Development of multifunctional energy systems (MESs)

By synthetically combining the utilization of different fuels and the co-production of alternative fuels and power, a multifunctional energy system (MES) can present more opportunities to achieve higher efficiency, lower investment, and less environmental impact as compared to traditional energy systems. The principle for the integration of MES is systematically illuminated from the perspective of chemical conversion, energy utilization, and pollutants control. According to system integration characteristics, the development of MES has been classified into three stages, namely, polygeneration systems, MESs combining different fossil fuels, and MESs combining fossil fuel and renewable energy. Three MESs with primary energy savings (PESs) of 14–18% are introduced, which illustrated the potential of MES technology. At the same time, the increment of investment cost had been indicated as the major possible barriers for development of MES technology. On the basis of a comparison with other technical routes, super-critical power plants, and IGCC technology, the role of the MES in the sustainable development of China has been established.     

Performance analysis of humid air turbine cycle with solar energy for methanol decomposition

According to the physical and chemical energy cascade utilization and concept of synthesis integration of variety cycle systems, a new humid air turbine (HAT) cycle with solar energy for methanol decomposition has been proposed in this paper. The solar energy is utilized for methanol decomposing as a heat source in the HAT cycle. The low energy level of solar energy is supposed to convert the high energy level of chemical energy through methanol absorption, realizing the combination of clean energy and normal chemical fuels as compared to the normal chemical recuperative cycle. As a result, the performance of normal chemical fuel thermal cycle can be improved to some extent. Though the energy level of decomposed syngas from methanol is decreased, the cascade utilization of methanol is upgraded. The energy level and exergy losses in the system are graphically displayed with the energy utilization diagrams (EUD). The results show that the cycle’s exergy efficiency is higher than that of the conventional HAT cycle by at least 5 percentage points under the same operating conditions. In addition, the cycle’s thermal efficiency, exergy efficiency and solar thermal efficiency respond to an optimal methanol conversion.     

以甲烷重整方式利用气化煤气显热的甲醇-电多联产系统

根据"温度对口,组分合适"的原则,提出了一种以甲烷重整来利用煤气显热的多联产系统,可用于煤/天然气、煤/焦炉煤气双燃料系统.该系统利用气化炉出口的高温煤气显热作为甲烷/水蒸汽重整的反应热,把煤气的热能转变为合成气的化学能进行回收,使天然气和焦炉煤气重整后的富氢气体与富碳的气化煤气可按化工生产要求灵活调配.计算结果表明,相比于单产系统,双燃料系统效率最少可提高约1.5%.     

Solar thermal power cycle with integration of methanol decomposition and middle-temperature solar thermal energy

In this paper, we have proposed a new solar thermal power cycle which integrates methanol decomposition and middle-temperature solar thermal energy, and investigated its features based on the principle of the cascade utilization of chemical exergy. Also, the methanol decomposition with a catalyst was experimentally studied at temperatures of 150–300 °C and under atmospheric pressure. The chemical energy released by methanol fuel in this cycle consisted of two successive processes: solar energy drives the thermal decomposition of methanol in a solar receiver-reactor, and the syngas of resulting products is combusted with air, namely, indirect combustion after methanol decomposition. As a result, the net solar-to-electric efficiency of the proposed cycle could be 35% at the collector temperature of 220 °C and the turbine inlet temperature of 1300 °C, and the exergy loss in the indirect combustion of methanol was about 7% points lower than that in the direct combustion of methanol. The promising results obtained in this study indicated that this new solar thermal power cycle could make significant improvements both in the efficient use of the chemical energy of clean synthetic fuel and in the middle-temperature solar thermal energy in a power system.     

A novel combined cycle with synthetic utilization of coal and natural gas

 In this paper, a novel combined cycle with synthetic utilization of coal and natural gas is proposed, in which the burning of coal provides thermal energy to the methane/steam reforming reaction. The syngas fuel, generated by the reforming reaction, is directly provided to the gas turbine as fuel. The reforming process with coal firing has been investigated based on the concept of energy level, and the equations has been derived to disclosing the mechanism of the cascade utilization of chemical energy of natural gas and coal in the reforming process with coal firing. Through the synthetic utilization of natural gas and coal, the exergy destruction of the combustion of syngas is decreased obviously compared with the direct combustion of natural gas and coal. As a result, the overall thermal efficiency of the new cycle reaches 52.9%, as energy supply by methane is about twice as much as these of coal. With the same consumption of natural gas and coal the new cycle can generate about 6% more power than the reference cycles (the combined cycle and the steam power plant). The promising results obtained here provide a new way to utilize natural gas and coal more efficiently and economically by synthetic utilization.     

Research,development and the prospect of combined cooling,heating, and power systems

The development of a combined cooling, heating, and power (CCHP) system in China is presented in this paper. The key scientific problems of a distributed energy system and the integration principles of a CCHP system are also pointed out. Moreover, two corresponding CCHP systems: one with the complementarities of fossil fuels energy and renewable energy, and the other integrated with desalination technology, are investigated. With special attention to thermal energy utilization, the integrating characteristics of these systems are likewise revealed, and the important role that the principle of cascade utilization of physical energy plays in system integration is identified. We have found that the energy-saving ratio of the integrated CCHP systems can be as high as 30%, and as such, the innovative CCHP systems suitable for China's sustainable development are also recommended.     

新颖的核能燃气轮机总能系统的开拓性研究

基于系统综合和能的梯级利用的思路对核能燃气轮机总能系统开拓研究的进展,包括三方面：（1）提出若干高温气冷堆核能联合循环发电新系统;（2）开拓出两种核能联合循环多联产新系统;（3）探索出几种核电站联合循环技术更新改造新途径等;建立了完整的系统特性模型进行了模拟分析,揭示了它们的热力学特性,概括了各种用途的核电燃气轮机总能系统新系统,新方案的性能与特点。     

A distributed energy system integrating SOFC-MGT with mid-and-low temperature solar thermochemical hydrogen fuel production

Solar thermochemical hydrogen production with energy level upgraded from solar thermal to chemical energy shows great potential. By integrating mid-and-low temperature solar thermochemistry and solid oxide fuel cells, in this paper, a new distributed energy system combining power, cooling, and heating is proposed and analyzed from thermodynamic, energy and exergy viewpoints. Different from the high temperature solar thermochemistry (above 1073.15 K), the mid-and-low temperature solar thermochemistry utilizes concentrated solar thermal (473.15–573.15 K) to drive methanol decomposition reaction, reducing irreversible heat collection loss. The produced hydrogen-rich fuel is converted into power through solid oxide fuel cells and micro gas turbines successively, realizing the cascaded utilization of fuel and solar energy. Numerical simulation is conducted to investigate the system thermodynamic performances under design and off-design conditions. Promising results reveal that solar-to-hydrogen and net solar-to-electricity efficiencies reach 66.26% and 40.93%, respectively. With the solar thermochemical conversion and hydrogen-rich fuel cascade utilization, the system exergy and overall energy efficiencies reach 59.76% and 80.74%, respectively. This research may provide a pathway for efficient hydrogen-rich fuel production and power generation.     

Decoupling optimization of integrated energy system based on energy quality character

Connections among multi-energy systems become increasingly closer with the extensive application of various energy equipment such as gas-fired power plants and electricity-driven gas compressor. Therefore, the integrated energy system has attracted much attention. This paper establishes a gas-electricity joint operation model, proposes a system evaluation index based on the energy quality character after considering the grade difference of the energy loss of the subsystem, and finds an optimal scheduling method for integrated energy systems. Besides, according to the typical load characteristics of commercial and residential users, the optimal scheduling analysis is applied to the integrated energy system composed of an IEEE 39 nodes power system and a 10 nodes natural gas system. The results prove the feasibility and effectiveness of the proposed method.     

Thermodynamic and economic assessment of a PEMFC-based micro-CCHP system integrated with geothermal-assisted methanol reforming

A micro-combined cooling heating and power (CCHP) system integrated with geothermal-assisted methanol reforming and incorporating a proton exchange membrane fuel cell (PEMFC) stack is presented. The novel CCHP system consists of a geothermal-based methanol steam reforming subsystem, PEMFC, micro gas turbine and lithium bromide (LiBr) absorption chiller. Geothermal energy is used as a heat source to drive methanol steam reforming to produce hydrogen. The unreacted methanol and hydrogen are efficiently utilized via the gas turbine and PEMFC to generate electricity, respectively. For thermodynamic and economic analysis, the effects of the thermodynamic parameters (geothermal temperature and molar ratio of water to methanol) and economic factors (such as methanol price, hydrogen price and service life) on the proposed system performance are investigated. The results indicate that the ExUF (exergy utilization factor the exergy utilization factor), TPES (trigeneration primary energy saving) and energy efficiency of the novel system can be reached at 8.8%, 47.24% and 66.3%, respectively; the levelized cost of energy is 0.0422 $/kWh, and the annual total cost saving ratio can be reached at 20.9%, compared with the conventional system. The novel system achieves thermodynamic and economic potential, and provides an alternative and promising way for efficiently utilizing abundant geothermal energy and methanol resources.     

IGCC多联产总能系统

从能源与环境领域渗透交叉层面、化学Yong梯级利用结合的角度综述IGCC多联产总能系统的研究动态；阐述了多联产系统概念与过程机理。分析了系统集成的关键技术及其应用与发展前景。     

A proposal for a novel multi-functional energy system for the production of hydrogen and power

A novel multi-functional energy system with two kinds of fuels (coal and natural gas) and two kinds of products (hydrogen and electricity) is proposed. The proposed system takes advantage of the complementary properties of coal and natural gas by integrating natural gas/steam reforming together with the combustion of coal. Coal is indirectly gasified by combustion so that the need for an air separation unit is eliminated. At the same time, a part of superior natural gas fuel, which is burnt in the reformer, is replaced with inferior coal fuel. Hence, energy utilization is improved effectively. In addition, the novel system is investigated by means of the EUD (energy-utilization diagram) methodology and then compared with the reference system, which is composed of four conventional systems. As a result, the thermal efficiency of the new system may be expected to reach 75%. Moreover, a comparison with the reference system shows that the proposed system provides a 10% energy savings. The promising result obtained here provides an attractive option for an effective utilization of coal and natural gas.     

串联型焦电联产系统的概念性设计与特性规律

根据能量的综合梯级利用原理,设计了串联型炼焦-发电联产系统.新系统缩小了燃料化学能释放侧与热能接受侧的品位差;尽量减少炼焦过程耗气量,把更多富氢的焦炉煤气提供给联合循环,以实现高效洁净发电;还变革传统的焦炉工艺流程,优化和整合燃气轮机和焦炉的排气系统,使得系统总排烟量和损失都降低.研究表明,新系统具有优良的热力特性,系统相对节能率高达23%.     

化工动力多联产系统设计优化理论与方法

化工动力联产备受关注,文章概述作者团队对多联产系统设计优化理论与方法的研究。从领域交叉层面探讨联产系统集成理论,阐明了能的综合梯级利用和控制CO2一体化原理;基于新原理,诠释了多联产系统类型和集成特征,凝练了系统集成的三个一般性原则思路和体现这些原则的优化整合途径和手段。然后,构建了相关的联产系统设计优化方法：基于相对节能率和基于化学能梯级利用机理的设计方法。实例研究验证了所提出理论与方法的有效性、实用性。     

Proposal of a natural gas-based polygeneration system for power and methanol production

A new kind of natural gas-based polygeneration system for methanol and power production is proposed in this paper. With the sequential connection between chemical production and power generation, the new system adopts innovative integration of partial-reforming and partial-recycle scheme in methanol synthesis subsystem. To reveal the characteristics of the new system, exegetic comparisons between the new system and a reference polygeneration system with full-reforming and once through methanol synthesis scheme have been carried out. Results indicate that the new system can save energy about 6 percentages versus single product systems. By the aid of graphical exergy analysis methodology, the specific information on internal phenomena of key processes was illustrated. The analysis shows that it is the synergetic combination of partial-reforming and partial-recycle schemes that makes the significant contribution to the performance improvement, and plays the most important role in system integration.     

应用天然气重整技术的新型动力系统开拓研究

总结概述应用天然气重整反应技术的新型动力系统开拓研究,包括燃料电池及联合循环系统、化学回热燃气轮机循环、太阳能一天然气互补动力系统以及天然气／煤双燃料综合动力系统等。分析归纳天然气蒸汽重整在动力系统应用的新方式,侧重论述天然气蒸汽重整在相关新系统集成中新应用的功能与机理,还分析揭示新系统的特性与性能。     

Thermodynamic performance study of the MR SOFC-HAT-CCHP system

Based on Aspen Plus, a methanol reforming Solid Oxide Fuel Cell - Humid Air Turbine - Combined cooling, heating and power (SOFC-HAT-CCHP) system based on solar methanol reforming is built in this paper, which combines (Solid Oxide Fuel Cell) SOFC with (Humid Air Turbine) HAT power generation system. This paper analyzes the performance of SOFC-HAT-CCHP system, and reveals the affinity of complementary utilization of solar energy and chemical energy. This paper optimizes the integrated design of the system and constructs a steady state model of the system's thermal calculation. The calculation results show that the total power efficiency of the method, the system total exergy efficiency and the thermal efficiency are 57.2%, 63.0% and 87.1% respectively. The results show that the introduction of HAT power generation system has increased the power generation and reduced the coal consumption rate. Compared with simple methanol reforming (Solid Oxide Fuel Cell - Gas Turbine - Combined cooling, heating and power) SOFC-GT-CCHP, the introduction of HAT effectively improves the total power generation efficiency of the system and increases 4.1% points. The exergy efficiency of increased by 4.6% points. Compared to the reference system, the standard coal consumption rate of electricity generated by the new system decreased by 16.6 g/kWh and the power generation increased by 15.5 g/kWh.     

Hybrid power generation system of solar energy and fuel cells

This paper introduces the methods of integration of solar energy and low‐temperature solid oxide fuel cells. On the one hand, we design the system that integrates the solar photovoltaic cells and fuel cells. On the other hand, solar energy is concentrated to heat up the fuel cell and supply the working temperature at hundreds Celsius degrees by Fresnel lens. Then the fuel conversion efficiency is increased because of gain from the solar energy. Moreover, integration of solar thermal energy power system with the fuel is a good method for resolving the instability of solar energy. CHP (combined heat and power) is another aspect to enhance the design hybrid system overall efficiency. Finally, we present a novel device but built on different scientific principle. It can convert solar energy and chemical energy of fuel to electric energy simultaneously within the same device to integrated solar cell and fuel cell from the device level. Copyright © 2016 John Wiley & Sons, Ltd.     

On capital utilization in the hydrogen economy: The quest to minimize idle capacity in renewables-rich energy systems

The hydrogen economy is currently experiencing a surge in attention, partly due to the possibility of absorbing variable renewable energy (VRE) production peaks through electrolysis. A fundamental challenge with this approach is low utilization rates of various parts of the integrated electricity-hydrogen system. To assess the importance of capacity utilization, this paper introduces a novel stylized numerical energy system model incorporating the major elements of electricity and hydrogen generation, transmission and storage, including both “green” hydrogen from electrolysis and “blue” hydrogen from natural gas reforming with CO₂ capture and storage (CCS). Concurrent optimization of all major system elements revealed that balancing VRE with electrolysis involves substantial additional costs beyond reduced electrolyzer capacity factors. Depending on the location of electrolyzers, greater capital expenditures are also required for hydrogen pipelines and storage infrastructure (to handle intermittent hydrogen production) or electricity transmission networks (to transmit VRE peaks to electrolyzers). Blue hydrogen scenarios face similar constraints. High VRE shares impose low utilization rates of CO₂ capture, transport and storage infrastructure for conventional CCS, and of hydrogen transmission and storage infrastructure for a novel process (gas switching reforming) that enables flexible power and hydrogen production. In conclusion, all major system elements must be considered to accurately reflect the costs of using hydrogen to integrate higher VRE shares.     

以燃气轮机为核心的多功能能源系统基本形式与构成

以燃气轮机为核心的多功能能源动力系统有不同功能和不同能源的两大类型.本文概述了不同功能的总能系统类型的基本形式,如纯产功的、热工领域的多联产、多领域的多功能以及无公害能源系统等多功能系统,并阐述它们的主要特点与过程构成.概述了不同能源的总能系统类别的基本形式,如燃用气体燃料和液体燃料、煤炭、核能、可再生能源、氢能以及多能源互补等多功能能源系统,并阐述它们的主要特点与过程构成.