Commercial potential of linear Fresnel solar collectors in the industrial sector of Ecuador: preliminary assessment

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Industry consumes about one-third of the total energy utilised in the world [1; 2]. Heat is responsible for three-quarters of industrial energy demand, and fifty per cent of it is of low to medium temperature [3]. Current heating systems for industrial process heat depend on steam, as well as on hot water, produced basically in boilers, which predominantly uses fossil fuel or electricity [4]. Nevertheless, heat for common industrial requirements may be supplied by concentrated solar systems such as linear Fresnel collectors (LFCs) and parabolic trough collectors (PTCs) [5]. As a matter of fact, to expand the energy matrix based on renewable energies, and to enhance scientific research on this field are goals aligned with the Ecuadorian policies. However, there is limited investigation on concentrated solar energy in the country, and consequently, it has not been applied yet by industry. This review article provides information on promising industrial sectors that could use linear Fresnel collectors for solar heat for industrial processes (SHIP) in Cartuche Cojitambo N., Redina M.M., López Villada J., Soria Peñafiel R., 2019 This work is licensed under a Creative Commons Attribution 4.0 International License https://creativecommons.org/licenses/by/4.0/ the continental region of Ecuador. The outcomes will contribute to forthcoming techno-economic studies. Existing literature on LFCs for SHIP was analysed, which has been carried out as well for the work developed by [6]. First of all, it was necessary to recognise the advantages and disadvantages of LFCs. Then, reliable sources of information such as the Global Solar Atlas [7] and the NSRDB Data Base [8] provided data on the solar resource in Ecuador. At the same time, the most incident industrial sectors of the country and their location were identified, through the review of available statistical reports [9; 10]. Finally, current Ecuadorian policies and legislation on renewable energy were underlined. Linear Fresnel collectors Table 1 shows the drawbacks and benefits of LFCs, in comparison with other concentrated solar technologies, discussed in articles and reports related to the topic. Disadvantages and advantages of LFCs [11-14] Table 1 Disadvantages Advantages The implementation of tracking devices increases financial and maintenance resources Compared to other types of solar fields, this technology is simple, compact and cheap. It has a lower investment cost and a payback period The direct normal irradiance depends, among other factors, on the geographical location Efficiency in the available land use, for its implementation. It offers a multiple land use too; for example, agriculture could make use of the semi-shaded space under the LFCs The mirror rows shade each other at high transversal incidence angles Absorber tubes and collectors can be very long, which reduces pressure losses, the number of loops and tube connections Optical losses may induce a partial decline in the total cost-effectiveness The use of solar radiation presents lower thermal losses thanks to the secondary concentrator in the receiver If it is necessary to reach higher temperatures, then HTFs such as molten salt, oil, and other materials must be added Fresnel for a direct steam generation does not need any HTF in between Cleaning is often needed to reduce dust accumulation. However, it is simpler for LFCs than for PTCs The tracking system of LFC needs lower forces to move the mirrors than PTC Research on advance material to avoid ultraviolet degradation is required Once its useful life is over, most of its components could be recycled. The remaining ones can be incinerated or sent to landfill LFC is a line-focus system that belongs to concentrating direct normal irradiance (DNI) technologies, which can reach temperatures of about 400 °C [15] depending on the heat transfer fluid employed. An LFC is divided into numerous long rows of almost flat mirrors, which rotate individually along one axis to focus solar radiation onto a linear fixed receiver [12; 13]. This technology has been developed mainly by industrial enterprises from Germany, Spain, United States, Italy, France, and others [16; 17]. LFC has not been adopted yet in Ecuador due to a lack of studies showing its technical and economic potential. Industrial sector in Ecuador One of the multiple applications of LFCs is the direct steam generation for SHIP. Key industrial sectors suitable for the adoption of solar thermal systems may differ between countries. For the most part, they are generally food, beverage, transport equipment, machinery, textile, and pulp and paper industries, because approximately 60% of the heating requirements can be supplied at less than 250 °C [18]. According to [19], the agro-food industry has stood out with more than 50% of manufacturing gross domestic product (GDP) in Ecuador. In 2014, the industrial sector accounted for 19,4% of the total energy consumption of the country, which increased by more than 50% from 2006 to 2014. Manufacturing industrial subsector mostly contributed to this increase. Then, in May 2018, the manufacture of food products was by far one of the most incident sectors in Ecuador regarding the manufacturing production index [9]. Accordingly, it may be a key sector for the use of solar thermal systems in the country. Diesel and electricity have been the main sources of energy for the Ecuadorian industry [19], which indicates that they could be reduced or replaced by LFCs. Figure 1. Share in sales of companies with manufacturing activities by province in 2016 Source: Adapted from [10]. It is worth to mention that, as depicted in Figure 1, in 2016, more than 75% of total sales were made by enterprises located in Pichincha and Guayas provinces. In contrast, firms from the Amazon and Insular regions had the lowest percentage of about 1% of the total sales. Solar resource in the continental region of Ecuador The direct normal irradiance is the resource used by concentrated solar technologies for SHIP [20]. Its implementation takes place with higher economic feasibility in areas where DNI is abundant (>5 kWh/m2/day) [19], which are usually located in subtropical latitudes (dry and hot regions with clear skies). Nevertheless, DNI is remarkably higher at higher elevations, where absorption and scattering of sun’s rays owing to aerosols can be much lower [21]. However, values between 4 and 6 kWh/m2/day may be still considered economically feasible [22]. Figure 2. Direct normal irradiation map of Ecuador Source: Global Solar Atlas [7]. Ecuador has a relatively abundant solar resource that reaches a value of approximately 4,6 kWh/m2/day [19]; with attention to its Andean region, where the DNI is higher. As evidence, Figure 2 [7] illustrates the long-term average of DNI from 1999 to 2015. Conversely, despite Ecuador's important solar potential, the participation of this energy in the energy matrix is minimal. In agreement with Vaca [23], one of the reasons is originated in the limited number of studies to quantify the solar resource in the localities of Ecuador. Ecuadorian policies and regulations on renewable energy Not only Ecuador was the first country worldwide to grant rights to Nature or ‘Pacha Mama’ in its 2008 constitution, but also it has a relevant number of policies and regulations for environmental management. They include mechanisms of promotion and economic incentives that encourage an efficient and sustainable use of natural resources. Table 2 is only an example of Ecuadorian regulations that cite renewable energies, and international agreements on the topic that the country has ratified. Ecuadorian legal framework and international agreements on renewable energy Table 2 Name Year National Constitution of Ecuador [24] 2008 Rio Declaration on Environment and Development [25] 1992 Kyoto Protocol, second period [26] 2013-2020 2030 Agenda for Sustainable Development [27] 2015 ‘Toda una vida’ National Development Plan 2017-2021 [28] 2017-2021 National Energy Efficiency Plan ‘PLANEE’ 2016-2035 [29] 2016-2035 Organic Code of the Environment [30] 2017 Organic Law of Energy Efficiency [31] 2019 Organic Law of the Public Service of Electric Power [32] 2015 Institutional Framework for Environmental Incentives. Ministerial Agreement No. 140 [33] 2015 Preliminary conclusions Ecuador promotes the use of renewable sources of energy and energy efficiency through its legal framework: National Constitution of Ecuador, ‘Toda una vida’ National Development Plan 2017-2021, Organic Code of the Environment, Organic Law of Energy Efficiency, the Organic Law of the Public Service of Electric Power, and so on. Moreover, the country has ratified international commitments on this regard: Kyoto Protocol, Rio Declaration on Environment and Development, 2030 Agenda for Sustainable Development. LFC is a simple, compact and reasonable technology, with techno-commercial challenges. It is geographically restricted to areas with high DNI, like the Ecuadorian Andes, but fortunately, leading industrial companies are located in many provinces of this region. In spite of having good solar resource and supportive laws, Ecuador has insufficient research on LFC for SHIP. This technology has not been adopted yet by the industrial sector. The implementation of LFCs in the manufacturing sector of Ecuador could reduce the use of conventional sources of energy, especially in the food industry. All these points considered suggest that there is a feasible market for linear Fresnel technology in the country. Nevertheless, this conclusion must be confirmed or denied by means of further research.

About the authors

Nathaly Cartuche Cojitambo

Peoples’ Friendship University of Russia (RUDN University)

Author for correspondence.
Email: nathalycartuche@gmail.com

master’s student, Department of Applied Ecology, Ecological Faculty

Moscow, Russian Federation

Margarita M Redina

Peoples’ Friendship University of Russia (RUDN University)

Email: redina-mm@rudn.ru

Doctor of Economic Sciences, Associate Professor, Dean of the Faculty of Ecology, Head of the Department of Applied Ecology

Moscow, Russian Federation

Jesus López Villada

The National Polytechnic School

Email: jesus.lopez@epn.edu.ec

Doctor of Mechanical Engineering in HVAC (Heating, Ventilation and Air Aconditioning) Technologies and Energy Efficiency in Buildings, Department of Mechanical Engineering

Quito, Republic of Ecuador

Rafael Soria Peñafiel

The National Polytechnic School

Email: rafael.soria01@epn.edu.ec

Doctor of Science in Energy Planning, Department of Mechanical Engineering

Quito, Republic of Ecuador

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