New-generation Energy Research Articles

Monitoring Approaches for New-Generation Energy Performance Certificates in Residential Buildings

In 2002, the Energy Performance of Building Directive (EPBD) introduced energy certification schemes to classify and compare building performances to support reaching energy efficiency targets by informing the different actors of the building sectors. However, since its implementation, the Energy Performance Certifications (EPCs) remained unexploited with limited impact on the energy savings targets. In this context, the EPC RECAST project aims at studying a new generation of EPCs with a focus on the residential sector. More in detail, the paper presents and frames a monitoring approach based on low-cost and non-invasive technology for real data collection in existing residential apartments/houses. The method is based on different levels of monitoring selected according to the typology of the building (e.g., detached house, apartment), services (e.g., centralized or local energy generation), and energy vectors (e.g., natural gas or electricity). Three different levels have been identified (named as: basic, medium, and advanced) and for each one, different plug and play monitoring sensor kits have been selected. Six representative pilot buildings have been identified and selected to verify the approach in general and, in particular, the sensors’ applicability and communication, the data reliability, and the monitoring platform. The presented work highlights, on the one hand, the general feasibility of the proposed monitoring approach; on the other, it highlights the difficulty of fully standardizing the sensors kits considering that each building/apartment has specific characteristics and constraints that have to be carefully analyzed. The use of the ultrasonic flow meters represents a good technical option for reducing the cost and the impact on the existing plant system; however, their installation must be verified considering that the logger needs to be powered and the sensors calibrated for collecting reliable data.

Excimer ultraviolet-irradiated graphene separator for suppressing polysulfide shuttling in Li–S batteries

Lithium–sulfur (Li–S) batteries are expected to become efficient new-generation energy storage systems owing to their properties such as high theoretical specific capacity (1675 mAh g−1) and high energy density (2600 Wh kg−1). However, some factors restrict their rapid development; for example, the dissolution and migration of polysulfides during the charge and discharge process, extremely poor conductivity of sulfur, and increase in volume. A glass fiber separator with graphene was loaded on a surface modified by excimer ultraviolet light (EUV/graphene separator) as the separator for Li–S batteries. The modified separator was irradiated by excimer ultraviolet light with graphene powder loaded on a glass fiber via vacuum filtration; this can effectively block polysulfide diffusion and improve the utilization rate of active materials when assembled into a Li–S battery. The first discharge specific capacity for this separator was as high as 1164 mAh g−1 at 0.2 C; after 300 cycles, the specific capacity was maintained at 640.5 mAh g−1. This modified separator guarantees the efficient migration of lithium ions and effectively inhibits the shuttle effect of Li–S batteries.

Towards Green Economics and Society: Exploring the Efficiency of New Energy Generation

In recent years, solar and wind energy have been increasingly abandoned due to the blind expansion of the new energy industry. Due to the competitive relationships between different types of new energy, reasonable industrial development planning needs to be implemented to not only save the cost of government subsidies but also clarify the investment direction of social capital. Based on the panel data of OECD countries between 2006 and 2018, the stochastic frontier analysis (SFA) was used to measure the efficiency of new energy generation (NEG) and the influencing factors were analyzed in this paper. Results were as follows: the efficiency of NEG in OECD countries is improving; the efficiency of NEG is positively correlated with technical innovation, government policies, economic level, and education level and negatively correlated with urbanization. Based on the empirical results of this study, problems in the development of the new energy industry have been discussed and suggestions to improve the efficiency of NEG have been proposed.

Ultrathin Ni(OH)2 layer coupling with graphene for fast electron/ion transport in supercapacitor

Integration of fast electrochemical double-layer capacitance and large pseudocapacitance is a practical way to improve the overall capability of supercapacitor, yet remains challenging. Herein, an effective cyanogel synthetic strategy was demonstrated to prepare ultrathin Ni(OH)2 nanosheets coupling with conductive reduced graphene oxide (rGO) (rGO-Ni(OH)2) at ambient condition. Ultrathin Ni(OH)2 nanosheet with 3–4 layers of edge-sharing octahedral MO6 maximally exposes the active surface of Faradic reaction and promotes the ion diffusion, while the conductive rGO sheet boosts the electron transport during the reaction. Even at 30 A g−1, the optimal sample can deliver a specific capacitance of 1119.52 F g−1, and maintain 82.3% after 2000 cycles, demonstrating much higher electrochemical capability than bare Ni(OH)2 nanosheets. A maximum specific energy of 44.3 W h kg−1 (148.5 W kg−1) is obtained, when assembled in a two-electrode system rGO-Ni(OH)2//rGO. This study provides an insight into efficient construction of two-dimensional hybrid electrodes with high performance for the new-generation energy storage system.

Spherical-graphite/nano-Mn2O3 composites as advanced anode materials for lithium half/full batteries

The spherical-graphite/Mn2O3 composites (SG/Mn2O3) with a core-shell structure have been facilely synthesized by the initial coprecipitation method and subsequent calcination treatment. As-synthesized composites as anode materials demonstrate remarkable lithium storage performances. The optimal SG/Mn2O3 with 17.6 wt% of Mn2O3 nanoparticles manifests the charge capacity of 499 mA h g−1 over 100 cycles at 0.5 A g−1, and presents the reversible capacity of 383 mA h g−1 under 2 A g−1 after 1000 long cycles for lithium-ion half batteries. When the optimal SG/Mn2O3 electrode is assembled to full-cell using LiFePO4 as the cathode, the full-cell affords the discharge capacity of 318 mA h g−1 with capacity retention of 97.2% at 0.1 A g−1 over 30 cycles. The high capacity of Mn2O3 nanoparticles coating on the surface/interface of SG enhances the long-periodic cycling properties and rate performance of overall electrode. The superior lithium storage performance demonstrates that the SG/Mn2O3 has great potential in the new-generation energy storage devices.

CuCo2O4 nanoneedle array with high stability for high performance asymmetric supercapacitors.

Cycling performance is very important to device application. Herein, a facile and controllable approach is proposed to synthesize high stability CuCo2O4 nanoneedle array on a conductive substrate. The electrode presents excellent performances in a large specific capacitance up to 2.62 F cm−2 (1747 F g−1) at 1 mV s−1 and remarkable electrochemical stability, retaining 164% even over 70 000 cycles. In addition, the asymmetric supercapacitor assembled with the optimized CuCo2O4 nanoneedle array (cathode) and active carbon (anode), which exhibits superior specific capacity (146 F g−1), energy density (57 W h kg−1), and cycling stability (retention of 83.9% after 10 000 cycles). These outstanding performances are mainly ascribed to the ordered binder-free nanoneedle array architecture and holds great potential for the new-generation energy storage devices.

Oxygen vacancies modulation in graphene/MnOx composite for high performance supercapacitors

An efficient and scalable method to improve the capacitive properties of MnO2 is reported by inducing graphene (rGO) and oxygen vacancies via a thermal treatment in air, in which graphene oxide (GO) is in situ reduced and graphene/MnOx (rGO/MnOx) composite without oxygen vacancies-induced phase transformation is formed. RGO/MnOx composite exhibits a large specific capacitance (274 F g−1 at 0.5 A g−1), excellent cycling stability (98.8% after 5000 cycles at 1 A g−1) and rate performance (171 F g−1 at 10 A g−1). The performance improvement of rGO/MnOx sample is mainly attributed to the moderate concentration of oxygen vacancies, rGO and special 3D porous architecture, which facilitate the rapid ionic and electronic transport and promote a facile redox reaction and surface double-layer capacitance. The asymmetric supercapacitor composed of rGO/MnOx//Kochen Black (KB) also shows an outstanding cyclic stability (89% after 5000 cycles) in all-solid-state asymmetric supercapacitor. The design and synthesis method of rGO/MnOx sample offers a promising approach to broaden MnO2-based electrode materials for a new-generation energy storage device.

High capacity semi-liquid lithium sulfur cells with enhanced reversibility for application in new-generation energy storage systems

Semi-liquid configuration of sulfur cell is proposed as simple strategy to develop high-energy lithium battery. Two solutions of Li2S8 in diethylene glycol dimethyl ether (DEGDME), containing either lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) or lithium trifluoromethansulfonate (LiCF3SO3) and lithium nitrate (LiNO3), are studied as catholytes for Li/S cells exploiting the polysulfides electrochemical reaction at about 2.2 V vs. Li+/Li. X-ray photoelectron spectroscopy (XPS) and thermal analyses, respectively, reveal composition and high-temperature stability of the catholyte solutions. Ad hoc study conducted by impedance spectroscopy, voltammetry, and galvanostatic techniques suggests well suitable characteristics in terms of Li+-transport ability, electrochemical stability window, and electrode/electrolyte interphase features. Cells with sulfur loading ranging from about 3 to 6 mg cm−2 into the solution are successfully studied with remarkable performances in terms of current rates, efficiency and cycle life. Hence, the lithium cells based on the catholyte deliver maximum capacity of the order of 1100 mAh gS−1 at C/10 rate and stable capacity of about 800 mAh gS−1 at C/3 rate with Coulombic efficiency exceeding 99%. Therefore, the catholyte solutions studied herein are considered as a very promising candidates for high-energy storage in next generation systems, such as the intriguing hybrid and electric vehicles.

Research on the new-generation urban energy system in China

Energy is the blood of modern society and energy system plays an increasingly important role in urban development, especially in the background of a new round of energy reform. The construction of a new-generation of urban energy systems is becoming an important breakthrough to solve the bottleneck of urban development and to improve the quality of urban development in the future. From the perspective of the relationship between energy and cities, this paper analyzes the current situation and existing problems of urban energy system. Taking the research of energy system in Xiong’an New District as an opportunity, this paper explores the operation structure and implementation path of the new-generation urban energy system in Xiong’an New District. In this paper, it is considered that the new-generation energy system in Xiong’an New District will be electricity-centered, smart grid as the platform, energy transregional transmission combined with local development, optimal scheduling among multiple energy categories, and "source-grid-load-storage" high-efficiency interaction as well as the unified open market. The proposal of the new generation of urban energy system cannot only point out the direction for the planning and construction of the energy system in Xiong’an New District, but also help to solve the general problems in the urban energy system and promote the trend of energy transformation.

Effective Activation and Stabilization of Si Negative Electrode By Li Pre-Doping Method for Next-Generation Batterie

In recent years, new-generation energy storage systems such as Li-S and Li-O2 batteries have attracted increasing attention because of the high energy densities over 500 Wh kg-1[1]. The high energy storage systems do not basically have Li+ ion in the positive electrodes and need Li metal negative electrode (NE), whose theoretical capacity is ca. 3860 mAh g-1. However, Li metal NE has a risk of short circuit by Li dendrite growth and the poor rate capability by the small surface area due to the flat morphology, i.e. foil or thin film. On the contrary, Si is one of the good candidates for the NEs because of the high theoretical capacity of ca. 4200 mAh g(Si)-1, and the suppression of Li dendrite growth by the Li alloying/de-alloying reactions. In addition, morphology of Si active materials, e.g. nanoparticles, nano-wires, nano-flakes, not only suppresses the capacity fading due to the crack and pulverization but also enhances the rate capability of Si NEs by increasing the surface area. However, for applying the Si NEs to next-generation batteries, it is necessary to Li pre-dope into the Si NEs. Namely, the easier and more convenient Li pre-doping technique must be developed for the practical use. In this study, we prepared two types of Li pre-doped Si NEs by direct Li pre-doping (DP) [2] and electrochemical Li charging (EC) methods without and with fluoroethylene carbonate (FEC) as an additive, and investigated the charge/discharge properties by a half-cell operation at limiting capacity of 2000 mAh g (Si)-1. The morphology and crystalline phase changes were investigated by a SEM, SPM and XRD analyses. The electrochemical properties also evaluated by constant current charge/discharge test and cyclic voltammetry by using Li pre-doped Si NE | 1.0 M LiPF6/ EC+DMC(1:1 by vol.) | Li metal half-cells at 30oC. To investigate the morphology change of Si nanoparaticles, SPM images of the Li pre-doped Si NEs were compared (Fig. 1). In the case of EC method, volume expansion of Si nanoparticles by Li pre-doping was clearly confirmed. Especially by the FEC addition, the volume expansion was more promoted, indicating deeper Li pre-doping. In contrast, Si nanoparticles treated by the DP method rather became smaller than the pristine one. This implies that the Si nanoparticles were cracked and pulverizated by the mechanical stress due to rapid Li alloying. Namely, the cracking is considered to shorten the Li+ diffusion distance to accelerate the Li pre-doping. In fact, XRD analysis exhibited much larger amount of Li15Si4, i.e. more Li-rich alloying state than Li x Si y amorphous phase, for the DP treated Si NEs, and the degree of Li alloying was enhanced by the FEC addition. Fig. 2 shows the cyclic voltammograms (CVs) for the Li pre-doped Si NEs between 1.5 and 0.02 V vs. Li/Li+. For EC treated Si NEs, two current peaks were observed for both charging at 0.20 and 0.10 V and discharging at 0.35 and 0.50 V, indicating Li alloying/de-alloying during the amorphous Si phase. Also, the charge/discharge capacities increased after adding FEC. In contrast, for DP treated Si NEs exhibited only one sharp current peak at 0.53 V during 1st cycle, meaning Li de-alloying from Li15Si4 crystalline phase. After that, the oxidation current due to electrolyte decomposition was continuously observed and relatively suppressed by the FEC addition. This indicates that the SEI film derived from FEC additive were more stable and tough against the large volume change by the phase transition between the Li15Si4 crystalline and Li x Si y amorphous phases. The charge/discharge capacities estimated from CVs at 3rd cycle was summarized in Table 1. The specific capacities were enhanced by the DP method and FEC addition. Therefore, the combination was found to be quite effective to improve the bulk activation and interphase stabilization of Si NE. The effect mechanism in more detail will be discussed in the meeting. This study was partially supported by NEDO Project “RISING2”, Japan. [1] P. G. Bruce et al., Nature materials, 11, 19 (2012). [2] M. Saito et al., Electrochemistry, 85(10), 656 (2017). Figure 1

Self-Assembled Biomolecular 1D Nanostructures for Aqueous Sodium-Ion Battery.

Aqueous sodium‐ion battery of low cost, inherent safety, and environmental benignity holds substantial promise for new‐generation energy storage applications. However, the narrow potential window of water and the enlarged ionic radius because of hydration restrict the selection of electrode materials used in the aqueous electrolyte. Here, inspired by the efficient redox reaction of biomolecules during cellular energy metabolism, a proof of concept is proposed that the redox‐active biomolecule alizarin can act as a novel electrode material for the aqueous sodium‐ion battery. It is demonstrated that the specific capacity of the self‐assembled alizarin nanowires can reach as high as 233.1 mA h g−1, surpassing the majority of anodes ever utilized in the aqueous sodium‐ion batteries. Paired with biocompatible and biodegradable polypyrrole, this full battery system shows excellent sodium storage ability and flexibility, indicating its potential applications in wearable electronics and biointegrated devices. It is also shown that the electrochemical properties of electrodes can be tailored by manipulating naturally occurring 9,10‐anthroquinones with various substituent groups, which broadens application prospect of biomolecules in aqueous sodium‐ion batteries.

Enhanced durability of a cost-effective perovskite-carbon catalyst for the oxygen evolution and reduction reactions in alkaline environment

The design of a bifunctional air electrode able to carry out both the oxygen reduction and evolution reactions in an alkaline environment is essential for the progress of new-generation energy conversion and storage devices. Alkaline systems allow the use of non-noble metals, which favors a considerable reduction of the system cost. In this work, a cost-effective perovskite, La0.6Sr0.4Fe0.8Co0.2O3, has been investigated as bifunctional catalyst in a 6 M KOH alkaline solution. The perovskite was mixed with an experimental carbon black, characterized by a graphitic structure and a specific surface area of 220 m2 g−1. The perovskite-carbon composite was compared to a Pd/C catalyst (employing the same carbon black as support). Generally, bifunctional catalysts are subjected to high electrochemical potentials, particularly during the oxygen evolution. In order to assess the stability of the bifunctional catalyst, several accelerated degradation tests were performed. Results proved that the perovskite-carbon composite showed good performance for both reactions, in particular for the oxygen evolution. Furthermore, it also presented enhanced stability vs. Pd/C when subjected to degradation tests, maintaining a constant potential over time, even working at high current densities (80 and 125 mA cm−2). This material is envisaged as a very promising bifunctional catalyst, in particular in terms of durability.

Thin and flexible all-solid supercapacitor prepared from novel single wall carbon nanotubes/polyaniline thin films obtained in liquid–liquid interfaces

The present work describes for the first time the synthesis and characterization of single wall carbon nanotubes/polyaniline (SWNTs/PAni) nanocomposite thin films in a liquid–liquid interface, as well as the subsequent construction of a flexible all-solid supercapacitor. Different SWNTs/PAni nanocomposites were prepared by varying the ratio of SWNT to aniline, and the samples were characterized by scanning and transmission electron microscopy, Raman and UV–Vis spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The pseudo-capacitive behavior of the nanocomposites was evaluated by charge/discharge galvanostatic measurements. The presence of the SWNTs affected the electronic and vibrational properties of the polyaniline and also improved the pseudo-capacitive behavior of the conducting polymer. A very thin and flexible all-solid device was manufactured using two electrodes (polyethylene terephthalate-PET covered with the SWNT/PAni nanocomposite separated by a H2SO4-PVA gel electrolyte). The pseudo-capacitive behavior was characterized by a volumetric specific capacitance of approximately 76.7 F cm−3, even under mechanical deformation, indicating that this nanocomposite has considerable potential for application in new-generation energy storage devices.

Anomalous Pseudocapacitive Behavior of a Nanostructured, Mixed-Valent Manganese Oxide Film for Electrical Energy Storage

While pseudocapacitors represent a promising option for electrical energy storage, the performance of the existing ones must be dramatically enhanced to meet today's ever-increasing demands for many emerging applications. Here we report a nanostructured, mixed-valent manganese oxide film that exhibits anomalously high specific capacitance (∼2530 F/g of manganese oxide, measured at 0.61 A/g in a two-electrode configuration with loading of active materials ∼0.16 mg/cm(2)) while maintaining excellent power density and cycling life. The dramatic performance enhancement is attributed to its unique mixed-valence state with porous nanoarchitecture, which may facilitate rapid mass transport and enhance surface double-layer capacitance, while promoting facile redox reactions associated with charge storage by both Mn and O sites, as suggested by in situ X-ray absorption spectroscopy (XAS) and density functional theory calculations. The new charge storage mechanisms (in addition to redox reactions of cations) may offer critical insights to rational design of a new-generation energy storage devices.