A Methodology for Determining Optimum Solar Tower Plant Configurations and Operating Strategies to Maximize Profits Based on Hourly Electricity Market Prices and Tariffs

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Parabolic trough power plants using thermal oil as heat transfer fluid are the most mature concentrating solar power technology and state of the art. To further increase their efficiency and lower costs, molten salts can be used as heat transfer fluid. This results in higher operating temperature differences for improved cycle efficiencies and enables direct thermal energy storage at lower costs due to omission of the oil-to-salt heat exchanger and the need for smaller storage sizes. As a variety of salts are available to choose from, this study uses a multi-objective optimization to identify the most suitable heat transfer fluid for three locations in South Africa, Spain and Chile. The lowest values for the levelized costs of electricity (LCOE) can be found in Chile using Solar Salt as heat transfer fluid (75.0 $/MWhe). Generally, Solar Salt offers the lowest LCOE values followed by thermal oil and Hitec. The results also suggest that the choice of the heat transfer fluid is dependent on the direct normal irradiance (DNI) at each location. Thermal oil is competitive with Solar Salt in small systems at locations with low DNI values, whereas Hitec can be cheaper than thermal oil in large systems at locations with high DNI. Furthermore, it is also investigated at which freeze alert temperature set point the activation of the freeze protection system is optimal. The results indicate that this temperature should be chosen close to the solar field inlet temperature for small systems, while it can be lowered significantly for large systems to reduce electricity consumption from the freeze protection system.

Section: Methodsmentioning

confidence: 99%

Section: Multi-objective Optimizationmentioning

confidence: 99%

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Identification of optimum molten salts for use as heat transfer fluids in parabolic trough CSP plants. A techno-economic comparative optimization

Pan¹,

Ferruzza²,

Guédez³

et al. 2018

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“…070002-1 energy storage given that prior studies [9] have shown that, for certain market conditions, the most profitable operating strategies imply an increased amount of annual starts in order to peak the operation of the plant during the highest electricity prices. As such, in the interest of improving the annual performance and competitiveness of parabolic trough CSP plants, it is desirable to achieve fast start-up times to harness the solar energy as soon as possible.…”

Section: Introductionmentioning

confidence: 99%

Analysis of plant performance with improved turbine flexibility: Test case on a parabolic trough configuration

Topel

Ferruzza

Seeger

et al. 2018

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Parabolic trough configurations account for 95% of the current installed concentrating solar power (CSP) capacity. Certainly this technology is considered as the most mature among other CSP types. However, regardless of its maturity, the pursuit of cost competitiveness with respect to fossil fuels and other renewables is still a dire need. One way to maximize profitability and improve performance is flexibility through fast starts. In this regard, the steam turbine has been identified as a key limiting component to the start-up process. This work focuses on analyzing the influence of steam turbine start-up parameters on the overall annual performance of a CSP plant. For this, a detailed parabolic trough power plant (PTPP) performance model was developed including a control strategy to account for turbine transient start-up constraints. The PTPP model was developed in accordance to the latest state-of-the-art of the technology. As such, the first part of the results consisted of validation studies of the model with respect to the actual power plant. The results obtained in this regard showed that the model correlates to the rated performance of the power plant with maximum errors of 12% and of 14% to the dynamic operation of the power plant. The second part of this work consisted of using the validated model in a series of sensitivity studies concerning the variation of different turbine start-up parameters. Results showed that improvements of up to 1.8% in the annual electricity production are possible with only 0.3% increase in fuel consumption.

“…In addition the steam generation components, evaporator (EV), super-heater (SH) and re-heater (RH), form the central receiver at the top the tower. The main design parameters and configuration specifications of the DSG-STPP used as the base case for this work are shown in TABLE 1 . For the purpose of the studies carried out in this work, the fact that the selected plant configuration does not comprise thermal energy storage serves to observe the impact and value of operational flexibility more clearly for each of the flexibility scenarios considered.…”

Section: Power Plant Techno-economic Modelmentioning

confidence: 99%

Towards prioritizing flexibility in the design and construction of concentrating solar power plants

Topel

Lundqvist

Haglind

et al. 2017

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Abstract. In the operation and maintenance of concentrating solar power plants, high operational flexibility is required in order to withstand the variability from the inherent solar fluctuations. However, during the development phases of a solar thermal plant, this important objective is overlooked as a relevant factor for cost reduction in the long term. This paper will show the value of including flexibility aspects in the design of a concentrating solar power plant by breaking down their potential favorable impact on the levelized cost of electricity (LCOE) calculations. For this, three scenarios to include flexibility as a design objective are analyzed and their potential impact on the LCOE is quantified. The scenarios were modeled and analyzed using a techno-economic model of a direct steam generation solar tower power plant. Sensitivity studies were carried out for each scenario, in which the level of improvement due to each scenario was compared to the base case. Then, the results obtained for each scenario were compared for similar levels of LCOE and flexibility improvements. In general, all scenarios were beneficial on power plant performance. Improvements on the LCOE in the range of 3-4% were obtained with different distributions of costs and annual electricity for each case.