Space Heating (SH) substations in District Heating-based (DH) systems are typically dimensioned at the design outdoor temperature without accounting for internal and solar heat gains. In residential ...buildings, the total required DH power typically also includes the need for Domestic Hot Water (DHW). This practice results in oversized substations and high DH design flow rates, which, due to heat gains and building thermal mass utilization in building operation, rarely, if ever, occur. Modern buildings maintain the desired indoor temperature with lower heating power by controlling the SH supply temperature with an outdoor-air-dependent heating curve and heating water flow with room unit thermostats. Applying a dynamic heating control algorithm can be considered one option to reduce the required DH power and optimize the DH network. Another possibility to decrease the needed power is controlling the DH flow by prioritizing DHW production and limiting the DH flow for SH. This study proposed a novel sizing method for the DH substation that quantifies the effects of dynamic control and flow limiters. Building models with detailed hydronic plants, accounting for internal heat gains, and using conventional and dynamic heating controls were developed in the IDA Indoor Climate and Energy simulation tool. The results show a potential DH side power reduction of up to 25%.
In this research, an existing building calibrated simulation model from 1981 was built based on measured energy and indoor temperature data. The model was used to study the central control's ...energy-saving potential. With parametric simulations, DHW circulation internal heat gain and ventilation airflow rate was determined as 85% and 0.29 l/s/m², respectively. DHW circulation heat loss has been found almost as high as DHW use. Dropping the heating curve from 70/40 °C to 65/35 °C resulted in a saving of 0.6 kWh/m²a (0.8% of space heating energy) on the cost of thermal comfort as yearly hours of the mean air temperature below 21 °C rose from 2.7% to 9.0%. It was necessary to reduce the heating curve to 55/25 °C in a hypothetical scenario with fully open thermostats, indicating heat redistribution from warmer to colder rooms, leading to higher heating energy. The findings indicate no energy saving potential due to compromising thermal comfort even by 5 °C heating curve reduction. It was revealed that the building average indoor temperature is not a factor to estimate energy-saving potential because of too low temperature in the coldest apartments.
Building energy efficiency, construction cost, life cycle cost, and carbon emission are the best interests of users, owners and different vendors. This study assessed the energy performance (EP) ...related investment and operational energy cost of Kouvola housing fair NZEB. Data from 12 new detached houses were collected, which fulfilled the energy certificate class of B according to the Finnish nearly zero energy building (NZEB) regulation. Besides, emission from building materials, construction and energy use during 50 years of one model building were estimated, aiming to compare the life cycle emission from wooden building, insulated concrete building, blockhouse and log house. The results showed that the total construction cost was independent to EP-value and even had a slightly negative correlation to the EP-value. The average EP-value of 12 buildings was slightly higher than that of buildings in Tampere housing fair 2012, which showed no improvement of nearly zero energy building (NZEB) guidelines since 2012. Energy performance related cost dependency in specific cost categories was shown so that EP-value improvement by 40 units increased less than 2% of construction cost. Electricity had a significant contribution to CO
2
emission while local district heating was based on renewables. Material emissions contribution was 32-48% of total emissions, and wooden buildings showed lower carbon footprint compared to other building structures.
This study investigated the effects of the dynamic heating control on power reduction and indoor air temperature in a typical Finnish block of apartments built in 1981. The building operated in 2018 ...with conventional and in 2020 with dynamic heating control. The onsite measured data was collected from both periods. Measured data enabled calibrating the whole building simulation models with an accuracy better than 10%. A new dynamic heating curve control algorithm was developed so that outdoor air compensated supply temperature was reduced during high use of Domestic Hot Water (DHW) by applying DHW compensation differential. If the indoor air temperature in any apartment dropped below the limit, supply temperature uplift was applied. The dynamic heating control resulted in 8.9% space heating and 13.7% total heating power reduction while had practically no effect on energy use. On the contrary, dynamic heating control slightly increased indoor temperature fluctuations, but both control systems resulted in a similar value of hours below the setpoint temperature of 21 °C. The results demonstrate that heating power reduction without compromising indoor air temperature is possible with applied supply temperature drop during DHW peaks and preheating afterwards.
This study analysed renovation measures implemented with ARA renovation subsidy in Finland in multifamily apartment buildings. Measured energy data was used to calibrate the energy simulation model ...of the most typical renovated building from the 1970 s. For the reference building, a comprehensive set of renovation packages were applied to assess the performance of ARA grants. It was noticed that official energy performance certificates (EPC) overestimated before the renovation energy use as well as energy saving by a factor of almost 2. It was notable that in calculated EPCs, after renovation, EP-value was higher than before renovation, EP-value based on measured energy use. The main reasons for faulty energy calculations were strong overestimations in the building leakage rate and ventilation airflow rate. Renovation packages reduced EP-value by 8 % to 27 %, including lighting and appliances. Those using district heat resulted in a small increase in electricity with a flat duration curve, but the combined ground source and exhaust air heat pump showed the highest peak electricity power increase by factor 6. Exhaust air heat pump, window replacement and photovoltaic were the most cost-effective options, while packages with additional insulation faced considerably higher costs than the sum of ARA support and monthly savings could cover bank loans; thus, ARA support was clearly too small to support deep renovation. The need to improve the accuracy of EPCs in assessing energy performance to facilitate more effective financial support was a finding that can be important for any support scheme to secure the necessary funding for renovation.
PDF
