In the present study, a zero-dimensional thermal model has been developed to analyze a novel low concentration photovoltaic-thermal (CPVT) collector. The model has been developed by driving heat transfer and energy balance equations for each part of the collector and then solving all the equations simultaneously. Moreover, a Monte-Carlo ray-tracing software has been used for optical stimulations of the parabolic trough solar collector. The novel CPVT collector has been experimentally tested at Gävle University (Sweden) and the model has been validated against the experimental results. The primary energy saving equivalent to the thermal-electrical power cogeneration of the CPVT collector has been determined. The effect of glass cover removal, heat transfer fluid (HTF) inlet temperature and mass flow rate on the collector performance has been investigated. The optimum HTF mass flow rates of the collector for maximum electrical yield and overall primary energy saving were determined under specified operating conditions by considering the pump consumption. The effect of mean fluid temperature on the thermal and electrical efficiencies has been studied and the characteristic equation of the thermal efficiency has been obtained. The thermal and electrical peak efficiencies of the collector have been found to be 69.6% and 6.1%, respectively.

Historical buildings account for a significant portion of the energy use of today’s building stock, and there are usually limited energy saving measures that can be applied due to antiquarian and esthetic restrictions. The purpose of this case study is to evaluate the use of the building structure of a historical stone building as a heating battery, i.e., to periodically store thermal energy in the building’s structures without physically changing them. The stored heat is later utilized at times of, e.g., high heat demand, to reduce peaking as well as overall heat supply. With the help of Artificial Intelligence and Convolutional Neural Network Deep Learning Modelling, heat supply to the building is controlled by weather forecasting and a binary calendarization of occupancy for the optimization of energy use and power demand under sustained comfortable indoor temperatures. The study performed indicates substantial savings in total (by approximately 30%) and in peaking energy (by approximately 20% based on daily peak powers) in the studied building and suggests that the method can be applied to other, similar cases.

This IEA Annex 80 Subtask C report and the associated brochures provide examples of well-documented field studies. These field studies apply resilient cooling technologies to reduce energy demand and carbon emissions for cooling and reduce the overheating risk in different types of buildings, including newly constructed and existing buildings. Examples and details on building information, energy systems, resilient cooling technologies, key performance indicators (KPIs), and performance evaluation amd lessons learned are included in the report and the brochures.

The present report summarizes all 13 field study buildings collected in Subtask C of IEA-EBC Annex 80. This summary presents information on the field studies, the resilient cooling technologies applied in the field studies, the KPIs, and the performance evaluation and lessons learned. The values of KPIs for building similar functions, i.e., residential buildings, under different climate conditions were discussed. In the field study brochures, detailed information is inlcuded for each building.

The field studies are presented in brochure format. Each brochure contains information in a standardized format. This includes the introduction & climate, building information, resilient cooling, KPI evaluation, design simulation, performance evaluation, discussion, lessons learned, references & key contacts.

This paper presents an experimental investigation of a photovoltaic-thermal solar collector (commonly known as PVT) that generates both electricity and heat from the same gross area. PVT solar collectors, in theory, achieve higher combined electrical and heat yields. Additionally, PVT enables a thermal coupling between PV cells and a heat transfer cooling medium. Electrical and thermal outdoor testing measurements have been performed on alow concentration PVT solar collector based on a parabolic reflector geometry with a wedge PVT receiver. Several outdoor experiments have been carried out and presented, such as daily instantaneous electrical and thermal performance efficiency diagrams, as well as optical efficiency charts. Moreover, an electrical IncidenceAngle Modifier (for both transversal and longitudinal directions) assessment has been performed and presented. Furthermore, an overall heat loss coefficient of 4.1 W/m2.◦C has been attained. A measured thermal optical and electrical efficiency of 59% and 8% have been achieved, respectively. Additionally, the placement of the wedge receiver shown to be very sensitive to high incidence angles, as the electrical transversal Incidence AngleModifier factor decreases significantly after reaching its electrical peak efficiency at 10◦.

A two-trough parabolic-shaped concentrating photovoltaic solar collector with a vertical half-size ‘phosphorus-passivated emitter rear totally diffused’ bifacial cell string receiver was designed and built for household applications, with the aim of smooth the electrical ‘duck curve’. The study consisted in testing the concentrating photovoltaic solar collector outdoors, under real weather conditions, for its daily electrical peak power and efficiency, as well as for its electrical transversal and longitudinal Incidence Angle Modifier direction. The outdoor testing measurements were conducted in a parabolic trough with low concentration coupled with a central vertical half-size ‘phosphorus-passivated emitter rear totally diffused’ bifacial cell string receiver. Furthermore, the electrical transversal Incidence Angle Modifier showed to be very delicate due to the position and outline of the receiver, which led to an electrical peak efficiency close to 10% at ±25° (i.e., for an electrical power output of around 49.3 W/m2). To validate the measured parameters, a ray-tracing software has been used, where the measured Incidence Angle Modifiers have a very good agreement with the simulated Incidence Angle Modifiers (e.g., deviation of <4%). Consequently, the concentrating solar collector met the objective of lowering the Photovoltaic cell stress and high radiation intensity, by shifting the electrical peak power at normal (e.g., at 0°) to higher incidence angles (e.g., ±25°); this aids the electrical demand peak shaving, by having the highest electrical power production displaced from the highest intensity solar radiation during the day.

The world is facing a rapid increase of air conditioning of buildings. It is the motivation of Annex 80 to develop, assess and communicate solutions of resilient cooling and overheating protection. Resilient Cooling is used to denote low energy and low carbon cooling solutions that strengthen the ability of individuals and our community to withstand, and prevent, thermal and other impacts of changes in global and local climates. It encompasses the assessment and Research & Development of both active and passive cooling technologies of the following four groups:

Reduce heat loads to people and indoor environments.Remove sensible heat from indoor environments.Enhance personal comfort apart from space cooling.Remove latent heat from indoor environments.The present review sums up the state of the art in cooling solutions which may be regarded as resilient. Its main objective is to systematically describe the available cooling solutions, their physical basis, their benefits and limitations, their technology readiness level, their practical availability, and applicability. Doing so, the State-of-the-Art Review forms the basis for the work of Annex 80.

When the sun rises, so does the key element that will shape the future of the world energy landscape. It is not an understatement to say that the solar energy industry is beginning to lead the path towards a sustainable future for all of us. However, the awareness of the potential of this amazing source of energy must begin from the most basic levels of education all the way to university. The scope of this paper is to display a new compact and didactic solar energy kit with the potential to replace current high cost and complex solar energy kits. These solutions are often too expensive and therefore unavailable for most of Europe’s public schools. As such, an equipment was developed using an open-source platform called Arduino that will enable students to conduct practical experiments in a fast, effective and simple manner and thus allow students to acquire the proper expertise in areas like energy, electronics, and programming.

The PVT technology combines solar PV and solar thermal in the same PVT panel. In this way, both electricity and heat are produced by the PVT panel. Compared to the PV technology and the solar heating technology the PVT technology is in the early market stage with only few small and weak industries active. Best practices for the PVT technology, which is still under rapid development, are summarized. Marketed systems with different PVT panel types, different PVT system types with different components for different applications are considered. The potential advantages for PVT systems and the needs for key actors in order to establish a successful sustainable future PVT market are given. Finally, recommendations for a subsidy scheme for PVT systems are given, so that a PVT market can be developed in parallel with the successful PV market.

In churches, intentional airing may be a measure to evacuate temporarily high levels of contaminants, emitted during services. Crucial contaminants include moisture and other emissions that may deteriorate and/or soil painted surfaces and other precious artefacts. Most old churches do not have any mechanical ventilation system or any purpose provided openings for natural ventilation, but the ventilation is governed by air infiltration. Enhanced airing may be achieved by opening external windows or doors. Thus, models provided in energy simulation programs should predict this kind of airflows correctly, to get a proper estimation of the total energy use. IDA Indoor Climate and Energy (IDA-ICE) simulation program is examined here and its model for airflow through large vertical openings is investigated. Moreover, field measurements were performed for airing rate in a historical church including. The simulated single-sided flows were of the same magnitude of the measured ones, but the effect of wind direction was less considered by the simulation program. At cross flow, when wind is approaching the opening it has a choice; flow through the opening or around and above the building. This process is not considered in the IDA-ICE model, which can contribute to the discrepancy between measurements and predictions.

Natural ventilation is the dominating ventilation process in ancient buildings like churches, and also in most domestic buildings in Sweden and in the rest of the world. These buildings are naturally ventilated via air infiltration and airing. Air infiltration is the airflow through adventitious leakages in the building envelope, while airing is the intentional air exchange through large openings like windows and doors. Airing can in turn be performed either as single-sided (one opening) or as cross flow ventilation (two or more openings located on different walls). The total air exchange affects heating energy and indoor air quality. In churches, deposition of airborne particles causes gradual soiling of indoor surfaces, including paintings and other pieces of art. Significant amounts of particles are emitted from visitors and from candles, incense, etc. Temporary airing is likely to reduce this problem, and it can also be used to adjust the indoor temperature. The present study investigates mechanisms and prediction models regarding air infiltration and open-door airing by means of field measurements, experiments in wind tunnel and computer modelling.

In natural ventilation, both air infiltration and airing share the same driving forces, i.e. wind and buoyancy (indoor-outdoor temperature differences). Both forces turn out to be difficult to predict, especially wind induced flows and the combination of buoyancy and wind. In the first part of the present study, two of the most established models for predicting air infiltration rate in buildings were evaluated against measurements in three historical stone churches in Sweden. A correction factor of 0.8 is introduced to adjust one of the studied models (which yielded better predictions) for fitting the large single zones like churches. Based on field investigation and IR-thermography inspections, a detailed numerical model was developed for prediction of air infiltration, where input data included assessed level of the neutral pressure level (NPL). The model functionality was validated against measurements in one of the case studies, indicating reasonable prediction capability. It is suggested that this model is further developed by including a more systematic calibration system for more building types and with different weather conditions.

Regarding airing, both single-sided and cross flow rates through the porches of various church buildings were measured with tracer gas method, as well as through direct measurements of the air velocity in a porch opening. Measurement results were compared with predictions attained from four previously developed models for single‑sided ventilation. Models that include terms for wind turbulence were found to yield somewhat better predictions. According to the performed measurements, the magnitude of one hour single-sided open-door airing in a church typically yields around 50% air exchange, indicating that this is a workable ventilation method, also for such large building volumes. A practical kind of diagram to facilitate estimation of suitable airing period is presented.

The ability of the IDA Indoor Climate and Energy (IDA-ICE) computer program to predict airing rates was examined by comparing with field measurements in a church. The programs’ predictions of single-sided airflows through an open door of the church were of the same magnitude as the measured ones; however, the effect of wind direction was not well captured by the program, indicating a development potential.

Finally, wind driven air flows through porch type openings of a church model were studied in a wind tunnel, where the airing rates were measured by tracer gas. At single-sided airing, a higher flow rate was observed at higher wind turbulence and when the opening was on the windward side of the building, in agreement with field measurements. Further, the airing rate was on the order of 15 times higher at cross flow than at single-sided airing. Realization of cross flow thus seems highly recommendable for enhanced airing. Calibration constants for a simple equation for wind driven flow through porches are presented. The measurements also indicate that advection through turbulence is a more important airing mechanism than pumping.

The present work adds knowledge particularly to the issues of air infiltration and airing through doors, in large single zones. The results can be applicable also to other kinds of large single-zone buildings, like industry halls, atriums and sports halls.

The Swedish environmental assessment certification system Miljöbyggnad rewards lower energy use in comparison to that of building regulations, related to total heated floor area. Previous studies suggest that this indicator shows the efficiency of the technical design of the building; not how well the building is utilized. Thus, a more suitable quantity/unit can be the one that takes into account the extent of how the building is used in a more efficient and sustainable way. The aim of this paper is to discuss if current energy units are sustainable enough to assess efficient use of buildings and investigate how indicators can affect the grades and criteria of a certification system. Normalization of simulated energy use of a school building, by using the total heated floor area, the total building’s enclosing area, number of occupants and the schedule of occupancy, give different results. 

The building sector accounts for a third of the total energy use in Sweden, and district heating provides half of the heating needs. The peak demand loads within a district heating network occur both regularly and irregularly and impose a burden on the energy company to fulfill the demand, often by using more expensive and less environmentally friendly resources (e.g., fossil fuels) instead of the waste heat from industry or biofuels. Heat storage during hours of less demand and prior to colder periods can be used for load management and sustainable planning of energy supply, as well as reduction of total greenhouse gas emissions. Thus, heat supply to the building can be lowered temporarily during the peak power period to utilize the stored thermal energy within the building thermal inertia. The use of indoor temperature decay and the delivery of heating power to a multifamily building are studied here, and heating storage capacity and thermal inertia are calculated. During the performed decay test, the energy supply was estimated to be reduced by 61% for 5 h, which resulted in only a 0.3 °C temperature decay. Therefore, the suggested method can shave eventual peaks in supplied heat with minimal influence on the thermal comfort.

Pressurization (blower door) test is a well-established standardized method, performed in order to quantify the total leakage in a building envelope. However, blower door results are not adequate to use when air leakage through the building envelope during natural conditions (non-pressurized) is to be estimated. A common assumption made when estimating air leakage during natural conditions, is that air leakage paths are evenly distributed in the areas of the building envelope. This assumption gives quite poor calculation results since different leakage configurations are often situated unevenly in the envelope. In order to improve the correspondence between Blower door and air leakage model results, more information on the types and locations of the leakage paths are required as input to simulation models. 

This paper investigates if additional information from visual inspection and IR-thermography observations at site can increase the precision when simulating air change rates due to air leakage in natural conditions.  A numerical model is developed in this study by allocating leakage in various parts of the building envelope. The leakage allocation is based on visual inspection and IR-thermography observations at the site during the blower door test.

This procedure is tested in the case study of a large single zone church. Blower door, neutral pressure level measurement and leakage allocation results are used as input in the numerical model. Model results are compared with tracer gas measurements and result accuracy is compared with results from the Lawrence Berkeley Laboratory model (LBL) and the Alberta Air Infiltration Model (AIM-2) for the same church. 

Airing can be a solution to introduce extra ventilation in large single zone buildings, especially where there are large aggregations of people such as churches or atriums. In naturally ventilated domestic and ancient buildings, opening of a window or door can introduce extra fresh air and remove particles and other contaminants emitted from people and other sources such as lit candles in churches. However, the energy use might be an issue in cold climates, where airing might lead to waste of heated air, at the same time as indoor air temperatures can be uncomfortably low. In the present study, the energy loss and ventilation rate due to airing in a large single zone (church) building is investigated via IDA-ICE simulation on annual basis in cold weather conditions. The results can be used in order to prepare airing guidelines for large single zone buildings such as atriums, churches, industry halls and large sport halls. According to the results, one-hour of airing in the studied church building resulted in 40-50 % of exchanged room air and, if practiced once a week, an increase of around 1 % in heating energy.

In churches, intentional airing may be a measure to evacuate temporarily high levels of contaminants that are emitted during services and other occasions. Crucial contaminants include moisture and other emissions that may deteriorate and/or soil painted surfaces and other precious artefacts. Most old churches do not have any mechanical ventilation system or any purpose provided openings for natural ventilation, but the ventilation is governed by air infiltration. Enhanced airing may be achieved by opening external windows or doors. Thus, models provided in energy simulation programs should predict this kind of air flows correctly, also in order to get a proper estimation of the total energy use. IDA-ICE is examined here and the model for air flow through a large vertical opening used in the program is investigated. In the present study, field measurements were performed for airing rate in a historical church. In comparison with measured air flow rates, the simulated results were of the same magnitude, but the effect of wind direction was less considered by the simulation program.

Temporarily enhanced natural ventilation of indoor environments can be achieved by opening windows and/or doors, i.e. airing. In this study, wind driven airing rate through doors was measured by tracer gas at a building model in a wind tunnel. Both single opening and cross flow airing was investigated, with doors placed in centrally on the long side of an elongated building model. It was found that cross flow airing yielded 4–20 times higher airing rate than single opening airing; lowest value occurring with opening surfaces perpendicular to wind direction. At single opening airing, windward positioned door yielded about 53% higher airing rate than leeward positioned. Inclusion of a draught lobby (extended entrance space) lowered airing rate by 27%, while higher wind turbulence increased it by 38%. Advection through turbulence appeared a more important airing mechanism than pumping. At cross flow, however, turbulence and draught lobby had practically no effect.

Air infiltration in ancient churches and other historical and monumental buildings is of great importance considering moisture transfer, energy consumption, thermal comfort and air pollutants that induce surface soiling. Two of the most established models for predicting air infiltration rate in buildings are the Lawrence Berkeley Laboratory (LBL) model and the Alberta air Infiltration Model (AIM-2). Being originally developed mainly for dwellings, their applicability to large single zone buildings is evaluated in this study by comparing model predictions with field measurements in three historical stone churches that are naturally ventilated only through infiltration. The somewhat more developed AIM-2 model yielded slightly better predictions than the LBL model. However, an LBL version that allows inclusion of the Neutral Pressure Level (NPL) of the building envelope produced even better predictions and also proved less sensitive to assumptions on air leakage distribution at the building envelopes. All models yielded however significant overpredictions of the air infiltration rate. Since NPL may be difficult to attain in practice, the AIM-2 model was chosen for model modification to improve predictions. Tuning of this model by varying its original coefficients yielded however unrealistic model behaviors and the eventually suggested modification implied introducing a correction factor of 0.8. This reduced the median absolute prediction error from 25% to 11%. Thus, especially when the NPL is not at hand, this modification of the AIM-2 model may suit better for air infiltration assessment of churches and other buildings similar to the tested kind.

Ventilation through open doors is a simple way to temporarily enhance ventilation of indoor spaces, with the purpose to evacuate indoor air pollutants or to adjust the indoor temperature. In churches and other historical buildings, which otherwise are ventilated only through air infiltration, temporarily enhanced ventilation through open doors or windows may be a prudent deed after e.g. services involving large congregations and burning of candles or incense. In the present study, the air exchange occurring at single-sided ventilation through the external doors of five historical churches is measured by tracer gas decay method. Further, air velocity measurements and smoke visualization in a doorway are performed. Measurement results are compared with predictions attained from four previously developed models for single‐sided ventilation. Models that include terms for wind turbulence yielded somewhat better predictions. According to the performed measurements, the magnitude of one hour single-sided open-door airing in a church is typically around 50% air exchange, indicating that this is a workable ventilation method, also for such large building volumes. A practical diagram to facilitate estimation of a suitable airing period is also presented. The study adds particularly knowledge to the issue of airing through doors, in large single zones.

Air infiltration in ancient churches and other historical and monumental buildings is of great importance considering moisture transfer, energy consumption, thermal comfort and indoor surface soiling. Two of the most established models for simulatingand predicting air infiltration in buildings are the Lawrence BerkeleyLaboratory (LBL) model and the Alberta air Infiltration Model (AIM-2). The applicability of these models in superimposing wind and buoyancy driven infiltration in large single zone buildings such as churches are evaluated in this study by comparing model predictions with field measurements in a 19^thcentury stone church. Both tested air infiltration models yielded significant positive correlations between measured and predicted data, and it is concludedthat the AIM-2 model works better than the LBL model for the studied church. Both models tend however to over-predict the air infiltration rate significantly. The over‑predictions were larger in cases with high wind speed and it seems that the models are more fragile in wind dominating conditions. Inclusion of crawl space coefficients in the AIM-2 model improved however the predictions, especially at high wind speeds. It seems that models of the tested kind can be useful in predicting air infiltration in churches and similar buildings, but that some empirically attained model coefficients might need some adjustment to suit this kind of buildings better.

Energy use on heating, ventilation and air conditioning (HVAC) accounts for about 50% of building energy use. To have a sustainable built environment, energy efficient ventilation systems that deliver good indoor environmental quality are needed. This study evaluates the cooling energy saving potential of a newly proposed ventilation system called Intermittent Air Jet Strategy (IAJS) and compares its performance against a mixing ventilation (MV) system in a classroom located in three cities with different climates, Singapore with ‘hot and humid’, Ahvaz with ‘hot and dry’ and Lisbon with “moderate” climate. The results show a significant reduction of cooling energy need and flexibility in control strategies with IAJS as a primary system in hot and humid climates like Singapore. Hot and dry climate with short cool periods like Ahvaz show possible application and considerable energy savings with IAJS as a primary system under optimized variable setpoints, but moderate climates have an increased risk of occupant discomfort likely due to increased draft especially during the cool season.  Thus, IAJS as a secondary system that operates only during cooling season may be conducive for moderate climates like Lisbon. Additionally, the results show that supply fan energy savings can also be realized if well implemented. 

The effect of mechanical night ventilation on thermal comfort and electricity use for cooling of a typical historic office building in north-central Sweden was assessed. IDA-ICE simulation program was used to model the potential for improving thermal comfort and electricity savings by applying night ventilation cooling. Parametric study comprised different outdoor climates, flow rates, cooling machine’s coefficient of performance and ventilation units’ specific fan power values. Additionally, the effect of different door schemes (open or closed) on thermal comfort in offices was investigated. It was shown that night ventilation cannot meet the building’s total cooling demand and auxiliary active cooling is required, although the building is located in a cold climate. Night ventilation had the potential in decreasing the percentage of exceedance hours in offices by up to 33% and decreasing the total electricity use for cooling by up to 40%. More electricity is saved with higher night ventilation rates. There is, however, a maximum beneficial ventilation rate above which the increase in electricity use in fans outweighs the decrease in electricity use in cooling machine. It depends on thermal mass capacity of the building, cooling machine´s coefficient of performance, design ventilation rate, and available night ventilation cooling potential (ambient air temperature).

Night ventilation is a technique in which the indoor air and the building’s thermal mass is cooled down during nighttime to provide a heat sink available during the next day to help mitigating overheating and reducing the daytime space cooling demand. This paper proposes a framework on evaluating the use of mechanical night ventilation today and in the future. It considers analysis of the ventilative cooling system, including mechanical night ventilation, by means of key performance indicators that involve thermal comfort, energy use and resiliency criteria as suggested by IEA Annex 80. It, additionally, introduces an economic parameter in form of diurnal and nocturnal price ratio of electricity as economic trade-off between nighttime fan- and daytime fan and chiller use in terms of electricity. A historic office building in north-central Sweden is presented as a detailed case as to illustrate the use of the framework. The investigation was done using a validated model of the building in IDA-ICE building simulation program at both current climate and future climate in 2050s. It was revealed that an upgraded ventilative cooling system with three times larger capacity is required to fulfill thermal comfort. Even though mechanical night ventilation could result in the annual cooling source electricity saving intensity up to 0.9 kWh/(m²∙a) at extreme current climate (2018), it could just insignificantly reduce the total electricity use for space cooling (up to 2 %) and only at some night ventilation rates at all mentioned climates. Mechanical night ventilation, however, could be applied in an economically beneficial way if the electricity network has different nocturnal and diurnal electricity prices. A unitless index of maximum nighttime over daytime electricity price ratio was proposed representing the maximum tolerable price for nighttime electricity, given a daytime electricity price, based on night- and daytime ventilation electricity demand. For economically justified application of mechanical night ventilation, lower nighttime over daytime electricity price ratios were required for higher night ventilation rates. For the typical future climate with night ventilation rates larger than 2.6 ACH, it will be necessary to have nighttime prices that are lower than daytime if mechanical night ventilation is to be economical. The approach used in the framework can be applied to future research and practice, regardless of the case-specific parameters such as building type, climate zone, location, etc.

This study aims at assessing how well a mechanical night ventilation of today, will cope with delivering acceptable thermal comfort while minimizing the electricity use and the electrical peak power demand for cooling in a historic office building in Sweden at both typical current climate and typical future climate in 2050s. The method includes numerical study in IDA-ICE simulation program using the typical current and future climate profiles. The results show that, for coefficient of performance of 3 and specific fan power of 1.5 kW/(m3/s), it would be possible to lower the electrical peak power demand and the electricity use in cooling machine by up to 2.2 kW (13%) and 1.4 MWh (48%) by night ventilation rate of 2.1 lit/(s·m2) at typical future climate in 2050s. Corresponding figures for typical current climate are 4.6 kW (36%) and 0.9 MWh (72%) owing to cooler nights and more diurnal temperature differences. 

Bifacial photovoltaic cells can produce electricity from the incoming solar radiation on both sides. Used in combination with concentrating solar technology, bifacial photovoltaic cells can see its electrical output further augmented, thus decreasing the cost per kWh. It is known, however, that the efficiency reduction when these cells are exposed to increased temperatures is a relevant factor. This can happen, for example, when they are mounted on a glassed collector or receiver. In this study, a thermal analysis is carried out on four prototypes of concentrating collectors with bifacial PV cells. Results show that, as expected, when glass and gables are removed from the collector, much better heat dissipation is achieved, thus resulting in favorable cell operation conditions.

The movement of people and other objects indoors may affect airflow patterns and velocities near local exhaust ventilation hoods, and consequently has influence on the hoods’ ability to remove locally emitted contaminants and on ventilation energy requirements. In this study, such disturbance effects have been studied experimentally and numerically, with the movements consisting of a human-sized plate, cylinder and detailed manikin, respectively, making back-and-forth movements near an exhaust hood. In the experimental part of the study, a 3-D sonic anemometer was used to measure air velocity in front of the hood opening. The numerical simulations used dynamic mesh to handle object movements. The numerical results were validated against the experimental ones and yielded supplementary results on the air flow field. The results show that the turbulence produced by the objects movements included marked air velocity peaks – both assisting and impeding the suction flow – in the near field of the exhaust hood. The generated turbulence, and particularly those peaks, proved substantially larger in the case of plate movement than with cylinder and manikin movement. Overall the results indicate that a moving cylinder represents human movement better than a moving plate, and thus that it’s better to use a cylinder in some test standards that now stipulate a plate as moving object. A Percentage of Negative Velocity (PNV) parameter was introduced for assessing the capture efficiency of the local exhaust system. The PNV represents the percentage of time that the air flow is directed away from the exhaust hood in an imagined point of contaminant release. The study includes test cases where the PNV values were significantly above zero, suggesting a strong effect on the capture efficiency of the exhaust hood. Human induced turbulence that cause such reverse air flows and overall impedes hood suction may be counteracted by enhanced exhaust flow rate, but then at higher energy consumption.

In local exhaust ventilation systems, external turbulence from e.g. human movements can affect the capture efficiency of the system considerably. In this study, experimental and numerical (CFD) approaches were utilized to evaluate the effect of human movement on the capture efficiency of a local exhaust ventilation system with an exterior circular hood. Human movements were simulated by back-and-forth movements of three human-sized moving objects: a flat plate (CFD + experimental), a cylinder (CFD) and a human-shaped manikin (CFD), respectively. The experiments consisted of tracer gas measurements in a full-scale test room. The numerical simulations included dynamic mesh methods to handle object movements. The results showed reasonable agreement between numerical and experimental results regarding the capture efficiency at different movement frequencies and exhaust flow rates, indicating that CFD is a feasible method for investigating complex flows of the studied kind. In comparison with the moving manikin, the moving plate caused significantly lower capture efficiency, whereas the moving cylinder yielded higher values. Overall, the results with the cylinder as moving object proved more similar to those of the manikin than the results with the flat plate. These findings have particular relevance towards existing test standards that stipulate the use of a moving flat plate in similar test situations. Further, some parameter variations verified that local exhaust capture efficiency increases by increasing the exhaust air flow rate and movement time interval, and also by decreasing the distance between contaminant source and exhaust hood opening. Also increasing the distance between the movable object and the contaminant source, as well as decreasing the diameter of the exhaust hood opening increased the capture efficiency.

The air leakage of the building envelope of ancient churches and other historical and monumental buildings has impact on energy consumption, thermal comfort, humidity and indoor surface soiling. To measure the air leakage in such large and naturally ventilated single-zone buildings is however challenging, especially due to wind and buoyancy (stack) induced disturbances. This study describes experiences in this regard, attainedat field tests where the fan pressurization technique (“Blower door”) was employed. Reference is made to the European test standard EN 13829. Also results of wind-tunnel tests are utilized. It is shown that both buoyancy and wind at commonly occurring conditions can cause significant uncertainty in fan pressurization tests, and that some of the directions in the standard might need to be strengthened or amended. While the uncertainty in measured air leakage rate at the standard (high) pressure of 50 Pa may be small, the predictions of the air leakage rate occurring at realistically (low) indoor-outdoor pressures tend to suffer from significant uncertainty. That uncertainty is then conveyed to later utilizations of the test results, e.g. building energy modeling and prediction. It is also shown that the wind induced pressure at buildings like churches extends a considerable way out into the surroundings of the building; in the order of two times the building height. This has particular importance when choosing a reference point for outdoorpressure measurement.

Prolonged and/or extreme heat has become a natural hazard that presents a significant risk to humans and the buildings, technologies, and infrastructure on which they have previously relied on to provide cooling. This paper presents a conceptual model of a resilient cooling system centred on people, the socio-cultural-technical contexts they inhabit, and the risks posed by the temperature hazard. An integrative literature review process was used to undertake a critical and comprehensive evaluation of published research and grey literature with the objective of adding clarity and detail to the model. Two databases were used to identify risk management and natural hazard literature in multiple disciplines that represent subcomponents of community resilience (social, economic, institutional, infrastructure and environment systems). This review enabled us to characterise in more detail the nature of the temperature hazard, the functionality characteristics of a resilient cooling system, and key elements of the four subsystems: people, buildings, cooling technologies and energy infrastructure. Six key messages can be surmised from this review, providing a guide for future work in policy and practice.

Photovoltaic (PV) panels and thermal collectors are commonly known as mature technologies to capture solar energy. The efficiency of PV cells decreases as operating cell temperature increases. Photovoltaic Thermal Collectors (PVT) offer a way to mitigate this performance reduction by coupling solar cells with a thermal absorber that can actively remove the excess heat from the solar cells to the Heat Transfer Fluid (HTF). In order for PVT collectors to effectively counter the negative effects of increased operating cell temperature, it is fundamental to have an adequate heat transfer from the cells to the HTF. This paper analyzes the operating temperature of the cells in a low concentrating PVT solar collector, by means of both experimental and Computational Fluid Dynamics (CFD) simulation results on the Solarus asymmetric Compound Parabolic Concentrator (CPC) PowerCollector (PC). The PC solar collector features a Compound Parabolic Concentrator (CPC) reflector geometry called the Maximum Reflector Concentration (MaReCo) geometry. This collector is suited for applications such as Domestic Hot Water (DHW). An experimental setup was installed in the outdoor testing laboratory at G&auml;vle University (Sweden) with the ability to measure ambient, cell and HTF temperature, flow rate and solar radiation. The experimental results were validated by means of an in-house developed CFD model. Based on the validated model, the effect of collector tilt angle, HTF, insulation (on the back side of the reflector), receiver material and front glass on the collector performance were considered. The impact of tilt angle is more pronounced on the thermal production than the electrical one. Furthermore, the HTF recirculation with an average temperature of 35.1C and 2.2 L/min flow rate showed that the electrical yield can increase by 25%. On the other hand, by using insulation, the thermal yield increases up to 3% when working at a temperature of 23 C above ambient.

Ventilation and infiltration caused by wind are difficult to predict because they are non-local phenomena: driving factors depend on the surrounding terrain and neighbouring buildings and on the building orientation with respect to the wind direction. Wind-driven flow through an opening is complex because wind can flow through the opening or around the building, in contrast to buoyancy driven flow. We explored wind and air infiltration phenomena in terms of pressure distributions on and around buildings, stagnation points, flow along façades, drag forces, and air flow through openings. Field trials were conducted at a 19^th-century church, and wind tunnel tests were conducted using a 1:200 scale model of the church and other models with openings.

The locations of stagnation points on the church model were determined using particle image velocimetry measurements. Multiple stagnation points occurred. The forces exerted on the church model by winds in various directions were measured using a load cell. The projected areas affected by winds in various directions were calculated using a CAD model of the church. The area-averaged pressure difference across the church was assessed. A fairly large region of influence on the ground, caused by blockage of the wind, was revealed by testing the scale model in the wind tunnel and recording the static pressure on the ground at many points. The findings of this study are summarized as a number of steps that we suggest to be taken to improve analysis and predictions of wind driven flow in buildings.

The study investigates the impact of improved synthetic amorphous silica, specifically developed aerogel-based insulating coatings, Quartzene (Qz), on energy efficiency in buildings across cold and warm climate zones. Simulations were conducted on various coatings and thicknesses for exterior and interior wall surfaces, as well as roofs. These were evaluated using a prototype residential building under dynamic thermal conditions. Wall coatings were analyzed, including a base plaster and a mixture with 10%Wt aerogel-based Quartzene. Additionally, three roof coating samples were tested: Qz 12.5%Wt, TiO2 3.3%Wt, and a blend of aerogel-based mixtures and TiO2. Mixtures containing Qz exhibited the lowest thermal conductivity (0.05 W/(m·K)) and high short-wave reflectance (up to 0.93 μm), impacting transmission loads, time lag, and decrement factor. Energy savings of up to 11% were observed in warm climates when implementing the coatings (unaged performance). Overall, the coated surfaces increased time lag and reduced decrement factor compared to uncoated surfaces. Aerogel-based coatings showed enhanced effectiveness in lowering transmission loads.

This study is framed around two research questions to 1) investigate the probable changes in future climate and 2) evaluate the changes in cooling demand of a studied building when implementing an assemble climate representing mid-term future period (2041-2060). The chosen building is a preschool in central Sweden that fulfills the Nearly-Zero Energy Building (NZEB) requirements based on today’s Swedish National Building Regulations. To assess and cope with the present and future cooling energy needs of the building, a climate file representing present conditions along with a projected future typical climate file are utilized. The future climate is an assembled typical meteorological year climate file using the CORDEX data. 

The present climate file underpredicts the future energy demands therefore verifying to be unsuitable for anticipated energy analysis. It was discovered that the cooling demand for assembled climate file is almost 4 times the present climate file for the studied conditions. 

The changes in climate and the expected extreme climate conditions in the future, given the long life span of the buildings have pushed the design limits. In this study, the changes in primary energy use (PEPET), total energy use and CO2 emission were investigated for a prototype residential building. The building fulfils nearly zero energy building (NZEB) characteristics, imposed by the Swedish building regulations. Different cooling technologies and various typical meteorological year (TMY) climate files assembled for different periods, as well as automatic shading were investigated. The assembled TMY files advocated for the present (2001-2020) and mid-future (2041-2060) period using the CORDEX data. Different cooling methods and set-points (24-28°C) were defined to evaluate the cooling energy requirement changes.

It was discovered that the freely available typical climate file fails to cover the induced changes in climate and its extreme implications on the building. The required cooling energy use increased from 1.7-5.8 times the freely available climate file, when using the projected TMY and the extreme climate files.

Addition of automatic shading system reduced cooling energy up to 75% within the studied cooling methods and set-points. Moreover PEPET and CO2 emission also decreased for the studied cooling methods, climate and weather files.

This chapter investigates the implementation of district cooling systems by exploring several research studies reported in the literature. The topics addressed include typologies and design parameters, benefits and limitations, applications of the system, and the technology readiness level. District cooling systems are generally regarded as cost-efficient and environmentally friendly solutions. One might think that district cooling is only a solution for areas with a very warm climate. However, based on the reported results of the surveyed studies, the number of operating district cooling systems has increased over the years, with the Scandinavian countries taking the lead in this market within European countries. Implementation of these systems concluded reduction in primary energy and electricity use, they also proved to be an environmentally efficient way.

In this study, the performance of different cooling technologies from energy and economicperspectives were evaluated for six different prototype residential Nearly Zero Energy Buildings(NZEBs) within a planned future city district in central Sweden. This was carried out by assessingthe primary energy number and life cycle cost analysis (LCCA) for each building model and coolingtechnology. Projected future climate file representing the 2050s (mid-term future) was employed.Three cooling technologies (district cooling, compression chillers coupled/uncoupled with photovoltaic (PV) systems, and absorption chillers) were evaluated. Based on the results obtained fromprimary energy number and LCCA, compression chillers with PV systems appeared to be favorableas this technology depicted the least value for primary energy use and LCCA. Compared to compression chillers alone, the primary energy number and the life cycle cost were reduced by 13%, onaverage. Moreover, the district cooling system was found to be an agreeable choice for buildingswith large floor areas from an economic perspective. Apart from these, absorption chillers, utilizingenvironmentally sustainable district heating, displayed the highest primary energy use and life cycle cost which made them the least favorable choice. However, the reoccurring operational cost fromthe LCCA was about 60 and 50% of the total life cycle cost for district cooling and absorption chillers,respectively, while this value corresponds to 80% for the compression chillers, showing the high netpresent value for this technology but sensitive to future electricity prices.

The increase in population and living standards, as well as global warming and heatwaves due to climate change, have created a challenge to meet the cooling demand in buildings. In this study, the cooling requirement for a multifamily building through simulations in a future city district in central-Sweden was determined. Different air supply set point  strategies, window to floor ratio and building rotations were employed to minimize the cooling requirements. The building was modelled so as to meet the Nearly Zero Energy Building (NZEB) requirements. Window to floor ratio of 10% with a piecewise proportional controller for supply temperature was depicted as appropriate for the building. A 45° rotation of the building increased the cooling demand. The cooling demand of the building increased by employing the extreme climate condition, as a representative for future climate, with factors 3.8 and 6.4 for cooling set points 25°C and 27°C for window to floor ratio 10%. This implies the need for a resilient building to withstand future climate conditions. The requirement to update the climate files was also used for decision making in the design process and building regulation. 

The increase in population and living standards, as well as global warming and heatwaves due to climate change, have created a challenge to meet the cooling demand in buildings. In this study, the cooling requirement for a multifamily building through simulations in a future city district in central-Sweden was determined. Different air supply set point strategies, window to floor ratio and building rotations were employed to minimize the cooling requirements. The building was modelled so as to meet the Nearly Zero Energy Building (NZEB) requirements. Window to floor ratio of 10% with a piecewise proportional controller for supply temperature was depicted as appropriate for the building. A 45° rotation of the building increased the cooling demand. The cooling demand of the building increased by employing the extreme climate condition, as a representative for future climate, with factors 3.8 and 6.4 for cooling set points 25°C and 27°C for window to floor ratio 10%. This implies the need for a resilient building to withstand future climate conditions. The requirement to update the climate files was also used for decision making in the design process and building regulation. 

This study investigates different cases to obtain optimal Window-to-Wall ratio (WWR) in seven different climate conditions based on the Köppen–Geiger climate classification. The optimal WWR was decided based on the minimum amount of total energy use (total of cooling, heating, and lighting energy use) of a building model during a complete year. The impact of overhang and automatic blinds were assessed on the optimization of WWR for a building with integrated automatic lighting control. Moreover, three different windows with different U-values and features were employed in order to analyze their effect on the energy use and WWR of the building. IDA-Indoor Climate and Energy (IDA-ICE) was used to carry out the simulations. The software has been validated based on ASHRAE Standard 140. Based on each climate condition, orientation, employed window type, and comfort conditions, an optimal range with a specific combination of window with blind, overhang, or neither was found.

Production, management, use, and end-of-life of buildings has a large impact on climate change. Therefore, environmental targets are set to lower the greenhouse gas (GHG) emissions from the building sector. To reach these targets building regulation and voluntary environmental assessment methods (EAMs) that evaluate and certify the building's environmental impact are put forward as tools to push the building sector towards lower GHG emissions. In Sweden, building design is governed by building regulations and the dominant EAM is ‘Miljöbyggnad’ (MB) (“Environmental building”). Today, more than 1900 buildings have been certified by MB and it has influenced the building and property sector. In this chapter the potential impact MB and the linked Swedish building regulations have on building performance, energy use and GHG emissions, will be reviewed and discussed. The analysis investigates several of the MB’s indicators, evaluate to what degree EAMs can influence the design of the building and the energy system to lower the energy use and GHG emissions based on material choices. The analysis presents important aspects that may influence the design of the building and its energy system and what challenges and possibilities the indicators, criteria and regulations can have on buildings and climate change. In addition, some modification and suggestion for improvements are presented.

Samhällsbyggnadssektorn i Sverige står för en betydande andel av landets utsläpp av växthusgaser. I ett led att styra branschen mot en mer hållbar riktning har Boverket fått i uppdrag att underlätta införandet av klimatdeklaration vid nybyggnation. Redan i januari nästa år, 2022, föreslås att nya krav på redovisning av klimatdeklaration vid uppförande av nya byggnader införs för de som söker bygglov. Men vad innebär redovisning av klimatdeklaration?

Validated by wind tunnel data, this study numerically investigates the integrated impacts of wind and thermal buoyancy on urban turbulence, ventilation and pollutant dispersion in full-scale 2D deep street canyons (aspect ratio AR = H/W = 3 and 5, W = 24 m). Isothermal urban airflows for such deep street canyons can be Reynolds-number-independent when reference Reynolds number (Re) exceeds the critical Re (Rec~106,107 when AR = 3, 5), i.e. AR = 5 experiences two main vortices and one-order smaller NEV* (~10−3, the normalized net escape velocity) than AR = 3 with a single main vortex (NEV*~10−2). With sufficiently large Re (Re > Rec) and the same air-wall temperature difference (Ri = 2.62, 4.36 when AR = 3, 5), four uniform wall heating patterns were considered, including leeward-wall heating (L-H), windward-wall heating (W–H), ground heating (G-H), and all-wall heating (A-H). Various indicators were adopted to evaluate street ventilation and pollutant dilution capacity (e.g. age of air (τ,s), NEV*, pollutant transport rates (PTR)). Full-scale wall heating produces a strong upward near-wall buoyancy force, which significantly influences flow patterns and improves street ventilation for most cases. When AR = 3, L-H strengthens the single-vortex airflow. When AR = 5, L-H converts the isothermal double vortices into a single-clockwise vortex. For both ARs, W–H reverses the main clockwise vortex to an enhanced counterclockwise one, moreover G-H and A-H cause a more complicated multi-vortex pattern than isothermal cases. Overall, when AR = 3, L-H and W–H increase NEV* by 68% and 40% than the isothermal case. When AR = 5, four wall heating patterns all raise NEV* considerably (by 150%–556%). For both ARs, the L-H, W–H and A-H amplify the contribution of mean flows on removing pollutants but reduce that by turbulent diffusion compared with isothermal cases.

The global effects of climate change will increase the frequency and intensity of extreme events such as heatwaves and power outages, which have consequences for buildings and their cooling systems. Buildings and their cooling systems should be designed and operated to be resilient under such events to protect occupants from potentially dangerous indoor thermal conditions. This study performed a critical review on the state-of-the-art of cooling strategies, with special attention to their performance under heatwaves and power outages. We proposed a definition of resilient cooling and described four criteria for resilience—absorptive capacity, adaptive capacity, restorative capacity, and recovery speed —and used them to qualitatively evaluate the resilience of each strategy. The literature review and qualitative analyses show that to attain resilient cooling, the four resilience criteria should be considered in the design phase of a building or during the planning of retrofits. The building and relevant cooling system characteristics should be considered simultaneously to withstand extreme events. A combination of strategies with different resilience capacities, such as a passive envelope strategy coupled with a low-energy space-cooling solution, may be needed to obtain resilient cooling. Finally, a further direction for a quantitative assessment approach has been pointed out.