Steam Generation Solar Power Plant Research Articles

Assessing parabolic trough collectors and linear Fresnel reflectors direct steam generation solar power plants in Northwest México

Concentrating solar power (CSP) systems offer promising solutions for harnessing solar energy. Parabolic trough collectors (PTC) are prevalent in CSP, but direct steam generation (DSG) in solar fields is an innovative alternative that eliminates the need for thermal oils. This study compares EuroTrough PTC and optimized linear Fresnel reflector (LFR) geometries for DSG for Mexican operating conditions. Two 10 MW Rankine cycles with two and three steam extractions are considered. The study evaluates 16 solar field configurations capable of delivering 400 °C superheated steam at 100 bar. Assessment parameters include effective concentration area, nominal loop inlet pressure, energy and exergy efficiency, and hypothetical thermal storage size. The findings strongly favor PTC solar fields with 14 loops, exhibiting superior performance. However, three-loop LFR configurations are suggested where pressure reduction prevails. Three-loop LFR arrays minimize land utilization for spatially constrained installations, while larger five-loop configurations optimize efficiency. Employing 14 PTC loops prioritizes thermal energy storage. In contrast, 8 PTC loops maximize storage capacity. The study underscores the advantages of Fresnel reflectors over parabolic troughs in specific scenarios, presenting avenues for future exploration. This analysis lays the groundwork for assessing these technologies in the distinctive context of Mexican operations, offering valuable insights into sustainable energy applications.

Thermodynamic and exergoeconomic operation optimization and simulation of steam generation solar power plant

Thermodynamic and exergoeconomic operation optimization and simulation of steam generation solar power plant

Energy and Exergy (2E) Analysis of an Optimized Solar Field of Linear Fresnel Reflectors for a Conceptual Direct Steam Generation Power Plant

Direct steam generation is a promising alternative to conventional heat transfer fluids for solar thermal power plants using linear concentrators because water and steam do not have thermal and chemical stability problems. The novelty of this study, an energy and exergy (2E) analysis, was that it was performed on several configurations of a conceptual direct steam generation solar power plant with optimized Fresnel reflectors in Agua Prieta, Mexico coupled with a regenerative steam Rankine power cycle to quantify their efficiency and establish a reference for future implementation of this technology in concentrated solar power plants in Mexico. The thermal model was assumed to be a 1D steady-state flow and validated against results in the literature. It was then applied directly to a case study to determine the size of the solar field. The design point was the lowest solar irradiance day, and evaluating the solar multiple with the highest solar irradiance, taking care not to oversize the solar field, as suggested for solar plants without energy storage. Comparing the performance of the optimized Fresnel field against the FRESDEMO field of Plataforma Solar de Almería, a considerable decrease in the length of the loop has been demonstrated with a low reduction in thermal efficiency.

Development and application of a multi-domain dynamic model for direct steam generation solar power plant

Direct Steam Generation (DSG) concentrated solar plants are promising but complex power systems. This latter feature originates both from the variety of physical phenomena and the dynamic nature of the boundary conditions at play during plant operation. A representative yet computationally efficient numerical simulator is a valuable tool to assist engineers in the proper design, control and operation of such specific water-steam cycle. The present communication reports on the development of a multi-domain dynamic model representing a DSG plant. To do so, we followed a code-coupling approach and relied on the domain-decomposition paradigm. More specifically, we built three sub-models respectively in the thermal-hydraulic, the optical and the control-command domains and coupled them through an in-house co-simulation platform called PEGASE. We used the CATHARE system code to solve the thermal-hydraulic problem and the more generalist DYMOLA software to model the convective and radiative heat exchanges within the solar receiver. As an example, we then applicate the simulator to elaborate an efficient controller for the steam separator level.

Transient performance of direct steam generation solar power plants

Summary Parabolic trough power plants are currently the most commercial systems for electricity generation. In this study, a transient numerical simulation of a solar power plant was developed by using direct steam generation (DSG) technology. In this system, condensate water from a Rankine cycle is pumped directly to solar parabolic trough collectors. The pressurized water is heated and evaporated before being superheated inside the solar collectors and directed back to the steam turbines, where the Rankine cycle is a reheated-regenerative cycle. The plant performance with saturated steam production is compared with the performance of a superheated plant. A mathematical model of each system component is presented, with the solar power cycle modeled by the TRNSYS-17 simulation program. Annual transient performance, including plant power and efficiency, is presented for both plants. As expected, the power of the superheated plant outperforms the saturated plant by approximately 45%, whereas the efficiency decreases by approximately 10%. Furthermore, the power of such plants is considerably improved under the weather of Makkah, 22.4°N, and it is approximately 40 MW for both the spring and autumn seasons. The annual generated energy is approximately 8062 MWh. The levelized electricity cost (LEC) was estimated for both the DSG and the corresponding synthetic oil plants. The DSG plant has an approximately 3% higher LEC than a synthetic oil plant with heat storage and an approximately 11.2% lower LEC than an oil plant if the plant has no storage. Copyright © 2016 John Wiley & Sons, Ltd.

Exergy and exergoeconomic analysis of sustainable direct steam generation solar power plants

Solar direct steam generation is considered as a promising technology for steam production in thermal power generation due to high temperature levels that can be achieved compared to other technologies that use indirect steam generation. This paper demonstrates exergy and exergoeconomic analysis of commercial-size direct steam generation parabolic trough solar thermal power plant. For steam power cycles, reheating might be necessary to avoid great wetness of steam which shortens the lifetime of the turbines. Therefore, two configurations have been considered in this study; the non-reheating configuration as well as reheating by steam–steam heat exchanger. For each component, exergy and exergy-costing balance equations have been formulated based on a proper definition of fuel–product–loss. Exergy results show that particular attention should be paid to solar field, condenser, low pressure turbine and high pressure turbine (in a descendant order) as they constitute the major sources of exergy destruction. Results from exergoeconomic analysis, however, show that the condenser should be the fourth component in the order of importance after the solar field and low/high pressure turbines. Increasing the temperature at the inlet of the low pressure turbine by 100K using steam–steam reheating is shown to result in 9.1% increase in the vapor fraction at the exit of turbine. This increase in steam quality, however, would be achieved by drop less than 1.5% in thermal and exergetic efficiencies, and about 2% increase in cost of electricity. Moreover, the effect of degree of reheating on exergetic exergoeconomic parameters has been investigated. The results revealed that there is a specific value of degree of reheating for which the exergetic efficiency would be on it’s lowest value. This point would be of importance during optimization procedure of reheating direct steam generation solar plants.

Analytical modeling of direct steam generation solar power plants

Analytical models for the physical processes governing direct steam generation line-focus solar thermal power plants are derived. Predictions compare favorably with the limited database available from published studies against which the accuracy of detailed model computations can meaningfully be assessed. That limited database should not be confused with extensive citations of system power delivery in the absence of comprehensive information. A physically transparent understanding is provided for heat transfer within the collectors, heat loss to ambient, fluid flow and steam cycle efficiency. With existing evacuated-tube parabolic-trough concentrators and steam turbines, net system conversion efficiencies can exceed 20% even for today’s small-scale (⩽100MW) power plants. A key limiting factor is that relatively low-power turbines inherently have poorer isentropic efficiencies than their high-power counterparts. Although a few strategies for improving system efficiency have previously been proposed, the analytical models presented here provide the ability to rapidly (a) quantify the performance advantages of these strategies and (b) project how assorted modifications should affect system behavior, in both cases, without the need for expansive simulations. Examples of these design options include (1) multiple fluid extractions in a regenerative turbine cycle, (2) higher isentropic efficiencies for larger turbines, and (3) raising cycle temperature.

Steam temperature stability in a direct steam generation solar power plant

Direct steam generation (DSG) is one alternative to the current oil-based parabolic trough solar thermal power plants. Within the German research project ITES, the dynamic behavior of a DSG collector field and the interactions with the conventional power block are assessed in detail. A transient solar field model developed by DLR is used to simulate the steam temperature behavior. Artificial irradiance disturbances as well as real irradiance data are used as input to the system. The resulting main steam temperature gradients are then analyzed by Siemens considering the standards for steam turbines. This paper presents the transient simulation results of the steam temperature as well as the corresponding results of the steam turbine analysis. It is found that the occurring temperature gradients are challenging for a safe turbine operation, if a conservative control system is used. Therefore, the use of an additional thermal inertia to stabilize the steam temperature is suggested. Its impact is also analyzed and discussed in this paper.

A Direct Steam Generation Solar Power Plant With Integrated Thermal Storage

For the future market potential of parabolic trough power plants with direct steam generation (DSG), it is beneficial to integrate a thermal storage system. Heat storage media based on phase change materials offer heat transfer at constant temperatures needed for the evaporation process. Different options for a plant layout are presented and discussed. The interactions between the three subsystems—solar field, power block, and thermal storage—are analyzed, and boundary conditions arising from the thermal storage system are identified. Compared with a system without storage the number of operating points increases significantly since different combinations of storage charge and discharge operations go along with a varying power output of the solar field. It is shown that the large number of theoretical operating points can be reduced to a subset with practical relevance. Depending on the live steam parameters a reheat is necessary within the power block. Compared with parabolic trough fields with a single phase heat transfer medium such as oil, a special heat exchanger configuration is needed for a DSG plant. Different alternatives based on available technologies are presented and evaluated.