•Ambient wet bulb temperature limits cooling potential of a building component skin.•Daytime sol–air temperature limits heating potential of a building component skin.•Cooling and heating efficiency ...of the skin of a building component have been defined.•The efficiency of different skin systems are comparable in a unique value.
The thermal evaluation of building components composed of a base wall with a solar passive skin solution, such as a vertical/roof greenery system, ventilated façade, reflective painting, etc., is usually performed as a whole. In this research, it has been proven that, independently of the base wall thermal inertia and insulation level, the temperature of the outermost surface layer of any building component during sunny hours is mainly dependent on the ambient air temperature and relative humidity, the incident global solar radiation and the building skin behaviour.
The latter assumption has been proven on the south wall of a reference building simulated with TRNSYS. The south wall properties have been varied and the building has been subjected to different climates. The assumption’s validity has been checked for twelve south wall cases: a combination of 2 thermal transmittance, 2 thermal inertia and 3 climates. Each case has been simulated for a whole year. Based on this finding and the local ambient conditions for sunny hours, the hypothetical achievable maximum and minimum temperatures for the outermost surface layer have been defined. Then, based on the outermost surface temperature experimental measurements, the cooling and heating solar efficiencies valid for any skin solution have been defined.
Furthermore, the developed methodology has been applied to a vertical living wall tested for a whole year under the accuracy and quality procedure of the PASLINK method. In this way, the cooling and heating solar efficiencies were experimentally determined for this skin solution for both, the hot cold seasons. The study has shown that the cooling efficiency during the hot season is 90.8%. As expected, even during sunny summer hours, the presence of water positively affects the performance of the façade, as it brings the base wall external surface temperature close to the ambient wet bulb temperature, therefore reducing the cooling load of the building. For the cold season, the cooling efficiency was similar, at 90.3%, which means a heating efficiency of 9.7%. Again, even for sunny winter hours, the values of the external surface temperature tend towards the ambient air wet bulb temperature, resulting in an increase in the heating demand.
These experimental efficiency values allow the heating or cooling behaviour of different skin solutions to be comparable with a single number that is independent of the base wall composition. In addition, independently of the base wall composition, once the experimental efficiency value of a given skin solution is known, it allows (during sunny hours) the base wall outermost surface temperature to be calculated with precision. The latter makes it possible to increase the accuracy of the estimation of the heating and cooling demands of such methods as the degree-day method.
The European Union is changing its energy model towards a more efficient and sustainable one. In this new outlook, the Heat Pump (HP) has become a leading technology in the building energy sector. ...The use of the air source heat pump (ASHP) in the energy installations in the so-called nZEB low consumption buildings is currently on the increase. Furthermore, its performance improves when supported by solar energy, which can be achieved through the use of hybrid solar thermal photovoltaic elements (BIPV/T) integrated into the building’s façade, thus reducing consumption by 9 or 10%. However, the improvement can be even higher if a thermal storage system is incorporated.
This research demonstrates the potential of one particular photovoltaic forced ventilated façade (PV-FVF) used as support for a heating and DHW system based on ASHPs, taking advantage of the entire building as a thermal accumulation system. For this, an “Adaptive Indoor Temperature Setpoint Strategy”, called Tadaptive, is proposed as one alternative mode of operation for the PV-FVF plus ASHP hybridisation. The objective is to transfer thermal energy to the building when the façade is obtaining a higher solar thermal gain. The PV-FVF was characterised experimentally in exterior conditions in a PASLINK test. It was modelled numerically and analysed on a whole building level using a thermal simulation programme into which the predictions of the numerical model were incorporated.
Using as an example a residential building with underfloor heating in the city of Madrid, Spain, it was found that the use of the Tadaptive as the accumulation strategy could double the savings obtained with an ASHP supported by a PV-FVF, reducing heating consumption by 19.9%; while including the photovoltaic generation of the outer leaf reduces the total annual final energy for heat demand by 20.7%. The viability of this proposal is therefore demonstrated on the basis of existing technology as an alternative to reduce even further the energy consumption of nZEB type buildings for which the contribution of this hybridisation can be significant.
The thermal characterization of building components in dynamic exterior conditions is crucial for understanding their real performance, particularly if they are passive or active solar elements. In ...this respect, the PASLINK methodology has stood out as an effective technique for outdoor testing due to its level of development and precision. It is based on the use of a calibrated test cell with interior walls covered by heat flow meters. The accurate determination of the heat flow through the envelope of the cell is essential for the subsequent thermal analysis of the passive/active solar component being tested.
Although the walls of a PASLINK cell have a high thermal resistance and minimal thermal bridges, a higher heat flux is inevitable near the inner corners because of the edge effects. This variation is partially detected by heat flow meters, requiring correction factors accordingly named ‘edge effect factors’. Additional heat flow meters strategically arranged in some interior corners are used to determine these factors in a calibration test. The factors thus calculated are used as invariable values in subsequent cell tests. However, the skill and knowledge of the staff conducting the calibration test are fundamental, as human errors can affect this process.
This proposal outlines a more objective and reliable new methodology to determine edge effect correction factors. It is based on applying correlations of instantaneous readings of heat flow meters. These correlations are obtained in an initial PASLINK calibration test, but are valid for all subsequent tests. The factors calculated in this way depend on instantaneous test readings and, for this reason, they are dynamic values perfectly adapted to each test.
The calibration test of the cell called EGUZKI, located in Vitoria-Gasteiz (Northern Spain), is used to demonstrate the validity of the proposed method. With the current PASLINK calibration test methodology, the calibrated cell obtains a measurement error of 13%, while the proposed new dynamic methodology reduces this error to 6%.
Although this new methodology is determined in the context of a PASLINK test cell, it is an extensive method applicable to the correction of heat flow measurements affected by edge effects in general.
Nowadays, most areas of human activity should be reviewed with the aim of reducing CO2 emissions, since these activities are producing the majority of these emissions. Specifically, the building ...sector is one of the main responsible activities. In order to minimize the ecological footprint and ensure energy sufficiency, European Union created the nearly-Zero Energy Building (nZEB) concept. More than ten years have elapsed and it worth to review the current state around the concept, considering the new advances in computer development that are already applicable to this field. Accordingly, recent researches published in reputed indexed journals and international conferences have been reviewed. This paper explains the nZEB concept and reviews research articles focused on achieving it. A research gap is detected, so enabling concepts and technologies as Building Energy Performance Simulation (BEPS) tools and Model Predictive Control (MPC) are recalled, and relevant researches where used are included in a specific state-of-the-art for each concept, since the academia considers that these tools should be applied in building air conditioning to achieve nZEB. After this deep analysis, we conclude that the possibilities to optimize the energy consumption are huge combining properly in a holistic way BEPS tools for modeling and simulation and MPC for control strategies. It is possible to manage a Heating, Ventilation and Air Conditioning (HVAC) system using Renewable Energy Sources (RES) in an effective means, reducing CO2 emissions problems worldwide and reaching considerable energy savings.
•The nZEB concept has been explained and different factors that are important to reaching this objective have been reviewed.•A A research gap has been detected about nZEB due they are not transversal only their focus is from a specific point of view.•It has been raised a holistic treatment, with a multidisciplinary approach to achieve the energy efficiency of the buildings.•BEPS tools literature have also been reviewed since the possibilities to optimize the energy consumption using them are huge.•The MPC concept has been explained and it is considered as a great control option to find optimal management of the energy.
In this article, the results of the hygroscopic characterization of a building material called ‘picón’, consisting of cement mortar and pyroclastic deposits from volcanic eruptions, are presented. ...The material obtained is used for the manufacture of blocks used in the construction of buildings in the Canary Islands. Picón is a heterogeneous material with uncontrolled particle size, having a pore system of very scattered sizes, what affects the moisture behaviour of the blocks. This heterogeneity results in a pore structure that affects the determination of the moisture properties of the material. In this work, this difficulty is faced, separately studying the pore structure of the cement paste and the aggregates, to come to a better interpretation of the concrete behaviour. The results indicate that the pore structure of the heterogeneous concrete differs from what could be expected from separately obtained porosimetry of each component of the concrete.
Energy performance and thermal comfort in historic and traditional urban environments are important because of the social and cultural requirement to conserve these areas as living entities, but also ...for the environmental obligation to decrease the impact of existing buildings globally. The objective of ENERPAT approach is to address this global challenge from the local perspective, through the co-creation of efficient solutions that improve the energy performance of historic areas considering local techniques and skills, taking into account the whole life cycle of the solutions, and supporting local economy and business. The objective is to test the efficiency and suitability of eco-renovation strategies that have been co-created with local stakeholders and are based on traditional energy conservation measures, as a way to work with locally-based business models that can safeguard cultural aspects and enable economic development. Two living labs have been established in the cities of Vitoria-Gasteiz (Spain) and Cahors (France) in two representative buildings of the historic urban area of each city. The living labs operate as inclusive multi-agent discussion arenas with a long-term vision, where multi-criteria co-creation processes are implemented to select conservation-friendly solutions based on local materials including criteria such as operational energy, impact on heritage values, quality of life, socio-economic development and easy logistics. The energy behaviour of the buildings and the hygrothermal performance of the external walls have been studied using on-site and laboratory experiments, through an efficient partnership between local authorities and universities. Likewise, local-based refurbishment solutions that were designed in the co-creation processes have been thermally characterised in the laboratory, through thermal conductivity and guarded hot box tests. Finally, the energy improvement of the whole renovation strategy has been simulated showing the enhancement of the two buildings.
•Energy efficiency of historic centres through eco-renovation and vernacular culture.•Energy transition based on co-creation and evolutionary development.•Urban labs to merge evidence-based knowledge with socio-economic considerations.•Architectural heritage is broadened to include traditional techniques.•Results of the co-creation process are tested with experimental and numerical work.
•Cost-optimal approach is applied to the residential building stock of Bilbao, northern Spain.•Energy renovation packages are explored under different scenarios.•Achieved cost-optimal levels ...represent the half of the current thermal consumption.•Adding renewable energies, all the existing buildings could be transformed into nZEB.•Public support is generally needed to make energy retrofitting attractive for the user.
The low replacement rate of existing residential buildings, together with their high share in the final energy consumption, has put energy refurbishment of the current stock in the centre of the agenda. Nevertheless, due to the high up-front investment and long payback period that it usually implies, deep energy retrofitting is not yet widely applied. In this context, the cost-optimal methodology introduced by Directive 2010/31/EU created a framework to identify the energy efficiency measures that would maximize the economic return. However, the analysis of cost-optimality has often been limited to a single building or type of building, which cannot be extrapolated to an existing building stock. In other cases, the limited number of reference buildings hinders the capture of the great heterogeneity of an existing building stock into sufficiently homogeneous building typologies for a reliable extrapolation of the assessment results. To address such a challenge, this research proposes the application of the cost-optimal method on an urban scale, aiming to identify the suitable range of energy performance that is reasonable to promote in different types of buildings, keeping in mind their specific characteristics. The methodology is applied to the residential building stock of the city of Bilbao, northern Spain, through a comprehensive approach that also incorporates deeper interventions pointing at nearly zero-energy building levels. The results aim to support decision-makers in outlining the most suitable energy efficiency policy and determining the priority targets that demand the mobilisation of investment.
•A DCE is conducted to assess households’ willingness to insulate their homes.•Determinants for the adoption of façade thermal insulation are identified.•The investment cost required in the existing ...building stock is below the obtained WTP.•The required subsidy level is lower than the grants set by existing aid programs.•Increased tax rebate has greater incentive effect than soft financing.
This paper assesses Spanish households’ willingness to thermally insulate their homes and the drivers that influence such a decision-making process. Stated preference data were collected through a discrete choice experiment (DCE). The final sample of 191 respondents and 1,145 observations was analysed by the use of a mixed logit model, weighing the factors that encourage homeowners to carry out façade energy renovations or not. The model enables the quantitative estimation of renovation adoption rates depending on the households’ characteristics and public support instruments in place. The results show that homeowners are extremely interested in increasing the thermal insulation of their homes. The actual investment cost required in the existing building stock is lower than the obtained willingness-to-pay. Furthermore, it was found a relevant effect of a variety of household features on renovation choice (income, age, heating system, etc.), which should be contemplated in the energy efficiency policy design. Additionally, a case analysis is performed which comprises 3 household categories. The results reveal that the required subsidy level is different in each case, sometimes even unnecessary, although all of them lower than the grants set by existing aid programs. Thus, to reduce the free-riding effect, a closer perspective would enable targeted support mechanisms towards each household category. Moreover, the policy performance can be improved by combining subsidies with other measures such as low-interest loans or increased tax rebates, which could contribute to improving the cost effectiveness of the public expense associated with direct grants. Overall, an increased tax rebate is preferred to soft financing, although the influence of the latter increases in low-income households.
A data-driven model is used to predict one-hour ahead heat loads based on present and recent history of weather and heat loads. A computationally inexpensive method is built to deliver load ...forecasting based on existing data quality and resolution from smart meters. Optimal model formulation is discussed and optimized at 4-hour historical values. The model is trained and tested against synthetic data from a building energy simulation, resulting in absolute error <4% and R2 values in the range of 0.92 to 0.94.
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