• Energy Research

The reduction of air-conditioning energy consumptions is one of the main indicators to act on when improving the energy efficiency in buildings.

Renovation Wave aims to boost the uptake of deep renovation towards the CO2 emission targets for 2030. In this perspective, there is the need of technologies and solution sets for improving the deep renovation process as well as demonstrating the performances for supporting the stakeholders in the decision-making process. To cope with the issue, this work presents a methodology for setting up a repository of building deep renovation packages that integrates industrialised facade technologies and more traditional solutions. The performances feeding into the repository have been evaluated by means of transient detailed simulations on a set of reference buildings in representative European climate conditions. The renovation packages are evaluated in terms of key performance indicators dealing with five areas: energy, comfort, pollutant emissions, cost, and renovation time. The defined repository includes 289 assessed technology packages and associated performances across Europe, providing a comprehensive support to identify the most effective solutions according to the user needs. The paper presents the application of the repository with two examples of stakeholders’ decision-making paths for selecting the deep renovation packages according to different priorities and expected targets.

Abstract In the perspective of the Net Zero Energy Buildings as specified in the EPBD 2010/31/EU, we propose the concept and design of a modular unglazed solar thermal (UST) facade component for facilitating the installation of active solar facades. The renovation of existing buildings offers an opportunity to improve the energy efficiency when using such a system and a novel design methodology tackled via a parametric approach is here proposed. We analysed a variety of building typologies as potential application targets of the UST collector, properly sizing the collector field for each typology to match the heat loads profile. We investigated the thermal behaviour of the novel thermal facade component and the energy potentiality in covering the heat demand using the TRNSYS software’s model of the UST collector field as a part of a combisystem. We concluded with the definition of rules of thumb for early design stage. The work here presented demonstrates that the low-cost, the versatile modularity and the easy installation make this active solar facade an innovative and promising technology for the building stock transformation, despite of the low quality of the produced energy due to the low outcome temperature of the unglazed collector.

Abstract Energy Performance Certificates (EPCs) are expected to be a useful instrument for stakeholders (including final users), enabling to compare building energy performances within a purchasing/renting decision process. Thereby, EPCs should have a direct impact on the value of the properties, affecting the market attractiveness, as well as driving the investors in the energy renovations process. Nevertheless, a survey to real estate agents reveals a perceived low reliability of EPCs, representing one of the main barriers in their full implementation. The paper presents the EPCs impact in the building market and an analysis on energy efficient buildings in eight European countries.

The paper analyses the benefits of the application of energy analysis in the early-stage building design, in particular for large commercial buildings. The research highlights the barriers that prevent this early integration and finally proposes the development of a methodology tailored around the optimization of energy efficiency during early-stage design. In general, the research aims to identify (a) the accuracy obtainable through progressive simplifications of the building model, (b) the most significant building parameters with respect to the model result accuracy and (c) the maximum number of simplifications able to ensure the respect of time requirements dictated by early-stage building design and to maintain an acceptable level of correctness. Here, as detailed example of simplification process, a case study of a large multi-storey office building is modelled starting with a previous detailed simulation performed through EnergyPlus and Openstudio software. The detailed model is then analyzed and progressively simplified. At each progressive simplification step, a comparison with the detailed results is given in terms of building energy needs and power curves of the system. The analysis is performed based on three different system hypotheses: a single-zone system and a variable air volume system with and without humidity control. The quantitative differences between detailed and simplified model are analyzed to determine the quality of the results of the simplified model.

Abstract A typical problem of Building Integrated Photovoltaic (BiPV) is the power loss due to temperature increase caused by limited cooling compared to free standing photovoltaic (PV) systems. Higher operating temperatures have a negative effect both on the efficiency and lifetime of the PV system. Decreasing the PV operating temperature in BiPV applications is thus a crucial aspect to both enhance the system efficiency and to decrease the temperature-induced degradation process. This study investigates the effectiveness of a passive low-cost strategy to improve the PV performance of BiPV systems by decreasing the module temperature. It consists in the application of an heat sink system on the PV module back side to enhance the PV cooling. An experimental investigation was performed on a wooden BiPV facade prototype and the results show that this strategy could lead to a temperature reduction up to 5.2 °C, meaning a possible power output increase of 2.3% of the PV nominal power. Considering a South facing facade application in Agrigento (South of Italy) climate, this strategy could enhance the annual PV energy generation for an extent of 1.2% and the total PV energy generation over the whole module life-time for an extent of 31% due to a longer life-time (considering some assumptions reported in the paper).

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.

Abstract Policy makers need scientific support to set ambitious yet realistic environmental targets for the transition to energy efficient buildings and to develop cost-effective policies to meet these targets, but comprehensive, manageable procedures to this aim are still lacking. Our proposed method ranges from baseline creation to transition scenarios depending on annual retrofit budget and specifies the buildings to renovate according to location, size, and age, and the energy efficiency measures to apply based on cost and energy saving. We show how to extrapolate a baseline from few available data, determine retrofit costs, and create calibrated models to estimate energy savings. Retrofits are ranked by levelized cost of saved energy, which ensures that for any budget allocated to retrofit maximum energy savings are obtained at minimum cost to society. The results are summarized in an energy efficiency cost curve enabling policy makers to estimate potential costs and energy savings. We demonstrate the method on a housing stock in northern Italy and show that facade insulation of old buildings in colder climates can compete with gas heating. About 60% baseline energy consumption can be saved doubling current investments, while a maximum saving of 75% requires over three times the current investments.