Dynamic heating control in power and energy reduction and renovation of multifamily apartment buildings

Abstract

Energy renovation involves retrofitting existing buildings with energy-efficient technologies and introducing practices to reduce energy consumption, peak power, and greenhouse gas emissions. To support the renovation targets, this study has two objectives. First, it sought to conduct a comprehensive investigation of how dynamic heating control systems can reduce heating energy and power needs in existing buildings. This entailed evaluating the impact of reducing HC temperatures, developing a dynamic heating control algorithm, and integrating flow limiters into the heating system to enhance energy performance. Although there have been high expectations of potential energy savings achievable through dynamic heating control, our study revealed that actual energy savings may not be realized. However, significant reductions in peak power needs were quantified. This led to a study of sizing conditions to ascertain the extent to which smaller heat exchangers could be employed by implementing capacity limits through flow control. Second, the dissertation aimed to assess the efficacy of Finnish renovation practices based on Asumisen rahoitus ja kehittämiskeskus (ARA) renovation subsidies. This involved evaluating the effects of implementing various renovation packages on energy consumption in typical residential buildings in Finland, along with assessing the accuracy of Energy Performance Certificates (EPCs) and the actual energy savings achieved in the renovated buildings. Calibrated reference building simulation models validated with on-site measured data were used throughout the study.

In the heating control analysis, lowering the HC temperatures resulted in a marginal energy saving of 0.6 kWh/m²a (equivalent to 0.8% of Space Heating (SH) energy) while maintaining the indoor air temperature at 21°C, revealing the almost nonexistent potential for energy savings. The developed dynamic control algorithm, enabling a reduction of the HC during domestic hot water peaks, led to a significant power reduction of more than 10% without compromising indoor air temperature. The introduction of the primary side flow limit reduced the heating sizing power and DH mass flow rate by 5.5% and 12.4%, respectively, under designed outdoor temperature conditions, enabling a more efficient use of DH system capacity.

In the analysis of common renovation packages based on heat pumps and window replacements, it was noticed that official EPCs overestimated before the renovation energy use as well as energy saving by a factor of almost two because of heavily overestimated infiltration and ventilation. Renovations undertaken with ARA renovation grants generally showed good energy savings. However, typical support for about 25% of the total cost of shallow renovations dropped below 10% in a deep renovation, which was not economically feasible. These findings underscore the importance of enhancing the accuracy of EPCs in assessing energy performance.