Application of nanofluids in solar energy system's performance enhancement

Energy systems are meaningful devices which are based on basic laws of physics to take energy at one end and transform it into another form with optimum efficiency. Scientists, engineers always strive to make systems more efficient and lighter. This motive acts as driving force to bring about new technologies, materials and alternative approaches. Nanofluids are that kind of materials which have revolutionized energy absorbing, transporting and storage systems. Various parameters which are cardinal in thermal performance enhancement are drastically modified when material changes into nanoform. These parameters are thermal conductivity, heat transfer coefficient, optical extinction coefficient, electrical conductivity, viscosity, density, metallic property. When materials changes its phase from bulk to nano, surface to volume ratio changes tremendously. In our experimental analysis we have chosen nanofluids (MgO+CNTs)/H₂O Hybrid for evaluating performance of and flat plate solar collector for exergy efficiency, entropy generation and thermal efficiency. Exergy efficiency indicates how system is efficient to convert available energy into useful work. We have gone through preparation of nanofluid along with characterization. Experimental analysis established that at 1% volume concentration and the flow rate 21/min exergetic efficiency (second law efficiency) for (MgO+CNTs)/H₂O nanofluid is enhanced by ∼28 % compare to water, ∼13% compare to MgO. Entropy generation rate, which is penalty increases insignificantly at lower concentration for MgO hybrid compare to MgO. But enhancement in exergy efficiency dominates over increment in entropy generation rate. We can conclude that nanofluid based energy transporting systems are more efficient in terms of performance and energy saving. (author)