Tandem Modules Research Articles

Structure of mammalian plasma fetuin-B and its mechanism of selective metallopeptidase inhibition.

Mammalian fetuin-A and fetuin-B are abundant serum proteins with pleiotropic functions. Fetuin-B is a highly selective and potent inhibitor of metallo-peptidases (MPs) of the astacin family, which includes ovastacin in mammals. By inhibiting ovastacin, fetuin-B is essential for female fertility. The crystal structure of fetuin-B was determined unbound and in complex with archetypal astacin, and it was found that the inhibitor has tandem cystatin-type modules (CY1 and CY2). They are connected by an exposed linker with a rigid, disulfide-linked 'CPDCP-trunk', and are followed by a C-terminal region (CTR) with little regular secondary structure. The CPDCP-trunk and a hairpin of CY2 form a bipartite wedge, which slots into the active-site cleft of the MP. These elements occupy the nonprimed and primed sides of the cleft, respectively, but spare the specificity pocket so that the inhibitor is not cleaved. The aspartate in the trunk blocks the catalytic zinc of astacin, while the CY2 hairpin binds through a QWVXGP motif. The CY1 module assists in structural integrity and the CTR is not involved in inhibition, as verified by in vitro studies using a cohort of mutants and variants. Overall, the inhibition conforms to a novel 'raised-elephant-trunk' mechanism for MPs, which is reminiscent of single-domain cystatins that target cysteine peptidases. Over 200 sequences from vertebrates have been annotated as fetuin-B, underpinning its ubiquity and physiological relevance; accordingly, sequences with conserved CPDCP- and QWVXGP-derived motifs have been found from mammals to cartilaginous fishes. Thus, the raised-elephant-trunk mechanism is likely to be generally valid for the inhibition of astacins by orthologs of fetuin-B.

GaAs/silicon PVMirror tandem photovoltaic mini‐module with 29.6% efficiency with respect to the outdoor global irradiance

AbstractBalance‐of‐system costs now dominate the installed cost of photovoltaic systems, causing the annually averaged module efficiency to become a primary system cost driver. The resulting continued push towards higher module efficiencies, coupled with the dominance of single‐axis tracking in the utility‐scale PV market, may create an opportunity for a low‐concentration tandem module technology. Here, we demonstrate such a tandem, using the “PVMirror” concept, on the mini‐module scale. The tandem couples a (concentrating) silicon PVMirror having an aperture area of 156.25 cm2 with a gallium arsenide receiver to achieve 29.6% efficiency with respect to the outdoor global irradiance. Unlike most concentrating technologies, the silicon PVMirror collects some of the diffuse light, but the tandem would nevertheless achieve 31% efficiency in the absence of diffuse light, as in a laboratory measurement. The same tandem technology can be implemented with a wide‐bandgap thin‐film PVMirror and silicon receiver—a potentially cost‐competitive combination—when efficient wide‐bandgap cells have been developed.

Inhibition of T Cell Receptor Activation by Semi-Synthetic Sesquiterpene Lactone Derivatives and Molecular Modeling of Their Interaction with Glutathione and Tyrosine Kinase ZAP-70.

A variety of natural compounds have been shown to modulate T cell receptor (TCR) activation, including natural sesquiterpene lactones (SLs). In the present studies, we evaluated the biological activity of 11 novel semi-synthetic SLs to determine their ability to modulate TCR activation. Of these compounds, α-epoxyarglabin, cytisinyl epoxyarglabin, 1β,10α-epoxyargolide, and chloroacetate grosheimin inhibited anti-CD3-induced Ca2+ mobilization and extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation in Jurkat T cells. We also found that the active SLs depleted intracellular glutathione (GSH) in Jurkat T cells, supporting their reactivity towards thiol groups. Because the zeta-chain associated tyrosine kinase 70 kDa (ZAP-70) is essential for TCR signaling and contains a tandem SH2 region that is highly enriched with multiple cysteines, we performed molecular docking of natural SLs and their semi-synthetic derivatives into the ZAP-70 binding site. The docking showed that the distance between the carbon atom of the exocyclic methylene group and the sulfur atom in Cys39 of the ZAP-70 tandem SH2 module was 3.04–5.3 Å for active compounds. Furthermore, the natural SLs and their derivatives could be differentiated by their ability to react with the Cys39 SH-group. We suggest that natural and/or semi-synthetic SLs with an α-methylene-γ-lactone moiety can specifically target GSH and the kinase site of ZAP-70 and inhibit the initial phases of TCR activation.

Characterization of CBM36-containing GH11 endoxylanase NtSymX11 from the hindgut metagenome of higher termite Nasutitermes takasagoensis displaying prominent catalytic activity

Symbionts in the gut of termites are expected to be large sources of enzymes involved in lignocellulose degradation, but their biotechnological potential has not been fully explored. In this study, we expressed, purified, and biochemically characterized a glycoside hydrolase family 11 xylanase, NtSymX11, from a symbiotic bacterium of the higher termite, Nasutitermes takasagoensis. NtSymX11 is a multimodular enzyme consisting of a catalytic domain and two tandem carbohydrate-binding modules (CBM36). The pH and temperature optima of NtSymX11 were pH 6.0 and 40 °C, respectively. By comparing the properties of full-length and truncated variants of NtSymX11, it was shown that CBM36 decreases the enzyme stability at acidic pH and high temperature. The main products from xylohexaose and various xylan substrates were X1-X3 xylooligosaccharides. Analysis of kinetic parameters indicated that NtSymX11 displays an outstanding catalytic performance when compared to other reported xylanases, and CBM36 enhances the activity by increasing the affinity to the substrate. Addition of Ca2+ boosted the activity of full-length enzyme, but not the truncated variant lacking the CBM, against the insoluble substrate, suggesting that CBM36 plays a role in the Ca2+-dependent increase of catalytic efficiency.

Impact of perovskite solar cell degradation on the lifetime energy yield and economic viability of perovskite/silicon tandem modules

Perovskite/silicon two-junction tandem solar cells have achieved higher power conversion efficiency than silicon cells. However, the long-term performance of tandem modules strongly depends on the degradation of perovskite top cells.

Energy yield of all thin‐film perovskite/CIGS tandem solar modules

AbstractPerovskite/CuIn1 − xGaxSe2 (CIGS) tandem photovoltaics (PV) promises high power conversion efficiencies in combination with the advantages of a light weight and an all thin‐film PV technology. However, the complexity of perovskite/CIGS tandem solar module architectures requires careful optimization of the layer stack under realistic solar irradiation conditions. Here, we provide a systematic numerical study on the energy yield (EY) of perovskite/CIGS tandem solar modules, optimizing the device architecture with regard to irradiance in various climate zones. In particular, variations of the spectral irradiation and the average photon energy are of decisive importance for the location‐specific optimization of the device architecture. Compared with the reference single‐junction CIGS thin‐film PV technology, we demonstrate a strong improvement in EY (>30%) in perovskite/CIGS thin‐film PV for perovskites of a wide range of bandgaps (1.55 ‐ 2.0 eV), reaching up to 52% improvement in EY for the optimal bandgap (around 1.8 eV). Of the two most favored architectures, the two‐terminal and four‐terminal devices, perovskite/CIGS tandem solar modules with low bandgap (∼1.55 eV) perovskite absorbers in the four‐terminal architecture outperform those in the two‐terminal architecture in average by 3.5% relative. However, for wide perovskite bandgaps ranging from 1.75 eV to 1.85 eV, both architectures perform comparably. The improvements in EY for perovskite/CIGS tandem solar modules highlight the potential of this technology but also the vital need for light management in tandem photovoltaics.

A Cost Analysis of Fully Solution‐Processed ITO‐Free Organic Solar Modules

AbstractOrganic photovoltaics (OPVs) have become a potential candidate for clean and renewable photovoltaic productions. This work examines the current cost drivers and potential avenues to reduce costs for organic solar modules by constructing a comprehensive bottom‐up cost model. The direct manufacturing cost (MC) and the minimum sustainable price (MSP) for an opaque single solar module (SSM) (MC = 187 ¥ m−2, MSP = 297 ¥ m−2) and for a tandem solar module (MC = 224 ¥ m−2, MSP = 438 ¥ m−2) are analyzed in detail. Within this calculation, the most expensive layers and processing steps are identified and highlighted. Importantly, the low levelized cost of energy (LCOE) value for an SSM with a 10% power conversion efficiency in a 20‐year range from 0.185 to 0.486 ¥ kWh−1, with a national average of 0.324 ¥ kWh−1 in China under an average solar irradiance of 1200 kWh m−2 year−1. Moreover, the impact on the cost of alternative materials and constructions, process throughputs, module efficiency, and module lifetime, etc., is presented and avenues to further reduce the MSP and LCOE values are indicated. The analysis shows that OPVs can emerge as a competitive alternative to established power generation technologies if the remaining issues (e.g., active layer material cost, module efficiency, and lifetime) can be resolved.

Model and experimental validation of a unidirectional phase modulator.

A unidirectional phase modulator consisting of tandem phase modulators is studied in detail for use as an integral part of an integrated optical isolator. The effects of non-linearity and residual amplitude modulation in the modulators, as well as the effect of the RF driving signals are captured in a phenomenological model for the first time. The model has been verified experimentally using a device realized in a generic InP based photonic integration platform and is used to study the operating range of the device. Design parameters of the modulator are derived such that modulation side bands in the forward propagating light are less than 40 dB, while isolation is maximized.

Description of degradation of output performance for photovoltaic modules by multiple regression analysis based on environmental factors

Output performances of multi-crystalline Si (mc-Si), single-crystalline Si (sc-Si), hydrogenated amorphous Si (a-Si), and a-Si/microcrystalline-Si tandem photovoltaic (PV) modules are described using multiple regression analysis based on environmental factors (irradiation intensity on tilted surface (IrrT), angle of incidence (AOI), average photon energy (APE), and module temperature (Tmod)). Since performances of PV modules are normally degraded with time-passing, a term of time (day_number) is added for the description of estimated output energy for high accuracy as compared with actual output energy, where collection periods of the environmental factors for the estimated output energy and actual energy are the same data period (interpolation). It is disclosed that for high accurate output description a term of time is vital for sc-Si, a-Si, and tandem PV modules with time-related degradation, while it is not for mc-Si PV module with small time-related degradation. In addition, the multiple regression analysis using the environmental factors and day_number is successfully utilized based on extending known sequence of these values in years 2004–2006 to describe output energy under their beyond data period of time in years 2007–2009 (extrapolation). This is practical for prediction of energy production in lifetime of PV modules (20–25 years) under consideration of their degradation.

Design Criteria for Micro-Optical Tandem Luminescent Solar Concentrators

Luminescent solar concentrators (LSCs) harness light generated by luminophores embedded in a light-trapping waveguide to concentrate onto smaller cells. LSCs can absorb both direct and diffuse sunlight, and thus can operate as flat plate receivers at a fixed tilt and with a conventional module form factor. However, current LSCs experience significant power loss through parasitic luminophore absorption and incomplete light trapping by the optical waveguide. Here, we introduce a tandem LSC device architecture that overcomes both of these limitations, consisting of a poly(lauryl methacrylate) polymer layer with embedded cadmium selenide core, cadmium sulfide shell (CdSe/CdS) quantum dot (QD) luminophores and an InGaP microcell array, which serves as high bandgap absorbers on the top of a conventional Si photovoltaic. We investigate the design space for a tandem LSC, using experimentally measured performance parameters for key components, including the InGaP microcell array, CdSe/CdS QDs, and spectrally selective waveguide filters. Using a Monte Carlo ray-tracing model, we compute the power conversion efficiency for a tandem LSC module with these components to be 29.4% under partially diffuse illumination conditions. These results indicate that a tandem LSC-on-Si architecture could significantly improve upon the efficiency of a conventional Si photovoltaic cell.

Resonance assignments of a cellulosomal double-dockerin from Clostridium thermocellum.

Cellulosomes are highly efficient multienzyme complexes for lignocellulose degradation secreted by some lignocellulolytic bacteria. Cellulosomes are assembled through protein modules named cohesin and dockerin, and multiple cohesin modules in the scaffold protein generally determine the complexity of the cellulosomes. Some cellulosomal proteins contain multiple dockerin modules, which may generate more complex cellulosomal architectures. Genome mining revealed that cellulosomal proteins containing double dockerin modules and a protease module exist in many cellulosome-producing bacteria, and these proteins together with cellulosomal protease inhibitors were proposed to have regulatory roles. However, the structures and functions of these multiple-dockerin proteins in cellulosome have not been reported before. In this paper, we present the NMR chemical shift assignments of the double-dockerin of a cellulosomal protease from Clostridium thermocellum DSM1313. The secondary structures predicted from the chemical shifts agree with the structural arrangement of the tandem dockerin modules. The chemical shift assignments here provide the basis for the structural and functional studies of multiple-dockerin proteins in future.

Techno-economic viability of silicon-based tandem photovoltaic modules in the United States

Tandem photovoltaic modules with silicon bottom cells offer a promising route to exceed the single-junction photovoltaic efficiency limit and further lower the levelized cost of solar electricity. However, it is unclear whether continued improvements in efficiency will render tandem modules cost-competitive with their two constituent sub-cells, and with silicon technology in particular. Here, we construct a simple and versatile techno-economic model that, for a given balance-of-systems scenario, calculates the tandem module efficiency and cost from assumed sub-cell module efficiencies and costs. To understand which input conditions are likely to be representative of the future photovoltaic market, we calculate learning rates for both module and area-related balance-of-system costs, and find that the slower learning rate of the latter means that high-efficiency tandems will become increasingly attractive. Further, in the residential market in 2020, the model indicates that top-cell modules could cost up to US$100 m–2—over twice that of the projected silicon module cost—and the associated tandem module would be cost-competitive if its energy yield, degradation rate, service life and financing terms are similar to those of silicon. One way to overcome the theoretical efficiency limit of silicon photovoltaics is to use them as the bottom cell in a tandem photovoltaic module. Here a model for tandem module efficiency and cost is presented, based on assumed sub-cell efficiencies and costs, and used to examine possible paths for different tandem markets.

Optical modeling of structured silicon-based tandem solar cells and module stacks.

Silicon-based tandem solar cells and modules are complex systems that require optical modeling for the optimization towards highest efficiencies. The fact that such devices typically incorporate surface structures of different optical regimes poses high requirements to the involved simulation tools. The OPTOS formalism is ideally suited to deal with such complexity. Within this work OPTOS is extended in order to calculate the layer resolved absorptance in silicon-based tandem solar cells and module stacks. After describing the relevant mathematical details, a good agreement between OPTOS absorptance simulation results and EQE measurements of the current 33.3% record efficiency III-V on silicon two-terminal tandem solar cell is found. Furthermore, a detailed loss analysis is performed for an exemplary perovskite silicon solar cell with and without module encapsulation. The comparison reveals a lower photocurrent density for the module stack due to increased reflectance and absorption in the EVA.

Impact of Perovskite/Silicon Tandem Module Design on Hot-Spot Temperature

Organic–inorganic hybrid perovskite materials, as promising candidates for high-efficiency silicon-based tandem solar cells, have passed reliability testing at 85 °C for 1,000 h. However, silicon photovoltaic modules experience elevated temperatures under fault operating conditions. We propose and simulate tandem modules using two- and four-terminal tandem cells and show potential detrimental temperatures under realistic shading conditions. A module using series-connected two-terminal cells reaches 207 °C compared to 137 °C for four-terminal cells from simulation. The cell temperature can be reduced with interdigitated-back-contact cells, additional bypass diodes, or silicon half-cell configurations.

Cost Analysis of Perovskite Tandem Photovoltaics

Summary Recently, metal halide perovskite photovoltaics (PV) are marching toward commercialization. The possibility for perovskite absorbers to be incorporated into multi-junction solar cells is also being discussed, which suggests alternative market entry. Although intensive investigations are being made on their technical feasibility, serious analysis on the cost of perovskite-based tandem modules is lacking. The levelized cost of electricity (LCOE) of solar modules is often used to evaluate technoeconomic competitiveness. Here, we performed a detailed cost analysis on two perovskite-based tandem modules (the perovskite/c-silicon and the perovskite/perovskite tandem module) compared with standard multi-crystalline silicon and single-junction perovskite solar cells. We found that perovskite PVs (both single junction and multi-junction) are competitive in the context of LCOE if the module lifetime is comparable with that of c-silicon solar cells. This encourages further efforts to push perovskite tandem modules onto the market in the future.

Economic viability of thin-film tandem solar modules in the United States

Tandem solar cells are more efficient but more expensive per unit area than established single-junction (SJ) solar cells. To understand when specific tandem architectures should be utilized, we evaluate the cost-effectiveness of different II–VI-based thin-film tandem solar cells and compare them to the SJ subcells. Levelized cost of electricity (LCOE) and energy yield are calculated for four technologies: industrial cadmium telluride and copper indium gallium selenide, and their hypothetical two-terminal (series-connected subcells) and four-terminal (electrically independent subcells) tandems, assuming record SJ quality subcells. Different climatic conditions and scales (residential and utility scale) are considered. We show that, for US residential systems with current balance-of-system costs, the four-terminal tandem has the lowest LCOE because of its superior energy yield, even though it has the highest US$ per watt (US$ W–1) module cost. For utility-scale systems, the lowest LCOE architecture is the cadmium telluride single junction, the lowest US$ W–1 module. The two-terminal tandem requires decreased subcell absorber costs to reach competitiveness over the four-terminal one. Multijunction solar cells are more efficient and more expensive than single-junction photovoltaic cells, but their cost-effectiveness remains unclear. Here, Sofia et al. study the manufacturing costs of thin-film devices to analyse the levelized cost of electricity of single and multijunctions in the United States.

Crystal structures of the extracellular domains of the CrRLK1L receptor-like kinases ANXUR1 and ANXUR2.

Catharanthus roseus Receptor-Like Kinase 1-like (CrRLK1L) proteins contain two tandem malectin-like modules in their extracellular domains (ECDs) and function in diverse signaling pathways in plants. Malectin is a carbohydrate-binding protein in animals and recognizes a number of diglucosides; however, it remains unclear how the two malectin-like domains in the CrRLK1L proteins sense the ligand molecule. In this study, we reveal the crystal structures of the ECDs of ANXUR1 and ANXUR2, two CrRLK1L members in Arabidopsis thaliana that have critical functions in controlling pollen tube rupture during the fertilization process. We show that the two malectin-like domains in these proteins pack together to form a rigid architecture. Unlike animal malectin, these malectin-like domains lack residues involved in binding to the diglucosides, suggesting that they have a distinct ligand-binding mechanism. A cleft is observed between the two malectin-like domains, which might function as a potential ligand-binding pocket.

A comparative life cycle assessment of chalcogenide/Si tandem solar modules

Tandem technologies offer potential price reductions and higher efficiencies of PV modules. The high band gap nature of chalcogenides like CIGS, CZTS and AZTS makes them excellent materials for use on top of a Si base tandem cells. Nevertheless, along with the search for new technologies, there is also the concern about the environmental impact that its lifetime can cause. A comprehensive life cycle assessment for CIGS/Si, CZTS/Si and AZTS/Si tandem solar modules was not reported to date. This work compares the environmental impacts of Si and chalcogenide/Si tandem solar modules, assessing global warming potential, human toxicity potential (cancer and non-cancer effects), freshwater eutrophication potential, freshwater ecotoxicity potential, abiotic depletion potential and the energy payback time of these technologies. The results of this study show that compared with Si, CIGS/Si presents worse environmental impacts for most of the categories but, on the other hand, CZTS/Si and AZTS/Si present better outcomes for most of the impacts categories. We can also say that higher efficiency of these tandem technologies could potentially reverse that result. This LCA provides design advice for the R&D community, showing which structure has the best environmental outcomes and which processes should be optimized to achieve better results.

Energy yield modelling of perovskite/silicon two-terminal tandem PV modules with flat and textured interfaces

Textured perovskite/silicon tandem photovoltaic modules are compared to state-of-the-art silicon single-junction photovoltaic modules by annual energy yield modelling.

Perovskite–silicon tandem solar modules with optimised light harvesting

Demonstration of efficient, large-area scalable perovskite–silicon tandem solar modules with optimised light management.