Academic literature on the topic 'Photovoltaic-electrochemical integrated system'

Self-powered systems for biosensing have attracted tremendous research interest in recent years, mainly due to the rapidly expanding market of wearable and portable devices for applications in clinical diagnosis and physiological monitoring. In our work, novel and unique hierarchical nanostructures were designed and synthesized to realize electrochemical devices with high performance, especially the sensor stability and energy storage capability. Meanwhile, scalable and printable approach was developed to integrate these electrochemical devices into monolithically integrated self-powered systems. The as-developed nanostructured electrochemical devices in conjunction with printable approach show great potency in fabrication of various wearable integrated self-powered devices for personalized healthcare monitoring applications. Our research highlights are as follow: Development of nanoporous membranes for electrochemical sensor applications. It eliminates enzymes escaping and provides sufficient surface area for molecular/ion diffusion and interactions, so as to ensure the sustainable catalytic activities of the sensors and generate reliable measurable signals during noninvasive monitoring. The highly improved stability of sensors is extremely desirable for investigation of metabolic activities in physiological systems. A fully integrated and self-powered system in a smartwatch fashion for continuous monitoring of sweat glucose levels during both equilibrium status and dynamic activities. The smartwatch can be self-powered by flexible photovoltaic cells, without external charging, the harvested energy can also be stored in the flexible Zn-MnO2 batteries as backup power source. It is also capable for real-time and in situ data analysis/display with integrated circuit board and E-ink screen. A monolithically integrated self-powered smart sensor system with energy supplied by fully printable planar supercapacitors and embedded solar cells, was fabricated on plastic substrate with inkjet printing technique as a proof-of-concept. The as-developed printable nanostructured electrochemical devices in conjunction with printable approach for system integration show great potency in fabrication of various wearable integrated self-powered devices for personalized healthcare monitoring applications.

The penetration of renewable power generation is increasing at an unprecedented pace. While the operating greenhouse gas (GHG) emissions of photovoltaic (PV) and wind power are negligible, their upstream emissions are not. The great challenge with the deployment of renewable power generators is their intermittent and variable nature. Current electric power systems balance these fluctuations primarily using natural gas fired power plants. Alternatively, these dynamics could be handled by the integration of energy storage technologies to store energy during renewable energy availability and discharge when needed. In this paper, we present a model for estimating emissions from integrated power generation and energy storage. The model applies to emissions of all pollutants, including greenhouse gases (GHGs), and to all storage technologies, including pumped hydroelectric and electrochemical storage. As a case study, the model is used to estimate the GHG emissions of electricity from systems that couple photovoltaic and wind generation with lithium-ion batteries (LBs) and vanadium redox flow batteries (VFBs). To facilitate the case study, we conducted a life cycle assessment (LCA) of photovoltaic (PV) power, as well as a synthesis of existing wind power LCAs. The PV LCA is also used to estimate the emissions impact of a common PV practice that has not been comprehensively analyzed by LCA—solar tracking. The case study of renewables and battery storage indicates that PV and wind power remain much less carbon intensive than fossil-based generation, even when coupled with large amounts of LBs or VFBs. Even the most carbon intensive renewable power analyzed still emits only ~25% of the GHGs of the least carbon intensive mainstream fossil power. Lastly, we find that the pathway to minimize the GHG emissions of power from a coupled system depends upon the generator. Given low-emission generation (<50 gCO2e/kWh), the minimizing pathway is the storage technology with lowest production emissions (VFBs over LBs for our case study). Given high-emission generation (>200 gCO2e/kWh), the minimizing pathway is the storage technology with highest round-trip efficiency (LBs over VFBs).

Photo-electrochemical (PEC) hydrogen generation is a promising technology and alternative to photovoltaic (PV)-electrolyser combined systems. Since there are no commercially available PEC cells and very limited field trials, a computer simulation was used to assess the efficacy of the approach for different domestic applications. Three mathematical models were used to obtain a view on how PEC generated hydrogen is able to cover demands for a representative dwelling. The analysed home was grid-connected and used a fuel cell based micro-CHP (micro-combined heat and power) system. Case studies were carried out that considered four different photo-electrode technologies to capture a range of current and possible future device efficiencies. The aim for this paper was to evaluate the system performance such as efficiency, fuel consumption and CO2 reduction capability. At the device unit level, the focus was on photo-electrode technological aspects, such as the effect of band-gap energy represented by different photo-materials on productivity of hydrogen and its uncertainty caused by the incident photon-to-current conversion efficiency (IPCE), which is highly electrode preparation specific. The presented dynamic model allows analysis of the performance of a renewable energy source integrated household with variable loads, which will aid system design and decision-making.

The development of a fully integrated photoelectrochemical cell capable of efficiently producing carbon-neutral fuels from sunlight, water, and atmospheric carbon dioxide is challenged by the electrochemical corrosion of photoelectrodes at the potentials required to drive the desired redox reactions. Recent progress in the development of protective coatings that integrate transparent conductive oxides with electrocatalysts has extended the operational lifetime of technologically important semiconductors such as Si, GaAs, and InP for use as photoanodes in aqueous alkaline electrolytes from seconds to hundreds or thousands of hours. Although an understanding of the failure modes for such devices has not yet been developed fully, systematic examinations of failure modes could lead to methods for improving the maximum attainable lifetimes, and would support the development of accelerated stability-testing protocols as well as modeling and simulation efforts to estimate device durability. This presentation will first provide a brief overview of recent progress in the development of protective coatings and catalyst-placement strategies for the stabilization of semiconductor electrodes for use in integrated solar fuels systems, and will then provide an in-depth examination of the failure mechanisms governing the performance and durability of a model system – Si anodes patterned with micrometer-scale Ni islands operating in contact with 1.0 M KOH (aq). In the patterned-catalyst approach, an insoluble protective oxide layer is grown over areas of the semiconductor not covered by the catalyst islands, and during operation the current is collected at and passed through the catalyst islands. For semiconductors such as Si that form insoluble oxides under water-oxidation conditions, the protective oxide layer can be grown in situ. The patterned-catalyst approach therefore can be considered a model system for protective coatings with pinhole or grain-boundary defects – where stability depends upon on passivation of the semiconductor beneath regions of the coating that allow direct contact with the electrolyte – allowing top-down definition and spatial control over regions analogous to through-film defects that are otherwise difficult to control and vary systematically. Ex situ and operando electrochemical, microscopic, and spectroscopic techniques were used to investigate the performance and stability of Si anodes patterned with a square array of micrometer-sized Ni islands and operated in contact with 1.0 M KOH (aq). Non-photoactive p+-Si(111) substrates were used to evaluate the stability of the catalyst as well as the formation of the passive SiOx layer. The impact of the diurnal cycle on the stability of the electrodes was evaluated by investigating the behavior of Si(100) substrates under open-circuit conditions. Buried-junction np+-Si(111) substrates were used to evaluate performance and stability under simulated solar illumination. The stability and efficiency of the patterned-catalyst Si electrodes were affected by the filling fraction of the Ni catalyst, the orientation and dopant type of the substrates, and the measurement conditions. The electrochemical behavior at different stages of operation, including Ni catalyst activation, Si passivation, steady-state operation, and device failure was affected by the dynamic processes of anodic formation and isotropic dissolution of SiOx on the exposed Si. Buried-junction np+-Si(111) photoanodes with an 18.0% filling fraction of a square array of Ni microelectrodes demonstrated performance equivalent to a Ni anode in series with a photovoltaic device having an open-circuit voltage of 538 ± 20 mV, a short-circuit current density of 20.4 ± 1.3 mA cm-2, and a photovoltaic efficiency of 6.7 ± 0.9%. For these samples the photocurrent density at the equilibrium potential for oxygen evolution was 12.7 ± 0.9 mA cm-2, yielding an ideal regenerative cell solar-to-oxygen conversion efficiency of 0.47 ± 0.07%. The photocurrent passed exclusively through the Ni catalyst islands to evolve O2 with nearly 100% faradaic efficiency. However, the passivating layer of SiOx dissolves in KOH, resulting in Si corrosion and SiOx dissolution especially in the dark. The dynamic processes of SiOx formation and etching affect both the electrical stability of the electrochemical and photovoltaic components, as well as the optoelectronic stability of the photovoltaic component. Localized undercutting of catalyst islands and damage to the emitter profile correlated with the current distribution on sample surfaces, suggesting substantial current branching at the location where the active catalysts and the corrosive solution are both present. This work provides evidence of one likely failure mechanism for Si photoanodes protected by transparent catalytic films, specifically, undercutting and removal of the catalysts at defects in protective coatings that can arise during fabrication, deployment and operation.

Abstract Thin film silicon based multi-junction solar cells were developed for application in combined photovoltaic electrochemical systems for hydrogen production from water splitting. Going from single, tandem, triple up to quadruple junctions, we cover a range of open circuit voltages from 0.5 V to 2.8 V at photovoltaic cell (PV) efficiencies above 13%. The solar cells were combined with electrochemical (EC) cells in integrated devices from 0.5 cm2 to 64 cm2. Various combinations of catalyst pairs for the oxygen and hydrogen evolution reaction side (OER and HER) were investigated with respect to electrochemical activity, stability, cost and – important for the integrated device – optical quality of the metal catalyst on the HER side as back reflector of the attached solar cell. The combined PV-EC systems were further investigated under varied operation temperatures and illumination conditions for estimation of outdoor performance and annual fuel production yield. For 0.5 cm2 size combined systems a maximum solar-to-hydrogen efficiency ηSTH = 9.5% was achieved under standard test conditions. For device upscaling to 64 cm2 various concepts of contact interconnects for reduced current and fill factor loss when using large size solar cells were investigated. To replace high performance noble metal based catalyst pairs (Pt/RuO2 or Pt/IrOx), more abundant and cheaper NiMo (HER) and NiFeOx (OER) compounds were prepared via electrodeposition. With the NiMo/NiFeOx catalyst pair we obtained ηSTH = 5.1% for a 64 cm2 size solar cell which was even better than the performance of the Pt/IrO2 system (ηSTH = 4.8%). In simulated day-night cycle operation the NiMo/NiFeOx catalyst pair showed excellent stability over several days. The experimental studies were successfully accompanied by simulation of the entire PV-EC device using a series connection model which allowed studies and pre-estimations of device performance by varying individual components such as catalysts, electrolytes, or solar cells. Based on these results we discuss the prospects and challenges of integrated PV-EC devices on large area for hydrogen and solar fuel production in general.

Photovoltaic (PV) electrolysis is an important and powerful technology for environmentally-friendly fuel production based on solar energy. By directly coupling solar cell materials to electrochemical systems to perform water electrolysis,...

The rise of Earth’s atmospheric CO2 levels, primarily due to combustion of fossil fuels, has affected its ecosystems. A way to combat this is by mimicking the plants photosynthesis by capturing CO2 from the atmosphere and convert it to usable hydrocarbon fuels, such as methane (CH4), because of the easy adaptability to the well-established infrastructure for natural gas (NG) storage, distribution and consumption. The denominated “solar methane”, very similar to NG, can be produced by converting solar energy from photovoltaic (PV) panels into electricity to power a 1-step reaction on electrochemical flow cell(s), using CO2 and water as the feedstock. Here, we simulate solar methane production and storage and apply it to address the energetic needs of concept buildings that have space and domestic hot water heating requirements. A combination of solar thermal collectors (STCs) and PV panels is optimized for buildings in different European locations, in which the heating needs that cannot be fulfilled by the STCs are satisfied by the combustion of methane synthesized by the PV-powered electrolyzers. Various combinations of situations for a whole year were studied and it was found that this auxiliary system can produce, per m2 of PV area, in the worst case scenario 23.6 g/day (0.328 kWh/day) of methane in Stockholm and in the best case scenario 47.4 g/day (0.658 kWh/day) in Lisbon.

Solar energy is a renewable and sustainable energy source that has a promising potential for the rapidly growing energy demands across the world. Large scale power generation from the energy of the sun is well established utilizing both direct thermal energy conversion and conversion to electricity via photovoltaic processes. Solar thermal systems have been limited to macro systems, even though they operate at higher efficiency compared to photovoltaic systems. Solar energy harvesting requires the use of collector plates to capture incident radiation. The surface area exposed to incident radiation is critical in solar thermal energy harvesting. In this work, we have integrated micro technology processes and solar thermal energy to design and fabricate a micro solar thermal system for power generation. This work specifically examined surface area enhancement using MEMS-based techniques to maximize solar thermal absorption. Selective absorber coating and enhanced surface areas due to the incorporation of micro structures on the collector substrates were utilized. In this manner, an important component to an autonomous micro power supply is investigated. Advanced microfabrication and electrochemical deposition techniques were employed to generate a selective absorber surface with enhanced surface area on a silicon substrate. Microchannels were used to enhance the surface area on the substrate. The selective absorber coating consists of a bimetallic structure consisting of tin and nickel.