Heat Cogeneration System Research Articles

A novel green methanol – heat cogeneration system based on municipal solid waste plasma gasification and coke oven gas: Energy, exergy, economic, and environmental assessment

Burning municipal solid waste for disposal contributes significantly to atmospheric pollution. Utilizing municipal solid waste for green methanol production can alleviate environmental burdens. This study proposes a novel approach based on municipal solid waste plasma gasification, integrating coke oven gas catalytic reforming for green methanol synthesis. A comparative analysis is conducted against a conventional scheme involving water gas shift for syngas production. Simulation models of both approaches are constructed, revealing that the newly proposed system achieves higher methanol synthesis yield and energy utilization efficiency at 90.57 % and 61.28 %, respectively, with an exergy efficiency of 63.74 %. The project incurs an investment cost of 11,448.70 k$, with a dynamic payback period of 4.18 years after a 1-year construction cycle. The net present value over a 25-year operational span is 21,899.16 k$. Additionally, the proposed system emits less than 0.06 tons of carbon dioxide per ton of green methanol, significantly lower than the 0.72 tons emitted by the water gas shift-adjusted syngas synthesis scheme. It makes the proposed approach a potential negative carbon emitter compared to municipal solid waste incineration. Therefore, the system demonstrates favorable thermodynamic performance, coupling with substantial economic and environmental benefits.

Energy and Exergy Analysis of a New Cogeneration Heating System Based on Condensed Waste-Heat Utilization in the Direct Air Cooling Coal-Fired Power Plant

Energy and Exergy Analysis of a New Cogeneration Heating System Based on Condensed Waste-Heat Utilization in the Direct Air Cooling Coal-Fired Power Plant

Performance of single cylinder diesel engine using triple fuel HSD-LPG-Steam

Fuel system modification techniques to improve engine efficiency could be the way to slow down the energy crisis caused by the lack of new fuel inventions. The Compression Ignition (CI) diesel engine is one of the most preferred engines for both in-land and marine transportation motors. The advantages of compact dimensions and large generated power make CI diesel engine superior to other engine types. The large number of single CI diesel engines use in small fishing vessel engines and agricultural machinery will contribute substantially to fuel consumption in a cumulative manner. Previous researchs on the modification of fuel system with bi-fuel system High Speed Diesel (HSD)oil – Liquified Petroleum Gas (LPG) system capable of reducing Brake Specific Fuel Consumption (BSFC) up to 24% and exhaust gas opacity up to 68%. Subsequent studies focused on engines with single fuel HSD oil but were injected with superheated steam in 1 atm (abs) 130 0C by utilizing Heat Recovery Generating System (HRSG) using heat of exhaust gas for a flowrate of 1.5-4.5 kg/hour. It is capable of delivering the performance improvement of Specific Fuel Consumption (SFC), which is reduced by 8.92% compared to diesel engines without steam injection. Recent research combines the above two modification methods so that diesel will adopt two types of fuel- oil-LPG with additional superheated steam injection resulting from exhaust gas heat cogeneration system. Experimental results of the diesel engine with LPG injection maintained at 0.4 kg/h and 3.5 kg/h superheated steam with an engine variation loading of 0.3-0.7 kWh provide an average AFR of 30.09 and SFC improvement up to 37.2% lower than SFC engine standard with a single fuel HSD oil.

Economic Efficiency Assessment of Using Wood Waste in Cogeneration Plants with Multi-Stage Gasification

The aim of this work is to assess the effectiveness of biomass gasification power plants in Russia (Irkutsk region) and compare them with other types of electricity and heat cogeneration systems. Biomass, which is waste from logging and wood processing, is considered as fuel for gasification plants. As a criterion, the cost of energy is used. Analytical relations are obtained for the cost of electric energy at a given cost of thermal energy and vice versa, thermal energy at a given cost of electric energy. These relationships are applied to assess the economic efficiency and compare small-power plants (up to 200–500 kW) such as mini-combined heat and power (CHP) on fuel chips and fuel pellets, coal-fired CHP and gas and liquid fuel power plants (gas-piston and diesel power plants). The latter are equipped with heat recovery boilers and supply consumers with heat and the electric power simultaneously. The calculation results show that the cost of electricity when using wood fuel is significantly less than the cost of electricity from a diesel power plant due to the use of cheaper fuel. In this regard, for autonomous energy systems of small power, especially near logging points, energy supply from biomass gasification power plants is a preferable solution than the use of diesel power plants. Wood fired energy cogeneration systems (mini-CHP) can also successfully compete with coal and gas power plants if they have cheap wood fuel at their location. With the introduction of carbon dioxide emissions charges, the use of not only wood chips, but also pellets becomes competitive in comparison with coal and gas.

Configuration optimization of the novel cogeneration heating system with multi turbine units

At present, the 300 MW extraction condensing turbine units are still the dominant heat sources of cogeneration heating in China. With a rapid increment of heating scale, combined heating with multi turbine units has applied extensively in cogeneration plants. The novel cogeneration heating system can achieve efficient utilization of the condensed waste heat (CWH) of cogeneration plants with multi turbine units, through organically combining the technical elements, such as improving the backpressure of turbine units, using the absorption heat pumps (AHPs), and lowering the return water temperature of heating network. This article takes the 300 MW water-cooling turbine units as analysis objects, adopts the method of the equivalent electricity of heating for energy consumption evaluation, and aims at minimizing the heating energy consumption of the system. Considering the influence on system economy is dominated by the heating energy consumption, the optimization of system configuration is guided by the heating energy consumption analysis. The elaborate and intensive analysis focuses on the optimum system configuration under different numbers of turbine units and different return water temperature. According to the application environment, the system configuration is discussed on the flexible high-backpressure heating mode (FHBM) and the restricted high-backpressure heating mode (RHBM). Through analyzing the variation regularities of the optimum crucial parameters under different conditions, it reveals the internal causes of energy consumption change of the heating system. On this basis, from the perspective of system design, this article summarizes the applicability of the novel high backpressure heating system (NHBS) and the novel absorption heat pump heating system (NAHPS). Furthermore, it refines the configuration optimization principles for the novel cogeneration heating system with multi turbine units. The conclusions are expected to indicate the optimization directions of system design.

Thermodynamic, energy consumption and economic analyses of the novel cogeneration heating system based on condensed waste heat recovery

In order to utilize the condensed waste heat of multi turbine units of cogeneration plant efficiently and simultaneously, a novel cogeneration heating system is proposed. Comparative analyses are made among the conventional cogeneration heating system, the absorption heat pump cogeneration heating system, the high backpressure cogeneration heating system and the novel cogeneration heating system from the aspects of thermodynamics, energy consumption and economy. The research objects are 2 × 300 MW water-cooling turbine units. The aim of the work is to point out the optimization direction of system integration for the novel cogeneration heating system by the thermodynamic analysis, and to reveal the actual heating energy consumption and the unit heating cost of the systems based on the method of equivalent electricity of heating. The study results show that the novel cogeneration heating system reasonably matches the extraction steam, the exhaust steam and the heating network water with each other at different energy levels. Therefore, it has evident advantages in the aspects of the thermodynamic perfection, the actual heating energy consumption and the economy. Compared with other systems, the novel cogeneration heating system increases the total exergy efficiency by 6.1–14.1%, reduces the equivalent electricity of heating by 11.1–29.4% and reduces the unit heating cost by 8.7–23.9%.

Development of a PEMFC-based heat and power cogeneration system

ABSTRACTHydrogen-fed proton exchange membrane fuel cell (PEMFC) has to overcome high installation and operation cost before being adopted as a distributed power candidate. Cogeneration of power and heat is a good approach to increase hydrogen energy utilization rate. A PEMFC-based power and heat cogeneration system is proposed and established in the current study to investigate system’s technological and economical feasibility. This cogeneration of heat and power (CHP) system composes of a 2.5-kW fuel cell stack, hydrogen supply system, air supply system, water and heat management system, and heat recovery system. The control strategies to automate the system operation are realized by a programmable automation controller (PAC) system. Detailed measurement of the system is also constructed along with a web-based human–machine interface (HMI) platform to facilitate experiments and demonstration. Preliminary testing of the CHP system shows good performance of heat and power outputs. System’s electrical power conversion efficiency and thermal efficiency of the CHP system are measured at 38% and 35%, respectively. System combined efficiency therefore reached about 73%.

Combined heating operation optimization of the novel cogeneration system with multi turbine units

At present, large extraction condensing turbine units are generally adopted for combined heating in the cogeneration plants of northern China. A large amount of condensed waste heat of the exhaust steam releasing to the environment leads to a great heat loss of the cold end system. The novel cogeneration system significantly improves energy efficiency of the plant by efficiently recovering the condensed waste heat of multi turbine units. For the turbine units with complete recovery of the condensed waste heat, the corresponding cooling towers are closed during the freezing period. With the reduction of the heat load, the surplus condensed waste heat should be discharged by the cooling towers. However, the outdoor wet-bulb temperature is very low during the severe cold period, which results in a surplus of the cooling capacity of the cooling towers. When releasing a small amount of the condensed waste heat, the cooling towers may confront with the frozen risk. A new type of connecting and switching method for the cold end system of the multi turbine units is proposed to avoid the frozen risk. On this basis, with the method of equivalent electricity of heating, an optimized combined heating operation strategy is proposed for the multi turbine units under full operating conditions. The case study takes 4 × 300 MW turbine units as an example, the heat load regulation process is simulated according to the optimized strategy and the discussions are made on the seven regulation stages. Furthermore, the heating performance of the absorption heat pumps and the variation and distribution regularities of the energy consumptions during the heating period are analyzed in detail. Case study results show that, the heating coefficient of performance of the absorption heat pumps is obviously improved after the steam-water heat exchanger withdraws from heating. Compared with the traditional cogeneration heating system, the novel cogeneration system reduces heating energy consumption by 47.7% under the premise of avoiding the frozen risk of the cooling towers during the winter.

Study of new cascade heating system with multi-heat sources based on exhausted steam waste heat utilization in power plant

Utilizing waste heat of exhausted steam in power plant as a new type of heat source is a key direction to achieve both energy-saving and clean district heating. This paper firstly reviews current mature waste heat utilization technologies, including “absorption heat pump”, “increasing back pressure of turbine” and “decreasing return water temperature of heat network”. Using only one method is not applicable to recovery all the exhausted steam waste heat of multiple turbine units due to its respective limitations. In view of this technical difficulty, this paper proposes a new cascade heating system with multi-heat sources based on waste heat utilization. Extraction steam and exhausted steam are involved to achieve the cascade temperature-rise of heat network water. Corresponding evaluation methods are presented, including the last-stage safety of the large unit and the comprehensive energy efficiency of the new cogeneration heating system. Taking 2 × 300 MW water-cooled units as the example to actualize the new system, the effects of key parameters on energy efficiency and economy are analyzed, and then further researches about integration optimization of the new system are developed. In this study, first keep constant return water temperature of primary heat network, the optimal condition is gained. At this point, all the waste heat of exhausted steam is recovered, the energy consumption of power plant is reduced by 33% and the total cost per heat output ct is reduced by 22.3%, compared with conventional cogeneration system. Then reduce the return water temperature in different level, both the energy consumption and the total cost per heat output ct can be further lowered, the energy efficiency and the economy are better improved.

Full operating conditions optimization study of new co-generation heating system based on waste heat utilization of exhausted steam

Utilizing the waste heat of exhausted steam in power plant as a new type of heat source is a key direction to achieve both energy-saving and clean urban heating. In order to recycle all the exhausted steam waste heat of multiple turbine units in designing condition, the authors’ research group proposed a new cascade heating system with multi-heat source and applied it in several air cooling power plants in China. This paper focused on the system integration improving and operation strategy formulating, the main studies included: (1) Established the calculation model of system heating characteristics, and analyzed the problems about energy efficiency of system and safety of air cooled condenser in full operating conditions. (2) Introduced the “equivalent electricity of heating” as the evaluation method of comprehensive energy efficiency of the new co-generation heating system. (3) Improved the integration of heating system to further realize energy cascade utilization between turbine units. (4) Aiming at the improved heating system, the comprehensive optimization ideas of operational parameters in full operating conditions were put forward. By above methods, on one hand the “equivalent electricity of heating” of the new co-generation heating system is decreased by 16%, the comprehensive energy efficiency of system is improved, on the other the freezing risk of air cooled condenser is relieved, the operation safety of system is improved.

Micro cogeneration - rich-methane gasifier and micro gas turbine

The study presents a concept of integration a gasifier system with distributed generation of electricity and heat cogeneration system based on a gas microturbine. The gas generator is supplied by the RDF fuel from waste and biomass fuel Bio-CONOx. In the scale considered, the cogeneration system is designed to produce 30kWe of electricity and approx. 50kW of heat. Important perspective directions of technology development are: (i) the possibility of gas microturbine to cooperate with the gasifier (up to date, in such systems were used, and continue to apply only piston engines), (ii) the production of syngas in the gasifier (for efficient cogeneration) in the composition of which there is a high content of methane (CH 4 = 18%-22%). In the first step of possible commercialization a mathematical model to simulate single shaft gas turbine cogeneration plant has been developed. In conceptual design is application of microturbine as the prime mover of Combined Heat and Power (CHP) system but with especial emphasis on possible use of a low calorific gas attainable from presented in details a gasifier unit. To support the calculations for preliminary design analysis, a computer program is developed in EES software environment.

Efficiency analysis of a novel electricity and heat co-generation system in the basis of aluminum–water reaction

With high calorific value and the environmental friendly features, hydrogen has been attached much importance. Aluminum–water reactions at medium–high temperature perform well in hydrogen generation as well as heat utilization. Active researches of the aluminum–water reactions in recent years can be attributed to the increasing interest of hydrogen generation and energy conversion.In the basis of aluminum–water reactions, the concept of a novel electricity and heat co-generation system was proposed here and it was primarily composed of a reactor, one or two turbines and generators, heat exchanger for heat user, a fuel cell and a pump. Two layouts were designed and analyzed: the one turbine layout (OTL) and the two turbine layout (TTL).The effects of key parameters, such as the steam temperature and pressure at turbine inlet, the heat user temperature and fuel cell conversion efficiency were investigated. The co-generation system could generate heat and electricity of about 22.2 MJ/kg (Al) in the OTL design. The system utilization efficiency, the ratio of the output was approximate 70% and the electricity generation efficiency could reach up to 41.52% (OTL) and 49.25% (TTL) in the two cases respectively. The OTL presented a higher heat user utilization efficiency than TTL, because of the higher turbine outlet parameters. The TTL layout with the integration of fuel cell and heat user enhanced electricity output by 45.06% in comparison with the OTL layout. The steam temperature at turbine inlet showed considerable impacts on the system utilization efficiency at the TTL case. Enhancing fuel cell conversion efficiency benefited the system and fuel cell utilization efficiencies, especially at the TTL case.

Study on Thermal Storage Device Model and Control Strategy for Cogeneration and Wind Power Heating System

Resources of wind power due to its presence greater volatility, increasing the difficulty of regulating for the power grid. In the supply side, by installing thermal storage device to the cogeneration units so as to increase the adjusting capacity in the supply side of the power system, in the load side, the wind power heating system added heat storage device, increasing the load that can be adjusted. These two measures could be better to solve the problem that part of the abandoned wind. In this paper, analyzed the theoretical basis of each system briefly, added thermal storage device in electric –thermal combine system, and the thermal storage device installation position has been described too. Due mostly theoretical on thermal storage device is about the thermodynamic aspects, it is rather strange for electricity workers, so in this electrical-thermal combined system, its thermal storage devices and electric boiler thermal model have been made a simple analysis and described its control strategy. The control strategy was a comprehensive coordination to the power grid, meanwhile, taking into account the hysteresis characteristics, delay effects and daily regulation plan features of the thermodynamic parameters of thermal storage system make a reasonable start-stop control strategy finally.

Dynamic Simulation of a Novel Solar Heating System Based on Hybrid Photovoltaic/Thermal Collectors (PVT)

In this paper, the authors aim at improving the knowledge on this topic presenting a dynamic model of a solar heating system based on PVT technology. With respect to the papers mentioned above, the layout proposed includes all the components required for operating the sys-tem. The TRNSYS simulation platform of the PVT cogeneration heating system has been established for researching the system performance of PVT solar cogeneration heating system. The inlet and outlet temperature, the electrical power output of PVT collector, heat consumption, outlet temperatures of auxiliary heat source and outlet temperatures of heat storage tank of PVT collector have been studied in this paper. The results of this investigation may be summarized as follows. The PVT collector 32m2 in size in the system can achieve annual power output of 131kWh electric energy. The heat gain of heat collector system between 12 am and 6 pm on the typical day, when the auxiliary heat source is not turned on can meet the load demand. Indoor temperature varies between 16.3∼19.5°C on the typical day, fluctuation of indoor temperature s impacted by outdoor ambient temperature and solar radiation. The entire heating season that the solar fraction of this solar heating system is 31.7%, which is close to the design value of 30%.

Operational Efficiency Evaluation of Cogeneration Central Heating System Based on Improved Matter-Element Model in North China

In order to assess the operational efficiency of cogeneration heating system and measure the systems social, economic, energy-saving and environmental protection benefits in North China, an evaluation index system is built up after analyzing the influence factors which may impact the heating system operation. The association degree function of classical matter element method is improved. And then, an improved matter-element evaluation model is established, which not only can figure out the evaluation grade that heating system belongs to, but also can point out the direction of the further improvement work. Besides, the model has other merits, such as uncomplicated operation, good scalability and so on. Example indicates that this evaluation model has excellent applicability and operability.

Assessment of load-following capability of VHTR cogeneration systems

A newly-proposed control system design for the GTHTR300C, a nuclear power and heat cogeneration system employing a Very High Temperature Reactor (VHTR), offering load-following capability is presented. The system is designed to follow significant seasonal variations of electric load demand. It combines several fundamental control methods including inventory control used to adjust primary coolant pressure, flow bypass control used to regulate the coolant flow rate and turbine inlet temperature, and additional flow control to vary the IHX heat rate. The goal of the control system design is such that the wide range of load-following capability can be performed at constant reactor power and thermal efficiency, which maximizes plant economics, while minimizing transient thermal stresses in the reactor equipment. The control simulation of a representative load-following operation is carried out using a system analysis code and discussed in the paper. The results of the simulation show that the design goal can be effectively met by monitoring and controlling constant a few selected operating parameters of reactor and gas turbine including reactor outlet temperature, turbine inlet temperature and speed. The original control system design shows that load-following operation at constant reactor power and thermal efficiency by a VHTR power and heat cogeneration system is feasible.

Development of Distributed Heat and Power Cogeneration System Integrated by Gasifier, Stirling Engine and Absorption Cooler

This study proposes a biomass power and heat cogeneration system that comprised of a gasifier, Stirling engine/alternator, and absorption cooler. Gasification is the most versatile approach to utilize biomass for the flexibility and affectivity of this technology. The flue gas from the combustion of the gasified gas propels a free-piston Stirling engine/alternator, which produces 50 or 60 Hz alternating current as output. The absorption cooler absorbs the residual heat from the flue gas after Stirling engine’s hot end and produces low temperature energy. This cold energy could be used to satisfy air conditioning requirement or be directed to the cold end of Stirling engine to further increase the power efficiency of the Stirling engine. The solid biomass rice husks were tested in this study, in addition, the current power and heat cogeneration system’s gross output exceeded the rated 500w engine gross output for this tested feeds. The total efficiency of this system was approaching to 46%.

Characterization of Perovskite-Type Anode Materials: Sr2-xLaxFeMoO6-δ (x = 0-0.5) for SOFCs

not Available.

Solid Oxide Fuel Cell Development at NIMTE

The biggest SOFC R&D activities in China are conducted at NIMTE where 45 full time staffs are vertically integrated. We manufacture and sale planar anode supported cells for international market with the highest performance/price ratio. We offer various nano-powders including LSM, LSCF, LSC, CGO, YSZ and SSZ. Long term tests on performance degradation, in particular at low temperature and high current density, are intensively carried out in our cell testing group. We demonstrated low cost stack by combining internal manifolding design and low cost components selection. A five cell short stack has run for more than 3000 hours and the voltage is monitored individually. Stacks of 500W to kW power range are built and tested. We successfully manufactured 30×30cm2 cells for multi-kilowatt single stack. 2kW power and heat co-generation system are under development and 20kW electrical generation system are planned this year in collaboration with a big Chinese electricity generation company.