Cost-optimized real-time operation of CHP systems

The Cooling, Heating, and Power (CHP) systems have been widely recognized as a key alternative for thermal and electric energy generation because of the outstanding energy efficiency, reduced environmental emissions, and relative independence from centralized power grids. Nevertheless, the total energy cost of CHP systems can be highly dependent on the operation of individual components. This paper presents an energy dispatch algorithm that minimizes the cost of energy (e.g., cost of electricity from the grid and cost of natural gas into the engine and boiler) based on energy efficiency constrains for each component. A deterministic network flow model of a typical CHP system is developed as part of the algorithm. The advantage of using a network flow model is that the electric and thermal energy flows through the CHP equipment can be readily visualized allowing for easier interpretation of the results. This algorithm has been used in simulations of a case study on the operation of an existing micro-CHP system. The results from the simulation are presented in the paper to demonstrate the economical advantages resulting from optimal operation.     

Merging of energy and environmental analyses for district heating systems

District heating (DH) systems, together with combined heat and power (CHP) plants, have been increasing both in number and interest over the last decade, but the environmental improvements are still controversial, because although there is usually a reduction in CO₂ emissions, a positive effect concerning other pollutants is not always certain. A limited number of works that pay particular attention to the local environmental effect due to DH plants have been found in a brief overview of DH papers. The energetic and environmental impact of a new DH+CHP plant has been investigated in the present paper, where this plant has been proposed to substitute the existing heating systems. The environmental aspects concerning the local variations due to some pollutants, such as sulfur oxides (SO_x), particulate matter (PM) and nitrogen oxides (NO_x), are in particular taken into account. The main data necessary for the analysis and the hypotheses that are useful to simulate the behavior of the local heating plant and DH plants (e.g. efficiency, the heating demand, etc.) are discussed. A dispersion model (Gaussian model) has been used to evaluate the effect at a local scale. Finally, a case study concerning a new DH+CHP plant in Northern Italy is presented and discussed.     

Weighting methodologies in multi‐criteria evaluations of combined heat and power systems

Several combined heat and power (CHP) system options are presented to assess and compare with respect to the end users' requirements. According to the obtained data from literature, 16 kinds of CHP systems are evaluated using gray relational method in multi‐criteria, such as technology, economy, environment, and society. The results depend greatly on the criteria weights in multi‐criteria evaluations. Aiming to obtain rational result, this paper reviews the weighting method briefly and proposes an optimal combined weighting method to consider the subjectivity of decision‐maker and the objectivity of measurement data. The singular value decomposition aggregation method is employed to verify the rationality of evaluation result. Through multi‐criteria evaluation and discussions, the combination weighting method is recommended to be used in the selection of CHP schemes. Finally, the best CHP system is selected and the most conspicuous factors having great impact on CHP system with respect to the users' requirements are given out. Copyright © 2009 John Wiley & Sons, Ltd.     

Experimental activity on two tubular solid oxide fuel cell cogeneration plants in a real industrial environment

The EOS project carries on an industrial research on stationary fuel cells based on the SOFC technology developed by Siemens, through a co-operation between TurboCare S.p.A. and Politecnico di Torino. Two SOFC units have been installed and operated in the TurboCare workshop. The running hours of the CHP100 generator are more than 16,400 h; the 5-kW Alpha6 generator is in operation since more than 10′000 h.     

3 MW集中式热电肥联产沼气工程设计与建设

山东民和牧业股份有限公司利用所属23家养殖场的鸡粪和污水作为沼气发酵原料,投资建设大型畜禽养殖场集中式沼气发电工程.原料经水解除砂工艺将鸡粪中的砂砾除去,保证发酵效率;采用中温(38 ℃)发酵工艺,产沼气30 000 m3/d;采用高效率低运行成本的生物脱硫工艺,将沼气中的H2S含量降至200×10-6以下;经净化的沼气在双膜干式贮气柜中贮存,供给热电联产的发电机组使用.发电量60 000 kWh/d,机组余热用于冬季发酵系统自身增温;发酵后的沼液用作周围葡萄、苹果及玉米地的有机肥料.项目实现了温室气体减排84882tCO2当量.文章介绍了该沼气发电工程的工艺特点和技术要点,为同类型沼气发电工程设计和建设提供参考.     

Should a small combined heat and power plant (CHP) open to its regional power and heat networks? Integrated economic,energy, and emergy evaluation of optimization plans for Jiufa CHP

The development of industrial ecology has led company managers to increasingly consider their company's niche in the regional system, and to develop optimization plans. We used emergy-based, ecological-economic synthesis to evaluate two optimization plans for the Jiufa Combined Heat and Power (CHP) Plant, Shandong China. In addition, we performed economic input–output analysis and energy analysis on the system. The results showed that appropriately incorporating a firm with temporary extra productivity into its regional system will help maximize the total productivity and improve ecological-economic efficiency and benefits to society, even without technical optimization of the firm itself. In addition, developing a closer relationship between a company and its regional system will facilitate the development of new optimization opportunities. Small coal-based CHP plants have lower-energy efficiency, higher environmental loading, and lower sustainability than large fossil fuel and renewable energy-based systems. The emergy exchange ratio (EER) proved to be an important index for evaluating the vitality of highly developed ecological-economic systems.     

Emissions targeting and planning: An application of CO2 emissions pinch analysis (CEPA) to the Irish electricity generation sector

This paper outlines the past analysis and projected planning of the Irish electricity generation sector using an extension of a novel methodology based on a graphical optimisation concept. The main two adaptations/extensions to the current form of the methodology are proposed as both the forecasting adaptation and the extension that accounts for the dynamic nature of electricity supply–demand. The determination of an optimal energy resource (OER) mix (or optimal fuel mix) for the sector will look to give guidelines towards fulfilling the sector's Kyoto targets, as well as yielding a possible approach for other sectors to follow in the future. Data pertaining to the sector for the year 2005 was taken in order to illustrate the analysis and forecasting procedures.     

The development of a small PEMFC combined heat and power system

A proton exchange membrane fuel cell combined heat and power system has been chosen as a platform on which key components and system integration technologies have been developed to advance the applications of fuel-cell technology. The prototype system consists mainly of a fuel-cell stack, a natural gas reformer to supply hydrogen-rich reformate gas to the stack, a power conditioner to convert and invert the electricity generated by the stack, and a water and heat management network to provide the oxidizer (air) to and necessary cooling and humidification for the stack. The design of the stack and its components, catalysts development, design and testing of the natural gas reformer, were studied. In addition, the durability of a CO tolerant membrane-electrode-assembly has been studied with the assistance of air bleeding. Preliminary testing of the prototype combined heat and power system was carried out. It was found that the maintenance of a uniform output voltage across all single cells was more difficult with reformatted gas rather than using pure hydrogen. It was also found that the design of water and heat management network played an important role in the overall efficiency of the system.     

Cost targets for domestic fuel cell CHP

Fuel cells have the potential to reduce domestic energy bills by providing both heat and power at the point of use, generating high value electricity from a low cost fuel. However, the cost of installing the fuel cell must be sufficiently low to be recovered by the savings made over its lifetime. A computer simulation is used to estimate the savings and cost targets for fuel cell CHP systems.     

Modelling and optimization of the smart hybrid renewable energy for communities (SHREC)

The future energy system in community level should be more ‘smart’ to secure reliability, enhance market service, minimize environmental impact, reduce costs and improve the use of renewable energy source (RES). Therefore, this paper proposes an energy integration system – smart hybrid renewable energy for communities (SHREC). It considers both thermal (heating and cooling) and electricity market in a large community level and highlight the interactions between them through utilizing RES, combined heat and power (CHP) and energy storages. A planning model based on CHP modelling is developed for the SHREC system. A linear programming (LP) algorithm is developed to optimize the SHREC system in a weekly period and the results are compared with an existing energy optimization software. We also demonstrate the model in a sample SHREC system during three typical weeks with cold, warm and mid-season weather in the year 2011. The results indicate that the developed modelling and optimization method is more efficient and flexible for the smart hybrid renewable energy systems.