2019-05-06

Simulation of a Large Heating Grid applied to the City of Dr. Peter Pechtl DI Thomas Knauss ENEXSA GmbH,

Agenda

. Concepts and Structure of the System • Evaluation Concept • Elements of the District Heating Grid  Existing Plants  Grid Extensions  Additional Heat Supply Options • Modelling of Various Plant Types  Degree of Modelling Detail  Calculation Procedure . Usage and Scenarios  Definition of Scenarios  Presentation of Results . Results and Evaluation

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Evaluation Concept

. Consider a complete year in hourly granularity . Balancing based on thermal energy streams (kWh) . Simplified model of the district heating grid . Each supply facility modelled in one module for high flexibility and accuracy . Time dependent thermal storage management . Results in form of EXCEL tables . System based on EBSILON®Professional Heat Balance Software

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Evaluation Concept cont‘d

. Balancing Areas • Grid divided into sub balancing areas • Heat supply and heat consumption and storage facilities are geographically assigned to the balancing areas • Connecting grid characterized by pumping limits and heat losses . Heat Sink / Heat Customers • Modelled based on historical data, correlated with ambient conditions; scaled by means of contractual supply duty (VAW Vertraglicher Anschlusswert) . Supply Facilities • Characterized using manufacturer data and measured historical data

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Existing Grid

. Assigned to Three Balance Areas . Balance Area #1 • Distribution Grid City of Graz • Thermal Solar Receivers Andritz and Liebenau • Waste Heat Recovery from Steel Mill Marienhütte . Balance Area #2 • District Heating Plant Graz (Gas fired boilers, FHKW Puchstrasse) • Solar Thermal Receivers AEVG . Balance Area #3 • District Heating Supply Pipeline Mellach-Puchstraße • Distributed Consumers along the DH Pipeline • CHP Mellach (modelled as simple Heat Supply) 5

Grid Extension: District Reininghaus

. Balance Area #4:

• Low Temperature Grid 68/43 • Connected to the main DH Grid of Graz • Heat Pump Marienhütte • Thermal Energy Storage (Lechthaler Speicher)

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Grid Extension: Project HELIOS

. Balance Area #5 • Thermal Storage Project HELIOS located at landfill site Neufeldweg • 2500 m³ Thermocline Thermal Storage • CHP from Landfill Gas • Power-to-Heat-Plant • Solar Thermal Receiver

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Grid Extension: DH Supply SAPPI

. DH Supply Paper Mill SAPPI

• Integrated into Balance Area #1

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Add‘l Facilities under Investigation

. Back-Up Boilers FHKW Puchstraße

• Gas fired warm water boilers

. Back-Up Boilers Waagner-Biro

. Heat Pump (s) Gössendorf

• Heat Source Sewage Treadment Plant Effluent

. Heat Pump Ice-Stadium Liebenau

. Bio Mass Boilers 9

Model Development using EBSILON

. Development of detailed physical models using manufacturer data, heat and mass balances and verification against measurements. . The grid model primarily considers energy flows but also considers main pump limits and heat losses and other limiting factors . Main model results are: • Supply duty, volumetric flow rates • Water supply temperature • Fuel and electricity consumption . …. Many more results are inherently available

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Model Development – Level of Detail

. Any desired level of detail is feasible using EBSILON®Professional … down to the unit operations (pumps, fans, heat exchangers) including loss items. Model of a heat supply plant comprising many Grid Model Model of a boiler different boilers

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Model Development – Various Plant Types

. Gas fired hot water boilers . Large gas fired steam boilers . CHP with Power-to-Heat device . Process heat extraction . Solar thermal plants . Heat pumps . Thermocline thermal stroage 2019-05-06

Model Development – Solar Thermal Plant

. Input Variables • Global Horizontal Irradiation • Ambient Temperature • Sun position due to date/time • Water supply temperature from characteristics . Model Calculation Basics • Sun position acc. to DIN 5034 • Radiation Modell acc. to Reindl, Beckman & Duffie • Conversion model similar to T*SOL® . Plant Characteristics • Geographic position and orientation • Angle corrections and heat transfer coefficients tuned to measurements

Sequence of Calculation

Importieren der Daten aus dem Excel- . Organized in three main simulation sequences Arbeitsblatt

1. Determination of the load range of each facility 1. Berechnungsschritt (parallelisiert) Server-Berechnungsdauer: 55 Minuten Min-, Max-Simulation plus productions costs PC-Berechnungsdauer: 53 Stunden

2. Berechnungsschritt Erstellen der Merit-Order 2. Determination of the Merit-Order, plant Server-Berechnungsdauer: 4 Minuten dispatch order, and storage management PC-Berechnungsdauer: 4 Minuten (instructions to load or unload) Berechnung des Dispatch

Speichermanagement 3. Detailed simulation of the entire year

according to the above determined dispatch 3. Berechnungsschritt (parallelisiert) Simulation laut Dispatch order Server-Berechnungsdauer: 25 Minuten PC-Berechnungsdauer: 24 Stunden

Exportieren der Ergebnisse in das Excel- Arbeitsblatt 14 2019-05-06

Creation of a Scenario

. Main simulation parameter input by means of EXCEL Tables. . Scenarios are defined by : • Consumption profile according to a reference year • Level of consumption defined by contracted duties (VAW) • Profile of ambient temperatures, which defines # of Heating Grade Days (Heizgradtage) • Availability of production plants • Min- / Max water flow rates • Variation of prices of gas and electricity . Scenarios can be calculated locally on a PC (80+hrs) but also uploaded to the server cluster of ENEXSA (80+minutes)

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Evaluation of Scenarios

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Display of Results

. EXCEL-Based Report (23 pages). . Report contains Inputs, Assumptions, and Results: • Ambient Conditions • Grid Conditions • Plant Availabilities and Dispatch • Heat Supply per Plant • Cost of Energy and Heat Supply Prices • Supply Facilities Operating Hours • Customized Reports for Complex Systems

 Reininghaus, Project HELIOS

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Display of Results

. Graphical Display of the Load State for Storage • Project HELIOS:

 Thermocline Storage  Operated at weekly frequency • Lechthaler Storage (Reininghaus):

 The operating target is to minimize operating hours of the heat pumps.

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Selected Results from 2017

. In 2015 simulated year 2017 for planning purposes with a model tuned to 2015 as a reference year . In 2018 simulated 2017 using 2015-Model exposed to actual conditions of 2017 (VAW, Ambient) . Simulated 2017 using conditions of 2017, fine tuned model to measurements (performance adjustments due to degradation)

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Evaluation Solar Thermal Plant Andritz

. Simulated heat supply duty and dispatch are in very good agreement with real plant operation . Model correctly predicted heat supply duty, merely based on input ambient conditions (Temperature, GHR), no manual intervention required. . The physical model gives a good representation of the real plant.

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Evaluation Heat Recovery Marienhütte

. Measured heat duty 2017 significantly deviated from the planning calculation . Deviation in January due to cooler ambient temperatures in 2017 compared to 2015 . In 2018 simulated 2017 using 2015-Model exposed to actual conditions of 2017

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Evaluation Heat Recovery Marienhütte

. Model suggested dispatch is in good agreement with real dispatch . Model (Status 2013) suggests appr. 18% higher heat duty than actually recorded in 2017. . To make the model match actual duty, plant performance had to be reduced (HX Effectiveness) -> 2017-Model . Further investigation of performance was conducted at the site. . Excessive HX fouling was confirmed

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Summary and Conclusions

. The successful development of a detailed thermodynamic simulation model for a complex district heating grid was presented . Some physical effects of the grid were considered (e.g. pumping limits or minimum grid pressure requirements) . The combination of detailed production facilities models with limited grid hydraulics enables modelling of the entire grid . The model enables the yearly simulation of the district heating grid of Graz in hourly granularity with high accuracy

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Summary and Conclusions

. The simulation results exhibited very good agreement with real plant operation with respect to consumption and production duties . The developed merit order simulated the facility dispatch and associated operating hours quite well. . Modelling of numerous future demand scenarios, combined with additional supply facilities of any type have been carried out successfully. . Many investigated grid extensions were implemented and operate as predicted. . The developed merit order concept will be implemented into the DCS (Leitsystem) for real time support of dispatch decisions

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DANKE! Energy Expert Software Applications

ENEXSA GmbH Parkring 18, 8074 -, Austria T: +43 (316) 400 9800 [email protected] www.enexsa.com