Proposal of a principle cum scale analytical framework for analyzing agroecological development projects

Because agroecology has different meanings, it may be used in an arbitrary and potentially abusive way when deployed by development cooperation actors conceiving “agroecology-based” development projects. To make the appropriation of agroecology more transparent, we first review the recent attempts in academia to clarify the concept and identify two main trends: a principle-based agroecology and a series of different agroecologies. Based on a critical assessment of these attempts, we then propose a new framework to program, implement and analyze agroecological development projects: it distinguishes different agroecologies with their corresponding categories of principles and their scales of intervention. Further, we argue in favor of a specific category of methodological principles.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Community owned solutions for fire management in tropical ecosystems:case studies from Indigenous communities of South America

Fire plays an increasingly significant role in tropical forest and savanna ecosystems, contributing to greenhouse gas emissions and impacting on biodiversity. Emerging research shows the potential role of Indigenous land use practices for controlling deforestation and reducing CO2 emissions. Analysis of satellite imagery suggests that Indigenous lands have the lowest incidence of wildfires, significantly contributing to maintaining carbon stocks and enhancing biodiversity. Yet, acknowledgement of Indigenous peoples’ role in fire management and control is limited, and in many cases dismissed, especially in policy-making circles. In this paper, we review existing data on Indigenous fire management and impact, focusing on examples from tropical forest and savanna ecosystems in Venezuela, Brazil and Guyana. We highlight how the complexities of community owned solutions for fire management are being lost as well as undermined by continued efforts on fire suppression and firefighting, and emerging approaches to incorporate Indigenous fire management into market, incentive-based for climate change mitigation. Our aim is to build a case for supporting Indigenous fire practices within all scales of decision-making by strengthening Indigenous knowledge systems to ensure more effective and sustainable fire management

Formulation of a 1D finite element of heat exchanger for accurate modelling of the grouting behaviour: Application to cyclic thermal loading

This paper presents a comprehensive formulation of a finite element for the modelling of borehole heat exchangers. This work focuses on the accurate modelling of the grouting and the field of temperature near a single borehole. Therefore the grouting of the BHE is explicitly modelled. The purpose of this work is to provide tools necessary to the further modelling of thermo-mechanical couplings. The finite element discretises the classical governing equation of advection-diffusion of heat within a 1D pipe connected to ground nodes. Petrov-Galerkin weighting functions are used to avoid numerical disturbances. The formulation is able to capture highly transient and steady-state phenomena. The proposed finite element is validated with respect to analytical solutions. An example consisting of a 100 m depth U-pipe is finally simulated. A first continuous heating simulation highlights the nonsymmetric distribution of temperature inside and near the borehole. An estimation of the error on the results as a function of the resolution parameters is also carried out. Finally simulations of cyclic thermal loading exhibit the need to take into account all daily variations if the grouting behaviour must be modelled. This is true especially in case of freeze-thaw damaging risk.Geotherwa

Addressing the knowledge gaps in agroecology and identifying guiding principles for transforming conventional agri-food systems

Today’s society faces many challenges when it comes to food production: producing food sustainably, producing enough of it, distributing food, consuming enough calories, consuming too many calories, consuming culturally-appropriate foods, and reducing the amount of food wasted. The distribution of power within the current mainstream agri-food system is dominated by multinational agri-businesses that control the flow of goods and wealth through the system. This hegemony has implemented a regime whose structures reinforce its control. A growing response to the current agri-food regime is the rise of agroecology, in both developed and developing country contexts. This is not a new phenomenon, but it has evolved over time from its Latin American origins. However, agroecology is not a monolithic block and represents many different perceptions of what it means to advance agroecology and ways in which it can help today’s society tackle the crisis of the agri-food system. This paper addresses these sometimes discordant view points, as well as the gaps in our knowledge regarding agroecology in an effort to lay out some guiding principles for how we can move forward in transforming the current agri-food system to achieve sustainability and a more equitable distribution of power and resources

Optimierung von oberflächennahen geschlossenen geothermischen Systemen

Vertical ground source heat pump systems have been established as the preferred geothermal technology for providing space heating and cooling to both small and large buildings. This technology utilizes shallow geothermal energy by extracting or injecting heat through a borehole heat exchanger (BHE). In large-scale applications, heat transfer is accomplished by using a field of multiple BHEs. Standard design practices for large-scale applications are based on equal operation of the BHEs. Moreover, groundwater often influences the thermal transport in the ground, but it is rarely considered. In the presented work, the potential of individual adjustment of BHEs for different hydro-geothermal conditions is investigated. Special attention is given to the subsurface temperature changes exerted by the operation of the BHEs. The main question is whether the concerted energy extraction of multiple BHEs can be improved, and how. For tackling this question, two simulation-optimization procedures are developed. The first procedure uses superimposed analytical models to simulate ground temperature impacts from operating multiple adjacent BHEs. The predictions of the models are used to evaluate an objective function to optimize individual BHE operation in the field. This is solved within a linear programming framework. Two real-case oriented application cases for heating energy supply are considered. In the first application case, the presence of groundwater flow is neglected, while for the second case, various groundwater flow regimes are considered. Temperature distributions from optimized and non-optimized BHEs, for given operation times, are then compared by comprehensive numerical models. In general, optimized BHEs can reduce the thermal impact, and extreme local cooling can be avoided. In the purely conductive case, the maximum ground temperature change is decreased by 18% compared to the non-optimized field. For the advection-dominated cases, even when flowing groundwater balances local anomalies, the temperature changes in the optimized field are always smaller. Also, the temperature of the circulating heat carrier fluid within the optimized BHEs can be increased by 1°C, which is favourable for improving the heat pump performance. In addition, the optimal adjustment of the boreholes produces characteristic load patterns that depend on time and groundwater flow velocity. The second simulation-optimization approach couples heat transport numerical simulation of geothermal systems with heuristic optimization algorithms. The performance of three evolutionary algorithms (each with 2 variants) is tested for maximizing the total energy extraction of BHE fields installed in a heterogeneous aquifer. In addition, an optimal positioning scheme of the BHEs within a predefined area is inquired. Among the evaluated algorithms, Differential Evolution (with line search, LS-DE) and Particle Swarm Optimization (PSO) perform best. For the given maximum temperature change in the subsurface (2.5 K) optimized solutions can reach substantial energy extraction rates. In comparison, BHE application according to standard planning practice can only reach 33% of the energy extraction of the optimized field.Erdgekoppelte Wärmepumpen mit vertikalen Sonden haben sich als die bevorzugte geothermische Technologie zum Heizen und Kühlen von kleinen und großen Gebäuden etabliert. Dieses Verfahren nutzt oberflächennahe geothermische Energie durch die Extraktion oder Injektion von Wärme über Erdwärmesonden (EWS). Bei großräumigen Anwendungen erfolgt der Wärmetransfer über einem Sondenfeld mit multiplen EWS. In der derzeitigen Praxis der EWS-Planung werden bei großräumigen Anlagen alle EWS in Sondenfeldern auf gleiche Weise betrieben. Zudem wird der Einfluss des Grundwassers auf den Wärmetransport im Untergrund bei der EWS-Planung selten berücksichtigt. Die vorliegende Arbeit untersucht das Potential der individuellen Einstellung der einzelnen EWS für unterschiedliche hydro-geothermale Bedingungen. Ein besonderes Augenmerk wurde hierbei auf die durch den Betrieb der EWS bedingten Temperaturänderungen im Untergrund gelegt. Die Hauptfrage ist, inwieweit der konzertierte Wärmeentzug multipler EWS verbessert werden kann. Für die Erörterung der Frage wurden zwei Simulationsoptimierungsverfahren entwickelt. Das erste Verfahren verwendet superpositionierte analytische Modelle, um die Beeinträchtigung der Grundwassertemperatur durch multiple beieinander liegende EWS zu simulieren. Die Vorhersagen der Modelle werden für die Evaluierung einer Zielfunktion für die Optimierung des Betriebs individueller EWS in einem Sondenfeld genutzt. Dies wird innerhalb eines linearen Programmierungsframework erreicht. Zwei real-case orientierte Anwendungsfälle für die Wärmeversorgung sind berücksichtigt. Im ersten Anwendungsfall ist das Vorhandensein des Grundwasserflusses vernachlässigt, während für den zweiten Fall unterschiedliche Grundwasserströmungsregime berücksichtigt sind. Die Temperaturverteilung der optimierten und nicht-optimierten EWS-Felder wird durch umfassende numerische Modelle verglichen. Im Allgemeinen kann durch optimierte EWS-Felder die thermische Beeinträchtigung reduziert und extreme lokale Abkühlungen verhindert werden. Im rein konduktiven Fall wird der maximale Temperaturunterschied im Untergrund um 18% reduziert. Für die konvektionsdominierten Fälle sind die Temperaturänderungen immer geringer, sogar wenn das Grundwasser die lokalen Temperaturanomalien ausgleicht. Zudem kann die Temperatur der zirkulierenden Wärmetransportflüssigkeit innerhalb der optimierten EWS um 1°C erhöht werden, was für die Verbesserung der Wärmepumpenleistung von Vorteil ist. Darüber hinaus erzeugt die optimale Einstellung der Sonden charakteristische Betriebsmuster, die von der Zeit und der Grundwasserfließgeschwindigkeit abhängig sind. Das zweite Simulationsoptimierungsverfahren koppelt die numerische Simulation des Wärmetransports der geothermischen Systeme mit heuristischen Optimierungsalgorithmen. Die Leistungsfähigkeit von drei evolutionären Algorithmen (mit je zwei Varianten) wird für die Maximierung des Gesamtenergieentzugs der EWS-Felder, die in einem heterogenen Aquifer installiert sind, getestet. Zusätzlich wird ein optimales Positionierungsschema für mehrere EWS innerhalb einer vordefinierten Fläche gesucht. Innerhalb der evaluierten Algorithmen ergeben die Optimierungsmethoden Differential Evolution (mit Linesearch-Verfahren, LS-DE) und Partikel-Schwarm Optimierung (PSO) die besten Ergebnisse. Für die gegebene maximale Temperaturänderung im Untergrund (2,5 K) können optimierte Lösungen beträchtliche Energieextraktionsraten erreichen. Die in der Praxis übliche EWS-Planung kann im Vergleich zu den optimierten EWS-Feldern nur 33% der Energieextraktion erreichen