The energy transition sometimes encounters challenges on balancing three competing goals, i.e., costs, emissions, and resilience (the so-called Energy Trilemma). Such trade-offs are particularly conspicuous for coastal cities, which usually have more ambitious emission reduction targets and are more likely under threat of extreme weather events, i.e., typhoon. This study develops a bottom-up optimisation framework to assess the sustainable transition of the electricity sector for a typical coastal city of Xiamen, China. The framework optimises the energy portfolio for 20-year-horizon with hourly temporal resolution considering demand-side flexibility of energy storage. By setting multiple optimisation objectives, three representative transition scenarios are evaluated: the least-cost scenario, the least-emissions scenario, and the diversity-optimal scenario. The trade-offs between competing objectives are presented as Pareto frontiers and posterior decision-making methods are further embedded to identify one superior solution and facilitate the policymaking. The optimisation results indicate that with the limited potential of solar and wind and other renewable resources, the electricity transition of Xiamen would rely on the import power to a large extent. An extra 3.9% cost than the least-cost pathway can achieve a pathway with maximum energy diversity to enhance the resilience, whereas 27% more cost than the least-cost pathway is needed to achieve the least-emissions pathway. In addition, the first 10-year modelling results are further verified by comparison with the real-world data to generate valuable insights into sustainable transition pathways of coastal cities.
Owing to the potential higher energy supply efficiency and operational flexibility, integrated energy system (IES), including the power, gas, heating, and cooling systems, will be one of the primary forms of energy carrier in the future. However, with the increase of multiple energy devices and systems integration, IES planning is facing a significant challenge in terms of risk assessment. Therefore, a conditional value-at-risk (CVaR) based energy hub (EH) planning model is proposed in this paper. The numerical results illustrate the proposed methodâ€™s effectiveness in balance the potential operation risk and investment cost, while the benefits of introducing energy storage system (ESS) are also verified.
The Clean Development Mechanism (CDM) is an important approach that developed and developing countries can take actual actions to mitigate global climate change. Both carbon reduction and sustainable development are the goals of CDM. However, the uneven distribution of CDM projects in the developing countries may jeopardize the fulfilling of the goals. This paper used a panel data of 107 host countries and explored the influencing factors with the panel negative binomial regression. And the club convergence model is used to divide the host countries into different groups according to their numbers of operating CDM projects each year. The results show that the affluence, the sophisticated international trading experience and the growing demands for energy of the host countries have positive impact on the successful registrations of the CDM projects, while the cost of carbon emission abatement hinders the registration. But for countries with less CDM projects, the industrial level and national carbon emission have no significant impacts on the distribution of CDM projects. In the end, target policy implications were offered according to the results.
Potential energy savings of the central air-conditioning systems can be induced by the indirect evaporative cooler (IEC) through energy recovery from exhaust air to the fresh air. However, the condensation in the dry channels can pose significant influences on cooling performance, especially for the IEC used in hot and humid areas. In this paper, a novel IEC heat exchanger was fabricated by depositing the hydrophobic nanoparticles on the surfaces of primary air channels, and experiments were conducted to compare its performance with the traditional uncoated IEC. The droplet behaviors on the plate surfaces with and without hydrophobic coating were compared under both dynamic and steady states. Results show that, the hydrophobic coating produces a higher contact angle for the plate surface, causing a reduced size of falling-off droplets and frequent droplets removal. The dropwise condensation on the hydrophobic surface has less deterioration effect on the convective heat transfer of primary air flowing over the heat exchange plates. Under dehumidifying conditions, the hydrophobic coating treatment on the primary air channel surfaces of the IEC could enhance the heat and mass transfer and improve the energy-saving rate by 8.5-17.2%, promising a great application potential for upgrading the evaporative cooling technologies in humid regions.
This paper considers domain knowledge of photovoltaic (PV) and proposes a theory-guided long-short-term memory (Tg-LSTM) framework to forecast the hourly day-ahead PV power generation (PVPG). It aims to overcome the shortcoming of recent machine learning algorithms that are applied based only on massive data, and are thus easily producing unreasonable forecasts. Real-life PV datasets are adopted to evaluate the feasibility and effectiveness of the models. The results indicate that the proposed Tg-LSTM model possesses stronger forecasting capability than the standard LSTM model. It is more robust against PVPG forecasting, and more suitable for PVPG forecasting with sparse data in practice. The Tg-LSTM model also demonstrates superior performance with higher accuracy of PVPG forecasting compared to conventional machine learning methods.
Integrating energy storage technology with renewable energy can improve largely the penetration of renewable energy. A novel energy storage system based on compressed air energy storage, electrical heater and Kalina cycle is thus proposed. This work focuses on demonstrating the feasiblity and effectiveness of the hybrid system for achieving the energy cascade utilization through parametric analysis. Results show that within certain ranges, higher discharging pressure and lower electrical heating temperature are beneficial for increasing round trip efficiency of the hybrid system. Decreasing discharging pressure and increasing separator pressure would reach higher power production of the Kalina cycle turbine.
Urban water-energy nexus is regarded to be highly important for the sustainable development of cities and the effective management of resources. Research methods on urban water-energy nexus are emerging, and a summary of these methods can help to determine the appropriate tool to manage urban water and energy. The accounting of energy and water in existing nexus research is not consistent, so the results and evaluation are also different. From supply to end-use, account the water and energy consumed in each stage, and the factors that affect the consumption of both in each process are analyzed. Review the latest development of research methods and models in urban water-energy nexus, and propose their advantages and limitations. For systematic models, the determination of parameters and the upgradation are still a huge challenge. In the future, more attention should be paid to the coupling and combination of various methods to understand urban water-energy nexus from a multi-scale perspective. In addition, future research directions should also pay more attention to the internal mechanisms and driving factors of urban water- energy nexus, and how to deal with the nexus under climate change, the interaction with other resources such as food, and the change of urban water and energy under policy control.
High penetration of renewable energy and the random real-time charging of large-scale electric vehicles are challenging to traditional urban power system technically and economically. This urgently calls for accelerating the development of smart energy solutions to improve the resilience of urban power system, and mobilized and distributed battery is believed to have the potential to provide the solution due to the advantages of high energy density, fast response, and convenient installation. Aiming at effectively satisfying the enormous urban power demand and realizing the cost-effectiveness and environmental-sustainability of power supply, this paper develops a novel method to achieve logistics and scheduling optimization of batteries at various temporal and spatial scales between renewable energy power plants (REPs) and cities. The objective function is to minimize the total cost of battery purchase and transportation considering the railway transport capacity, battery balance and other technical constraints. Based on the forecast results of available supply and demand of fully charged batteries in each REP and city, the detail battery transportation route and volume can be obtained. Finally, the proposed approach is applied to six cities in China, and the results demonstrate that the battery logistics and scheduling model can effectively improve the penetration of renewable energy, thereby realizing the low-carbon development of urban energy system.
With the rapid development of China’s economy, the contradiction between the growing demand for fossil energy consumption and the increasingly urgent pressure of emission reduction has become increasingly prominent. As a potential option to address climate change, CO2 enhanced coalbed methane recovery (CO2-ECBM) technology has been widely concerned, which can inject the CO2 captured into the coalbed to enhance coalbed methane recovery and store CO2 at the same time. Therefore, CO2-ECBM technology is of great significance for China’s low-carbon development, especially after China put forward the goal of achieving carbon neutrality by 2060. In order to provide references for CO2-ECBM technology deployment, the investment benefits of the CO2-ECBM project in China under various scenarios was evaluated based on real options in this study, and the key factors influencing the economy of the CO2-ECBM technology were also identified. The results showed that (1) without carbon trading, the investment benefits of CO2-ECBM project is 2.58 billion CNY in low CO2 source purchase price scenario(180 CNY/t); (2) if CO2 source purchase price rises to 300 CNY/t (high CO2 source price scenario), the CO2-ECBM project has no investment value as its revenues cannot offset the total costs; (3) the net present value (NPV) of CO2-ECBM project will decrease by 22.76 million CNY if the CO2 source purchase price increases 1 CNY/t, and the critical CO2 source purchase price is 293 CNY/t without carbon trading; (4) Carbon trading can greatly increase the investment income of CO2-ECBM projects, and in the low CO2 source purchase price scenario, the investment benefits of CO2-ECBM projects would increase by 44.2% with the current carbon trading price (50 CNY/t). However, China has not yet incorporated CO2 utilization technology into the emission trading system. The results of this study could provide theoretical support for CO2-ECBM investment and the relevant policy-making.
As a formal means of environmental regulation, environmental tax receives extensive attention from scholars for its emission reduction effect and economic impact. However, few studies have focused on the regulatory effect and impact mechanism of Environmental Information Disclosure (EID) and other informal environmental regulatory methods, especially the heterogeneity of such regulatory effect at the time and industry level. Therefore, based on China input-output tables and pollutant emission data of 139 sectors in 2012, this paper constructed China environmental Computable General Equilibrium (CGE) model for empirical test. Studies have shown that the improvement of EID has a â€œdouble dividendâ€ regulatory effect on emission reduction and economic impact of environmental tax, but this effect has obvious time and industry heterogeneity. Specifically, the long-run economic stimulus effect of EID improvement (0.087%) is greater than that of the short-run (0.037%), while the long-run enhanced effect of EID on exhaust emission reduction (SO2 -0.015%ï¼›NOX -0.014%) is less than that in the short-run (SO2 -0.081%ï¼›NOX -0.076%). In terms of the comparisons between the two, in the short-run, the enhanced effect of EID on environmental taxâ€™s emission reduction is greater than its effect on economic improvement. While in the long run, the effect on the former is less than its effect on the latter. Meanwhile, the improvement of EID has a weaking effect on reducing wastewater discharge reduction of environmental tax. From the industry perspective, the improvement of EID quality can drive the output growth of the industry in the short run and long run by 64% and 93% respectively. Nonetheless, there exists significant non-uniformity. Among them, production of capital-intensive investment products and its upstream industries have increased emissions when output has expanded significantly, while the output of labor-intensive and export-oriented industries have suffered due to factor prices that have been pushed up. It is worth noting that the improvement of EID quality can stimulate the energy consumption structure to shift from high-emission coal towards clean energy products in the long run. This research can provide references for objectively understanding the complementary role of informal environmental regulation to formal environmental regulation, and promote the construction of a modern environmental governance system with multi-party co-governance.