The impact of CHP generation on CO2 emissions

The combined generation of heat and power (cogeneration) is praised by many as a technique for reducing the emissions of CO₂ in industrialized nations. This is generally true but not always. In this article we discuss the impact of some major variables on the CO₂ emission reduction capacity of cogeneration. Two sets of variables are predominant: the characteristics of the CHP process and the composition of the electricity generation sector. We highlight the interaction between the two sets of variables with the help of diagrams.     

Conceptual design of a novel hybrid fuel cell/desalination system

A novel concept for integrating fuel cells with desalination systems is proposed and investigated in this work. Two unique case studies are discussed — the first involving a hybrid system with a reverse osmosis (RO) unit and the second — integrating with a thermal desalination process such as multi-stage flash (MSF). The underlying motivation for this system integration is that the exhaust gas from a hybrid power plant (fuel cell/turbine system) contains considerable amount of thermal energy, which may be utilized for desalination units. This exhaust heat can be suitably used for preheating the feed in desalination processes such as reverse osmosis which not only increases the potable water production, but also decreases the relative energy consumption by approximately 8% when there is an increase of just 8°C rise in temperature. Additionally, an attractive hybrid system application which combines power generation at 70%+ system efficiency with efficient waste heat utilization is thermal desalination. In this work, it is shown that the system efficiency can be raised appreciably when a high-temperature fuel cell co-generates DC power in-situ with waste heat suitable for MSF. Results indicate that such hybrid system could show a 5.6% increase in global efficiency. Such combined hybrid systems have overall system efficiencies (second-law base) exceeding those of either fuel-cell power plants or traditional desalination plants.     

Analysis of Technology Potential of a Metal-based Latent Heat Storage for Backup Process Steam Supply

An analysis of technology potential of a metal-based high temperature latent heat storage for the application of process steam backup for industrial parks in Germany was carried out. To investigate the integration of the storage into a process steam network, dynamic process simulations were performed. Furthermore, the analysis includes ecological and economical calculations for various fuel types of industrial power plants, plant sizes and auxiliary fuels. Basis of all calculations is an extensive research conducted on the industrial parks in Germany with a dedicated power plant and process steam utilization.     

消除汽缸变形 提高机组热效率

针对某热电厂150MW热电联产机组存在的汽轮机高中压内缸变形严重的问题，分析了其对汽轮机缸效、热耗带来的影响，通过与修造厂合作，现场自主处理了汽缸变形严重的缺陷，提高了高中压缸的缸效，为企业的节能降耗取得了明显的成效。     

Fluids and parameters optimization for a novel cogeneration system driven by low-temperature geothermal sources

A novel cogeneration system was proposed and techno-economically investigated, consisting of a low-temperature geothermally-powered organic Rankine cycle (ORC) subsystem, an intermediate heat exchanger subsystem and a heat pump subsystem. The main purpose is to identify suitable working fluids (among 27 fluids with boiling point temperature ranging from −47.69 to 47.59 °C) and optimized cycle parameters for the ORC-based power generation subsystem. The screening criteria include net power output per unit mass flow rate of hot source (P_net), the ratio of total heat transfer area to net power output (A/W_net), and electricity production cost (epc). Results show that there exists optimum evaporating temperatures maximizing the P_net value and minimizing the A/P_net and epc values. The optimum temperatures vary with different screening criteria and fluids. Optimized fluids based on each screening criteria are not the same. E170, R600 and R141b show the lowest A/W_net and epc values with averagely 3.78% lower P_net value than R236ea which presents the largest P_net value.     

分布式能源系统中燃气轮机热电联产运行方式优化方法

为了对热电联产之中电负荷与热负荷变化进行协调,需对热电供需的不均衡问题进行处理,优化分布式能源的系统之中燃气轮机的热电联产运行方式.同时在传统以热定电与以电定热运行基础上,添加辅助的设备方式,对热电联产运行方式进行补充.本文主要分析了燃气轮机的热电联产两类运行方式,深入研究优化分布式能源的系统之中燃气轮机的热电联产运行方式,为相关研究提供参考.     

High efficient aqueous-film rotating disk photocatalytic fuel cell (RDPFC) with triple functions: Cogeneration of hydrogen and electricity with dye degradation

A high efficient aqueous-film rotating disk photocatalytic fuel cell (RDPFC) was proposed for the simultaneous production of hydrogen and electricity concomitantly with the degradation of high concentration dye wastewater. During the experimental period, the accumulation of hydrogen evolution increased linearly, the current intensity remained stable and the chemical oxygen demand decreased gradually in this RDPFC. Under the same condition, the hydrogen generation rate and the electric flow obtained in the RDPFC were 10 times higher than that of the conventional immersion reactor. The whole system operated steadily and exhibited good performance under a long-running process, and the accumulation of hydrogen were 27.9 and 26.2 mL by using 100 mg L⁻¹ rhodamine B and 300 mg L⁻¹ reactive brilliant red X-3B, respectively. The aqueous-film RDPFC represents a promising candidate for the concurrent function of the organic degradation and clean-energy production by utilizing the light energy and wastewater.     

Assessment of potential for natural gas-based cogeneration in Thailand

Using the results of a comprehensive data analysis of final energy consumption in industry and commercial buildings, the assessment has been made of the potential for gradual implementation of cogeneration plants in these facilities. In doing so, plans for the expansion of the natural gas pipeline distribution network in Thailand are taken into consideration. The sample comprises of 2540 factories and 1651 commercial buildings from which it was found that 817 factories and 966 commercial buildings were suitable for the implementation of natural gas-based cogeneration technologies until 2020. By the implementation of cogeneration in these facilities, it is possible to save 3.2% of the total primary energy consumption in Thailand in 2003.     

Targeting for cogeneration potential through total site integration

Total site integration offers energy conservation opportunities across different individual processes and also to design as well as to optimize the central utility system. In total site integration of the overall process, indirect integration with intermediate fluids or through a central utility system are preferred as it offers greater advantages of flexibility and process control but with reduced energy conservation opportunities. To achieve the maximum possible indirect integration between processes assisted heat transfer, i.e., heat transfer outside the region between process pinch points, plays a significant role. A new concept is proposed in this paper for total site integration by generating a site level grand composite curve (SGCC). Proposed SGCC targets the maximum possible indirect integration as it incorporates assisted heat transfer. In this paper, a methodology is proposed to estimate the cogeneration potential at the total site level, utilizing the concept of multiple utility targeting on the SGCC. The proposed methodology to estimate the cogeneration potential is simple and linear as well as utilizes the rigorous energy balance at each steam header.