From hospital to municipal cogeneration systems: an Italian case study

A mixed integer linear programming model combined with a more traditional design by scenarios is proposed to optimize facilities size and operation mode of a municipal energy system involving significant civil centres and a hospital. Moving from the need of a new heat and power station for the local hospital due to the construction of new pavilions, the opportunity of involving other centres in the neighbourhood in a distributed cogeneration system is analysed, increasing system complexity step by step. Smaller cogeneration units tailored to hospital needs are rewarding ventures with relatively low risks but, in a country whose traditional power generation systems heavily rely on fossil fuels and where energy policy and market conditions can make it profitable to sell surplus power, district heating systems foster the installation of larger cogenerators and lead thereby to higher profits and to better performance as for primary energy savings and greenhouse gases emission reduction. Copyright © 2006 John Wiley & Sons, Ltd.     

Modelling and optimization of district heating and industrial energy system—an approach to a locally deregulated heat market

Regions with densely concentration of industries and district heating systems (DHS) could be interesting study object from the light of an integrated heat market on local basis. System analysis with a widened system boundary could be used as an approach to evaluate the benefit of an integrated heat supply system. In this study, an energy system model consisting of totally seven different participants is designed and the optimization results of the system analysis are presented. With applied data and assumptions, the study shows that a significant amount of the heat demand within two sub‐systems can be covered by heat supply from the heat market (the entire heat comes from two industries). Shadow prices, which can be used for heat pricing, indicate the advantage of an integrated system. The system cost reduction through integration and the availability of several actors with diverse energy supply system, makes the region under study an interesting area to prove a locally deregulated heat market. Copyright © 2004 John Wiley & Sons, Ltd.     

On cost‐effective technical measures to avoid environmental damages of regional energy systems

The production of heat and electricity can cause large environmental impacts and, hence, large costs for society. Those are costs that are seldom taken into consideration. An important question is how the future technical energy systems should be formed if environmental costs were considered as any other good or service, such as raw material, capital and labour. This study comprises cost‐effective technical measures when monetary values of external effects are included in an energy system analysis. It is an analysis of how the present energy system can for society be cost‐effectively reconstructed to be more sustainable. A regional energy system model has been developed to perform the study and it concentrates upon production of heat in single‐family houses, multi‐dwelling buildings, non‐residential premises and district heating systems. The analysis adopts a business economic perspective, using present prices of energy carriers, and a more socio‐economic perspective, in which external costs are included. The result of the analysis is the optimal mix of energy carriers as well as new and existing heating plants that minimizes the costs of satisfying a demand for heat. The results show that it is profitable to invest in new heating plants fuelled with woody biomass. Furthermore, the external costs arising with satisfying the demand for heat can decrease substantially, 60%, by carrying through with the investments that are cost‐effective according to the institutional rules valid today. When monetary values of external costs are taken into consideration, this number is additional 5‐percentage points lower. It is shown that if environmental costs are included it is more expensive to continue with business as usual than it is to reconstruct and run a more sustainable energy system. Copyright © 2002 John Wiley & Sons, Ltd.     

Optimization of energy plants including water/lithium bromide absorption chillers

In this paper a methodology for the optimal integration of water/lithium bromide absorption chillers in combined heat and power plants is proposed. This method is based on the economic optimization of an energy plant that interacts with a refrigeration cycle, by using a successive linear programming technique (SLP). The aim of this paper is to study the viability of the integration of already technologically available absorption chillers in CHP plants. The results of this alternative are compared with the results obtained using the conventional way of producing chilled water, that is, using mechanical vapour compression chillers in order to select the best refrigeration cycle alternative for a given refrigeration demand. This approach is implemented in the computer program XV, and tested using the data obtained in the water/LiBr absorption chiller of Bayer in Tarragona (Catalonia, Spain). The results clearly show that absorption chillers are not only a good option when low‐cost process heat is available, but also when a cogeneration system is present. In this latter case, the absorption chiller acts as a bottoming cycle by using steam generated in the heat recovery boiler. In this way, the cogeneration size can be increased producing higher benefits than those obtained with the use of compression chillers. Copyright © 2000 John Wiley & Sons, Ltd.     

太阳能冷热电联供分布式能源系统的研究

以太阳能应用为背景，讨论了能够实现独立建筑冷热电联供的两种分布式能源系统的原理。以太阳能作为唯一热源，用于加热气体工质，进行闭式Brdyton循环发电。其透平释放的余热通过余热制冷方式供冷或通过换热器直接供热．可实现独立建筑的冷热电联供。当把燃料电池系统和该热动力系统组合起来，则可实现白天和夜间连续的独立建筑冷热电联供。该系统不消耗化石能源，无污染，能源利用效率高，具有进一步理论研究的价值和推广应用潜力。     

热电联产的节能效益分析——以乌鲁木齐市沙依巴克区热网工程为例

乌鲁木齐市的能源结构目前以煤为主,人均耗煤约3.96 t,位居中国城市人均耗煤量第一位,是中国人均耗煤量的近4倍。乌鲁木齐市冬季大气污染是典型的＂煤烟型＂污染。以乌鲁木齐市沙依巴克区热网工程为例,叙述了乌鲁木齐实行热电联产节能的情况,提出了发展热电联产是改善乌鲁木齐市大气环境、实现资源节约型、环境友好型社会的有效途径。     

Modeling an industrial energy system: Perspectives on regional heat cooperation

Through energy efficiency measures, it is possible to reduce heat surplus in the pulp and paper industry. Yet pulp and paper mills situated in countries with a heat demand for residential and commercial buildings for the major part of the year are potential heat suppliers. However, striving to utilize the heat within the mills for efficient energy use could conflict with the delivery of excess heat to a district heating system. As part of a project to optimize a regional energy system, a sulfate pulp mill situated in central Sweden is analyzed, focusing on providing heat and electricity to the mill and its surrounding energy systems. An energy system optimization method based on mixed integer linear programming is used for studying energy system measures on an aggregated level. An extended system, where the mill is integrated in a regional heat market (HM), is evaluated in parallel with the present system. The use of either hot sewage or a heat pump for heat deliveries is analyzed along with process integration measures. The benefits of adding a condensing unit to the back-pressure steam turbine are also investigated. The results show that the use of hot sewage or a heat pump for heat deliveries is beneficial only in combination with extended heat deliveries to an HM. Process integration measures are beneficial and even increase the benefit of selling more heat for district heating. Adding a condensing turbine unit is most beneficial in combination with extended heat deliveries and process integration. Copyright © 2007 John Wiley & Sons, Ltd.     

国外热电冷三朕产的现状和前景_热电联产工程系列报告之四

本文在前面三个系列报告［１～３］的基础上．着重讨论热电联产工程及技术的新发展──热电冷三联产．对热电冷三联产的基本概念和应用实例进行了介绍。对国内有关工作作了评述和展望。     

区域供热技术在希腊国内供热中的有效应用

希腊的区域供热始于1994年，采用热电联产技术向用户供热。预计目前在建项目完成以后，总装机容量将超过300MW，其中约85％为现有燃煤机组，其余16％主要是烧柴油和液化石油气的调峰机组。目前用户数量已超过25000户，供热建筑超过6000幢。由于区域供热价格具有竞争力，且初始投资成本低，所以时希腊而言尤其具有吸引力。随着希腊能源市场自由化以及输气管线的完善，区域供热技术将在能源和环保领域产生更大的效益。     

A district heating system based on absorption heat exchange with CHP systems

In order to decrease the energy consumption of large-scale district heating systems with cogeneration, a district heating system is presented in this paper based on absorption heat exchange in the cogeneration system named Co-ah cycle, which means that the cogeneration system is based on absorption heat exchange. In substations of the heating system, the temperature of return water of primary heat network is reduced to about 25°C through the absorption heat-exchange units. In the thermal station of the cogeneration plant, return water is heated orderly by the exhaust steam in the condenser, the absorption heat pumps, and the peak load heater. Compared with traditional heating systems, this system runs with a greater circuit temperature drop so that the delivery capacity of the heat network increases dramatically. Moreover, by recovering the exhausted heat from the condensers, the capacity of the district heating system and the energy efficiency of the combined heat and power system (CHP system) are highly developed. Therefore, high energy and economic efficiency can be obtained.     

A life cycle energy assessment for biogas energy in Serbia

The aim of this paper was to present the energy flows in the life cycle of biogas utilization systems (cogeneration and transportation), as well as their mutual relations, starting from providing the feedstock for digestion through to end-of-life management of biogas system as fertilizer on agricultural land. This study was carried out through the energy analysis of two scenarios (biogas in cogeneration and biogas in transportation) using performance of Mirotin biogas plant (1 MW) in Serbia. Results obtained in this study have shown that the analyzed scenario (biogas in cogeneration and biogas in transportation) have positive energy balances (52,114 and 53,585 GJ) and these scenarios are sustainable from energetic point of view.     

Turbine inlet cooling with thermal energy storage

Turbine inlet cooling (TIC) is a common technology used to increase combustion turbine power output and efficiency. The use of mechanical or absorption chillers for TIC allows for more air cooling than evaporative methods and also imposes a significant parasitic load to the turbine. Thermal energy storage (TES) can be used to shift this load to off‐peak hours. Use of thermal storage increases the flexibility of turbine power output, which benefits from the application of optimization tools. This paper explores the effect of combining TIC with TES to enhance the performance of a district cooling system that includes a gas turbine for power generation. The work illustrates how the system's performance can be enhanced using optimization. Application of multi‐period optimization to the system that includes TES brings significant operational cost savings when compared with a system without thermal storage. It is also shown how TES provides demand‐side energy management in the district cooling loop and supply‐side management through the use of TIC. In addition to the optimization study, a thorough literature review is included that describes the current body of work on combining TIC with TES. Copyright © 2013 John Wiley & Sons, Ltd.     

Some aspects of the use of solar energy in Serbia

This article presents the aspects of solar radiation and the use of solar energy in Serbia. It also considers why Serbia does not use thermal conversion of solar radiation in spite of much greater potential comparing to the countries of the Western and Central Europe, which are leading in the use of solar energy. The low standard of living, low electricity prices, the low level of energy efficiency in all areas of energy use, lack of knowledge, and political decisions are the main causes of insufficient use of renewable energy sources in Serbia.     

Thermoeconomic operation optimization of the Hellenic Aspropyrgos Refinery combined-cycle cogeneration system

Hellenic Aspropyrgos Refinery (HAR) is a state-owned petroleum refinery with a capacity of 130,000 barrels per day. The electric and part of the thermal loads of HAR are covered by a combined-cycle cogeneration plant of 54 MW_e capacity, which is interconnected with the utility grid. The plant consists of two gas-turbine generators, two exhaust-gas boilers, four fuel-oil boilers and one steam-turbine generator. Steam is produced at four levels; high, medium, low and very low pressure. Low-sulphur fuel oil is burned in the boilers, while the gas turbines can operate in any one or in a combination of (a) diesel oil, (b) process-generated fuel gas. (c) a mixture of propane and propylene (LPG). Connection to the utility network allows for importing additional electricity, if there is need, or for exporting excess electricity. Due to the variety of sources which can be used to cover the loads, the interdependency between sources and the variation of technical and economic conditions with time, questions such as the following arise. Given the technical (e.g. needs in electricity and heat), environmental and economic conditions at any instant of time, what source and at what load should be used? Which is the quantity of electricity bought from or sold to the utility grid? In order to answer these questions, an optimization procedure has been developed which is supported by a thermoeconomic analysis of the system and modelling of the performance of the main components. The minimization of the operation expenses has been selected as the objective function. A computer program has been developed for the numerical solution of the optimization problem. In the present work, the optimization procedure and the computer program are described, numerical results are presented which show the importance of applying such a procedure to real-world complex systems, a sensitivity analysis with respect to important parameters is performed and conclusions are drawn regarding the usefulness and further improvements of the program.     

斯特林发动机在能源利用领域中的应用

斯特林发动机具有燃料多样性、效率高等特点,对于促进能源的综合利用、减少环境污染具有重要的意义。提出了斯特林发动机推广应用的领域,并通过与燃气锅炉在初投资和运行费用方面进行比较,分析了斯特林发动机未来的发展趋势。     

Proliferation of district heating using local energy resources through strategic building-stock management: A case study in Fukushima,Japan

District heating systems using cogeneration technology and renewable resources are considered as an effective approach to resources conservation and reduction of greenhouse gas (GHG) emissions. However, widespread aging and depopulation problems, as well as the popularization of energy-saving technologies in buildings, are estimated to greatly decrease energy consumption, leading to inefficiency in district heating and barriers to technology proliferation. From a long-term perspective, land use changes, especially the progression of compact city plans, have the potential to offset the decrement in energy consumption that maintains the efficiency of district heating systems. An integrated model is developed in this paper based on building cohort analysis to evaluate the economic feasibility and environmental impact of introducing district heating systems to a long-term compact city plan. As applied to a case in the Soma Region of Fukushima, Japan, potential migration from the suburbs to the central station districts is simulated, where district heating based on gas-fired cogeneration is expected to be introduced. The results indicate that guided migration to produce concentrated centers of population can substantially increase the heat demand density, which supports a wider application of district heating systems and better low-carbon performance. These results are further discussed in relation to technology innovation and related policies. It is concluded that policies related to urban land use planning and energy management should be integrated and quantitatively evaluated over the long-term with the aim of supporting urban low-carbon sustainable development.     

Effect of apartment building energy renovation on hourly power demand

ABSTRACT

Optimal energy renovations of apartment buildings in Finland have a great impact on annual energy demand. However, reduction of energy demand does not necessarily translate into similar changes in peak power demand. Four different types of apartment buildings, representing the Finnish apartment building stock, were examined after optimal energy retrofits to see the influence of retrofitting on hourly power demand. Switching from district heating to ground-source heat pumps reduced emissions significantly under current energy mix. However, the use of ground-source heat pumps increased hourly peak electricity demand by 46–153%, compared to district heated apartment buildings. The corresponding increase in electrical energy demand was 30–108% in the peak month of January. This could increase the use of high emission peak power plants and negate some of the emission benefits. Solar thermal collectors and heat recovery systems could reduce purchased heating energy to zero in summer. Solar electricity could reduce median power demand in summer, but had only a little effect on peak power demand. The reduction in peak power demand after energy retrofits was less than the reduction in energy demand.     

Optimal unit sizing of cogeneration systems under the toleration for shortage of energy supply

The paper investigates the influence of tolerating the shortage of energy supplies on the economy of cogeneration systems in consideration of energy demands as random variables. To make a reasonable investigation into the influence, an optimal unit sizing method proposed by the authors is adopted after it is extended to this case so that it enables probability distributions of energy demands to be considered. In the method, equipment capacities and maximum contract demands of utilities such as electricity and natural gas are determined so as to minimize the expected value of the annual total cost in consideration of operational strategies for all the estimated energy demands under the toleration for the shortage of energy supplies. Numerical studies are carried out on cogeneration systems installed in a hotel or an office building with changing shortage rates of energy supplies as parameters. Through the studies, it is found that the expected systems' economy is improved even if the shortage rates of energy supplies are very small, and that the improvement for the office building is larger than that for the hotel. Copyright © 2000 John Wiley & Sons, Ltd.     

Chosen set of capital investments can greatly influence energy service tariff levels

The present centralised approach on very small islands does little to advance any kind of coordinated strategy for rationalising demand and factors of energy supply; the end-users are left to their own devices with little or no real sense of direction. This paper questions the current energy systems on such islands, and takes the Channel Island of Guernsey as a case situation, and suggests that by changing the system a net ‘gain’ of value may result. Great care needs to be exercised when making comparisons between the cost of centralised generation and the cost of alternative generation; centralised utility cost disclosures usually enjoy the benefit of substantial written down capital investment. A more appropriate comparison would be between the cost of new centralised power generation plant and the alternative methods of generation, which are also new. The question of occupacity, and whether the generator is a prime base-load supplier or not, also creates ‘unfair’ cost comparisons at times, and many false economics exist on this basis. This paper uses diurnal simulation of demand to bring clarity to these issues. © 1997 by John Wiley & Sons, Ltd.