Korea Energy Economics Institute

Improvements to perovskite solar cells (PSCs) have focused on increasing their power conversion efficiency (PCE) and operational stability and maintaining high performance upon scale-up to module sizes. We report that replacing the commonly used mesoporous–titanium dioxide electron transport layer (ETL) with a thin layer of polyacrylic acid–stabilized tin(IV) oxide quantum dots (paa-QD-SnO 2 ) on the compact–titanium dioxide enhanced light capture and largely suppressed nonradiative recombination at the ETL–perovskite interface. The use of paa-QD-SnO 2 as electron-selective contact enabled PSCs (0.08 square centimeters) with a PCE of 25.7% (certified 25.4%) and high operational stability and facilitated the scale-up of the PSCs to larger areas. PCEs of 23.3, 21.7, and 20.6% were achieved for PSCs with active areas of 1, 20, and 64 square centimeters, respectively.

All-solid-state sodium-ion batteries that operate at room temperature are attractive candidates for use in large-scale energy storage systems. However, materials innovation in solid electrolytes is imperative to fulfill multiple requirements, including high conductivity, functional synthesis protocols for achieving intimate ionic contact with active materials, and air stability. A new, highly conductive (1.1 mS cm(-1) at 25 °C, Ea =0.20 eV) and dry air stable sodium superionic conductor, tetragonal Na3 SbS4 , is described. Importantly, Na3 SbS4 can be prepared by scalable solution processes using methanol or water, and it exhibits high conductivities of 0.1-0.3 mS cm(-1) . The solution-processed, highly conductive solidified Na3 SbS4 electrolyte coated on an active material (NaCrO2 ) demonstrates dramatically improved electrochemical performance in all-solid-state batteries.

The peer to peer (P2P) electricity trading without the need for utilities is expected to increase as the awareness of the shared economy has grown and the microgrid has spread. Furthermore, the development of renewable energy technology and the Internet technology will accelerate the dissemination of the new system. In this light, this study compares the major P2P electricity trading cases being promoted and reviews the potential development and future challenges. Since there have been little case studies of P2P electricity trading published, this study could be used as valuable information for government and corporations that are promoting or pursuing P2P electricity trading business.

Abstract For efficient water splitting, it is essential to develop inexpensive and super-efficient electrocatalysts for the oxygen evolution reaction (OER). Herein, we report a phosphate-based electrocatalyst [Fe 3 Co(PO 4 ) 4 @reduced-graphene-oxide(rGO)] showing outstanding OER performance (much higher than state-of-the-art Ir/C catalysts), the design of which was aided by first-principles calculations. This electrocatalyst displays low overpotential (237 mV at high current density 100 mA cm −2 in 1 M KOH), high turnover frequency (TOF: 0.54 s −1 ), high Faradaic efficiency (98%), and long-term durability. Its remarkable performance is ascribed to the optimal free energy for OER at Fe sites and efficient mass/charge transfer. When a Fe 3 Co(PO 4 ) 4 @rGO anodic electrode is integrated with a Pt/C cathodic electrode, the electrolyzer requires only 1.45 V to achieve 10 mA cm −2 for whole water splitting in 1 M KOH (1.39 V in 6 M KOH), which is much smaller than commercial Ir-C//Pt-C electrocatalysts. This cost-effective powerful oxygen production material with carbon-supporting substrates offers great promise for water splitting.

Using Current Population Survey data for 1983-93, this article analyzes whether there is a union membership wage premium among full-time, private sector employees covered by union contracts. Ordinary least squares estimates of the membership wage premium are 12%-14%, and allowing membership to be endogenous yields larger estimates. Differences in job tenure, unobservable characteristics, and measurement error cannot fully explain the estimated premium. Significant differences in this premium, as well as in membership rates conditional upon coverage, across various demographic subgroups are also documented. In general, "free riders" do not appear to be free riding. Copyright 2000 by University of Chicago Press.

Abstract All‐solid‐state sodium‐ion batteries that operate at room temperature are attractive candidates for use in large‐scale energy storage systems. However, materials innovation in solid electrolytes is imperative to fulfill multiple requirements, including high conductivity, functional synthesis protocols for achieving intimate ionic contact with active materials, and air stability. A new, highly conductive (1.1 mS cm −1 at 25 °C, E a =0.20 eV) and dry air stable sodium superionic conductor, tetragonal Na 3 SbS 4 , is described. Importantly, Na 3 SbS 4 can be prepared by scalable solution processes using methanol or water, and it exhibits high conductivities of 0.1–0.3 mS cm −1 . The solution‐processed, highly conductive solidified Na 3 SbS 4 electrolyte coated on an active material (NaCrO 2 ) demonstrates dramatically improved electrochemical performance in all‐solid‐state batteries.

This study investigates the relationship between the nuclear power proportion and CO2 emissions per capita using the panel dynamic ordinary least square method. The panel datasets consist of 18 countries covering 95% of the global nuclear reactors. The results indicate that a long-term 1% increase in nuclear power led to a 0.26–0.32% decrease in CO2 emissions per capita. Additionally, in France, Germany, and Switzerland they demonstrate the existence of the environmental Kuznets curve—an inverted U-shaped relationship between environmental pollution and income per capita.

To address environmental regulations on greenhouse gas emissions and depletion of fossil fuels, many countries around the world are actively promoting electric vehicles. The penetration rate of electric vehicles, however, is different in each country. What are the causal conditions of EVs adoption? To answer the question, the fuzzy-set qualitative comparative analysis methodology, fsQCA, is employed to compare the factors affecting the deployment of electric vehicles and to draw policy implications for promoting the deployment of electric vehicles. In conclusion, some effective policies, such as tax exemption, purchase subsidies, are summarized. And it can be seen that there is no single effective policy tool or the circumstances of the countries for electric vehicle supply. Therefore, in order to promote the diffusion of electric vehicles, it is necessary to promote an effective policy mix considering the circumstances of the countries concerned.

Abstract The theory of wave extrapolation is based on the square-root equation or one-way equation. The full wave equation represents waves which propagate in both directions. On the contrary, the square-root equation represents waves propagating in one direction only.

The increasing demand for advanced rechargeable batteries spurs development of new power sources beyond currently most widespread lithium-ion batteries. Here, we demonstrate a new class of flexible/rechargeable zinc (Zn)–air batteries based on multifunctional heteronanomat architecture as a scalable/versatile strategy to address this issue. In contrast to conventional electrodes that are mostly prepared by slurry-casting techniques, heteronanomat (denoted as “HM”) framework-supported electrodes are fabricated through one-pot concurrent electrospraying (for electrode powders/single-walled carbon nanotubes (SWCNTs)) and electrospinning (for polyetherimide (PEI) nanofibers) process. Zn powders (in anodes) and rambutan-shaped cobalt oxide (Co3O4)/multiwalled carbon nanotube (MWCNT) composite powders (in cathodes) are used as electrode active materials for proof of concept. The Zn (or Co3O4/MWCNT) powders are densely packed and spatially bound by the all-fibrous HM frameworks that consist of PEI nanofibers (for structural stability)/SWCNTs (for electrical conduction) networks, leading to the formation of three-dimensional bicontinuous ion/electron transport channels in the electrodes. The HM electrodes are assembled with cross-linked polyvinyl alcohol/polyvinyl acrylic acid gel polymer electrolytes (acting as zincate ion crossover-suppressing, permselective separator membranes). Benefiting from its unique structure and chemical functionalities, the HM-structured Zn–air cell significantly improves mechanical flexibility and electrochemical rechargeability, which are difficult to achieve with conventional Zn–air battery technologies.

This study aims to analyze and compare the long-run causal relationship between renewable energy consumption and economic growth for developed countries with that for less-developed countries to derive implications for long-term renewable energy policy. This study uses 1990–2010 data on 31 OECD countries (developed countries) and 49 non-OECD countries (less-developed countries) in the multivariate panel vector error correction model. The results show that the conservation hypothesis of a causal relationship between renewable energy consumption and economic growth is valid in the long run for OECD countries, and the feedback hypothesis, for non-OECD countries. This finding indicates that for developed countries, renewable energy has not played an important role in economic growth but has instead been growing by leaning on economic growth. By contrast, for less-developed countries, renewable energy has been playing an important role as a production input; similarly, economic growth has led to increased renewable energy consumption. As their economies grow, renewable energy consumption will increase in both developed countries and less-developed countries. However, policies to increase renewable energy consumption will encourage economic growth only in less-developed countries. Consequently, developed countries need to adopt a selection and concentration strategy, and less-developed countries need to adopt intensive promotion policies for renewable energy.

In predicting energy consumption, classic econometric and statistical models are used to forecast energy consumption. These models may have limitations in an increasingly fast-changing energy market, which requires big data analysis of energy consumption patterns and relevant variables using complex mathematical tools. In current literature, there are minimal comparison studies reviewing machine learning algorithms to predict energy consumption in Korea. To bridge this gap, this paper compared three different machine learning algorithms, namely the Random Forest (RF) model, XGBoost (XGB) model, and Long Short-Term Memory (LSTM) model. These algorithms were applied in Period 1 (prior to the onset of the COVID-19 pandemic) and Period 2 (after the onset of the COVID-19 pandemic). Period 1 was characterized by an upward trend in energy consumption, while Period 2 showed a reduction in energy consumption. LSTM performed best in its prediction power specifically in Period 1, and RF outperformed the other models in Period 2. Findings, therefore, suggested the applicability of machine learning to forecast energy consumption and also demonstrated that traditional econometric approaches may outperform machine learning when there is less unknown irregularity in the time series, but machine learning can work better with unexpected irregular time series data.

With the development of renewable energy, a key measure for reducing greenhouse gas emissions, interest in the levelized cost of electricity (LCOE) is increasing. Although the input variables used in the LCOE calculation, such as capacity factor, capital expenditure, annual power plant operations and maintenance cost, discount and interest rate, and economic life, vary according to region and project, most existing studies estimate the LCOE by using a deterministic methodology. In this study, the stochastic approach was used to estimate the LCOE for solar photovoltaic (PV) in South Korea. In addition, this study contributed to deriving realistic analysis results by securing the actual data generated in the solar PV project compared to the existing studies. The results indicate that the LCOE for commercial solar power ranged from KRW 115 (10 cents)/kWh to KRW 197.4 (18 cents)/kWh at a confidence level of 95%. The median was estimated at KRW 160.03 (15 cents)/kWh. The LCOE for residential solar power ranged from KRW 109.7 (10 cents)/kWh to KRW 194.1 (18 cents)/kWh at a 95% confidence level and a median value of KRW 160.03 (15 cents)/kWh. A sensitivity analysis shows that capital expenditure has the most significant impact on the LCOE for solar power, followed by the discount rate and corporate tax. This study proposes that policymakers implement energy policies to reduce solar PV hardware and soft costs.

Abstract Metal–sulfur batteries (MSBs) provide high specific capacity due to the reversible redox mechanism based on conversion reaction that makes this battery a more promising candidate for next‐generation energy storage systems. Recently, along with elemental sulfur (S 8 ), sulfurized polyacrylonitrile (SPAN), in which active sulfur moieties are covalently bounded to carbon backbone, has received significant attention as an electrode material. Importantly, SPAN can serve as a universal cathode with minimized metal–polysulfide dissolution because sulfur is immobilized through covalent bonding at the carbon backbone. Considering these unique structural features, SPAN represents a new approach beyond elemental S 8 for MSBs. However, the development of SPAN electrodes is in its infancy stage compared to conventional S 8 cathodes because several issues such as chemical structure, attached sulfur chain lengths, and over‐capacity in the first cycle remain unresolved. In addition, physical, chemical, or specific treatments are required for tuning intrinsic properties such as sulfur loading, porosity, and conductivity, which have a pivotal role in improving battery performance. This review discusses the fundamental and technological discussions on SPAN synthesis, physicochemical properties, and electrochemical performance in MSBs. Further, the essential guidance will provide research directions on SPAN electrodes for potential and industrial applications of MSBs.

Abstract An empirical framework for assisting with water quality management is proposed that relies on open‐source hydrologic data. Such data are measured periodically at fixed water stations and commonly available in time‐series form. To fully exploit the data, we suggest that observations from multiple stations should be combined into a single long‐panel data set, and an econometric model developed to estimate upstream management effects on downstream water quality. Selection of the model's functional form and explanatory variables would be informed by rating curves, and idiosyncrasies across and within stations handled in an error term by testing contemporary correlation, serial correlation, and heteroskedasticity. Our proposed approach is illustrated with an application to the Nakdong River basin in South Korea. Three alternative policies to achieve downstream BOD level targets are evaluated: upstream water treatment, greater dam discharge, and development of a new water source. Upstream water treatment directly cuts off incoming pollutants, thereby presenting the smallest variation in its downstream effects on BOD levels. Treatment is advantageous when reliability of water quality is a primary concern. Dam discharge is a flexible tool, and may be used strategically during a low‐flow season. We consider development of a new water corridor from an extant dam as our third policy option. This turns out to be the most cost‐effective way for securing lower BOD levels in the downstream target city. Even though we consider a relatively simple watershed to illustrate the usefulness of our approach, it can be adapted easily to analyze more complex upstream‐downstream issues.

Abstract Dithiocarbonate‐based non‐hygroscopic polymers with a glass transition temperature ( T g ) and polydispersity index (PDI) of ≈4 °C and 1, respectively, are synthesized through living cationic ring‐opening polymerization. These liquid‐state polymers are characterized by monodispersity based on the low T g and PDI, rendering remarkable miscibility with the perovskite precursors without aggregation. Accordingly, these polymers are added to perovskite solar cells (PSCs) to enhance their power conversion efficiency (PCE). The PCE of reference PSCs increases from 19.70% to 23.52% after direct addition of the synthesized polymer. This efficiency improvement is attributed to the considerable increases in short‐circuit current density ( J SC ) and fill factor (FF), resulting from the augmented size and defect passivation of perovskite crystals induced by added polymers. In fact, the PCE and J SC of the devices measured in the laboratory and the certification center are the highest among the reported polymer‐added PSCs, thanks to the great miscibility of the new polymers leading to the large amount addition which enables more thorough passivation among the grain boundaries. The improvement in open‐circuit voltage falls short as compared to that in J SC and FF, ascribed to the relatively moderate interaction strength between perovskite materials and dithiocarbonate groups.

Abstract Hole transport materials (HTMs) play essential roles in achieving high photovoltaic performance and long‐term stability in the n–i–p structure of perovskite solar cell (PSC) devices. Recently, dopant‐free polymeric materials as HTMs in PSCs have attracted considerable attention owing to high carrier mobility and excellent hydrophobicity. However, achieving similar efficiencies to those of doped small molecule HTMs such as Spiro‐OMeTAD is a big challenge. Herein, a thienothiophene π‐bridge is selected as a stabilizer and energy level regulator incorporated into a donor–acceptor‐type HTM to synthesize a new polymer, Nap‐SiBTA. The incorporation of the thienothiophene group improves the thermal stability and favors the high planarity and face‐on orientation, promoting high charge carrier mobility and tunable optical band gap. Finally, the dopant‐free polymer Nap‐SiBTA‐based PSC achieves an excellent power conversion efficiency (PCE) of 23.07% with a high fill factor of 80.85%. To the best of the authors’ knowledge, this is one of the best efficiencies in dopant‐free HTM PSCs. Moreover, the unencapsulated device retains 93% of its initial PCE after 1000 h owing to the excellent hydrophobicity of Nap‐SiBTA. This work provides a general and practical method to design dopant‐free HTMs for the high efficiency and long‐term stability of PSCs.

Abstract Sulfide‐based all‐solid‐state batteries (ASSBs) are next‐generation batteries, which resolve the safety issues of energy storage systems. Elaborated intimate contact by providing constant external pressure using a customized cell is a way to overcome chemo‐mechanical deterioration associated with interfacial issues; however, it is not a practical approach. Here, ASSBs are evaluated by adopting a typical coin‐type cell at low pressure (≈0.3 MPa) and it is confirmed that cathode deterioration is a more significant factor in lowering capacity retention than contact loss. Sulfide is infused surprisingly along the grain boundary of the cathode, causing gradual lithium deficiency in the cathode active materials by capturing the active lithium, which is revealed by time‐of‐flight secondary‐ion mass spectroscopy using a lithium isotope ( 6 Li). This study sheds light on the urgency of resolving the depletion of lithium ingredients during cycling rather than surface modification, by investigating the factors that accelerate degradation of the cathode during low‐pressure operation of ASSBs.

Abstract The Earth‐abundant element‐based Cu 2 ZnSn(S,Se) 4 (CZTSSe) absorber is considered as a promising material for thin‐film solar cells (TFSCs). The current record power conversion efficiency (PCE) of CZTSSe TFSCs is ≈13%, and it's still lower than CdTe and CIGS‐based TFSCs. A further breakthrough in its PCE mainly relies on deep insights into the various device fabrication conditions; accordingly, the experimental–oriented machine learning (ML) approach can be an effective way to discover key governing factors in improving PCE. The present work aims to identify the key governing factors throughout the device fabrication processes and apply them to break the saturated PCE for CZTSSe TFSCs. For realization, over 25,000 data points were broadly collected by fabricating more than 1300 CZTSSe TFSC devices and analyzed them using various ML techniques. Through extensive ML analysis, the i ‐ZnO thickness is found to be the first, while Zn/Sn compositional ratio and sulfo‐selenization temperature are other key governing factors under thin or thick i ‐ZnO thickness to achieve over 11% PCE. Based on these key governing factors, the applied random forest ML prediction model for PCE showed Adj. R 2 = >0.96. Finally, the best‐predicted ML conditions considered for experimental validation showed well‐matched experimental outcomes with different ML models.

Abstract Free‐standing trimethylolpropane ethoxylate triacrylate gel polymer electrolyte is synthesized by a chemical cross‐linking process and used as an electrolyte and separator membrane in lithium‐sulfur batteries. The cross linked gel polymer electrolyte also exhibited a stable geometric size retention of 95 % at the high temperature of 130 °C. The as‐prepared gel polymer electrolyte membrane with carbon nanofibers interlayer can effectively prevent polysulfide dissolution and shuttle effect, leading to significantly enhanced electrochemical properties, including high capacity and cycling stability, with an enhanced specific capacity of 790 mA h g −1 after 100 cycles.