Many non-traditional energy sources, such as solar panels, fuel cells, and batteries, supply direct-current (DC) power. This has led to development of DC power systems for a number of applications since conversion to alternating-current (AC) can be eliminated. For example, DC distribution is now used for computer data centers, office buildings, and ship power and propulsion. Though the source, loads, and other components in a DC power system are well understood, there may be interest in innovation with respect to protection schemes since DC systems do not have a zero crossing in its current, and circuit breakers are unable to open up a faulted component without sustaining an arc.

Researchers at the University of California, Davis, have developed an improved redox flow battery (RFB) for intermittent renewable energy applications such as wind, solar, and tidal. The device provides high-density energy storage and transfer without losing capacity over time and frequent replacement as with traditional lithium batteries.

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Photosynthetic organisms use “soft” macromolecular assemblies for light absorption and concentration of electronic excitation energy. These generally work via an optically inactive protein-based backbone that acts as a host matrix for an array of light-harvesting pigment molecules. The pigments are organized in space such that excited states can migrate between molecules, ultimately delivering the energy to the reaction center. 

Large format active or deformable mirrors can enable optical applications that are difficult to achieve with more conventional-sized deformable mirrors. In particular, adaptive secondary mirrors (ASMs) can be integrated into telescopes and provide adaptive optics corrections. However, making facesheets for ASMs is challenging. Current facesheet fabrication processes are costly and risky. Hot forming approaches for forming curved facesheets have been developed, but these methods typically require a mold for the facesheet to slump into.

Hydrogen from sustainable/renewable inputs shows promise as a decarbonized energy source. Hydrogen can be produced from a liquid electrolyte (e.g., water) through a variety of sunlight-based processes, including low/high-temperature electrolysis (e.g., steam electrolysis), photoelectrochemical (PEC), and solar thermochemical (STC). Temperature-based electrolysis systems using solar electricity are generally more complex and less solar-to-hydrogen efficient than PEC and STC. Water-splitting by PEC uses functional materials and leverages sunlight-driven electron-hole pairs to produce hydrogen and oxygen in two half reactions. STC water-splitting uses a series of consecutive chemical reactions and absorbed heat from sunlight to generate hydrogen and oxygen in two full reactions. Generation of hydrogen bubbles at the electrode-electrolyte interface obstruct the propagation of sunlight to functional or catalytic interfaces which limits the cell performance.

Renewable energy sources such as solar photovoltaics (PV) and wind turbines are used for clean power generation to address the ever-increasing energy consumption. With large-scale integration of renewables, battery storage becomes essential in the grid to meet supply-demand volatility. In these scenarios, direct current (DC) grids offer multiple benefits over alternating current (AC) grids such as, improved efficiency, controllability, reliability and reduced cost. Isolated voltage boost/step-up DC-DC converters are used for interfacing PV and wind energy sources with DC grids and DC-DC converters serve such applications and environments. Existing DC-DC converter designs have known weaknesses. For example, shunt-resonant converter capacitors require a dedicated charging interval in every switching half-cycle, which does not contribute towards energy transfer and results in duty-cycle loss. Since the shunt-resonant capacitor is designed to hold resonant energy sufficient for a rated current condition, resonant energy is fixed for all loading conditions. At reduced loading, reduced resonant energy is sufficient but shunt-configuration has no means to achieve this control. Although this may be mitigated by using two additional switches, this arrangement leads to increased losses and cost. At reduced loading, duty-cycle loss increases significantly because the reduced current results in longer capacitor charging time. This severely restricts the operation range of converter. Smooth current commutation and zero-current-switching (ZCS) are also lost at overload conditions since the capacitor is designed for rated-current condition. The shunt-resonant capacitor is expected to hold its voltage/energy during the operating mode when input inductor charges. However, a leakage path exists through the transformer winding parasitics, which results in capacitor discharge. As a result, the capacitor energy must be overrated to compensate for this loss, which further aggravates all of the aforementioned issues. In another example, series-resonant capacitors must also be charged to a voltage higher than the reflected voltage across the transformer-primary. Peak voltage-rating of primary-side components (e.g., switches and input inductor) is also increased. Series-resonant capacitor also transfers energy to the output during the time interval when resonant current commutation occurs, which requires using capacitors having a higher rating. At reduced loading, the series-resonant capacitor does not have enough voltage to satisfy the resonant condition. Switching frequency may be used as an additional control parameter without using extra switches. Reduction in switching frequency results in increased charging time and hence, higher voltage, while ripple content increases and requires larger filters due to varying switching frequency. Overall, while traditional DC-DC converters like the aforementioned meets some requirements, it may be desirable to have new DC-DC converter approaches to smoothly onboard and operate PV and wind energy production with DC grids.

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Prof. Ming Lee Tang and her colleagues from the University of California, Riverside have developed a promising new material for photonic devices utilizing hybrid materials composed of inorganic semiconductor nanocrystals and organic acene molecules. The material allows for photon upconversion, a promising wavelength shifting technology for photon management. This multi-photon process has potential applications in biological imaging, photocatalysis and photovoltaics. Regarding solar energy systems, the conversion of low energy near-infrared (NIR) photons to higher energy photons is particularly appealing, considering NIR radiation comprises 53% of the solar spectrum. Current solar panels are greatly limited in efficiency due to this. Reshaping the solar spectrum to match the optical properties of common semiconductors will allow the efficient use of all incident light. This holds the potential to solve the largest issue that current solar panel systems face.

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Many industries, such as solar cells and energy storage, will be greatly benefited by high-gain step-up/step-down converters.UCI researchers have developed a family of hybrid boosting converters (HBC) that combine a base bipolar voltage multiplier (BVM) and one of several possible inductive switching cores to address various converter functionalities.

Switched capacitor converters, which provide high-gain voltage conversion, have drawbacks that have limited their use to specific applications. UCI researchers have developed a family of two-switch boosting switched-capacitor converters (TBSC) that enables the use of switched-capacitor converters in low cost and small-size applications as well as on-chip integration.

UCLA researchers in the Department of Mechanical and Aerospace Engineering have developed a novel multi-point, multi-access thermal energy storage system.

   Researchers at UCI have, for the first time, developed a method for modeling the efficiencies of artificial photosynthetic devices containing multiple light absorbers. As these devices more closely parallel naturally occurring photosynthesis, they offer higher performance than standard single-absorber devices.

UCLA researchers in the Department of Chemistry & Biochemistry have developed an approach for synthesizing nitrogen-containing polycyclic aromatic hydrocarbons with high yield.

Researchers at UCLA have developed an underground drilled shaft concept for storage of hydrogen or other gases.

Researchers at UCI have developed a compact device for the rapid desalination of water which is driven entirely by renewable solar energy.