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

Abstract

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 applications.

Evaluation of the potential of nanofluids containing different Ag nanoparticle size distributions for enhanced solar energy conversion in hybrid photovoltaic-thermal (PVT) applications

“…Typically, to determine with a high degree of sensitivity the optical transmittance of a two-component fluid (such as the nanofluid investigated here) the transmittance measurement needs to be performed at two different path lengths [39]. However, the average deviation between the transmittance recorded at a single path length and the value registered using the standardised two path-length protocol outlined in [39] was found to be±6.4% for the analogous Ag nanofluid's described in [22]. Thus, the transmittance data presented herein correspond to spectra recorded using a single path-length, where the associated error on the measurement has been included in all subsequent calculations used in modelling that involve this spectral information.…”

“…An alternative solution is to place the HTF in front of the PVT [19], however, for this configuration to yield a positive exergetic merit for the system the spectral properties of these HTF needs to be carefully assessed before their integration in PVT applications [20]. This stems from the fact that in order to efficiently partition the solar spectrum into its respective thermal and electrical components, the optical properties of the HTF must also be spectrally matched to the responsivity of the PV element [21,22]. Additionally, the ability of the classic HTFs to transport thermal energy efficiently can be restricted by their relatively low thermal conductivities [23].…”

“…This allowed the spectral changes induced in the optical properties of the nanofluids to be ascertained. The impact of partitioning the solar spectrum into its thermal and electrical components for the PVT system, due to the presence of the nanofluids, was evaluated using modelling [21,22]. Finally, the modified thermal and electrical power output of the PVT system under the partitioned solar irradiance of the nanofluids was analysed from an economic perspective through the implementation of a merit function [22].…”

“…The impact of partitioning the solar spectrum into its thermal and electrical components for the PVT system, due to the presence of the nanofluids, was evaluated using modelling [21,22]. Finally, the modified thermal and electrical power output of the PVT system under the partitioned solar irradiance of the nanofluids was analysed from an economic perspective through the implementation of a merit function [22]. In this regard, the economic merit of the additional energy captured as a result of modifying the spectral properties of the base fluid were analyzed under real-world European economic conditions.…”

Flexible Transparent Heat Mirror for Thermal Applications

“…This unique optical property of THM shows great potential in thermal management of places that require light transmission [ 27 , 28 ]. Dopants such as Ti, Ge, and Ag to the ITO matrix were found to be helpful for enhancing both the electrical conductivity and optical transparency [ 29 , 30 , 31 ]. However, there have been only limited efforts and attempts to introduce them into applications of thermal management.…”