Non-Destructive Possibilities of Thermal Performance Evaluation of the External Walls

Identification of the actual thermal properties of the partitions of building enclosures has a significant meaning in determining the actual energy consumption in buildings and in their thermal comfort parameters. In this context, the total thermal resistance of the exterior walls (and therefore their thermal transmittance) in the building is a major factor which influences its heat losses. There are many methods to determine the total thermal resistance of existing walls, including the quantitative thermography method (also used in this study). This paper presents a comparison of the calculated total thermal resistance values and the measured ones for three kinds of masonry walls without thermal insulation and the same walls insulated with expanded polystyrene boards. The measurements were carried out in quasi-stationary conditions in climate chambers. The following three test methods were used: the temperature-based method (TBM), the heat flow meter method (HFM) and the infrared thermography method (ITM). The measurement results have been found to be in good agreement with the theoretically calculated values: 61% of the measured values were within 10% difference from the mean value of total thermal resistance for a given external wall and 79% of the results were within 20% difference. All of the used measuring methods (TBM, HFM and ITM) have proven to be similarly approximate in obtained total thermal resistances, on average between 6% and 11% difference from the mean values. It has also been noted that, while performing measurements, close attention should be paid to certain aspects, because they can have a major influence on the quality of the result.

Oversized Electrical Appliance Impacts on Condominium Energy Efficiency and Cost-Effectiveness Management: Experts’ Perspectives

A direct use approach incorporating a cost approach assumed that replacing oversized electrical appliances with those better fit to actual energy consumption can reduce energy consumption, optimizing capacities of the new appliances to the maximum while reducing electricity costs. This study aimed to verify the assumption that the size of appliances has impacts on energy consumption and cost effectiveness. A mixed-method approach included these instruments for data elicitations (i.e., a questionnaire, data records of 485 transformers, two assessments of condominium technical caretakers, and two in-depth interviews of electrical engineering experts). The findings revealed that most condominiums installed electric appliances that are too large for their actual energy usage, which lies between 5.4% and 7.1% of the capacity. This study therefore proposed a total cost reduction of 54% by downsizing these appliances (i.e., MV Switchgear 2 sets, dry type transformer 2 sets 80,000, LV Cable 10 m. (XLPE), main distribution board, Busduct (MDB-DB), generator (20% of Tr.), and generator installation). Even though this analysis is limited to Bangkok, Thailand, this case may contribute decision-making on electrical appliance selection at early stage of investment or to downsize the currently installed appliances for the more energy efficient and cost-effective management of condominiums around the world.

Domestic hot water optimizing potential in existing or renovated multifamily residential buildings

In a Swiss case study of the ReCO2st research project, hot water optimization demonstrated a high potential for energy savings with low investment costs. The optimization started with the end user to reduce first hot water consumption. Energy-efficient showerheads and faucets reduced hot water consumption by 10 to 25%, notably from 65.2 [l/p.day] to 48 [l/p.day] for the period of September to October 2019. A multi-criteria selection of showerheads involved end users considering other qualitative aspects like rinsing efficiency, overall feel of use, noise, and material robustness. Strict control of pipe and storing tank insulation reduced storage and distribution losses. Day and night storage temperature setpoints, water recirculation time, switching off this process after 11:00 p.m., temperature differential of start and stop loading setpoints, creating long loading cycles, ensure that the pipes are not always hot. Reducing Legionella cycles at 60° to once a day avoided the need for continuous high temperatures. The combination of all these soft measures in the Swiss case study resulted in a reduction of energy consumption for hot water of 20-30%. This is equivalent to the installation of expensive solar panels for hot water. A detailed two-year monitoring of the building's hot water consumption shows the contribution of each optimization measure. The encouraging results show that without perfect control of the entire process, it is impossible to avoid a performance gap between planned and actual energy consumption.

Influencing Factors Evaluation of Machine Learning-Based Energy Consumption Prediction

Modern computing resources, including machine learning-based techniques, are used to maintain stability between the demand and supply of electricity. Machine learning is widely used for the prediction of energy consumption. The researchers present several artificial intelligence and machine learning-based methods to improve the prediction accuracy of energy consumption. However, the discrepancy between actual energy consumption and predicted energy consumption is still challenging. Various factors, including changes in weather, holidays, and weekends, affect prediction accuracy. This article analyses the overall prediction using error curve learning and a hybrid model. Actual energy consumption data of Jeju island, South Korea, has been used for experimental purposes. We have used a hybrid ML model consisting of Catboost, Xgboost, and Multi-layer perceptron for the prediction. Then we analyze the factors that affect the week-ahead (WA) and 48 h prediction results. Mean error on weekdays is recorded as 2.78%, for weekends 2.79%, and for special days it is recorded as 4.28%. We took into consideration significant predicting errors and looked into the reasons behind those errors. Furthermore, we analyzed whether factors, such as a sudden change in temperature and typhoons, had an effect on energy consumption. Finally, the authors have considered the other factors, such as public holidays and weekends, to analyze the significant errors in the prediction. This study can be helpful for policymakers to make policies according to the error-causing factors.

Development and Analysis of a Dynamic Energy Model of an Office Using a Building Management System (BMS) and Actual Measurement Data

Calibration of the energy model of a building is one of the essential tasks required to determine the efficiency of building management systems, and both their own and other systems’ improvement potential. In order to make the building energy model as accurate as possible, it is necessary to collect comprehensive data on its operation and sometimes to assess the missing information. This paper represents the process of developing an energy model for an administrative building and its calibration procedure, using detailed long-term measurement and building management system (BMS) data. Indoor air temperature, CO₂ concentration, and relative humidity were experimentally measured and evaluated separately. Such dual application of data reduces the inaccuracy of the assumptions made and assesses the model’s accuracy. The DesignBuilder software developed the building model. During the development of the model, it was observed that the actual energy consumption needs to be assessed, as the assumptions made during the design about the operation and management of HVAC systems often do not coincide with the actual situation. After integrating BMS information on HVAC management into the building model, the resulting discrepancy between the model results and the actual heat consumption was 6.5%. Such a model can be further used to optimize management decisions and assess energy savings potential.

Personal Heating in Dwellings as an Innovative, Energy-Sufficient Heating Practice: A Case Study Research

Despite the efforts to improve the energy efficiency of buildings, the actual energy consumption decreased much less than expected in recent years. Therefore, energy sufficiency is gaining attention as a complementary approach to energy efficiency. It aims to reduce the actual energy consumption of buildings by providing thermal comfort to residents in a sufficient way. This demands for alternative heating practices, such as the application of personal heating systems. Although a review of past studies shows that, in office buildings, thermal comfort can be provided with less energy by using personal heating systems, the application in a residential context is much less explored. Our hypothesis is that an innovative, energy-sufficient personal heating practice also has potential to reduce the overall energy consumption in dwellings. Therefore, this paper presents the results of a one-week case study on personal heating as an energy-sufficient heating practice in three dwellings. During the case study, the ambient temperature was reduced to 18 °C, and residents were allowed to use active and passive personal heating systems to make themselves as comfortable as possible. They were also asked to evaluate their thermal sensation and thermal comfort. The results show that, despite a lower indoor temperature, residents are able to achieve thermal comfort by using personal heating at the locations where they effectively reside. Additionally, a significant energy saving potential was found. The case study proved our hypothesis, leading to the conclusion that an innovative, sufficient personal heating practice in dwellings can be a supplementary step to reduce the energy consumption to meet the global challenges.

Building Energy Performance Certificate—A Relevant Indicator of Actual Energy Consumption and Savings?

A building energy performance gap can be illustrated as the difference between the theoretical (methodologically defined) and the actual energy consumption. In EU countries, Energy Performance Certificates are issued when buildings are constructed, sold, or leased. This information is the first step in order to evaluate the energy performance of the building stock. In Serbia, when issuing an energy certificate, the adopted national methodology recognizes only energy consumption for heating. The main purpose of this paper is to evaluate the energy gap and estimate the relevance of an Energy Performance Certificate to meet the national energy efficiency or carbon target. An Energy Performance Certificate determines the theoretical residential and commercial building energy efficiency or its “design intent”. This research stresses the necessity of measuring and achieving reductions in actual energy consumption through system regulation and consumers’ self-awareness in buildings. The research compares the performance of the building stock (135) that is connected to the District Heating System (DHS), with its own integrated heat meter, to Individual Gas Boiler (IGB) systems (18), in the city of Novi Sad, Serbia, built after 2014. For the purpose of comparing energy consumption, 16 buildings were selected that are very similar in terms of design, operation, and location. The data used are derived from metered consumption data, official evidence of city service companies, and Energy Performance Certificates of the considered buildings. We have determined that IGB systems have a much wider specific annual performance gap (11.19–101 kWh/m2a) than the buildings in the DHS (3.16–18.58 kWh/m2a).

Understanding the energy performance GAP: case studies of energy efficient homes

The energy performance gap between the predicted and actual energy consumption of 3 LEED for Homes certified buildings were investigated. The actual energy consumptions of the homes were found to be 23 to 77% higher than the initial energy consumption predictions made during the design stage. Revisions to the HOT2000 models to account for changes made between the design and occupancy phase of the buildings helped reduce the gap (9 to 40%). The sources of the discrepancies were found to be related to the energy modeling program’s limitations, inconsistency between the energy model and the actual building, and additional loads in the homes. The HOT2000 program, which is used for obtaining the EnerGuide rating for LEED certified homes, was compared against a dynamic energy simulation program to assess the applicability of the use of the former for energy efficient homes. The use of EnergyPlus not only allowed for a more accurate representation of the actual homes in the energy models, but an increase in the EnerGuide rating for the home was seen, which in turn equates to additional points for the home under the “Energy & Atmosphere” category for the LEED for Homes certification process

Understanding the energy performance GAP: case studies of energy efficient homes

The energy performance gap between the predicted and actual energy consumption of 3 LEED for Homes certified buildings were investigated. The actual energy consumptions of the homes were found to be 23 to 77% higher than the initial energy consumption predictions made during the design stage. Revisions to the HOT2000 models to account for changes made between the design and occupancy phase of the buildings helped reduce the gap (9 to 40%). The sources of the discrepancies were found to be related to the energy modeling program’s limitations, inconsistency between the energy model and the actual building, and additional loads in the homes. The HOT2000 program, which is used for obtaining the EnerGuide rating for LEED certified homes, was compared against a dynamic energy simulation program to assess the applicability of the use of the former for energy efficient homes. The use of EnergyPlus not only allowed for a more accurate representation of the actual homes in the energy models, but an increase in the EnerGuide rating for the home was seen, which in turn equates to additional points for the home under the “Energy & Atmosphere” category for the LEED for Homes certification process