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In the context of solar tower power, the significance of the receiver has to do with its capacity to convert sun rays into heat. This heat is then conveyed to a heat transfer fluid. The extremely high velocity of the heat transfer fluid, motivates for the use of smart geometry to simultaneously enhance the heat transfer process and strengthen the structure of the tubes. In this study, a new molten salt receiver design was numerically investigated, following the addition of square, rectangular, circular and triangular longitudinal fins, that come at various heights (w=1,2,4 and 6 mm). Molten salt was used as the heat transfer fluid that flown through the receiver tubes with the Reynolds number ranging between 14,000 and 38,000. In comparison to a smooth tube, it was observed that while the inclusion of fins led to a dip in pressure, the overall efficiency level was improved. An increase in the number of fins, led to an improvement in the heat transfer process. The use of four square fins delivered the highest heat transfer enhancement. In the use of a singular fin, a triangular fin with a height of 1 mm delivered the best heat transfer performance. For a similar flow rate and hydraulic area, the triangular fins exhibited a better heat transfer performance than the square, circular and rectangular fins. In terms of the receiver's efficiency, the triangular fins produced the heights efficiency.

This study was performed in outdoor conditions to quantify the level of influence on the electrical performance of the Multi-junction (MJ) solar cells. It was discovered that non-uniform illumination on the solar cell could reduce the MJ electrical output by more than 40%. Also, the irradiation uniformity was improved by applying several methods; increasing the distance between the concentrator and the receiver (l) and introducing a secondary optical element (SOE) on the receiver. The outdoor measurement also revealed that the electrical efficiency of the solar cell increased from around 22% to 37% with an increment of 68%, due to improvement of irradiation uniformity. However, the optical efficiency substantially fell when increasing the distance (l). To address this issue, a 0.06 m high SOE having a surface reflectivity of 90% above the PV assembly was implemented to enhance the irradiation uniformity and to minimise the dramatic decline in optical efficiency. The hot spot initiated by non-uniform illumination was also examined in outdoor conditions by measuring the temperature at the centre and both sides of the PV cell. Accordingly, a variance of about 13 K was observed between the centre and both sides (0.005 m distance) of the PV cell's surface area, which was further reduced to 1 K after improving the illumination uniformity.

Concentrating solar radiation on Photovoltaic (PV) has the potential to replace the expensive PV material with cheaper optical elements which also enhance the overall electrical output. The use of high solar concentration ratios with the triple junction III-V solar cells offers potential of high solar cell efficiency and power output. However, using high concentration ratios will increase the solar cell surface temperature which is inversely proportional to the PV electrical efficiency. This work investigates the effect of active cooling on the performance of triple junction PV cells with high solar concentration (up to 500X) in the harsh environment of Saudi Arabia where ambient temperatures can reach to 50 o C in summer time, but with good clearance index of 0.6 and high yearly solar radiation of up to 2200 kWh/m 2 . Simulation results showed that as the concentration ratio increases, the effect of cooling on the PV efficiency increases.