Innovative Nanomaterial Approaches For Solar Energy Applications

The fundamental limitation of the conversion efficiency achievable with solar energy solutions (which includes photovoltaic and photothermal technology), requires the adaptation and integration of a series of innovative material strategies to continue the process of sustainably decarbonizing the global economy. Through the passive integration of additional nanoscale features which exploit and modify the solar spectrum through its interactions with luminescent molecules, metal nanoparticles, and/or thin-film optical coatings – the solar spectrum can be modulated and accordingly the collection efficiency of each respective technology enhanced. However, irrespective of the type of spectral conversion integrated into the technology (luminescent down-shifting, nanofluids, plasmonic luminescent down-shifting, or spectral beam splitting), a series of additional loss mechanisms are introduced as a result of the architectural modifications. Through a proposed series of innovative & iterative advancements in each one of these material strategies, the objective of alleviating the additional loss mechanisms through a suitable combination of the individual approaches could potentially be realised

Evaluation of the Potential of Nanofluids Containing Different Ag Nanoparticle size Distributions for Enhanced Solar Energy Conversion in Hybrid Photovoltaic-Thermal (PVT) Applications

Hybridising photovoltaic and photothermal technologies into a single system that can simultaneously deliver heat and power represents one of the leading strategies for generating clean energy at more affordable prices. In a hybrid photovoltaic-thermal (PVT) system, the capability to modulate the thermal and electrical power output is significantly influenced by the spectral properties of the heat transfer fluid utilised. In this study, we report on one of the first experimental evaluations of the capability of a multimodal silver nanofluid containing various particle shapes and particle sizes to selectively modulate the solar energy for PVT applications. The diverse set of particle properties led up to a 50.4% enhancement in the solar energy absorbed by the nanofluid over the 300nm—550nm spectral region, where silicon is known to exhibit poor photovoltaic conversion performances. This improved substantially the absorption of solar energy, with an additional 18–129Wm−2 of thermal power being generated by the PVT system. Along with the advancements made in the thermal power output of the PVT system, a decrease of 4.7–36.6Wm−2 in the electrical power generated by the photovoltaic element was noted. Thus, for every∼11Wm−2 increase of thermal power achieved through the addition of the nanoparticles, a reduction of∼3Wm−2 in the ability to generate clean electricity was sustained by the PVT. Despite the energy trade-offs involved under the conditions of the nanofluid, the PVT system cumulatively harvested 405Wm−2 of solar energy, which amounts to a total conversion efficiency of 45%. Furthermore, the economics of the additional energy harvested through merging of the two systems was found to reach an enhancement of 77% under certain European conditions

A transfer matrix approach to aid in the design and optimization of hybrid advanced passive structures for enhancing photovoltaic efficiency

The addition of a luminescent down-shifting (LDS) layer directly onto a photovoltaic (PV) cell introduces additional loss mechanisms within the system. The combination of non-ideal photo-luminescent materials encapsulated within a limited range of viable host materials, with the increased reflection losses arising from the newly created interface represent losses which must be overcome for LDS to offer an enhancement to the underlying cells efficiency. Exploiting the interaction between the highly enhanced electric fields established close to a metal nanoparticles (MNP’s) surface is one route aimed at mitigating the poor optical properties of the luminophore-host combinations available. Alternative approaches, aimed at addressing the other loss mechanisms within such a system have gone relatively unexplored. Exploiting the non-ideal nature of the photo-luminescent materials available, offers a possibility of recycling the photons which previously did not undergo photoluminescence while also addressing the reflection losses through the inclusion of selectively reflecting optical structures. The hybrid device designs, incorporating single- and double layer- antireflection coatings composed of commonly available materials offer enhancements in the underlying PV cells performance of 8% - 30% depending upon the design criteria established. The transfer matrix approach adopted allowed the impact of individual design considerations on the reflection suppression capabilities of the structure, as well as their impact on the underlying cells efficiency to be readily determined

Humidity and Temperature Induced Changes in the Diffraction Efficiency and the Bragg Angle of Slanted Photopolymer-based Holographic Gratings

This work explores the humidity and temperature response of volume phase slanted gratings recorded in photopolymers with varied chemical composition. Acrylamide and diacetone acrylamide were used as monomers and triethanolamine and N-phenylglycine were used as photoinitiators. The study demonstrates that the response of photopolymer-based holographic gratings to relative humidity (RH) and temperature (T) can be tuned by alteration of the photopolymer composition.Humidity and temperature response of the holograms has been characterized by recording Bragg selectivity curves of transmission gratings and by monitoring the position of the maximum intensity in the spectral response of reflection gratings. Investigation of the humidity response in the range of 20–90% RH reveals that photopolymers containing triethanolamine are more responsive to moisture than photopolymers containing N-phenylglycine and display significant sensitivity to relative humidity above 40%. Full reversibility of humidity induced changes in gratings recorded in diacetone acrylamide-based photopolymer is confirmed at RH≤60%. Exposure to RH≥70% leads to irreversible changes in these gratings.The temperature response of slanted transmission gratings was investigated in the temperature range of 20–60°C. Exposure of the photopolymer layers containing triethanolamine to elevated temperature was found to cause layer shrinkage due to desorption of absorbed water. Sealed layers containing triethanolamine, however, demonstrated swelling due to the effect of thermal expansion. The photopolymer layers containing N-phenylglycine were found to be unresponsive to temperature changes below 30°C and have sensitivity to temperature above 30°C

Combined Experimental and Modeling Analysis for theDevelopment of Optical Materials Suitable to Enhance theImplementation of Plasmonic-Enhanced Luminescent Down-Shifting Solutions on Existing Silicon-Based Photovoltaic Devices

The development of highly efficient solar collectors requires modulating the light interactions with the semiconducting materials. Incorporating luminescent species and metal nanoparticles within a semitransparent polymeric material (e.g., polymethyl methacrylate (PMMA)) leads to the formation of a plasmon-enhanced luminescent down-shifting (PLDS) layer, which offers a retrofittable approach toward expanding the wavelength range over which the conversion process can effectively occur. Adding antireflection coatings (ARCs) further controls the spectral response. However, with each additional component comes additional loss pathways. In this study, the losses related to light interactions with the PMMA and the ARCs have been investigated theoretically using a transfer matrix method and experimentally validated. Two proposed architectures were considered, and the deviations between the optical response of each iteration helped to establish the design considerations. The proposed structure-enhanced (SE) designs generated a predicted enhancement of 37 to 62% for the collection performance of a pristine monocrystalline-silicon solar cell, as inferred through the short-circuit current density (Jsc). The results revealed the synergies among the SE-design components, demonstrating that the spectral response of the SEs, containing a thin polymer framework and an ARC, can be tuned to minimize the reflections, leading to the solar energy conversion enhancement

Development of poly-vinyl alcohol stabilized silver nanofluids for solar thermal applications

Nanofluids offer the potential to address the low thermal conductivities found in conventional heat transfer fluids, through their unique electrical, optical and thermal properties, but their implementation remains restricted due to absorption and stability limitations. Here, we characterize and exploit the distinctive plasmonic properties exhibited by polyvinyl-alcohol stabilized silver nanostructures by tuning their absorption and thermal properties through controlling the nanoparticle size, morphology and particle-size distribution configuration at the synthesis stage. The photo-thermal efficiency of different water-based silver nanofluids under a standard AM1.5G weighted solar spectrum were explored, the influence of each of these components on the resulting fluids performance within a direct absorption solar thermal collection system being considered. Nanofluids, containing an extensive ensemble of particle size-distributions (5 nm–110 nm in diameter) in addition to anisotropic particle morphologies (e.g. prisms, hexagons and other non-spherical geometries), exhibited a significant enhancement in the absorption and photo-thermal energy transfer. Enhancements of 5%–32% in the photo-thermal conversion efficiency were achieved, the enhancement being dependent upon the presence of multiple particle size-distributions and the particle concentration. The enhancement is influenced by the interactions occurring between the individual particle size-distributions but also by the collective behaviour of the particles ensemble. The critical particle diameter, above which the photo-thermal characteristics of the nanofluid become dominated by the larger sized particles present, was identified as 150 nm. The increased performance of these nanofluids, which adopt a more complex particle-size configuration, suggests that they can represent suitable candidates for solar-thermal applications

Nanofluid Development Using Silver Nanoparticles and Organic-Luminescent Molecules for Solar-Thermal and Hybrid Photovoltaic-Thermal Applications

Exploiting solar energy using photo-thermal (PT) and/or hybridised photovoltaic/thermal (PVT) systems can represent a viable alternative to the growing demand for renewable energy. For large-scale implementation, such systems require thermal fluids able to enhance the combined conversion efficiency achievable by controlling the ‘thermal’ and ‘electrical’ components of the solar spectrum. Nanofluids are typically employed for these purposes and they should exhibit high heat-transfer capabilities and optical properties tuned towards the peak performance spectral window of the photovoltaic (PV) component. In this work, novel nanofluids, composed of highly luminescent organic molecules and Ag nanoparticles dispersed within a base fluid, were tested for PT and PVT applications. These nanofluids were designed to mimic the behaviour of luminescent down-shifting molecules while offering enhanced thermo-physical characteristics over the host base fluid. The nanofluids’ conversion efficiency was evaluated under a standard AM1.5G weighted solar spectrum. The results revealed that the Ag nanoparticles’ inclusion in the composite fluid has the potential to improve the total solar energy conversion. The nanoparticles’ presence minimizes the losses in the electrical power component of the PVT systems as the thermal conversion increases. The enhanced performances recorded suggest that these nanofluids could represent suitable candidates for solar energy conversion application

MPSoCs for Reconfigurable Modular Spacecraft

Modular, reconfigurable spacecraft offer a new approach to extending mission capability and maximising the lifetime of a spacecraft. Future uses of space robotics such as in-orbit construction and servicing allow faulty or obsolete parts of a modular spacecraft to be replaced by servicer spacecraft that dock with their targets and perform upgrades and maintenance. Such manoeuvres will require a high degree of autonomy from both platforms and thus will need to leverage high-performance onboard computing for both the robotic control and manipulation of service spacecraft but also for managing Thales Alenia Space in the UK (TAS UK) and The University of York (UoY) are involved in projects towards this goal and are collaborating to research autonomous network reconfiguration and fault tolerance of the onboard network based on existing space technology (SpaceWire, SpaceFibre). Both organisations have identified FPGA based MPSoCs as a solution for providing the high-performance computing that autonomous robotic systems require, using the FPGA fabric for mission-phase related hardware accelerators (e.g. vision soft co- processors) that can be swapped as the construction or maintenance task demands. In this presentation we will describe the modular spacecraft avionics unit that TAS UK is developing for the H2020 MOSAR project. This is based on the Xilinx Ultrascale+ MPSoC and uses the “big-little” architecture to provide a split between the spacecraft module’s mission functionality (executing on the “big” quad-core A53) and the support functions to provide: the communication network, module-to-module docking management and the module power management functions of the spacecraft (implemented on the “little” dual-core R5 cores). Details on our development of an AXI4 compatible SpaceWire and RMAP IP core will also be included. RMAP forms an important part of the MOSAR fault management strategy and this core allows processor-transparent RMAP access to the full MPSoC address range, with automatic DMA descriptors for all other SpaceWire traffic. The AXI4 interface simply allows it to be dropped into any Ultrascale+, Zynq 7000 and NG-ultra based design and several configuration options allow options such as SpW front end type (oversampling /clock recovery) and output data path width (32-bit/16bit) to be selected. We will also present details of research by the University of York on using RMAP in a MPSoC environment. Access to the full address space of a MPSoC via RMAP brings security and fault management concerns to complex SoCs and hardware security based approaches (e.g. ARM’s TrustZone) could be used in future MP- SoC architectures to protect against damage by either corrupt RMAP packets, damage from failure modes of RMAP initiators or malicious/compromised spacecraft modules. To tackle autonomy challenges UoY is cur- rently developing a reasoner based, reconfigurable modular robotic platform that can cope with uncertain environments that arise in space applications using FPGA based MPSoC and soft-processor technologies. MOSAR has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant agreement No. 821996. Part of this work is funded by EPSRC and Innovate UK under grant KTP12066

Adding Fish Oil to Whey Protein, Leucine and Carbohydrate Over a 6 Week Supplementation Period Attenuates Muscle Soreness Following Eccentric Exercise in Competitive Soccer Players

Soccer players often experience eccentric exercise-induced muscle damage given the physical demands of soccer match-play. Since long chain n-3 polyunsaturated fatty acids (n-3PUFA) enhance muscle sensitivity to protein supplementation, dietary supplementation with a combination of fish oil-derived n-3PUFA, protein, and carbohydrate may promote exercise recovery. This study examined the influence of adding n-3PUFA to a whey protein, leucine, and carbohydrate containing beverage over a six-week supplementation period on physiological markers of recovery measured over three days following eccentric exercise. Competitive soccer players were assigned to one of three conditions (2 × 200 mL): a fish oil supplement beverage (FO; n = 10) that contained n-3PUFA (1100 mg DHA/EPA - approximately 550 mg DHA, 550 mg EPA), whey protein (15 g), leucine (1.8 g), and carbohydrate (20 g); a protein supplement beverage (PRO; n = 10) that contained whey protein (15 g), leucine (1.8 g), and carbohydrate (20 g); and a carbohydrate supplement beverage (CHO; n = 10) that contained carbohydrate (24 g). Eccentric exercise consisted of unilateral knee extension/flexion contractions on both legs separately. Maximal force production was impaired by 22% during the 72-hour recovery period following eccentric exercise (p < 0.05). Muscle soreness, expressed as area under the curve (AUC) during 72-hour recovery, was less in FO (1948 ± 1091 mm × 72 h) than PRO (4640 ± 2654 mm × 72 h, p < 4 0.05) and CHO (4495 ± 1853 mm × 72 h, p = 0.10). Blood concentrations of creatine kinase, expressed as AUC, were ~60% lower in FO compared to CHO (p < 0.05) and tended to be lower (~39%, p = 0.07) than PRO. No differences in muscle function, soccer performance, or blood c-reactive protein concentrations were observed between groups. In conclusion, the addition of n-3PUFA to a beverage containing whey protein, leucine, and carbohydrate ameliorates the increase in muscle soreness and blood concentrations of creatine kinase following eccentric exercise in competitive soccer players

Expanding health technology assessment towards broader value: Ireland as a case study

Healthcare innovations often represent important improvements in population welfare, but at what cost, and to whom? Health technology assessment (HTA) is a multidisciplinary process to inform resource allocation. HTA is conventionally anchored on health maximization as the only relevant output of health services. If we accept the proposition that health technologies can generate value outside the healthcare system, resource allocation decisions could be suboptimal from a societal perspective. Incorporating broader value in HTA as derived from social values and patient experience could provide a richer evaluative space for informing resource allocation decisions. This article considers how HTA is practiced and what its current context implies for adopting broader value to evaluating health technologies. Methodological challenges are highlighted, as is a future research agenda. Ireland serves as an example of a healthcare system that both has an explicit role for HTA and is evolving under a current program of reform to offer universal, single-tier access to public services. There are various ways in which HTA processes could move beyond health, including considering the processes of care delivery and/or expanding the evaluative space to some broader concept of well-being. Methods to facilitate the latter exist, but their adaptation to HTA is still emerging. We recommend a multi-stakeholder working group to develop and advance an international agenda for HTA that captures welfare/benefit beyond health.Health Research Board