Enhancing photovoltaic efficiency through evaporative cooling and a solar still

The efficiency of photovoltaic panels decreases with the increase in panel temperature while converting light into electricity. The issue of temperature rise and the associated decrease in efficiency has been widely analysed by active and passive cooling methods. In those processes, normally water is used as a cooling medium, and it results in water loss along with power loss due to circulating or compensating for the lost water. The current study aims to address both efficiency as well as water loss by combining an evaporative cooling technique with a solar still. A Photovoltaic panel with rear-side evaporative cooling is attempted by using a jute sack dipped in water at both ends. As a result of capillary action, the water from a solar still rises through the sack and cools the panel’s rear side. Solar still operation is ensured by an extended portion of glass. During desalination, the evaporated vapour from the solar still condenses on the back cover of the glass surface and is collected in a collection trough. As a result, the output power increased by 5.6 % and the electrical efficiency increased by 14.51 % and the surface temperature are reduced by 8°C. After seven hours of sunshine, the proposed PV panels and solar still system produced approximately 550 ml of water

Experimental and numerical investigation on flow angle characteristics of an automotive mixed flow turbocharger turbine

To date, turbocharger remains as a key enabler towards highly efficient Internal Combustion Engine. Although the first turbocharger was patented more than 30 years ago, the design is still being improved, thus signifying its importance in modern vehicles. One of the key features that contribute to the challenges in designing highly efficient turbine is the complex nature of the flow field within the turbine stage itself. Experimental method could be used to extract parameters such as pressure and temperature traces but still unable to provide a full description of the flow field. Therefore, the use of Computational Fluid Dynamics (CFD) in resolving this issue is necessary. Out of many feature of fluid flow in turbomachinery, the flow angle at rotor inlet plays significant role in determining turbine efficiency. However, due to geometrical complexity, even at optimum averaged incidence flow angle, there still exist variations that could impair the turbine ability to produce work. This research attempts to provide insight on the complexity of flow angle distribution within the turbocharger turbine stage. To achieve this aim, a numerical model of a full stage turbocharger turbine operating at 30000rpm under its optimum condition was developed. Results indicated that even though use of guide vanes has reduced flow angle fluctuations at mid-span of the rotor inlet from ±10° to only ±1°, significant variations still exist for velocity components in spanwise direction. This in turns effected the distribution of incidence flow angle at the rotor leading edge. In the current research, variation of incidence flow angle in spanwise direction is recorded to be as high as 60

Steady state performance evaluation of variable geometry twin-entry turbine

This paper presents the results from an experimental investigation conducted on different turbine designs for an automotive turbocharger. The design progression was based on a commercial nozzleless unit that was modified into a variable geometry single and twin-entry turbine. The main geometrical parameters were kept constant for all the configurations and the turbine was tested under steady flow conditions. A significant depreciation in efficiency was measured between the single and twin-entry configuration due to the mixing effects. The nozzleless unit provides the best compromise in terms of performance at different speeds. The twin-entry turbine was also tested under partial and unequal admissions. Based on the test results a method to determine the swallowing capacity under partial admission given the full admission map is presented. The test results also showed that the turbine swallowing capacity under unequal admission is linked to the full admission case

Improving energy extraction from pulsating exhaust flow by active operation of a turbocharger turbine

A mixed flow turbine with pivoting nozzle vanes was designed and tested to actively adapt to the pulsating exhaust flow. The turbine was tested at equivalent speed of 48000 rpm with inlet flow pulsation of 40Hz and 60Hz, which corresponds to a 4-stroke diesel engine speed of 1600 rpm and 2400 rpm respectively. The nozzle vane operating schedules for each pulse period are evaluated experimentally in two general modes; natural opening and closing of the vanes due to the pulsating flow and the forced sinusoidal oscillation of the vanes to match the incoming pulsating flow. The turbine energy extraction as well as efficiency is compared for the two modes to formulate its effectiveness

Unsteady effect in a nozzled turbocharger turbine

The unsteady behavior of a nozzled turbocharger turbine under pulsating flow conditions has been studied experimentally in a cold flow test facility that replicates engine pulses. The results presented are obtained at a turbine speed of 48,000 rpm for pulsating frequencies of 40 Hz and 60 Hz (which correspond to 1600 rpm and 2400 rpm in a twin turbocharger six cylinder internal combustion engine). The turbine unsteady behavior is compared for nozzle vane angles ranging between 40 deg and 70 deg. A nozzled turbocharger turbine is found to behave differently from a nozzleless turbine under pulsating flow. The existence of a nozzle ring “damps” the unsteady flow leading to a reduced level of flow dynamics affecting the turbine wheel for all vane angles. The bigger volume in the nozzled turbine is also another contributing factor to the observed characteristics. The results are more pronounced in the higher frequency and maximum vane opening condition. Given this “damping” behavior, the concept of unsteady efficiency is questioned. The level of unsteadiness in the flow is characterized by the relevant nondimensional parameters, and the onset of the unsteadiness in the flow and its effect on a nozzled turbocharger turbine is discussed. The onset of the unsteady effect is suggested to be at 40 Hz flow condition. However, the nozzled turbine exhibits more of filling and emptying characteristics for both the frequency conditions, especially at close nozzle position cases. The effect of unsteadiness on the instantaneous efficiency calculation is more pronounced in the nozzled turbine compared with a nozzleless turbine

Photovoltaic Module with Uniform Water Flow on Top Surface

Though the solar photovoltaic (PV) module is used for power production, it usually works at high temperatures, decreasing its efficiency and therefore its output. So if an effective cooling method is to be implemented, it would reduce the heat from the solar PV module and increase its power production. Significant research in water cooling on both top and bottom surfaces of the PV module widen the scope for uniform cooling with constant module temperature throughout at any instant. In this work, uniform flow is maintained by means of overflow water from a tank fitted on the top of the PV module. Experiments were carried out with and without cooling. Performance parameters in terms of power output and efficiency have been presented for the PV module without cooling and cooling with three different mass flow rates. The results show that there is a significant rise in efficiency of the PV module by reducing its temperature. An accelerated output power of 23 W has been observed for a higher mass flow rate of 5.3 kg/min which is 15% higher than the photovoltaic module operating without cooling. Results were compared with previous researchers’ work and found to be a good enhancement. Theoretical results agree well with experiments

Solar still with vapor adsorption basin: Performance analysis

In this work, a vapor adsorption type solar still was designed, fabricated and tested at Thiagarajar College of Engineering, Madurai, India. A vapor adsorbent pipe network comprising activated carbon-methanol pair was integrated with the basin. Losses from the bottom of the still are considerably reduced due to sensible heat absorption by the activated carbon and latent heat of vaporization by methanol. Also water circulated through the inner tube of the adsorbent bed is used as a feed to basin, thus enhancing the evaporation rate during day time. The increase in temperature of the basin due to adsorbent bed and condensation of methanol vapor, augments the evaporation rate during the night time also. Sponges, gravels, sand and black rubbers were used in the vapor adsorption type solar still for improving the yield. Experimental results were compared with ordinary conventional basin type still. The governing energy balance equations for both conventional and vapor adsorption type solar still were solved analytically and compared with experimental results. Theoretical analysis gave very good agreement with experimental results