[en] As single junction photovoltaic (PV) technologies, both Si heterojunction (HIT) and perovskite based solar cells promise high efficiencies at low cost. Intuitively, a traditional tandem cell design with these cells connected in series is expected to improve the efficiency further. Using a self-consistent numerical modeling of optical and transport characteristics, however, we find that a traditional series connected tandem design suffers from low J_SC due to band-gap mismatch and current matching constraints. Furthermore, a traditional tandem cell with state-of-the-art HIT (η = 24%) and perovskite (η = 20%) sub-cells provides only a modest tandem efficiency of η_T~ 25%. Instead, we demonstrate that a bifacial HIT/perovskite tandem design decouples the optoelectronic constraints and provides an innovative path for extraordinary efficiencies. In the bifacial configuration, the same state-of-the-art sub-cells achieve a normalized output of η_T* = 33%, exceeding the bifacial HIT performance at practical albedo reflections. Unlike the traditional design, this bifacial design is relatively insensitive to perovskite thickness variations, which may translate to simpler manufacture and higher yield.

[en] We present our scientific and philosophical analysis of the comments made in the recent paper of A.P. Kirk, “An Analysis of Quantum Coherent Solar Photovoltaic Cells” Physica B 407 (2012) 544. We highlight the key role of quantum coherence in the enhancement of the photocell power without violating the laws of thermodynamics

No abstract available

[en] Perovskite solar cells exhibiting ~ 14–15% efficiency were experimentally measured using current–voltage (I–V) and capacitance–voltage (C–V) techniques in order to extract material and device properties, and understand the action of photovoltaic (PV) operation. Deep analyses were carried out on dark- and illuminated I–V curves, and dark C–V curves. Results were compared with those of graded bandgap solar cells fabricated on inorganic n-type window layers. These analyses according to a physicist’s point of view lead to understand the perovskite solar cell as a graded bandgap solar cell built on a p-type window layer. I–V and C–V results show very similar behaviour and the principle of PV action is identical. Once the stability issues with perovskites are solved, these devices have very high potential of producing next generation solar cells reaching at least mid-20% efficiency values.

[en] Due largely to recent dramatic cost reductions, photovoltaics (PVs) are poised to make a significant contribution to electricity supply. In particular, distributed applications of PV on rooftops, brownfields, and other similar applications – hold great technical potential. In order for this potential to be realized, however, PV must be “cost-effective”—that is, it must be sufficiently financially appealing to attract large amounts of investment capital. Electricity costs for most commercial and industrial end-users come in two forms: consumption (kWh) and demand (kW). Although rates vary, for a typical larger commercial or industrial user, demand charges account for about ∼40% of total electricity costs. This paper uses a case study of PV on a large university campus to reveal that even very large PV installations will often provide very small demand reductions. As a result, it will be very difficult for PV to demonstrate cost-effectiveness for large commercial customers, even if PV costs continue to drop. If policymakers would like PV to play a significant role in electricity generation – for economic development, carbon reduction, or other reasons – then rate structures will need significant adjustment, or improved distributed storage technologies will be needed. - Highlights: ► Demand charges typically account for ∼40% of total electricity costs for larger electricity users. ► Distributed photovoltaic (PV) systems provide minimal demand charge reductions. ► As a result, PVs are not a financially viable alternative to centralized electricity. ► Electricity rate structures will need changes for PV to be a major electricity source.

[en] Highlights: ► To improve the efficiency of PV systems, under different temperature and irradiance conditions. ► The MPPT and different control method for the induction motor were applied. ► The DTC in PV pumping system introduced and performance studied. ► The introductions of DTC in PV systems are very promising. ► Optimizing the water pumping system speed response characteristic by DTC. - Abstract: We aim to find a better control and optimization among the different functions of a solar pumping system. The photovoltaic panel can provide a maximum power only for defined output voltage and current. In addition, the operation to get the maximum power depends on the terminals of load, mostly a non-linear load like induction motor. In this work, we propose an intelligent control method for the maximum power point tracking of a photovoltaic system under variable temperature and irradiance conditions. The system was tested without maximum power point tracking, with the use of Scalar-Based control motor, but we cannot maintain the speed optimal. Next, we developed several methods for the control. Finally, we have chosen the Direct Torque Control.

[en] Highlights: • Failure rates and modes analysis of photovoltaic plants. . • Historical failures data and photovoltaic operators' perspective analysis. . • Review of failures frequencies in photovoltaic plants. . • Photovoltaic failure rates for its application in FMEA analysis . -- Abstract: The greater challenge that researchers address and indicate while investigating about photovoltaic (PV) system failures during their Operation and Maintenance (O&M) is the lack of accessible reliable real quantitative data. For this reason, several publications have focused on this problem through a qualitative approach. However, this fact is one of the greater strengths of this paper, in which the quantitative information from the historical data of sixty-three PV plants portfolio in Italy and Spain has been accessible. Results obtained from the research provide essential information for main players involved in PV plants to identify failure modes and rates, in order to reduce investment risk and to focus their maintenance efforts on preventing those failures, improving longevity and performance of PV plants. The paper presents failure rates per PV Site and per kW, considering all portfolio and dividing it regarding five PV plants groups per size, distribution of failures per element, Mean Time Between Failures (MTBF), reparation times per affected element and the main failures modes examining each of the almost 100,000 complete alarms registered during the five years analyzed.

[en] The author responds to the attempted tutorial (Chapin et al., Physica B (2013) [6]) on solar cell physics specifically as it relates to the hypothetical toy model quantum coherent solar cell (Scully, Phys. Rev. Lett. 104 (2010) 207701 [1])

[en] Highlights: * Employing an organic triphenylamine dye as heterojunction interfacial modifier. * The use of modifier facilitates the compatibility between TiO₂ and P3HT. * Interfacial modification promotes exciton dissociation, reduces charge recombination. * V_oc and J_sc enhanced obviously, that improved photovoltaic performance to 2.01%. Interface control is an important approach in polymer based solar cells because the interface properties on bulk heterojunction can govern the device performance. We select an organic triphenylamine-type sensitizer to tune the interfacial characters in TiO₂ nanorod array/poly(3-hexylthiophene) (P3HT) hybrid solar cell device. In addition to physically improving the compatibility between TiO₂ nanorod and polymer contact junction, the introduction of modifier reduces the charge recombination, prolongs the electron lifetime, and thus optimizes the device performance.

[en] This paper presents a critical view of Florida's photovoltaic (PV) subsidy system and proposes an econometric model of PV system installation and generation costs. Using information on currently installed systems, average installation cost relations for residential and commercial systems are estimated and cost-efficient scales of installation panel wattage are identified. Productive efficiency in annual generating capacity is also examined under flexible panel efficiency assumptions. We identify potential gains in efficiency and suggest changes in subsidy system constraints, providing important guidance for the implementation of future incentive programs. Specifically, we find that the subsidy system discouraged residential applicants from installing at the cost-efficient scale but over-incentivized commercial applicants, resulting in inefficiently sized installations. - Highlights: ► Describe a PV solar incentive system in the U.S. state of Florida. ► Combine geocoded installation site data with a detailed irradiance map. ► Estimate installation and production costs across a large sample. ► Identify inefficiencies in the incentive system. ► Suggest changes to policy that would improve economic efficiency.