Author Correction: Pairing of near-ultraviolet solar cells with electrochromic windows for smart management of the solar spectrum Nat. Energy Pub Date : 2017-09-18 Nicholas C. Davy, Melda Sezen-Edmonds, Jia Gao, Xin Lin, Amy Liu, Nan Yao, Antoine Kahn, Yueh-Lin Loo
Author Correction: Pairing of near-ultraviolet solar cells with electrochromic windows for smart management of the solar spectrumNature Energy, Published online: 18 September 2017; doi:10.1038/s41560-017-0017-8
Stretchable and waterproof elastomer-coated organic photovoltaics for washable electronic textile applications Nat. Energy Pub Date : 2017-09-18 Hiroaki Jinno, Kenjiro Fukuda, Xiaomin Xu, Sungjun Park, Yasuhito Suzuki, Mari Koizumi, Tomoyuki Yokota, Itaru Osaka, Kazuo Takimiya, Takao Someya
Textile-compatible photovoltaics play a crucial role as a continuous source of energy in wearable devices. In contrast to other types of energy harvester, they can harvest sufficient electricity (on the order of milliwatts) for wearable devices by utilizing the cloth itself as the platform for photovoltaics. Three features are important for textile-compatible photovoltaics, namely environmental stability, sufficient energy efficiency and mechanical robustness. However, achieving these simultaneously remains difficult because of the low gas barrier properties of ultrathin superstrates and substrates. Here, we report on ultraflexible organic photovoltaics coated on both sides with elastomer that simultaneously realize stretchability and stability in water whilst maintaining a high efficiency of 7.9%. The efficiency of double-side-coated devices decreases only by 5.4% after immersion in water for 120 min. Furthermore, the efficiency of the devices remains at 80% of the initial value even after 52% mechanical compression for 20 cycles with 100 min of water exposure.
High-resolution assessment of global technical and economic hydropower potential Nat. Energy Pub Date : 2017-09-18 David E. H. J. Gernaat, Patrick W. Bogaart, Detlef P. van Vuuren, Hester Biemans, Robin Niessink
Hydropower is the most important renewable energy source to date, providing over 72% of all renewable electricity globally. Yet, only limited information is available on the global potential supply of hydropower and the associated costs. Here we provide a high-resolution assessment of the technical and economic potential of hydropower at a near-global scale. Using 15”×15” discharge and 3”×3” digital elevation maps, we built virtual hydropower installations at >3.8 million sites across the globe and calculated their potential using cost optimization methods. This way we identified over 60,000 suitable sites, which together represent a remaining global potential of 9.49 PWh yr−1 below US$0.50 kWh−1. The largest remaining potential is found in Asia Pacific (39%), South America (25%) and Africa (24%), of which a large part can be produced at low cost (
Washing away barriers Nat. Energy Pub Date : 2017-09-18 Ning Li, Christoph J. Brabec
Washing away barriers Nature Energy, Published online: 18 September 2017; doi:10.1038/s41560-017-0011-1 Light-weight and stretchable, organic photovoltaics offer unique integration prospects. Now, organic solar cells and modules can also be washed while maintaining good photoconversion efficiencies.
Energy policy: Guiding green lighting Nat. Energy Pub Date : 2017-09-12 Nicky Dean
Energy policy: Guiding green lightingNature Energy, Published online: 12 September 2017; doi:10.1038/nenergy.2017.146
Solar heating: Warm with thy neighbour Nat. Energy Pub Date : 2017-09-12 Elsa Couderc
Solar heating: Warm with thy neighbourNature Energy, Published online: 12 September 2017; doi:10.1038/nenergy.2017.147
Business as unusual Nat. Energy Pub Date : 2017-09-12
Business as unusualNature Energy, Published online: 12 September 2017; doi:10.1038/nenergy.2017.150Energy models provide powerful insights for decision-makers, but more care is needed around the choice of reference scenarios and the transparency of assumptions.
Oil production: Impact of age Nat. Energy Pub Date : 2017-09-12 James Gallagher
Oil production: Impact of ageNature Energy, Published online: 12 September 2017; doi:10.1038/nenergy.2017.148
Aqueous batteries: Versatile quinones Nat. Energy Pub Date : 2017-09-12 Changjun Zhang
Aqueous batteries: Versatile quinonesNature Energy, Published online: 12 September 2017; doi:10.1038/nenergy.2017.149
Radiative cooling: Energy savings from the sky Nat. Energy Pub Date : 2017-09-04 Geoff Smith, Angus Gentle
Radiative cooling: Energy savings from the sky Nature Energy, Published online: 4 September 2017; doi:10.1038/nenergy.2017.142 Environmental heat sinks beyond local air are available for use with normal air conditioners to increase their efficiency. A study has exploited outer space and the atmosphere as remote sinks to demonstrate daytime sub-ambient fluid cooling and its application in reducing the energy needed to cool an interior.
Sub-ambient non-evaporative fluid cooling with the sky Nat. Energy Pub Date : 2017-09-04 Eli A. Goldstein, Aaswath P. Raman, Shanhui Fan
Cooling systems consume 15% of electricity generated globally and account for 10% of global greenhouse gas emissions. With demand for cooling expected to grow tenfold by 2050, improving the efficiency of cooling systems is a critical part of the twenty-first-century energy challenge. Building upon recent demonstrations of daytime radiative sky cooling, here we demonstrate fluid cooling panels that harness radiative sky cooling to cool fluids below the air temperature with zero evaporative losses, and use almost no electricity. Over three days of testing, we show that the panels cool water up to 5 ∘C below the ambient air temperature at water flow rates of 0.2 l min−1 m−2, corresponding to an effective heat rejection flux of up to 70 W m−2. We further show through modelling that, when integrated on the condenser side of the cooling system of a two-storey office building in a hot dry climate (Las Vegas, USA), electricity consumption for cooling during the summer could be reduced by 21% (14.3 MWh).
The underestimated potential of solar energy to mitigate climate change Nat. Energy Pub Date : 2017-08-25 Felix Creutzig, Peter Agoston, Jan Christoph Goldschmidt, Gunnar Luderer, Gregory Nemet, Robert C. Pietzcker
The Intergovernmental Panel on Climate Change's fifth assessment report emphasizes the importance of bioenergy and carbon capture and storage for achieving climate goals, but it does not identify solar energy as a strategically important technology option. That is surprising given the strong growth, large resource, and low environmental footprint of photovoltaics (PV). Here we explore how models have consistently underestimated PV deployment and identify the reasons for underlying bias in models. Our analysis reveals that rapid technological learning and technology-specific policy support were crucial to PV deployment in the past, but that future success will depend on adequate financing instruments and the management of system integration. We propose that with coordinated advances in multiple components of the energy system, PV could supply 30–50% of electricity in competitive markets.
Raising the one-sun conversion efficiency of III–V/Si solar cells to 32.8% for two junctions and 35.9% for three junctions Nat. Energy Pub Date : 2017-08-25 Stephanie Essig, Christophe Allebé, Timothy Remo, John F. Geisz, Myles A. Steiner, Kelsey Horowitz, Loris Barraud, J. Scott Ward, Manuel Schnabel, Antoine Descoeudres, David L. Young, Michael Woodhouse, Matthieu Despeisse, Christophe Ballif, Adele Tamboli
Today’s dominant photovoltaic technologies rely on single-junction devices, which are approaching their practical efficiency limit of 25–27%. Therefore, researchers are increasingly turning to multi-junction devices, which consist of two or more stacked subcells, each absorbing a different part of the solar spectrum. Here, we show that dual-junction III–V//Sidevices with mechanically stacked, independently operated III–V and Si cells reach cumulative one-sun efficiencies up to 32.8%. Efficiencies up to 35.9% were achieved when combining a GaInP/GaAs dual-junction cell with a Si single-junction cell. These efficiencies exceed both the theoretical 29.4% efficiency limit of conventional Si technology and the efficiency of the record III–V dual-junction device (32.6%), highlighting the potential of Si-based multi-junction solar cells. However, techno-economic analysis reveals an order-of-magnitude disparity between the costs for III–V//Si tandem cells and conventional Si solar cells, which can be reduced if research advances in low-cost III–V growth techniques and new substrate materials are successful.
Withdrawing from the Paris climate agreement hurts the US Nat. Energy Pub Date : 2017-08-25 Jason Bordoff
Withdrawing from the Paris climate agreement hurts the US Nature Energy, Published online: 25 August 2017; doi:10.1038/nenergy.2017.145 The Trump administration's domestic plans would have curtailed the nation's climate action even if it had stayed in the Paris Agreement. Yet, the decision to leave the agreement undermines US international energy and climate leadership and the prospects of ramping up global climate policy ambition.
The climate and air-quality benefits of wind and solar power in the United States Nat. Energy Pub Date : 2017-08-14 Dev Millstein, Ryan Wiser, Mark Bolinger, Galen Barbose
Wind and solar energy reduce combustion-based electricity generation and provide air-quality and greenhouse gas emission benefits. These benefits vary dramatically by region and over time. From 2007 to 2015, solar and wind power deployment increased rapidly while regulatory changes and fossil fuel price changes led to steep cuts in overall power-sector emissions. Here we evaluate how wind and solar climate and air-quality benefits evolved during this time period. We find cumulative wind and solar air-quality benefits of 2015 US$29.7–112.8 billion mostly from 3,000 to 12,700 avoided premature mortalities, and cumulative climate benefits of 2015 US$5.3–106.8 billion. The ranges span results across a suite of air-quality and health impact models and social cost of carbon estimates. We find that binding cap-and-trade pollutant markets may reduce these cumulative benefits by up to 16%. In 2015, based on central estimates, combined marginal benefits equal 7.3 ¢ kWh−1 (wind) and 4.0 ¢ kWh−1 (solar).
Efficient ambient-air-stable solar cells with 2D–3D heterostructured butylammonium-caesium-formamidinium lead halide perovskites Nat. Energy Pub Date : 2017-08-14 Zhiping Wang, Qianqian Lin, Francis P. Chmiel, Nobuya Sakai, Laura M. Herz, Henry J. Snaith
Perovskite solar cells are remarkably efficient; however, they are prone to degradation in water, oxygen and ultraviolet light. Cation engineering in 3D perovskite absorbers has led to reduced degradation. Alternatively, 2D Ruddlesden–Popper layered perovskites exhibit improved stability, but have not delivered efficient solar cells so far. Here, we introduce n-butylammonium cations into a mixed-cation lead mixed-halide FA0.83Cs0.17Pb(IyBr1−y)3 3D perovskite. We observe the formation of 2D perovskite platelets, interspersed between highly orientated 3D perovskite grains, which suppress non-radiative charge recombination. We investigate the relationship between thin-film composition, crystal alignment and device performance. Solar cells with an optimal butylammonium content exhibit average stabilized power conversion efficiency of 17.5 ± 1.3% with a 1.61-eV-bandgap perovskite and 15.8 ± 0.8% with a 1.72-eV-bandgap perovskite. The stability under simulated sunlight is also enhanced. Cells sustain 80% of their ‘post burn-in’ efficiency after 1,000 h in air, and close to 4,000 h when encapsulated.
Energy innovation: Disinterest impedes adoption Nat. Energy Pub Date : 2017-08-08 Jenn Richler
Energy innovation: Disinterest impedes adoption Nature Energy, Published online: 8 August 2017; doi:10.1038/nenergy.2017.136
Thermoelectrics: Invisible harvest Nat. Energy Pub Date : 2017-08-08 Elsa Couderc
Thermoelectrics: Invisible harvest Nature Energy, Published online: 8 August 2017; doi:10.1038/nenergy.2017.137
Fuel cells: Making membranes Nat. Energy Pub Date : 2017-08-08 James Gallagher
Fuel cells: Making membranes Nature Energy, Published online: 8 August 2017; doi:10.1038/nenergy.2017.138
Conditions for capture Nat. Energy Pub Date : 2017-08-08
Conditions for capture Nature Energy, Published online: 8 August 2017; doi:10.1038/nenergy.2017.141 Recent large-scale carbon-capture schemes in the energy sector point to progress, but further development and support are still required to improve viability and widespread deployment.
Electrochemical storage: Liquefied gas solvents Nat. Energy Pub Date : 2017-08-08 Changjun Zhang
Electrochemical storage: Liquefied gas solvents Nature Energy, Published online: 8 August 2017; doi:10.1038/nenergy.2017.139
Bioinspired catalytic materials for energy-relevant conversions Nat. Energy Pub Date : 2017-08-07 Vincent Artero
Bioinspired catalytic materials for energy-relevant conversions Nature Energy, Published online: 7 August 2017; doi:10.1038/nenergy.2017.131 The structure of active sites of enzymes involved in bioenergetic processes can inspire design of active, stable and cost-effective catalysts for renewable-energy technologies. For these materials to reach maturity, the benefits of bioinspired systems must be combined with practical technological requirements.
Li–air batteries: Decouple to stabilize Nat. Energy Pub Date : 2017-08-07 Ji-Jing Xu, Xin-Bo Zhang
Li–air batteries: Decouple to stabilize Nature Energy, Published online: 7 August 2017; doi:10.1038/nenergy.2017.133 The utilization of porous carbon cathodes in lithium–air batteries is hindered by their severe decomposition during battery cycling. Now, dual redox mediators are shown to decouple the complex electrochemical reactions at the cathode, avoiding cathode passivation and decomposition.
Energy storage deployment and innovation for the clean energy transition Nat. Energy Pub Date : 2017-07-31 Noah Kittner, Felix Lill, Daniel M. Kammen
The clean energy transition requires a co-evolution of innovation, investment, and deployment strategies for emerging energy storage technologies. A deeply decarbonized energy system research platform needs materials science advances in battery technology to overcome the intermittency challenges of wind and solar electricity. Simultaneously, policies designed to build market growth and innovation in battery storage may complement cost reductions across a suite of clean energy technologies. Further integration of R&D and deployment of new storage technologies paves a clear route toward cost-effective low-carbon electricity. Here we analyse deployment and innovation using a two-factor model that integrates the value of investment in materials innovation and technology deployment over time from an empirical dataset covering battery storage technology. Complementary advances in battery storage are of utmost importance to decarbonization alongside improvements in renewable electricity sources. We find and chart a viable path to dispatchable US$1 W−1 solar with US$100 kWh−1 battery storage that enables combinations of solar, wind, and storage to compete directly with fossil-based electricity options.
Self-optimizing, highly surface-active layered metal dichalcogenide catalysts for hydrogen evolution Nat. Energy Pub Date : 2017-07-31 Yuanyue Liu, Jingjie Wu, Ken P. Hackenberg, Jing Zhang, Y. Morris Wang, Yingchao Yang, Kunttal Keyshar, Jing Gu, Tadashi Ogitsu, Robert Vajtai, Jun Lou, Pulickel M. Ajayan, Brandon C. Wood, Boris I. Yakobson
Low-cost, layered transition-metal dichalcogenides (MX2) based on molybdenum and tungsten have attracted substantial interest as alternative catalysts for the hydrogen evolution reaction (HER). These materials have high intrinsic per-site HER activity; however, a significant challenge is the limited density of active sites, which are concentrated at the layer edges. Here we unravel electronic factors underlying catalytic activity on MX2 surfaces, and leverage the understanding to report group-5 MX2 (H-TaS2 and H-NbS2) electrocatalysts whose performance instead mainly derives from highly active basal-plane sites, as suggested by our first-principles calculations and performance comparisons with edge-active counterparts. Beyond high catalytic activity, they are found to exhibit an unusual ability to optimize their morphology for enhanced charge transfer and accessibility of active sites as the HER proceeds, offering a practical advantage for scalable processing. The catalysts reach 10 mA cm−2 current density at an overpotential of ∼50–60 mV with a loading of 10–55 μg cm−2, surpassing other reported MX2 candidates without any performance-enhancing additives.
Hydrogen evolution: Not living on the edge Nat. Energy Pub Date : 2017-07-31 Danielle N. Chirdon, Yiying Wu
Hydrogen evolution: Not living on the edge Nature Energy, Published online: 31 July 2017; doi:10.1038/nenergy.2017.132 Transition-metal dichalcogenides are appealing catalysts for H2 generation from water. They tend to rely on scarce edge sites, rather than the more abundant basal-plane sites, to drive catalysis. Now, guided by computation, H-TaS2 and H-NbS2 are proposed as highly basal-plane-active catalysts that improve with electrochemical cycling.
A rechargeable lithium–oxygen battery with dual mediators stabilizing the carbon cathode Nat. Energy Pub Date : 2017-07-31 Xiangwen Gao, Yuhui Chen, Lee R. Johnson, Zarko P. Jovanov, Peter G. Bruce
At the cathode of a Li–O2 battery, O2 is reduced to Li2O2 on discharge, the process being reversed on charge. Li2O2 is an insulating and insoluble solid, leading ultimately to low rates, low capacities and early cell death if formed on the cathode surface. Here we show that when using dual mediators, 2,5-Di-tert-butyl-1,4-benzoquinone [DBBQ] on discharge and 2,2,6,6-tetramethyl-1-piperidinyloxy [TEMPO] on charge, the electrochemistry at the cathode surface is decoupled from Li2O2 formation/decomposition in solution. Capacities of 2 mAh cmareal−2 at 1 mA cmareal−2 with low polarization on charge/discharge are demonstrated, and up to 40 mAh cmareal−2 at rates ≫1 mA cmareal−2 are anticipated if suitable gas diffusion electrodes can be devised. One of the major barriers to the progress of Li–O2 cells is decomposition of the carbon cathode. By forming/decomposing Li2O2 in solution and avoiding high charge potentials, the carbon instability is significantly mitigated (<0.008% decomposition per cycle compared with 0.12% without mediators).
A facile surface chemistry route to a stabilized lithium metal anode Nat. Energy Pub Date : 2017-07-31 Xiao Liang, Quan Pang, Ivan R. Kochetkov, Marina Safont Sempere, He Huang, Xiaoqi Sun, Linda F. Nazar
Lithium metal is a highly desirable anode for lithium rechargeable batteries, having the highest theoretical specific capacity and lowest electrochemical potential of all material candidates. Its most notable problem is dendritic growth upon Li plating, which is a major safety concern and exacerbates reactivity with the electrolyte. Here we report that Li-rich composite alloy films synthesized in situ on lithium by a simple and low-cost methodology effectively prevent dendrite growth. This is attributed to the synergy of fast lithium ion migration through Li-rich ion conductive alloys coupled with an electronically insulating surface component. The protected lithium is stabilized to sustain electrodeposition over 700 cycles (1,400 h) of repeated plating/stripping at a practical current density of 2 mA cm−2 and a 1,500 cycle-life is realized for a cell paired with a Li4Ti5O12 positive electrode. These findings open up a promising avenue to stabilize lithium metal with surface layers having targeted properties.
Efficient and equitable spatial allocation of renewable power plants at the country scale Nat. Energy Pub Date : 2017-07-24 Martin Drechsler, Jonas Egerer, Martin Lange, Frank Masurowski, Jürgen Meyerhoff, Malte Oehlmann
Globally, the production of renewable energy is undergoing rapid growth. One of the most pressing issues is the appropriate allocation of renewable power plants, as the question of where to produce renewable electricity is highly controversial. Here we explore this issue through analysis of the efficient and equitable spatial allocation of wind turbines and photovoltaic power plants in Germany. We combine multiple methods, including legal analysis, economic and energy modelling, monetary valuation and numerical optimization. We find that minimum distances between renewable power plants and human settlements should be as small as is legally possible. Even small reductions in efficiency lead to large increases in equity. By considering electricity grid expansion costs, we find a more even allocation of power plants across the country than is the case when grid expansion costs are neglected.
Renewable deployment: Model for a fairer distribution Nat. Energy Pub Date : 2017-07-24 Philipp Grunewald
Renewable deployment: Model for a fairer distribution Nature Energy, Published online: 24 July 2017; doi:10.1038/nenergy.2017.130 Typically, the allocation of renewable power sources is determined by a desire to maximize output and reduce generation costs in order to satisfy the preferences of a small number of stakeholders. A new model broadens this perspective by considering societal equity and acceptability, with the aim of improving the siting process.
A materials perspective on Li-ion batteries at extreme temperatures Nat. Energy Pub Date : 2017-07-24 Marco-Tulio F. Rodrigues, Ganguli Babu, Hemtej Gullapalli, Kaushik Kalaga, Farheen N. Sayed, Keiko Kato, Jarin Joyner, Pulickel M. Ajayan
With the continuous upsurge in demand for energy storage, batteries are increasingly required to operate under extreme environmental conditions. Although they are at the technological forefront, Li-ion batteries have long been limited to room temperature, as internal phenomena during their operation cause thermal fluctuations. This has been the reason for many battery explosions in recent consumer products. While traditional efforts to address these issues focused on thermal management strategies, the performance and safety of Li-ion batteries at both low (<20 °C) and high (>60 °C) temperatures are inherently related to their respective components, such as electrode and electrolyte materials and the so-called solid-electrolyte interphases. This Review examines recent research that considers thermal tolerance of Li-ion batteries from a materials perspective, spanning a wide temperature spectrum (−60 °C to 150 °C). The structural stability of promising cathodes, issues with anode passivation, and the competency of various electrolyte, binder and current collectors are compared for their thermal workability. The possibilities offered by each of these cell components could extend the environmental frontiers of commercial Li-ion batteries.
Climate change and the vulnerability of electricity generation to water stress in the European Union Nat. Energy Pub Date : 2017-07-24 Paul Behrens, Michelle T. H. van Vliet, Tijmen Nanninga, Brid Walsh, João F. D. Rodrigues
Thermoelectric generation requires large amounts of water for cooling. Recent warm periods have led to curtailments in generation, highlighting concerns about security of supply. Here we assess EU-wide climate impacts for 1,326 individual thermoelectric plants and 818 water basins in 2020 and 2030. We show that, despite policy goals and a decrease in electricity-related water withdrawal, the number of regions experiencing some reduction in power availability due to water stress rises from 47 basins to 54 basins between 2014 and 2030, with further plants planned for construction in stressed basins. We examine the reasons for these pressures by including water demand for other uses. The majority of vulnerable basins lie in the Mediterranean region, with further basins in France, Germany and Poland. We investigate four adaptations, finding that increased future seawater cooling eases some pressures. This highlights the need for an integrated, basin-level approach in energy and water policy.
Energy justice: Participation promotes acceptance Nat. Energy Pub Date :
Energy justice: Participation promotes acceptance Nature Energy, Published online: 17 July 2017; doi:10.1038/nenergy.2017.128 Wind turbines have been a go-to technology for addressing climate change, but they are increasingly a source of frustration for all stakeholders. While community ownership is often lauded as a panacea for maximizing turbine acceptance, a new study suggests that decision-making involvement — procedural fairness — matters most.
Distributed energy resources: Planning for the future Nat. Energy Pub Date :
Distributed energy resources: Planning for the future Nature Energy, Published online: 17 July 2017; doi:10.1038/nenergy.2017.129 Distributed energy resources will play a fundamental role in providing low-carbon electricity in a smart, flexible way. A new study develops a cross-disciplinary planning tool showing that ‘going distributed’ always pays.
Data-driven planning of distributed energy resources amidst socio-technical complexities Nat. Energy Pub Date :
Data-driven planning of distributed energy resources amidst socio-technical complexities Nature Energy, Published online: 17 July 2017; doi:10.1038/nenergy.2017.112 Planning of distributed energy resources requires careful consideration of many socio-technical factors to ensure that it is optimally built. Jain et al. present a model that incorporates numerous such factors and use it to find cost-effective resources for a sample of 10,000 consumers in California.
High-concentration planar microtracking photovoltaic system exceeding 30% efficiency Nat. Energy Pub Date :
High-concentration planar microtracking photovoltaic system exceeding 30% efficiency Nature Energy, Published online: 17 July 2017; doi:10.1038/nenergy.2017.113 Concentrator photovoltaics achieve high efficiency but have so far been impractical for use on rooftops. Here, Price et al. develop a flat-panel concentrating photovoltaic system based on a triple-junction solar cell that operates at fixed tilt over a full day with >30% peak efficiency.
Better energy indicators for sustainable development Nat. Energy Pub Date :
Better energy indicators for sustainable development Nature Energy, Published online: 17 July 2017; doi:10.1038/nenergy.2017.117 The UN Sustainable Development Goal 7 aims to deliver affordable, reliable, sustainable and modern energy for all. Tracking progress towards the targets under this goal can spur better energy statistics and data gathering capacity, and will require new indicators that also consider the interplay with other goals.
Hydrogen storage: Pressure swing Nat. Energy Pub Date : 2017-07-11 James Gallagher
Hydrogen storage: Pressure swing Nature Energy, Published online: 11 July 2017; doi:10.1038/nenergy.2017.122
Community energy: Bottom-up justice Nat. Energy Pub Date : 2017-07-11 Nicky Dean
Community energy: Bottom-up justice Nature Energy, Published online: 11 July 2017; doi:10.1038/nenergy.2017.123
Reading through breakthroughs Nat. Energy Pub Date : 2017-07-11
Reading through breakthroughs Nature Energy, Published online: 11 July 2017; doi:10.1038/nenergy.2017.126 The development of rechargeable batteries looks hugely successful on paper, but moving in leaps takes fundamental breakthroughs, truly meaningful performance advances, and technological integration.
Perovskite solar cells: Stability lies at interfaces Nat. Energy Pub Date : 2017-07-11 Mónica Lira-Cantú
Perovskite solar cells: Stability lies at interfaces Nature Energy, Published online: 11 July 2017; doi:10.1038/nenergy.2017.115 Perovskite solar cells are developing fast but their lifetimes must be extended. Now, large-area printed perovskite solar modules have been shown to be stable for more than 10,000 hours under continuous illumination.
Energy policy: Explaining change in the US Nat. Energy Pub Date : 2017-07-11 Alessandro Rubino
Energy policy: Explaining change in the US Nature Energy, Published online: 11 July 2017; doi:10.1038/nenergy.2017.120
Solar energy: Hotspots in Tanzania Nat. Energy Pub Date : 2017-07-11 Elsa Couderc
Solar energy: Hotspots in Tanzania Nature Energy, Published online: 11 July 2017; doi:10.1038/nenergy.2017.121
Ultra-high-rate pseudocapacitive energy storage in two-dimensional transition metal carbides Nat. Energy Pub Date : 2017-07-10 Maria R. Lukatskaya, Sankalp Kota, Zifeng Lin, Meng-Qiang Zhao, Netanel Shpigel, Mikhael D. Levi, Joseph Halim, Pierre-Louis Taberna, Michel W. Barsoum, Patrice Simon, Yury Gogotsi
The use of fast surface redox storage (pseudocapacitive) mechanisms can enable devices that store much more energy than electrical double-layer capacitors (EDLCs) and, unlike batteries, can do so quite rapidly. Yet, few pseudocapacitive transition metal oxides can provide a high power capability due to their low intrinsic electronic and ionic conductivity. Here we demonstrate that two-dimensional transition metal carbides (MXenes) can operate at rates exceeding those of conventional EDLCs, but still provide higher volumetric and areal capacitance than carbon, electrically conducting polymers or transition metal oxides. We applied two distinct designs for MXene electrode architectures with improved ion accessibility to redox-active sites. A macroporous Ti3C2Tx MXene film delivered up to 210 F g−1 at scan rates of 10 V s−1, surpassing the best carbon supercapacitors known. In contrast, we show that MXene hydrogels are able to deliver volumetric capacitance of ∼1,500 F cm−3 reaching the previously unmatched volumetric performance of RuO2.
The future cost of electrical energy storage based on experience rates Nat. Energy Pub Date : 2017-07-10 O. Schmidt, A. Hawkes, A. Gambhir, I. Staffell
Electrical energy storage could play a pivotal role in future low-carbon electricity systems, balancing inflexible or intermittent supply with demand. Cost projections are important for understanding this role, but data are scarce and uncertain. Here, we construct experience curves to project future prices for 11 electrical energy storage technologies. We find that, regardless of technology, capital costs are on a trajectory towards US$340 ± 60 kWh−1 for installed stationary systems and US$175 ± 25 kWh−1 for battery packs once 1 TWh of capacity is installed for each technology. Bottom-up assessment of material and production costs indicates this price range is not infeasible. Cumulative investments of US$175–510 billion would be needed for any technology to reach 1 TWh deployment, which could be achieved by 2027–2040 based on market growth projections. Finally, we explore how the derived rates of future cost reduction influence when storage becomes economically competitive in transport and residential applications. Thus, our experience-curve data set removes a barrier for further study by industry, policymakers and academics.
Defect passivation in hybrid perovskite solar cells using quaternary ammonium halide anions and cations Nat. Energy Pub Date : 2017-06-26 Xiaopeng Zheng, Bo Chen, Jun Dai, Yanjun Fang, Yang Bai, Yuze Lin, Haotong Wei, Xiao Cheng Zeng, Jinsong Huang
The ionic defects at the surfaces and grain boundaries of organic–inorganic halide perovskite films are detrimental to both the efficiency and stability of perovskite solar cells. Here, we show that quaternary ammonium halides can effectively passivate ionic defects in several different types of hybrid perovskite with their negative- and positive-charged components. The efficient defect passivation reduces the charge trap density and elongates the carrier recombination lifetime, which is supported by density-function-theory calculation. The defect passivation reduces the open-circuit-voltage deficit of the p–i–n-structured device to 0.39 V, and boosts the efficiency to a certified value of 20.59 ± 0.45%. Moreover, the defect healing also significantly enhances the stability of films in ambient conditions. Our findings provide an avenue for defect passivation to further improve both the efficiency and stability of solar cells.
I'm not surprised Nat. Energy Pub Date : 2017-06-09
I'm not surprised Nature Energy, Published online: 9 June 2017; doi:10.1038/nenergy.2017.101 It is easy to conflate what is known based on the scientific literature and what feels known because it is intuitive. However, empirical validation and precision are particularly critical for policy-relevant behavioural research, regardless of whether the results are surprising.
Public engagement: Trust and scepticism Nat. Energy Pub Date : 2017-06-09 Jenn Richler
Public engagement: Trust and scepticism Nature Energy, Published online: 9 June 2017; doi:10.1038/nenergy.2017.100
Battery vehicles: Unfriendly production Nat. Energy Pub Date : 2017-06-09 Changjun Zhang
Battery vehicles: Unfriendly production Nature Energy, Published online: 9 June 2017; doi:10.1038/nenergy.2017.99
Burning lithium in CS2 for high-performing compact Li2 S–graphene nanocapsules for Li–S batteries Nat. Energy Pub Date : 2017-06-12 Guoqiang Tan, Rui Xu, Zhenyu Xing, Yifei Yuan, Jun Lu, Jianguo Wen, Cong Liu, Lu Ma, Chun Zhan, Qi Liu, Tianpin Wu, Zelang Jian, Reza Shahbazian-Yassar, Yang Ren, Dean J. Miller, Larry A. Curtiss, Xiulei Ji, Khalil Amine
Tremendous efforts have been made to design the cathode of Li–S batteries to improve their energy density and cycling life. However, challenges remain in achieving fast electronic and ionic transport while accommodating the significant cathode volumetric change, especially for the cathode with a high practical mass loading. Here we report a cathode architecture, which is constructed by burning lithium foils in a CS2 vapour. The obtained structure features crystalline Li2S nanoparticles wrapped by few-layer graphene (Li2S@graphene nanocapsules). Because of the improvement on the volumetric efficiency for accommodating sulfur active species and electrical properties, the cathode design enables promising electrochemical performance. More notably, at a loading of 10 mgLi2S cm−2, the electrode exhibits a high reversible capacity of 1,160 mAh g−1s, namely, an area capacity of 8.1 mAh cm−2. Li2S@graphene cathode demonstrates a great potential for Li-ion batteries, where the Li2S@graphene-cathode//graphite-anode cell displays a high capacity of 730 mAh g−1s as well as stable cycle performance.
Empirically observed learning rates for concentrating solar power and their responses to regime change Nat. Energy Pub Date : 2017-06-12 Johan Lilliestam, Mercè Labordena, Anthony Patt, Stefan Pfenninger
Concentrating solar power (CSP) capacity has expanded slower than other renewable technologies and its costs are still high. Until now, there have been too few CSP projects to derive robust conclusions about its cost development. Here we present an empirical study of the cost development of all operating CSP stations and those under construction, examining the roles of capacity growth, industry continuity, and policy support design. We identify distinct CSP expansion phases, each characterized by different cost pressure in the policy regime and different industry continuity. In 2008–2011, with low cost pressure and following industry discontinuity, costs increased. In the current phase, with high cost pressure and continuous industry development, costs decreased rapidly, with learning rates exceeding 20%. Data for projects under construction suggest that this trend is continuing and accelerating. If support policies and industrial structure are sustained, we see no near-term factors that would hinder further cost decreases.
Two-dimensional heterostructures for energy storage Nat. Energy Pub Date : 2017-06-12 Ekaterina Pomerantseva, Yury Gogotsi
Two-dimensional (2D) materials provide slit-shaped ion diffusion channels that enable fast movement of lithium and other ions. However, electronic conductivity, the number of intercalation sites, and stability during extended cycling are also crucial for building high-performance energy storage devices. While individual 2D materials, such as graphene, show some of the required properties, none of them can offer all properties needed to maximize energy density, power density, and cycle life. Here we argue that stacking different 2D materials into heterostructured architectures opens an opportunity to construct electrodes that would combine the advantages of the individual building blocks while eliminating the associated shortcomings. We discuss characteristics of common 2D materials and provide examples of 2D heterostructured electrodes that showed new phenomena leading to superior electrochemical performance. We also consider electrode fabrication approaches and finally outline future steps to create 2D heterostructured electrodes that could greatly expand current energy storage technologies.
Concentrating solar power: Still small but learning fast Nat. Energy Pub Date : 2017-06-12 Robert Pitz-Paal
Concentrating solar power: Still small but learning fast Nature Energy, Published online: 12 June 2017; doi:10.1038/nenergy.2017.95 Concentrating solar power had a difficult market start compared to other renewable technologies, leading to a total global capacity of only 5 GW today after more than a decade of deployment. A comprehensive global empirical study identifies distinct deployment phases, with high learning rates exceeding 25% over the past 5 years.
Li–S batteries: Firing for compactness Nat. Energy Pub Date : 2017-06-12 Yanguang Li, Fengjiao Chen
Li–S batteries: Firing for compactness Nature Energy, Published online: 12 June 2017; doi:10.1038/nenergy.2017.96 Conventional Li–S batteries have a non-compact cathode structure containing low areal loading of active materials. Now, a strategy of burning Li foils in a CS2 vapour is presented, which leads to the formation of highly compact Li2S nanoparticles as a lithiated sulfur cathode, offering promising battery performance.
Microbial fuel cells: Running on gas Nat. Energy Pub Date : 2017-06-09 Zhiyong Jason Ren
Microbial fuel cells: Running on gas Nature Energy, Published online: 9 June 2017; doi:10.1038/nenergy.2017.93 Methane is an abundant energy source that is used for power generation in thermal power plants via combustion, but direct conversion to electricity in fuel cells remains challenging. Now, a microbial fuel cell is demonstrated to efficiently convert methane directly to current by careful selection of a consortium of microorganisms.
Energy efficiency: Governance in the EU Nat. Energy Pub Date : 2017-06-09 Alessandro Rubino
Energy efficiency: Governance in the EU Nature Energy, Published online: 9 June 2017; doi:10.1038/nenergy.2017.97
Offshore wind: Decommissioning plans Nat. Energy Pub Date : 2017-06-09 Elsa Couderc
Offshore wind: Decommissioning plans Nature Energy, Published online: 9 June 2017; doi:10.1038/nenergy.2017.98
True performance metrics in beyond-intercalation batteries Nat. Energy Pub Date : 2017-06-05 Stefan A. Freunberger
True performance metrics in beyond-intercalation batteries Nature Energy, Published online: 5 June 2017; doi:10.1038/nenergy.2017.91 Beyond-intercalation batteries promise a step-change in energy storage compared to intercalation-based lithium-ion and sodium-ion batteries. However, only performance metrics that include all cell components and operation parameters can tell whether a true advance over intercalation batteries has been achieved.
Enhanced selectivity in mixed matrix membranes for CO2 capture through efficient dispersion of amine-functionalized MOF nanoparticles Nat. Energy Pub Date : 2017-06-05 Behnam Ghalei, Kento Sakurai, Yosuke Kinoshita, Kazuki Wakimoto, Ali Pournaghshband Isfahani, Qilei Song, Kazuki Doitomi, Shuhei Furukawa, Hajime Hirao, Hiromu Kusuda, Susumu Kitagawa, Easan Sivaniah
Mixed matrix membranes (MMMs) for gas separation applications have enhanced selectivity when compared with the pure polymer matrix, but are commonly reported with low intrinsic permeability, which has major cost implications for implementation of membrane technologies in large-scale carbon capture projects. High-permeability polymers rarely generate sufficient selectivity for energy-efficient CO2 capture. Here we report substantial selectivity enhancements within high-permeability polymers as a result of the efficient dispersion of amine-functionalized, nanosized metal–organic framework (MOF) additives. The enhancement effects under optimal mixing conditions occur with minimal loss in overall permeability. Nanosizing of the MOF enhances its dispersion within the polymer matrix to minimize non-selective microvoid formation around the particles. Amination of such MOFs increases their interaction with thepolymer matrix, resulting in a measured rigidification and enhanced selectivity of the overall composite. The optimal MOF MMM performance was verified in three different polymer systems, and also over pressure and temperature ranges suitable for carbon capture.
Making Li-metal electrodes rechargeable by controlling the dendrite growth direction Nat. Energy Pub Date : 2017-06-05 Yadong Liu, Qi Liu, Le Xin, Yuzi Liu, Fan Yang, Eric A. Stach, Jian Xie
The long-standing issue of Li-dendrite formation and growth during repeated plating or stripping processes prevents the practical application of Li-metal anodes for high-specific-energy batteries. Here we develop an approach to control dendrite growth by coating the separator with functionalized nanocarbon (FNC) with immobilized Li ions. During cycling, the Li dendrites grow toward each other simultaneously from both the FNC layer on the separator and the Li-metal anode; when the dendrites meet, the growth changes direction: rather than penetrating the separator, a dense Li layer is formed between the separator and the Li anode. This controlled growth alleviates the solid electrolyte interphase formation, reduces the decomposition of the electrolyte, and improves the cyclability of the Li-metal cell. In a Li/LiFePO4 coin cell with three different electrolytes, we show that this approach enables a long stable cycle life (>800 cycles with 80% retention of the initial capacity) and improved efficiency (>97%). Our method offers promise for application in practical Li-metal batteries, and it may also be useful for tackling dendrite issues for other metals.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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