Energy Utilization Strategies Research Articles

Cascade reservoirs operation rules derivation using integrated decision-making method and combinatorial evolution network

Implicit reservoir operation rules map known reservoir conditions to discharge flow or water level decisions to guide reservoir operation. Existing data-driven operation rule extraction models are influenced by both features and hyperparameters, and lack subjective-objective coordination, hindering the formulation of reasonable water energy utilization strategies. To improve the comprehensive benefits of cascade reservoirs, this study proposes a novel multi-objective cascade reservoir operation rule derivation framework. First, a multi-objective optimal operation model for cascade reservoirs (MOOMCR) considering power generation, environment, and navigation is constructed and solved using a Speed-constrained Multi-objective Particle Swarm Optimization algorithm (SMPSO). The relationships among the requirements were explained using a four-dimensional Pareto front visualization analysis. Then, an Integrated Decision-making Method based on Multilevel Subspace Domination (IDMSD) is proposed to circumvent the subjective defects of single decision-making models and reliably select the optimal scheme with the most significant comprehensive benefits from all typical years. Finally, a feature-hyperparameter combination optimization technique based on the differential evolutionary algorithm (FHCC-DE/best/1) is proposed, which exhibits its strength in the identification of key influencing factors on the optimal discharge flow from the IDMSD. The method was embedded in a deep learning model to construct a Combinatorial Evolution Network (CEN) to extract the implicit reservoir operation rules from the optimal IDMSD schemes for the MOOMCR. The results show that the RMSE of the CEN simulating the optimal discharge flow is improved by 5.98%, 28.03%, and 27.89% for the XLD reservoir and by 11.01%, 1.66%, and 60.98% for the XJB reservoir, respectively, over the best results of all benchmark models. Meanwhile, the operation simulation results confirmed that the CEN outperforms conventional reservoir scheduling, with advanced multi-objective comprehensive effects. This suggests that multimethod integrated decision-making and deep learning evolution optimization can help improve the accuracy, generalization, and reliability of implicit reservoir operation rules.

A State-of-the-Art Review on Geothermal Energy Extraction, Utilization, and Improvement Strategies: Conventional, Hybridized, and Enhanced Geothermal Systems

A State-of-the-Art Review on Geothermal Energy Extraction, Utilization, and Improvement Strategies: Conventional, Hybridized, and Enhanced Geothermal Systems

Utilization of Cold Energy from LNG Regasification Process: A Review of Current Trends

Liquified natural gas (LNG) is a clean primary energy source that is growing in popularity due to the distance between natural gas (NG)-producing countries and importing countries. The large amount of cold energy stored in LNG presents an opportunity for sustainable technologies to recover and utilize this energy. This can enhance the energy efficiency of LNG regasification terminals and the economic viability of the LNG supply chain. The energy stored in LNG in the form of low temperatures is referred to as cold energy. When LNG is regasified, or converted back into its gaseous form, this cold energy is released. This process involves heating the LNG, which causes it to vaporize and release its stored energy. The current state-of-the-art techniques for LNG cold energy utilization, including power generation, air separation, traditional desalination, and cryogenics carbon dioxide (CO2) capture are discussed in this review. While most of the current LNG cold energy utilization systems are presented, potential future applications are also discussed. The commercialization of sustainable technologies, such as improvement strategies for LNG cold energy utilization, is becoming increasingly important in the energy industry.

Divergent Energy-Climate Nexus in the Global Fuel Combustion Processes.

Fuel combustion provides basic energy for the society but also produces CO2 and incomplete combustion products that threaten human survival, climate change, and global sustainability. A variety of fuels burned in different facilities expectedly have distinct impacts on climate, which remains to be quantitatively assessed. This study uses updated emission inventories and an earth system model to evaluate absolute and relative contributions in combustion emission-associated climate forcing by fuels, sectors, and regions. We showed that, from 1970 to 2014, coal burned in the energy sector and oil used in the transportation sector contributed comparable energies consumed (24 and 20% of the total) but had distinct climate forcing (1 and 40%, respectively). Globally, coal burned for energy production had negative impacts on climate forcing but positive effects in the residential sector. In many developing countries, coal combustion in the energy sector had negative radiative forcing (RF) per unit energy consumed due to insufficient controls on sulfur and scattering aerosol levels, but oils in the transportation sector had high positive RF values. These results had important implications on the energy transition and emission reduction actions in response to climate change. Distinct climate efficiencies of energies and the spatial heterogeneity implied differentiated energy utilization strategies and pollution control policies by region and sector.

English

This paper reviews biomass energy production and utilization trends, opportunities, challenges and strategies for sustainability in biomass energy sector in sub-Saharan Africa (SSA).  This is because despite various benefits provided by the resource, it receives little attention in terms of policy formulation and planning to enhance adequate investments and allocation of funds. Therefore, with increasing demand rate of 3.3% over 27% of woodfuel in SSA will continue being produced unsustainably using inefficient technologies; leading to a deforestation and degradation rate of over 3.5 million ha per year. The situation is worse in some countries like Kenya where over 40% of biomass energy especially is obtained from arid and semi-arid lands (ASALs) characterized by less than 4% productivity rate due to poor regeneration and vegetation growth rates.  Thus there is need to implement various strategies including adoption of improved and efficient production and utilization technologies, increase on-farm tree planting and enhanced tree out-grower systems, enactment and proper implementation of biomass energy policies, establishment of reliable biomass energy database, and recognition of biomass energy benefits to the society. These will foster integration of biomass energy into planning programmes to enhance investments in the sector and reduce biomass energy resource overexploitation. Key words: Biomass energy, sustainability, policy, technologies, deforestation, degradation.

Optimal scheduling of residential houses with optimal photovoltaic energy utilization strategy using improved multi-objective equilibrium optimizer algorithm

In the background of strongly practicing the “double carbon” strategy, the use of solar photovoltaic (PV) energy in residential houses is an effective way to achieve energy saving and emission reduction. In this paper, a multi-objective optimal scheduling model for residential houses is established, and it takes electricity cost, demand response (DR) curtailment value and carbon emission as the optimization objectives. Then, a novel operation strategy, which is called optimal PV energy utilization strategy, is proposed to further reduce electricity cost and carbon emission, by properly managing the power flow. For the multi-objective optimal scheduling problem with multi-decision variables and nonlinearity, an improved multi-objective equilibrium optimizer (IMOEO) algorithm is proposed to obtain the Pareto front solutions. The algorithm uses constrained non-dominant mechanism to deal with the constraint problems of the model, as well as the hybrid opposite learning strategy and the spiral operator are used to improve the overall performance of the algorithm. Finally, the optimal compromise solution is obtained by using the technique for order preference by similarity to ideal solution (TOPSIS). The experimental results indicate that IMOEO algorithm has better performance in terms of convergence and diversity. What's more, compared with the original strategy, the optimal compromise solution obtained by the proposed strategy reduces 28.76%, 9.78% and 15.36% for these optimization objectives, respectively. Therefore, the proposed method is beneficial to achieve low-carbon electricity consumption in residential houses.

Reduction of charge carrier recombination by Ce gradient doping and surface polarization for solar water splitting

Photoelectrochemical (PEC) water splitting is one of the most strategies for solar energy storage and utilization. Hematite as one of the promising candidates for PEC research, has a short hole diffusion length and short carrier lifetime, resulting in PEC conversion efficiency far below the theoretical value. In this work, a facile but efficient strategy was introduced for the growth of gradient Ce doped hematite nanorods, following with the sequent photoactivation process. The gradient Ce doping not only increased the conductivity of bulk material, but also importantly, constructed a built-in electric field by the addition of Ce element, which remarkably enhanced the charge separation and transfer from the bulk to the surface. Moreover, the surface polarization under illumination was applied for the reduction of overpotential and the enhancement of photocurrent density, taking a role of cocatalyst decoration. It reduced the oxygen vacancies concentration at the surface, which further reduced the surface recombination owing to the passivation from photoactivation. According to these, the resulting photoanode exhibited a photocurrent of 1.92 and 2.50 mA cm−2 at 1.23 and 1.50 VRHE, respectively, with onset potential of 0.64 VRHE under AM 1.5G illumination. This work opens a useful strategy of modifying the electronic structure and constructing the interface structure for improving PEC performance on hematite-based photoelectrodes for solar energy storage and utilization.

Coal Mining Energy Utilization and Environmental Impact Management Strategy Using the LCA Method

Coal mining processing and the clearing of land require that materials which have been removed be carefully inspected before it is reused. In this study, the boundary of our model starts with excavation and ends with material recovery. Therefore, further processing of the material to be recovered (recycling, reprocessing) is excluded from the model. In this study, the topsoil layer was collected in three pits numbered one, two, and three, from January to December 2020. The use of the LCA method gives results after the inventory data is carried out, which results in global warming. The results showed material removal unit process generated a total CO2 value of 32.44 kg CO2- eq.tonne-1 of coal, and the coal mining unit process generated a total CO2 value of 255.99 kg CO2- eq.tonne-1 of coal, for the impact of global warming. When compared to the material removal process, the results of the coal mining unit process show the highest global warming impact. Coal processing gives a yield of 25.61 kg CO2- eq.tonne-1 of coal. So that the resulting impact as a whole is 314 kg CO2- eq.tonne-1 of coal. The total emissions resulting from B30 fuel (314 kg CO2- eq.tonne-1 of coal) are smaller than B20 fuel (320 kg CO2- eq.tonne-1 of coal), 6 kg CO2-eq.tonne-1 of coal. The coal mining process includes fuel used in coal extraction, coal hauling, coal stockpiling, blasting, water pumps, and water tracks.

Collaborative optimization for a multi-energy system considering carbon capture system and power to gas technology

Decarbonization of the power system is a crucial way to mitigate global warming. Carbon capture and renewable energy utilization are constructive solutions to realize decarbonization from the perspective of emission and generation, respectively. Considering the co-existence of a high proportion of coal-fired power plants and large-scale renewable energy in China, this paper couples the carbon capture system (CCS) and power to gas (P2G) technology to establish the relationship between the carbon reduction and the renewable energy utilization strategies, and proposes a collaborative optimization of planning and operation for a multi-energy system considering the two technologies. Compared with the baseline case, simulation results show that the proposed model achieves positive effects on carbon mitigation and renewable energy penetration with less cost. This study highlights the significant potential of the coordination of carbon capture systems and the power to gas technology towards deeper decarbonization and carbon tax relief. In addition, we propose some insights on the social acceptance of CCS and P2G from the qualitative perspective to achieve the goal of raising awareness on the successful development of the two technologies in China.

Current Advances of Resource Utilization of Herbal Extraction Residues in China

China is the largest consumer and producer of herbal medicine known as traditional Chinese medicine in the world. After the extraction of medicinal plants’ functional ingredients, large amounts of herbal extracted residues would be manufactured. It is estimated that there are more than 1500 medicinal herb companies in China; the annual yield of Chinese herb extracted residues (CHERs) is up to 35 million tons. However, herbal residues are managed through landfills rather than being considered as renewable lignocellulosic biomass. A review concerning the utilization ways and technologies of CHERs is presented, focusing on energy utilization strategies, including direct combustion, thermochemical and biochemical conversion. Other technologies, such as adsorbents products, composting and fertilizers, biorefinery for bioethanol, bio-based chemicals, and re-extraction of other ingredients are also presented. Based on the technology status and potential, the future research and development of herb residues in biomass energy to develop a low-carbon economy for the traditional Chinese medicine industry are proposed.

Greenhouse Gas Emission Transfer of Inter-Provincial Electricity Trade in China.

Inter-regional electricity trade is an important way to mitigate the imbalance between regional electricity generation and consumption. With the increasing amount of inter-regional electricity trade in China, the emission transfer problem is more severe. By using Quasi-Input-Output model, which can consider the ripple effect of electricity trade network, this study analyzed embodied greenhouse gas emissions of electricity trade among 30 provinces in China. Results indicated that, in 2017, the national transfer volumes of CO2, CH4, and N2O embodied in inter-provincial electricity trade were 603.25 Mt, 6803.81 t, and 9899.25 t, respectively. Emissions are mainly transferred from the eastern to the western regions, especially to those with high proportion of electricity generated from fossil fuels. The amount of emission transfer is not consistent with that of purchased electricity, since some regions are rich in clean energy. Although direct emission transfer plays the dominant role for most province, indirect emission transfer should also be noticed. Provinces with larger indirect emission transfer generally purchase electricity from provinces with a lot of electricity inflows. The findings could help policy makers coordinate regional energy utilization strategies and issue more effective emission reduction policies in the electricity industry.

Thermodynamic performance evaluation of a hybrid ejector cooling and humidification-dehumidification desalination system

Energy consumption by cooling and desalination systems is huge and increasing with growing demand. The integration of two or more energy systems to form a hybrid system and work on a single energy source is one of the strategies for better energy utilization. This paper introduces a novel hybrid cooling-desalination system. The cooling unit is based on the ejector refrigeration cycle (ERC) and combined with water-heated humidification dehumidification (HDH) desalination cycle to make the hybrid system. A validated model of the hybrid system is developed and evaluated using the Engineering Equation Solver (EES) software. The basic ERC is analyzed with R134a as the refrigerant at different operating temperatures. The results show that the increase in the generator temperature improved the entrainment ratio (w) and the coefficient of performance (COP). The COP and entrainment ratio also increases with the increase in evaporator temperature. The increase in the condenser temperature resulted in a decrease in COP and entrainment ratio. The gain output ratio (GOR) of the HDH system is improved by 20%. This is due to the increase in the minimum temperature of the HDH system by 15 °C as a result of the hybrid configuration. This led to a 17% enhancement on the overall energy utilization factor.

Relationship Between Chronic Stress and Heart Rate Over Time Modulated by Gender in a Cohort of Office Workers: Cross-Sectional Study Using Wearable Technologies.

BackgroundChronic stress is increasing in prevalence and is associated with several physical and mental disorders. Although it is proven that acute stress changes physiology, much less is known about the relationship between physiology and long-term stress. Continuous measurement of vital signs in daily life and chronic stress detection algorithms could serve this purpose. For this, it is paramount to model the effects of chronic stress on human physiology and include other cofounders, such as demographics, enabling the enrichment of a population-wide approach with individual variations.ObjectiveThe main objectives of this study were to investigate the effect of chronic stress on heart rate (HR) over time while correcting for weekdays versus weekends and to test a possible modulation effect by gender and age in a healthy cohort.MethodsThroughout 2016 and 2017, healthy employees of technology companies were asked to participate in a 5-day observation stress study. They were required to wear two wearables, of which one included an electrocardiogram sensor. The derived HR was averaged per hour and served as an output for a mixed design model including a trigonometric fit over time with four harmonics (periods of 24, 12, 8, and 6 hours), gender, age, whether it was a workday or weekend day, and a chronic stress score derived from the Perceived Stress Scale (PSS) as predictors.ResultsThe study included 328 subjects, of which 142 were female and 186 were male participants, with a mean age of 38.9 (SD 10.2) years and a mean PSS score of 13.7 (SD 6.0). As main effects, gender (χ21=24.02, P<.001); the hour of the day (χ21=73.22, P<.001); the circadian harmonic (χ22=284.4, P<.001); and the harmonic over 12 hours (χ22=242.1, P<.001), over 8 hours (χ22=23.78, P<.001), and over 6 hours (χ22=82.96, P<.001) had a significant effect on HR. Two three-way interaction effects were found. The interaction of age, whether it was a workday or weekend day, and the circadian harmonic over time were significantly correlated with HR (χ22=7.13, P=.03), as well as the interaction of gender, PSS score, and the circadian harmonic over time (χ22=7.59, P=.02).ConclusionsThe results show a relationship between HR and the three-way interaction of chronic stress, gender, and the circadian harmonic. The modulation by gender might be related to evolution-based energy utilization strategies, as suggested in related literature studies. More research, including daily cortisol assessment, longer recordings, and a wider population, should be performed to confirm this interpretation. This would enable the development of more complete and personalized models of chronic stress.

Reversible electron storage in tandem photoelectrochemical cell for light driven unassisted overall water splitting

Photoelectrochemical (PEC) cell, representing as one of the most promising candidates to implement solar-driven unassisted overall water splitting, still remains a bottleneck in the construction of technology strategies for efficient solar energy utilization due to the intermittent nature of sunlight. Herein, we demonstrate an approach to realize round-the-clock hydrogen production by a solar rechargeable tandem PEC cell with two photoactive electrodes, where the photoanode is composed of a pseudocapacitive WO3 nanoflakes film sensitized with visible-light responsive zeolitic-imidazolate-framework-67 (ZIF-67), and the photocathode is constituted with a Z-scheme BiVO4-black phosphorus (BP) heterojunctions that can broaden the light absorption to near-infrared (NIR) region as well as maintain the strong redox ability to fasten hydrogen evolution reactions by the effective charge separation. Deliberately, the alignment of Fermi level between the as-prepared WO3-ZIF-67 photoanode and BiVO4-BP photocathode permits us to realize a tandem PEC cell with reversible electron storage property, enabling light-induced charge storing and on-demand release in the dark, for the application of unassisted overall water splitting. The formed tandem PEC cell shows a promising strategy for the conversion of solar power into hydrogen fuel by integrating pseudocapacitive materials into man-made photovoltaic cells, and provides a new guidance for the design of multi-functional PEC device.

Phosphorus-doped polymeric carbon nitride nanosheets for enhanced photocatalytic hydrogen production

Photocatalytic hydrogen production by water splitting is one of the most effective strategies for solar energy conversion and utilization. The metal-free polymeric carbon nitride (CN) has been widely used as an efficient photocatalyst for the photocatalytic hydrogen evolution reaction (HER). However, to date, the solar to hydrogen conversion efficiency of the CN-based photocatalysts is still low. Herein, to boost the photocatalytic activity of CN, controllable phosphorus atoms were introduced to form P-doped CN (PCN) via an evacuated ampoule calcination strategy. Compared with bare CN, the optimized PCN exhibits remarkably enhanced photocatalytic HER activity, with the HER rate up to 261.2 µmol h−1 and 171.6 µmol h−1 under the simulated solar light and visible-light illumination, respectively. It was revealed that the boosted photocatalysis for HER is mainly ascribed to the P dopants that can synergetically increase the visible-light absorption and facilitate the charge transfer process. This present work highlights improving the photocatalytic energy conversion efficiency by controllable tuning of the heteroatom doping degree in photocatalysts.

A wrinkled graphene and ionic liquid based electric generator for the sea energy harvesting

Sea energy harvesting with carbon nanomaterials is an attractive renewable energy utilization strategy. Recently, studies with the focus on electric energy generation with various graphene-based materials combined with ionic fluids have been reported. However, reliable materials for the energy generation from the mechanical movements of seawater are still a challenge. In the present work, a wrinkled graphene based highly sensitive and stable electric generator has been developed and applied to multiple seawater movements with superior performances. The electric generation mechanism from the mechanical movements of seawater including droplet movement, boundary shift, and continuous flow is explored, and the corresponding electric generation performances are evaluated. The results suggest that the surface wrinkle nanostructure of graphene can enable energy harvesting from continuously flowing ionic liquid due to the drifting of adsorbed ions and ion accumulation in the wrinkles. Based on these results, a miniaturized sea energy harvesting system is fabricated and evaluated with simulated seawater flow and tidal waves. The as-fabricated generator exhibits high sensitivity and high voltage outputs, suggesting its great application potentials as a sea energy harvesting device.

Pt Atoms on the Surfaces of Ordered and Disordered Aucu/C for Oxygen Reduction Reaction: Comparison of Electrochemical Performance and Mechanism

To mitigate the effects of dwindling fossil fuel and the detrimental climate problems originating from the excessive CO2 emission, significant efforts are required to exploit alternative clean energy resources and advanced energy utilization strategies. Owing to its high energy density, high energy efficiency and low environmental impact, proton exchange membrane fuel cells (PEMFCs) are widely considered as the ideal alternatives to replace the traditional internal combustion engines. However, the slow rate of oxygen reduction reaction (ORR) in PEMFCs is the main limitation for automotive applications. This limitation could be eliminated if stable and active cathode catalysts could be developed. Nowadays, carbon supported platinum nanoparticles (Pt/C) still serve as the state-of-the-art ORR catalyst. The high cost and limited availability of Pt seriously impede its large-scale commercialization. Though tremendous efforts have been devoted to exploiting new Pt-free catalysts, there is still a large gap in the electrochemical performance between Pt/C and Pt-free catalysts in fuel cell. One strategy is to alloy Pt with other transition metals to form as PtM (M represents other transition metal) catalysts. The introduction of a secondary transition metal could change the environment of Pt atoms including: chemical composition, catalytic surface and coordination environment. What’s more, to maximize Pt utilization for fuel cell, various methods are explored to synthesize various structure of PtM catalysts, including hollow, cage, wire, dendrites and core-shell. Due to the so-called ligand effect and strain effect, the core-shell structure where the Pt atoms are usually arranged on the surface of the as-prepared alloy, is the most promising alternative to replace the traditional commercial Pt/C. However, few literature have studied if the structure ordering of the core materials has any effects on the catalytic performance of the outmost Pt atoms. The structure ordering refers to the different atomic arrangement in the unit cell. Taking the AuCu alloy as an example, in an ordered structure, the atoms only occupy the specific site of the unit cell, while the atoms of the disordered one will randomly distribute in the cubic of lattice. It means that in any nodes of the disordered unit cell, the atoms may exist statistically according to their mole ratios. Recently, there are several reports on the ordered alloys that they could have better ORR performance than their corresponding disordered samples. The enhanced activity and durability may be attributed to their different heteroatomic bonding, surface configuration and distribution of active sites. In our previous work, we obtained the ordered and disordered AuCu/C by a post-heating treatment at different temperatures. After a systematic comparison, we demonstrated the ordered AuCu/C catalysts could exhibit superior ORR performance, which is similar to that of Pt/C, than disordered ones in 0.1 M KOH solution. However, the Cu atoms are unstable in acid electrolyte which limited its further application in PEMFCs. In present work, Cu atoms on the surface of ordered AuCu/C nanoparticles were selectively replaced by Pt atoms by means of acid leaching and wet chemical deposition (denoted as O-Pts–AuCu/C) as shown in Figure 1. For comparison, the disordered AuCu/C was also used as core material to prepare D-Pts–AuCu/C. The high resolution transmission electron microscopy （HR-TEM）and high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) coupled with line scan demonstrated the formation of as O-Pts–AuCu/C and D-Pts–AuCu/C. The electrochemical characterization displayed the O-Pts–AuCu/C have a superior activity and remarkable stability in 0.1 M HClO4 solution with respect to commercial Pt/C and D-Pts–AuCu/C. To better understand their different electrochemical performance, X-ray photoelectron spectroscopy and X-ray absorption spectroscopic measurements were performed to study the electronic structure of O-Pts–AuCu/C and D-Pt s–AuCu/C. It was found that the ordered AuCu core could exert a compressive strain on the outmost Pt atoms. Compared to D-Pts–AuCu/C, lower d-band vacancy could be observed in O-Pts–AuCu/C which could account for its superior ORR performance. Figure 1

CO2 Capture and in situ Catalytic Transformation.

The escalating rate of fossil fuel combustion contributes to excessive CO2 emission and the resulting global climate change has drawn considerable attention. Therefore, tremendous efforts have been devoted to mitigate the CO2 accumulation in the atmosphere. Carbon capture and storage (CCS) strategy has been regarded as one of the promising options for controlling CO2 build-up. However, desorption and compression of CO2 need extra energy input. To circumvent this energy issue, carbon capture and utilization (CCU) strategy has been proposed whereby CO2 can be captured and in situ activated simultaneously to participate in the subsequent conversion under mild conditions, offering valuable compounds. As an alternative to CCS, the CCU has attracted much concern. Although various absorbents have been developed for the CCU strategy, the direct, in situ chemical conversion of the captured CO2 into valuable chemicals remains in its infancies compared with the gaseous CO2 conversion. This review summarizes the recent progress on CO2 capture and in situ catalytic transformation. The contents are introduced according to the absorbent types, in which different reaction type is involved and the transformation mechanism of the captured CO2 and the role of the absorbent in the conversion are especially elucidated. We hope this review can shed light on the transformation of the captured CO2 and arouse broad concern on the CCU strategy.

Warming Alters Plant Chemical and Nutrient Compositions by Affecting Metabolites in Cunninghamia lanceolata (Lamb.) Hook

Research Highlights: Warming alters the chemical composition of Cunninghamia lanceolata (Lamb.) Hook, resulting in increased production of macromolecular compounds that protect against heat stress. Background and Objectives: Low latitude forests are experiencing obvious climatic warming; however, the plant physiological responses to warming are not well understood. As warming induces moisture stress, we hypothesized that warming activates metabolites (i.e., lipids, phenolic compounds, amino acids) and causes damage to the leaves, exemplified by the increased concentrations of reactive oxygen species. Materials and Methods: We conducted a warming experiment in a C. lanceolata plantation. Plant physiological traits associated with nutrient status, reactive oxygen species, antioxidant enzymes species, and metabolites were measured. Results: Warming altered the chemical composition of C. lanceolata as it increased C:N ratios of leaves and roots. In particular, the concentrations of N and P in leaves and roots were significantly decreased under the warming condition, which might be related to the biomass production, namely, a dilution effect. Under the warming condition, most of the phospholipid compounds and proteins significantly increased. Leaf C, carbohydrates, amino acids, organic acids, flavonoids, and phenolic compounds were identified to have significantly lower concentrations under the warming treatment than those under the control treatment. These results suggested that moisture stress under the warming treatment may drive C deficiency and metabolic restriction in plants. Conclusions: Under the warming condition, C. lanceolata changed its energy utilization strategy and invested more resources to produce macromolecular compounds for protecting against heat stress. Warming in sub-tropical forests alters plant chemical properties, and thus may have an important consequence for nutrient cycling and soil C sequestration.

Spinel-type solar-thermal conversion coatings on supercapacitors: An effective strategy for capacitance recovery at low temperatures

Solar-thermal conversion is the most direct strategy of solar energy utilization, and spinel-type transition metal oxides as photo-thermal conversion (PTC) materials have attracted great attention because of their attractive optical property and durable stability under strong sunlight or harsh temperature condition. Supercapacitors are important electrochemical energy storage devices, but sluggish ionic mobility and freezing of electrolytes at low temperatures directly lead to low or even no capacitance. Herein, we report an effective strategy to recover the charge storage ability of sandwich-type supercapacitors by employing a series of spinel-type PTC coatings. Under solar irradiation, these PTC coatings can effectively capture sunlight and convert it into thermal energy, thereby increasing the actual operation temperature of supercapacitor devices. At low ambient temperatures (−20 and −30 °C), the devices coated with Cu1.5Mn1.5O4 film showed the highest temperature increase (about 60 °C) because of the best PTC effect. Consequently, a significant capacitance improvement was achieved (from close to zero up to desirable values), thus enabling the devices to work well at such low ambient temperatures. This works offers a highly effective method to improve low-temperature performance of supercapacitors and, simultaneously, endows a new application of spinel-type PTC coatings for supporting electrochemical energy storage devices.