.....Wind is a clean, inexhaustible, ‘green’, sustainable energy resource that can generate sufficient electricity to power millions of homes and businesses.
Wind energy is one of the fastest-growing forms of global electricity generation. Currently, the US, for instance, can generate more than 10,000 MW of electricity via the wind, enough to power 2.5 million average American homes, with future estimates predicting wind energy could supply 20 per cent of that nation’s energy needs. Contemporary multi-megawatt wind turbines can now compete on a par with conventional energy sources and are far safer and greener in that their pollution and CO2 emissions
are zero.
A short history
of wind power
Wind power has been an integral part of energy generation for the past 1,400 years, starting in Persia in the 7th century. Windmills have been common throughout Europe since the 12th century, being used largely for grinding/milling grain, sawing timber, making paper and pumping water and were naturally taken to America with the first immigrants. The average windmills managed to generate 25-30 kW of mechanical power. However, the most powerful, in the mid-19th century, were capable of generating a staggering 1,500 MW of power; an achievement unsurpassed until 1988!
While commonly used as water pumps, it wasn’t until the 1930s that wind devices, in the form of wind turbines, were used to generate electricity. These ‘wind-chargers’ were small appliances that charged small batteries and were the forerunners of today’s modern wind turbines.
The contemporary wind turbines were pioneered by the alternative technology movement in Europe and the States in the late 1960s and popularised following the oil crisis of 1970s.
Of all the countries which attempted to develop wind turbines as an alternative source of electrical power only Denmark was successful and this technology was later adopted by the rest of the world.
Today’s wind turbines have benefitted from the advances in design, material and battery technology made during the 1980s and 1990s, resulting in the contemporary efficient models. A modern wind turbine, the same size as its mediaeval European forerunners, can generate 250-300 kW of power — approximately a tenfold increase in efficiency. Wind power as an effective contributor to the national grid makes use of wind farms where, typically, up to 108 individual wind turbines can generate as much as 162 MW of electricity, like, for example, the Colorado Green Wind Farm.
Domestic wind turbines
Wind energy is essentially a supplement or back-up power supply to the electricity provided by your normal electricity supplier. It won’t normally supply all your domestic electricity needs, but a modern wind turbine can make substantial savings on your electricity bill, providing a third and up to a half of domestic power requirements, dependent on location, wind speed, and the size and sophistication of the wind turbine; they will also substantially reduce your carbon footprint. Small wind turbines, generating on average 100 kW of electricity are ideal for homes, small farms or a small business. The typical size range is from approximately 7 feet (2m) to 25 feet (8m) in diameter to produce electricity at a rate of 900-10,000 watts at their tested wind speed. Manufacturers claim that the latest models are inaudible, even a few feet under the turbine. The modern versions also use a system known as ‘dynamic braking’, similar to differential gearing, which regulates the speed by dumping excess energy, so that the turbine continues to produce electricity even in high winds. To give you some idea of domestic wind turbine use in the developed world, in 2007, approximately 3,500 micro- and small-wind turbines were in use in the UK, with 2008 and ’09 figures expected to be considerably higher.
Feasibility of wind turbines
Location is the key factor. Ideal situations are as follows:
l an area that has adequate amounts of wind;
l a sufficiently high area;
l 10 metres above and 76 metres from any obstructions;
l minimum wind speed should be about 10 kmph;
l your property should be at least an acre (4,047m2 ), unless the wind turbine is roof-mounted;
l the distance between you and your neighbours should be at least 200-300 metres;
l pole-mounted, in a large garden or field, is superior to a domestic rooftop installation;
l the ideal location would be on a hilltop, in a valley funnelling winds from the shore, or on a shoreline with few trees.
You should also be aware that the amount of electricity provided by a wind turbine will vary, according to the size of the model, how much wind there is and how strong the wind speed. While urban environments aren’t ideal, progress is being made in wind turbine development in this area.
Wind speeds
Wind turbines start producing power at a wind speed of 7.5 mph, and increase their output up to 45 mph winds. Higher wind speeds require the blades to be slowed down, to reduce vibration and protect the equipment, but are very effective in wind speeds in this range (7.5 - 45 mph/12.07 - 72.42 kmph).
Technicalities to
assess viability
1 Average mean wind speed
You must first determine the average mean wind speed, or AMWS, calculated over the course of a year, with records being kept for three years. The technical minded will want to use an anemometer, which calculates wind speed, in conjunction with a data-logger. Alternatively, surf the Internet for yachting websites to find the average annual and seasonal wind speeds for your area. Jomtien, for instance, experiences north-easterly to westerly winds, ranging from 9.2-23 mph/14.8 - 37.01 kmph, so the area, especially near the coast, is ideal.
2 Wind energy output
Wind energy output is calculated using the cube rule, which states that each time the wind speed doubles, the output from the turbine increases by eight times. Also, by doubling the diameter of the blade, you increase the electricity output by four. The larger the turbine, the larger the rotor.
The mechanics
of wind turbines
There are two types of wind turbines: those with a horizontal axis and those with a vertical one. The more common horizontal axis type is attached to a tower, whereas, the vertical ones are usually anchored to the ground.
The horizontal axis turbine rotates and tacks, or tracks and turns into the wind, using a tail-vane. With this type, the blades are aligned to the turbine’s centre of gravity, and are thus more stable, having more control and being designed to maximise wind energy capturing.
The mounting tower gives access to high winds, with as much as 20 per cent higher speeds. The tower height should be at least 30 feet (9m) higher than anything within 500 feet (152m). However, the tower can’t be too high as the destructive vibrations from wind turbulence will damage the structure.
This vibration factor is one of the reasons why a tower mounting is superior to a roof-mounted model, vibrations from which can actually damage the roof itself.
The vertical axis type is fixed on the ground and orients towards the predominant wind direction. This type is costly and difficult to install. However, its advantages are: higher pitch angle for airfoil, enhanced power generation, less risk of breaking and the ability to orient itself to the wind direction. On the downside, they only produce 50 per cent of the energy of their horizontal cousins, must stand on very flat land, have low starting torque, and need guy wires that could cause stress on the bearings that hold the turbine together.
Battery storage
Domestic wind turbines are essentially DC battery chargers. As wind variation makes for inconsistent energy production, battery storage is crucial.
Great strides have been made in terms of battery efficiency in recent years and the knock-on effect of the necessity of producing hyper-efficient, long-life batteries for lap top computers, electric cars and military and avionic uses promises further efficiency improvements in the future. They come in 3 sizes: 12 VDC, 24 VDC, or 48 VDC, matched to the type of turbine, with a typical wattage range of 400-10,000 watts. Batteries are also installed in banks or series.
One essential with batteries, however, is that they must be located close to the house, otherwise voltage drop will be experienced, proportionate to the distance involved. As a price guideline, in the UK, the cost for typical, deep cycle 85Ah 12V batteries is £47.50 (approx Bt2,440) and £69 (approx Bt3,550) for the 110Ah 12V batteries.
These prices will probably be higher in Thailand because of import duties. Another vital consideration is the need to insulate the batteries against extreme heat, rain or mould.
The cost of wind turbines
Unfortunately, the cost of domestic wind turbines is not cheap and most need to be installed by experienced technicians, not least because they must be integrated with the domestic electricity supply. They are connected to your electrical meter and are so phased that when there is enough wind energy, you use your own renewable energy, with low or no winds, the grid electric kicks in seamlessly, theoretically.
In the States, turbines with outputs of 2-10 kW have a typical price range US$12,000 - 55,000 installed (US$6 per watt). The Thai government is giving subsidies, but the suppliers are usually the only ones privy to this information. The US manufacturer, Southwest Windpower, estimates a turbine will pay for itself in energy savings in 5-10 years.
In the UK, typical .4-1,5 kW turbines, including installation, range from £1,600-4,000 (approx Bt82,230-206,000). A much cheaper route is to buy the lower rated, lightweight micro-turbines with a range of power outputs from 200W-1kW. These are simple to install and cost between £350-800 (approx Bt18,000-41,000) made by Alian Energy Solutions, UK.
For the latest developments, log onto Wikipedia/Small wind turbine and click on the links.
Do it yourself (DIY)
This is by far the cheapest route and surfing the web will yield some fine examples. However, you do need to be relatively adept with tools and sensible in following safety precautions. A complete step-by-step DIY guide is available from http://www.re-energy.ca/pdf/wind-turbine.pdf
Conclusions
Though by no means cheap to purchase, astute shopping around, using the Internet will pay dividends. Import and shipping could be a hassle, but nothing ventured, nothing gained and remember, the system will pay for itself in between 5-10 years and you’ll be helping to save the planet – who can put a cost on that? Ω
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