Experimental validation of a thermodynamic boiler model under steady state and dynamic conditions Elisa Carlon a,b,⇑ , Vijay Kumar Verma a , Markus Schwarz a , Laszlo Golicza a , Alessandro Prada b , Marco Baratieri b , Walter Haslinger a , Christoph Schmidl a a Bioenergy 2020+, Gewerbepark Haag 3, 3250 Wieselburg Land, Austria b Free University of Bozen-Bolzano, Universitätsplatz – Piazza Università 5, 39100 Bozen-Bolzano, Italy highlights  Laboratory tests on two commercially available pellet boilers.  Steady state and a dynamic load cycle tests.  Pellet boiler model calibration based on data registered in stationary operation.  Boiler model validation with reference to both stationary and dynamic operation.  Validated model suitable for coupled simulation of building and heating system. article info Article history: Received 2 July 2014 Received in revised form 6 October 2014 Accepted 7 October 2014 Available online 19 November 2014 Keywords: Pellet boiler Dynamic test method Building energy simulation HVAC boiler model Model validation abstract Nowadays dynamic building simulation is an essential tool for the design of heating systems for residen- tial buildings. The simulation of buildings heated by biomass systems, first of all needs detailed boiler models, capable of simulating the boiler both as a stand-alone appliance and as a system component. This paper presents the calibration and validation of a boiler model by means of laboratory tests. The chosen model, i.e. TRNSYS ‘‘Type 869’’, has been validated for two commercially available pellet boilers of 6 and 12 kW nominal capacities. Two test methods have been applied: the first is a steady state test at nominal load and the second is a load cycle test including stationary operation at different loads as well as tran- sient operation. The load cycle test is representative of the boiler operation in the field and characterises the boiler’s stationary and dynamic behaviour. The model had been calibrated based on laboratory data registered during stationary operation at different loads and afterwards it was validated by simulating both the stationary and the dynamic tests. Selected parameters for the validation were the heat transfer rates to water and the water temperature profiles inside the boiler and at the boiler outlet. Modelling results showed better agreement with experimental data during stationary operation rather than during dynamic operation. Heat transfer rates to water were predicted with a maximum deviation of 10% during the stationary operation, and a maximum deviation of 30% during the dynamic load cycle. However, for both operational regimes the fuel consumption was predicted within a 10% deviation from the experimental values. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction The recent EU policies encourage energy efficiency in heating systems and promote the use of energy from renewable sources [1,2]. In this framework small scale biomass combustion devices (boilers and stoves) are currently considered a promising technology to supply heating and domestic hot water for the resi- dential sector in Europe [3,4]. Because of the ongoing renovations of the residential building stock and because of the increasing pop- ularity of low-energy and passive houses, the demand is gradually shifting to small scale heating devices. Boilers are the core of hydronic central heating and domestic hot water supply systems. Hot water leaving the boiler is delivered to one or more space heat- ing circuits and to the hot water storage tank. The technology of biomass boilers is already well-established, with efficiencies reach- ing 90% and low emission factors [5]. Heat production can also be http://dx.doi.org/10.1016/j.apenergy.2014.10.031 0306-2619/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: Bioenergy 2020+, Gewerbepark Haag 3, 3250 Wieselburg Land, Austria. Tel.: +43 7416 5223859. E-mail address: elisa.carlon@bioenergy2020.eu (E. Carlon). Applied Energy 138 (2015) 505–516 Contents lists available at ScienceDirect Applied Energy journal homepage: www.elsevier.com/locate/apenergy