Maarten Sourbron

Building models for model predictive control of office buildings with concrete core activation

Model predictive control (MPC) is a good candidate to exploit the energy cost savings potential of concrete core activation (CCA), while guaranteeing thermal comfort. A bottleneck for practical implementation is the selection and identification of the building control model. Using grey box models, this article studies the impact of model structure and identification data set on the MPC control performance for an office building with CCA. Results for a one-year simulation show: (1) a second-order model can achieve equal control performance as a fourth-order one, (2) inclusion of solar or internal gains in the identification data set improves the model accuracy in general, especially for the fourth-order models and (3) MPC with a second-order model reduces electricity consumption by 15% compared to a reference controller, hereby deploying information about past operative temperature prediction errors and this without the need for solar or internal gains predictions.

Sensitivity analysis of feedback control for concrete core activation and impact on installed thermal production power

Because concrete core activation (CCA) actively integrates building mass in the heating, ventilation and airconditioning system, the choice of control strategy and controller settings plays a decisive role in reaching both thermal comfort and low energy use. Although not capable of intrinsically taking into account the system dynamics, conventional feedback control is often applied in CCA buildings. Without prior knowledge, a sensitivity analysis of the main control parameters highlights the basic characteristics a CCA feedback controller should have, taking energy use and thermal comfort as performance indicators. The best result is achieved by controlling the CCA surface temperature as a function of the ambient temperature, while transients are avoided to ensure an adequate performance with a low installed production power. Further data-analysis reveals the intrinsic controller behaviour of keeping the CCA core temperature during the whole year around 1°C higher than the lower thermal comfort temperature.

Determination of heat transfer characteristics of solar thermal collectors as heat source for a residential heat pump

One of the best ways of making efficient use of energy in residential units is to use heat pump. Heat pump performance can be further enhanced by integrating a solar thermal unit to provide hot water and subsidize space heating. This paper presents numerically examined energy feasibility study of a solar driven heat pump system for a low energy residence, where a flat plate solar collector served as the sole low temperature heat source. A parametric study on the ambient-to-solar fluid heat transfer coefficient has been conducted to determine the required solar collector heat transfer characteristics in this system. Solar collector area and storage tank volume were varied to investigate their impact on the system performance. A new performance indicator availability was defined to assess the contribution of the solar collector as low temperature energy source of the heat pump. Results showed that the use of a solar collector as low temperature heat source was feasible if its heat transfer rate (UA-value) was 200 W/K or higher. Achievement of this value with a realistic solar collector area (A-value) required an increase of the overall ambient-to-solar fluid heat transfer coefficient (U-value) with a factor of 6 to 8 compared to the base case with only natural convection heat exchange between solar collector cover and ambient.Copyright