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Concentrating Solar Power (CSP) plants are a promising technology of renewable energy production, as witnessed by the increasing public and private investments during the last decade. The assessment of the associated risks of business interruption (loss of production) and loss of assets due to the occurrence of undesired internal or external events...
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... first question arises naturally from the general uncertainty on the success of novel technologies, due to lack of experience and the too few lessons that can be learnt from little similar operating plants. To address this question, a scaled-down pilot plant has been designed and is planned to be built on the site of Massa Martana (Italy); the observed generation performances of the pilot plant are expected to contribute to reducing the uncertainties on the selected technology, increasing the Company confidence on the economic viability of the investment program. The answer to the second question requires the development and application of Reliability, Availability and Maintainability (RAM) analyses, taking into account the peculiarities of the plant and the characteristics of the site of installation. With respect to the latter, in fact, the Company investment program foresees to build a number of plants in different regions of the South Mediterranean area, characterized by different environmental conditions. The answer to the third question is the focus of the work presented in this paper, which reports about the research activity carried out in collaboration between Politecnico di Milano and Techint, for the development and application of a methodology for identifying and assessing the economical risks associated to the CSP plant operation, related to the occurrence of undesired events to its components. The paper is organized as follows. Section 2 briefly recalls the essential notions about the CSP technology selected by Techint. Section 3 provides a description of the risk assessment methodology and the results of the application of this methodology. Some concluding remarks and perspectives for future advancements are given in the last Section. The CSP plants, often also called Solar Thermal Power (STP) plants, can be divided into four classes: Fresnel Systems, Solar Towers, Dish/Engine Systems and Parabolic Troughs. All these plants produce electricity in much the same way as conventional power stations. The difference among them is that they obtain their energy input by concentrating in different ways solar radiation, and converting it to high- temperature steam or gas, which then drives a turbine or motor engine. Differently from other solar technologies, the CSP plants can keep working at a constant load thanks to the thermal storage systems, whose main function is equivalent to that of the fuel in other power generation systems. This potentially leads to an optimal plant utilization with higher margins and shorter return of the investment, making the CSP technology particularly attractive for investors. The CSP plant type selected by Techint is based on the conventional parabolic trough, enhanced by innovative design solutions. Figure 1 provides a schematic view of the reference plant and of its key components: mirrors, receivers, thermal storage system and turbine. Roughly speaking, a parabolic solar collector tracks the Sun continuously and exploits the optical properties of the parabolic mirrors, which reflect the incident parallel rays in the optical focal line, to concentrate the Sun‟s rays onto a heat absorber element (the „receiver‟ in Figure 2). The solar radiation warms up the heat transfer fluid flowing through the absorber tube (up to 550°C in the reference plant), and the hot salt mixture is accumulated in the hot tank ( this is technically called the „ thermal storage charging phase ‟, during which the level of the cold tank is reduced and the level of the hot tank is increased). When the delivery of electric energy is required a molten salt flow is spilled out from the hot tank, the fluid is conducted along a heat exchanger in which steam is produced and finally the cooled molten salt flow is re-collected in the cold tank (this is technically called the „ thermal storage discharging phase ‟ : dually from the previous charging phase, the level of the cold tank is increased and the level of the hot tank is reduced). The produced steam generates rotating power in the turbines, which is converted in electrical power with an expected output of about 10-50 MW of electricity, depending on the rate design of the plant. The receiver adopted in the reference CSP plant represents a fundamental technological innovation, patented by ENEA and consisting of a specially coated absorber tube (solar absorbance of 95% and emissivity of 10% at 400°C) which is embedded in an evacuated glass envelope; the high photo-thermal properties allow achieving an high working temperature (580°C) and consequent high efficiency of the plant, with high mechanical reliability. The reflecting panels are also novels; they are made of a thin glass-silvered mirror coupled to a supporting panel in Sheet Moulding Compound (SMC); this solution combines the advantages of the glass mirror (a cheap and reliable reflecting material) with the improved mechanical properties of composite materials. Last but not least, also the heat transfer fluid is an innovative solution; it is a molten salt mixture (60% NaNO 3 - 40% KNO 3 ) operating at temperatures in the range of 290-550°C, assuring chemical stability up to 600°C and which does not contribute to the degradation of the tubes. This innovation leads to several important aspects: the increase of the operating temperature from 390°C up to 550°C, with an increase of the thermodynamic efficiency; the reduction of storage costs consequent to system simplification and reduction of storage media inventory for the same amount of storage capacity; the reduction of the environmental impact of such kind of plants. The methodology developed to assess the plant power generation performance is based on the framework of system risk analysis, focused on business interruption (loss of production) and loss of assets only (in other words, safety consequences are not ...
Citations
... Technical risks are also of a great importance. Indeed, Amato et al. (2011) carried out a very original study by assessing the risks associated with business interruption and loss of assets resulting from the emergence of undesirable internal or external events. These authors identified a list of critical hazards, such as malfunction of the orientation system, turbine failure, turbine leakage, salt solidification, and orientation system stopping. ...
Concentrating solar power (CSP) is a promising technology in Tunisia. However, its diffusion is facing many barriers which deter investments. Through the analysis of a CSP plant in Southern Tunisia by using the Global Risk Analysis (GRA) method, we try to analyze the main risks faced by investors. The main objective of this research is to identify and analyze the risks faced by CSP investors in Tunisia and develop strategies that should be adopted to accelerate the process of diffusion of this technology.
This analysis allows us to conclude that the CSP project is very exposed to political, financial, physical-chemical, legal, and strategic hazards. Moreover, we show that among the four phases of the project, the preparation phase is the most vulnerable to hazards.
In fact, the GRA method makes it possible to determine the list of the major risks, such as the risk of not obtaining permission to build a CSP plant, the risk of non compliance with the deadline, the risk of failure to achieve the expected performance, the risk of insufficient access to capital, and the risk of conflicts with local residents.
In order to de-risk CSP technology in Tunisia, we propose some strategies, such as strengthening the public-private partnerships, using participatory approaches, creating local employment, etc.
... Secondly, the answers to questions (2) and (3) are analyzed with fault tree analysis to meet the objective-what production risks can be influenced by human factors in production procedures. Fault tree analysis is a popular method to explain how things go wrong in process research (e.g., Amato et al. 2011;Ramesh and Saravannan 2011;Chen and Wang 2017) which is an adequate tool to identify related hazards in complex systems (Lavasani et al. 2015). The weakness of using fault tree analysis to show the influencing network is that only negative influences can be expressed. ...
Thermal power plants are very popular in China. However, there has not been proportional research attention paid to production risk in these plants and human impact on production due to their importance in electricity generation. This study investigates production risks caused by human factors in thermal power plants and management methods to address identified human factors. Eighteen semi-structured interviews with front-line, middle and senior managers from four thermal power plants in China were carried out in this cross-sectional inductive study. Fault tree analysis and causal network analysis are used. We identify a range of production risks and human factors potentially influencing production in both negative and positive ways. We also recognize the most effective and practical relevant management methods to deal with identified human factors. By investigating production risk caused by human factors through the whole production process, this study emphasizes working attitude, safety consciousness, creativity and awareness of environmental protection as essential human factors potentially influencing production risks in thermal power plants. Through our analysis, by linking human factors to different types of production risk and supplying corresponding management methods to address these human factors, we offer practical human resource management approaches in the production management of thermal power plants.
... This has boosted the interest in new maintenance service contracting models (i.e., vendor logistics support, integrated operational support, service by the hour or power by the hour contracts, depending on the industrial field) in which the owner (i.e., who buys GTs from GE to generate revenue) directly buys the availability of the system, rather than the system itself [5]. In business terms, this yields to the owner the advantages of i) transferring the risk of unavailability (e.g., business interruption [6]) to the manufacturer who pays penalties when the performance under contract is not guaranteed, ii) streamlining its own maintenance department, and iii) simplifying the business model, in where there will be a single cost item for the asset management [4]. This situation, i.e., need for maintenance outsourcing and power by the hour contracting, has led to an increasing interest by the owner in the maintenance service contracts offered by the GT manufacturers (i.e., GE), first because it may be the mandatory condition to sell the GTs, and then because it may be an important source of income, with new opportunities arising if GE is able to sell added values by taking over parts of clients' business risks and other (financial) burdens. ...
This article describes a Monte Carlo–based approach for reconstructing missing information in a dataset used by General Electric for reliability analysis, which contains data coming from field observations at inspection of gas turbine components. The approach is based on a combination of maximum likelihood estimation technique to estimate the failure model parameters, Fisher information matrix to estimate the confidence intervals on the estimated parameters, and a double-loop Monte Carlo approach to estimate the missing equivalent starts (i.e. data of turbine state without the relative equivalent starts). The proposed methodology reduces the uncertainty in the estimation of the parameters of the turbine. The results of the application of the novel approach to a real industrial dataset are discussed along with a sensitivity analysis for the quantification of the robustness of the methodology to deal with different sizes of datasets.
... The MSPT demo plant aims to be a showcase for the Molten Salt technology and the Italian supply chain and, at the same time, to demonstrate the manageability, the efficiency and the robustness of such kind of plants that several CSP experts consider to be one of the best ways to decrease Concentrating Solar Power (CSP) plant's Levellized Cost Of Electricity (LCOE) [1,2,3,4,5]. ...
Since July 2013 the first stand-alone Molten Salt Parabolic Trough (MSPT) plant, located adjacent to the Archimede Solar Energy (ASE) manufacturing plant in Massa Martana (Italy), is in operation. After one year of operation, the management of the ASE demonstration plant has shown that MSPT technology is a suitable and reliable option. Several O&M procedures and tests have been performed, always with very good results confirming that this approach can be easily scaled up to realize standard size CSP plants without any concern, if the plant design takes into account molten salt peculiarities. In this paper a brief description of the plant and the overall and main plant operation figures will be presented.
... With regards to the costs of the maintenance actions, these are assumed to be proportional to the unavailability of the component. This situation is typical in plants where main maintenance costs are related to business interruption (e.g., energy production plants, [23], [24]). In this setting, the identification of the best maintenance policy, which is in general a multi-objective optimization problem, comes down to the issue of identifying the policy which minimizes the value of the unavailability. ...
Predictive Maintenance (PrM) exploits the estimation of the equipment Residual Useful Life (RUL) to identify the optimal time for carrying out the next maintenance action. Particle Filtering (PF) is widely used as a prognostic tool in support of PrM, by reason of its capability of robustly estimating the equipment RUL without requiring strict modeling hypotheses. However, a precise PF estimate of the RUL requires tracing a large number of particles, and thus large computational times, often incompatible with the need of rapidly processing information for making maintenance decisions in due time. This work considers two different Risk Sensitive Particle Filtering (RSPF) schemes proposed in the literature, and investigates their potential for PrM. The computational burden problem of PF is addressed. The effectiveness of the two algorithms is analyzed on a case study concerning a mechanical component affected by fatigue degradation.
... According to Stephanopoulos's directives, the simplest control scheme that does the work is the best control scheme [22]. In this case, two proportional-integral flow controllers, PID1 for the solar line and PID2 for the generation line, and a proportional-integral temperature controller, PID3, for the steam generation are implemented to manage the overall system, beyond the relevance to monitor the minimum temperature of molten salts for loss of assets [23]. ...
... Interest in maintenance can be expected to continue increasing in the next future, as the industrial scenario continues to evolve. An example is the development of non-fossil-fuel energy production plants (nuclear, solar, wind, etc.), which is receiving worldwide attention in the last decades (e.g., Amato et al. 2011): maintenance represents a major portion of the total production cost of such technologies, and its optimization can play a role for their competitiveness with respect to fossil-fuel energy production plants. ...
... In regard to the costs of the maintenance actions, these are assumed to be proportional to the unavailability of the component. This situation is typical of the plants where the main maintenance costs are related to the business interruption (e.g., solar energy production plants, Amato et al. 2011, Parker 1993). In this setting, the identification of the best maintenance policy, which is in general a multi-objective optimization problem, comes down to the issue of identifying the policy that minimizes the value of the unavailability. ...
The growing importance of maintenance in the evolving industrial scenario and the technological advancements of the recent years have yielded the development of modern maintenance strategies such as the condition-based maintenance (CBM) and the predictive maintenance (PrM). In practice, assessing whether these strategies really improve the maintenance performance becomes a fundamental issue. In the present work, this is addressed with reference to an example concerning the stochastic crack growth of a generic mechanical component subject to fatigue degradation. It is shown that modeling and analysis provide information useful for setting a maintenance policy.
... Generally speaking, the observation With regards to the costs of the maintenance actions, these are assumed to be proportional to the unavailability of the component. This situation is typical in plants where main maintenance costs are related to business interruption (e.g., energy production plants, [23], [24]). In this setting, the identification of the best maintenance policy, which is in general a multi-objective optimization problem, comes down to the issue of identifying the policy which minimizes the value of the unavailability. ...
Predictive Maintenance (PrM) exploits the estimation of the equipment Residual Useful Life (RUL) to identify the optimal time for carrying out the next maintenance action. Particle Filtering (PF) is widely used as prognostic tool in support of PrM, by reason of its capability of robustly estimating the equipment RUL without requiring strict modeling hypotheses. However, a precise estimate of the RUL requires tracing a large number of particles, and thus large computational times, often incompatible with the need of rapidly processing information for making decisions in due time. To circumvent this problem, the Risk Sensitive Particle Filtering (RSPF) technique is exemplified in this work by way of a case study concerning a mechanical component affected by fatigue degradation.
In this paper, results of a thermal-hydraulic analysis of a linear Fresnel solar collector loop using molten salt or liquid metals as heat transfer fluid are presented. The purpose of this study is to compare the benefits and challenges of using liquid metals (e.g. sodium) or molten salts (e.g. solar salt) as heat transfer fluid into line focusing Solar Thermal Electric plants. Similar studies have been conducted for point focussing Solar Thermal Electric plants but line focussing plants have not been thoroughly investigated yet. After reviewing and comparing the main thermo-physical properties of sodium and solar salt, results from thermal-hydraulic simulations, using the best-estimate system code TRACE from the US Nuclear Regulatory Commission, are presented for various plant operation scenarios. The results show that sodium offers several advantages over solar salt when used as heat transfer fluid, among which: wider operation temperature range, faster start-up procedures, quicker response of the control system and ultimately potentially higher energy yield, mostly thanks to its hundredfold higher thermal conductivity. These benefits may result in increased interest into this technological concept and might lead to further developments of Solar Thermal Electric plant design with reduced levelised cost of electricity generation.
Concentrating solar power (CSP) provides the ability to incorporate simple, efficient, and cost-effective thermal energy storage (TES) by virtue of converting sunlight to heat as an intermediate step to generating electricity. Thermal energy storage for use in CSP systems can be one of sensible heat storage, latent heat storage using phase change materials (PCMs) or thermochemical storage. Commercially deployed CSP TES systems have been achieved in recent years, with two-tank TES using molten salt as a storage medium and steam accumulators being the system configurations deployed to date. Sensible energy thermocline systems and PCM systems have been deployed on a pilot-scale level and considerable research effort continues to be funded, by the United States Department of Energy (DOE) and others, in developing TES systems utilizing any one of the three categories of TES. This paper discusses technoeconomic challenges associated with the various TES technologies and opportunities for advancing the scientific knowledge relating to the critical questions still remaining for each technology.
