Simulation models and performance assessment of district heating substations

Development of new technologies and methodologies regarding district heating substation operational control strategies are increasingly found nowadays. At the same time a great number of modern buildings are provided with energy monitoring and control systems which supervise and collect operating data from different energy components. Accordingly, an exemplary district heating systems is being implemented in the city of Kortrijk in Belgium, as part of a demonstration zero-carbon neighborhood. This study deals with the energy performance assessment of one of the systems component -the consumer substationinstalled in this low-temperature district heating system. A comparative analysis of the energy performance with several existing district heating substations was carried out. Three different district heating substation models are set up (using TRNsys) for investigation of the gross energy use, energyefficiency and comfort issues. In order to evaluate the performance of the analyzed substations two scenarios concerning the space heating system (radiator or floor heating system) were considered. The study aims to investigate the impact of different operational circumstances on the performance of district heating substations. The study generate understandings for energy saving operational strategies to be developed. Results indicate that the design concept together with a suitable selection of the substation has an important impact on the energy performance of the entire system

Techno-Economic Analysis of Rural 4th Generation Biomass District Heating

Biomass heating networks provide renewable heat using low carbon energy sources. They can be powerful tools for economy decarbonization. Heating networks can increase heating efficiency in districts and small size municipalities, using more efficient thermal generation technologies, with higher efficiencies and with more efficient emissions abatement technologies. This paper analyzes the application of a biomass fourth generation district heating, 4GDH (4th Generation Biomass District Heating), in a rural municipality. The heating network is designed to supply 77 residential buildings and eight public buildings, to replace the current individual diesel boilers and electrical heating systems. The development of the new fourth district heating generation implies the challenge of combining using low or very low temperatures in the distribution network pipes and delivery temperatures in existing facilities buildings. In this work biomass district heating designs based on third and fourth generation district heating network criteria are evaluated in terms of design conditions, operating ranges, effect of variable temperature operation, energy efficiency and investment and operating costs. The Internal Rate of Return of the different options ranges from 6.55% for a design based on the third generation network to 7.46% for a design based on the fourth generation network, with a 25 years investment horizon. The results and analyses of this work show the interest and challenges for the next low temperature DH generation for the rural area under analysis

On Making Judges Do the Right Thing

Denna rapport beskriver arbetet med att sammanställa ångförbrukande processer på Norrmejeriers Mejeri i Umeå som skulle kunna konverteras till fjärrvärmedrift. En del arbete har också lagts ner på att hitta förbättringsförslag på mejeriets ångsystem och beräkna nödvändig maxeffekt på en ny biobränsleeldad panna som är planerad att driftsättas före slutet på 2017. Processdata, som till stor del uppmätts av Sweco Systems för en energikartläggning av mejeriet, har använts till att undersöka 23 olika processer med en årlig energianvändning på ca 22 000 MWh. 11 av dessa processer har så låga temperaturkrav att fjärrvärme skulle kunna driva dessa året om, de anses därför vara mer lämpade för fjärrvärmedrift än de övriga. Dessa 11 processer har ett sammanlagt årligt energibehov på ca 15 000 MWh och hit hör bland annat uppvärmning av vatten till processer och tapp, värme till mejeriets ventilationssystem och förvärmning av nytt pannvatten. Resterande processer anses olämpliga att driva med fjärrvärme då kostnaden för att göra detta troligen blir högre än i dagsläget och en del av dessa processer enbart kan drivas med fjärrvärme en begränsad del av året. Till dessa processer hör värmning av mjölk och grädde vid några av mejeriets pastörer och återuppvärmning av diskvatten. I arbetet presenteras 3 olika förslag på hur fjärrvärmen kan kopplas in till undersökta processer. De två första förslagen ger framtida visioner om hur alla 23 undersöka processer kan konverteras till fjärrvärme. Det tredje förslaget visar däremot hur en fjärrvärmeanslutning kan se ut inom en snar framtid och i detta förslag ansluts endast de 11 mest lämpade processerna till fjärrvärmen. Det tredje förslaget användes till att göra en ekonomisk jämförelse mellan att värma processerna med ånga eller fjärrvärme. Det enda som jämfördes i beräkningarna var kostnaden för uppvärmning av processerna och ingen hänsyn togs till installationskostnader av fjärrvärmen eller den nya pannan. Beräkningarna visade att störst ekonomisk vinst kunde göras genom att använda sig av fjärrvärme för basbehovet och sedan toppa på detta med ånga när värmeförbrukningen var hög. Med ångproduktion i de befintliga pannorna skulle Norrmejerier kunna spara 1,8 miljoner kr/år med denna lösning. När den nya biobränslepannan installeras så sjunker däremot den möjliga besparingen till någonstans mellan 420 000- 860 000 kr/år. Förutom de besparingar som skulle kunna göras med en fjärrvärmeinstallation har flera förlustfaktorer identifierats i gångsystemet. Bland annat förloras ca 9 000 MWh årligen som flashånga eller genom att kondensat inte återförs till pannorna. Förbättringsförslag för att minska förlorade energimängder och effektivisera andra processer tas därför upp. Med nuvarande kostnadsbild på fjärrvärmen anses investeringskostnaden för denna inte väga upp den möjliga årliga besparingen efter att biobränslepannan konstruerats. Fjärrvärmen ses däremot som ett bättre miljömässigt alternativ och genom att installera fjärrvärme skulle maxeffekten på den nya biobränslepannan kunna minskas. Hur maxeffekten på den nya pannan bör dimensioneras vid en möjlig fjärrvärmeinkoppling och vid olika effektiviseringsförslag diskuteras därför också.This report describes the work of compiling steam consuming processes that could be converted to district heating in the dairy plant Norrmejerier in Umeå. Some work has also been put into finding possible improvement for the dairy's steam system and calculating the necessary maximum output of a new biofuel boiler that is to be built before the end of 2017.   Process data, which has been gathered by Sweco systems for an energy audit of the dairy, has been used to further investigate 23 different processes with an annual energy consumption of approximately 22 000 MWh. 11 of these processes have such low temperature requirements that district heating could be utilized to power them throughout the whole year. These 11 processes are those considered most suitable for a district heating installation and they have an annual energy consumption of about 15 000 MWh. The processes include heat to process- and tap-water, preheating new boiler water and heat to the dairy’s ventilation. The remaining processes are considered less suitable for a district heating installation since the cost of using district heating to power these probably would be more expensive than using self-produced steam. Some of these processes also have such high temperatures that district heating only could power them for a short period of the year. These processes include heating of milk and cream at some of the dairy's pasteurs and reheating dish water in the dairy’s dish system. Three different proposals for connecting the dairy to the district heating network have been suggested. Two of these proposals provide a futuristic vision for how Norrmejerier could connect district heating in the future to access all 23 investigated processes. The last proposal shows how a district heating installation could be utilized in the near future and in this suggestion only the 11 most suitable processes are connected.   The basic data from the last connection suggestion was used to make a financial comparison between district heating and self-generated steam for heating. The only thing compared in the calculations are the energy costs for heating and no consideration was taken to the installation costs of district heating or the new boiler. The calculations showed that the largest economical gain could be achieved by using district heating for the base load and then adding self-produced steam for peak loads. With steam productions in the current boilers Norrmejerier could save 1.8 million SEK annually with this solution. However, with the installation of a new biofuel boiler the possible savings drops to somewhere between 420 000 to 860 000 SEK/year. In addition to the savings that could be made with a district heating installation, several loss factors have been identified in the steam system. Among other things, about 9,000 MWh are annually lost as flash steam or condensate that disappears from the system. Suggestions to reduce losses in the system and improving energy use in different processes are therefore presented.   The possible savings that can be achived by installing district heating are not considered to be worth the big investment cost once the new steam boiler is installed. District heating is however seen as a better environmental option and by installing district heating the new boiler would be able to be constructed with a smaller maximum output, which would lower the installation costs. How suggested improvements to the steam system and a possible district heating installation would affect the new boiler is therefor also discussed

Thermal Transients in District Heating Systems

Heat fluxes in a district heating pipeline systems need to be controlled on the scale from minutes to an hour to adjust to evolving demand. There are two principal ways to control the heat flux - keep temperature fixed but adjust velocity of the carrier (typically water) or keep the velocity flow steady but then adjust temperature at the heat producing source (heat plant). We study the latter scenario, commonly used for operations in Russia and Nordic countries, and analyze dynamics of the heat front as it propagates through the system. Steady velocity flows in the district heating pipelines are typically turbulent and incompressible. Changes in the heat, on either consumption or production sides, lead to slow transients which last from tens of minutes to hours. We classify relevant physical phenomena in a single pipe, e.g. turbulent spread of the turbulent front. We then explain how to describe dynamics of temperature and heat flux evolution over a network efficiently and illustrate the network solution on a simple example involving one producer and one consumer of heat connected by "hot" and "cold" pipes. We conclude the manuscript motivating future research directions.Comment: 31 pages, 7 figure

Biofuels and Market Power - The Case of Swedish District Heating Plants

This paper tests for market power on the market for biofuels, employing a statistical model and making use of the idea of Granger causality. We use a panel data set of plant specific input prices and quantities of wood chip covering 91 Swedish district heating plants 1990-1996. If quantity Granger causes price, it is taken as an indication of market power. We find that the Swedish district heating plants to some degree have market power in the market for wood chips.market power; Granger causality; VAR; biofuel; district heating

Challenges in Energy Awareness: a Swedish case of heating consumption in households

An efficient and sustainable energy system is an important factor when minimising the environmental impact caused by the cities. We have worked with questions on how to construct a more direct connection between customers-­‐citizens and a provider of district heating for negotiating notions of comfort in relation to heating and hot tap water use. In this paper we present visualisation concepts of such connections and reflect on the outcomes in terms of the type of data needed for sustainability assessment, as well as the methods explored for channelling information on individual consumption and environmental impact between customers and the provider of district heating. We have defined challenges in sustainable design for consumer behaviour change in the case of reducing heat and hot water consumption in individual households: (1) The problematic relation between individual behaviour steering and system level district heating, (2) The complexity of environmental impact as indicator for behaviour change, and (3) Ethical considerations concerning the role of the designer