Estimated and measured energy consumption for specific buildings

Abstract

The main topic of this thesis has been to study the relationship between the measured and estimated energy consumption of specific buildings, across different building energy performance and construction periods. The objective of the study is to find a way to minimise the discrepancy between the expected and measured energy consumption of the buildings. In chapter 2, the international literature study revealed that the measured energy consumption is expected to be more than the estimated figure for buildings with low energy demands, and less than the estimated value for buildings with high expected consumption. These conclusions have been examined using two DTU case studies, in which data on the expected and measured energy use in buildings 127 and 210 has been gathered. These case studies were also evaluated with respect to their estimated and measured energy use. Additionally, a dataset of all of the buildings at DTU has been supplied by the DTU Campus service. In chapter 3 the measurements are described, e.g., the measurements of outside temperature, inside temperature and energy consumption, as well as the measurements used to calculate and verify the expected energy use. The measurements were performed for a period of 29 days, from December 1 2016 to December 31 2016. During this period, the building used 43,15 kWh/m2/year for heating. The mean inside and outside temperatures were 22⁰C and 6⁰C. All of the measured results were compared with the estimated results. The energy estimation was performed using two methods, a simple formula and Be15 software. The comparisons resulting from these two methods show that, generally, the simple calculation overestimates energy consumption whereas Be15 underestimates it. In chapter 4, the measurements, calculations and Be15 results described in chapters 2 and 3 are given. Building 127’s total energy consumption for heating, cooling, ventilation, and domestic hot water use was calculated to be 55.5kWh/m2 per year, where 23.2 kWh/m2/year of the total is used for heating and 14.7 kWh/m2/year is used for cooling. According to the actual energy use found by the measurements, the building is not qualified to be included in the low energy class 15. For this building to qualify in this class, the actual energy use would need to be six times lower. For building 210, the actual energy use is 102.4 kwh/m2 per year. For this building to use the same amount of energy as was originally estimated by Birch & Krogboe A/S, the building and its users would need to reduce the actual energy use by 41.5%.