Optimal Building Integration of District Heating Substations

Transcription

1 Optimal Building Integration of District Heating Substations Ph.D. project 10/2009 9/2012 Marek Brand DTU Civil Engineering 1 Workshop, May 19-20, 2010

2 Optimal Building Integration of District Heating Substations part of Zero Emission Buildings (ZEB) Work Package 2 on integration of building envelope with building service systems Objective: provide basis for development of intelligent systems for space heating (SH) and domestic hot water (DHW) heating for low energy buildings based on a supply of renewable energy from district heating systems Methods: design, analyses and evaluation of innovative solutions for DHW heating and Space Heating systems supplied by LEDH evaluation with advanced dynamic simulations of heat and mass transfer in DH substations, DHW installations and Space Heating systems. 2

3 District Heating in Denmark very much used in Denmark, in some areas obligate connection heat is produced in central plant and supplied by district heating water to end user end user has a substations for DHW heating and/or space heating (SH) advantages: reduced fuel consumption, CHP reduced CO 2 emissions, cleaning of flue gases use of waste heat alternative sources and waste incineration disadvantages: high initial cost heat loss in network what about future of district heating? (source 3

4 Low Energy Houses & Zero Emission Buildings WHY? environmental awareness CO 2 emissions - global warming 40% of energy used in buildings increasing prices of fossil fuels (run out of sources, env. taxes) Decrease energy demand of buildings building energy regulations low energy houses & ZEB Building regulations in Denmark: heat demand for a single family house with area 145m 2, including DHW heating (DHW due to DS 439 2,3 MWh/year) no regulation: XXX MWh pr. year 2008, BR08: 12 MWh pr. year 2010, LE2: 9 MWh pr. year 2015, LE1: 6 MWh pr. year heat demand of low energy buildings is much lower than traditional buildings 4

5 Is it suitable to supply low energy houses with DH? area with low energy houses lower heat demand higher heat loss in DHN traditional DH 80/40 C high heat loss not competitive solution: to decrease heat loss in network Low Energy District Heating (LEDH) use of twin pipes, better insulation, reduced pipe diameter (source LOGSTOR) decrease temperature of district heating water 50/20 C user 45 C increased ratio of renewable heat sources and waste heat there are still some questions and problems to solve 5

6 DHW heating by LEDH DHW 47 C below 60 C Legionella old fashion DHW systems reduce volume of DHW < 3 L (due to W551) no Legionella problem! 1, DHWSU Domestic Hot Water Storage Unit old concept 2, DHEU Direct Heat Exchanger Unit 3, DHWU new District Heating Water Unit no standing water! + individual pipe for each fixture, small pipe d 2 Direct Heat Exchanger Unit 3 District Heating Storage Unit (source 6

7 DHW heating by LEDH different thermo-dynamic behaviour compared to high temperature DH, i.e. heat transfer in heat exchangers, cooling of branch pipes, level of user comfort = waiting time for DHW (due to DS sec ) fulfilling of draw off profile and concurrency for DHW Solutions optimization of : by-pass solutions, set point temperatures branch pipes: twin/triple pipes, circulation, booster pump volume of buffer tank for DHWU concepts good, cheap and simple solution tank volume? 7

8 connection of Direct Heat Exchanger Unit, related to user comfort Traditional concepts By-pass solutions provide high level of comfort, but not optimal cooling of DH water Innovative concepts use of bathroom floor heating whole year supply-supply recirculation

9 LEDH for space heating in low energy buildings low temperature large surface space heating systems - floor/wall/ceiling or radiators? different floor composition high/low thermal capacity time constant low energy building are more sensitive to heat gains and proper control of space heating intelligent control system: reduce peaks from DH network thermal mass, weather forecast for heat demand prediction simultaneous running of SH and DHW heating will be affected thermal comfort of occupants? 9

10 Lystrup project LEDH pilot project in Lystrup/Aarhus low temperature network 50/25 C twin pipes 40 connected houses class 1 & 2 11 District Heating Water Units 29 Direct Heat Exchanger Units results for overall performance evaluation are already available but not related to user comfort 10 (source COWI)

11 Measurements of IHEU at DTU IHEU, used in Lystrup, supplied by LEDH (51 C) level of user comfort tap delay τ 42 C and τ 47 C Internal and external by-pass solution τ 47 C τ 42 C Time delay for external bypass (PTC2+P), when tapping is performed just before expected start of by-pass flow, set up on 35 C τ 42 C and τ 47 C just for IHEU is and 17 and 25 sec problems to fulfil suggested value for tap delay: 10 sec (DS439) 11

12 Numerical simulation of LEDH for space heating Low temperature space heating with reduced return temperature floor heating large surfaces radiators?... 50/30 C To shave peak loads for DH network intelligently controlled SH system with weather prediction floor heating importance of thermal mass Heat demand new and renovated houses not renovated houses? - over dimension of SH system - windows renovation - enlarge radiators 12

13 Thank you! District humor (source 13

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16 each phase = 6 months Phases of PhD project 1 st phase: state of the art of DH systems, identification of the problems, numerical simulation of Direct Heat Exchanger Unit type of substation + branch pipes and DHW building installations 2 nd phase: simulation of space heating systems in single family houses and their intelligent control 3 rd phase: District Heating Storage Unit (DHSU) in single family houses 4 th phase: optimization of combined solutions of substations for DHW and SH in single family houses 5 th phase: DHW and SH in multi-storey building connected to LEDH, using decentralised substations 6 th phase: guidelines for designing DHW heating and SH systems for buildings connected to LEDH 16

17 Low Energy District Heating Substations for multi-storey buildings Objectives: avoid circulation of DHW short tap delay (10 sec) small size of substation concurrency of draw off Solution: decentralised flat units consist of heat exchanger + possibility of using small buffer (30/40L) circulate district hot water easy control and measuring of heat consumption for each flat reduced noise propagation between storeys - no vertical pipes for SH (source 17

18 Simulations advanced numerical simulations of heat and mass transfer in SH and DHW systems in Matlab Simulink models include dynamic behaviour of service pipes, substation, and DHW installations in building Procedure set up model evaluate model with experimental data (from lab or real project) optimization of concept recommendations for manufacturer 18

19 LEDH for Domestic Hot Water heating Reduced temperature of DH water (from 70 C to 50 C) reduced temperature of DHW how much can be reduced? slower dynamic response of substation 10 sec tap delay Low Temperature DHW system low volume DHW systems < 3 L individual pipes to individual fixtures no circulation of DHW 19

20 Ph.D. project 10/2009 9/2012 Optimal Building Integration of District Heating Substations Ph.D student: supervisor: Marek Brand, DTU Civil Engineering, professor Svend Svensen DTU Civil Engineering co-supervisors: professor Bjarne W. Olesen DTU ICIEE Jan Eric Thorsen Danfoss Redan A/S Stephan Heessels Danfoss Redan A/S 20