Multi-energy Complementary Systems Research Articles

Optimal operation for district cooling systems coupled with ice storage units based on the per-unit value form

The integration of non-dispatchable renewable resources into the power system, as part of efforts to mitigate carbon emissions and achieve carbon neutrality, presents a significant problem in maintaining the balance between generation and consumption within multi-energy complementary systems. The widespread adoption of district cooling systems (DCS) with ice storage units has proven to be a highly effective approach for enhancing flexibility by changing the operating schedule or adopting different control strategies to participate in demand response, reducing load peaks or peaking and filling to improve system economy. However, the nonlinearity and the presence of multiple variables with different orders of magnitude of the DCS model pose a significant challenge for arithmetic operations well. The present study establishes models based on per-unit value for DCS coupled with ice storage units, and employes several objective functions to validate the selection of base values, demonstrating the superiority of the calculation process for per-unit value model. Simulation results show that, the adoption of per-unit value models of DCS significantly reduce the calculation time, particularly for large systems where it would be possible to have a reduction in time-consuming by more than 68%. Additionally, this paper suggests an operational strategy for real DCS that incorporates demand response by per-unit value models, demonstrating the efficacy of the proposed approach in achieving a reduction of 11.17% in operating costs, while simultaneously enhancing flexibility to meet the load demands of multi-energy complementary systems.

Comprehensive evaluation of the working mode of multi-energy complementary heating systems in rural areas based on the entropy-TOPSIS model

BackgroundThe establishment of a multi-energy complementary heating system (MECHS) using abundant renewable energy is currently an effective way to solve the rapid growth of heating demands in rural areas. However, coupling schemes for different energy sources have become a critical barrier to the MECHS development. ObjectivesThe entropy-TOPSIS method was used to conduct a comprehensive evaluation of MECHS, which provided a basis for optimizing system operation strategy. MethodsWe built a test platform for MECHS based on solar-biomass-electricity energy in Tumxuk, Northwest China. Frist, six working modes were established according to the system operation control strategy. Second, we constructed the evaluation indexes of MECHS considering energy, environment and economy and determined their weights using entropy weight method. Third, the TOPSIS model was used to perform a comprehensive evaluation of the different working modes to identify optimal energy supply schemes. ResultsOur case study showed that the MECHS operated stably and met the indoor temperature demands of rural houses in cold regions. To maximize the heating efficiency of the system, it is necessary to reduce the types of energy appropriately. Next, based on entropy-TOPSIS model, the recommended order of energy supply mode for heating systems were solar-biomass energy (0.6202), solar-biomass-electric energy (0.6152), solar-electric energy (0.5895), biomass energy (0.4075), biomass-electric energy (0.3680), and electrical energy (0.3603). We found that the optimal energy supply mode was solar-biomass. ConclusionOur results indicated that the entropy-TOPSIS model could provide practical recommendations for the design and operation strategies of MECHS in cold rural areas.

A case study of multi-energy complementary systems for the building based on Modelica simulations

The utilization of renewable energy sources and the development of energy storage technologies have enhanced the interconversion of various energy sources to slow down global warming. The building sector, as the main bearer of energy consumption, is essential for its energy saving and emission reduction. Integrating natural gas-based combined cooling, heating, and power systems with renewable energy generation facilities is an effective solution. For that, different scenarios are designed to provide energy for a specific office building and compared with the current scenario of depending only on the municipal grid. Equipment models for photovoltaic, battery, gas engine, absorption chiller-heater, and electric heat pump are created. The results show that the multi-energy complementary system has better economic and environmental characteristics, with a primary energy ratio of over 80 % and emission reduction of over 17 %; the advantages of configuring the unit capacity to meet the cooling and heating loads for 80 % of the year are obvious, and in this scenario abandoning battery storage has higher economics for users, with a static payback period from 7.3 years to 4.4 years, but the primary energy ratio decreased by 3 % and carbon emissions increased by 7.2 tCO2. It is recommended to consider the principle of gas-electricity complementarity, relying on the combined cooling, heating, and power system to meet part of the loads, with the remaining loads being supplemented by the municipal grid. The installation of batteries should be considered comprehensively based on the price of the batteries and the requirement for energy-saving and emission-reduction.

Optimal Operation Scheduling of Multi-energy Complementary Systems Including Offshore Wind Power

Background: With the rapid development of offshore wind power in China, offshore wind power is accounting for an increasing proportion of the whole installed power generation in China, which put forward higher requirements for operation scheduling of multi-energy complementary systems including offshore wind power. However, existing studies have paid little attention to the complementary output scheduling of multi-energy systems with a high proportion of offshore wind power, this phenomenon is not conducive to the realization of reasonable operation scheduling. Objective: To realize the reasonable operation scheduling of multi-energy systems with a high proportion of offshore wind power. Methods: Firstly, the output characteristics of offshore wind power were analyzed and summarized, and modeling was conducted from the perspectives of time distribution, spatial correlation, volatility and randomness, which would serve as the theoretical basis for subsequent researches. Secondly, the complementary rule among offshore wind power and the multi-energy system was analyzed, and the complementary characteristic index was put forward. Then the safety operation was taken as the constraint, and the two-stage operation model of the integrated energy system was established, which considers the auxiliary service costs. In the first stage, the initial generation scheduling was developed according to the day-ahead forecast values of the offshore wind power; in the second stage, the more accurate intra-day operation scheduling was further achieved by considering the intra-day forecast values of offshore wind power and the day-ahead scheduling results. Costs of rotating reserve capacity could be reduced by correcting the deviation of generating capacity, then the revenue-maximizing scheduling strategies were obtained and the output of the pumped-storage power plants was optimized. Results: The effectiveness of the model proposed in this paper was verified based on the simulation examples. Compared with the traditional scheduling strategy, the scheduling strategy considering auxiliary service cost proposed in this paper can promote the consumption of offshore wind power, reduce the wind curtailment proportion and improve the electricity sales revenues in the end. Conclusion: The research results in this paper provide a reference for the reasonable consumption of multi-energy complementary systems with a high proportion of offshore wind power and improving electricity sales revenues

A review on research and application of multi-energy complementary system containing high proportion of renewable energy based on different attributes

To better understand the latest development of renewable energy systems, recent studies on multi-energy complementary power systems with a high proportion of renewable energy are reviewed in this paper. The connection modes of power grids and economic system analysis are summarized and discussed respectively, putting forward some suggestions on the system design and operation optimization. Firstly, the characteristics and differences between an integrated system and an off-grid system are reviewed, concluding that an integrated system is more reliable and costeffective based on a few case studies. Secondly, the commonly used economic parameters and cost evaluation methods of the hybrid power system are reviewed. Those methods offer crucial tools to optimize the system, and they are able to analyze the system feasibility, enabling the most economical configuration. The results of several cases prove that the hybrid multi-energy system is more economical than the single-energy system. Finally, there are few articles focusing on technical details assessments and environmental impacts, which leaves room for future study.

Multi-Scheme Optimal Operation of Pumped Storage Wind–Solar–Thermal Generation System Based on Tolerable Energy Abandonment

In multi-energy complementary power generation systems, the complete consumption of wind and photovoltaic resources often requires more costs, and tolerable energy abandonment can bring about the more reasonable optimization of operation schemes. This paper presents a scheduling model for a combined power generation system that incorporates pumped storage, wind, solar, and fire energy sources. Through a comparison of schemes, the energy regulation function of the pumped storage power station was verified and analyzed. The CPLEX solver and MOPSO algorithm were employed to solve the daily output of a pumped storage power station in the Gansu region under various scenarios. The incorporation of pumped storage power plants has the potential to provide many benefits, including a reduction in operating expenses by about CNY 1.1163 million, a decrease in carbon emissions by 491.24 t, an enhancement in the stability of thermal power by 2.39%, and an improvement in the combined system capability to absorb additional energy. The correlation between the indicators of the combined system and the penetration rate of renewable energy is non-linearly influenced by changes in the power capacity configuration. Ultimately, the multi-objective optimization computation yields the ideal operational scheme for each power source, taking into account a tolerable energy abandonment mode.

Economy-environment-energy performance evaluation of power to hydrogen and power to methane considering renewable energy generation and carbon capture

Abstract The integration of multienergy complementary systems has become increasingly prevalent to mitigate the waste of renewable energy. As power-to-gas (P2G) technology advances, converting electricity into gas presents a viable solution for bolstering the reliability of power supplies within integrated energy frameworks. P2G plays a pivotal role in harnessing unused renewable resources, such as wind and solar energy, to produce sustainable power. While numerous studies have explored the advancement of P2G, there remains a lack of comprehensive evaluation of its various component subsystems. This research aims to design a renewable energy power system, augmented by gas-fired generation, assessing the collective advantages of both the power-to-hydrogen (P-H) and power-to-methane (P-M) conversion processes within the P2G infrastructure. It is important to note that the economic potential of P-H conversion is currently constrained by cost factors within existing P2G systems. This study takes into account the dynamics of carbon trading, as well as the hydrogen and methane markets, to compare the economic, environmental and energy-specific benefits of P-H and P-M conversions under different power demand scenarios. The goal is to formulate enhanced strategies to optimize P2G deployment in these varied contexts.

Performance analysis of the comprehensive energy system based on active energy storage-discharge technology under time-sharing electricity price operation strategy

Multi-energy complementary comprehensive energy systems based on renewable energy can reliably meet the energy needs of communities and significantly mitigate carbon emissions. This is of paramount significance in the establishment of low-carbon sustainable communities. The effective operation of an integrated energy system necessitates a thorough examination of demand-side load, the dynamic performance of the energy supply system, the configuration of energy storage systems, local electricity pricing policies, and operational or control strategies for the system. It confronts substantial challenges in practical application. Considering the noteworthy performance variations of comprehensive energy systems under diverse demand-side load, fluctuating electricity prices, and various operating modes of energy storage equipment, this paper initially conducts a practical analysis of demand-side load. A comprehensive energy system with multi-energy complementary based on source-load-storage coordination (SLS-CES) model was constructed. From the perspective of system operation strategy, we identify the current electricity consumption pattern in the region, characterized by peak and valley periods. We integrate this information with the time-of-use electricity pricing policy and the equipment within the target area. An operation strategy based on local time-of-use electricity price policy was proposed. An in-depth analysis of the thermal performance, environmental performance, and economic performance of the system in the full-year dimension and typical daily dimension under this operating strategy was conducted. The results show that under this operation strategy, the system's annual net income is 415.90 thousand yuan, of which the system's energy storage battery power supply revenue during peak period reaches 254.40 thousand yuan. The initial investment is 5.03 million yuan, and the static investment payback period is 12.09 years. The annual primary energy saving rate of the system is 36.00%, and the maximum CO2 emission reduction rate is 72.23%. The maximum primary energy saving rates on typical days in winter and typical days in summer are 74.74% and 97.14% respectively. The total annual CO2 emissions were reduced by 5.47 tons and 4.54 tons respectively. Through this study, we found that a system incorporating energy storage equipment, combined with an operation strategy based on electricity price policy, can yield additional economic benefits. This approach helps alleviate peak power supply pressure on the grid and mitigates the challenges associated with the high initial investment in renewable energy systems, all while maintaining good thermal performance and environmental benefits.

A Multi-Objective Optimization Method of Sustainable Wind–Photovoltaic–Hydro Systems Considering Source–Grid Coordination

Hydropower compensating for wind and solar power is an efficient approach to overcoming challenges in the integration of sustainable energy. Our study proposes a multi-objective scheduling model for the complementary operation of wind–photovoltaic–hydro systems. The model aims to maximize the total generation while minimizing the mean square deviation of the system output and grid load. Taking wind and solar bases and key peak-shaving cascade hydropower stations in Hubei Province as a case study, various multi-objective Pareto solution sets were obtained for different scheduling periods. The analysis dissects the relationship between total generation and the stability of residual load after adjustment by the wind–photovoltaic–hydro systems. Furthermore, the study analyzes the role that a complementary system should play in the power grid and discusses the effect of cascade hydropower scheduling methods on the operational characteristics of multi-energy complementary systems.

Real-time operational optimization for flexible multi-energy complementary integrated energy systems

Multi-energy complementary integrated energy system (MCIES) has gained widespread attentions due to its utilization of diverse energy sources, enhancing energy efficiency, and reducing carbon emissions. The scheduling optimization of MCIESs needs to address multiple factors, including solar/wind energy potential, fluctuating load demand, and prediction errors, to maintain its highly flexible and decarbonized operation. This study presents a scheduling optimization model based on a mixed integer nonlinear programming model (MINLP) with a novel flexibility index as the objective function. A case study of a MCIES in a swimming pool in Changsha is provided. The results demonstrate that real-time operational scheduling considering flexibility enhances the system flexibility of the MCIESs from 0.608 to 0.623 comparing with the day-ahead scheduling, maintaining superior performance across multiple dimensions. The coupling between the power grid and the natural gas network is also improved, significantly reducing the carbon dioxide emissions of the MCIES by 127.67kgCO2 per day. Furthermore, the study reveals that the flexibility-aware real-time operational scheduling for MCIES outperforms day-ahead scheduling in responding to weather and equipment failures, sustaining high flexibility operation, economic viability, and notably improved environmental performance. CO2 emissions are reduced by 21.088% and 14.638%, respectively. The proposed operational optimization approach in this study can enhance the flexibility and coordinated operation of MCIESs, leading to reduced carbon emissions.

Research on optimal configuration of park-level multi-energy complementary system with multiple evaluation indexes

At present, energy shortages are becoming increasingly severe, and the concept of park level multi energy complementary systems (MECS) has provided direction for sustainable energy development. In recent years, how to improve the economy and reliability of multi energy complementary systems has become a research hotspot in this field. In this paper, a two-layer optimal scheduling strategy is proposed to allocate the capacity of various energy equipment in the park, considering the comprehensive energy self-sufficiency rate, comprehensive energy utilization rate and energy shortage expectation. The proposed capacity allocation scheme can effectively improve the economy of MECS in the park. Finally, the effectiveness and practicability of the algorithm are verified by simulation analysis.

Technical and economic analysis of multi-energy complementary systems for net-zero energy consumption combining wind, solar, hydrogen, geothermal, and storage energy

An integrated renewable energy supply system is designed and proposed to effectively address high building energy consumption in Zhengzhou, China. This system effectively provides cold, heat, and electricity by incorporating various clean energy sources such as wind, solar, hydrogen, and geothermal energy. Technical and economic analyses are conducted to optimize the integration of these renewable sources. Technical and economic analyses are conducted to optimize the integration of these renewable sources. Rigorous system modeling and dynamic simulation using TRNSYS software evaluate the seamless integration and optimal functioning of the PV/T subsystem within the CCHP system. The interaction between Photovoltaic/Thermal (PV/T) and borehole heat exchanger (BHE) coupling is investigated, analyzing their impact on individual system performance. Furthermore, key indicators, including overall electricity consumption (OEC), life cycle cost (LCC), heat pump coefficient of performance (COPHP), and system coefficient of performance (COPSYS) are analyzed. The robust response surface methodology (RSM) and Box-Behnken experimental design approach are employed to show remarkable agreement between predicted and simulated values, with a maximum deviation of only 1.45%. The optimal configuration consists of a PV/T area of 132 m2, 20 wind turbines, 12 alkaline fuel cells, and 17 borehole heat exchangers, resulting in highly favorable outcomes: an OEC of −35648.72 kW∙h/year, an LCC of $209113.85, a COPSYS of 2.91, and a COPHP of 3.82. Moreover, detailed assessments of each subsystem's performance enhances our understanding of the system's overall operation, affirming the feasibility of the proposed integrated energy supply system for buildings.

Optimization Configuration of Distributed Multi-Energy Complementary Energy Systems

This paper points out the uncertainty of existing optimization models due to factors such as environmental and equipment output, which have a significant impact on the accuracy and rationality of system planning. Therefore, this paper establishes a full-working-condition-mathematical model for distributed multi-energy complementary energy systems and constructs an optimization configuration mathematical model with the total annual cost of the system as the optimization objective. Subsequently, an energy supply equipment optimization configuration method for distributed multi-energy complementary energy systems is proposed. Finally, the effectiveness of the proposed optimization configuration method is verified through case studies. This research will have important guiding significance for the construction and operation of distributed multi-energy complementary energy systems.

Multi-criteria optimization of multi-energy complementary systems considering reliability, economic and environmental effects

Economic and environmental benefits of multi-energy complementary systems (MECSs) have become favorite topics. However, intermittent renewable energy and demand, as well as breakdown, may cause a failure of expected benefits or even supply shortages. This paper proposed an optimization method for MECSs that comprehensively considers reliability, economic and environmental performances. Markov Chain Monte Carlo (MCMC) method was adopted for reliability assessment. The multi-criteria optimization problem was solved using the Non-dominated Sorting Genetic Algorithm-II (NSGA-II) and a decision-making method (TOPSIS). An actual indoor heated swimming pool with a MECS was conducted as a case study. Furthermore, the influences of scheduling strategy and power grid penetration (PGP) on MECSs were investigated. Compared with the case without considering reliability, the proposed optimization method exhibits more holistic performance, in terms of nearly 10 times lower expected energy supply shortage time (EESST) at the expense of 13.08% higher annual total cost (ATC) and 15.15% lower environmental performance coefficient (EPC). Additionally, the scheduling strategy greatly affects the performances, and a proposed scheduling strategy achieves 7.26% lower ATC, 7.69% higher EPC and about 40 times lower EESST. This study also reveals the necessity to focus on PGP as it significantly influences the strategy selection.

Optimal capacity allocation of wind-light-water multi-energy complementary capacity based on improved multi-objective optimization algorithm

As a basic industry for national economic development, the power industry is closely related to the overall economic and environmental development of China. At present, China is still dominated by thermal power generation. In order to reduce carbon emissions, promote the realization of the “double carbon” goal, and improve the level of clean energy utilization and the operating efficiency of the power system, a wind-light-water storage complementary power generation system is built, and a mathematical model of multi energy complementation is established. The minimum economic cost and the minimum battery capacity are proposed as the objective functions of system capacity configuration. Then a multi-objective evolutionary algorithm based on Pareto optimal space of the NDWA-GA and the PCA is proposed for optimal capacity allocation of multi energy complementary systems in this paper. Compared with the traditional multi-objective optimization algorithm, the correctness and effectiveness of the proposed method are verified. In addition, according to the actual research object, the optimal capacity configuration of the multi energy complementary system is given, which can guide the production and has an important promotion significance for energy saving and emission reduction.

A multi-objective planning method for multi-energy complementary distributed energy system: Tackling thermal integration and process synergy

This study proposes a multi-objective optimization methodology for planning multi-energy complementary distributed energy systems considering process synergy and thermal integration. The process integration technique is integrated into the Energy Hub model to deal with the multi-process synergy and temporal source-load matching. The system design and dispatch strategy are optimized by an augmented ε-constraint method with three objectives (economics, carbon emission, and fossil fuel consumption), and then the optimal tradeoff solution is identified by the Technique for Order Preference by Similarity to an Ideal Solution. Moreover, a novel multi-energy complementary distributed energy system is developed, which includes comprehensive utilization of solar energy (photovoltaic, photothermal, and thermochemical) and middle-low temperature heat utilization technologies, as well as hybrid energy storage technologies. Finally, a case study located in Beijing is selected as an illustrated example. The obtained single-objective optimization solutions and Pareto optimal solutions are further analyzed and compared in terms of system configuration, hourly/yearly energy balance, and thermal integration condition. The results show that the multi-energy complementary distributed energy system presents an economic benefit (reducing 25% of the annual total cost) compared to a gas turbine-based integrated energy system. Considering thermal integration contributes to 5.13% of the cost reduction. The configuration of the energy storage devices will reduce 18% energy supply cost, 9% fossil fuel consumption, and 42% carbon emission with the storage devices' boundary increase from 2 MWh to 60 MWh. Moreover, the optimal design of the system provides a reference for decision-making and a basis for flexible operation. The annual total cost, carbon emission, and fossil fuel consumption of the optimal solution in the Pareto frontier are 8.19 million CNY, 2.91 kt CO2-eq./year, and 18.4 GWh, respectively.

Energy storage capacity configuration in multi-energy complementary systems

To solve the problems of high peak shaving pressure, low energy utilization rate and poor economy of the multi-energy complementary system caused by the integration of wind and solar power into the grid, the research builds a two-layer optimization model of energy storage and routine power peak shaving based on the predicted output and load of wind and solar power on a typical day. The outer layer aims at the maximum annual net profit of the muit energy complementary system, and the inner layer aims at the lowest daily operating cost. The improved PSO and nonlinear programming are used to coordinate and solve the problem to determine the multi-energy complementary system’s intra-day peak-shaving scheduling method, which is reasonable and reasonable. Finally, an example of an actual power grid is analyzed, and the results show that the multi-energy complementary system after optimal configuration of energy storage can greatly raise the level of new energy consumption and has good economy.

Optimization and Performance Analysis of Francis Turbine Runner Based on Super-Transfer Approximate Method under Multi-Energy Complementary Conditions

Hydropower unit is the compensation power generation of the energy regulating unit in wind–solar–water multi-energy complementary systems that often require the turbine to operate in a partial working condition area, thereby resulting in problems of low hydraulic efficiency and severe vibration during operation. A multi-objective and multi-condition optimization design method for Francis turbine runner based on the super-transfer approximation approach was proposed in this study. The proposed method aims to improve the hydraulic performance of the turbine, enhance and suppress the vibration of the turbine, and expand the operation range of the turbine on the basis of the actual situation given that Francis turbine frequently operates in low- and ultralow-load areas under the condition of multi-energy complementarity and continuous adjustment of operating conditions. Different operating conditions from low load to full load were selected as performance evaluation conditions. The super-transfer approximation method was used to select the weight co-efficient of water turbine operating conditions, and a multi-objective optimization function with the efficiency and cavitation performance of the water turbine as optimization objectives was constructed to ensure that the optimized water turbine can achieve the optimal performance in the full working condition range. Results showed that the pressure distribution on the blade surface of the optimized runner was uniform and the working ability was enhanced under the condition of ensuring the performance stability of optimal and rated conditions when the original runner was optimized. The hydraulic efficiency of the turbine under the low-load conditions OP1 and OP2 increased by 4.61 and 3.17%, respectively. Hence, the optimized runner is suitable for hydraulic turbines under multi-energy complementary conditions. The results of this study can provide a reference for the optimal design and operation of the turbine runner.

Multi-objective optimization of multi-energy complementary integrated energy systems considering load prediction and renewable energy production uncertainties

Multi-energy complementary integrated energy system (MCIES) is considered as a promising solution to mitigate carbon emissions and promote carbon peaking and carbon neutrality. Currently, the capacities of a MCIES are sized according to the deterministic load and parameters of the system model. However, uncertainty may lead to the failure to achieve the desired performance and affect the sizing of the MCIES. This study explored an optimization model for the proper sizing of the MCIES considering uncertainties to achieve the best economic, environmental and thermal comfort benefits. The non-dominated sorting genetic algorithm-II (NSGA-II) combined with a technique for order preference by similarity to an ideal solution (TOPSIS) and Shannon entropy method were adopted to solve the optimization. Case studies, an actual swimming pool building with MCIES, as the prototype, were used to illustrate the procedure. Moreover, the effects of uncertainty degree and scenario setting were investigated. The results show the benefits of the proposed approach against the traditional deterministic optimization method for comprehensive consideration of economy, environment and thermal comfort. It also suggests that uncertainty and scenario setting should be carefully and properly considered during the design stage, as they have a significant impact on the results of sizing.

Feasibility study on the construction of multi-energy complementary systems in rural areas—Eastern, central, and western parts of China are taken as examples

In this study, the feasibility of constructing multi-energy complementary systems in rural areas of China is examined. First, the rural energy structure and energy utilization in the eastern, central, and western regions of China are analyzed, and the development and utilization modes of multi-energy complementary systems in different regions are evaluated based on the differences in the resource endowment in different regions. Second, the input-output status of the multi-energy complementary mode in different regions is analyzed. Then, based on the assumption of technical feasibility, the feasibility of the multi-energy complementary system is analyzed in terms of various dimensions, such as economic, energy conservation, environmental protection, and social benefit. Finally, an empirical study is conducted by comparing the proposed multi-energy complementary system with traditional energy supply system. The results show that the development of a multi-energy complementary system in each region is feasible from the perspective of multiple dimensions to reduce environmental pollution, create employment opportunities, and improve the economy. Moreover, the system can significantly reduce the peak-valley difference and improve energy efficiency.