Development of a Simple Methodology Using Meteorological Data to Evaluate Concentrating Solar Power Production Capacity, A. M. Tavares, R. Conceição, F. M. Lopes, H. G.Silva, Energies, 15, 7693, 2022, Online version, https://doi.org/10.3390/en15207693

Abstract

Evaluation of the Concentrating Solar Power capacity factor is critical to support decision making on possible regional energy investments. For such evaluations, the System Advisor Model is used to perform capacity factor assessments. Among the required data, information concerning direct normal irradiance is fundamental. In this context, the Engerer model is used to estimate direct normal irradiance hourly values out of global horizontal irradiance ground measurements and other observed meteorological variables. Model parameters were calibrated for direct normal irradiance measurements in Évora (Southern Portugal), being then applied to a network of 90 stations, part of the Portuguese Meteorological Service. From the modelled direct normal irradiance, and for stations that comprise 20 years of data, typical meteorological years were determined. Finally, to identify locations of interest for possible installations of Concentrating Solar Power systems, annual direct normal irradiance availabilities and the respective capacity factor, for a predefined power plant using the System Advisor Model, were produced. Results show annual direct normal irradiance availabilities and capacity factors of up to ~2310 kWh/m² and ~36.2% in Castro Marim and in Faro, respectively. Moreover, this study supports energy policies that would promote Concentrating Solar Power investments in Southern Portugal (Alentejo and Algarve regions) and eastern centre Portugal (Beira Interior region), which have capacity factors above 30%.

Experimental evaluation and energy analysis of a two-step water splitting thermochemical cycle for solar hydrogen production based on La_0.8Sr_0.2CoO_3-δ perovskite, M. Orfila, M. Linares, A. Pérez, I. Barras-García, R. Molina, J. Marugán, J.A. Botas, R. Sanz, International Journal of Hydrogen Energy, 47, 41209-41222, 2022, Online version, https://doi.org/10.1016/j.ijhydene.2022.03.077

Abstract

A study of the hydrogen production by thermochemical water splitting with a commercial perovskite La_0.8Sr_0.2CoO_3-δ(denoted as LSC) under different temperature conditions is presented. The experiments revealed that high operational temperatures for the thermal reduction step (>1000 °C) implied a decrease in the hydrogen production with each consecutive cycle due to the formation of segregated phases of Co₃O₄. On the other hand, the experiments at lower thermal reduction operational temperatures indicated that the material had a stable behaviour with a hydrogen production of 15.8 cm³ STP/g_material·cycle during 20 consecutive cycles at 1000 °C, being negligible at 800 °C. This results comparable or even higher than the maximum values reported in literature for other perovskites (9.80–10.50 STP/g_material·cycle), but at considerable lower temperatures in the reduction step of the thermochemical cycle for the water splitting (1000 vs 1300–1400 °C). The LSC keeps the perovskite type structure after each thermochemical cycle, ensuring a stable and constant H₂ production. An energy and exergy evaluation of the cycle led to values of solar to fuel efficiency and exergy efficiency of 0.67 and 0.36 (as a percentage of 1), respectively, which are higher than those reported for other metal oxides redox pairs commonly found in the literature, being the reduction temperature remarkably lower. These facts point out to the LSC perovskite as a promising material for full-scale applications of solar hydrogen production with good cyclability and compatible with current concentrating solar power technology.

Editorial: Recent Advances in Solar-Driven Thermochemical Fuel Production and Thermal Energy Storage, A. J. Carrillo, A. Bayon, J. M. Coronado, E. Mastronardo, Frontiers in Energy Research, 10, 885894, 2022, Online version, https://doi.org/10.3389/fenrg.2022.885894

Soiling effect in solar energy conversion systems: A review, R. Conceição, J. González-Aguilar, A. A. Merrouni, M. Romero, Renewable and Sustainable Energy Reviews, 162, art. no. 112434, 2022, Online version, https://doi.org/10.1016/j.rser.2022.112434

Abstract

This review provides a comprehensive, detailed description and contextualization of soiling research evolution in the solar energy field throughout time. The analysis consists of past soiling research, including important notes on notable works and main researches. The current state of the art is presented, followed by an extended literature survey covering from 1942 to 2019, facilitating the finding of primordial research concerning each of the available technologies, and enriching knowledge regarding the existing extensive research database. Moreover, soiling analysis and comments are made for several specific topics, such as cleaning techniques and environmental effects on soiling deposition. Finally, future prospects and research directions on the soiling effect are given.

Optical and thermal integration analysis of supercritical CO2 Brayton cycles with a particle-based solar thermal plant based on annual performance, R. Chen, M. Romero, J. González-Aguilar, F. Rovense, Z. Rao, S. Liao, Renewable Energy, 189, 164-179, 2022, Online version, https://doi.org/10.1016/j.renene.2022.02.059

Abstract

Central receiver concentrating solar power (CSP) plants based on particles as heat transfer fluid in solar circuits and supercritical CO₂ (S–CO₂) Brayton cycles can fulfil the requirements for next generation CSP to improve solar-to-electric efficiency and reduce energy storage costs. However, effective incorporation of these two concepts requires an in-depth understanding of their characteristics and an appropriate approach to match them. This paper addresses the importance of the design features and annualized performances of the optical subsystem (heliostat-receiver) and the thermal-to-electricity subsystem (solar receiver-energy storage-power block) on the global optimization of any integrated CSP plant. The analysis lies in a complete model of a particle-based CSP plant, which includes detailed modeling for the solar field, a cavity solar receiver with an up bubbling fluidized bed (UBFB) tubular panel, particles storage tanks and a recompression S–CO₂ Brayton cycle. The design incident irradiance on the receiver aperture (IR) and the particles temperature at the receiver outlet (T_p) are identified as key parameters determining the solar-to-electric integration procedure and affecting the overall plant design and annual performance. Regarding subsystems located upstream and downstream of the receiver, the effects of heliostat and power block characteristics on the optimal IR and T_p are also evaluated, represented by the heliostat beam quality and main compressor inlet temperature. Results show that IR around 1,200–1,500 W/m² provides the maximum system design efficiency and annual efficiency. Improvements on heliostat beam quality and power block efficiency help to increase the optimal IR and overall system efficiency. In the optimal range of IR, increasing T_p leads to higher system design efficiency, but lower system annual efficiency and annual electricity output. The optimal combination of IR and T_p contributes to a minimum heliostat design area, representing the integration trade-off between the system optical and thermal characteristics.