| Distributed Energy System(DES)is commonly installed as energy infrastructure of industrial parks to meet energy demand of industrial production and daily operation.The plan and design of DES system follows the rule of energy cascade utilization.As the development of waste heat recovery technologies,more and more low-grade waste heat can be recovered to improve comprehensive energy efficiency of DES system.The research on low-grade waste heat utilization and comprehensive evaluation of DES system is carried out according to the characteristic of energy demand and waste heat of the industrial park,which is characterized by Cloud Computing industry(so-called Cloud Computing industrial park).To begin with,based on the research status of industrial waste heat recovery for District Heating(DH),typical configuration of CCHP-DH system is proposed based on the combination of CCHP system and DH,which is illustrated step by step to show how to realize energy cascade utilization in industrial park.In the study of waste heat recovery,three types of optimal configuration of multi-waste heat sources are proposed and analyzed using thermodynamics method,i.e.multi-waste heat sources in serial,in parallel and in mixed arrangement.The distribution issue of low-grade waste heat on the heat-source side of DH system is analyzed mainly including the study of energy consumption and heat loss in the long-distance distribution.Besides,low-pressure steam is proposed to settle down peak-shaving issue of DH system based on low-grade waste heat recovery.Then,according to the current state of using multiple heat exchangers to recover multi-souce waste heat,a new heat exchange unit is designed with the function of recovering waste heat from multi-waste heat sources simultaneously and adjusting the number of waste heat sources and the area of heat exchange flexibly.Then,according to the investigation of the development status of DES projects in Chongqing,it is known that DES projects in industrial parks are experiencing rapid expansion.However,a large amount of low-grade industrial waste heat from industrial park has not yet been recovered in an effective way.Besides,based on the questionnaire in terms of space heating status,the will for DH and expected cost for DH etc.,the expectation and requirement of DH for residents living in Chongqing are acknowledged.Then,the challenge of developing DH in Chongqing is analyzed and the suggestion is proposed to develop waste heat driven DH preferentially for end-users in industrial park,which can be expanded to people living around the industrial park.Then,in the process of figuring out key issues of recovering multiple low-grade industrial waste heat for DH,low-grade industrial waste heat is identified and heat pump selection is carried out for seven heating conditions,respectively.The result shows by recovering all the low-grade industrial waste heat of industrial park of Case study will supply heating up to 135 MW.In the fourth heating condition,10 units of heat pumps at heating capacity of 9000 k W/unit are used for recovering the waste heat of cooling water of thermal power plant and 3 units of absorption refrigerators.The recovered waste heat can meet heating demand of buildings located in and near the industrial park based on energy consumption of 3090 kW for water pump and heat loss of 56.366 kW in water delivery by using water pipe.Besides,the amount of low-grade steam used for peak-shaving is analyzed.Then,two modes of low-grade waste heat recovery applied in CCHP-DH system and CHP-DH system is compared and analyzed.One is waste heat recovery for DH using compression heat pump and the other is waste heat recovery for DH using heat exchanger with the extraction of a certain amount of low-pressure steam.In terms of energy performance of,the former mode applied in CCHP-DH model performs better than the latter in the supply of power,industrial heat,district cooling and DH,however,comprehensive energy efficiency of the former mode is higher than the latter by 3.76%.The main reason is that compression heat pump consumes a certain amount of in the former mode.Besides,two modes of waste heat recovery perform similarly when applied in CHP-DH model.Then,THERMOPTIM software is applied to simulate DES system of Case Study in the form of CCHP-DH model.However,there are different energy demand groups of cooling,heating and DH in the process of the construction and operation of CCHP-DH system,so different scenarios are proposed,i.e.CCHP-DH,CCHP,CHP-DH and CHP,to carry out comparative analysis of 3E performance.Thus,comparative analysis can be used to trace 3E performance of DES project of Case Study from CHP model to CCHP-DH model,as well as to make a qualified reference for adjusting the energy output and price of DES project according to the renewed energy demand in the process of construction and operation.Finally,comprehensive evaluation system is established for DES project and Case Study is used to validate its rationality.The evaluation system includes comprehensive performance evaluation of DES project using Outside Boundary(OB)analysis and Inside Boundary(IB)analysis,and barrier evaluation of the sustainable development of project using Stakeholder Analysis,which is illustrated in detail as follows:1)Comprehensive performance evaluation: In OB analysis,three-dimension coordinate is established to show the general performance of DES system.It potentially shows more favorable and feasible option by comparing potential configurations of the project.As a result,V01 has the most favorable performance.In Inside Boundary(IB)analysis,relative 3E index is introduced to evaluate DES comprehensively considering 3E performance by transferring energy performance indicator and environmental performance indicator into economic performance indicator for the purpose of the unification of 3E performance indicators.IB analysis is beneficial to detect the process improvement precisely,and waste heat recovery has a promising impact on comprehensive performance of DES system.2)Barrier evaluation: interest-influence matrix of Stakeholder analysis is used to identify different stakeholders,i.e.core stakeholders,primary stakeholders and general stakeholders in life cycle of DES project.Consequently,the Owner/Operator of Power Plant,Primary Energy Provider and Power Grid Controller are identified to be core stakeholders during the life cycle in this DES project,so their interests should be seriously considered in each process of developing DES project. |
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