热电联产的经济性分析

通过理论推导和论证求得各种类型的供热机组的经济条件,进而对机组方案的经济效益做出正确而快速的判断,以确定其是否存在经济效益。     

Potential emissions reductions from the use of dual-combined heat and power systems in different climate conditions

In this paper, the potential carbon dioxide emissions (CDE) reduction from the use of a combined heat and power system with two power generation units (D-CHP) is examined for a restaurant building in nine different climate conditions. The performance of the D-CHP system is evaluated on the basis of CDE and operational cost savings. In addition, the results from the D-CHP optimised scheme are compared with the optimised results of a base-loaded CHP (BL-CHP) system and a CHP system operated following the electric load (CHP-FEL). Results show that the D-CHP system produces greater savings over BL-CHP and CHP-FEL for most of the locations examined, whether optimised based on CDE or based on cost. Moreover, the effect of the emissions and cost spark spreads for each location on the D-CHP system performance is analysed. Results indicate that higher spark spreads are shown to yield greater savings for all CHP configurations.     

Analysis and optimization of the use of CHP-ORC systems for small commercial buildings

The use of combined heating and power (CHP) systems is increasing rapidly due to their high potential of reducing primary energy consumption (PEC), cost, and carbon dioxide emissions (CDE). These reductions are mainly due to capturing the exhaust heat to satisfy the thermal demand of a building. However, when the CHP system is operated following the electric load, the recovered exhaust heat may or may not be sufficient to satisfy the thermal demand of the facility. When the recovered exhaust heat is more than the heat required, the excess is usually discarded to the atmosphere. An organic rankine cycle (ORC) can be used to recover the surplus exhaust heat to generate extra electricity. Therefore, combining the ORC system with the CHP system (CHP-ORC) reduces the electricity that has to be produced by the CHP system, thereby reducing the total PEC, cost, and CDE. The objective of this paper is to study the energetic, economical, and environmental performance of a combined CHP-ORC system and compare its performance to a standalone CHP system and a reference building for different climate zones. A comparison of a CHP-ORC system operating 24 h with a system operating during typical office hours is also performed.     

Technical, economic and environmental analysis of energy production from municipal solid waste

Four technologies are investigated which produce energy from municipal solid waste (MSW): incineration, gasification, generation of biogas and utilisation in a combined heat and power (CHP) plant, generation of biogas and conversion to transport fuel.Typically the residual component of MSW (non-recyclable, non-organic) is incinerated producing electricity at an efficiency of about 20% and thermal product at an efficiency of about 55%. This is problematic in an Irish context where utilisation of thermal products is not the norm. Gasification produces electricity at an efficiency of about 34%; this would suggest that gasification of the residual component of MSW is more advantageous than incineration where a market for thermal product does not exist. Gasification produces more electricity than incineration, requires a smaller gate fee than incineration and when thermal product is not utilised generates less greenhouse gas per kWh than incineration. Gasification of MSW (a non-homogenous fuel) is, however, not proven at commercial scale.Biogas may be generated by digesting the organic fraction of MSW (OFMSW). The produced biogas may be utilised for CHP production or for transport fuel production as CH₄-enriched biogas. When used to produce transport fuel some of the biogas is used in a small CHP unit to meet electricity demand on site. This generates a surplus thermal product.Both biogas technologies require significantly less investment costs than the thermal conversion technologies (incineration and gasification) and have smaller gate fees. Of the four technologies investigated transport fuel production requires the least gate fee. A shortfall of the transport fuel production technology is that only 50% of biogas is available for scrubbing to CH₄-enriched biogas.     

Technical/economic/environmental analysis of biogas utilisation

Biogas may be utilised for Combined Heat and Power (CHP) production or for transport fuel production (CH₄-enriched biogas). When used to produce transport fuel either electricity is imported to power the plant or some of the biogas is used in a small CHP unit to meet electricity demand on site. The potential revenue from CH₄-enriched biogas when replacing petrol is higher than that for replacing diesel (Irish prices). Transport fuel production when replacing petrol requires the least gate fee. The production of greenhouse-gas is generated with cognisance of greenhouse-gas production with the scheme not in place; landfill of the Organic Fraction of Municipal Solid Waste (OFMSW) (20% of biomass) with and without combustion of landfill gas is investigated. The transport scenario with importation of brown electricity generates more greenhouse-gas than petrol or diesel, when the ‘do-nothing’ case involves combustion of landfill gas. The preferred solution involves transport fuel production with the production of CHP to meet electricity demand on site. A shortfall of this solution is that only 53% of biogas is available for export.     

Simulation analysis of hydrogen recirculation rates of fuel cells and the efficiency of combined heat and power

The objective of this study was to simulate a proton-electrolyte membrane fuel cell (PEMFC) system, namely a PEMFC stack, an anode gas supply subsystem, an anode gas-recovery subsystem, a cathode gas supply subsystem, and a tail gas exhaustion subsystem. In addition, this paper presents an analysis of the efficiency of combined heat and power (CHP) systems. MATLAB and Simulink were employed for dynamic simulation and statistical analysis. The rates of active and the passive anode hydrogen recirculation were considered to elucidate the mechanism of hydrogen circulation. When recovery involved diverse recovery mechanisms, the recirculation rate was affected by the pressure at the hydrogen outlet of the PEMFC system. The greater the pressure was at that outlet, the higher the recovery rate was. In the hydrogen recovery system, when the temperature of the hydrogen supply end remained the same, increasing the temperature of the gas supply end increased the efficiency of the fuel cells; fixing the flow of the hydrogen supply end and increasing the temperature of the hydrogen supply end increased the efficiency of the PEMFC system. A calculation of the efficiency of the recovery system indicated that the thermal efficiency of the fuel cells exceeded 35%, the power generation efficiency exceeded 45%, and the efficiency of the CHP system exceeded 80%.     

Theoretical and experimental investigations on thermal management of a PEMFC stack

In recent years micro-cogeneration systems (μ-CHPs), based on fuel cells technology, have received increasing attention because, by providing both useful electricity and heat with high efficiency, even at partial loads, they can have a strategic role in reduction of greenhouse gas emissions. For residential applications, the proton exchange membrane fuel cell (PEMFC), is considered the most promising, since it offers many advantages such as high power density, low operating temperature, and fast start-up and shutdown.In this paper the electrical and thermal behaviors of a PEMFC stack, suitable for μ-CHP applications, have been investigated through experimental and numerical activity.The experimental activity has been carried out in a test station in which several measurement instruments and controlling devices are installed to define the behavior of a water-cooled PEMFC stack. The test station is equipped by a National Instruments Compact DAQ real-time data acquisition and control system running Labview™ software.The numerical activity has been conducted by using a model, properly developed by the authors, based on both electrochemical and thermal analysis.The experimental data have been used to validate the numerical model, which can support and address the experimental activity and can allow to forecast the behavior and the performance of the stack when it is a component in a more complex energy conversion system.     

Combined heat and power systems with dual power generation units and thermal storage

The objective of this paper is to study the performance of a combined heat and power (CHP) system that uses two power generation units (PGU). In addition, the effect of thermal energy storage is evaluated for the proposed dual‐PGU CHP configuration (D‐CHP). Two scenarios are evaluated in this paper. In the first scenario, one PGU operates at base‐loading condition, while the second PGU operates following the electric load. In the second scenario, one PGU operates at base‐loading condition, while the second PGU operates following the thermal load. The D‐CHP system is modeled for the same building in four different locations to account for variation of the electric and thermal loads due to weather data. The D‐CHP system results are compared with the reference building by using conventional technology to determine the benefits of this proposed system in terms of operational cost and carbon dioxide emissions. The D‐CHP system results, with and without thermal storage, are also compared with that of single‐PGU CHP systems operating following the electric load (FEL), following the thermal load (FTL), and base‐loaded (BL). Results indicate that the D‐CHP system operating either FEL or FTL in general provides better results than a single‐PGU CHP system operating FEL, FTL, or BL. The addition of thermal storage enhances the potential benefits from D‐CHP system operation in terms of operational cost savings and emissions savings. Copyright © 2013 John Wiley & Sons, Ltd.     

分布式热电联产中热电比的确定

分布式供能是国际上近几年发展起来的一种新的能源供应概念和方式。在分布式热电联产系统中,余热锅炉补燃是调节热电负荷的有效手段,选择合适的补燃率有助于提高余热锅炉和分布式热电联产系统的效率。本文基于上海理工大学分布式热电联产实验台的数据,通过与购买市电＋单独燃油锅炉供热进行比较,给出了一种确定最佳热电比的方法。     

北京PM2.5与冬季采暖热源能关系及治理措施

为了治理严重灰霾天气,北京市政府采取了热电联产“煤改气”（使用大型燃气热电联产全面替代大型燃煤热电联产）措施。这个措施对减少灰霾、改善空气质量有多大的作用呢？针对此问题,本文首先研究了PM2．5的形成机制与造成严重灰霾的关键因素,再比较冬季采暖各种热源所造成的污染物排放量,通过定量的计算比较使用燃气热电联产供热和燃煤热电联产两种方式供热对PM2．5形成的贡献。研究表明：减少NOx排放量是治理PM2．5的关键,而热电联产“煤改气”措施并不能显著降低NOx排放量,反而会大幅增加天然气用量,造成用气矛盾,因此不宜作为治理大气污染的有效措施来大范围推广。