Techno-Economic Analysis of a Concentrating Solar Power Plant Using Redox-Active Metal Oxides as Heat Transfer Fluid and Storage Media

We present results for a one-dimensional quasi-steady-state thermodynamic model developed for a 111.7 MWe concentrating solar power (CSP) system using a redox-active metal oxide as the heat storage media and heat transfer agent integrated with a combined cycle air Brayton power block. In the energy charging and discharging processes, the metal oxide CaAl0.2Mn0.8O2.9-δ (CAM28) undergoes a reversible, high temperature redox cycle including an endothermic oxygen-releasing reaction and exothermic oxygen-incorporation reaction. Concentrated solar radiation heats the redox-active oxide particles under partial vacuum to drive the reduction extent deeper for increased energy density at a fixed temperature, thereby increasing storage capacity while limiting the required on sun temperature. Direct counter-current contact of the reduced particles with compressed air from the Brayton compressor releases stored chemical and sensible energy, heating the air to 1,200°C at the turbine inlet while cooling and reoxidizing the particles. The cool oxidized particles recirculate through the solar receiver subsystem for another cycle of heating and reduction (oxygen release). We applied the techno-economic model to 1) size components, 2) examine intraday operation with varying solar insolation, 3) estimate annual performance characteristics over a simulated year, 4) estimate the levelized cost of electricity (LCOE), and 5) perform sensitivity analyses to evaluate factors that affect performance and cost. Simulations use hourly solar radiation data from Barstow, California to assess the performance of a 111.7 MWe system with solar multiples (SMs) varying from 1.2 to 2.4 and storage capacities of 6–14 h. The baseline system with 6 h storage and SM of 1.8 has a capacity factor of 54.2%, an increase from 32.3% capacity factor with no storage, and an average annual energy efficiency of 20.6%. Calculations show a system with an output of 710 GWhe net electricity per year, 12 h storage, and SM of 2.4 to have an installed cost of $329 million, and an LCOE of 5.98 ¢/kWhe. This value meets the U.S. Department of Energy’s SunShot 2020 target of 6.0 ¢/kWhe (U. S Department of Energy, 2012), but falls just shy of the 5.0 ¢/kWhe 2030 CSP target for dispatchable electricity (U. S Department of Energy, 2017). The cost and performance results are minimally sensitive to most design parameters. However, a one-point change in the weighted annual cost of capital from 8 to 7% (better understood as a 12.5% change) translates directly to an 11% decrease (0.66 ¢/kWhe) in the LCOE.

Redox-Active Metal Ions and Amyloid-Degrading Enzymes in Alzheimer’s Disease

Redox-active metal ions, Cu(I/II) and Fe(II/III), are essential biological molecules for the normal functioning of the brain, including oxidative metabolism, synaptic plasticity, myelination, and generation of neurotransmitters. Dyshomeostasis of these redox-active metal ions in the brain could cause Alzheimer’s disease (AD). Thus, regulating the levels of Cu(I/II) and Fe(II/III) is necessary for normal brain function. To control the amounts of metal ions in the brain and understand the involvement of Cu(I/II) and Fe(II/III) in the pathogenesis of AD, many chemical agents have been developed. In addition, since toxic aggregates of amyloid-β (Aβ) have been proposed as one of the major causes of the disease, the mechanism of clearing Aβ is also required to be investigated to reveal the etiology of AD clearly. Multiple metalloenzymes (e.g., neprilysin, insulin-degrading enzyme, and ADAM10) have been reported to have an important role in the degradation of Aβ in the brain. These amyloid degrading enzymes (ADE) could interact with redox-active metal ions and affect the pathogenesis of AD. In this review, we introduce and summarize the roles, distributions, and transportations of Cu(I/II) and Fe(II/III), along with previously invented chelators, and the structures and functions of ADE in the brain, as well as their interrelationships.

Interaction of Melanin with Metal Ions Modulates Their Cytotoxic Potential

Melanin is one the most common biological pigments. In humans, specialized cells called melanocytes synthesize the pigment from tyrosine and 3,4-dihydroxyphenylalanine via enzyme-catalyzed reactions and spontaneous processes. The formed melanin granule consists of nanoaggregates of oligomers containing different monomers. Although the main biological function of melanin is protection against damage from solar radiation, melanin may also be involved in protection against oxidative stress. In the latter function, sequestration of redox-active metal ions and scavenging of reactive oxygen species are of importance. The paper reviews basic physicochemical properties of melanin responsible for binding of metal ions and discusses specific conditions that may induce cytotoxicity of metal ions such as iron and copper by facilitating their redox activation and release from melanin. While the value of EPR spectroscopy and other EPR-related techniques for the study of melanin is emphasized, the concomitant use of other physicochemical methods is the most efficient approach.

The Relevance of Plant-Derived Se Compounds to Human Health in the SARS-CoV-2 (COVID-19) Pandemic Era

Dietary selenium (Se)-compounds accumulated in plants are essential for human metabolism and normal physiological processes. Inorganic and organic Se species can be readily absorbed by the human body, but are metabolized differently and thus exhibit distinct mechanisms of action. They can act as antioxidants or serve as a source of Se for the synthesis of selenoproteins. Selenocysteine, in particular, is incorporated at the catalytic center of these proteins through a specific insertion mechanism and, due to its electronic features, enhances their catalytic activity against biological oxidants. Selenite and other Se-organic compounds may also act as direct antioxidants in cells due to their strong nucleophilic properties. In addition, Se-amino acids are more easily subjected to oxidation than the corresponding thiols/thioethers and can bind redox-active metal ions. Adequate Se intake aids in preventing several metabolic disorders and affords protection against viral infections. At present, an epidemic caused by a novel coronavirus (SARS-CoV-2) threatens human health across several countries and impacts the global economy. Therefore, Se-supplementation could be a complementary treatment to vaccines and pharmacological drugs to reduce the viral load, mutation frequency, and enhance the immune system of populations with low Se intake in the diet.

Enhancement of the electrocatalytic abilities toward CO2 reduction by tethering redox-active metal complexes to the active site.

Tethering metal complexes, like[Ru(bpy)2Cl2] (bpy = 2,2`-bipyridine), which are redox-active at low reduction potentials and the ability to transfer electrons to another complex, to a [Ni(cyclen)]2+ electrocatalyst enhanced the reduction...