Analysis and optimization of CCHP systems based on energy, economical, and environmental considerations

Analysis of combined cooling, heating, and power (CCHP) systems is frequently based on reduction of operating cost without measuring the actual energy use and emissions reduction. CCHP systems can be optimized based on different optimization criterion such as: energy savings, operation cost reduction or minimum environmental impact. In this study, CCHP systems operated following the electric load (FEL) and the thermal load (FTL) strategies are evaluated and optimized based on: primary energy consumption (PEC), operation cost, and carbon dioxide emissions (CDE). This study also includes the analysis and evaluation of an optimized operational strategy in which a CCHP system follows a hybrid electric-thermal load (HETS) during its operation. Results show that CCHP systems operating using any of the optimization criteria have better performance than CCHP systems operating without any optimization criteria. For the evaluated city, the optimum PEC and cost reduction are 7.5% and 4.4%, respectively, for CCHP-FTL, while the optimum CDE reduction is 14.8% for CCHP-FEL. Results also show that the HETS is a good alternative for CCHP systems operation since it gives good reduction of PEC, cost, and CDE. This optimized operation strategy provides a good balance among all the variables considered in this paper.     

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.     

Analysis of a combined cooling, heating, and power system model under different operating strategies with input and model data uncertainty

Combined cooling, heating, and power (CCHP) system models have been used by many researchers to compare their performance with conventional systems. However, decisions based on the results of computer simulations need to take into account the uncertainty of these results to get insight into the level of confidence in the predictions. This paper presents an analysis of a CCHP system model under different operating strategies with input and model data uncertainty. However, the uncertainties that underlie the variation in input parameters such as the thermal load, natural gas prices and electricity prices are not readily available. Additionally, engine performance uncertainty can be difficult to characterize because of the nonlinearity of engine efficiency curves. This paper presents practical and novel approaches to estimating the uncertainty in these and other input parameters. A case study using a small office building located in Atlanta, GA, is described to illustrate the importance of the use of uncertainty and sensitivity analysis in CCHP system performance predictions, and how the primary energy consumption, operational cost, and carbon dioxide emissions are affected by the uncertainty associated with the model input parameters.     

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.     

天然气三联供技术在城市综合体中应用分析

天然气冷-热-电三联供技术是一种建立在能源梯级利用基础上,制冷、供热和发电过程一体化综合应用的多联产系统。在城市综合体项目中应用天然气冷-热-电三联供技术,不但通过发电自用减缓城市供电压力,还能够充分利用余热资源为建筑提供采暖、制冷和生活热水,减少常规能源的消耗,具有良好的经济、环境和社会效益。在能源环境危机日益突出的当代社会,天然气三联供技术将会得到广泛的应用。     

复合供能系统优化配置和运行策略研究

针对由微小型燃气轮机分布式供能系统和地下水地源热泵组成的复合供能系统,以北京市某典型医院为应用对象,分别以年总费用和天然气年节能率为优化目标,对系统在经济最优、以热定电和节能最优3种运行策略下的优化配置和运行规律进行了研究。结果表明,与电制冷机+燃气锅炉+市电的常规分供方案和地下水地源热泵+市电方案相比,复合供能系统具有经济、节能与电力调峰性能明显等综合优势;与联合循环+燃气锅炉+电制冷机模式相比,复合供能系统在传统的经济最优和以热定电运行策略下并不节能,但在节能最优运行策略下可实现节能。     

三联供系统配置及运行策略的多目标优化分析

在满足建筑物冷热电负荷的前提下,建立了联供系统以年费用、一次能源消耗和二氧化碳排放要求的多目标函数,并利用权重系数将多目标转换为单目标优化模型。以上海市某能源中心的工程为例,得出了冷、热、电三联供系统的最优配置容量及运行策略。     

热电冷联供系统在海上平台的应用

文章介绍热电冷联供系统的设备组成及其设计注意事项;介绍以燃气轮机为发电机组的热电冷联供系统案例。在热电冷联供系统中配置溴化锂吸收式制冷机,可充分发挥其利用低品位能源的优势;设计热电冷联供系统前,应进行必要的经济性分析,合理确定设备配置方案和配置容量;以燃气轮机发电机组和烟气型溴化锂吸收式冷热水机组为主要设备组成的热电冷联供系统,烟气系统的设计和安装连接是关键。文章可为燃气轮机热电冷联供系统的设计和建造提供技术参考。     

典型办公楼负荷预测

对于冷热电三联供系统而言,为了使系统更好的发挥出优势,就要使系统和建筑的负荷较好的匹配,那么得到逐时的冷热电负荷数据就变得至关重要.参照日本三联供手册的方法,根据我国国情,以北京典型办公楼为例,采用模拟结合经验值的方法,得到适合中国办公楼的逐时负荷系数,以便为办公楼类建筑配置系统时提供参考依据.     

初探冷热电三联供系统在A级数据中心的应用

冷热电三联供(CCHP)系统是一种建立在能量梯级利用概念基础上,将供热(采暖和供热水)、制冷及发电过程有机结合在一起的总能系统。本文按照数据中心的用能特点,探讨了三联供系统在数据中心中应用的可行性。     

冷热电三联供系统在民用建筑中的应用

结合某办公楼中冷热电三联供系统的应用,介绍冷热电三联供的原理、相关规范标准、民用建筑中应用冷热电三联供系统的运行方案、技术经济分析、发电机组规模的确定原则及配电系统的主接线形式。     

冷热电联供系统能耗与CO2排放特性分析

建立了微型燃气轮机冷热电联供系统数学优化模型。基于上海某办公楼典型日负荷结构,以总运行费用最低为优化目标,采用模式搜索法对数学优化模型进行求解计算,分析了微型燃气轮机发电效率及空燃比对联供系统能耗与CO2排放特性的影响。研究结果表明微型燃气轮机发电效率及空燃比对联供系统能耗与CO2排放的影响趋势是一致的,可以通过调节微型燃气轮机发电效率及空燃比来充分发挥联供系统节能性和环保性的优势。     

燃气轮机进气冷却对冷热电联产性能的影响

基于Solar Centaur 50燃气轮机简单循环冷热电联产系统，结合工程实例给出了燃气轮机进口空气温度对冷热电联产系统性能的影响。     

热泵在燃气冷热电联供系统的应用

介绍了某生态园燃气冷热电联供能源站的技术方案。采用水源热泵利用夜间城市电网低谷电进行蓄冷、蓄热,白天用于供冷、供热,延长了燃气发电机组的运行时间,降低了运行成本,提高了供冷、供热的安全可靠性。     

Benchmarking energy consumption and CO2 emissions from rainwater‐harvesting systems: an improved method by proxy

Life cycle analyses (LCAs) show the main operational energy contribution for rainwater‐harvesting (RWH) systems come from ultraviolet (UV) disinfection and pumping rainwater from tank to building. Simple methods of estimating pump energy consumption do not differentiate between pump start‐up and pump‐operating energy or include pump efficiency parameters. This paper outlines an improved method incorporating these parameters that indirectly estimates pump energy consumption and carbon dioxide (CO₂) emissions using system performance data. The improved method is applied to data from an office‐based RWH system. Comparison of the simple and improved methods identified the former underestimates pump energy consumption and carbon emissions by 60%. Results of the improved method corresponded well to directly measured energy consumption and energy consumption represented 0.07% of an office building's total energy consumption. Consequently, the overall energy consumption associated with RWH systems is a very minor fraction of total building energy consumption.     

负荷不确定性对三联供系统配置和经济性的影响

利用围绕代表日负荷的概率分布来描述所有负荷的不确定性,以年总费用期望值为目标函数,建立了三联供系统的优化模型.根据一实例,系统地研究了负荷不确定性对三联供系统配置和经济性的影响.结果表明,负荷不确定性对三联供系统核心设备的配置影响不大,对辅助设备影响较大;随不确定性的增大,三联供系统初投资和运行费用都有所增加,系统经济优势有所下降.     

楼宇级冷热电联产系统的应用分析

针对一种应用于楼宇的冷热电联产系统(CCHP),从一次能源节约率(FESR)和经济性出发,对不同的发电功率配置方案进行对比,并考查“用户负荷跟随”和“全负荷”两种运行策略。计算结果表明,全负荷运行方式具有较好的节能性和经济性,冷热电联产系统发电功率过小或过大都不能达到节能目的,系统投资回收期在一定容量范围内相对稳定。天然气价格和电价对于不同容量的冷热电联产系统具有较大影响,但选择合适的发电机装机容量的系统可以减小这些因素的影响。     

燃气内燃机与燃气轮机冷热电联产系统的比较

介绍了美国建筑燃气内燃机与燃气轮机冷热电联产系统的应用现状。从变工况下的热电效率和火用效率两个方面比较了MW级燃气内燃机和燃气轮机冷热电联产系统的技术性能,分析了两者在不同冷热电需求下的一次能耗。对1～3MW建筑冷热电联产系统,燃气内燃机具有明显的节能和经济效益,而燃气轮机联合循环适用于规模更大的系统。     

分布式天然气CCHP系统应用研究现状与前景

介绍了分布式天然气冷热电联供(CCHP)系统的国内外应用研究现状及系统设备种类,综述了目前CCHP系统在热力学研究、经济性研究以及应用优化研究中的主要方法和结论,分析了CCHP系统的应用局限和发展前景。     

Integration of distributed generation systems into generic types of commercial buildings in California

Distributed generation (DG) of combined cooling, heat, and power (CCHP) has been gaining momentum in recent years as an efficient, secure alternative for meeting increasing power demands in the world. One of the most critical and emerging markets for DG-CCHP systems is commercial and institutional buildings. The present study focuses analysis on the main economic, energy-efficiency, and environmental impacts of the integration of three types of advanced DG technologies (high-temperature fuel cells, micro-turbines, and photovoltaic solar panels) into four types of representative generic commercial building templates (small office building, medium office building, hospital, and college/school) in southern California (e.g., mild climate), using eQUEST as energy simulation tool. Detailed load profiles for the four commercial building types during times of peak electric and peak gas consumption were analyzed and complementary strategies to further increase overall building energy efficiencies such as energy efficiency measures (e.g., day lighting, exterior shading, improved HVAC performance) and thermally activated absorption cooling were also investigated. Results show that the high-temperature fuel cell (HTFC) performance is best matched with the hospital energy loads, resulting in a 98% DG capacity factor, 85% DG heat recovery factor, and $860,000 in energy savings (6 years payback). The introduction of thermally driven double-effect absorption cooling (AC) in the college building with HTFC reduces significantly the building electricity-to-thermal load ratio and boosts the heat recovery factor from 37% to 97%.