Mathematical Modelling of Bifacial Dual SIS Solar Cell and Optimization of Tilt Angle

The major challenge of PV cell design and installation has always been to find the optimum cost per energy and area of installation of solar panels. In densely populated and high-yielding agricultural country like India land acquisition is becoming an issue. Moreover the consisting demand to deduce the cost per energy indulges the worldwide scientists to design more efficient solar cells with low production cost. In developing countries scientists and engineers are trying to find an amicable solution to meet up these problems. In this paper the mathematical modelling of a dual SIS bifacial vertically mounted solar panel has been proposed to mitigate the energy and land area crisis in countries of Indian subcontinent, south Asia and elsewhere. The SIS (Semiconductor-Insulator-Semiconductor) technology was chosen for its extremely low thermal budget and less complicated production procedure. A bifacial solar cell with SIS junction in both sides was modelled. The front surface SIS junction was considered ZnO-SiO2-Si(p-type) while the back surface junction was considered Si(p type)-Al2O3-SnO. The efficiency for front and back surface was calculated as 5.64% and 5.58% respectively. We have further considered the effect of albedo from two different surfaces (soil and concrete) and the efficiencies of front and back surface for these albedo radiations. The angle of installation was optimized for both these effects. Considering both direct and albedo the all-day efficiency was calculated as 22.47% for a sunny day tropical region.

Series-connected array of superconductor–insulator–superconductor junctions in the 100 GHz-band heterodyne mixer for FOREST on the Nobeyama 45 m telescope

We have designed and experimentally evaluated a series-connected array of superconductor–insulator–superconductor (SIS) junctions in the 100 GHz-band mixer for the multi-beam receiver FOREST on the Nobeyama 45 m millimeter-wave telescope. The construction of the junction chip comprised a waveguide probe antenna, impedance-matching circuit, SIS array junction, and choke filter, which were made from a superconducting niobium planar circuit on a quartz substrate. The multi-stage impedance-matching circuit between the feed point and the SIS junction was designed as a capacitively loaded transmission line, and it comprised two sections with high (∼90 Ω) and low (∼10 Ω) characteristic impedance transmission lines. The structure of this tuning line was simple and easy to fabricate, and the feed impedance matched with the SIS junction in a wide frequency range. The signal coupling efficiency was more than 92% and the expected receiver noise temperature was approximately twice the quantum limit for 75–125 GHz based on quantum theory. The array junction devices with three to six connected junctions were fabricated and we measured their performance in terms of the receiver noise temperature and gain compression in the laboratory. We successfully developed an array junction device with a receiver noise temperature of ∼15–30 K and confirmed that the improvement in the saturation power corresponded to the number of junctions. The newly developed array junction mixer was installed in the FOREST receiver and it successfully detected the 12CO(J = 1–0) molecular line toward IRC +10216 with the Nobeyama 45 m telescope.