Southern European Climate Research Articles

A Meta-Analysis Approach to Estimate the Effect of Cover Crops on the Grain Yield of Succeeding Cereal Crops within European Cropping Systems

Farming practices such as cover cropping, crop rotation systems, and soil tillage practices, along with climate conditions and soil type play important roles in determining final crop production. Numerous empirical studies have documented the heterogeneous effects of cover crops on the yield of successive crops, exhibiting variations across diverse regions, climate regimes, soil characteristics, cover crop types, and agricultural management practices. A meta-analysis was conducted to comprehensively summarize and evaluate the impact of cover crops (CCs) in the agroecosystem. The main goal of the study is to promote a transition towards more sustainable cereal crop production by exploring the potential of currently unexploited CCs in Europe. The study demonstrated that the incorporation of legume CCs resulted in the most pronounced and statistically significant increase in grain yield among cereal crops. CCs from the Brassicaceae family also demonstrated a positive impact on grain yield under southern European climates. Cover cropping had a positive effect on the subsequent cash crop under conventional tillage practice. A positive, but not significant impact, was detected under both conservation tillage practices, which include reduced tillage (RT) and no-till (NT). The result of the study suggests that NT practices are more suitable for Northern Europe, while RT practices are preferable for Southern Europe zones. This study indicates that the adoption of cover cropping represents a viable and effective agronomic strategy for enhancing grain yield in cereal crops cultivated across European agricultural systems.

Penultimate interglacial palynology of Flanders: A revised river evolution model

There are no Saalian Stage pollen records in Northwest Europe that not only cover an entire interglacial complex but also have been successfully correlated down to marine isotope substage level. The presented pollen record fills this knowledge gap. Three pollen sequences, sampled from a well-preserved Saalian Stage river terrace near Brussels (Belgium), together span most of an interglacial complex: two interglacial cycles and one interstadial separated by colder intervals. To date the pollen data, the authors present a multi-proxy supported river evolution model through which the correlation of the pollen record with the penultimate interglacial complex (Marine Isotope Stage (MIS) 7) becomes apparent. The authors further illustrate homotaxis—defined as the similarity between pollen diagrams that are not necessarily contemporaneous—by comparing MIS 7 with MIS 5 pollen data from the same area, convincingly curve-match the pollen record with marine isotope data, and point to similarities between Southern and Northwest European vegetation dynamics and climate variability during MIS 7.

‘A Paradise of Invalids’

Nineteenth-century Madeira was a popular destination for wealthy British people suffering from consumption and other pulmonary ailments. A rich store of sources from the period provide first-hand accounts of invalids on the island or offer special advice for the invalid traveller. After positioning medical travel within the context of contemporary science about climate, health and acclimatization, this article will provide a brief account of existing sources related to medical travel to Madeira. This article then examines this material for what it reveals about contemporary ideas about the Madeiran climate upon health, as well as cultural interaction between the British and the island. In particular, the article will trace how writing about Madeira conforms or diverges from popularly held views about the southern European climate and southern European people, as well as what resonance such views may have in the present.

The Impact of Thermal Inertia on the Indoor Thermal Environment of Light Steel Framing Constructions

Typically, reinforced concrete and brick masonry construction is the most common construction system of the majority of the southern European residential building stock. However, the lightweight steel framing (LSF) construction system has been progressively assuming a relevant position in the residential sector. Since LSF is not the traditional construction system, the indoor thermal environment of these buildings has not been widely studied and discussed considering the southern European climate context. The low thermal inertia of this construction system is commonly pointed to as a possible weakness in warmer climates. The present work aims to address this research gap by evaluating and comparing the LSF and masonry construction systems in terms of the indoor thermal environment focusing on the level of thermal inertia. The considered methodology lies in a long-term experimental campaign based on the construction and monitoring of two identical experimental test cells, differing only in the construction system. The test cells are in the central region of Portugal. The monitoring period elapsed over an entire year. Dynamic simulations are also carried out with a model experimentally validated to consider a wider range of climatic conditions. It is shown that internally insulating the ground floor has an impact on the indoor thermal environment of the LSF test cell by accentuating the indoor air temperature fluctuations and magnitude of the extreme peak values. However, the results also reveal that the faster and closer response to the outdoor conditions may be beneficial for LSF buildings during the heating season.

Dynamic Modelling and Validation of an Air-to-Water Reversible R744 Heat Pump for High Energy Demand Buildings

This paper presents a reversible heat pump based on CO2 as the refrigerant, able to provide heating, cooling, and domestic hot water to high energy demand buildings. The unit was developed and tested under the EU H2020 project MultiPACK, which has the main goal of assuring the market about the feasibility, reliability, and energy efficiency of CO2 integrated systems for heating and cooling and promoting a fast transition to low environmental impact solutions. Within the project, the confidence raising was performed by installation and monitoring of fully integrated state-of-the art CO2 systems in the Southern European Climate. With the aim of predicting the unit behaviour under variable load and boundary conditions, a dynamic model of the entire unit was developed with commercial software, considering actual components and the implemented control system and it was validated with experimental data, collected at the factory’s lab before commissioning. The validation against experimental data collected during operation as a heat pump demonstrated a maximum percentage difference between the experimental and predicted value of gas–cooler heat flow rate equal to +5.0%. A preliminary comparison with the experimental data in chiller configuration is reported, however further development was required to achieve a satisfactory validation. Lastly, the numerical model was utilized to simulate a typical operation in heat pump configuration with the system coupled with a hot water tank storage for the production of domestic hot water and space heating; the model predicts higher COP when operating in domestic hot water operation due to the lower water inlet temperature.

Impact of atmospherical stability and intra-hour variation of meteorological data in the variability of building air change rates

In contrast with structural engineering, where the focus for design is on extreme values, for the proper assessment and modelling of air change rates in natural ventilation and infiltration, one must use the full range of input variables. Most of the modelling in infiltration research relies on hourly datasets for air infiltration balance. This consideration overlooks the intra-hour variability on meteorological variables. Additionally, it is customary to assume unchanging neutral atmospheric conditions when modelling, which affects the calculated airflows. This work intends to detail and quantify these effects in a case study representative of an average single-family dwelling in a Southern European climate setup. By comparing four setups with an increasing degree of complexity, a median of 0.04 h−1 of the hourly standard deviations in air change rates (ACH) is attributed to the time step effect. Approximately 43% of the occurrences experienced non-neutral atmospheric stability, skewing for stable conditions. This effect contributed to differences in the ACHs ranging from −0.202 to 0.131 h−1 at the 5% and 95% quantiles. Overall, by using hourly uniform distributions and smart sampling of meteorological variables, one ensures that the values in between and others potentially occurring around the boundaries are being considered for air change rates calculation, and therefore providing a more detailed picture of actual conditions.

Indoor Thermal Environment Challenges of Light Steel Framing in the Southern European Context

Over the past decades, Southern European residential architecture has been typically associated with heavyweight hollow brick masonry and reinforced concrete construction systems; however, more industrialised alternative systems have been gaining a significant market share, such as the light steel framing (LSF). Regardless of the proliferation of LSF buildings, a lack of experimental research studies have been performed on this construction system in terms of the indoor thermal environment and thermal comfort in the Southern European climate context. Moreover, a research gap also exists regarding experimental comparisons with typical brick masonry buildings. The present study focused on this research gap by characterising and comparing the performance of these two construction systems. A long-term experimental campaign was carried out, involving the construction and monitoring of two identical test cells, differing only by construction system. The test cells were located in Portugal and were monitored over an entire year. The results revealed that the LSF experimental test cell presented higher daily indoor air temperature fluctuations, leading to more extreme maximum and minimum values, closely following the outdoor dry bulb temperature variations. The more responsive behaviour was also reflected in the indoor thermal comfort analysis, with the LSF cell presenting slightly worse performance; however, some advantages were also observed regarding the LSF construction system, which could provide benefits during intermittent residential occupation, especially in mild climates, in which overheating is not a major concern.

Contrasting northern and southern European winter climate trends during the Last Interglacial

Abstract The Last Interglacial (LIG; 130–115 ka) is an important test bed for climate science as an instance of significantly warmer than preindustrial global temperatures. However, LIG climate patterns remain poorly resolved, especially for winter, affected by a suite of strong feedbacks such as changes in sea-ice cover in the high latitudes. We present a synthesis of winter temperature and precipitation proxy data from the Atlantic seaboard of Europe, spanning from southern Iberia to the Arctic. Our data reveal distinct, opposite latitudinal climate trends, including warming winters seen in the European Arctic while cooling and drying occurred in southwest Europe over the LIG. Climate model simulations for 130 and 120 ka suggest these contrasting climate patterns were affected by a shift toward an atmospheric circulation regime with an enhanced meridional pressure gradient and strengthened midlatitude westerlies, leading to a strong reduction in precipitation across southern Europe.

Opportunities of Light Steel Framing towards thermal comfort in southern European climates: Long-term monitoring and comparison with the heavyweight construction

In a climate such as the southern European, heavyweight buildings have been associated with improved indoor comfort conditions. The heavyweight reinforced concrete and brick masonry construction is the most widespread and technically known constructive system. However, alternative lightweight systems have been gaining market share, such as the Light Steel Framing (LSF). Experimental research focused on the comparison between the two constructive systems is yet scarce.The present work intends to focus on this research gap by analysing and comparing the performance of the two constructive systems in terms of indoor thermal environment and thermal comfort, considering an intermittent residential occupation. To this end, a robust experimental campaign was carried out, based on the construction and monitoring of two identical experimental test cells, differing only in the constructive system. The test cells are located in Portugal and were monitored for one full year.It is shown that the LSF constructive system presents higher daily indoor temperature fluctuation and more expressive peak values, following closer the outdoor dry-bulb temperature variations. The obtained results also evidence the opportunities of the LSF constructive system in terms of indoor thermal comfort, presenting, in general terms, a more promising scenario on the performed annual analyses.

The applicability of nearly/net zero energy residential buildings in Brazil – A study of a low standard dwelling in three different Brazilian climate zones

Buildings account for 34% of world energy consumption and about half of electricity consumption. The nearly/Net Zero Energy Building (nZEB/NZEB) concepts are regarded as solutions for minimizing this problem. The countries of Southern Europe, which included the nZEB concept recently in their regulatory requirements, have both heating and cooling needs, which adds complexity to the problem. Brazil may benefit from their experience since most of the Brazilian climate zones present significant similarities to the Southern European climate. Brazil recently presented a household energy consumption increase, and a growing trend in the use of air conditioning is predicted for the coming decades. Simulations with various wall and roof solutions following the Brazilian Performance Standard were carried out in a low standard single-family house in three different climate zones in order to evaluate thermal comfort conditions and energy needs. Results show that in milder climate zones, achieving thermal comfort with a low energy consumption is possible, and there is a great potential to achieve a net zero-energy balance. In the extreme hot climate zone, a high cooling energy consumption is needed to provide thermal comfort, and the implementation of a nearly zero-energy balance may be more feasible.

Eco-efficiency in early design decisions: A multimethodology approach

Eco-efficiency is a key concept encompassing economic and environmental aspects to promote a more efficient use of resources and lower emissions. An eco-efficiency perspective in the design of products and services is thus essential in the pursuit of sustainability. This article proposes a novel decision-support methodological approach to assess the environmental impacts and costs in early design stages, aimed at providing informed recommendations to designers, manufacturers and decision-makers. This multimethodology approach integrates a streamlined life-cycle environmental and cost assessment with a data envelopment analysis (DEA) model that derives eco-efficiency ratios and compares alternative designs, without the need to subjectively weigh the different environmental and cost life-cycle metrics. A linear regression model is then used to indicate the most influential decision variables. This approach was applied to a retrofit process of a historic residential building located in Southern Europe. The metrics used to assess the design parameters are: climate change, acidification, eutrophication, non-renewable primary energy, and net present value. A sensitivity analysis on the decarbonization of the electricity mix was also performed. The multimethodology offers valuable guidance to allow decision-makers to progressively specify the decision variables in an iterative way, using robust methods allowing for the statistical validation of results. The case study revealed robust empirical results for building retrofits in Southern European climates, indicating that the variables that most impact eco-efficiency (in both short and long-term) are roof insulation thickness and material followed by exterior wall insulation material. After three variables specification, the average eco-efficiency always increased, with higher gains obtained for the scenarios with the current electricity mix (22–25% increase) and more modest gains obtained for the electricity decarbonization scenarios (8–15% increase).

Assessment of test methods for the durability of thermal mortars exposure to freezing

Thermal mortars are a trend in the construction industry in recent years, owing to the required decrease of the thermal transmission of building envelopes. The high porosity of thermal mortars leads to permeability values that can affect their durability since it creates more favourable conditions for the penetration of aggressive agents. Water is observed as one of the most common and harmful degradation agents. Regarding the climatic variability in Europe, freezing is a usual degradation mechanism both in severe and moderate climates. Since thermal mortars have higher water absorption than a common insulation, the freezing may occur. As no durability assessment methodologies to evaluate the exposure of thermal mortars to freezing degradation mechanisms exist, the present work has the objective to analyse existing accelerated ageing procedures, which envisage freezing degradation mechanism. As such, the durability assessment described in EN 1015-21 and ETAG 004 was adapted and implemented in different thermal mortars. It was observed that the higher number of cycles and the severity of the freeze–thaw ageing cycles, according to ETAG 004, may reproduce the effect of the northern European climates, while the ageing cycles, described in EN 1015-21, combine degradation mechanisms that occur in central and southern European climates. This adaptation allowed collecting reliable data and inputs to the development of durability assessment methodologies directly applicable to thermal rendering and plastering systems.

Experimental energy performance assessment of a solar desiccant cooling system in Southern Europe climates

Solar desiccant cooling systems, SDEC, could be an effective alternative to conventional cooling systems, which mainly depend on electrical energy. The main objective of this work was to determine experimentally the seasonal coefficient of performance, SCOP, of a SDEC system composed of a desiccant wheel, an indirect evaporative cooler and a thermal solar system, to control indoor conditions in a research lab room. The dependence of coefficient of performance on outdoor air conditions and percentage of renewable energy used by the SDEC system were also analysed. Experimental tests were carried out for six weeks during spring and summer seasons in Martos, Spain.The experimental results showed that the SDEC system independently adjusted the temperature and humidity of the supply air. 75% of the energy consumed by this air handling system comes from renewable sources. A seasonal coefficient of performance of the SDEC system of 2 was obtained for the period analysed. It is shown that the higher the outdoor temperature, the higher instantaneous COPs is. These results suggest that the use of SDEC systems in hot climates, such as southern European climates, could contribute to achieve the EU's energy goals within the frame of Nearly Zero Energy Buildings.

Optimisation of a high-efficiency solar-driven organic Rankine cycle for applications in the built environment

Energy security, pollution and sustainability are major challenges presently facing the international community, in response to which increasing quantities of renewable energy are to be generated in the urban environment. Consequently, recent years have seen a strong increase in the uptake of solar technologies in the building sector. In this work, the potential of a solar combined heat and power (CHP) system based on an organic Rankine cycle (ORC) engine is investigated in a domestic setting. Unlike previous studies that focus on the optimisation of the ORC subsystem, this study performs a complete system optimisation considering both the design parameters of the solar collector array and the ORC engine simultaneously. Firstly, we present thermodynamic models of different collectors, including flat-plate and evacuated-tube designs, coupled to a non-recuperative sub-critical ORC architecture that delivers power and hot water by using thermal energy rejected from the engine. Optimisation of the complete system is first conducted, aimed at identifying operating conditions for which the power output is maximised. Then, hourly dynamic simulations of the optimised system configurations are performed to complete the system sizing. Results are presented of: (i) dynamic 3-D simulations of the solar collectors together with a thermal energy storage tank, and (ii) of an optimisation analysis to identify the most suitable working fluids for the ORC engine, in which the configuration and operational constraints of the collector array are considered. The best performing working fluids (R245fa and R1233zd) are then chosen for a whole-system annual simulation in a southern European climate. The system configuration combining an evacuated-tube collector array and an ORC engine is found to be best-suited for electricity prioritisation, delivering an electrical output of 3,605 kWh/year from a 60 m2 collector array. In addition, the system supplies 13,175 kWh/year in the form of domestic hot water, which is equivalent to more than 6 times the average annual household demand. A brief cost analysis and comparison with photovoltaic (PV) systems is also performed, where despite the lower PV investment cost per kWel, the levelised energy costs of the different systems are found to be similar if the economic value of the thermal output is taken into account. Finally, a discussion of the modelled solar-CHP systems results shows how these could be used for real applications and extended to other locations.

Concrete solar collectors for façade integration: An experimental and numerical investigation

Precast concrete cladding systems can be converted into concrete solar collectors by embedding pipes within the exposed concrete, providing a unique building integrated solar thermal solution. Past research of non-integrated, roof-attached concrete solar collectors have largely focused on experimental studies in high temperature climates and/or simulation studies using simplified 1D and 2D models. This study (1) Experimentally investigates the performance of a façade integrated concrete solar collector in a mid-latitude European climate (Dublin) and (2) Develops and validates a 3D numerical model which is then used to predict the performance of other façade integrated concrete solar collectors in other European climates. The study primarily quantifies the performance in relation to the energy output and the solar fraction. The experimental set-up of the concrete solar collector is designed to represent a south facing façade installation. The experimental results showed that one quarter of the annual hot water demand of a single occupant dwelling could be provided using 1m2 of concrete solar collectors with spring and autumn months producing the highest daily energy outputs; attributed to the vertical orientation of the concrete solar collectors. A 3D numerical model of the vertically installed concrete solar collector is developed in COMSOL Multiphysics and validated against the experimentally measured results. The validated model is used to expand the study to different collectors and systems, as well as two additional contrasting Northern and Southern European climates where precast concrete is a popular cladding material, namely Helsinki and Sofia. The simulation results showed that the solar absorptance, flow rate, collector area and pipe length have a significant influence on the performance of the concrete solar collector system. Annual solar fractions of 20% (Helsinki), 24% (Dublin) and 30% (Sofia) are predicted for a small apartment building using a façade integrated concrete solar collector. The concrete solar collectors presented a negligible influence on the interior environment provided sufficient insulation is located at the back of the concrete absorber, as would be typical of a precast concrete sandwich panel construction.

Photovoltaic-thermal hybrid collector performance for direct trigeneration in a European building retrofit case study

This article compares the annual energetic, exergetic and economic performance of a combined (hybrid) photovoltaic-thermal collector system (PVT) to that of a system with separate solar thermal and photovoltaic collectors. Furthermore, energy saving potentials through refurbishment of the building envelope are investigated. The analysis is based on simulations with an experimentally validated PVT model. The major novelty of the study is that the water based PVT collectors are also used for long wave radiative cooling. Three different residential case study buildings from Central to Southern European climate zones are investigated. Their heat, cooling and electricity demand, as well as their renewable supply, are determined along with savings through the envelope measures. In general, the performance of the PVT system varies strongly with the boundary conditions of the demand profile, climate situation and energy price levels. The results demonstrate that PVT collectors used for heat (primary DHW) and electricity offer approximately 6–7 percentage points higher exergetic efficiency than thermal and PV collectors equally sharing the available surface area. Raising the temperature level for cooling by 4K increases the amount of renewable cooling by a factor 2–4. The analysis shows that the economic performance of the trigeneration PVT system is only better than separate generation if the additional electricity and cooling generate enough benefit to compensate the loss of heat gains. Especially in the Portuguese location of Almada, with high electricity price levels and high enough cooling demand, the application of PVT in a trigeneration system is recommendable from an exergetic and economic point of view.

Natural ventilation and indoor air quality in educational buildings: experimental assessment and improvement strategies

Indoor environmental conditions in classrooms, in particular temperature and indoor air quality, influence students’ health, attitude and performance. In recent years, several studies regarding indoor environmental quality of classrooms were published and natural ventilation proved to have great potential, particularly in southern European climate. This research aimed to evaluate indoor environmental conditions in eight schools and to assess their improvement potential by simple natural ventilation strategies. Temperature, relative humidity and carbon dioxide concentration were measured in 32 classrooms. Ventilation performance of the classrooms was characterized using two techniques, first by fan pressurization measurements of the envelope airtightness and later by tracer gas measurements of the air change rate assuming different envelope conditions. A total of 110 tracer gas measurements were made and the results validated ventilation protocols that were tested afterward. The results of the ventilation protocol implementation were encouraging and, overall, a decrease on the CO2 concentration was observed without modifying the comfort conditions. Nevertheless, additional measurements must be performed for winter conditions.

Cooling potential of natural ventilation in representative climates of central and southern Europe

ABSTRACTThis study analyses the climate-dependent passive ventilative cooling (PVC) potential in central and southern Europe. This analysis was carried out in two phases: (1) evaluation of PVC potential as a climate-dependent variable, in different locations representative of European climate zones for both wind-drive airflow (comfort ventilation) and temperature gradient (environmental and structural cooling); (2) verification of the above PVC potential through dynamic energy simulations on a reference-building model located in selected cities. In the first phase, a parametrical analysis on the typical meteorological year of 55 European cities was carried out considering a new synthetic parameter – ‘residual CDH’ (CDHres) – representing the potential reduction of cooling degree hours due to PVC. In the second phase, the PVC potential was assessed through dynamic energy simulations on an office-building unit located in a sample of locations (10), varying building envelop physical parameters and VAC system configurations. Results show that PVC is an effective strategy for reducing cooling energy consumption in buildings in central and southern European climates. Furthermore, dynamic simulations demonstrate that internal heat capacity has an important role in PVC potential and validate the climatic analysis, especially when temperature gradient is taken into account.

Pilot scale land-based cultivation of Saccharina latissima Linnaeus at southern European climate conditions: Growth and nutrient uptake at high temperatures

Saccharina latissima is a cold water seaweed species with commercial potential. The northern Portuguese coast is the southern distribution limit of the species, where some dispersed populations can be found. S. latissima has been identified as being a potential candidate for monoculture or as part of integrated multi-trophic aquaculture (IMTA) systems, presenting good results considering both growth and biofiltration performance. In the present work, the cultivation of S. latissima in a pilot land-based system was performed in order to assess the efficiency of two different methods: tumbling in the water column vs attached to fixed ropes at the bottom of the tank. S. latissima cultivated in tumble culture presented the best results, reaching growth rates of 10.6±0.9%day−1 and 0.9±0.1cmday−1, with a weekly yield around 120gDWm−2. Cultivation using this method was continued over the summer, for assessment of S. latissima growth at warmer temperatures. Average weekly yield ranged between 44.7 and 146.3 (average 110) gDWm−2 from April to mid-May; from mid-May to mid-July a high variability was observed, when some negative values indicating biomass loss were obtained and from mid-July onwards, average weekly yield ranged between 36.7 and 78.3gDWm−2. These results showed that tank cultivation of S. latissima in tumble culture was possible throughout the summer, withstanding average temperatures around 20°C from May onwards, well above published optimum temperatures for this species. This fact may be explained by their origin in populations located near the southern distribution boundary, which may have acquired adaptations that increased tolerance to high temperatures. Cultivation of S. latissima using tumble culture in outdoor tanks at southern latitudes appears to be feasible even during high temperature periods. Densities around 8kgm−3 were effective in keeping epiphytes development low. This system may be used for seaweed monoculture or as a biofilter component of IMTA systems. Statement of relevanceThe present manuscript is relevant for commercial land-based aquaculture of S. latissima, a high commercial value species, as a monoculture or as a part of an integrated multitrophic aquaculture system, since it presents information directly applicable to commercial installations due to its pilot scale trials.

Energy Storage Requirements for PV Power Ramp Rate Control in Northern Europe

Photovoltaic (PV) generators suffer from fluctuating output power due to the highly fluctuating primary energy source. With significant PV penetration, these fluctuations can lead to power system instability and power quality problems. The use of energy storage systems as fluctuation compensators has been proposed as means to mitigate these problems. In this paper, the behavior of PV power fluctuations in Northern European climatic conditions and requirements for sizing the energy storage systems to compensate them have been investigated and compared to similar studies done in Southern European climate. These investigations have been performed through simulations that utilize measurements from the Tampere University of Technology solar PV power station research plant in Finland. An enhanced energy storage charging control strategy has been developed and tested. Energy storage capacity, power, and cycling requirements have been derived for different PV generator sizes and power ramp rate requirements. The developed control strategy leads to lesser performance requirements for the energy storage systems compared to the methods presented earlier. Further, some differences on the operation of PV generators in Northern and Southern European climates have been detected.