We all know that the main power grid will most likely end up crashing after a few short months after the main onslaught. We all like to think about how we'll supply our group and family with power. The first thought is always a generator. But the gas supply will end sooner or later.

   So then we'll have to turn to other forms of power to supply to our compounds or buildings. I would like to believe that the best way to supply the power we all need will be the use of three power sources. Using windmills, solar panels and generators we should be able to keep our safe havens supplied properly for long term. So I decided to supply or at least try and get people thinking about other forms of power in order to keep our lives somewhat on the normal side.

   We'll start with windmills. Harnessing the mother nature for our survival, besides using the rain water for drinking and cooking, animals and plants for food. 

Wind power

From Wikipedia, the free encyclopedia

   

Burbo Bank Offshore Wind Farm, at the entrance to the River Mersey in North West England.

The Shepherds Flat Wind Farm is a 845 megawatt (MW) wind farm in the U.S. state of Oregon.

Wind power is the conversion of wind energy into a useful form of energy, such as using wind turbines to make electrical power, windmills for mechanical power, wind pumps for water pumping or drainage, or sails to propel ships.

Large wind farms consist of hundreds of individual wind turbines which are connected to the electric power transmission network. Offshore wind is steadier and stronger than on land, and offshore farms have less visual impact, but construction and maintenance costs are considerably higher. Small onshore wind farms provide electricity to isolated locations. Utility companies increasingly buy surplus electricity produced by small domestic wind turbines.^[1]

Wind power, as an alternative to fossil fuels, is plentiful, renewable, widely distributed, clean, produces no greenhouse gas emissions during operation and uses little land.^[2] The effects on the environment are generally less problematic than those from other power sources. As of 2011, Denmark is generating more than a quarter of its electricity from wind and 83 countries around the world are using wind power on a commercial basis.^[3] In 2010 wind energy production was over 2.5% of total worldwide electricity usage, and growing rapidly at more than 25% per annum. The monetary cost per unit of energy produced is similar to the cost for new coal and natural gas installations.^[4]

Wind power is very consistent from year to year but has significant variation over shorter time scales. The intermittency of wind seldom creates problems when used to supply up to 20% of total electricity demand,^[5] but as the proportion increases, a need to upgrade the grid, and a lowered ability to supplant conventional production can occur.^[6] Power management techniques such as having excess capacity storage, geographically distributed turbines, dispatchable backing sources, storage such as pumped-storage hydroelectricity, exporting and importing power to neighboring areas or reducing demand when wind production is low, can greatly mitigate these problems.^[7] In addition, weather forecasting permits the electricity network to be readied for the predictable variations in production that occur.

Mechanical power

Medieval depiction of a wind mill

Sailboats and sailing ships have been using wind power for thousands of years, and architects have used wind-driven natural ventilation in buildings since similarly ancient times. The use of wind to provide mechanical power came somewhat later in antiquity. The windwheel of the Greek engineer Heron of Alexandria in the 1st century AD is the earliest known instance of using a wind-driven wheel to power a machine.^[10][11]

The first windmills were in use in Persia at least by the 9th century and possibly as early as the 7th century.^[12] The use of windmills became widespread across the Middle East and Central Asia, and later spread to China and India.^[13] By 1000 AD, windmills were used to pump seawater for salt-making in China and Sicily.^[14] Windmills were used extensively in Northwestern Europe to grind flour from the 1180s,^[13] and windpumps were used to drain land for agriculture and for building.^[15] Early immigrants to the New World brought the technology with them from Europe.^[15]

In the US, the development of the water-pumping windmill was the major factor in allowing the farming and ranching of vast areas otherwise devoid of readily accessible water.^[16] Windpumps contributed to the expansion of rail transport systems throughout the world, by pumping water from water wells for steam locomotives. The multi-bladed wind turbine atop a lattice tower made of wood or steel was a century a fixture of the landscape throughout rural America.^[17]

In 1881, Lord Kelvin proposed using wind power when coal ran out, as "so little of it is left".^[18] Solar power was also proposed, at about the same time.^[19]

Wind energy

Wind energy is the kinetic energy of air in motion, also called wind. Total wind energy flowing through an imaginary area A during the time t is:

^[26]

where ρ is the density of air; v is the wind speed; Avt is the volume of air passing through A (which is considered perpendicular to the direction of the wind); Avtρ is therefore the mass m passing per unit time. Note that ½ ρv² is the kinetic energy of the moving air per unit volume.

Power is energy per unit time, so the wind power incident on A (e.g. equal to the rotor area of a wind turbine) is:

^[26]

Wind power in an open air stream is thus proportional to the third power of the wind speed; the available power increases eightfold when the wind speed doubles. Wind turbines for grid electricity therefore need to be especially efficient at greater wind speeds.

Map of available wind power for theUnited States. Color codes indicate wind power density class. (click to see larger)

Wind is the movement of air across the surface of the Earth, affected by areas of high pressure and of low pressure.^[27] The surface of the Earth is heated unevenly by the Sun, depending on factors such as the angle of incidence of the sun's rays at the surface (which differs with latitude and time of day) and whether the land is open or covered with vegetation. Also, large bodies of water, such as the oceans, heat up and cool down slower than the land. The heat energy absorbed at the Earth's surface is transferred to the air directly above it and, as warmer air is less dense than cooler air, it rises above the cool air to form areas of high pressure and thus pressure differentials. The rotation of the Earth drags the atmosphere around with it causing turbulence. These effects combine to cause a constantly varying pattern of winds across the surface of the Earth.^[27]

The total amount of economically extractable power available from the wind is considerably more than present human power use from all sources.^[28] Axel Kleidon of the Max Planck Institute in Germany, carried out a "top down" calculation on how much wind energy there is, starting with the incoming solar radiation that drives the winds by creating temperature differences in the atmosphere. He concluded that somewhere between 18 TW and 68 TW could be extracted.^[29] Cristina Archer and Mark Z. Jacobson presented a "bottom-up" estimate, which unlike Kleidon's are based on actual measurements of wind speeds, and found that there is 1700 TW of wind power at an altitude of 100 metres over land and sea. Of this, "between 72 and 170 TW could be extracted in a practical and cost-competitive manner".^[29] They later estimated 80 TW.^[30] However research at Harvard University estimates 1 Watt/m² on average and 2-10 MW/km² capacity for large scale wind farms, suggesting that these estimates of total global wind resources are too high by a factor of about 4.^[31]

Distribution of wind speed

Distribution of wind speed (red) and energy (blue) for all of 2002 at the Lee Ranch facility in Colorado. The histogram shows measured data, while the curve is the Rayleigh model distribution for the same average wind speed.

The strength of wind varies, and an average value for a given location does not alone indicate the amount of energy a wind turbine could produce there. To assess the frequency of wind speeds at a particular location, a probability distribution function is often fit to the observed data. Different locations will have different wind speed distributions. The Weibull model closely mirrors the actual distribution of hourly/ten-minute wind speeds at many locations. The Weibull factor is often close to 2 and therefore a Rayleigh distribution can be used as a less accurate, but simpler model.^[32]

High altitude winds

Power generation from winds usually comes from winds very close to the surface of the earth. Winds at higher altitudes are stronger and more consistent, and may have a global capacity of 380 TW.^[30] Recent years have seen significant advances in technologies meant to generate electricity from high altitude winds.^[33]

Wind power capacity and production

Worldwide wind generation up to 2010

Worldwide there are now over two hundred thousand wind turbines operating, with a totalnameplate capacity of 282,482 MW as of end 2012.^[44] The European Union alone passed some 100,000 MW nameplate capacity in September 2012,^[45] while the United States surpassed 50,000 MW in August 2012 and China passed 50,000 MW the same month.^[46][47]

World wind generation capacity more than quadrupled between 2000 and 2006, doubling about every three years. The United States pioneered wind farms and led the world in installed capacity in the 1980s and into the 1990s. In 1997 German installed capacity surpassed the U.S. and led until once again overtaken by the U.S. in 2008. China has been rapidly expanding its wind installations in the late 2000s and passed the U.S. in 2010 to become the world leader.

At the end of 2012, worldwide nameplate capacity of wind-powered generators was 282gigawatts (GW), growing by 44 GW over the preceding year.^[44] According to the World Wind Energy Association, an industry organization, in 2010 wind power generated 430 TWh or about 2.5% of worldwide electricity usage,^[48] up from 1.5% in 2008 and 0.1% in 1997.^[49]Between 2005 and 2010 the average annual growth in new installations was 27.6 percent.^[50]Wind power market penetration is expected to reach 3.35 percent by 2013 and 8 percent by 2018.^[50][51]

Several countries have already achieved relatively high levels of penetration, such as 28% of stationary (grid) electricity production in Denmark (2011),^[52] 19% in Portugal (2011),^[53] 16% in Spain (2011),^[54] 14% in Ireland(2010)^[55] and 8% in Germany (2011).^[56] As of 2011, 83 countries around the world were using wind power on a commercial basis.^[3]

Europe accounted for 48% of the world total wind power generation capacity in 2009. In 2010, Spain became Europe's leading producer of wind energy, achieving 42,976 GWh. Germany held the top spot in Europe in terms of installed capacity, with a total of 27,215 MW as of 31 December 2010.^[57]

WindMills

By Steve Graham for Networx

A strong wind gust and attractive rebates may not add up to a good deal on residential wind power. Several factors affect the amount of power generated by a home wind turbine. Homeowners should avoid general ratings and carefully study the potential power-generating capacity of a wind turbine on a specific site.

Power Ratings

Most turbines have a power rating in kilowatts (kW). The rating is somewhat like a car’s horsepower figure. It shows which engine or turbine is bigger, but isn’t a direct measure of the machine’s full energy output. The number of “horses under the hood” doesn’t indicate the fuel efficiency or top speed without vehicle weight, driving conditions and other stats. At least most car buyers have already owned a car, so they have a rough idea how to translate horsepower figures. However, homeowners are typically buying their first turbine, so they have nothing for comparison.

Utility bills are measured in kilowatt-hours (kWh) — power usage multiplied by time. For example, a 100-watt light bulb left on for 10 hours uses one kWh. Many companies and industry groups say a 10 kW system will generate about 10,000 kWh per year (equaling the average power usage in a U.S. home), but the real output will be higher or significantly lower. The turbine puts out a maximum of 10 kW under perfect conditions, so it could theoretically generate 10 kW for 24 hours a day 365 days a year, or 87,600 kW per year. With soft breezes, it will generate just a handful of watts.

Calculating the real power output of a wind turbine in watts involves multiplying the mechanical efficiency by the wind speed, air density, and rotor blade length.

Wind Speed

Wind speeds and other weather factors make a bigger difference to power output than a turbine’s parts. This U.S. Department of Energy map shows annual average wind speeds at 50 meters above the ground. Residential wind turbines have been installed in most U.S. states, but many areas do not have enough wind to spin turbines. No matter what the installer or manufacturer says, you won’t generate significant power at speeds below 10 miles per hour.

Above that threshold, energy increases exponentially with speed. A site with 12 mph winds can generate 70 percent more energy than a site with 10 mph winds.

Wind speeds also increase quickly with altitude. A 10 kW turbine generates 30 percent more power on a 100-foot tower than a 60-foot tower. The difference is greater if tall trees or structures block the wind or create turbulence.

Most wind turbines automatically shut down when wind speeds rise above 25 mph to avoid mechanical damage or bodily injuries. A relatively calm area with seasonal windstorms may never generate much wind capacity.

Turbine Size

The other major consideration is the size of the turbine’s rotor blade. Like wind speed, a larger blade will generate exponentially more energy. A 10-foot blade may not look much larger than an 8-foot blade, but the “swept area” is 58 percent larger. That corresponds with a 58-percent increase in energy production per blade rotation.

The other parts of the turbine differ in quality more than output. Look for a reputable company with quality parts and avoid claims of extreme power production.

You might get a good offer on a wind turbine rated at 10 kW, but without considering several mechanical and natural factors, it is hard to determine the actual electric production capacity.

So where do you start?  Who do you talk to?

• First establish whether you have sufficient wind in your area to make an installation viable.  You will need specialist tools to gauge this  accurately and you may choose to hire someone to do this for you.
• Look on local wind websites for information on wind patterns
• Speak to your local authority to check if there are any special planning permits required
• Find out how much energy you currently use so you know what size turbine to consider.  Your current energy provider can help you interpret your energy bill.
• Do a basic energy audit and see if you can insulate your home better to reduce energy consumption.
• Decide whether you want to use a commercial supplier or build your own windmill or home wind turbine
• Check out ready made kits and find out about separate installation costs
• It will certainly be cheaper to build your own turbine but it will require effort and some skill.  Larger turbines are not usually suitable for an inexperienced handyman
• It is still worthwhile doing some research into home wind turbines even if you employ a commercial supplier to educate yourself as to the suitability of the products that may be recommended.
• Wind turbines only produce energy when the wind blows, and are often used in conjunction with solar panels to give continual energy supply
• Home wind turbines also require a specialized battery to store energy
• Do not shop on price alone.  Be aware of noise requirements for your area – certain models are much quieter than others

Reliability

Wind power hardly ever suffers major technical failures, since failures of individual wind turbines have hardly any effect on overall power, so that the distributed wind power is highly reliable and predictable, whereas conventional generators, while far less variable, can suffer major unpredictable outages.