Wind power - an explanation
There are a number of structural elements in a Small Wind Power System -
Wind turbine
The wind turbine is the part of the system that generates electricity. Our wind turbine is a downwind design which means that the blades are on the side of the tower that faces away from the wind. The turbine directly drives an electrical generator, which in itself is driven by the rotor. We use a three-bladed rotor, as it provides a good compromise between efficiency and rotor balance. Our wind turbines protect themselves from high winds by a patented device which twists the blades out of the way when the wind blows too strongly. This means that our turbines are safe no matter how strong the wind and they produce electricity whenever the wind blows, even in high winds.
The electricity generated is three phase alternating current (AC), which fluctuates in both frequency and voltage, depending upon the rotational speed of the turbine. This AC power is transmitted down the tower on wires, to a controller, which converts it to direct current (DC) to charge batteries. If the system is connected to the Grid, then the power is converted to match the specification of the Grid.
Tower
The tower is required to get the turbine up into the most efficient area of the wind flow. A wind generator tower is very often more expensive than the turbine. The tower puts the turbine up in the smooth strong winds that give the most energy. Three common types of towers are tilt-up, fixed-guyed, and freestanding. We tend to use the tilt-up type, as they are easier to access for maintenance. Towers must be specifically engineered for the lateral thrust and weight of the turbine; ours is a tapering tube, made from galvanised steel. It is bolted to a strong base, which is normally concreted into the ground. We can provide full details of the metal base; our Installation page shows a complete installation. The tower should be adequately grounded to protect your equipment against lightning damage.
Electrical system
This depends on how you plan to use the electricity generated.
- simple wind electric
- wind power with battery or generator backup
- grid connected
Simple wind electric
This is a system that simply has a turbine producing power, through an inverter, to power a house or some fixed use, like pumping water. This is unusual, because there is no backup for when the wind drops.
Wind power with battery and/or generator backup
This system has backup for when the wind drops. Banks of batteries can be charged by the wind turbine when the wind blows, and these cut in to provide power should the wind drop. It is possible to have batteries that provide power for up to three days. An alternative is to use a stand-alone generator which provides electrical power directly when the wind drops. This runs on diesel or petrol and can be noisy and smelly. However, if a backup system is required, it provides a ready answer. We'd expect to need it for only 50 to 200 hours in a year, depending on site conditions. This is a source of backup power with no limit, as long as you keep it fuelled.
Grid connected
It is possible to connect into the National Grid and sell any surplus generated energy from your wind turbine. The Grid also acts as a backup for when the wind drops, because it lets you draw power from the Grid. You will be paid for the surplus power and charged for the power you draw. In a well-designed system, these may well balance out. Generating enough power for your own needs and having a surplus to sell is a cost-effective approach. The cost of adding the Grid connection and a meter to measure the power whichever way it flows, plus the cost of having the meter read, does mean that there is a greater capital cost on installation. To make this cost worthwhile, it is worth considering a larger turbine and generating a net contribution of energy to the Grid.
You will earn Renewables Obligation Certificates (ROC) if you are generating electricity and these can be sold to electricity companies. Renewables Obligation is a legal requirement for electricity supply companies to buy or generate a set percentage of their electricity from renewable energy sources. and they can use the certificates to offset their obligation.
The electrical control equipment for a Grid connected system. This includes a meter to measure the electricity supplied to the Grid. |
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The base of the tower, fixed down to the base set in concrete. The hinge to allow the tower to be tilted can be seen in the foreground. |
Comparing wind and solar power
In terms of simplicity and in terms of power generation, wind power beats all other forms of renenewable energy for the individual or for a community. There is much debate about wind farms and wind power in general, when done on a large scale. Our interest is on a small scale, for the individual home, community or building. The choice is then between solar energy and wind energy (unless you have your own source of hydro power). Wind is a more readily available resource in the UK than sun. Further, a wind turbine is a cheaper and simpler way to generate power. A 2.5kW turbine will supply more than enough energy for the average home and occupies virtually no land. To generate the same power would require 56 solar panels to do the same job, covering a considerable area.
Solar panels are very good at generating heat directly, so they are mostly used for domestic water heating. They are not so good for generating electricity. The opposite is true for wind power; it is very good at generating electricity, because the rotor directly drives a generator. The electricity generated can be used to generate heat, provide light and drive motors, so is much more useful.
Wind power is an appealing way to generate your own power. The process is fully visible, occupies little space and is efficient.
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