Low rate energy use for heating and in industrial energy supply systems—Some technical and economical aspects

The subject hereof are two typical examples of waste heat and low-temperature heat use and the objective is to evaluate economic effectiveness taking into account various boundary conditions. The first facility considered is an “earth-coupled” heat pump with direct evaporation used as a component of a heating system. The second is an industrial installation, based on a specific project to use waste heat from the cooling process. Alternatively, four different technical options have been considered, including the use of the compression heat pump, absorption heat pump, heat transformer (absorption) and combined system with a gas motor for driving the heat pump compressor. An original simple methodology for economic analysis evaluating uses of low-temperature heat sources as elements of energy supply systems has been developed using input data taken from actual research or industrial projects. The paper also offers a comparison between such energy supply systems operating under different economic conditions of Germany and Poland.     

工业余热跨季节储热系统优化及经济性分析

以工业余热跨季节储热用于区域供热系统为研究对象,在一个已有的1 MW工业余热系统的基础上,搭建工业余热跨季节储热系统设计方案,通过系统模拟对系统储热、取热过程进行分析。分析结果表明:工业余热跨季节储热适合长周期、大规模蓄热;储热体体积和循环流量应根据系统热源和取热装置特性进行合理匹配,在合理匹配范围内可参考系统经济性确定系统最优配置。最后,通过费用年值法分析优化后的系统经济性,分析表明工业余热跨季节储热用于区域供热成本仅略高于燃煤供热,相比燃气供热具有非常可观的经济性。     

Probabilistic aspects in the technical and economic analysis of the industrial waste heat recovery system generating useful heat and refrigeration

The technical and economic analysis of the industrial waste heat recovery system, considering probabilistic distribution of the input data is presented. A prospect and rationality of the application of the waste heat boiler and absorption refrigerator has been examined as an example, in view of covering integrated heat and refrigeration demands. The influence of changing ambient conditions as well as the exhaust gas temperature and its flow rate on the overall system performance has been simulated and assessed. Copyright © 2005 John Wiley & Sons, Ltd.     

Controller tuning of district heating networks using experiment design techniques

There are various governmental policies aimed at reducing the dependence on fossil fuels for space heating and the reduction in its associated emission of greenhouse gases. DHNs (District heating networks) could provide an efficient method for house and space heating by utilizing residual industrial waste heat. In such systems, heat is produced and/or thermally upgraded in a central plant and then distributed to the end users through a pipeline network. The control strategies of these networks are rather difficult thanks to the non-linearity of the system and the strong interconnection between the controlled variables. That is why a NMPC (non-linear model predictive controller) could be applied to be able to fulfill the heat demand of the consumers. The main objective of this paper is to propose a tuning method for the applied NMPC to fulfill the control goal as soon as possible. The performance of the controller is characterized by an economic cost function based on pre-defined operation ranges. A methodology from the field of experiment design is applied to tune the model predictive controller to reach the best performance. The efficiency of the proposed methodology is proven throughout a case study of a simulated NMPC controlled DHN.     

Energy harvesting, reuse and upgrade to reduce primary energy usage in the USA

Two-thirds of input energy for electricity generation in the USA is lost as heat during conversion processes. Additionally, 12.5% of primary fuel and 20.3% of electricity are employed for space heating, water heating, and refrigeration where low-grade heat could suffice. The potential for harnessing waste heat from power generation and thermal processes to perform such tasks is assessed. By matching power plant outlet streams with applications at corresponding temperature ranges, sufficient waste heat is identified to satisfy all USA space and water heating needs. Sufficient high temperature exhaust from power plants is identified to satisfy 27% of residential air conditioning with thermally activated refrigeration, or all industrial refrigeration and process heating from 100 to 150 °C. Engine coolant and exhaust is sufficient to satisfy all air conditioning and 68% of electrical demands in vehicles. Overall, this study demonstrates the potential to reduce USA primary energy demand by 12% and CO₂ emissions by 13% through waste heat recovery. A detailed analysis of thermal energy demand in pulp and paper manufacturing is conducted to demonstrate the methodology for improving the fidelity of this approach. These results can inform infrastructure and development to capture heat that would be lost today, substantially reducing USA energy intensity.     

Design of a seasonal thermal energy storage in the ground

Longterm storage of high quantities of thermal energy is one of the key problems for a widespread and successful implementation of solar district heating and for more efficient use of conventional energy sources. Seasonal storage in the ground in the temperature range of up to 90°C seems to be favourable from a technical and economical point of view. Preferably duct systems with vertical heat exchangers can be built in areas without ground water or low flow velocity compared with the geometry of the store and the storage period.

The thermal performance of such systems is influenced by the heat and moisture movement in the area surrounding the heat exchangers. Thermal conductivity and heat capacity are strongly dependent on the water content. This combined heat and moisture transport was simulated on the computer for temperatures up to 90°C. This model calculates the effective heat transfer coefficient and the heat capacity of the soil depending on water content, mineral composition, dry bulk density and shape of soil components. The computer simulation was validated by a number of laboratory and field experiments.

Based on this theoretical work a pilot plant was designed for seasonal storage of industrial waste heat. A heat and power cogeneration unit (174 kW_th) delivers waste heat during summer to the ground storage of about 15 000 m³ with 140 vertical heat exchangers of 30 m depth. About 418 MWh/a will be charged into the ground at a temperature level of 80°C, about 266 MWh/a should be extracted at temperatures between 40°C and 70°C and delivered directly to the space heating system. With this design an economic calculation gave energy prices of 39 US$/MWh which is of the same order as conventional energy prices.     

Industrial waste heat utilization for low temperature district heating

Large quantities of low grade waste heat are discharged into the environment, mostly via water evaporation, during industrial processes. Putting this industrial waste heat to productive use can reduce fossil fuel usage as well as CO₂ emissions and water dissipation. The purpose of this paper is to propose a holistic approach to the integrated and efficient utilization of low-grade industrial waste heat. Recovering industrial waste heat for use in district heating (DH) can increase the efficiency of the industrial sector and the DH system, in a cost-efficient way defined by the index of investment vs. carbon reduction (ICR). Furthermore, low temperature DH network greatly benefits the recovery rate of industrial waste heat. Based on data analysis and in-situ investigations, this paper discusses the potential for the implementation of such an approach in northern China, where conventional heat sources for DH are insufficient. The universal design approach to industrial-waste-heat based DH is proposed. Through a demonstration project, this approach is introduced in detail. This study finds three advantages to this approach: (1) improvement of the thermal energy efficiency of industrial factories; (2) more cost-efficient than the traditional heating mode; and (3) CO₂ and pollutant emission reduction as well as water conservation.     

Heat integrated heat pumping for biomass gasification processing

The main part of this paper is an industrial case study. It deals with an application of a heat pump in energy systems for biomass gasification in a wood processing plant. Process integration methodology is applied to deal with complex design interactions as many streams requiring heating and cooling are involved in the energy recovery. A refrigeration cycle maintains low temperature in the scrubber where the production gas (or synthesis gas–syngas) is cooled and undesirable contaminants are removed before the syngas is introduced into the engine. In addition to electricity generation, a large amount of waste heat is available in the biomass gasification system studied in the paper, and its appropriate heat integration with utility systems within a plant allows the available heat to be efficiently utilized for the site. The conceptual understanding gained from the case study provides systematic design guidelines for further process development and industrial implementation in practice.     

Industrial waste heat potential in Germany—a bottom-up analysis

Industrial waste heat may be one of the answers to future energy demands. Depending on the temperature, industrial waste heat may be used to produce electricity or meet cooling or heating demands at different temperature levels. However, in order to estimate the influence the waste heat may have in future energy systems, the magnitude of the industrial waste heat in the different countries need to be estimated. For Germany, so far, only top-down analyses of the waste heat potential exist, using key figures derived from other studies in other countries. In this paper, the first bottom-up approach for estimating the industrial waste heat potential in Germany is presented. For this approach, an algorithm to evaluate and test the mandatory emission report data from German production companies was developed. In a second step, round about 81,000 data sets have been evaluated to calculate a conservative and lower boundary value for the industrial waste heat. As this conservative, lower boundary based on the collected data from the German industry, the waste heat volume was evaluated as 127 PJ/a or 13 % of the industrial fuel consumption. Results were used to derive key figures with which the missing share of the data was approximated.     

An economic assessment of electricity for industrial space heating in the United Kingdom

The potential for increased use of electricity for space heating in industry in the United Kingdom is investigated. Two presently available technologies are considered the most likely candidates: electricaire (storage-based warm air heating on a restricted hour tariff) and air-to-air heat pumps. A simulation modeling approach is employed to examine the economic feasibility of the two electricity-based heating systems. The central component of the model is a simple industrial building with known thermal characteristics. The technical performance of the heating system installed in the model factory is assessed over the period of a year, while the economic performance is evaluated over the lifetime of the heating system. The economic competitiveness of electricaire and heat pump space heating is assessed by comparison with gas-fired warm air heating for different sizes of factory and shift patterns. The future prospects of the heating systems are examined under various scenarios. It is concluded that electricaire looks most favourable in small single shift factories because of its low capital cost, while heat pump heating looks most attractive in factories operating longer shifts, particularily if advantage can be taken of restricted hour tariffs. Greater penetration of heat pump heating systems is only likely if reductions in the capital cost of heat pumps and/or improvements in the coefficient of performance are achieved.     

北方采暖地区既有建筑节能改造问题研究

本文介绍了北方城镇建筑采暖能耗现状,分析了建筑采暖需要的热量、采暖系统的过量供热,以及热源和采暖系统的效率三大因素的状况和存在问题。对目前社会关注的我国建筑采暖的政策和技术的热点问题进行了专门讨论,对热计量和供热收费改革、天然气采暖、挖掘热电联产系统节能潜力、全面利用工业生产排出的低品位余热作为城市供热的主要热源等问题进行了分析研究。对2020年采暖的节能潜力进行了预测,并提出了全面推进供热体制改革的政策建议。     

Design of biomass district heating systems

The biomass exploitation takes advantage of the agricultural, forest, and manure residues and in extent, urban and industrial wastes, which under controlled burning conditions, can generate heat and electricity, with limited environmental impacts.Biomass can – significantly – contribute in the energy supplying system, if the engineers will adopt the necessary design changes to the traditional systems and become more familiar with the design details of the biomass heating systems.The aim of this paper is to present a methodology of the design of biomass district heating systems taking into consideration the optimum design of building structure and urban settlement around the plant. The essential energy parameters are presented for the size calculations of a biomass burning-district heating system, as well as for the environmental (i.e. Greenhouse Gas Emissions) and economic evaluation (i.e. selectivity and viability of the relevant investment). Emphasis has been placed upon the technical parameters of the biomass system, the economic details of the boiler, the heating distribution network, the heat exchanger and the Greenhouse Gas Emissions.     

Heat pumps and combined heat and power a technology assessment

This paper utilizes a novel system boundary and methodological framework for comparing the technical, economic and institutional factors affecting the development of advanced heating technologies. The focus is on the USA where electric heat pump technology has recently gained widespread acceptance; parts of the centralized combined heat and power (CHP) industry are in a state of decline; and a rapidly changing regulatory environment is stimulating development of small decentralized gas-fired CHP systems.     

Solid oxide fuel cell micro combined heat and power system operating strategy: Options for provision of residential space and water heating

Solid oxide fuel cell (SOFC) based micro combined heat and power (micro-CHP) systems exhibit fundamentally different characteristics from other common micro-CHP technologies. Of particular relevance to this article is that they have a low heat-to-power ratio and may benefit from avoidance of thermal cycling. Existing patterns of residential heat demand in the UK, often characterised by morning and evening heating periods, do not necessarily complement the characteristics of SOFC based micro-CHP in an economic and technical sense because of difficulties in responding to large rapid heat demands (low heat-to-power ratio) and preference for continuous operation (avoidance of thermal cycling). In order to investigate modes of heat delivery that complement SOFC based micro-CHP a number of different heat demand profiles for a typical UK residential dwelling are considered along with a detailed model of SOFC based micro-CHP technical characteristics. Economic and environmental outcomes are modelled for each heat demand profile. A thermal energy store is then added to the analysis and comment is made on changes in economic and environmental parameters, and on the constraints of this option. We find that SOFC-based micro-CHP is best suited to slow space heating demands, where the heating system is on constantly during virtually all of the winter period. Thermal energy storage is less useful where heat demands are slow, but is better suited to cases where decoupling of heat demand and heat supply can result in efficiencies.     

燃煤发电机组耦合余热利用技术研究进展

  目的  为实现燃煤发电机组进一步扩大其热电比的需求,结合原有机组特点耦合余热利用技术成为了有效方式之一。现有余热利用技术的适应特点以及调节能力具有较大差异。  方法  综合评述了几种余热回收利用方式,同时对比了其原理、优缺点,并通过介绍常用的评价指标进一步评述了当下余热回收技术的关注点。  结果  对于余热回收利用技术方式,目前主要有烟气余热回收,循环水余热回收,空气源余热回收,工业废气回收等方式。其温度区间分别为120～150 ℃、15～35 ℃、0～60 ℃、300 ℃以下。耦合余热利用技术的评价方法主要包括通过性能评价、经济性评价以及系统参数关联评价,其中以热耗、热效率等评价参数为主。  结论  文章给出了余热回收利用技术的发展方向及相关建议。耦合余热回收利用技术目前主要应用于热泵系统,在未来更高热电比需求下,采用冷端余热供热的低压缸改造技术将成为一大发展重点。     

径向热管换热器在天然气工业炉低温烟气中的应用

当前我国的能源形势紧张,能源利用状况令人担忧.在一些高耗能的企业,工业生产中排放的中低温烟气余热由于回收难度高、回收成本大等问题,一直得不到合理的利用,如何合理回收成为亟待解决的难题之一.简要介绍了一种新型余热利用换热设备——径向热管换热器,提出了计算热管换热器经济性评价指标的方法,并以某工厂低温烟气余热回收工程为实例,对烟气余热的回收利用进行了技术和经济效益分析.实践应用证明,径向热管换热器在工业低温烟气余热回收中有很好的实用性和可行性.     

An applied methodology for assessment of the sustainability of biomass district heating systems

In order to maximise the share of biomass in the energy supplying system, the designers should adopt the appropriate changes to the traditional systems and become more familiar with the design details of the biomass heating systems. The aim of this study is to present the development of methodology and its associated implementation in software that is useful for the design of biomass thermal conversion systems linked with district heating (DH) systems, taking into consideration the types of building structures and urban settlement layout around the plant. The methodology is based on a completely parametric logic, providing an impact assessment of variations in one or more technical and/or economic parameters and thus, facilitating a quick conclusion on the viability of this particular energy system. The essential energy parameters are presented and discussed for the design of biomass power and heat production system which are in connection with DH network, as well as for its environmental and economic evaluation (i.e. selectivity and viability of the relevant investment). Emphasis has been placed upon the technical parameters of biomass logistics, energy system's design, the economic details of the selected technology (integrated cogeneration combined cycle or direct combustion boiler), the DH network and peripheral equipment (thermal substations) and the greenhouse gas emissions. The purpose of this implementation is the assessment of the pertinent investment financial viability taking into account the available biomass feedstock, the economical and market conditions, and the capital/operating costs. As long as biomass resources (forest wood and cultivation products) are available and close to the settlement, disposal and transportation costs of biomass, remain low assuring the sustainability of such energy systems.     

内丘县工业余热用于集中供热

叙述了河北省内丘县供热发展的历史与现状以及采用工业余热集中供热在内丘县的可行性与整个系统的节能效益,指出,工业余热回收用于集中供热是缓解中国能源紧缺,促进对供热事业的有效途径.     

Power-to-hydrogen & district heating: Technology-based and infrastructure-oriented analysis of (future) sector coupling potentials

Numerous studies suggest that power-to-hydrogen (PtH₂) will take a decisive part in future sustainable energy systems. District heating (DH) networks are also assigned a crucial role for the overall efficiency of such. In this regard, heat flows resulting from PtH₂ may lead to synergies with the heat supply of DH systems.This paper discusses the potentials of PtH₂ as a relevant heat source for DH (with focus on Austrian system conditions). Technology-specific efficiencies, heat flows and temperatures are put in context with today's and future DH system specifications and synergies are analyzed. A qualitative analysis summarizes the opportunities and challenges that arise from a system perspective, e.g. electrolyzer location, user type, and user-specific operation (i.e. generation load).It is found that high-temperature electrolysis is likely to be fully integrated in industrial utility operations and heat utilization corresponds to the well-known challenges of integrating industrial waste heat into DH networks. The location of low-temperature electrolysis is subject to infrastructure limitations and the economics of utilizing by-products. Operation is likely to be more electricity-market-oriented and may seasonally differ from heat demand. However, its waste heat is sufficient to feed modern low-temperature DH networks and by 2030 could cover up to 12% of Austria's current DH demands and up to 4% of the EU demand for heat below 100 °C.     

Comparison of energy and exergy analysis of fossil plant,ground and air source heat pump building heating system

The energy and exergy flow for a space heating systems of a typical residential building of natural ventilation system with different heat generation plants have been modeled and compared. The aim of this comparison is to demonstrate which system leads to an efficient conversion and supply of energy/exergy within a building system.The analysis of a fossil plant heating system has been done with a typical building simulation software IDA–ICE. A zone model of a building with natural ventilation is considered and heat is being supplied by condensing boiler. The same zone model is applied for other cases of building heating systems where power generation plants are considered as ground and air source heat pumps at different operating conditions. Since there is no inbuilt simulation model for heat pumps in IDA–ICE, different COP curves of the earlier studies of heat pumps are taken into account for the evaluation of the heat pump input and output energy.The outcome of the energy and exergy flow analysis revealed that the ground source heat pump heating system is better than air source heat pump or conventional heating system. The realistic and efficient system in this study “ground source heat pump with condenser inlet temperature 30 °C and varying evaporator inlet temperature” has roughly 25% less demand of absolute primary energy and exergy whereas about 50% high overall primary coefficient of performance and overall primary exergy efficiency than base case (conventional system). The consequence of low absolute energy and exergy demands and high efficiencies lead to a sustainable building heating system.