Numeric study of geothermal borehole heat exchanger enhancement via phase change material macro encapsulation

his article addresses the theoretical effect of using geothermal boreholes enhanced with macro-encapsulated phase change materials (PCM) employed with a ground sourced heat pump (GSHP). The aim being the improvement of the heat pump performance through soil temperature stabilisation, taking advantage from the PCM inherent property of changing phase at a constant temperature, that can be matched with the temperature of the surrounding soil, contributing as well to increase the energy storage capacity underground. The numeric work studied different PCM thermal parameters with regards to their influence on the overall behaviour of the heat pump, with different operation modes (On/Off and Inverter) changing the solidus and liquidus temperatures and phase change enthalpy values. The CFD results showed that, while it underperformed having 0.15% difference in the best of cases (specifically the On/Off mode), it used in the best case scenario only 30% of the stored energy in the PCM. The application of macro-encapsulation did provide a stabilising effect to the soil and heap pump operation as it was originally intended to do, helping reduce energy expenditure by the system. Significant modifications are needed in order to improve, both concerning geometry and encapsulation techniques to overcome the PCM and other materials thermal limitations.info:eu-repo/semantics/publishedVersio

Geothermal energy use, country update for Portugal

Trabalho apresentado em European Geothermal Congress 2022, Berlin, Germany, 17-21 October 2022The presence of high-temperature geothermal resources, and the production of electricity from geothermal resources in Portugal, are restricted to the volcanic islands of the Azores Archipelago located in the North Atlantic Ocean. Three geothermal binary power plants are installed and running normally in the islands of S. Miguel and Terceira, the most economically developed, with a total capacity running of 26 MWe and an average production of about 200 GWh/year. The total production of those power plants in 2021 represented about 20 % of the total demand of the Azores archipelago. New nine vertical and directional wells were drilled in 2021 in both islands to increase the total running capacity of power plants, or at least saturate them, especially the Pico Alto geothermal power plant, Terceira Island. Following the call released in 2018 for geothermal projects, sponsored by the FAI – “Fundo de Apoio à Inovação”, to promote the use of geothermal resources in Portugal, namely the low enthalpy resources associated with Thermal Baths/Spas facilities, two district heating networks for hotels and public buildings are under completion: (i) Chaves (74 oC, 25 l/s) and (ii) S. Pedro do Sul (67 oC, 19.4 l/s). Furthermore, in Chaves, an independent small operation (110 kWth) was open in January 2022 in an emblematic museum located over an impressive former Roman Thermal Bath with innovations regarding the environmental management of the geothermal fluid and its disposal.Concerning GSHPs, the potential is huge and continues to be exploited, with new projects ongoing and new specific regulations are expected to be approved shortly. There are a few installations registered until now, but the technical data of the operations are scarce and do not represent the totality of what is installed in Portugal.N/

Portugal country update 2020

Trabalho apresentado em World Geothermal Congress 2020, Reykjavik, Iceland, April 26 – May 2, 2020, moved to October, 2021N/

Assessment of the exploitation potential of hydromineral and geothermal resources and their use for temperatures above 25°C

Trabalho apresentado em XI Congresso Nacional de Geologia 2023,17-19 de julho de 2023, Coimbra, PortugalEnergy sustainability presents challenges as how to reduce resource consumption and how to make better use of renewable ones. For this purpose, the characterization of the existing endogenous resources is essential. The aim of this project was to evaluate the exploitation potential of hydromineral and geothermal resources and their use for temperatures above 25°C, in 39 concessions. The results allowed verifying that it is possible to optimize the use of energy contained in hydromineral resources in most concessions, namely in space heating, domestic hot water production and swimming pool water heating, as well as in buildings in the surrounding area, such as houses, hotels, swimming pools and greenhouses. This study was carried out as part of a project financed by Fundo de Apoio à Inovação, for and with the support of the DGEG and is intended to be a first approach to allow concessions carry out more detailed studies adapted to their reality.N/

Effect of fins and nanoparticles in the discharge performance of PCM thermal storage system with a multi pass finned tube heat exchange

This work studies the heat exchange process of a latent heat thermal energy storage (LHTES) system equipped with a compact finned tubes heat exchanger (HE) as this is one of the most important aspects of the storage system, the capacity for effectively delivering its stored energy. This work fills in a literature gap for 3D, transient heat transport fluid (HTF) flow models concerning storage systems with phase change materials (PCMs) with fins and nanoparticles allowing for an evaluation on the quality of heat delivered by the system. Numerical simulations, for full turbulent conditions of the HTF flow, were developed to access the influence of the fin pitch and the PCM thermal properties in the performance of the energy discharge process. Samples of commercial paraffin-wax A53 doped with graphene based nanoplatelets were tested and characterised. Different types of nanoplatelets were employed in the range of 0.5% to 6% weight. Measured data of the thermal conductivity, specific heat and fusion latent heat are presented. The simulations were developed for three fin pitch values 5 , 10 and 20 mm and for 1%wt and 6%wt nanoparticles loads. The effect of fins and combination of fins and nanoparticles in the outlet temperature and liquid fraction distribution inside the LHTES unit during the discharge process in a 3D full scale model was analysed. The system performance was evaluated based of off the outlet temperature of HTF to ascertain both the quantity and quality of the heat provided. The results show that the PCM thermal conductivity is significantly enhanced by the addition of graphene nanoparticles with a high aspect ratio. The addition of only 1%wt doubled the solid phase PCM thermal conductivity and for a 6%wt load the thermal conductivity increased by a factor of 3.5. Meanwhile, specific and latent heat values of the samples are relatively unaffected. The numerical results further show that applying thin fins is an effective approach to enhance LHTES systems discharge performance. Increasing the fin number significantly enhances the heat transfer rate and the HTF discharge temperature during solidification and has a positive impact in the useful discharge heat capacity, providing better quality heat. Combining fins and nanoparticles improves the discharge process, nevertheless the role of nanoparticles becomes secondary as the fins number increases. The results demonstrate that standardised compact finned heat exchangers ubiquitously used in the HVAC industry can successfully overcome the low thermal conductivity of common PCMs without compromising the useful heat discharge capacity or resorting to nanoparticles decreasing the discharge time between 60 and 77% with adequate fin number.info:eu-repo/semantics/publishedVersio

Latent thermal energy storage application in a residential building at a mediterranean climate

An innovative thermal energy storage system (TESSe2b) was retrofitted in a residential building in Cyprus with a typical Mediterranean climate. The system comprises flat-plate solar collectors, thermal energy storage tanks filled with organic phase change material, a geothermal installation consisting of borehole heat exchangers with and without phase change material and a ground source heat pump, an advanced self-learning control system, backup devices and several other auxiliary components. The thermal energy storage tanks cover the building’s needs at certain temperature ranges (10–17 ◦C for cooling, 38–45 ◦C for heating and 50–60 ◦C for domestic hot water). A performance evaluation was conducted by comparing the TESSe2b system with the existing conventional heating and cooling system. The systems were simulated using commercial software, and the performance of the systems and the building’s energy needs were calculated. Based on the energy quantities, an economic analysis followed. The equivalent annual primary energy consumption with the conventional system resulted in being 43335 kWh, while for the storage system, it was only 8398 kWh. The payback period for the storage system was calculated to be equal to 9.76 years. The operation of the installed storage system provided data for calculations of the seasonal performance factor and storage performance. The seasonal performance factor values were very high during June, July and August, since the TESSe2b system works very efficiently in cooling mode due to the very high temperatures that dominate in Cyprus. The measured stored thermal energy for cooling, heating and domestic hot water resulted in being 14.5, 21.9 and 6.2 kWh, respectively. Moreover, the total volume of the phase change material thermal energy storage tanks for heating and domestic hot water was calculated to be roughly several times smaller than the volume of a tank with water as a storage medium.info:eu-repo/semantics/publishedVersio

Organic Farming e-book

A agricultura biológica está-se a tornar cada vez mais importante como um caminho preferencial para a produção de produtos agrícolas, face à crescente procura do mercado mundial. A relevância da agricultura biológica é ainda maior, devido à necessidade e procura de produtos agrícolas de origem biológica, que são isentos de produtos químicos, saudáveis e amigos do ambiente. Atualmente, a agricultura biológica resulta em produtos de valor acrescentado, mas estes sistemas de produção exigem abordagens especializadas. Verifica-se uma lacuna de conhecimento especializado para enfrentar os desafios e exigências da agricultura biológica. Além disso, um número crescente de pessoas com níveis elevados de educação está a mudar a sua atividade para a agricultura sem qualquer tipo de formação nesta área técnica, principalmente em países com dificuldades económicas, como Portugal. Há, portanto, necessidade de desenvolver a capacidade de pessoas com algum tipo de qualificação prévio, a fim de melhorar suas competências agrícolas e facilitar a sua capacidade de desempenho e inovação, para que possam contribuir para a Estratégia Europeia (CE) de Desenvolvimento Rural. Este e-book foi concebido para melhorar as competências desses agricultores. O seu objectivo geral é dotar os novos agricultores com conhecimentos e capacidades necessários para o desenvolvimento da cadeia de valor dos produtos da agricultura biológica. Os objectivos específicos são: i) Fornecer conhecimento básico em vários aspectos da agricultura biológica e áreas afins, tais como a gestão de recursos naturais (solo, água, plantas, ambiente) e desenvolvimento rural (conservação, agricultura biológica e familiar, multifuncionalidade). ii) Facilitar a troca efetiva de conhecimento e experiências em agricultura biológica, desenvolvimento rural e ambiente. iii) Oferecer suporte técnico e conhecimento em agricultura biológica num contexto de mobilidade e em ambiente de trabalho. Este e-livro, produzido em sete idiomas diferentes (Português, Inglês, Espanhol, Italiano, Eslovaco, Turco e Húngaro) também contribui para preservar línguas e culturas Europeias e, assim, melhorar a comunicação entre os diferentes intervenientes e grupos-alvo. O e-book inclui os princípios e técnicas da agricultura biológica, com base no triângulo planta-solo-ambiente e nas relações entre a produção animal e o ambiente. A preparação de alimentos e rotulagem, marketing e conversão à agricultura biológica são também abordados. Os princípios e as técnicas apresentadas são explicados com base em regras e diretrizes (normas), baseados numa abordagem logística que garante o equilíbrio e integridade do sistema. O e-book apresenta também os regulamentos e normas nacionais e Europeias que são obrigatórias para os agricultores biológicos.info:eu-repo/semantics/publishedVersio

Local hydrological conditions influence tree diversity and composition across the Amazon basin

Tree diversity and composition in Amazonia are known to be strongly determined by the water supplied by precipitation. Nevertheless, within the same climatic regime, water availability is modulated by local topography and soil characteristics (hereafter referred to as local hydrological conditions), varying from saturated and poorly drained to well-drained and potentially dry areas. While these conditions may be expected to influence species distribution, the impacts of local hydrological conditions on tree diversity and composition remain poorly understood at the whole Amazon basin scale. Using a dataset of 443 1-ha non-flooded forest plots distributed across the basin, we investigate how local hydrological conditions influence 1) tree alpha diversity, 2) the community-weighted wood density mean (CWM-wd) – a proxy for hydraulic resistance and 3) tree species composition. We find that the effect of local hydrological conditions on tree diversity depends on climate, being more evident in wetter forests, where diversity increases towards locations with well-drained soils. CWM-wd increased towards better drained soils in Southern and Western Amazonia. Tree species composition changed along local soil hydrological gradients in Central-Eastern, Western and Southern Amazonia, and those changes were correlated with changes in the mean wood density of plots. Our results suggest that local hydrological gradients filter species, influencing the diversity and composition of Amazonian forests. Overall, this study shows that the effect of local hydrological conditions is pervasive, extending over wide Amazonian regions, and reinforces the importance of accounting for local topography and hydrology to better understand the likely response and resilience of forests to increased frequency of extreme climate events and rising temperatures

Geography and ecology shape the phylogenetic composition of Amazonian tree communities

Aim: Amazonia hosts more tree species from numerous evolutionary lineages, both young and ancient, than any other biogeographic region. Previous studies have shown that tree lineages colonized multiple edaphic environments and dispersed widely across Amazonia, leading to a hypothesis, which we test, that lineages should not be strongly associated with either geographic regions or edaphic forest types. Location: Amazonia. Taxon: Angiosperms (Magnoliids; Monocots; Eudicots). Methods: Data for the abundance of 5082 tree species in 1989 plots were combined with a mega-phylogeny. We applied evolutionary ordination to assess how phylogenetic composition varies across Amazonia. We used variation partitioning and Moran\u27s eigenvector maps (MEM) to test and quantify the separate and joint contributions of spatial and environmental variables to explain the phylogenetic composition of plots. We tested the indicator value of lineages for geographic regions and edaphic forest types and mapped associations onto the phylogeny. Results: In the terra firme and várzea forest types, the phylogenetic composition varies by geographic region, but the igapó and white-sand forest types retain a unique evolutionary signature regardless of region. Overall, we find that soil chemistry, climate and topography explain 24% of the variation in phylogenetic composition, with 79% of that variation being spatially structured (R$^{2}$ = 19% overall for combined spatial/environmental effects). The phylogenetic composition also shows substantial spatial patterns not related to the environmental variables we quantified (R$^{2}$ = 28%). A greater number of lineages were significant indicators of geographic regions than forest types. Main Conclusion: Numerous tree lineages, including some ancient ones (>66 Ma), show strong associations with geographic regions and edaphic forest types of Amazonia. This shows that specialization in specific edaphic environments has played a long-standing role in the evolutionary assembly of Amazonian forests. Furthermore, many lineages, even those that have dispersed across Amazonia, dominate within a specific region, likely because of phylogenetically conserved niches for environmental conditions that are prevalent within regions

Geography and ecology shape the phylogenetic composition of Amazonian tree communities

AimAmazonia hosts more tree species from numerous evolutionary lineages, both young and ancient, than any other biogeographic region. Previous studies have shown that tree lineages colonized multiple edaphic environments and dispersed widely across Amazonia, leading to a hypothesis, which we test, that lineages should not be strongly associated with either geographic regions or edaphic forest types.LocationAmazonia.TaxonAngiosperms (Magnoliids; Monocots; Eudicots).MethodsData for the abundance of 5082 tree species in 1989 plots were combined with a mega-phylogeny. We applied evolutionary ordination to assess how phylogenetic composition varies across Amazonia. We used variation partitioning and Moran's eigenvector maps (MEM) to test and quantify the separate and joint contributions of spatial and environmental variables to explain the phylogenetic composition of plots. We tested the indicator value of lineages for geographic regions and edaphic forest types and mapped associations onto the phylogeny.ResultsIn the terra firme and várzea forest types, the phylogenetic composition varies by geographic region, but the igapó and white-sand forest types retain a unique evolutionary signature regardless of region. Overall, we find that soil chemistry, climate and topography explain 24% of the variation in phylogenetic composition, with 79% of that variation being spatially structured (R2 = 19% overall for combined spatial/environmental effects). The phylogenetic composition also shows substantial spatial patterns not related to the environmental variables we quantified (R2 = 28%). A greater number of lineages were significant indicators of geographic regions than forest types.Main ConclusionNumerous tree lineages, including some ancient ones (>66 Ma), show strong associations with geographic regions and edaphic forest types of Amazonia. This shows that specialization in specific edaphic environments has played a long-standing role in the evolutionary assembly of Amazonian forests. Furthermore, many lineages, even those that have dispersed across Amazonia, dominate within a specific region, likely because of phylogenetically conserved niches for environmental conditions that are prevalent within regions