• Energy Research
• 11. Sustainability close
• DK close
• Energy and Buildings close

Abstract The increasing global energy demand, the foreseen reduction of available fossil fuels and the increasing evidence off global warming during the last decades have generated a high interest in renewable energy sources. However, renewable energy sources, such as wind and solar power, have an intrinsic variability that can seriously affect the stability of the energy system if they account for a high percentage of the total generation. The Energy Flexibility of buildings is commonly suggested as part of the solution to alleviate some of the upcoming challenges in the future demand-respond energy systems (electrical, district heating and gas grids). Buildings can supply flexibility services in different ways, e.g. utilization of thermal mass, adjustability of HVAC system use (e.g. heating/cooling/ventilation), charging of electric vehicles, and shifting of plug-loads. However, there is currently no overview or insight into how much Energy Flexibility different building may be able to offer to the future energy systems in the sense of avoiding excess energy production, increase the stability of the energy networks, minimize congestion problems, enhance the efficiency and cost effectiveness of the future energy networks. Therefore, there is a need for increasing knowledge on and demonstration of the Energy Flexibility buildings can provide to energy networks. At the same time, there is a need for identifying critical aspects and possible solutions to manage this Energy Flexibility, while maintaining the comfort of the occupants and minimizing the use of non-renewable energy. In this context, the IEA (International Energy Agency) EBC (Energy in Buildings and Communities program) Annex 67: “Energy Flexible Buildings” was started in 2015. The article presents the background and the work plan of IEA EBC Annex 67 as well as already obtained results. Annex 67 is a corporation between participants from 16 countries: Austria, Belgium, Canada, China, Denmark, Finland, France, Germany, Ireland, Italy, The Netherlands, Norway, Portugal, Spain, Switzerland and UK.

The dominance of operational energy and related greenhouse gas (GHG) emissions of most existing buildings is decreasing in new construction, when primary fossil energy of building operation decreas ...

Abstract Model-based control schemes such as model predictive control (MPC) can assist smart-energy systems in achieving higher efficiency and utilization of renewable energy sources. A practical barrier for deploying such control schemes for space heating of residential buildings is the costs related to obtaining the weather data measurements needed for identifying a model that describes the dynamic behaviour of the building. Therefore, this paper reports on a simulation-based study investigating whether there is a significant impact on the performance of MPC schemes when substituting these weather measurements with data from meteorological weather services. Since access to weather forecasts is necessary during the operation of the MPC scheme, this implementation approach draws on data already available to remove the need for weather measurements. The results indicated that this approach only led to a minor performance impact in that heating savings were reduced by 4% while comfort violations increased by less than 0.1 Kh per day on average. The results thereby suggest that the use of data from meteorological forecast services for model identification may constitute a cost-efficient alternative to on-site or near-by weather measurements.

Abstract Roof windows are widely used in northern European countries, contributing positively by giving daylight, passive solar heat and view to the outside. In order to improve their thermal property, triple glazing unit together with external shutter are more and more common on the market. Additionally, the junction part between window and roof is also important since it greatly influences the linear thermal transmittance (LTT) along edges of the window and the daylight level of the room. This research presents a parametric analysis for roof windows with triple glazing unit and external shutter from perspectives of energy, daylight and thermal comfort. The investigation can be described in two parts: • Analysis of thermal and comfort performance for triple glazing unit with an external shutter. • Analysis of combined performance of daylight level and LTT for roof windows. Performances of energy and thermal comfort of triple glazing unit with external shutter can be influenced by different properties, including the width of the cavity between shutter and external pane, air penetration rate through the cavity between shutter and external pane, the tilt angle of the window. The study conducts analysis on the energy and comfort performances of the window by calculating U-value of the entire window and internal surface temperature of the glazing. The calculations are performed by a model developed via state-space modelling using Simulink/MATLAB. The results reveal that the external shutter improves both the thermal and comfort performances of the window. The ways of installing windows on a roof and cutting on the internal wall along window edges also have great influences on the combined performance of daylight level and LTT along the edge between window and roof. Therefore, daylight and LTT are also evaluated with different parameters, including the thickness of roof insulation, installation level of windows on the roof, cutting of lining and extra insulation around the perimeter of windows. The analysis is conducted using DIVA/Rhino and Flixo. The calculations show that the lower installation level and extra insulation around the window frame can decrease linear thermal transmittance of the entire window by more than 60%.

Abstract Pollution sources were quantified by the new olf unit in 20 randomly selected offices and assembly halls in Copenhagen. The spaces were visited three times by 54 judges, who assessed the acceptability of the air: (1) while unoccupied and unventilated to quantify pollution sources in the space; (2) while unoccupied and ventilated to quantify pollution sources in the ventilation system; and (3) while occupied and ventilated to determine pollution caused by occupants and smoking. Ventilation rates, carbon dioxide, carbon monoxide, particulates, and total volatile organic compounds were measured, but did not explain the large variations in perceived air quality. For each occupant in the 15 offices there were on average 6–7 olfs from other pollution sources; 1–2 olfs were situated in the materials in the space, 3 olfs in the ventilation system, and 2 olfs were caused by tobacco smoking. The ventilation rate was 25 l/s per occupant, but due to the extensive other pollution sources only 4 l/s per olf. This explains why an average of more than 30% of the subjects found the air quality in the offices unacceptable. The obvious way to improve indoor air quality is to remove pollution sources in the spaces and in the ventilation systems. This will at the same time improve air quality, decrease required ventilation and energy consumption, and diminish the risk of draughts.

Abstract Energy flexibility is a cost-effective solution to facilitate secure operation of the energy system while integrating large share of renewables. Thermal energy infrastructure is a great asset for flexibility in systems with widely developed district heating networks. The aim of the present work is to investigate the potential for low-energy residential buildings to be operated flexibly, according to the needs of district heating system. An apartment block is studied, utilizing the storage capacity of thermal mass as storage medium. Two sets of data are utilized: heat load of Greater Copenhagen and dynamic heat production cost which is used as a price signal for the scheduling of the heating use in the building. Scenarios with different control signals are determined in order to achieve load shifting. The findings show that pre-heating is highly effective for load shifting and peak load reduction. During morning peak load hours, energy use is reduced in all scenarios between 40% and 87%. Although with load shifting higher energy use may occur, it occurs mostly at times when the city heat load is lower and heat production is less expensive and less carbon-intensive. Indoor temperature has a wider range and/or more fluctuations, yet remains within acceptable limits.