Coal-fired Units Research Articles

Cost Analysis of the Boiler Unit of Coal Power Units Depending on the Initial Steam Pressure and the Availability оf Flue Gas Purification Systems

When designing power plants of a new type or equipping them with new generation equipment, the problem of estimating capital investments is solved with the uncertainty of information on its cost. The lack of reliable methods suitable for use in engineering setting complicates decision-making on the technical development of power units and thermal power plants. When evaluating investments in the equipment of power plant units, it is convenient to use continuous functions. Their use makes it possible to carry out the analysis without cost restrictions. The article proposes a method for estimating capital investments in the boiler island of power units of power plants based on a power parametric function. The method includes an assessment of the cost of a boiler unit with fuel preparation systems within the boiler shop, draught and blast. A specific feature of the method is that the cost of the boiler includes the cost of flue gas purification systems from harmful combustion products in the form of ash, sulfur oxides and nitrogen oxides. The method was developed in an engineering setting. The methodological section demonstrates the performance of the method in assessing capital investments in a boiler island in comparison with the same indicator for the EU countries, the USA and China. When discussing the results of the study, it was found that capital investments in a coal-fired boiler with flue gas purification systems is in the range of US$ 25–200 million, depending on the power and initial steam parameters. The share of the cost of environmental flue gas purification systems is 28–50 % of the total cost of the boiler unit. It is demonstrated that the design of coal-fired power units with flue gas purification systems for supercritical parameters with a capacity of less than 300 MW is inefficient due to low competitiveness in terms of specific investments in the boiler.

Optimal Scheduling Framework of Integrated Energy System Based on Carbon Emission in Electricity Spot Market

Micro coal-fired units (MCFU) and combined heat and power plants (CHP) in integrated energy system (IES) will emit a large amount of carbon dioxide when providing loads to customers, which will lead to higher operating costs of IES. To solve this challenge, an optimal dispatch model of power-to-gas (P2G) and methane reactor (MR) considering the reward and punishment costs based on carbon emission trading mechanism is proposed, to reduce carbon emissions of IES and enhance the accommodation of renewable energy (RE). Subsequently, considering the uncertainty of RE, a combination optimization method for MCFU and CHP units is developed based on the Lagrange multiplier method. Finally, considering the mechanism of electricity spot market (ESM), a transaction strategy for IES participating in ESM is proposed to further enhance the accommodation of RE. The effectiveness of the proposed framework is demonstrated through simulations.

Design and analysis of a novel liquefied air energy storage system coupled with coal-fired power unit

With its large scale and high flexibility, liquefied air energy storage is very suitable for integrated operation with existing power generation systems to improve the regulation ability of the grid. A novel liquified air energy storage system coupled with coal-fired power unit for heat exchange through the water/steam and the compression/expansion air is proposed. The thermodynamic model of a novel liquified air energy storage system is established with a 307 MW coal-fired power unit as the coupling object. And the parameters design and performance analysis of the coupling system are carried out. The results show that the efficiency of the system can reach 51.64 %. At this time, the corresponding energy storage/release pressure is 18/7.2 MPa. The highest return on investment of the system can reach 19.59 %, and the shortest dynamic payback period can reach 4.73 years. The sensitivity analysis shows that decreasing the heat transfer end difference of the regenerator and increasing the adiabatic efficiency of the compressor are conducive to reducing the exergosy destruction of equipment and improving the efficiency of the system. It is beneficial to improve the economic performance of the system to increase the difference between peak and valley electricity prices and the amount of peak regulation subsidy.

Towards a low-carbon future for China’s power supply chain: Critical sectors identification and scenario analysis

The power sector is a significant contributor to global carbon emissions and has received widespread attention from scholars; however, the path to achieving supply chain-wide carbon reductions in China from a provincial perspective remains unclear. This study combined multi-regional input–output and betweenness-based methods to identify the critical upstream sectors that indirectly drive large amounts of carbon emissions through power supply chains. The point source data of coal-fired units were collected to ensure the accuracy of the disaggregated input–output table. In addition, a scenario analysis was conducted to examine the effects of different electricity policy combinations on supply chain-wide emissions during the 14th Five-Year Plan (FYP). Our findings indicate that the embodied carbon intensity of the coal-fired power sector in Northwest China is among the highest in the country, ranging from 36.39 to 82.10 tons/10000 CNY. Therefore, the shift of the power sector to Western China during the 14th FYP will partially offset the positive emission reduction effect of the structural transformation of the power system. To achieve a low-carbon power supply chain, it is necessary to improve the production efficiency of critical transmission sectors and the low-carbon technology levels of major emitting sectors. Our results provide valuable insights for provincial governments to plan low-carbon transformation paths for the power sector.

Thermodynamic analysis and operation strategy optimization of coupled molten salt energy storage system for coal-fired power plant

The growing use of renewable energy requires greater flexibility than existing thermal power units. A steam-extraction system was developed to adjust the power output during a low-load period. The incorporation of molten-salt energy storage enables the decoupling of the boiler from the turbine, thus enabling the regulation of the output power during low-load operation. And the impact of key parameters on the performance of coal-fired units is analyzed to find the suitable operation parameters for the existing coal-fired power plant. The performance parameters of the system are optimized by a multi-objective grey wolf optimization algorithm, which conducts trade-off optimization between roundtrip efficiency and exergy efficiency to identify the Pareto Front for a certain range of extracted steam mass flow rates, hot-tank temperatures, and split ratios. The typical operating conditions of the combined system were analyzed, and a peak capacity of 64.1 MW and a power change factor of 17.33 % were achieved. The discharging process reduced the heat consumption of the unit, while the peak capacity and heat consumption of the combined system were used as objective functions to optimize the charging process. The peak capacity, power enhancement rate, and net profits of the system improved 1.12, 1.42, and 1.27 times after optimization. Heat consumption and efficiency were reduced by 2.61 % and 3.96 %. The molten-salt thermal storage system achieved a synergistic improvement in the operational flexibility and thermal efficiency of the thermal power system.

An electricity-carbon joint market optimization model for coal-fired power system under China's “dual-carbon” target

In the process of low-carbon transformation of power system in China, providing enough flexible service from coal-fired power units (CFPUs) is one of the most crucial answers to reduce or even avoid the operation risk which is caused by large-scale expansion of variable renewable energy (VRE). To spur CFPUs release flexibility, this paper suggests a two-stage optimal model, taking into account various peaking compensation mechanisms (VPCM) in a day-ahead power and carbon emissions trade (CET) joint market. Pre-clearing is the first stage, which maximizes social welfare, and formal clearing is the second stage, which maximizes the profit of the coal-fired power system. In contrast to the existing fixed peaking compensation mechanism (FPCM), the variable and fixed costs associated with providing peaking regulation are calculated by the VPCM. In addition, the work considers the CET market as an external carbon emissions constraint and internal constraint and no constraint are set to study the effectiveness of the current CET market. The result indicates that the VPCM can adapt more successfully to the cost of CFPUs when providing peaking regulation and increase the profit of the coal-fired power system. Then, “VPCM + external carbon constraint” enables larger profits for coal-fired power systems, whereas “FPCM + internal carbon constraint” stimulates VRE integration and reduces carbon emissions. Finally, the current CET market mechanism is insufficient to support coal-fired power plants in reducing carbon emissions as VRE rises.

Depth investigation of the regulation mechanism of SiO2 on the denitrification performance and sulfur resistance of MnCe/Ti SCR catalyst

The “deep peaking” of coal-fired units presents great challenges for SCR catalysts’ de-NOx activity at wide temperatures. Mn-based catalysts have good de-NOx activity at low temperatures, but their poor sulfur resistance is one of the key issues affecting industrial applications. In this study, the effects of SiO2 doping on the denitrification, sulfur resistance, and physicochemical performance of the MnCe/Ti catalyst were investigated. The results showed that SiO2 improved the de-NOx activity of catalysts at high temperatures and enhanced SO2/H2O resistance at wide temperatures. Under short reaction time conditions, the MnCe/Ti0.9Si0.1 catalyst exhibited the highest NO conversion rate at 400 °C, which was 33% higher than that of the MnCe/Ti catalyst. The NO conversion rates of Si-doped MnCe/Ti catalysts increased rapidly to over 85% (65% of the MnCe/Ti catalyst) as the reaction temperature increased from 200 °C to 250 °C under SO2-containing atmosphere due to the promoting effects of SiO2 on the decomposition of ammonium bisulfate. MnCe/Ti0.7Si0.3 catalyst exhibited the optimal sulfur and H2O resistance, with NO conversion rate higher than 85% with 600 min under SO2/H2O-containing atmospheres. SiO2 inhibited the crystallization of anatase TiO2, and increased the specific surface area to 306.60 m2/g. Additionally, the ratios of Mn4+/Mnn+ and Ce3+/Cem+, and the surface adsorbed oxygen and weak-medium acid amount also increased due to the multiple interactions between the TiO2-SiO2 and Mn/Ce, resulting in the higher de-NOx activity. Compared with the MnCe/Ti catalyst, Si-doped MnCe/Ti catalysts have lower SO2(g) adsorption amount and the sulfation of Mn, and higher SO3(a) desorption performance, resulting in better sulfur resistance at wide temperatures.

A Flexibility-oriented robust transmission expansion planning approach under high renewable energy resource penetration

High penetrations of renewable energy sources incorporated into transmission systems pose a substantial challenge to transmission expansion planning operations due to both the strong uncertainty of these sources and their high variability. However, most current robust transmission expansion planning studies focus exclusively on the issue of uncertainty, and neglect to optimize system flexibility in an effort to cope with the high variability of these sources. The present work addresses this critical issue by proposing a flexibility-oriented robust transmission expansion planning method developed according to the unit commitment characteristics of coal-fired and gas-fired generation units that fully considers the short-term flexibility requirements of electric power systems while maintaining high robustness to the uncertainties of RES outputs in long-term transmission expansion planning problems. The proposed complex model with unit commitment constraints containing massive binary variables is solved by first reducing the number of binary variables via the application of clustering techniques to identify generator units with similar generation properties, and then decreasing the complexity of the model further by relaxing the integer variables in the unit-clustered model. Finally, we develop generalized column-and-constraint generation algorithms that can solve the clustered model and the relaxed simplified model with greatly enhanced efficiency. Comparisons of the numerical results obtained by the proposed approach with existing state-of-the-art methods when applied to a simple Garver 6-node system and a realistically-sized power system demonstrate that the proposed method produces optimal RTEP solutions that account for both the uncertainty and variability of RES outputs. Moreover, the total cost of the proposed approach is 2.22×106$ less than that of the other state-of-the-art methods considered, which is of great significance in guiding practical transmission expansion planning applications.

Study and management of flow and concentration field problems in 600 MW SCR unit

With the increasingly stringent national requirements for environmental protection, the control of pollutants in coal-fired power plants has been gradually strengthened. In order to meet the NOx emission standard, some coal-fired units achieve ultra-low emissions by excessive ammonia injection, which seriously affects the unit operation economy. This paper takes the SCR denitrification unit of a 600 MW coal-fired unit with a Π-type furnace in China as the research object and studies the distribution of flow and concentration fields inside the unit under a 60% load section by means of CFD numerical simulation. It points out the problems of flow and concentration fields at local locations under current operating conditions and proposes the rectification of the corresponding area of the inflow equipment and the idea of a zonal ammonia injection optimization method. It provides a certain reference value for the optimized management of the denitrification system of coal-fired units in the future.

Changes in the structure of the Polish energy mix in the transition period to ensure the safety and reliability of energy supplies

The share of renewable sources in energy production in Poland is increasing steadily, but the reliability of energy supplies is determined primarily by stable sources, i.e. the coal-fired power units now in operation. The paper compares the current energy mix of the Polish power generation system with other European countries, drawing attention to the dominant role of coal-fired sources in Poland. Recent-year changes in the structure of the energy system are presented, along with the changes planned to ensure reduction in carbon dioxide emissions. It is demonstrated that the planned changes in the energy mix will significantly deteriorate the level of reliability of energy supplies in subsequent years of transition. Variants are presented of necessary adjustments in the planned energy mix in the system, which will make it possible to meet the growing national demand for energy and ensure the required level of the energy system reliability. Several variants of the system expansion are considered, including gas-fired units, onshore and offshore wind farms, photovoltaic sources and a slower rate of decommissioning the coal-fired power units retrofitted with CO2 capture facilities. The most favourable solution for the system reconstruction is to increase the share of all the above-mentioned energy sources.

ПЕРСПЕКТИВИ ВПРОВАДЖЕННЯ МАЛИХ МОДУЛЬНИХ РЕАКТОРІВ В ЕНЕРГОСИСТЕМІ УКРАЇНИ

Ukraine's declared goals of sustainable, environmentally acceptable energy development, and reduction of greenhouse gas emissions in accordance with the Paris Agreement require the preferential development of nuclear and renewable energy. At the same time, in the conditions of the current shortage of maneuverable capacities, the increase of stochastic generation volumes from renewable energy sources in the power system and the decommissioning of maneuverable coal-fired power units in accordance with international environmental obligations determines the need to study the possibilities of implementing new nuclear power plant technologies in the IPS of Ukraine, which will be able to participate in daily maneuvering. The article provides an overview of the state of development and implementation of the first NPP projects with small modular reactors of the American companies NuScale Power and Holtec International. It is shown that the national nuclear legislation does not single out MMR as a separate group of nuclear installations and does not take into account their features, which makes it necessary to carry out a thorough professional comparative analysis of the current regulatory framework of Ukraine and other countries on this issue, based on the results of which a decision should be made regarding the need to develop special regulatory requirements for MMR and determine the scope of application of existing regulatory documents. The results of the calculations of the forecast structure of generating capacities of IPS of Ukraine for the period up to 2040 are given, which showed that the construction in Ukraine of 3 powerful advanced NPP power units and the introduction of 1.5 GW of the power units with MMR, which can be used in daily power change modes, with the using of 13 GW of the baseload existing nuclear power units while reducing the capacity of existing coal-fired power units to 5 GW with their reconstruction to meet the requirements of the National Emission Reduction Plan and the growing volume of renewable generation are able to ensure the power balance system and reduce pollutant emissions by at least 50% and greenhouse gases by up to 30%. Keywords: small modular reactor, technical standards, legal and regulatory framework, power system, operating mode.

Tracking Carbon Flows from Coal Mines to Electricity Users in China Using an Ensemble Model.

Accurately tracking carbon flows is crucial for preventing carbon leakage and allocating responsibility for reducing CO2eq emissions. In this study, we developed an ensemble model to effectively track carbon flows within China's power system. Our approach integrates coal quality tests, individual power plant datasets, a dynamic material-energy flow analysis model, and an extended version of an interconnected power grid model that incorporates transmission and distribution (T&D) losses. Our results not only provide accurate quantification of unit-based CO2eq emissions based on coal quality data but also enable the assessment of emissions attributed to T&D losses and emission shifts resulting from interprovincial coal and electricity trade. Remarkably, for CO2eq emissions from coal-fired units, the disparity between the guideline and our study can be as high as [-95%, 287%]. We identify Guangdong, Hebei, Jiangsu, and Zhejiang provinces as the major importers of both coal and electricity, responsible for transferring nearly half of their user-based emissions to coal and power bases. Significantly, T&D losses, often overlooked, contribute to 15-20% of provincial emissions at the user side. Our findings emphasize the necessity of up-to-date life cycle emissions and spatial carbon shifts in effectively allocating emission reduction responsibilities from the national level to provinces.

Comparative study on flexibility enhancement of combined heat and power for wind power accommodation

Flexibility enhancement of coal-fired combined heat and power units is an essential approach for improving the wind power accommodation and a significant low-carbon way to achieve clean urban heating. To consume excess wind power, this paper proposed a novel combined heat and power system integrated with the various flexible technologies. The EBSILON software was applied for modeling the proposed thermal systems and analyzing the thermal performance under different operating conditions. On this basis, the mechanism of their heating compensation and wind power consumption was revealed and the indicator, the heating compensation capacity, was presented considering from both peak shaving and coal-savings perspectives. Compared with the conventional system, the wind power accommodation rate of the novel system had a maximum increment of 31.7% and the standard coal consumption had a maximum reduction of 14.3%. Meanwhile, by adding dynamic payback period and internal rate of return, the techno-economic performances were more reasonable and precise. The results showed that the heating compensation capacities of absorption heat pumps, low-pressure cylinder of turbine removal and thermal energy storage with extracted steam from turbine are 0.29 t/MWh, 0.26 t/MWh, and 0.25 t/MWh, respectively, which are better than that of other technologies. The net annual revenue of thermal energy storage system could reach 3.87 M$, 0.57 and 0.37 M$ higher than that of low-pressure cylinder of turbine removal and absorption heat pumps, respectively. It can be concluded that thermal energy storage can be the best to balance the peak shaving demand and techno-economic performance. In all, the proposed systems provided a promising method for the flexibilization of coal-fired combined heat and power units alongside new renewable systems.

Daily rolling estimation of carbon emission cost of coal-fired units considering long-cycle interactive operation simulation of carbon-electricity market

The high overlap of participants in the carbon emissions trading and electricity markets couples the operations of the two markets. The carbon emission cost (CEC) of coal-fired units becomes part of the power generation cost through market coupling. The accuracy of CEC calculation affects the clearing capacity of coal-fired units in the electric power market. Study of carbon–electricity market interaction and CEC calculations is still in its initial stages. This study analyzes the impact of carbon emissions trading and compliance on the operation of the electric power market and defines the cost transmission mode between the carbon emissions trading and electric power markets. A long-period interactive operation simulation mechanism for the carbon–electricity market is established, and operation and trading models of the carbon emissions trading market and electric power market are established. A daily rolling estimation method for the CEC of coal- fired units is proposed, along with the CEC per unit electric quantity of the coal-fired units. The feasibility and effectiveness of the proposed method are verified through an example simulation, and the factors influencing the CEC are analyzed.

Impact of adaptive water-saving and phaseout strategies on water withdrawal in China's coal-fired power industry under carbon constraints

Coal-fired power generation occupies a dominant position in China's power sector and is known for its high water requirement. Limited research exists on how water withdrawal for coal-fired power generation responds to policy and technical factors, as well as spatial variations in the future. To address this gap, this study utilizes a geospatial dataset at the coal-fired power unit level and an improved calculation method for water withdrawal to investigate the evolving trend of water withdrawal in coal-fired power generation, considering the influences of carbon emission reduction, adaptive water-saving measures, and phaseout strategies. The results demonstrate that the improved water withdrawal calculation method yields superior simulation outcomes compared to existing approaches. The study reveals substantial variations in coal-fired power generation under different carbon emission reduction scenarios. Despite the business-as-usual (BAU) scenario where coal-fired power generation continues to dominate the power sector, implementing various adaptive water-saving scenarios results in national water withdrawal estimates ranging from 42.9 to 59.4 billion m3 in 2050. In contrast, water withdrawal is reduced by 37.6% to 42.9% under the 2.0℃ target scenario and by 86.5% to 97.5% under the 1.5℃ target scenario. Technological advancements play a crucial role in reducing water withdrawal for coal-fired power generation, particularly in northwest China. The transformation of cooling systems significantly decreases water withdrawal nationwide and in the regions that predominantly relied on once-through cooling. The deployment of carbon capture and storage (CCS) technology in coal-fired power plants in the northwest region creates short-term pressure on regional water resources. Under strict carbon emissions constraints, adopting the phaseout strategy with guaranteed lifetime results in relatively higher water withdrawal for coal-fired power generation, and the variations in coal-fired power plants configuration across provinces lead to different responses in water withdrawal changes when facing the same unit retirement strategy.

Storage Optimization (r, Q) Strategy under Condition-Based Maintenance of Key Equipment of Coal-Fired Power Units in Carbon Neutrality Era

For the safe, stable, and economic operation of thermal power units in new power systems, the condition-based maintenance mode and storage strategy of key equipment and materials for power generation enterprises were selected. According to the storage linkage demand of condition-based maintenance, a Weibull probability density function was used to calculate spare parts demand, and an intelligent storage optimization model with an availability constraint was established. The application cases of spare parts cost and availability of high-value key equipment and low-value key equipment of coal-fired thermal power units were analyzed, respectively, and the influence of different life spans and the number of covered units on the model were expounded. The results show that the cost of spare parts borne by a single unit is greatly reduced via the optimization of an intelligent inventory (r, Q) strategy on the premise that the availability of units is not less than 99.5%.

The impact of electricity-carbon market coupling on system marginal clearing price and power supply cost.

In this study, we assessed the impacts of the benchmark designs of emissions allowance allocation in China's national carbon emissions trading system with plant-level data and further estimated the marginal clearing price and power supply cost in Guangdong power market under electricity-carbon market coupling with unit commitment and economic dispatch model. We find that the existing allowances benchmark would result in a considerable surplus of allowances at about 222 Mt. But the benchmarking and exemplary levels on the heat rate of power supply would motivate thermal power units to reduce CO2 emissions. Under a tight balance of supply and demand in Guangdong, peaking thermal power plants will become the marginal clearing units and higher clearing prices will add to the revenue of lower cost inframarginal renewable energy power units. However, the combined impact of electricity-carbon market coupling would cause the marginal clearing price fluctuates obviously from 0 to 1159 CNY/MWh. Compared to the baseline scenario with free CO2 allowances allocation, the efficiency of thermal power utilization would decrease by 23%-59% and the net revenue per MWh power supply of coal-fired power units would decrease by 275%-325% under the stress scenario. Our study suggests that setting a more stringent allowances allocation benchmark for carbon price discovery is necessary. As electricity-carbon market coupling changes the role of coal-fired power plants to provide flexibility service and decrease their revenues, it calls for further market designs on proper reimbursement of flexible resources, under which the electricity market can effectively achieve the synergy among accommodating new energy, ensuring resource adequacy, and delivering cost efficiency. In addition, the synergy can be enhanced by formulating a tax program, which can promote renewable energy investment.

Revisiting Market Power in the Polish Power System

The consequences of the liberalisation of electricity markets have been widely discussed in the literature emphasising the successes or failures of privatisation and deregulation. While most developed power systems have undergone a form of economic transformation, they still require to be monitored and analysed to assess market power. The Polish power system is an example wherein the potential of market power examined fifteen years ago was summarised as significant. Since then, the transformation process and changes in the ownership structure have taken place. This study focuses on the assessment of the potential of market power in the Polish electricity market. For this purpose, statistics on power companies were collected and processed. Then, structural and behavioural measures were applied, including concentration ratios, the entropy coefficient, the Gini coefficient, the Herfindahl–Hirschman Index (HHI), the Residual Supply Index (RSI), and the Lerner Index. The results reveal that, despite a dynamic increase in renewable capacity, market concentration has increased in recent years, achieving an HHI of 2020.9 in 2021. An increase in the Lerner Index of lignite and hard coal-fired units is also observed, indicating high mark-ups by the key market players. Based on quantitative analysis, policy recommendations are outlined to reduce the negative impact of market power on consumers.

Why coal-fired power plants should get nuclear-ready

Nuclear power plant designs are becoming smaller so that the capacity of these small modular reactors (SMRs) is similar to that of coal-fired power units. The need to decarbonize the energy sector will leave infrastructure and workers of retired coal-fired power plants behind. From an environmental point of view coal-fired power plants should neither be built nor operated. If these plants are built/operated though, they should be designed in a way that they can be swiftly transformed to provide low-carbon energy. They should be designed to be nuclear-ready. The idea to transform coal-to-nuclear (C2N) is receiving increased attention. In this Perspective, we argue that akin to an earlier EU directive on carbon capture and storage (CCS) that made CCS readiness assessments necessary to obtain a building permit in the EU, C2N assessments could be provided by utilities of new and operating coal-fired power plants on a voluntary basis today, to maximize the utilization of existing infrastructure for clean energy production tomorrow.

Off-design characteristics of a novel integrated system of coal-fired cogeneration unit and compressed air energy storage

The regulation range of heat-power ratio in conventional coal-fired cogeneration unit of heat and power (CHP) is limited, which makes the previous determination of electricity by heat can't meet both the heat and power load, and results in relatively low efficiency. In this paper, a new integrated system of coal-fired CHP unit with compressed air energy storage (CAES) system is studied, which can greatly adjust the heat-power ratio. During heat enhanced period (increasing heat-power ratio), CAES stores electric energy and makes the compression heat supply to the users. During power enhanced (reducing heat-power ratio), CAES discharges energy and absorbs CHP extraction heat to use in CAES expander. As the regulation of heat-power ratio is a process of variable working conditions, a detailed off-design model of the integrated system is established. The influence of the key parameters on the system off-design characteristics is revealed. The research shows that the CAES air flow rate has a great impact on the integrated system's efficiency and heat-power ratio, while the CAES chamber pressure has the least impact on the integrated system's efficiency. Under different CAES air flow rates and air chamber pressures, the fuel ratio corresponding to the highest exergy efficiency in the two periods is the same, which is about 0.92. Finally, a case study is made on the data of an industry park, which shows that the integrated system can well follow the heat and power demand with relatively high efficiency.