In 2000, a small group of refugees from Sudan were sponsored by three local churches in Maryville, Tennessee. The churches worked with the Bridge Organization in order to orchestrate the refugees' departure from Africa to Maryville. At the time of their sponsorship, it was believed that the Sudanese population in Maryville would be self-sufficient within two years of arrival. This study uses one-on-one, open-ended interviews and a paper-pencil questionnaire with the Sudanese population and a focus group with the American sponsors to assess the extent that the Sudanese refugee population in Maryville has become self-sufficient. While individual success depends on multitude of variables, the results indicate that in general, the Sudanese community is still struggling with American norms and culture, and, as a result, has not become self-sufficient.

Cuba has a long history of different dependencies and is a country facing many energy challenges, and therefore seeks to diversify its energy sources and reduce its reliance on fossil fuels. The purpose of this degree project is therefore to conceptualize a microgrid based on renewable energy sources for local energy sustainability at the lowest cost possible. For this purpose, the sugar mill Carlos Baliño and its surrounding community, in Villa Clara, Cuba is used for a case study. The currently existing electricity generation at Carlos Baliño is tied to the steam needed to run the sugar production process, which is generated with a back-pressure steam engine. This thesis evaluates the possibility to extend the system including a condensing extraction steam turbine connected to a new generator, solar PV, and wind power by developing and comparing three scenarios for the future. The BASE scenario is the business as-usual case including no changes, the PLAN scenario is based on the plans of installing a 1 MW solar PV power plants, and the APT scenario includes all possible technologies to be part of the system. For all scenarios, the different microgrid configuration were evaluated based on the following key performance indicators; CAPEX, NPV, IRR and DPP of the microgrid, share of electricity supplied from the grid and lastly the emission reduction rate compared to the current system in Carlos Baliño. In addition to the technical, economic, and social perspective, the results are evaluated in relation to the national context and goals. Evolution of microgrids is significant to develop more sustainable power systems. The key advantages of this microgrid solution include reduced greenhouse gas emissions, increased energy independence, and improved resilience in the electricity supply. By utilizing bagasse and renewable energy sources like solar PV and wind, Cuba can reduce its dependence on imported fossil fuels, leading to lower carbon emissions and contributing to global climate change mitigation efforts. Moreover, the integration of bagasse-based cogeneration plants enhances the country's energy resilience by diversifying the energy mix and reducing vulnerability to external energy shocks. The distributed nature of microgrids enables local communities to generate their own clean energy, fostering self-sufficiency and socioeconomic empowerment. The results show negative NPV for the BASE and PLAN scenarios. When including a Condensing Extraction Steam Turbine generator, the electricity supplied from the grid decreases from 30 to 11% for the BASE scenario and even more for the PLAN. Additionally, for the PLAN scenario, the 1 MW solar PV investment in isolation generates a positive NPV of 2.67 million USD indicating a good investment even though the whole system shows infeasibility and should increase the solar PV installation size to become profitable. Lastly, for the APT scenario, the NPV is 59.8 million USD, with an IRR of 11% and payback time of 7 years showing a good investment. However, with a high CAPEX of 41.3 million USD. The emission reduction rate is as high as 92%. Furthermore, a sensitivity analysis is performed to address the uncertainty in different cost parameters affecting the results of the study. And the result shows that the system NPV is most sensitive to the change in cost in bagasse fuel price. In conclusion, the integrated microgrid solution with solar PV and bagasse represents a sustainable and resilient energy option for Carlos Baliño and Cuba in general. By capitalizing on its solar potential and utilizing bagasse as a local biomass resource, Cuba can achieve a greener and more reliable energy system while promoting rural development and reducing carbon footprint. This solution can serve as a blueprint for other regions in Cuba and the Caribbean with similar energy challenges seeking to transition to renewable energy and achieve energy security. / Kuba har en lång historia av olika beroenden och är ett land som står inför många energiutmaningar, och försöker därför diversifiera sina energikällor och minska sitt beroende av fossila bränslen. Syftet med detta examensarbete är därför att konceptualisera ett mikronät baserat på förnybara energikällor för lokal energihållbarhet till längsta möjliga kostnad. För detta ändamål genomförs en fallstudie av sockerfabriken Carlos Baliño och dess närliggande samhälle, i Villa Clara, Kuba. Den nuvarande elproduktionen vid Carlos Baliño är kopplad till den ånga som behövs för att driva sockerproduktionsprocessen, som genereras med en back-pressure turbin. Vårt mål är att utvärdera möjligheten att utöka systemet och inkludera en CEST-generator, solcellsenergi och vindkraft. Dem olika konfigurationerna på mikronätet utvärderas utifrån följande nyckeltal; CAPEX, NPV, IRR och DPP för mikronätet, andel el som levereras från nätet och slutligen utsläppsminskningstakten jämfört med det nuvarande systemet i Carlos Baliño. Utöver det tekniska, ekonomiska och sociala lokala perspektivet utvärderas resultaten i relation till nationella sammanhang och mål. Utvecklingen av mikronätet är viktig för att utveckla mer hållbara kraftsystem. De viktigaste fördelarna med denna mikronätslösning inkluderar minskade växthusgasutsläpp, ökat energioberoende och förbättrad motståndskraft i elförsörjningen. Genom att använda bagass och förnybara energikällor som solenergi och vindkraft kan Kuba minska sitt beroende av importerade fossila bränslen, vilket leder till lägre koldioxidutsläpp och bidrar till globala klimatförändringar. Dessutom förbättrar integrationen av bagass-baserade kraftvärmeverk landets energitålighet genom att diversifiera energimixen och minska sårbarheten för externa energichocker. Mikronätets möjlighet till distribuerad energiproduktion gör det möjligt för lokalsamhällen att generera sin egen rena energi, vilket främjar självförsörjning och socioekonomisk egenmakt.  Resultaten visar en negativ NPV för BASE och PLAN scenarierna. När en Condensing Extraction Steam Turbine generator inkluderas minskar eltillförseln från nätet från 30 till 11% i BASE scenariot och ännu mer för PLAN. Dessutom, för PLAN scenariot, ger 1 MW solcellsinvesteringen en positiv NPV på 2,67 miljoner USD när den beräknas för sig själv, vilket indikerar en bra investering. Däremot är hela systemet inte ekonomiskt möjlig, och bör öka solcellsanläggningens storlek för att bli lönsam. Slutligen, för APT scenariot, är NPV 59,8 miljoner USD, med en IRR på 11% och en återbetalningstid på 7 år, vilket visar på en bra investering. Dessutom med en utsläppsminskningsgraden är så hög som 92%. Dock med en hög CAPEX på 41,3 miljoner USD. Vidare görs en känslighetsanalys för att ta itu med osäkerheten i olika kostnadsparametrar som påverkar studiens resultat. Och resultatet visar att systemets NPV är mest känsligt för förändringen i priset på bagassbränslet. Sammanfattningsvis representerar den integrerade mikronätlösningen med solceller och bagass ett hållbart och motståndskraftigt energialternativ för Carlos Baliño och Kuba i allmänhet. Genom att utnyttja sin solpotential och använda bagass som en lokal biomassaresurs kan Kuba uppnå ett grönare och mer tillförlitligt energisystem samtidigt som det främjar landsbygdsutveckling och minskar koldioxidavtrycket. Denna lösning kan fungera som en plan för andra regioner på Kuba och Karibien med liknande energiutmaningar som försöker gå över till förnybar energi och uppnå energisäkerhet.

The Stockholm Archipelago has a unique natural landscape - rugged nature that blends with wooded islands, rocky cliffs and sandy beaches enriched by cultural and ecological values. The islands, dating back to the Viking Age are faced with a progressively uneven growth compared to the city developing an inevitable socio-economic dependency on the city core through infrastructural connections. Emigration from already diffusely scattered settlements made life unaffordable on the islands for both permanent residents and municipalities. According to official surveys and analyses, the islands claimed to lack a live-work-play balance and social potential that could be developed better for the residents. This struggle is loaded with the seasonal influx of tourists who exploit the landscape, leaving the responsibility for care onto those who live there. This situation added to climate change, strains energy and (water) resources causing summer droughts. All these struggles raise a question for the future - “How can urban planning and design help re-imagine the potential of existing systems to adapt to a more sustainable Archipelago?” The project envisions to transform the fragmented, protected landscape of the Stockholm Archipelago into a continuous productive landscape, bringing meaning to the scattered and dynamic context. With an approach that closely integrates fields of planning, landscape and design, the goal is realised through a three-layered strategy - (1) continuous blue-green systems of resource capture and nutrient circulation, (2) building local economy through collective production and diversification through exchange, and (3) community exchange through robust networking and production as a way of life. For design possibilities on the local scale, the island of Runmaro is explored with the aim of building synergies with the existing context of landscape, mobility networks, food production, resident villages, local businesses and popular landmarks. The idea is to strengthen existing socio-economic nodes while developing new ones through programs offering shared production and exchange, a year-round activation and continuous accessibility (circulation and systemic) that bring continuity to the overall experience.

A growing world population has resulted in an increasing number of people being homeless or living in inadequate housing. In addition, the threatening climate crisis and the world’s limited resources calls for a more sustainable way of living. The organization Stockholm Tiny House Expo aims to contribute a solution to these issues: an artificial island with several tiny houses, able to adapt to rising sea levels, having net-zero-waste and completely self-sufficient regarding energy. This island will symbolize the sustainable development goals and will be an attraction for tourists, as well as create several job opportunities. In order to realize this vision, research needs to be conducted to find solutions to make this island become reality. Therefore, the aim of this project is to evaluate the economic and environmental feasibility of a high degree of self-sufficiency regarding energy, by locally producing heat and power, on an artificial island in Stockholm. Firstly, a literature review is conducted to find suitable technologies to supply the island with heat and power. Subsequently, the software tools IDA ICE and HOMER Pro are used to simulate the energy demand and supply of the island. Eight different scenarios, with different types of supply and demand, are created to investigate different possibilities of the island. The scenarios are evaluated using technical-, economic- and environmental key performance indicators. A scenario where the demand is reduced and heat and power are supplied only by resources on the island, is deemed most relevant based on Stockholm Tiny House Expo’s vision. A sensitivity analysis is therefore performed on this scenario. The results indicate technical and environmental feasibility; however, the economic evaluation showed that this scenario will be non-profitable. Although the scenario is non-profitable, if further measures are taken to create a pricing model to customers, it could be possible. In conclusion, the results of this research indicate that it is possible for Stockholm Tiny House Expo to be self-sufficient regarding heat and power solely utilizing renewable energy. The evaluation of the results, however, showed that it is not economically feasible. In addition, the national grid did not contribute to an impact on the surrounding environment, nor to a considerable amount of greenhouse gas emissions. Hence, grid connection is recommended for Stockholm Tiny House Expo. / En växande världspopulation har resulterat i att ett ökande antal människor är hemlösa eller bor i bristfälliga bostäder. Den hotande klimatkrisen och jordens begränsade tillgångar kräver dessutom en hållbarare livsstil. Organisationen Stockholm Tiny House Expo vill bidra med en lösning till dessa problem: en artificiell ö med flera småhus, som kan anpassa sig till stigande havsnivåer, har noll nettoavfall och är helt självförsörjande gällande energi. Denna ö kommer symbolisera FN:s hållbarhetsmål och vara en turistattraktion så väl som skapa ett flertal arbetsmöjligheter. För att förverkliga denna vision krävs forskning för att hitta lösningar och göra denna ö till verklighet. Därmed är syftet med detta projekt att undersöka den ekonomiska och miljömässiga genomförbarheten av en hög grad av självförsörjning av energi, genom att lokalt producera kraft och värme, på en artificiell ö i Stockholm. Först utförs en litteraturstudie för att hitta lämpliga teknologier för att försörja ön med kraft och värme. Därefter används programvarorna IDA ICE och HOMER Pro för att simulera energibehovet och energiförsörjningen för ön. Åtta olika scenarier, med olika typer av försörjning och behov, konstrueras för att undersöka olika möjligheter för ön. Scenarierna utvärderas med hjälp av tekniska-, ekonomiska- och miljömässiga nyckeltal (key performance indicators). Ett scenario där behovet är reducerat samt att kraft och värme endast försörjs av resurser på ön, bedöms vara mest relevant baserat på Stockholm Tiny House Expos vision. En känslighetsanalys utförs därför på detta scenario. Resultaten tyder på att scenariot är tekniskt och miljömässigt genomförbart; dock visade den ekonomiska utvärderingen att det inte är lönsamt. Trots detta så skulle det kunna vara möjligt om vidare åtgärder tas för att skapa en prissättningsmodell mot kunderna. Sammanfattningsvis så tyder resultaten på att det är möjligt för Stockholm Tiny House Expo att vara självförsörjande gällande kraft och värme som endast utnyttjar förnybar energi. Utvärderingen av resultatet visade dock att det inte är ekonomiskt genomförbart. Det nationella kraftnätet bidrog dessutom inte till påverkan på den omgivande miljön och inte heller någon betydande mängd växthusgasutsläpp. Följaktligen rekommenderas nätanslutning för Stockholm Tiny House Expo.

How can architects let their buildings interact with the water while protecting occupants from the potential danger? The two intents are very different and often compete with one, either protection or recreation, as the primary program in one project. Water draws people, everyone likes being near water. People visit waterfalls and the beach just to experience moving water, they go boating and kayaking just to be on the water. Water views and access are considered an amenity that drive up prices in buildings. Whenever possible architects should strive to connect their architecture and water and to let occupants interact with the water. However, water can be dangerous too. Overfull rivers wash away roads and cars. Floods inundate entire cities, and hurricanes devastate huge islands. In addition to catastrophic damage sea levels are rising around the world causing damage and rendering low lying land uninhabitable. Architects must protect against these dangers. If designed correctly buildings can offer shelter from storms and resist rising water of all kinds. For my thesis I decided to study how to reconcile these two conflicting approaches to water. / Master of Architecture

Photovoltaic technology is among the best tools our civilization has to reduce the emissions of greenhouse gas that are currently altering the atmosphere composition of our planet. The idea of using photovoltaic surfaces on the envelope of buildings is called with the acronym of BIPV (building integrated photovoltaics), it offers the advantage of producing energy in the same location of the demand for electricity. Furthermore, BIPV allows to save monetary and environmental costs by substituting building materials with photovoltaic collectors. As every technology,BIPV follows an adoption pattern that is bringing it from a very limited niche product to a pervasive one. Nevertheless, the adoption rate of BIPV appears to be slow, and the industry has offered little opportunities of business for its stakeholders over the last 20 years. There are multiple reasons for this sluggish growth, and a considerable body of scientific literature has offered potential solutions to the problem. The building industry is notoriously slow in picking up innovation, furthermore the BIPV material needs to compete with much more mature, versatile and often cheaper cladding technologies and materials. Numerous research endeavors are focusing on the development of new BIPV claddings to have diversified colors, dimensions, shapes and other properties. The argument is that the technology is not mature and thus cannot be adopted by the bulk of architects and designers. Unfortunately, the premium characteristics of these new materials often come with a higher price and a reduced efficiency, thus reducing their market potential. Other research endeavors, among which this thesis, are focusing on the design of buildings: trying to include the use of photovoltaics into the architectural practice through education and software development. Numerous software has been developed over the last 20 years with the aim of calculating the productivity or the economic outlook of a BIPV system. The main difference between the existing software and the method presented here lies in the following fact: previously, the capacity and positions of a BIPV system are required as input for the calculation of performance, in this method the capacity and positions of the BIPV system are given as the output of an optimization process. A designer whois skeptical or disengaged about the use of BIPV could be induced to avoid its use entirely by the discouraging simulation results given by the lack of a techno-economic optimal configuration. Conversely, a designer who opt for a premium architectural PV material would, thank to the methodology shown, be able to assess the impact its unitary cost has on the optimal BIPV capacity of the building. Ultimately, the method presented provides new knowledge to the designer regarding the use of BIPV on his building, hopefully this can facilitate the spread of BIPV technology. The method described was translated into a software tool to find the best positions and number of PV surfaces over the envelope of the building and the best associated battery capacity. The tool is based on the combined use of ray-tracing (for irradiation calculation) and optimization algorithms, its use led to the following conclusions: • BIPV is profitable under a wide range of assumptions if installedin the correct capacities • 20% of the residential electric demand can easily be covered by PV without the need for electric storage and in a profitable way • Despite an interesting rate of return of the investment, the payback time was generally found to be long (over 10 years) • More research is needed to assess the risk on the investment on BIPV: if found to be low, future financial mechanisms could increase its spread despite the long payback time • The optimal capacity in energy terms (i.e. the energy consumed on-site minus the energy used to produce a BIPV system) tends to be far higher than any techno-economic optimum • The specific equivalent CO2 emissions for an NPV optimal system have been found to be between 70 and 123 [kg CO2 eq/MWh] under the range of assumptions applied • The installation of optimal BIPV capacity could change the overall residential CO2 emission of -12%, +13%, -29% in England, France and Greece respectively • despite the non optimal placement of a BIPV system compared to a ground mounted, south oriented one, and despite the noncontemporaneity of production and consumption, the BIPV still easily outperforms the energy mix of most countries when optimized for maximum NPV. • The part of the building envelope that have the most annual irradiation (i.e. the roof) should not necessarily host the entirety of the system as other facades might have an advantage in terms of matching production and consumption times. • when different scenarios are made in terms of techno-economic input parameters (e.g. degradation of the system, future costs of maintenance, future variation of electricity price etc..) larger capacities are optimal for optimistic outlooks and vice-versa • the optimal capacity for the expected scenario (i.e. the 50 % ile) can be considered robust as it performs close to the optimum in optimistic and pessimistic scenarios alike. • a reduction in price for the electric storage appears to have a positive effect on the optimal capacity of PV installed for the case study considered. • when a group of households is optimized separately V.S. aggregated together, the aggregation have a huge positive effect on all KPIs of the resulting system: in the NPV optimal system of a case study examined the installed capacity ( +118%), the NPV ( +262.2%) and the self-sufficiency( +51%) improved thanks to aggregation.

No description available.

Ce mémoire vise à mieux comprendre l'utilisation du concept d'autarcie à l'oeuvre dans les écrits d'Aristote et, ce faisant, à nous amener à une meilleure compréhension du lien entre l'éthique et la politique dans la pensée aristotélicienne. Pour ce faire, nous commençons tout d'abord par distinguer deux types d'autarcie, à savoir ce que nous appellerons dans la suite l'autarcie divine et l'autarcie humaine. L'autarcie divine doit être comprise comme le fait de se suffire pleinement à soi-même de la manière la plus rigoureuse qui soit et cette autarcie n'est, à proprement parler, attribuable qu'au divin. L'autarcie humaine, quant à elle, est celle qui est à l'oeuvre dans la définition que donne Aristote de la cité, à savoir qu'elle est un regroupement autarcique de personnes visant à vivre et à bien vivre. Par la suite, nous montrons que la pratique de la philosophie, qui est décrite comme une pratique autarcique en EN, X, est difficilement conciliable avec les activités de la cité et la constitution d'une communauté politique. En effet, comme c'est le besoin qui doit jouer le rôle de ciment de la cité, il est difficile de voir comment la philosophie peut s'insérer dans le cadre étatique de la cité, étant donné qu'elle n'est d'aucune utilité et qu'elle est recherchée pour elle-même. Toutefois, puisqu'Aristote ne présente jamais la cohabitation de la philosophie avec les autres activités de la cité comme problématique, nous tentons de voir comment il est possible de concilier la pratique de la philosophie avec la nécessité pour l'individu de vivre en cité. C'est en examinant la notion de loisir que nous en venons à conclure que la philosophie doit y être reléguée afin de pouvoir être pratiquée. C'est aussi en associant la philosophie au loisir et en étudiant le rôle que celui-ci doit jouer au sein de la cité que nous sommes en mesure de voir se dessiner le lien entre l'éthique et la politique. / This dissertation tries to gain a better understanding of the concept of autarkeia which is present in the writings of Aristotle. Doing this, we are also able to get a clearer idea of the link between ethics and politics in the aristotelian thought. In order to achieve this, we start by distinguishing two types of self-sufficiency : the divine self-sufficiency and the human self-sufficiency. The divine self-sufficiency is to be understood as the fact of being fully self-sufficient in the most rigorous way. Strictly speaking, it is only the divine that can be granted of such a self-sufficiency. On the other hand, the human self-sufficiency is the one effective in the aristotelian definition of the polis, which is the self-sufficient grouping of persons aiming at living and good living. After that, we show that the practice of philosophy, which is described as a self-sufficient activity in NE, X, is hardly possible as an activity of the polis and cannot participate in bringing a polis to life. This is founded in the fact that for Aristotle, it is the needs that keep people together, united in a polis, and considering that, it is difficult to see how philosophy could be part of this, because it is totally useless and searched for itself. However, we try to see how it would be possible to conciliate the practice of philosophy with the necessity for a human to live in a polis, because Aristotle never speaks of it as being problematic. The answer of this so-called problem is to be found in the notion of leisure, by relegating philosophy to this part of a human life in order for it to be practiced. It is also by associating philosophy and leisure that we can draw the link between ethics and politics.

Military Forward Operating Base Camps (FOBs) support and enable sustained military operations abroad by providing safe locations for soldiers and supporting contractors to eat, sleep, and maintain personal hygiene. FOBs need some amount of energy and water to provide these services but are often located in austere environments that do not have access to grid utilities. Off-grid FOBs are not self-sufficient; they are dependent on supply chains for the services they provide to camp occupants. The challenge of supplying FOBs with fuel and water and removing waste (resource resupply and waste removal comprise logistical requirements) is associated with very high human, monetary, strategic, and environmental costs. There are many research efforts across the U.S. Department of Defense (DoD) that seek to reduce FOB logistical requirements, but it is currently very difficult to identify the research efforts that are most beneficial to DoD goals. There are also many factors that make designing FOBs to be more self-sufficient challenging including varying missions, environments, and legacy equipment at currently-fielded FOBs, a lack of baseline data on FOB logistical requirements, an unclear relationship between design changes and resource use behavior, and an unclear valuation of saved resources. This research seeks to develop computer tools and contribute to a methodology that can be used to design FOBs that are more self-sufficient. More self-sufficient FOBs provide high quality services to occupants but do so with mitigated logistical requirements. To this end, a detailed computer model of specific type of FOB (a single 150-person Force Provider module) is developed, and baseline levels of resource requirements are established. Potentially resource-saving devices and other design changes are incorporated into the FOB model and simulated to assess each design change's effect on resource use and waste production. Then, estimated resource savings are weighed against required investment for each design change to arrive at design recommendations. The results of this research effort are specific design recommendations for making the Force Provider system more self-sufficient, as well as computer tools and a methodology that are applicable to other off-grid habitation redesign problems. / text

Ce mémoire vise à mieux comprendre l'utilisation du concept d'autarcie à l'oeuvre dans les écrits d'Aristote et, ce faisant, à nous amener à une meilleure compréhension du lien entre l'éthique et la politique dans la pensée aristotélicienne. Pour ce faire, nous commençons tout d'abord par distinguer deux types d'autarcie, à savoir ce que nous appellerons dans la suite l'autarcie divine et l'autarcie humaine. L'autarcie divine doit être comprise comme le fait de se suffire pleinement à soi-même de la manière la plus rigoureuse qui soit et cette autarcie n'est, à proprement parler, attribuable qu'au divin. L'autarcie humaine, quant à elle, est celle qui est à l'oeuvre dans la définition que donne Aristote de la cité, à savoir qu'elle est un regroupement autarcique de personnes visant à vivre et à bien vivre. Par la suite, nous montrons que la pratique de la philosophie, qui est décrite comme une pratique autarcique en EN, X, est difficilement conciliable avec les activités de la cité et la constitution d'une communauté politique. En effet, comme c'est le besoin qui doit jouer le rôle de ciment de la cité, il est difficile de voir comment la philosophie peut s'insérer dans le cadre étatique de la cité, étant donné qu'elle n'est d'aucune utilité et qu'elle est recherchée pour elle-même. Toutefois, puisqu'Aristote ne présente jamais la cohabitation de la philosophie avec les autres activités de la cité comme problématique, nous tentons de voir comment il est possible de concilier la pratique de la philosophie avec la nécessité pour l'individu de vivre en cité. C'est en examinant la notion de loisir que nous en venons à conclure que la philosophie doit y être reléguée afin de pouvoir être pratiquée. C'est aussi en associant la philosophie au loisir et en étudiant le rôle que celui-ci doit jouer au sein de la cité que nous sommes en mesure de voir se dessiner le lien entre l'éthique et la politique. / This dissertation tries to gain a better understanding of the concept of autarkeia which is present in the writings of Aristotle. Doing this, we are also able to get a clearer idea of the link between ethics and politics in the aristotelian thought. In order to achieve this, we start by distinguishing two types of self-sufficiency : the divine self-sufficiency and the human self-sufficiency. The divine self-sufficiency is to be understood as the fact of being fully self-sufficient in the most rigorous way. Strictly speaking, it is only the divine that can be granted of such a self-sufficiency. On the other hand, the human self-sufficiency is the one effective in the aristotelian definition of the polis, which is the self-sufficient grouping of persons aiming at living and good living. After that, we show that the practice of philosophy, which is described as a self-sufficient activity in NE, X, is hardly possible as an activity of the polis and cannot participate in bringing a polis to life. This is founded in the fact that for Aristotle, it is the needs that keep people together, united in a polis, and considering that, it is difficult to see how philosophy could be part of this, because it is totally useless and searched for itself. However, we try to see how it would be possible to conciliate the practice of philosophy with the necessity for a human to live in a polis, because Aristotle never speaks of it as being problematic. The answer of this so-called problem is to be found in the notion of leisure, by relegating philosophy to this part of a human life in order for it to be practiced. It is also by associating philosophy and leisure that we can draw the link between ethics and politics.