Urban Energy Supply Research Articles

Risk Assessment of Urban Water and Energy Supply Using Copula Function: A Water–Energy Nexus Approach in an Arid City

Planning for the future of water and energy supply systems in urban areas requires a thorough assessment of associated risks. In this study, monthly water and energy demand data from 2011 to 2022 in an arid city was used to predict the corresponding demands from 2023 to 2032 using the seasonal auto-regressive integrated moving average (SARIMA) method. The aim is to estimate future water and energy supply risks both individually and jointly, using cumulative distribution functions (CDFs) derived from historical data. The main focus is to calculate the combined risk of water and energy, referred to as the water–energy nexus (WEN) risk. Based on the interdependent relationship between water and energy, the Copula function was utilized to model the bivariate distribution between these two variables. Pearson correlation analysis indicated a strong correlation between water and energy supplies. Among the distributions fitted to the data, the log-normal and gamma distributions were the best fit for water supply and energy supply systems, respectively, with the lowest Akaike information criterion (AIC) values. The Gumbel Copula, with a parameter of 1.66, was identified as the most suitable for modeling the joint distribution, yielding the lowest AIC value. The results indicate that the risks associated with energy supply, water supply, and their joint dependency could exceed 0.8% in the future, highlighting a potentially critical situation for the city. The trend analysis revealed that forecasted water and energy demands and their corresponding risks and the WEN risk are expected to have a significant upward trend in the future. Finally, local authorities need to explore alternative sources to supply water and energy in the future to address the ever-growing water and energy demands.

A post-disaster load supply restoration model for urban integrated energy systems based on multi-energy coordination

Urban integrated energy systems (UIES) have emerged as a promising solution to address the challenges of urban energy supply and consumption. However, UIES are vulnerable to extreme disasters, such as earthquakes, hurricanes, or floods, which can disrupt the energy infrastructure and lead to power outages and energy shortages. This study introduces a novel approach aimed at enhancing the resilience and load recovery capabilities of UIES in the face of extreme events. The proposed approach encompasses several key innovations, including the comprehensive coordination of local energy sources, prioritized restoration of critical loads, and a node-based modeling approach for gas and heat networks. Firstly, by fully integrating electricity, gas, and heat sources, the overall resilience of UIES is significantly improved, ensuring higher levels of load recovery even in the event of energy supply shortages. Secondly, the critical load recovery is prioritized by load classification, and the weights set can fully consider the connection status and load level of nodes to ensure priority provisioning of important node loads. In addition, the node-based modeling approach allows for accurate consideration of the flow of gas and heat in the pipe during modeling of the pipe energy storage. Finally, the case study section conducts simulation experiments with the UIES E33-G20-H6 test system to verify the effectiveness of the proposed approach and to demonstrate its potential in enhancing the post-disaster load recovery capability of UIES.

Service equilibrium of urban transportation energy supply station based on cooperative game

PurposeAs of December 2022, there were 119,000 gas stations, 10,800 gas stations and 4,488,000 charging piles nationwide, while the number of vehicles reached 312 million, including 11.49 million new energy vehicles. The imbalance between transportation energy supply and energy replenishment demand leads to crowded queues of vehicles at some stations and idle resources in others. How to reduce the phenomenon of large queues and improve the utilization rate of idle resources is the key to alleviating the imbalance between supply and demand.Design/methodology/approachTherefore, from the perspective of spatio-temporal equilibrium of urban transportation energy supply stations, multi-energy supply station cooperation is established in view of the phenomenon of large spatio-temporal differences among different energy supply stations, and corresponding inducing strategies are adopted for energy supplement vehicles in the road network, so that part of queued users go to energy supply stations with fewer vehicles, so as to balance the supply and demand of transportation energy in the region. On this basis, the income distribution of urban transportation energy supply station is discussed.FindingsThe total revenue after the cooperation was 13,095, an increase of 22.9%. Secondly, in terms of distribution rationality, three impact factors are selected and Shapley correction value is used to distribute the total income. Compared with independent operation, both sites have a certain degree of increase.Originality/valueTraffic congestion at energy supply stations is closely related to the number, location and number of vehicles at energy supply stations. Therefore, using a cooperative approach of energy trading cannot solve the queuing problem. In addition, there are a few research results on the equalization of energy supply station services considering time-of-use pricing. However, these studies do not consider the vehicular grooming at congested stations. As far as the authors know, there are no relevant research results in the research on the service equilibrium of energy supply stations based on cooperative games.

An environmentally friendly process design of an innovative CCHP-desalination system combined with a geothermal cycle and LNG regasification unit

The importance of geothermal energy in the urban energy supply is derived from its renewable nature, power generation capabilities, and potential for lowering air pollutants. The utilization of combined arrangements utilizing geothermal energy represents an outstanding alternative option. Hence, present investigation proposes a novel and environmentally friendly multigeneration framework for a geothermal energy resource, incorporating combined cooling, heating, power (CCHP), and desalination systems. Furthermore, the entire system includes a liquefied natural gas regasification unit. The present study simulates the system utilizing the Aspen HYSYS software, wherein a comprehensive analysis is conducted on considerations of energy, exergy, economics, and environment. The study also includes a comprehensive parametric study. According to the study's findings, the system can generate 863.8 kg/s of hot water, 22.01 kg/s of chilled water, and 59.67 kg/s of fresh water, along with a power output potential of 120,185 kW. Besides, this process yields energy, thermal, and electrical efficiencies at 25.08 %, 10.25 %, and 14.12 %, correspondingly. The exergy analysis findings demonstrate that the system's efficiency for power generation and multigeneration modes is 45.17 % and 47.79 %, respectively. From the economic aspect, the total unit cost of products is found at 2.91 $/GJ and the cost of energy at 0.0962 $/kWh.

Day-ahead robust optimal dispatching method for urban power grids containing high proportion of renewable energy

Urban energy supply includes more renewable energy, but renewable energy, such as wind and photovoltaic, is intermittent and connected to the grid and impacts the safe operation of the power system. For urban multi-type energy dispatching, this paper proposed a day-ahead multi-energy robust optimization dispatching method for an urban power grid with a high proportion of renewable power. Firstly, the power supply and load operation scenarios of the urban energy supply system are constructed. Multiple typical scenarios are formed based on fully considering the uncertainties caused by renewable energy and load prediction. A robust optimal scheduling model with system constraints was constructed based on the tuning capacity of adjustable generator sets and energy storage devices in the power grid, with multi-system functional cost optimization as the objective function. Extending the augmented Lagrange multiplier Method, the Alternating Direction Method of Multipliers (ADMM) is proposed to solve the constructed model. The effectiveness of the proposed method is verified by some examples based on the data of an actual power grid in China.

Prediction and comparison of urban electricity consumption based on grey system theory: A case study of 30 southern China cities

Rapid urbanization has put heavy pressure on urban energy supply over the past decades in China and such a trend is expected to continue. Therefore, it is critical to capture the impacts of key factors on urban energy consumption and further predict its future growth. This study proposes a framework to predict urban-scale electricity consumption which incorporates an original urban information database with 18 macroeconomic factors and 2 electricity consumption indicators. The grey prediction model is the core for prediction, whose performance is investigated in the established database. Meanwhile, multiple strategies, e.g., variable screening and optimal data allocation, have been conducted to improve the accuracy of the prediction. A case study of 30 cities in southern China indicates that the established database can well represent the relation between urban development and energy consumption. The proposed prediction framework performs well in forecasting urban-scale electricity consumption with less than 10 % of mean absolute percentage error, showing a positive correlation between model accuracy and data amount. Overall, the proposed prediction framework generates valuable insights into the interaction between urban development and electricity consumption, which can quantitatively inform urban designers when planning urban energy systems.

Study on the Performance of Photovoltaic/Thermal Collector–Heat Pump–Absorption Chiller Tri-Generation Supply System

The solar energy supply system has played an increasingly substantial role in realizing nearly zero-carbon buildings. In order to overcome the impact of solar randomness on the energy supply of a distributed solar system, this paper proposes a solar tri-generation supply system which integrates a photovoltaic/thermal collector (PV/T), a heat pump (HP), and an absorption chiller (AC). The PV/T-HP integration system is adopted to provide stable heating for a building and AC. The system model is established in TRNSYS software, and its performance is evaluated based on energy, exergy, and economic aspects. The results demonstrate that the system effectively meets the load demand, with an energy efficiency of 32.98% and an exergy efficiency of 17.62%. The payback period (PP) is 7.77 years. Compared with the systems proposed in the other literature, the performance of the proposed system has a certain extent of advantage. Furthermore, the equipment and system exergy performance decline with an increase in the intensity of solar radiation. Increasing the PV/T area effectively improves the system’s profitability within the actual roof area limitation of the building. Moreover, increasing the capacity of the low-temperature heat pump after 68 kW improves the system efficiency and reduces the payback period. In summary, this paper proposes an efficient distributed solar energy system that is suitable for urban building energy supply.

Negative Effect Prediction and Refueling Traffic Flow Equilibrium of Urban Energy Supply Network during Weekends and Holidays

With the continuous improvement of people’s living standards, the travel demand for vehicles increases rapidly during weekends and holidays. This situation leads to a number of negative impacts on the transport network, such as traffic congestion, carbon emissions, and long queues at refueling stations. The impact of vehicles requiring energy replenishment on the negative effect is nonlinear. Therefore, the negative effect data of working days cannot be directly used to evaluate the cost, and the traffic equilibrium allocation problem also needs to be solved. An equilibrium allocation model of hybrid vehicles considering the energy replenishment demand in holidays is established, aiming at minimizing the total time cost and energy consumption cost. The Frank–Wolfe algorithm is used to solve the traffic allocation problem in advance, and the negative effect of the urban energy network during holidays is predicted by the Genetic Algorithm—Back Propagation (GA-BP) algorithm. Then, the energy-replenishing vehicles in the traffic network are induced to reduce the total cost. Finally, taking the actual road network in Jiulongpo District of Chongqing City, southwest of China, as an example, the negative effects of multiple stations are predicted. The results show that the prediction method proposed in this paper is effective during holiday periods. In addition, as the market share of electric vehicles increases, the negative cost can decrease gradually. The predicted results can provide a reference for traffic managers.

Dynamic Interactions between Local Energy Systems Coupled by Power and Gas Distribution Networks

Supplied with electricity and natural gas, local energy systems (LESs) with gas-fired generations increase the operational flexibility of urban energy supply. However, the increasing usage of these LESs may lead to adverse impacts on the urban energy system supply via power and/or gas distribution networks. Dynamic interactions between the LESs, electricity, and gas networks subject to different disturbances need to be investigated due to the complexity of the problem. To address this issue, this paper first presents the topology and operating mode of the LESs as well as the relationship with power and gas networks. Second, an extended microturbine model is developed to reflect the nonlinear dynamic propagation of disturbances between the two networks. A general model of the interconnected LESs is developed to analyze the mutual impacts between gas and electricity networks under different modes. Finally, an iterative method is proposed to simulate the mechanism of disturbance propagation between the electricity network, gas network, and LESs, incorporating the impacts of loads and renewables. Case studies reveal that simultaneous regulation of multiple gas-fired generators would reduce the minimum pressure to 50% of the steady-state value. The resulted pressure drop is even lower than the case with higher total gas demand but only one gas-fired generator regulated. Moreover, it is shown that state fluctuations of the gas system last 20 times longer than the electricity system within the LESs. The electrical link between LESs, such as soft opening point with shorter response time, could smooth the fluctuations.

Resilience Oriented Planning of Urban Multi-Energy Systems With Generalized Energy Storage Sources

In the last decade, a number of severe urban power outages have been caused by extreme natural disasters, e.g., hurricanes, snowstorms and earthquakes, which highlights the need for rethinking current planning principles of urban energy systems and expanding the classical reliability-oriented view. In addition to being reliable to low-impact and high-probability outages, power system should also have high level of resilience to withstand high-impact and low-probability (HILP) events. Compared with power system, multi-energy systems (MESs) have advantages in improving resilience through energy shifting across multiple energy sectors, a variety of generalized energy storage resources and thermal inertia of heat/cooling loads. This paper proposes a resilience-oriented planning method to determine optimal configuration of distribution level MES, e.g., urban energy supply systems, considering comprehensive impacts from supply, network and demand sides in MES. Impacts of energy shifting at supply side, pipe storage at network side and thermal inertia at demand side are described in the same linear modeling framework using energy hub (EH) model. Generalized energy storage resources including centralized and distributed energy storage devices, pipe network storage and building heat capacity are all modeled into centralized energy storage to facilitate an efficient configuration planning of MES.

Способы повышения эффективности территориальных систем энергоснабжения

Исследованы системы энергоснабжения, в составе которых имеются источники, использующие различные технологии совместного производства тепловой и электрической энергии. В крупных городах России высока доля поставок тепловой энергии от теплоэлектроцентралей, но в больших и средних – доминирует ее производство на котельных. Соотношение объемов производимой совместным способом тепловой и электрической энергии с общим потреблением позволяет судить о состоянии и эффективности территориальных систем энергоснабжения. Практически повсеместное отсутствие коммунальных мини-ТЭЦ и ограничение на поставку электроэнергии, произведенной крупными ТЭЦ в теплофикационном режиме на розничный рынок, ведут к снижению эффективности городских и региональных систем энергоснабжения. Основное число потребителей, кроме предприятий, использующих собственные когенерационные источники, ограничены в доступе к недорогой тепловой и электрической энергии. Актуально увеличение доли когенерационного производства энергии. Необходим показатель, характеризующий уровень интеграции источников совместного производства тепловой и электрической энергии в системах энергоснабжения. Основной потенциал создания интегрированных систем энергоснабжения сосредоточен в больших и средних городах, где производство тепловой энергии осуществляется на котельных. Их преобразование в мини-ТЭЦ соответствует стратегии энергетического перехода к распределенной энергетике, но требует внесения изменений в процесс управления развитием муниципальной и региональной энергетики. Наличие благоприятных условий для частных инвестиций в развитие интегрированных систем энергоснабжения соответствует целям устойчивого социально-экономического развития территорий.

Efficiency enhancement of a solar trough collector by combining solar and hot mirrors

Parabolic trough collector is an up-and-coming technology for urban energy supply. To further enhance the optical-thermal efficiency of the collector, a modified receiver enhanced by solar and hot mirrors was proposed. In this receiver, two symmetrical solar mirrors were designed to collect more solar irradiance, and a transparent hot-mirror shield was employed to lessen the thermal loss. After the design, the collector performance was studied by developing an optical-thermal coupled model. Based on the model, firstly, the proposed receiver was compared with the conventional receiver and two existing modified receivers. Results indicate the proposed receiver can achieve an optical efficiency of 78.02%, which is higher than those of the existing modified receivers and is just 0.22% lower than that of the conventional one. Moreover, compared with the conventional receiver, the two existing modified receivers cannot improve the optical-thermal efficiency at sufficiently high direct normal irradiance or relatively low fluid temperature, which can be overcome by the proposed receiver. Furthermore, compared with the conventional receiver, the proposed receiver can lessen the thermal loss by 11.2–89.6 W·m−1, thus improving the receiver efficiency and the optical-thermal efficiency by 0.03–5.26% and 0.03–4.70%, respectively, under the typical ranges of the inlet temperature (573–823 K) and the direct normal irradiance (0.3–1 kW·m−2). Then, parameter analysis indicates the hot mirror with low emissivity is necessary for efficiently improving the optical-thermal efficiency. Finally, the proposed receiver can improve the optical-thermal efficiency more effectively at higher fluid temperature or larger coating emissivity. The above results signify that the proposed receiver can be helpful for enhancing the efficiency of the trough collector.

A systematic approach for data analysis and prediction methods for annual energy profiles: An example for school buildings in Norway

Current research on energy supply systems and building energy demand presents positive impacts from the two sides, with potentials of combining top-down and bottom-up modelling. Mostly, the energy demand input has been employed directly from energy utility companies as a package of information, without considering energy use patterns regarding building type. There lacks a bridge between demand profiles on building stock functions and urban energy supply systems. Accordingly, this article proposes a framework that enables the prediction of annual energy profiles, applied to one educational building type on an hourly basis. The work consists of five steps: (1) getting energy information of 40 district heating (DH) supplied schools in Norway, (2, 3) processing data for getting the modified average hourly demand per m2 and holiday breakpoints through a modified Z-Score, (4) energy forecast of DH and electricity load profiles through temperature moving average, correlation, and linear regression analysis, (5) validation of the predicted yearly profiles by three criteria, and further with the cluster methods for DH profiles. The results showed that the suggested methods for annual energy forecast were satisfying. The defined load profiles might represent the current energy demand of the Nordic school and the methods could be transferred to other building types. With energy analysis of typical building types, the proposed method enables the planners to better understand the energy needs for different building functions.

Rethinking infrastructure rehabilitation: Conflict resilience of urban water and energy supply in the Middle East and South Sudan

Protracted armed conflicts in the Middle East and Africa are heavily impacting the infrastructure of basic services such as water, energy, healthcare, and education. People adapt to these persistent conditions through self-organization, private sector-driven services and the reliance on international aid. In rehabilitating infrastructure damaged by conflicts, there is a rift between the perspectives of emergency aid and development cooperation. In fragile states, aid often fails to capture the temporal aspects of infrastructure in terms of its vulnerability to recurrent breakouts of conflicts and infrastructure’s long-term resilience. Besides, the issue of conflict resilience of basic infrastructure is lacking academic attention in terms of determining factors and best practices. In this paper, three examples of promising adaptation efforts are analyzed: the construction of water kiosks in South Sudan, self-organized markets for solar energy applications in Yemen, and the integration of schools with basic services in Syria. Using a comprehensive assessment framework of micro-level vulnerability (a system-unit risk perspective) and macro-level resilience (a whole-system strategy perspective), this paper highlights critical areas for enhancing conflict resilience in the case studies. It shows the importance of rethinking aspects of infrastructure development such as interconnectivity, mobility, centralization, or missing baselines. Infrastructure reconstruction efforts need to find a balance between highly integrated infrastructure systems and community-level production and delivery options. Further, for improving long-term infrastructure performance in conflict-ridden areas, softer issues need to be addressed, e.g., local capacities, institutional development, community trust, and the mobilization of reuse options or locally available resources.

Application of Compressed Air Energy Storage in Urban Buildings Energy Supply

Urban buildings consume a lot of energy every year. Through analyzing the characteristics of urban buildings energy supply and compressed air energy storage (CAES) and considering the electric energy, thermal and cold energy output from CAES, this paper constructs the overall framework of CAES providing urban buildings with combined cooling, heating and power (CCHP), which can meet the energy demand of urban buildings, improve the system efficiency of CAES, make profit from the peak and valley electric charges difference of power grid, and it also has a broad range of popularization and application.

Urban integrated energy demand forecasting method considering multi-station fusion

Under the background of energy reform, China’s energy-related industries actively innovate from the top to the bottom, vigorously promote the “Internet + Energy” strategy, and promote multi-station integration to deeply integrate energy, information communication and other pillar industries of the national economy to help China’s industrial upgrading and economic development. This paper proposes a method for forecasting urban comprehensive energy supply and demand that considers multi-station integration. Through the prediction and analysis of energy supply and demand under various scenarios of multi-station fusion, the comprehensive energy design scheme under different types of multi-station fusion scenarios is clarified to assist the early development of market developers and provide decision support for the promotion and application of comprehensive energy technology facing multi-station fusion.

Promoting the Construction of Xiongan New Area Through Energy Revolution: General Idea and Implementation Route

Based on the strategic background, positioning, and objectives of the planning and construction of the Xiongan New Area, an analysis model framework is established for the requirements for energy revolution during the planning and construction of this area. We conclude that energy revolution can actively promote the construction of the Xiongan New Area. Specifically, energy technology revolution can aid the Xiongan New Area to become a global energy innovation center; the energy operation mode of this area can be reformed through energy system revolution; the planning and construction requirements of the Xiongan New Area can be satisfied through energy consumption revolution; and a safe and efficient energy supply system can be ensured through energy supply revolution. Furthermore, an urban energy supply system that is green, safe, efficient, smart-friendly, and future-leading can be created in the Xiongan New Area through the energy revolution, particularly through key projects regarding energy integrated operation systems, energy Internet, green and smart transportation systems, ultra-low-energy buildings, and energy saving and emission reduction.

Collaborative Multidepot Petrol Station Replenishment Problem with Multicompartments and Time Window Assignment

Energy supply is an important system that affects the overall efficiency of urban transportation. To improve the system operational efficiency and reduce costs, we formulate and solve a collaborative multidepot petrol station replenishment problem with multicompartments and time window assignment by establishing a mixed-integer linear programming model. The hybrid heuristic algorithm composed of genetic algorithm and particle swarm optimization is used as a solution, and then the Shapley value method is applied to analyze the profit allocation of each petrol depot under different coalitions. The optimal membership sequence of the cooperation is determined according to the strict monotone path. To analyze and verify the effectiveness of the proposed method, a regional petrol supply network in Chongqing city in China is investigated. Through cooperation between petrol depots in the supply network, the utilization of customer clustering, time window coordination, and distribution truck sharing can significantly reduce the total operation costs and improve the efficiency of urban transportation energy supply. This approach can provide theoretical support for relevant government departments and enterprises to make optimal decisions. The implementation of the joint distribution of energy can promote the sustainable development of urban transportation.

Stakeholder demands and regulatory framework for community energy storage with a focus on Germany

Community energy storage (CES) can provide for a variety of services and offers the possibility of combining individual needs with grid services. Hence, CES has the potential to play an important role in the energy transition, especially for a sustainable urban energy supply. In Germany, however, progress in this field has been slow due to a complex regulatory framework and limited transdisciplinary research.This paper focuses on an analysis of the regulatory framework in Germany and the demands of the various stakeholders. What opportunities does CES hold for private and public stakeholders? What are the barriers? To answer this, we conducted a literature review on CES, identifying the regulatory and political framework in Germany and Europe. In spring 2018, we conducted structured interviews with 17 professionals from various municipalities, regional authorities, energy suppliers, grid operators, and storage manufacturers.Both the literature review and our interviews show that in order to achieve greater implementation CES needs to fulfil multiple services to optimize its utility and meet the demands of all stakeholders. Moreover, our research reveals that in Germany one of the biggest obstacles faced by CES, other than a complex regulatory framework, is the lack of a clear legal definition.

Spatial and temporal considerations in the performance of wastewater heat recovery systems

Abstract In December 2018, wastewater was officially recognized by the European Union as a renewable source of energy, thus wastewater heat recovery can be included in efforts to reduce greenhouse gas emissions. Given the fact that wastewater treatment plants can generate enormous heat surpluses, this decision gives leeway to couple the wastewater infrastructure with the energy system in order to increase energy efficiency at the system level, allow for power to heat solutions in order to integrate volatile renewable electricity generation and, thus, foster a sustainable energy transition and cleaner production. Yet, the success of these system integrations depends on the availability of energy consumers in proximity of the wastewater treatment plants, and the temporal patterns of energy supply and energy demand. So far, the importance of both temporal and spatial variations in performance of wastewater heat recovery systems have been discussed in literature, but only as separate considerations to date. In order to exhaust the potential of wastewater energy, the combination of both aspects still has to be studied sufficiently, and this paper aims at filling that gap. A three-step methodology is proposed, including an energetic analysis at the wastewater treatment plant, a spatio-temporal analysis of supply and demand in potential supply areas, and an integrated analysis, overlaying the supply and demand profiles. This allows to account for both the proximity of consumers and potential temporal mismatches between supply and demand. The methodology was applied on a case study in Ireland, being able to clearly identify potentials and pitfalls for laying out grids and dimensioning the energy generation systems. It can be concluded, that wastewater energy is a well-suited source of energy to supply baseloads, but the spatio-temporal patterns reveal that both periods of excess wastewater heat potentials as well as additional heating in bivalent systems is required. Therefore, the spatial – urban and regional – fabric, the mix of land uses and their density, largely determine the layout and the useable amount of this renewable energy source. Finally, it can be concluded, that the use of wastewater energy provides feasible and valuable contributions for sustainable urban energy supply systems and cleaner production if the electricity sources for the respective heat pump systems are renewable guaranteeing low-to zero-emission operation.