximately two-thirds of global CO2 emissions" [1].Foster y Elzinga, emissions do not include emissions of methane and other short-lived climate pollutants, so energy production and use may be sources with higher proportions of emissions.In turn, the UN Intergovernmental Panel on Climate Change (IPPC) was created by the World Meteorological Organization (WMO) and UN Environment to provide an objective view of scientifically reliable information on the status and future of global warming.The IPPC presented a report in the year 2021, entitled "Climate Change 2021: Physical Basis", where they state: "Global warming is Widespread, rapidly advancing and intensifying.They also underline the urgency of substantial, rapid and sustained reductions in greenhouse gas emissions.In addition, they point out that in all regions of the world the climate system is changing and that phenomena such as the continuous rise in sea level will not be reversed for several centuries" [14].
The report presented by the IPPC makes it clear that human action in current environmental problems is indisputable, and highlights that humanity must consider substantial and sustained measures to immediately reduce emissions of carbon dioxide (CO2) and other greenhouse gases to curb the growing pollution of the atmosphere, generating immediate health benefits, stabilizing the global average temperature within two to three decades [14].
The IPPC report, endorsed by 195 governments and prepared by Working Group I, is the first installment of the Sixth Assessment Report "AR6 Climate Change 2021: The Physical Science Basis" and will be completed by the end of 2022.For the first time, it is expected to complete a detailed analysis of climate change at the regional level, allowing to show the current state and help interpret what is supposed to be the appropriate path for human action to generate a positive impact on environmental problems in society and ecosystems.
If current trends of accelerated fossil fuel use continue due to energy demand that is projected to double by 2050, gas emissions will far exceed the levels proposed to curb global warming and could instead increase global temperatures by 2°C [1].However, the reduction of emissions should not exclude the use of fossil fuels, but requires a significant change of direction, i.e. the use of renewable energy technologies, improved energy efficiency in industrial facilities and processes worldwide, as well as carbon capture and storage [15].This is why the assumption of using only fossil fuels for the entire energy system has disappeared, i.e., it is necessary to implement technologies that allow the generation of a gradual energy mix, which will make it possible to curb global warming and reduce dependence on fossil fuels in the world.Renewable energy technologies have positioned themselves in recent years as an alternative with projection and capacity, but with limitations due to their non-uniform use throughout the energy system, due to the variation in production.In addition, alternative technologies that can replace current industrial production techniques are in the process of centralized experimentation and have presented significant advances that provide an adequate future articulation to the world's energy supply [1].
On the other hand, carbon capture technology exists to contribute as much as renewable technologies in reducing the use of fossil fuels, however, carbon sequestration or capture is currently decentralized, with only a few applications at a centralized level, but it is expected that over the years, the technology will gain maturity and can contribute significantly to the current environmental problems.
It is important to mention that there are currently developing countries with unexplored fossil resources and a growing interest in using them to improve the quality of life of their inhabitants and to develop their economies.This scenario, in view of the current problems and the developed countries that have used their fossil resources for growth, generates an uncertain scenario with political tensions.However, a consensus must be generated so as not to slow down the growth of these developing countries and the appropriate use of renewable energies as an alternative for energy production in these countries.
Finally, the idea of developing smart energy grids that have common rules would provide a global opportunity for collaboration between technologies, generating a more efficient and sustainable consumption and generation system.Generating social and economic development worldwide.Integrating the rational use of fossil fuels and alternative technologies, which could gradually replace a large part of the consumption percentages of fossil fuels.It is important to link emerging economies and developing countries to change the dynamics of current policies and help form a strong global climate agreement.

Current Status of Projects in the World
Concentrating solar power is used worldwide in the industrial sector to supply heat or to produce electricity.Figure 3 presents the percentages of energy from solar collection in sectors such as: residential, industrial, transportation and others.The sector with the highest energy consumption is the industrial sector, followed by the transportation sector with 32% and 31%, respectively.The industrial sector of the 100% of energy consumed, only 26% is electrical energy, which shows a high demand for thermal consumption.The National Renewable Energy Laboratory (NREL) has a database of all existing centralized concentration projects, describing location, capacity, status (operational or not operational), among other relevant data.Additionally, it presents a mapping as shown in Figure 4.The 2D and 3D concentrating solar power systems are sometimes integrated with photovoltaic systems, however, in the compilation of information describing the existing concentrating solar power plants in the world, it was not possible to discriminate whether the parabolic trough systems were integrated with other systems (photovoltaic-PV).

Critical Literature Review
Concentrating solar power (CSP) has been in the research orbit recently, as it shows favorable environmental results compared to other technologies [17] [18] that use fossil fuels for their operation [19].Concentration technologies are classified into 2D and 3D systems [20].The 2D systems are technologically divided into Parabolic Trough Collectors (PTC) and Linear Fresnel Reflectors (LFR).3D systems are technologically divided into parabolic dish collectors (PDC) and solar power towers (SPT) [21].The two technologies that currently dominate the market are PTC and SPT, with parabolic trough collectors (PTC) being the most mature technology, followed by SPT, LFR and PDC respectively [22] [23].The PTC and LFR systems are linear concentration collectors, while the SPT and PDC systems are point concentration.Linear concentration technologies have lower concentration ratios compared to point concentration technologies [24].
PTC, SPT and LFR technologies are recommended for power generation systems with sizes ranging from 10 to 200 MW, while PDC technology is recommended for low generation between 0.01 and 0.4 MW [25] [26].Currently, there are about 135 CSP plants (see Table 6) operating in the world, 80% of which implement PTC technology, being the technology with the most operational and commercial experience at a global level.[27].Consequently, PTC has the lowest technical and financial risks in the market, followed by SPT technology [28] [22].
On the other hand, the PDC technology, when implemented at a low scale, presents minimum soil occupation, while technologies such as PTC, LFR and SPT present high soil occupations, however, the PTC technology currently presents the best ratio of the three with respect to soil occupation and efficiency [29] [30].This trend may tend to decrease due to the growth of SPT technology, however, it depends on market dynamics to gain more commercial experience in the coming years [31] [12].
Technologically, 2D or linear systems offer greater flexibility in construction, operation and maintenance [32] [33].3D technologies, on the other hand, are designed to generate more waste heat, implying a higher investment in the development of the systems [34] [35].In addition, the life cycle of the 4 technologies is usually similar, depending on the size of the plant and the capacity, periodic intervention plans must be generated to guarantee the operability of the system [36] [37].
Finally, concentrating solar power technologies in general require identical weather conditions, with high normal direct solar irradiation (DNI) for long daily periods of the year, to ensure their operation and profitability [38] [39].It is therefore recommended that for areas with extreme radiation levels such as coastal areas [40] [41].
Table 1 presents the matrix of the relationship between attributes and objectives; the attributes that meet the stated objectives are marked with an X.

Results
The current state of technology places Spain and the United States as world leaders in the process of generating electricity from concentrating solar power (CSP) plants, with the installed capacity in both countries exceeding 73% of the global CSP installation capacity in the world.Considering the CSP projects under development worldwide, China is projected to be the country with the largest investment in concentrated solar power.China is currently building around 15 CSP plants for a total capacity of approximately 1064 MWe.The Chinese government has a vision towards renewable energies, ratified at COP21, which seeks to limit the accelerated process of global warming that the world is undergoing.Other developing countries such as Chile, India, the United Arab Emirates, Morocco and South Africa have developed CSP power generation projects, supported by various organizations such as the World Bank's Global Environment Facility, the German Federal Enterprise for International Cooperation and the Desertec Foundation.It is important to note that Chile is the first country in South America to have a centralized SPS system.
The results of the methodological application of the formal analysis of concepts through the Conception Explorer software are presented below.The different nodes shown in Figure 18 are identified in the following way: • Blue-white: contains only attributes • Blue-black: these are containers of solar tracking technologies related to attributes • Black-White: Control Algorithm Only Containers • White: Nodes acting as connectors between branches Considering the above, the analysis of the diagram is simple.The four concentrating solar power (CSP) technologies are related to the attributes that, in turn, connect from the top down to the node of origin.At a glance, Figure 5 shows that attributes A1 "Cost", A2 "Technological complexity", A3 "Maturity", A4 "Life cycle", A5 "Implementation area", A6 "Weather conditions" and A7 "System efficiency" are not fully met by all objects.However, it is evident that attributes A4 and A6 are contained in all objects.
Figure 6 shows in blue the line that connects attributes with the specific objective of the PTC technology, highlighting: • PTC technology meets attributes A1, A2, A3, A4, A5 and A6.PDC and TRF technologies are evident in the graph because they share attributes with PTC.• The PTC technology within the present analysis is the technology with the greatest potential for implementation globally for the specific characteristics.In turn, Figure 8 shows in blue the line that connects attributes with the specific objective of the SPT technology, highlighting: • SPT technology complies with attributes A4, A5, A6 and A7.The graph does not show the other technologies; however, the white circles are nodes that link objects to each other, so it is evident that they share the fulfillment of all the attributes mentioned above.
• The SPT technology in the present analysis is the technology with a high global implementation potential for the specific characteristics evaluated.

Conclusions
The use of fossil fuels is one of the main causes of global warming, the excessive use of petroleum derivatives for the daily use of the human race has been excessive, which requires the use of alternative energy systems, being concentrating systems a promising technological line.However, it should be emphasized that the use of fossil fuels cannot be totally eliminated; rather, they should be gradually replaced over time, in order to generate a gradual decrease in global warming and a broader energy mix in the world.
Concentrating solar power (CSP) technologies are presented in the current world scenario as a key source of flexibility and application for electricity generation as an alternative to fossil fuels.To strengthen its implementation, a climate policy framework and a reduction in implementation costs are needed to generate greater impact at the centralized level.
CSP technologies face challenges for large-scale deployment that include lowering the cost compared to photovoltaic (PV) systems.At the same time, they require market mechanisms that guarantee the use of the energy generated by users, in order to maximize the economic contributions that would allow the growing development of more projects worldwide.
PTC technology is the technology with the greatest potential for implementation worldwide for centralized power generation systems.Based on the attributes defined to evaluate its potential application in future projects in Colombia, the PTC technology stood out for its cost-performance ratio, simple technology to implement, maintain and operate, as well as greater commercial maturity.These characteristics make it a promising technology in the process of applying new electric generation technologies in the country, generating an energy mix that feeds the national grid.
SPT technology is promising and it is expected that, over time, it could match or surpass PTC technology in terms of benefits.TRF technology is still in the process of commercial development, so the time to maturity may be longer than with SPT technology.Lastly, PDS systems are aimed at small generation plants, so their application in a centralized manner has been limited to date.
Finally, the application of the formal concept analysis (FCA) methodology allowed a critical evaluation of CSP technologies by directing the search for information to previously established parameters.Although the FCA methodology allows an interesting analysis of the information, it should not be replaced by numerical methods that allow information to be obtained with higher levels of precision; rather, it should be part of a first stage of literature review.

Figure 3 .
Figure 3. Use of solar thermal energy in consumer sectors[16]

Figure 4 .
Figure 4. Solar energy projects in the world[16]

Figure 5 .
Figure 5.General FCA analysis diagram CSP Technologies

Figure 6 .
Figure 6.Specific FCA diagram for PTC technology

Figure 7 .
Figure 7. Specific FCA diagram for TRF technology

Figure 9 .
Figure 9. Specific FCA diagram for PDC technology