While the potential of model-based control is recognized, the development of reasonably accurate models for control applications remains a challenging, cumbersome and time-consuming task. This paper proposes a systematic and generalizable approach – based on low-order control-oriented thermal network (RC) archetypes – for the development, testing and implementation of readily scalable control solutions for buildings. These archetypes, focusing specifically on control applications, can significantly facilitate assessing the effect of control strategies on energy efficiency and load management. Furthermore, this approach can also be used for characterization, design and testing of simple retrofit strategies. The utilization of RC-based archetypes for common types of zones (such as those heated/cooled with forced-air or radiant systems) is proposed. These simple models (often 1st to 4th order models suffice), can also be used for the control of residential buildings. For larger buildings, zonal models can be combined to form whole building models.

This paper presents a model of a wall with variable properties dedicated to modelling phase change materials (PCMs) in building envelopes. The model is implemented in the TRNSYS simulation tool and referred to as Type 3258. The 1-D conduction heat transfer equation is solved using an explicit finite-difference method coupled with an enthalpy method to consider the variable PCM thermal capacity. This model includes temperature-dependent thermal conductivity and PCM-specific effects like hysteresis and supercooling. The stability conditions are discussed and the algorithm implemented in TRNSYS is described. A numerical validation performed on wall test cases proposed by the International Energy Agency is presented, showing that the developed model is in agreement with reference models. The paper also discusses the impact of temporal and spatial discretization on the model performance. Modelling problems encountered when using an effective heat capacity method (compared to an enthalpy method) and when representing supercooling are also discussed.

This paper presents the results of experimental tests performed on a wall section equipped with phase change materials (PCM). The wall is quickly transferred between cold and warm enclosures to observe the PCM behavior when melting or solidification is interrupted. A 1-D model of the wall based on the enthalpy method is used to identify the enthalpy curves that provide the best fit to experimental data. Results show that the PCM experiences a quick transition between different enthalpy curves when the heat flow direction (heating or cooling) is reversed during phase-change. According to our experiments and to the comparison with the 1-D model, the PCM investigated here follows an enthalpy curve that is very close to the heating curve when a cooling process is interrupted during solidification. If a heating process is interrupted during melting, the PCM follows an enthalpy curve that is located between the heating and cooling curves. This information is important to develop models for PCM used in buildings and further work is required to assess the impact of different factors on the transitional behavior

This paper presents a general methodology to model and activate the energy flexibility of electrically heated school buildings. The proposed methodology is based on the use of archetypes of resistance–capacitance thermal networks for representative thermal zones calibrated with measured data. Using these models, predictive control strategies are investigated with the aim of reducing peak demand in response to grid requirements and incentives. A key aim is to evaluate the potential of shifting electricity use in different archetype zones from on-peak hours to off-peak grid periods. Key performance indicators are applied to quantify the energy flexibility at the zone level and the school building level. The proposed methodology has been implemented in an electrically heated school building located in Québec, Canada. This school has several features (geothermal heat pumps, hydronic radiant floors, and energy storage) that make it ideal for the purpose of this study. The study shows that with proper control strategies through a rule-based approach with near-optimal setpoint profiles, the building’s average power demand can be reduced by 40% to 65% during on-peak hours compared to a typical profile.