Le vent comme source d'énergie

Éoliennes / les éoliennes viennent dans toutes les formes et tailles, mais vous les reconnaîtrez très probablement sous leur forme industrielle, d'énormes hélices blanches sur des tiges blanches géantes s'élevant jusqu'à 80 mètres de haut. Il est très peu probable que votre projet OffGrid ait besoin d'un monstre de 150 kW. However in most areas a smaller wind turbine around the size of 400watt-3kw can be a worthwhile investment. The wingspan of these are 1m to 3m and will still fit into the landscape without standing out or producing too much noise. Tout simplement, le vent tourne l'hélice / pales autour d'un rotor, qui tourne un arbre, qui se connecte à un générateur pour produire de l'électricité. Une éolienne générera généralement 30% de son rendement maximum théorique un jour légèrement venteux.

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Avoir au moins une éolienne dans les projets OffGrid est recommandé, even when your location is not particularly windy on normal conditions. During bad weather phases especially Autumn wind can be a very good source of energy to keep your batteries happy over longer periods of little to no solar. It also helps on battery lifetime to have the occasional charge in the night, même si ce n'est 20 minutes. La grande différence avec le solaire est, do not size wind generators to big! A wind turbine will need to “se débarrasser” d'énergie produite, if your battery is full and you did not install a resistor to burn off the excessive power you risk damaging your equipment. to give a rough idea, some 500w input for every 300ah of battery should be considered maximum.

Small wind turbines

Small wind turbines, also known as micro wind turbines, are used for microgeneration of electricity, as opposed to large commercial wind turbines, such as those found in wind farms. Small wind turbines often have passive yaw systems as opposed to active ones. They use a direct drive generator and use a tail fin to point into the wind, whereas larger turbines have geared powertrains that are actively pointed into the wind.

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Small wind turbines typically produce between 500 W and 10 kW of power, although the smaller turbines may be as small as a 50 Watt auxiliary power generator for a boat, caravan, or miniature refrigeration unit

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The generators for small wind turbines are usually three-phase alternating current generators and the trend is to use the induction type, although some models utilize single-phase generators or direct current output.

After running the three phase AC wire through a slip ring and down to the receiving end, a three-phase rectifier is used to convert the AC to rectified DC for battery charging, especially in solar hybrid power systems. The rectifier should be mounted to a heat sink for cooling, with the option of adding a computer fan that is activated by a bimetal thermal switch for active cooling.
A three phase rectifier being used on a rooftop mounted urban wind turbine.

The DC end of the rectifier is then connected to the batteries. This connection should be as short as possible to avoid power losses, typically with a shunted digital wattmeter in between for monitoring. The batteries are then connected to a power inverter, which converts the power back to AC at a constant frequency for grid connectivity and end use.

Types de éoliennes

Éoliennes horizontales

Ce sont les modèles auxquels vous êtes probablement le plus habitué.
For best results they need to be put on a pole and above roof level, or in reasonable distance to any objects that influence wind flow. Ils fournissent très peu ou pas de puissance pendant les temps de mouvement d'air lents, mais produira une puissance raisonnable lors de vents moyens et forts. Horizontal wind generators do create a certain level of noise. Although not loud, you can certainly hear it when the blades are spinning. Installing one right above your sleeping room might not be the smartest thing to do. Generally they are a bit cheaper than vertical ones.

Éoliennes verticales

Ceux-ci fournissent de l'énergie même avec le plus petit mouvement d'air. Vertical wind generators are a lot less influenced by turbulence, car il n'y a pas de nez qui doit pointer vers le vent, but instead they can utilise wind from all directions at the same time. Si vous prévoyez d'installer une seule éolienne pour votre projet, a vertical one will provide more reliable power. Ceux-ci peuvent être installés directement sur le toit ou, il n'est pas nécessaire de les mettre sur un poteau.

Variability

Wind power is variable, and during low wind periods, it must be replaced by other power sources. Transmission networks presently cope with outages of other generation plants and daily changes in electrical demand, but the variability of intermittent power sources such as wind power is more frequent than those of conventional power generation plants which, when scheduled to be operating, may be able to deliver their nameplate capacity around 95% of the time.

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Electric power generated from wind power can be highly variable at several different timescales: hourly, daily, or seasonally. Annual variation also exists but is not as significant. Because instantaneous electrical generation and consumption must remain in balance to maintain grid stability, this variability can present substantial challenges to incorporating large amounts of wind power into a grid system. The combination of diversifying variable renewables by type and location, forecasting their variation, and integrating them with dispatchable renewables, flexible fueled generators, and demand response can create a power system that has the potential to meet power supply needs reliably

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Solar power tends to be complementary to wind. On daily to weekly timescales, high-pressure areas tend to bring clear skies and low surface winds, whereas low-pressure areas tend to be windier and cloudier. On seasonal timescales, solar energy peaks in summer, whereas in many areas wind energy is lower in summer and higher in winter. Thus the seasonal variation of wind and solar power tend to cancel each other somewhat. Wind hybrid power systems are becoming more popular.