Girts Vigants

District Heating Systems Performance Analyses. Heat Energy Tariff

Abstract The paper addresses an important element of the European energy sector: the evaluation of district heating (DH) system operations from the standpoint of increasing energy efficiency and increasing the use of renewable energy resources. This has been done by developing a new methodology for the evaluation of the heat tariff. The paper presents an algorithm of this methodology, which includes not only a data base and calculation equation systems, but also an integrated multi-criteria analysis module using MADM/MCDM (Multi-Attribute Decision Making / Multi-Criteria Decision Making) based on TOPSIS (Technique for Order Performance by Similarity to Ideal Solution). The results of the multi-criteria analysis are used to set the tariff benchmarks. The evaluation methodology has been tested for Latvian heat tariffs, and the obtained results show that only half of heating companies reach a benchmark value equal to 0.5 for the efficiency closeness to the ideal solution indicator. This means that the proposed evaluation methodology would not only allow companies to determine how they perform with regard to the proposed benchmark, but also to identify their need to restructure so that they may reach the level of a low-carbon business.

Modelling of the District Heating System's Operation

Modelling of the District Heating Systems Operation The development of a district heating systems calculation model means improvement in the energy efficiency of a district heating system, which makes it possible to reduce the heat losses, thus positively affecting the tariffs on thermal energy. In this paper, a universal approach is considered, based on which the optimal flow and temperature conditions in a district heating system network could be calculated. The optimality is determined by the least operational costs. The developed calculation model has been tested on the Ludza district heating system based on the technical parameters of this system. Centralizētās siltumapgādes sistēmas darbības modelēšana Latvijas klimatiskie apstākļi rada nepieciešamību pēc siltumenergijas piegādes. Tas jo īpaši attiecas uz centralizēto siltumapgādes sistēmu, kas ir galvenais risinājums lielo pilsētu siltumapgādē (~80% no siltumenergijas patērētājiem). Pēdējo 15 gadu laikā Latvijas centralizētā siltumapgā des sistēma ir piedzīvojusi izmaiņas, jo lielākajā daļā ēku ir uzstādītas apakšstacijas, lai apmierinātu pieprasījumu pēc siltumenergijas un karstā ūdens. Principā tā ir pāreja no viena veida kontroles uz citu, kas ļauj optimizēt siltumtīklu darbību. Izpētes ietvaros izstrādāts centralizētās siltumapgādes sistēmas aprēķina modelis, ar kuru var aprēķināt jebkuras pilsētas centralizētās siltumapgādes siltumtīklu optimālos plūsmu un temperatūru režīmus, pie kuriem ir zemākās ekspluatācijas izmaksas. Izstrādātais aprēķina mod elis ir pārbaudīts uz Ludzas siltumapgādes sistēmas, ņemot vērā šīs siltumapgādes tehniskos parametrus. Ludzas pilsētas siltumtīklu matemātiskā modelēšana veikta ar mērķi noteikt optimālu kvantitatīvi - kvalitatīvo regulēšanas sistēmu, ņemot vērā, ka Ludzas pilsētas siltumtīkli tika izbūvēti pirms 13 gadiem, kā arī matemātiskais modelis tika pielāgots jaunas siltumtrases izbūvei uz Ludzas pilsētas siltumtīklu bāzes. Ludzas siltumapgādes sistēma darbināšana teorētiski dod iespēju siltumnesēja pārvades izmaksas gadā samazināt par 13 % no kopējām siltumtrases ekspluatācijas izmaksām. Temperatūras grafika pazemināšana uzskatāma par ekonomiski pamatotu pasākumu, jo naudas līdzekļi, kas tiek ietaupīti līdz ar siltuma zudumu samazinājumu, pārsniedz izdev umus, kas radušies intensīvākas siltumnesēja cirkulācijas nodrošināšanai. Tas vienlaikus paver iespējas sistēmas efektivitātes paaugstināšanai dūmgāzu dziļai dzesēšanai siltumapgādes sistēmas katlumājā. VIII.

Modelling of Technological Solutions to 4th Generation DH Systems

Abstract Flue gas evaporation and condensing processes are investigated in a direct contact heat exchanger - condensing unit, which is installed after a furnace. By using equations describing processes of heat and mass transfer, as well as correlation coherences for determining wet gas parameters, a model is formed to create a no-filling, direct contact heat exchanger. Results of heating equipment modelling and experimental research on the gas condensing unit show, that the capacity of the heat exchanger increases, when return temperature of the district heating network decreases. In order to explain these alterations in capacity, the character of the changes in water vapour partial pressure, in the propelling force of mass transfer, in gas and water temperatures and in the determining parameters of heat transfer are used in this article. The positive impact on the direct contact heat exchanger by the decreased district heating (DH) network return temperature shows that introduction of the 4th generation DH system increases the energy efficiency of the heat exchanger. In order to make an assessment, the methodology suggested in the paper can be used in each particular situation.