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Concept: Concentrating solar power


Decisions determining the use of land for energy are of exigent concern as land scarcity, the need for ecosystem services, and demands for energy generation have concomitantly increased globally. Utility-scale solar energy (USSE) [i.e., ≥1 megawatt (MW)] development requires large quantities of space and land; however, studies quantifying the effect of USSE on land cover change and protected areas are limited. We assessed siting impacts of >160 USSE installations by technology type [photovoltaic (PV) vs. concentrating solar power (CSP)], area (in square kilometers), and capacity (in MW) within the global solar hot spot of the state of California (United States). Additionally, we used the Carnegie Energy and Environmental Compatibility model, a multiple criteria model, to quantify each installation according to environmental and technical compatibility. Last, we evaluated installations according to their proximity to protected areas, including inventoried roadless areas, endangered and threatened species habitat, and federally protected areas. We found the plurality of USSE (6,995 MW) in California is sited in shrublands and scrublands, comprising 375 km(2) of land cover change. Twenty-eight percent of USSE installations are located in croplands and pastures, comprising 155 km(2) of change. Less than 15% of USSE installations are sited in “Compatible” areas. The majority of “Incompatible” USSE power plants are sited far from existing transmission infrastructure, and all USSE installations average at most 7 and 5 km from protected areas, for PV and CSP, respectively. Where energy, food, and conservation goals intersect, environmental compatibility can be achieved when resource opportunities, constraints, and trade-offs are integrated into siting decisions.

Concepts: Sun, Solar cell, Photovoltaics, Solar energy, Solar power, Nuclear power, Solar thermal energy, Concentrating solar power


Land-cover change from energy development, including solar energy, presents trade-offs for land used for the production of food and the conservation of ecosystems. Solar energy plays a critical role in contributing to the alternative energy mix to mitigate climate change and meet policy milestones; however, the extent that solar energy development on nonconventional surfaces can mitigate land scarcity is understudied. Here, we evaluate the land sparing potential of solar energy development across four nonconventional land-cover types: the built environment, salt-affected land, contaminated land, and water reservoirs (as floatovoltaics), within the Great Central Valley (CV, CA), a globally significant agricultural region where land for food production, urban development, and conservation collide. Furthermore, we calculate the technical potential (TWh year-1) of these land sparing sites and test the degree to which projected electricity needs for the state of California can be met therein. In total, the CV encompasses 15% of CA, 8415 km2 of which was identified as potentially land-sparing for solar energy development. These areas comprise a capacity-based energy potential of at least 17 348 TWh year-1 for photovoltaic (PV) and 2213 TWh year-1 for concentrating solar power (CSP). Accounting for technology efficiencies, this exceeds California’s 2025 projected electricity demands up to 13 and 2 times for PV and CSP, respectively. Our study underscores the potential of strategic renewable energy siting to mitigate environmental trade-offs typically coupled with energy sprawl in agricultural landscapes.

Concepts: Energy, Solar cell, Photovoltaics, California, Renewable energy, Solar energy, Solar thermal energy, Concentrating solar power


Solar steam generation is one of the most promising solar-energy-harvesting technologies to addressing the issue of water shortage. Despite intensive efforts to develop high-efficiency solar steam generation devices, challenges remain in terms of the relatively low solar thermal efficiency, complicated fabrications, high cost, and difficulty in scaling up. Herein, a double-network hydrogel with a porous structure (p-PEGDA-PANi) is demonstrated for the first time as a flexible, recyclable and efficient photothermal platform for low-cost and scalable solar steam generation. As a novel photothermal platform, the p-PEGDA-PANi involves all necessary properties of efficient broadband solar absorption, exceptional hydrophilicity, low heat conductivity and porous structure for high-efficiency solar steam generation. As a result, the hydrogel-based solar steam generator exhibits a maximum solar thermal efficiency of 91.5% with an evaporation rate of 1.40 kg m-2 h-1 under one-sun illumination, comparable to state-of-the-art solar steam generation devices. Furthermore, the good durability and environmental stability of p-PEGDA-PANi hydrogel enables a convenient recycling and reusing process toward real life applications. The present research not only provides a novel photothermal platform for solar energy harvest, but also opens a new avenue for application of the hydrogel materials in solar steam generation.

Concepts: Sun, Photovoltaics, Energy conversion, Recycling, Solar energy, Evaporation, Solar thermal energy, Concentrating solar power


In this communication, a concentrated solar light (CSL) annealing strategy is proposed with a Fresnel lens as the concentrator for rapid and effective crystallization of nanomaterials. More interestingly, the CSL can be integrated into photoelectrochemical devices and achieved an unprecedented photocurrent density.

Concepts: Light, Photoelectric effect, Lens, Magnifying glass, Concentrating solar power, Augustin-Jean Fresnel, Fresnel lens, Solar forge


The ability to modulate the conductance of an electronic device under light irradiation is crucial to the practical applications of nanoscale electronics. Density functional theory calculations predict that the conductance of the photo-responsive graphene-based nanocomposites can be tuned through the noncovalent adsorption of an azobenzene (AB) derivative onto pristine, Si-doped, and pyridine-like N3-vacancy graphene. AB@graphene systems were found to exhibit a visible-light response within the low-frequency region, rendering the trans-to-cis isomerizations of these nanocomposites under the irradiation of solar light. The excellent solar light absorption performances of these hybrids can then be used to modulate the conductance of both N3-vacancy- and Si-doped-graphene AB hybrids effectively through the reversible change of the effective conjugate length of the AB molecule in the photoisomerization. In addition, the solar thermal energy up to 1.53 eV per AB molecule can be stored in the designed nanocomposites with the doped graphene. These findings provide clues for making multifunctional materials with potential applications as both optically controlled nanoelectronics and solar energy storage devices.

Concepts: Energy, Sun, Kinetic energy, Photovoltaics, Solar energy, Energy storage, Solar thermal energy, Concentrating solar power


Concentrating solar power plants (CSPPs) are considered to be particularly respectful of the environment but under Mediterranean climate where surface water scarcity is a key issue, these types of electrical plants usually require groundwater for their cooling towers and use the same aquifers to discharge their salinized effluents. This study analyses de Spanish case, where fifteen out of the fifty active CSPPs use groundwater directly, four discharge their effluents to infiltration ponds and forty-three to surface watercourses most of which recharge underlying aquifers. The volume of water withdrawn and discharged varies greatly among similar plants. The salinity of the effluent exceeds 2.5 times that of the withdrawn water in half of the plants and it may alter the current or potential use of the water turning it unsuitable for drinking or even for irrigation. There is a risk that the impact on groundwater can be extended to related ecosystems such as wetlands. This can become a serious environmental problem, but specific impacts on groundwater are often overlooked in environmental impact assessments of CSPPs and no research on the matter has been reported so far. Other legal and political implications of CSPPs are further discussed.

Concepts: Water, Water pollution, Hydrology, Aquifer, Irrigation, Environmental science, Solar energy, Concentrating solar power


This article presents technical data for concentrated solar power (CSP) plants in operation, under construction and in project all over the world in the form of tables. These tables provide information about plants (e.g., name of the CSP plant, country of construction, owner of the plant, aim of the plant) and their technical characteristics (e.g., CSP technology, solar power, area of the plant, presence and type of hybridization system, electricity cost, presence and type of TES, power cycle fluid, heat transfer fluid, operating temperature, operating pressure, type of turbine, type and duration of storage, etc.). Further interpretation of the data and discussions on the current state-of-the-art and future trends of CSP can be found in the associated research article (Pelay et al., 2017) [1].

Concepts: Solar energy, Solar power, Solar thermal energy, Concentrating solar power, Solar Energy Generating Systems, Solar thermal, PS10 solar power tower, Heliostat


Volumetric solar thermal conversion is an emerging technique for a plethora of applications such as solar thermal power generation, desalination, and solar water splitting. However, achieving broadband solar thermal absorption via dilute nanofluids is still a daunting challenge. In this work, full-spectrum volumetric solar thermal conversion is demonstrated over a thin layer of the proposed ‘photonic nanofluids’. The underlying mechanism is found to be the photonic superposition of core resonances, shell plasmons, and core-shell resonances at different wavelengths, whose coexistence is enabled by the broken symmetry of specially designed composite nanoparticles, i.e., Janus nanoparticles. The solar thermal conversion efficiency can be improved by 10.8% compared with core-shell nanofluids. The extinction coefficient of Janus dimers with various configurations is also investigated to unveil the effects of particle couplings. This work provides the possibility to achieve full-spectrum volumetric solar thermal conversion, and may have potential applications in efficient solar energy harvesting and utilization.

Concepts: Energy, Sun, Photovoltaics, Energy conversion, Solar energy, Nuclear power, Solar thermal energy, Concentrating solar power


We investigate the optical properties of LaB6 - based materials, as possible candidates for solid absorbers in Concentrating Solar Power (CSP) systems. Bulk LaB6 materials were thermally consolidated by hot pressing starting from commercial powders. To assess the solar absorbance and spectral selectivity properties, room-temperature hemispherical reflectance spectra were measured from the ultraviolet to the mid-infrared, considering different compositions, porosities and surface roughnesses. Thermal emittance at around 1100 K has been measured. Experimental results showed that LaB6 can have a solar absorbance comparable to that of the most advanced solar absorber material in actual plants such as Silicon Carbide, with a higher spectral selectivity. Moreover, LaB6 has also the appealing characteristics to be a thermionic material, so that it could act at the same time both as direct high-temperature solar absorber and as electron source, significantly reducing system complexity in future concentrating solar thermionic systems and bringing a real innovation in this field.

Concepts: Sun, Solar cell, Photovoltaics, Solar energy, Solar power, Solar thermal energy, Concentrating solar power, Lanthanum hexaboride


This study shows an analysis of the stability of nanofluids based on the eutectic mixture of diphenyl oxide and biphenyl, used as a heat transfer fluid (HTF) in concentrating solar energy, and NiO nanoparticles. Two surfactants were used to analyze the stability of the nanofluids: Benzalkonium Chloride (BAC) and 1-Octadecanethiol (ODT). From an experimental perspective, the stability was analyzed using UV-vis spectroscopy, particle size measurements using the dynamic light scattering technique and  potential measurements. The results show that the stability of the nanofluids improved with the use of BAC. DFT calculations were performed to understand the role played by the surfactants. A study was performed into the interaction of the surfactants with both the fluid and the NiO (100) surface. The QTAIM analysis showed that hydrogen bridge interactions favor the stability of the fluid-surfactant mixture. The more stabilizing NiO-surfactant interaction involves the Ni-H interaction of the -SH and -CH3 groups of the ODT and BAC. Also, nanofluids with BAC is favored over that with ODT, which is in agreement with the experimental results. The structural and electronic effects of incorporating the surfactant onto the NiO (100) surface are shown using ELF analysis, the non-covalent interaction (NCI) index and PDOS.

Concepts: Spectroscopy, Scattering, Scientific techniques, Colloidal chemistry, Solar energy, Light scattering, Dynamic light scattering, Concentrating solar power