Srinivasa K Reddy

In photovoltaic (PV) cells, a large fraction of solar radiation gets converted into heat which raises its temperature and decreases its efficiency. The heat can be extracted by attaching a box containing phase change material (PCM) behind the PV panel. Due to large latent heat of PCM, it can absorb heat without rise in temperature. It will lower down the PV temperature and will increase its efficiency. The available numerical studies analysed the vertical PV-PCM systems. However, PV panels are generally tilted according to latitude of the place. Thus, in the current work, performance analysis of the tilted PV-PCM is carried out. The effects of tilt-angle, wind-direction, wind-velocity, ambient-temperature and melting-temperature of PCM on the rate of heat extraction by PCM, melting process of PCM and temperature of PV-PCM system are also studied. The results show that as tilt-angle increases from 0° to 90°, the PV temperature (in PV-PCM system) decreases from 43.4 °C to 34.5 °C which leads to increase in PV efficiency from 18.1% to 19%. The comparison of PV-PCM with only-PV is also carried out and it is found that PV temperature can be reduced by 19 °C by using PCM and efficiency can be improved from 17.1% to 19%.

In photovoltaic (PV) cells, a large portion of the solar-irradiance becomes heat which shoots the cell temperature up and decreases its electrical efficiency. The heat can be removed using phase-change-material (PCM) at the rear of the PV. In literature, the researchers have reported the performance of PV-PCM for their respective locations. However, selection criteria for climates suitable for PCM integration are not reported yet. Thus, it has been carried out in the current work. The model has been validated against the experimental measurements. It has been concluded that (i) the climates having less variations in the ambient temperature are more suitable for PCM integration. The electricity enhancement achieved by PV cooling is 9.7%. It reduces to 6.6% for the climate having large variations, (ii) Heat extraction by PCM-systems is more effective in warm climates in comparison to cold climates, (iii) PCM integration performs better in climates with low wind-speed, (iv) PCM is more effective for the climates where wind-flow is across the PV and (v) Climates having high solar-radiation is better for heat removal by PCM.

Heat generation during the operation of the photovoltaic (PV) cell raises its temperature and results in reduced electrical output. The heat produced in the process can be removed by attaching phase change material (PCM) at the back of the PV panel which can contain the PV temperature substantially and increase its efficiency. Fins can be used inside the PCM container to enhance the heat transfer. In literature, it is observed that as soon as PCM is melted completely, the heat extraction rate of PCM reduces which again leads to increase in PV temperature. However, the study carrying out the optimization of Finned-PV-PCM system to keep PV temperature low during operation for different solar irradiance levels is not available in literature. Thus, in the current study, the most suitable depth of PCM container is calculated for different solar irradiance levels. In addition, how it is affected with spacing between successive fins, fin length and fin thickness has been studied. The best fin dimensions are also calculated. The results show that the most suitable depth of PCM container is 2.8 cm for ∑IT = 3 kWh/m2/day and 4.6 cm for ∑IT = 5 kWh/m2/day for the chosen parameters. The best spacing between successive fins (to keep PV temperature low) is 25 cm, best fin thickness is 2 mm and best fin length is the one when it touches the bottom of the container. PV, PV-PCM and Finned-PV-PCM systems are also compared. For PV-PCM system (without fins), the most suitable depth of PCM container is 2.3 cm for ∑IT = 3 kWh/m2/day and 3.9 cm for ∑IT = 5 kWh/m2/day.

The rise in the temperature of photovoltaic (PV) leads to decrease in the solar to electricity conversion efficiency. This paper presents a simulated study to investigate the thermal management of the PV panel using phase change material (PCM). It is found that once the PCM is fully melted, the rate of heat extraction by PCM decreases and, thus, the PV temperature starts increasing rapidly. In literature, the studies related to the performance analysis of the PV-PCM system are available. However, the optimization of the PCM quantity to cool the PV in various operating conditions and solar radiation levels is not available. Thus, it has been carried out in the presented work. The effects of the operating conditions (wind azimuth angle i.e. wind direction, wind velocity, melting temperature of PCM and ambient temperature) on the optimum depth of the PCM container have been analysed. The results show that as wind azimuth angle increases from 0° to 90°, the optimum depth of the PCM container (to maintain the PV at lower temperature) increases from 3.9 cm to 5.3 cm for ∑IT = 5 kWh/m2/day and from 2.4 cm to 3.2 cm for ∑IT = 3 kWh/m2/day for the chosen parameters.

Among all passive methods for photovoltaics (PV) cooling, phase change material (PCM) can be highly effective due to high latent heat capacity. However, very low thermal-conductivity of PCM restricts its potential. The proposed work focuses on the enhancement of rate of heat transfer from PV to PCM by using conductivity-enhancing-containers. The proposed approach was experimented outdoor and compared with the reference panel for different seasons at Chennai, India. PV temperature, open circuit voltage, short circuit current, Current-Voltage (I–V) and Power-Voltage (P–V) curves, fill-factors, power outputs, efficiency and daily electricity generation are reported. The results show that the proposed heat sink was able to decrease the maximum PV temperature from 64.4 °C to 46.4 °C for January and 77.1 °C to 53.8 °C for June. It increased the open circuit voltage of PV from 24.3 V to 26.4 V for January and 23.6 V to 26.0 V for June. The fill-factor increased from 0.678 to 0.705 for January. Consequently, the electrical efficiency increased from 9.5% to 10.5% during noon. Daily electricity generation increased from 769 Wh/day to 817 Wh/day during January and 948 Wh/day to 1026 Wh/day during June. Thus, daily electricity generation increased by 6.2% for January and 8.3% for June using proposed approach.

The intermittent nature of renewable sources, such as solar and wind, leads to the need for a hybrid renewable energy system (HRES) that can provide uninterrupted and reliable energy to a remote and off-grid location with the use of a biogas generator and battery. In the present study, conventional PV panels have been integrated with phase change material (PCM) for power enhancement. In addition, various configurations (i. PV-Wind-Battery system, ii. PV-PCM-WindBattery, iii. PV-Wind-Biogas-Battery and iv. PV-PCM-Wind-Biogas-Battery) have been compared for the hot and humid climatic location of Chennai, India. Optimization has been carried out to minimize the cost of energy and the net present cost has also been computed. It has been found that the integration of PCM with the PV-Wind-Biogas-Battery-based off-grid system results in savings of USD 0.22 million in terms of net present cost and reduces the cost of energy from USD 0.099/kWh to USD 0.094/kWh. Similarly, for another off-grid HRES configuration of PV-Wind-Battery, the integration of PCM results in savings of USD 0.17 million, and reduces the cost of energy from USD 0.12/kWh to USD 0.105/kWh.

The present work aims at the optimization of fins fitted phase change material equipped photovoltaic system under different working circumstances for proper power enhancement. Setup has been modelled and the best deepness of fins fitted phase change material enclosure has been computed for a range of daily collective solar flux at photovoltaic panel surface, wind pace, wind azimuth, surroundings temperature, melting point, successive fins distance, fins deepness and fins width in order to analyse the influence of working circumstances. It is shown that the change in wind pace from 0.2 m/s to 6 m/s results in reduction of best deepness of phase change material enclosure from 5.2 cm to 3.7 cm, 5.6 cm to 4.0 cm, 5.8 cm to 4.2 cm, 5.9 cm to 4.3 cm and 5.9 cm to 4.3 cm for successive fins distance of 1 m, 1/2 m, 1/3 m, 1/4 m and 1/5 m respectively for daily collective solar flux at photovoltaic panel as 5000Wh/m2. The change in wind azimuth from 0° to 75° results in increment in the best deepness of enclosure from 3.9 cm to 4.8 cm, 4.3 cm to 5.2 cm, 4.5 cm to 5.4 cm, 4.6 cm to 5.5 cm and 4.6 cm to 5.5 cm for respective fins distances. The power production is increased from 125 W/m2 to 137 W/m2, 140 W/m2, 142 W/m2, 143 W/m2 and 143 W/m2 with fins width of 0 mm, 0.5 mm, 1 mm, 2 mm and 4 mm respectively.

Phase change material (PCM) has capability to increase the power production of solar photovoltaics (PV) by effective temperature regulation. In this work, Thermal Conductivity Enhancing Containers (TCEC) are proposed. They allow the PCM to extract the heat from all sides of the containers instead of only front which improves the thermal conductivity of the PCM containers and increases the PV electrical efficiency. PCM was filled inside the TCECs and pasted at the back of the PV. Systems with and without PCM, with and without TCEC and systems with different tilt angles have been investigated. The melting of PCM, rate of thermal energy storage, charging efficiency and enhancement in PV performance are analyzed. The behavior of the systems is analyzed for the climates of Portsmouth, UK and Chennai, India. It is seen that the average charging efficiency of PCM can be increased from 49% to 62% using proposed TCEC. Moreover, the average rate of thermal energy storage can be increased from 249 W/m2 of aperture to 302 W/m2 and the PV electrical efficiency can be increased from 17.6% to 19.2% using TCEC-PCM. It is also seen that as the inclination of PCM container decreases from 45° to 0°, the charging efficiency decreases by 32%.

Heat transfer enhancement and optimization are found to be essential for the PCM (phase change material) thermal energy storage design. In this work, the performance advantage of the packed bed PCM storage unit design is analyzed in comparison, and the impacts of key geometric parameters of a packed bed unit were numerically investigated. The optimized shell-and-tube design, based on the hexagonal circle configuration, serves as the benchmark for the comparison. The thresholds of the bed and PCM-capsule diameter ratio,D/d, is found, above which the effective energy storage capacity of the packed bed would be higher than that of an optimal shell-and-tube unit. The threshold of D/d can be quantitatively correlated to the superficial velocity of the heat transfer fluid, providing a pathway for the tailored design of a packed bed PCM thermal storage system. In conclusion, it was found that packed bed units are advantageous due to their larger surface-to-volume ratio, in particular in large-scale applications. This work proposes a numerical analysis based framework to design packed bed PCM storage units in comparison with shell-and-tube units so that a proper type of PCM thermal storage design can be selected under a specific geometric and operational condition.

Phase change material (PCM) based passive cooling of photovoltaics (PV) can be highly productive due to high latent heat capacity. However, the low rate of heat transfer limits its usefulness. Thus, the presented work aims at the improvement in PV cooling by using finned PCM (FPCM) heat sinks. In the present study, PCM heat sink and FPCM heat sinks were investigated numerically for PV cooling and the extracted heat is used for space heating. 4 kWp PV, PV-PCM and PV-FPCM systems were studied under the weather conditions of Southeast of England. It was observed that the PCM heat sinks can drop the peak PV temperature by 13 K, whereas FPCM heat sinks can enhance the PV cooling by 19 K. The PCM heat sinks can increase the PV electrical efficiency from 13% to 14%. Moreover, the daily electricity generation can be boosted by 7% using PCM and 8% by using FPCM heat sinks. In addition, 7 kWh of thermal output was achieved using the FPCM heat sink, and the overall efficiency of system increased from 13% to 19%.