Performance analysis of a novel integrated photovoltaic-thermal system by top-surface forced circulation of water

Almost 80-90%of energy is wasted as heat(provides no value)in a photovoltaic(PV)panel.An integrated photovoltaic-thermal(PVT)system can utilize this energy and produce electricity simultaneously.In this research,through energy and exergy analysis,a novel design and methodology of a PVT system are studied and validated.Unlike the common methods,here the collector is located outside the PV panel and connected with pipes.Water passes over the top of the panel and then is forced to the collector by a pump.The effects of different water-mass flow rates on the PV panel and collector,individual and overall efficiency,mass loss,exergetic efficiency are examined experimentally.Results show that the overall efficiency of the system is around five times higher than the individual PV-panel efficiency.The forced circulation of water dropped the panel temperature and increased the panel efficiency by 0.8-1%and exergy by 0.6-1%,where the overall energy efficiency was~81%.

Photovoltaic-thermal solar-assisted heat pump systems for building applications:Integration and design methods

The photovoltaic-thermal collector is one of the most interesting technology for solar energy conversion,com-bining electric and thermal energy production in a single device.Vapour-compression heat pump is already considered the most suitable clean technology for buildings thermal energy needs.The combination of these two technologies in an integrated“photovoltaic-thermal solar-assisted heat pump”(PVT-SAHP)system allows reaching a high fraction of the building thermal needs covered by renewable energy sources and to improve the performances of both the photovoltaic-thermal collector and the heat pump.The first is cooled down increasing its energy conversion efficiency,while providing low-temperature thermal energy to the second,which benefits from a higher evaporation temperature.The review study presents the state-of-art of photovoltaic-thermal solar-assisted heat pump systems intended to cover thermal energy needs in buildings,with a particular focus on the integration methodologies,the possible configurations,the use of different sources and the design of sub-system components.These issues are addressed by much scientific research,to improve the reliability and applicability of this technology,as an option for the building decarbonization.This study aims to present PVT-SAHP systems in an organic and critical way to propose a useful tool for future research developments.More in detail,the work highlights the fact that the integration of photovoltaic-thermal collectors as evaporator of the heat pump in direct-expansion systems allows the highest heat recovery and performances.However,the distinction of the two circuits lead to more reliable,flexible and robust systems,especially when combined with a second heat source,being able to cover both heating and cooling needs.The implementation of real-time control strategy,as well as the continuous development of the compressor and refrigerant industries is positively influencing this technology,which is receiving more and more attention from scientific research as a suitable solution for nearly zero energy buildings.

Benchmark assessment of performance indices of a selection of hybrid nanofluids in a hybrid photovoltaic/thermal system

This research is a study assessing the performance of hybrid nanofluids in hybrid photovoltaic(PV)-thermal systems.This study addresses 10 hybrid nanofluids applied to hybrid PV-thermal systems.The transition to carbon-free energy can mitigate the worst effects of climate change,ensuring that global sustainability is addressed.Clean energy is now responsible for one-third of the global capacity,of which 20%is attributed to solar energy.Renewables continue to be economically viable,with declining costs driving growth.This study aims to compare the yearly performances of a model hybrid PV-thermal system using 10 different hybrid nanofluids.Hybrid nanofluids constitute two or more dissimilar materials stably suspended in a base fluid(e.g.water).MATLAB and COMSOL Multiphysics®computational fluid dynamics software are employed together for the benchmarking assessment with good agreement observed.Various fluid inlet temperatures(Tin∈[300,360]K),nanofluid volume concentrations(φ∈[0,4]%)and storage-tank volumes(V∈[50,300]L)were simulated.The meteorological data applied were those for Lagos,Nigeria(6°27’55.5192”N,3°24’23.2128”E).The assessment based on analytical-numerical solutions reveals that the thermal enhancement by hybrid nanofluids ranges from 6.7%(graphene oxide[GO]-multiwalled carbon nanotube[MWCNT]/water)to 7%(ZnO-Mn-ZnFe2O4/water)forφ=2%and V=300 L.The yearly exergy efficiency ranges from 2.8%(ZnO-Mn-ZnFe2O4/water)to 2.9%(GO-MWCNT/water),also forφ=2%and V=300 L.These findings have implications for a vast range of industrial processes,expanding the knowledge that is critical to a sustainable future.