L'énergie dans l'habitat/en : Différence entre versions

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|Step_Title=La puissance solaire
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|Step_Title=Solar power
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|Step_Content=La Terre est soumise à une irradiation solaire très importante, d'une puissance moyenne de 173 Pétawatts (1 PW = 1015 Watts) soit 11 500 fois la puissance consommée par l’humanité.
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|Step_Content=The earth is subjected to significant solar radiation of an average power of 173 petawatts (1 PW = 1,015 W), which is 11,500 times the power consumed by humanity.
  
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Chaque jour elle est un peu plus utilisée via l’installation de panneaux photovoltaïques. Ce type de panneau a un rendement d’environ 15%. Il existe un système technologiquement plus simple non pas pour fournir de l’électricité mais de la chaleur. Les panneaux solaires thermiques ont un rendement supérieur à 60%. Ils produisent donc quatre fois plus d'énergie que les panneaux photovoltaïque pour une même surface. Cette solution est intéressante face aux besoins en chaleur importants dans l'habitat.
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This solar power is being used a little more each day through the installation of photovoltaic panels. This type of panel has an efficiency of around 15%. There is another more technologically simple system that produces not only electricity but heat. These thermal solar panels have an efficiency of greater than 60%. This means that they produce four times the energy of photovoltaic panels over the same surface area. This is an attractive solution in light of the substantial heating needs in the home.
  
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Par temps clair, la puissance du rayonnement solaire à la surface de la Terre est de 1 000 Watts/m². Cependant l’intensité solaire dépend fortement des saisons. En été le soleil est « au plus haut », plus perpendiculaire à la surface terrestre donc une plus grande densité de rayons est captée. A l’inverse, en hiver, il est « au plus bas ».
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On a clear day, the power of solar radiation on the surface of the earth is 1,000 W/m2. Even then, the intensity of solar radiation depends greatly on the season. In the summer, the sun is at its highest, or more perpendicular to the earth’s surface, and thus a greater density of rays is captured. On the other hand, in the winter, the sun is at its lowest. Not only is the angle of the sun affected by seasons, but so is day length. In Paris, the day’s length during the winter solstice is a little over 8 hours, while during the summer solstice, the day’s length is more than 16 hours.
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De plus la durée des journées varie du simple au double, avec, pour Paris, un peu plus de 8h de jour au solstice d’hiver et plus de 16h au solstice d’été.
 
  
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En prenant en compte la puissance solaire et la durée du jour, l’énergie solaire d’un jour d’été est jusqu’à six fois plus importante qu’un jour d’hiver (E = P x t).
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Taking into account the power of the sun’s radiation and day length, the solar energy produced on a summer day is almost 6 times greater than that of a winter day (E = P x t).
  
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Dans l’idée d’utiliser cette énergie pour des applications thermiques ou électriques, il faut penser à orienter son système  en fonction de la période de plus forts besoins, plus vertical l’hiver, plus horizontal l’été. Il reste que l’énergie solaire est toujours présente et qu’un système très productif en été sera toujours un appoint intéressant en hiver.
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In order to harness this energy for thermal and electrical use, it is important to orient the panels at an optimum angle for the season, that is, more vertically in the winter and more horizontally in the summer. The fact remains that solar energy is always present, and a system that is very productive during the summer can always be used as a supplement in the winter.
 
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|Step_Title=Chauffage - la température idéale
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|Step_Title=Heating: the ideal temperature
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|Step_Content=Il est normal que la température d’un logement soit plus élevée l’été que l’hiver et qu’il faille s’habiller en fonction des saisons.  
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|Step_Content=It is natural that the temperature of a home is higher in the summer than the winter, and that we should dress appropriately for the seasons. Furthermore, it is not necessary for the house to be hot in order to live comfortably. The average temperature of a French home is 20 °C. The ADEME (the French Environment and Energy Management Agency) recommends a temperature of 19 °C in living areas and 16 °C in bedrooms. The difference in heating at 20 °C instead of 19 °C produces an energy overconsumption of 7%.
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De plus, pour un bon confort de vie, il n’est pas nécessaire qu’il fasse chaud chez soi. Il fait en moyenne 20°C dans un logement français. L’Ademe recommande une température de 19°C dans les pièces à vivre et de 16°C dans les chambres. La variation d’un chauffage de 19°C à 20°C entraîne une surconsommation d’énergie de 7%.
 
  
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Scientifiquement, cela s’explique en partie par la loi simplifiée de Fourier ou de conduction thermique:
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This can be partly explained scientifically using a simplified version of Fourier’s law, or the law of thermal conduction:  
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                          J_th = -λ GradT = λ x ∆T/e
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J_th = -λ GradT = λ x ∆T/e
  
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Jth : flux thermique (W/m²)
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Jth : heat flow (W/m²)
  
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λ : conductivité thermique (W/m/K)
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λ : thermal conductivity (W/m/K)
  
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∆T : écart de température entre les côtés de la paroi (°C ou K)
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∆T : temperature difference between the two sides of the wall (°C or K)
  
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e : épaisseur de la paroi (m)
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e : thickness of the wall (m)
  
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Selon cette loi, le flux thermique (la perte de chaleur) est proportionnel à la différence de température.
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According to this law, heat flow (that is, heat loss) is proportional to the difference in temperature.
  
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En exemple, s’il fait 12°C à l’extérieur et que l’habitat est chauffé à 18°C :  
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For example, if it is 12 °C outside and a house is heated at 18 °C:
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                          J_th1 = λ x (18-12) / e = λ x 6 / e
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                          J_th1 = λ x (18-12) / e = λ x 6 / e
  
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S’il fait toujours 12°C à l’extérieur mais que l’habitat est chauffé à 24°C :
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If it remains 12 °C outside but a house is heated at 24 °C:
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                          J_th2 = λ x (24-12) / e = λ x 12 / e = 2×J_th1
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                          J_th2 = λ x (24-12) / e = λ x 12 / e = 2×J_th1
 
  
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Quel que soit l’isolant utilisé et son épaisseur, s’il fait 12°C à l’extérieur les déperditions thermiques seront 2 fois plus importantes à 24°C qu’à 18°C.
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Regardless of the insulation used and its thickness, if it is 12 °C outside, then the heat loss will be two times greater at 24 °C than at 18 °C.
 
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|Step_Title=Chauffage - l'isolation
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|Step_Title=Heating: insulation
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|Step_Content=Le chauffage représente en moyenne sur l’année les deux tiers de la consommation énergétique des foyers avec environ 11 000 kWh. N’étant utilisé que pendant la saison froide, environ six mois de l’année, il est un véritable « gouffre d’énergie » avec 60 kWh journaliers lissés sur cette période.
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|Step_Content=On average over the year, heating represents two-thirds of household energy consumption at around 11,000 kWh. Considering that heating is only used during the cold season, or about six months of the year, it is a veritable “energy pit,” with about 60 kWh used daily when spread over this period.
  
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Une très bonne isolation permet de réduire de 80% les besoins en chaleur. Il est possible d’isoler son habitat de plusieurs manières avec des efficacités et des coûts économiques très différents.
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A good insulation can reduce heating needs by 80%. There are several ways to insulate a house that vary widely in efficacy and cost.
  
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En exemple, l’isolation par l’extérieur est intéressante : elle permet de garder le logement en dehors du froid environnant et de conserver l’énergie solaire dans les matériaux lourds de la construction, s’ils ne sont pas couverts d’un isolant thermique. Mais cette méthode d’isolation est onéreuse et demande d’importants travaux. De plus ce n’est pas par les murs que les déperditions thermiques sont les plus importantes.
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For example, exterior insulation protects a house from environmental cold and conserves solar energy within heavy construction materials if they are not covered in a thermal insulation. However, this method of insulation is expensive and requires a lot of work to install. And in any case, it isn’t via the walls that the most significant heat loss occurs.
  
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En premier lieu, il faut faire attention à la bonne étanchéité à l’air. Chauffer un courant d’air, même bien isolé, est inutile. La circulation d’air provient majoritairement des espaces entre les fenêtres, portes et leurs cadres. Un joint en mousse limitera fortement le vent ambiant.
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It is important to pay attention to the airtightness of a house, as it is useless to heat air currents even if the house is well insulated. Air currents come primarily from spaces between windows and doors and their frames. A foam seal will significantly limit these currents.
  
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Les fenêtres sont responsables de 10 à 15% des déperditions thermiques, Fermer ses volets ou tirer un rideau lourd évite un investissement dans une nouvelle épaisseur de vitrage.
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Windows are responsible for 10 to 15% of heat loss. Closing the shutters or using heavy curtains will help you to avoid the need to invest in thicker windows.
  
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Il faut également faire attention aux ponts thermiques : ce sont des zones de faiblesse dans l'enveloppe d'un bâtiment. Le froid extérieur est alors plus rapidement transmis à l’intérieur du logement. Les ponts thermiques les plus importants se situent aux jonctions entre la toiture et les murs et entre les murs et les menuiseries des fenêtres. Ce sont les premières régions à isoler.
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It is also important to pay attention to heat bridges, which are weak zones in the building envelope. In these areas, exterior cold is transmitted more rapidly into the interior of a home. The most significant heat bridges are found at junctions between the roof and the walls and between walls and window woodwork. These are the primary areas that should be insulated.
  
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Dans l’étape précédente est détaillée la loi de Fourier sur la conduction thermique. La conduction thermique est la quantité de chaleur qui passe d’un milieu à un autre en fonction du matériau les séparant et de son épaisseur. Cette conduction dépend du facteur de conductivité thermique (λ) propre à chaque matériau. Plus λ est faible, plus le matériau est isolant. Selon la norme française RT2012, un matériau est considéré comme isolant si sa conductivité thermique est inférieure à 0,065 W/m/K. Voici quelques exemples de matériaux communs pouvant être utilisés dans la construction :
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Fourier’s law on thermal conduction is detailed in the previous step. Thermal conduction is the amount of heat that passes from one area to another depending on the type and thickness of the material separating the areas. This conduction depends on the thermal conductivity (λ) of a particular material. The weaker λ is, the more insulating the material is. According to the French regulation RT2012, a material is considered insulating if its thermal conductivity is less than 0.065 W/m/K. Here are some examples of materials that are used in construction:
  
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Matériaux λ (W/m/K) à 20°C
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Material λ (W/m/K) at 20 °C
  
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Brique (terre cuite) 0,84
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Brick: 0.84
  
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Carton                 0,11
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Cardboard: 0.11
  
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Laine de verre         0,04
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Glass wool: 0.04
  
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Paille                 0,04
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Straw: 0.04
 
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|Step_Title=Chauffage - chauffer autrement
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|Step_Title=Heating: other options
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|Step_Content=Le logement n’est plus un courant d’air. Les principaux ponts thermiques de l’enveloppe sont isolés. La température ciblée est réduite de quelques degrés. Les besoins en apports caloriques sont donc fortement réduits. Il devient intéressant de s’orienter vers une nouvelle source de chaleur, au moins auxiliaire, pour réduire sa consommation directe (gaz, fioul) ou indirecte (électricité) d’énergies fossiles.
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|Step_Content=By this step, much has been improved: air currents have been blocked, the main heat bridges in the building envelope have been insulated, and the target temperature has been decreased by some degrees. Heating needs have thus been significantly reduced. Now, it becomes important to find a new source of heat, or at least an auxiliary source, to reduce direct (i.e., gas, oil) or indirect (electricity) consumption of fossil fuels.
  
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En fonction du type d’habitat et de la région, il peut être intéressant de chauffer à la biomasse (bois, pellet, granulé de bois) dans un poêle à bois. Les poêles de masse (tutoriel disponible en décembre) ont un rendement supérieur à 80% et sont donc très économiques en combustibles.
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Depending on the type of house and its location, it could be feasible to heat by burning biomass (i.e., wood, pellets, granulated wood) in a woodstove. Biomass stoves (a tutorial on this will be available in December) have an efficiency of greater than 80% and so are very economical in terms of fuel.
  
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Attention, chauffer à la biomasse n’est pas synonyme d’écologie. En effet, les cheminées à foyer ouvert sont un moyen de chauffage des plus médiocres. L'air réchauffé est  aspiré par la cheminée. La cheminée ne chauffe dès lors que par rayonnement. Plus le foyer sera chaud, plus le tirage sera important, plus l’air intérieur sera évacué vers l’extérieur. Un foyer ordinaire peut avoir un tirage de 800 à 1 000 mètres cubes d'air par heure. Le  rôle principal des cheminées est donc réduit à de la ventilation. Caricaturalement, avec une cheminée, plus on chauffe, plus il fait froid (en dehors de la zone de rayonnement).
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Be aware, however, that heating by biomass is not synonymous with environmentalism. In fact, chimneys with an open hearth are one of the most mediocre forms of heating. Reheated air is sucked up the chimney, so the chimney only heats by radiation. The hotter the hearth gets, the greater the draw, and the more air is sucked from inside to the outside. An ordinary hearth can have a draw of 800 to 1,000 m3 of air per hour. The principal use of a chimney is thus reduced to ventilation. Ironically, with a chimney, the more it is heated, the colder the air gets (outside the zone of radiation).
  
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De plus, la combustion dans un foyer ouvert est très incomplète. Les fumées qui s’échappent d’une cheminée sont des hydrocarbures non consommés, donc un manque à gagner et une pollution supplémentaire.
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Furthermore, combustion in an open hearth is very incomplete. The fumes that escape through the chimney are unused hydrocarbons, resulting in a shortfall and further pollution.
  
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En résumé, moins il y a de fumées en sortie du poêle, meilleur est le rendement de la combustion. Plus la température des fumées est faible, plus la chaleur est donnée au logement.
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To summarize, the less fumes there are escaping from a stove, the better the efficiency of the combustion. The lower the temperature of the fumes, the more heat is available for the house.
  
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Pour limiter le volume de combustible (biomasse, gaz, fioul) pour se chauffer, il est également possible d’utiliser le rayonnement solaire et sa transformation en calories. En hiver, les journées sont plus courtes et le rayonnement solaire est moins puissant qu’en été mais l’énergie disponible reste cependant importante.
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In order to limit the volume of fuel (biomass, gas, oil) used for heating, it is possible to use solar radiation and its transformation into calories. In winter, the days are shorter and solar radiation is less powerful than in summer, but the available energy is still considerable.
  
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En prenant en compte la météorologie, d’octobre à mars, période d’utilisation du chauffage, le soleil fournit plus de 3 kWh/m² par jour dans le sud de la France, plus de 2 kW.h/m² dans le nord. En prenant un rendement de 60%, les énergies captées par un panneau solaire thermique seraient respectivement de 2 et 1,3 kW.h/m²
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Taking into account the weather, from October to March (the period when heating is used) the sun provides more than 3 kWh/m2 per day in the south of France and more than 2 kWh/m2 in the north. Based on an efficiency of 60%, the energy captured by thermal solar panels would be 2 and 1.3 kWh/m2, respectively.
 
|Step_Picture_00=L_nergie_dans_l_habitat_Chauffage_vs_puissance_solaire.png
 
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|Step_Title=Chauffe-eau
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|Step_Title=Water heaters
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|Step_Content=Le chauffage de l’eau chaude sanitaire représente plus de 10% de l’énergie totale consommée à l’année dans un logement. La consommation moyenne d’un foyer est d’environ 1 700 kW.h par an soit un peu moins de 5 kW.h par jour.
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|Step_Content=Hot water heating represents more than 10% of the total energy consumed annually in a home. The average household consumption is 1,700 kWh per year, or a little less than 5 kWh per day.
  
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Comme pour le chauffage du logement, la première action à réaliser est de bien isoler sa chaudière, son chauffe-eau et les tuyaux qui en sortent. Un chauffe-eau neuf de 200 litres a des pertes statiques de plus d’ 1 kW.h par jour. Les pertes statiques sont l’énergie liée à la diminution de la température de l’eau sans qu’elle soit consommée. 20% de la consommation quotidienne est perdue. Sur-isoler le ballon permet d’économiser une part conséquente de l’énergie. Quand on touche un chauffe-eau, il doit être froid, sinon c’est un radiateur, il perd de l’énergie par rapport à sa fonction première.
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Just as with home heating, the first step to take is to well insulate the water heater, the hot water tank, and the pipes coming from it. A new hot water tank of 200 liters has a standing loss of more than 1 kWh per day. Standing loss is the energy related to the decrease in the water's temperature before it is used. So, 20% of the energy consumed daily by this new hot water tank is lost. Insulating the hot water tank will preserve some of this energy. A hot water tank should be cool to the touch; if not, it is simply a radiator and is losing energy in relation to its primary function.
  
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Précédemment étaient étudiés les intérêts et limites du chauffage solaire thermique. Les besoins en chauffage sont inversement proportionnels à l’énergie fournie par le soleil. Pour l’eau, la situation est bien différente : les besoins sont similaires toute l’année et 13 fois moins forts que le chauffage en plein hiver.
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In previous steps we looked at the benefits and limits of thermal solar heating. Home heating needs are inversely proportional to the energy provided by the sun. For water heating, the situation is different: needs are similar throughout the year and are 13 times less than what is needed for home heating in the middle of winter.
  
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Le fonctionnement des chauffe-eau solaires est simple : un fluide caloporteur (qui transporte la chaleur) passe dans des tubes isolés exposés idéalement au soleil. Avec le rayonnement, le fluide chauffe ; quand la température du fluide est supérieure à celle du ballon d’eau chaude, un thermostat ouvre la vanne de circulation. Le fluide caloporteur transfère ses calories à l’eau sanitaire.
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The operation of a solar water heater is simple: a heat-carrying fluid passes through insulated tubes that are exposed to the sun. The sun’s radiation heats the fluid, and when the temperature of the fluid exceeds that of the hot water tank, a thermostat opens a circulation valve. The fluid then transfers its calories to the water in the tank.
  
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L'eau du ballon chauffe dans la journée, avec le soleil. L’eau a une bonne inertie thermique, elle gardera sa température pendant la nuit si le ballon est isolé.
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The water in a hot water tank is heated during the day by the sun. Water has a good thermal inertia, so it will maintain its temperature at night if the tank is insulated.
  
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Les systèmes solaires thermiques ont un rendement en général supérieur à 60%, c’est-à-dire que si le soleil rayonne 1 000 W/m², un chauffe-eau solaire de 1 m² générera au moins 600 W de chaleur.
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Thermal solar systems generally have an efficiency greater than 60%, meaning that if the sun radiates 1,000 W/m2, a solar water heater of 1 m2 will generate at least 600 W of heat.
  
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Avec l’ensoleillement moyen en France, 4 m² de panneaux permettent de couvrir les besoins quotidiens toute l’année ; 3 m² de panneaux permettent de couvrir les besoins pendant 90% de l’année, décembre excepté; 2 m² couvrent les besoins en eau chaude pendant la moitié la plus chaude de l’année.
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Given the average amount of sunshine in France, 4 m2 of panels is enough to cover daily hot water needs year-round. 3 m2 of panels will cover daily needs 90% of the year except for December, and 2 m2 will cover needs during the hottest half of the year.
  
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Quelle que soit la saison, il est possible d’avoir plusieurs jours consécutifs sans soleil. L’eau restera froide. Les systèmes de chauffe-eau solaires sont en général couplés avec un système électrique qui prend le relai pendant les longues périodes nuageuses.
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In any season, it is possible to have multiple consecutive days without sunshine, in which the water will remain cold. Solar hot water systems are generally paired with electric systems that make up for the deficit during these long cloudy periods.
  
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Un système de chauffe-eau solaire low-tech sera documenté par le Low-tech Lab en 2018.
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A low-tech solar hot water system will be documented by the Low-tech Lab in 2018.
 
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|Step_Title=Cuisson
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|Step_Title=Cooking
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|Step_Content=La cuisson représente environ 6% de l’énergie consommée. C’est un peu moins de 1 000 kWh sur l’année soit environ 2,5 kWh par jour.
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|Step_Content=Cooking represents about 6% of energy consumed. This is a little less than 1,000 kWh annually or about 2.5 kWh per day.
  
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Globalement, d’un point de vue énergétique, la cuisson au gaz est la plus intéressante. L’efficacité d’une gazinière est de 60%, contre 90% pour des plaques à induction. Mais, comme vu en introduction, l’électricité du réseau est produite avec de la chaleur. Si on prend en compte les 70% de pertes de la centrale et du réseau, le rendement énergétique de l’induction chute à 27%.
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Overall, from an energy consumption point of view, cooking with gas is the most attractive option. The efficiency of a gas cooker is 60% compared to 90% for induction cookers. However, as seen in the introduction, mains electricity is produced using heat. Taking into account the 70% loss of the power plant and the grid, the energy efficiency of induction cookers falls to 27%.
  
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Le gaz naturel distribué dans le réseau est du méthane (CH4). Il est possible d’en produire à petite échelle à partir de déchets organiques via un compostage anaérobique. Les systèmes domestiques permettant la production de méthane sont appelés méthaniseurs ou biodigesteurs.
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Mains gas is a natural gas called methane (CH4). It is possible to produce methane on a small scale from organic waste via anaerobic composting. Domestic systems that produce methane are called biodigesters.
  
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Pour réduire la consommation propre à la cuisson, deux solutions simples peuvent être mises en place : les jupes isolantes et la marmite norvégienne. Une gazinière perd une bonne partie de son énergie en chauffant l’air autour de la casserole. Une jupe permet de concentrer la chaleur du feu sur la zone à chauffer. La jupe isole également les champs de la casserole, cela permet de limiter les pertes de chaleur pendant et après la cuisson. C’est également le principe de la marmite norvégienne, particulièrement utilisée pour les cuissons longues. Une fois le plat monté à température, on le retire du feu pour le placer dans une enceinte très bien isolée. La chaleur va descendre très doucement, possiblement pendant des heures, permettant à la cuisson de continuer sans consommer d’énergie additionnelle. Pour ces deux solutions, des tutoriels seront bientôt disponibles.
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To reduce energy consumption in cooking, two simple solutions can be put in place: pot skirts and Norwegian pots. A gas cooker loses a good portion of its energy in heating the air around the pot. A skirt will concentrate the heat of the fire on the spot that needs to be heated. The skirt also insulates the pot, which limits heat loss during and after cooking. This is the same principle with the Norwegian pot, which is used particularly for longer cooks. Once the food has reached the needed temperature, it can be taken off the heat and placed in a well-insulated enclosure. The heat will decrease very gently, possibly over hours, allowing cooking to continue without consuming additional energy. For these two solutions, tutorials will soon be available.
 
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|Step_Title=Energie spécifique
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|Step_Title=Specific energy
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|Step_Content=L’énergie spécifique est l’énergie dédiée à la lumière, l’équipement électroménager, la bureautique et la hi-fi. C’est la seule énergie pour laquelle le besoin est de l'électricité. Toutes les autres énergies de l'habitat sont des besoins de chaleur. Elle représente aujourd’hui 16,6% de l’énergie consommée. C’est un peu moins de 2 700 kW.h sur l’année soit environ 7 kW.h par jour.
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|Step_Content=Specific energy is energy use dedicated to lighting, household appliances, office equipment, and hi-fi. It is the only category of energy use in which the need is for electricity; all other energy used in the home is for heating needs. Currently, this category represents 16.6% of energy consumed. This is a little less than 2,700 kWh per year or about 7 kWh per day.
  
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Avec l’arrivée massive des lampes à économie d’énergie et des LED, la consommation consacrée à la lumière a fortement diminué. Cependant, la consommation d’énergie spécifique a doublé depuis 1990. En cause, le nombre croissant d’appareils électriques et électroniques, comme les téléphones et ordinateurs qui habitent le quotidien.
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With the mass arrival of energy efficient bulbs and LEDs, energy consumption related to lighting has greatly decreased. And yet, the consumption of specific energy has doubled since 1990. This is due to the growing number of electric devices such as telephones and computers that are now part of daily life.
  
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Pour limiter sa consommation spécifique, il faut faire attention à ne pas multiplier les appareils. De plus, les appareils non utilisés sont souvent en veille, avec une consommation légèrement inférieure à 1 W. Mais une veille d’un Watt sur l’année correspond à l’énergie nécessaire pour cuisiner pendant 4 jours. L’énergie consommée par plusieurs appareils en veille peut être conséquente.
+
To limit specific energy consumption, it is important to not increase the number of devices in the home. Furthermore, devices that are not currently in use are often in sleep mode, which consumes slightly less than 1 W. This 1 W per year used by sleep mode is equal to the amount of energy needed for 4 days of cooking. The energy consumed by multiple devices in sleep mode can be significant.
  
−
Pour finir, bien qu’invisible individuellement mais avec un très fort impact à l’échelle nationale : la consommation électrique en fin de journée, où une grande partie des besoins énergétiques sont concentrés sur quelques heures. Chacun rentre chez soi et allume tous ses appareils (téléviseurs, ordinateurs, machine à laver, cuisinière, etc). La demande est telle que la consommation nationale connaît un véritable pic sur cette période. L’énergie n’étant pas ou peu stockable, les centrales doivent fournir cette énergie en direct. Le parc électrique français est dimensionné par cette demande en énergie, en début de soirée.
+
And finally, there is a phenomenon that may be invisible at an individual level but has a large impact on a national scale: the electric consumption in the evening when a large part of electricity needs are concentrated within a few hours. At that time, everyone returns home and turns on all of their devices (televisions, computers, washing machines, ovens, etc.). The demand is such that the national consumption sees a veritable peak during this period. Since little to no energy can be stored, power plants must provide this energy in real time. French power stations are sized based on this energy demand at the start of the evening.
  
−
Si la consommation électrique était lissée sur la journée, plusieurs centrales électriques pourraient être fermées. Pour répartir ce besoin, il est possible de programmer certains appareils pour la nuit ou, encore mieux, en journée, profitant du solaire photovoltaïque de plus en plus présent.
+
If electricity consumption were spread out over the day, many electric power plants could be closed. In answer to this need, it is possible to program certain devices to run during the night, or even better, during the day to take advantage of solar photovoltaic panels that are becoming increasingly present.
 
|Step_Picture_00=L_nergie_dans_l_habitat_E_Sp_cifique.png
 
|Step_Picture_00=L_nergie_dans_l_habitat_E_Sp_cifique.png
 
}}
 
}}
 
{{Tuto Step
 
{{Tuto Step
 
|Step_Title=Conclusion
 
|Step_Title=Conclusion
−
|Step_Content=La consommation énergétique dans le logement français est importante. La première étape à réaliser dans la transition énergétique individuelle n’est pas le changement de source d'énergie et/ou d’échelle. L’installation de panneaux photovoltaïques ou d’éoliennes n’est pas intéressante économiquement et écologiquement parlant s’il n’y a pas eu une importante réduction de la consommation énergétique avant.
+
|Step_Content=Energy consumption in the French household is significant. The first step in individual energy transition is not to change the source of energy and/or the scale of production. The installation of photovoltaic panels or windmills is not economically and ecologically impactful if there is not a significant reduction in energy consumption first.
  
−
Mais réduire sa consommation ce n’est pas se priver ou même perdre du confort. C’est rendre son habitat plus efficace. L'efficacité, c’est avant tout limiter ses pertes.
+
However, reducing your consumption does not mean depriving yourself of comfort; it means making your home more efficient. Above all else, efficiency is limiting losses. Since more than 70% of energy is consumed in heating, losses can be limited by well insulating the home.
−
Plus de 70% de l'énergie consommée étant du chauffage, limiter ses pertes c’est bien isoler son logement.
 
  
−
Une fois les pertes réduites il est possibles de s’orienter vers des solutions moins puissantes. Dans ces conditions les alternatives intéressantes sont nombreuses, en low-tech, ou conventionnelles :
+
Once these losses are reduced, then it is possible to look for solutions that use less power. The alternatives are numerous and attractive, both low-tech and conventional:
  
−
* poêle à bois
+
Woodstove
−
* chauffage solaire
+
Solar heating
−
* chauffe-eau solaire
+
Solar water heater
−
* architecture bioclimatique
+
Bioclimatic architecture
−
* éolienne
+
Wind power
−
* panneaux solaires
+
Solar panels
−
* biogaz
+
Biogas
−
* marmite norvégienne
+
Norwegian pot
−
* jupe isolante
+
Pot skirt
 
}}
 
}}
 
{{Notes
 
{{Notes
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|Notes=*https://www.connaissancedesenergies.org/fiche-pedagogique/mix-energetique-de-la-france
+
|Notes=https://www.connaissancedesenergies.org/fiche-pedagogique/mix-energetique-de-la-france
−
*http://www.statistiques.developpement-durable.gouv.fr/energie-climat/r/consommations-secteur-tous-secteurs.html?tx_ttnews%5Btt_news%5D=21060&cHash=4168b27f68d9955400f2c25b0419095f
+
http://www.statistiques.developpement-durable.gouv.fr/energie-climat/r/consommations-secteur-tous-secteurs.html?tx_ttnews%5Btt_news%5D=21060&cHash=4168b27f68d9955400f2c25b0419095f
−
*https://www.ecologique-solidaire.gouv.fr/collection-datalab
+
https://www.ecologique-solidaire.gouv.fr/collection-datalab
−
*http://ines.solaire.free.fr/gisesol_1.php#
+
http://ines.solaire.free.fr/gisesol_1.php#
−
*https://fr.wikipedia.org/wiki/Conductivit%C3%A9_thermique
+
https://fr.wikipedia.org/wiki/Conductivit%C3%A9_thermique
−
*https://www.connaissancedesenergies.org/fiche-pedagogique/mix-energetique-de-la-france
+
https://www.connaissancedesenergies.org/fiche-pedagogique/mix-energetique-de-la-france
−
*https://www.e-rt2012.fr/explications/conception/explication-architecture-bioclimatique/
+
https://www.e-rt2012.fr/explications/conception/explication-architecture-bioclimatique/
−
*http://www.solaire1300.ch/f/technologie-solaire/rayonnement-solaire-delivre-par-heure.asp
+
http://www.solaire1300.ch/f/technologie-solaire/rayonnement-solaire-delivre-par-heure.asp
−
*http://www.ademe.fr/particuliers-eco-citoyens/habitation/renover/isolation/isolation-toit-murs-planchers
+
http://www.ademe.fr/particuliers-eco-citoyens/habitation/renover/isolation/isolation-toit-murs-planchers
 +
 
 +
English translation : Brianna Lale.
 
}}
 
}}
 
{{PageLang
 
{{PageLang

Version actuelle datée du 8 novembre 2022 à 10:35

Tutorial de avatarLow-tech Lab | Catégories : Habitat, Énergie

avatarLow-tech Lab

L nergie dans l habitat Main.png
https://wiki.lowtechlab.org/wiki/L%27%C3%A9nergie_dans_l%27habitat/en
Dernière modification le 08/11/2022


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How to have energy-efficient homes

How to have energy-efficient homes

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English • ‎français

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Introduction

Today, whether for environmental, economic, or political reasons, many people want to be self-sufficient in energy production. However, before thinking about more ecological methods of energy production, it is important to first lower your own energy consumption. And to do that, you will need to know how much energy you are consuming.

Video d'introduction

Étape 1 - Energy consumption in France

In France, buildings account for 45% of the total energy consumed, followed by transportation (33%), industry (19%), and agriculture (3%). Two-thirds of the energy consumption in this category comes from housing and one-third from service sector buildings.

Within the home, in 2013, 67% of consumed energy went toward heating the home, 10.4% toward heating water, and 6% toward cooking. The remaining 16.6% was used for lighting, household appliances, office equipment, and hi-fi, all of which is grouped under the term “specific energy”. The 16,000 kWh consumed by each household costs just over €1,700 per year.

In France, residential heating accounts for a larger portion of the total energy consumed (20.1%) than does industry (19%).

L nergie dans l habitat Conso nerg tique france.png
L nergie dans l habitat Conso nerg tique habitat.png



Étape 2 - Glossary

In this tutorial, each category of home energy consumption is explained in detail. The topics of power and energy, which are relatively abstract, are addressed throughout the text.

Here is a brief explanation of these concepts:

Power (P) is measured in watts (W) or kilowatts (kW) Energy (E) is measured in watt-hours (Wh) or kilowatt-hours (kWh)

Power and energy are linked by time: power is the amount of energy per unit time. Power is therefore a rate of energy transfer. P x t = E

Here is an example to illustrate these two closely related concepts:

A cyclist pedaling slowly generates a power of 50 W. If they cycle for an hour, they produce an energy of 50 W x 1 hr = 50 kWh. If they pedal at this same slow speed for two hours, they produce an energy of 50 W x 1 hr = 100 kWh.

The 16,000 kWh produced annually per household thus corresponds to 320,000 hours, or 36 years, of non-stop slow cycling.

If we had to pedal to produce our own energy, how much time would it take? The game “Revolt” shows you the energy consumption of your everyday appliances in hours of cycling: http://la-revolt.org/

Étape 3 - Electricity and heat in the home

More than three-fourths of energy consumed in the home goes toward heat production (home heating, hot water, and cooking). Half of electricity used in the household (50.4%) is for heat production. 81% of electricity is produced by nuclear power plants or fossil energy (gas, carbon, and oil).

The efficiency of nuclear power plants is around 30%. Here is a closer look at the electricity production and transport process: Fluid is heated to create pressure, and this pressure turns a turbine, which in turn feeds a generator to produce electricity. The resulting electricity is transported to homes, and there it is turned into heat. In terms of energy use, with three transformations and transport involved in the process, heating by electricity is not in our best interest.

Étape 4 - Solar power

The earth is subjected to significant solar radiation of an average power of 173 petawatts (1 PW = 1,015 W), which is 11,500 times the power consumed by humanity.

This solar power is being used a little more each day through the installation of photovoltaic panels. This type of panel has an efficiency of around 15%. There is another more technologically simple system that produces not only electricity but heat. These thermal solar panels have an efficiency of greater than 60%. This means that they produce four times the energy of photovoltaic panels over the same surface area. This is an attractive solution in light of the substantial heating needs in the home.

On a clear day, the power of solar radiation on the surface of the earth is 1,000 W/m2. Even then, the intensity of solar radiation depends greatly on the season. In the summer, the sun is at its highest, or more perpendicular to the earth’s surface, and thus a greater density of rays is captured. On the other hand, in the winter, the sun is at its lowest. Not only is the angle of the sun affected by seasons, but so is day length. In Paris, the day’s length during the winter solstice is a little over 8 hours, while during the summer solstice, the day’s length is more than 16 hours.

Taking into account the power of the sun’s radiation and day length, the solar energy produced on a summer day is almost 6 times greater than that of a winter day (E = P x t).

In order to harness this energy for thermal and electrical use, it is important to orient the panels at an optimum angle for the season, that is, more vertically in the winter and more horizontally in the summer. The fact remains that solar energy is always present, and a system that is very productive during the summer can always be used as a supplement in the winter.

L nergie dans l habitat Soleil.jpg




Étape 5 - Heating: the ideal temperature

It is natural that the temperature of a home is higher in the summer than the winter, and that we should dress appropriately for the seasons. Furthermore, it is not necessary for the house to be hot in order to live comfortably. The average temperature of a French home is 20 °C. The ADEME (the French Environment and Energy Management Agency) recommends a temperature of 19 °C in living areas and 16 °C in bedrooms. The difference in heating at 20 °C instead of 19 °C produces an energy overconsumption of 7%.

This can be partly explained scientifically using a simplified version of Fourier’s law, or the law of thermal conduction: J_th = -λ GradT = λ x ∆T/e

Jth : heat flow (W/m²)

λ : thermal conductivity (W/m/K)

∆T : temperature difference between the two sides of the wall (°C or K)

e : thickness of the wall (m)

According to this law, heat flow (that is, heat loss) is proportional to the difference in temperature.

For example, if it is 12 °C outside and a house is heated at 18 °C: 

                         J_th1 = λ x (18-12) / e = λ x 6 / e

If it remains 12 °C outside but a house is heated at 24 °C: 

                         J_th2 = λ x (24-12) / e = λ x 12 / e = 2×J_th1

Regardless of the insulation used and its thickness, if it is 12 °C outside, then the heat loss will be two times greater at 24 °C than at 18 °C.

Étape 6 - Heating: insulation

On average over the year, heating represents two-thirds of household energy consumption at around 11,000 kWh. Considering that heating is only used during the cold season, or about six months of the year, it is a veritable “energy pit,” with about 60 kWh used daily when spread over this period.

A good insulation can reduce heating needs by 80%. There are several ways to insulate a house that vary widely in efficacy and cost.

For example, exterior insulation protects a house from environmental cold and conserves solar energy within heavy construction materials if they are not covered in a thermal insulation. However, this method of insulation is expensive and requires a lot of work to install. And in any case, it isn’t via the walls that the most significant heat loss occurs.

It is important to pay attention to the airtightness of a house, as it is useless to heat air currents even if the house is well insulated. Air currents come primarily from spaces between windows and doors and their frames. A foam seal will significantly limit these currents.

Windows are responsible for 10 to 15% of heat loss. Closing the shutters or using heavy curtains will help you to avoid the need to invest in thicker windows.

It is also important to pay attention to heat bridges, which are weak zones in the building envelope. In these areas, exterior cold is transmitted more rapidly into the interior of a home. The most significant heat bridges are found at junctions between the roof and the walls and between walls and window woodwork. These are the primary areas that should be insulated.

Fourier’s law on thermal conduction is detailed in the previous step. Thermal conduction is the amount of heat that passes from one area to another depending on the type and thickness of the material separating the areas. This conduction depends on the thermal conductivity (λ) of a particular material. The weaker λ is, the more insulating the material is. According to the French regulation RT2012, a material is considered insulating if its thermal conductivity is less than 0.065 W/m/K. Here are some examples of materials that are used in construction:

Material λ (W/m/K) at 20 °C

Brick: 0.84

Cardboard: 0.11

Glass wool: 0.04

Straw: 0.04

Étape 7 - Heating: other options

By this step, much has been improved: air currents have been blocked, the main heat bridges in the building envelope have been insulated, and the target temperature has been decreased by some degrees. Heating needs have thus been significantly reduced. Now, it becomes important to find a new source of heat, or at least an auxiliary source, to reduce direct (i.e., gas, oil) or indirect (electricity) consumption of fossil fuels.

Depending on the type of house and its location, it could be feasible to heat by burning biomass (i.e., wood, pellets, granulated wood) in a woodstove. Biomass stoves (a tutorial on this will be available in December) have an efficiency of greater than 80% and so are very economical in terms of fuel.

Be aware, however, that heating by biomass is not synonymous with environmentalism. In fact, chimneys with an open hearth are one of the most mediocre forms of heating. Reheated air is sucked up the chimney, so the chimney only heats by radiation. The hotter the hearth gets, the greater the draw, and the more air is sucked from inside to the outside. An ordinary hearth can have a draw of 800 to 1,000 m3 of air per hour. The principal use of a chimney is thus reduced to ventilation. Ironically, with a chimney, the more it is heated, the colder the air gets (outside the zone of radiation).

Furthermore, combustion in an open hearth is very incomplete. The fumes that escape through the chimney are unused hydrocarbons, resulting in a shortfall and further pollution.

To summarize, the less fumes there are escaping from a stove, the better the efficiency of the combustion. The lower the temperature of the fumes, the more heat is available for the house.

In order to limit the volume of fuel (biomass, gas, oil) used for heating, it is possible to use solar radiation and its transformation into calories. In winter, the days are shorter and solar radiation is less powerful than in summer, but the available energy is still considerable.

Taking into account the weather, from October to March (the period when heating is used) the sun provides more than 3 kWh/m2 per day in the south of France and more than 2 kWh/m2 in the north. Based on an efficiency of 60%, the energy captured by thermal solar panels would be 2 and 1.3 kWh/m2, respectively.

L nergie dans l habitat Chauffage vs puissance solaire.png




Étape 8 - Water heaters

Hot water heating represents more than 10% of the total energy consumed annually in a home. The average household consumption is 1,700 kWh per year, or a little less than 5 kWh per day.

Just as with home heating, the first step to take is to well insulate the water heater, the hot water tank, and the pipes coming from it. A new hot water tank of 200 liters has a standing loss of more than 1 kWh per day. Standing loss is the energy related to the decrease in the water's temperature before it is used. So, 20% of the energy consumed daily by this new hot water tank is lost. Insulating the hot water tank will preserve some of this energy. A hot water tank should be cool to the touch; if not, it is simply a radiator and is losing energy in relation to its primary function.

In previous steps we looked at the benefits and limits of thermal solar heating. Home heating needs are inversely proportional to the energy provided by the sun. For water heating, the situation is different: needs are similar throughout the year and are 13 times less than what is needed for home heating in the middle of winter.

The operation of a solar water heater is simple: a heat-carrying fluid passes through insulated tubes that are exposed to the sun. The sun’s radiation heats the fluid, and when the temperature of the fluid exceeds that of the hot water tank, a thermostat opens a circulation valve. The fluid then transfers its calories to the water in the tank.

The water in a hot water tank is heated during the day by the sun. Water has a good thermal inertia, so it will maintain its temperature at night if the tank is insulated.

Thermal solar systems generally have an efficiency greater than 60%, meaning that if the sun radiates 1,000 W/m2, a solar water heater of 1 m2 will generate at least 600 W of heat.

Given the average amount of sunshine in France, 4 m2 of panels is enough to cover daily hot water needs year-round. 3 m2 of panels will cover daily needs 90% of the year except for December, and 2 m2 will cover needs during the hottest half of the year.

In any season, it is possible to have multiple consecutive days without sunshine, in which the water will remain cold. Solar hot water systems are generally paired with electric systems that make up for the deficit during these long cloudy periods.

A low-tech solar hot water system will be documented by the Low-tech Lab in 2018.

L nergie dans l habitat chauffe-eau.png




Étape 9 - Cooking

Cooking represents about 6% of energy consumed. This is a little less than 1,000 kWh annually or about 2.5 kWh per day.

Overall, from an energy consumption point of view, cooking with gas is the most attractive option. The efficiency of a gas cooker is 60% compared to 90% for induction cookers. However, as seen in the introduction, mains electricity is produced using heat. Taking into account the 70% loss of the power plant and the grid, the energy efficiency of induction cookers falls to 27%.

Mains gas is a natural gas called methane (CH4). It is possible to produce methane on a small scale from organic waste via anaerobic composting. Domestic systems that produce methane are called biodigesters.

To reduce energy consumption in cooking, two simple solutions can be put in place: pot skirts and Norwegian pots. A gas cooker loses a good portion of its energy in heating the air around the pot. A skirt will concentrate the heat of the fire on the spot that needs to be heated. The skirt also insulates the pot, which limits heat loss during and after cooking. This is the same principle with the Norwegian pot, which is used particularly for longer cooks. Once the food has reached the needed temperature, it can be taken off the heat and placed in a well-insulated enclosure. The heat will decrease very gently, possibly over hours, allowing cooking to continue without consuming additional energy. For these two solutions, tutorials will soon be available.

L nergie dans l habitat cuisson.png




Étape 10 - Specific energy

Specific energy is energy use dedicated to lighting, household appliances, office equipment, and hi-fi. It is the only category of energy use in which the need is for electricity; all other energy used in the home is for heating needs. Currently, this category represents 16.6% of energy consumed. This is a little less than 2,700 kWh per year or about 7 kWh per day.

With the mass arrival of energy efficient bulbs and LEDs, energy consumption related to lighting has greatly decreased. And yet, the consumption of specific energy has doubled since 1990. This is due to the growing number of electric devices such as telephones and computers that are now part of daily life.

To limit specific energy consumption, it is important to not increase the number of devices in the home. Furthermore, devices that are not currently in use are often in sleep mode, which consumes slightly less than 1 W. This 1 W per year used by sleep mode is equal to the amount of energy needed for 4 days of cooking. The energy consumed by multiple devices in sleep mode can be significant.

And finally, there is a phenomenon that may be invisible at an individual level but has a large impact on a national scale: the electric consumption in the evening when a large part of electricity needs are concentrated within a few hours. At that time, everyone returns home and turns on all of their devices (televisions, computers, washing machines, ovens, etc.). The demand is such that the national consumption sees a veritable peak during this period. Since little to no energy can be stored, power plants must provide this energy in real time. French power stations are sized based on this energy demand at the start of the evening.

If electricity consumption were spread out over the day, many electric power plants could be closed. In answer to this need, it is possible to program certain devices to run during the night, or even better, during the day to take advantage of solar photovoltaic panels that are becoming increasingly present.

L nergie dans l habitat E Sp cifique.png




Étape 11 - Conclusion

Energy consumption in the French household is significant. The first step in individual energy transition is not to change the source of energy and/or the scale of production. The installation of photovoltaic panels or windmills is not economically and ecologically impactful if there is not a significant reduction in energy consumption first.

However, reducing your consumption does not mean depriving yourself of comfort; it means making your home more efficient. Above all else, efficiency is limiting losses. Since more than 70% of energy is consumed in heating, losses can be limited by well insulating the home.

Once these losses are reduced, then it is possible to look for solutions that use less power. The alternatives are numerous and attractive, both low-tech and conventional:

Woodstove Solar heating Solar water heater Bioclimatic architecture Wind power Solar panels Biogas Norwegian pot Pot skirt

Notes et références

https://www.connaissancedesenergies.org/fiche-pedagogique/mix-energetique-de-la-france http://www.statistiques.developpement-durable.gouv.fr/energie-climat/r/consommations-secteur-tous-secteurs.html?tx_ttnews%5Btt_news%5D=21060&cHash=4168b27f68d9955400f2c25b0419095f https://www.ecologique-solidaire.gouv.fr/collection-datalab http://ines.solaire.free.fr/gisesol_1.php# https://fr.wikipedia.org/wiki/Conductivit%C3%A9_thermique https://www.connaissancedesenergies.org/fiche-pedagogique/mix-energetique-de-la-france https://www.e-rt2012.fr/explications/conception/explication-architecture-bioclimatique/ http://www.solaire1300.ch/f/technologie-solaire/rayonnement-solaire-delivre-par-heure.asp http://www.ademe.fr/particuliers-eco-citoyens/habitation/renover/isolation/isolation-toit-murs-planchers

English translation : Brianna Lale.

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