Stroing Wind Energy in Batteries

Introduction

Wind power is the conversion of wind energy into a useful form, such as electricity, using wind turbines. Wind energy has historically been used directly to propel sailing ships or converted into mechanical energy for pumping water or grinding grain, but the principal application of wind power today is the generation of electricity. Large scale wind farms are typically connected to the local electric power transmission network, with smaller turbines being used to provide electricity to isolated locations. Utility companies increasingly buy back surplus electricity produced by small domestic turbines. Wind energy as a power source is favored by many environmentalists as an alternative to fossil fuels, as it is plentiful, renewable, widely distributed, cleans, and produces lower greenhouse gas emissions.

A wind turbine is a rotating machine which converts the kinetic energy in wind into mechanical energy. If the mechanical energy is used directly by machinery, such as a pump or grinding stones, the machine is usually called a windmill. If the mechanical energy is then converted to electricity, the machine is called a wind generator, wind turbine, wind power unit (WPU), wind energy converter (WEC), or aerogenerator.

Now the main drawback with using wind enrgy directly witout storage is that wind does not blows all the time, and usually blows when it’s least required i.e. during nights. So storing wind energy in batteries is a very novel idea for making wing energy reliable for industrial use.
How Wind Turbines are used

Installing a wind turbine is a bit more involved than installing solar panels, but they are still relatively easy to incorporate into your alternative energy system. The turbine needs to be mounted in an area free from obstructions to wind flow (nearby buildings, trees, etc.).

When installing the controls and wiring of a wind generator, it is important to understand two fundamentals:

Current Rectifiers: Wind generators do not produce DC electricity, so a device called a “rectifier” is used to convert the turbine’s output current to DC.

Some turbines have a rectifier built in. In most cases though, the rectifier is supplied as a separate component that must be installed between the wind turbine and the battery. Often, the rectifier is combined with a charge controller into one complete wind turbine control unit.

Load Diversion: Solar panels are “passive” electricity producers. Even though the sun is shining, they only produce electricity when a charge is needed by the battery. Wind generators are “active” electricity producers. If the wind is blowing, they will produce current whether the battery bank needs the charge or not. In order to prevent damage to the wind turbine, all of the electricity it produces must be “used” in some way.

A load diverting charge controller regulates wind generator output so your batteries receive charging current when they need it, and any excess electricity generated by the wind turbine is diverted to an alternate load when the batteries are fully charged.

Some wind turbines have charge control features built-in, diverting their own excess current and allowing it to dissipate as heat through the wind turbine housing. In most turbine systems however, the charge controller is an external unit, and while DC rectifiers are always included as part of a basic wind turbine package, the load diverting controller may not be.

Some load-diverting charge controllers come with a heat-sink resistor to attach as the diversion load. When the batteries reach full charge, the load-diverting controller will simply send electricity to this resistor, where the energy will be released as heat. Some wind turbines have diversion features built into the turbine body itself, and the turbine’s outer shell acts as a heat sink for the excess power. Many charge controllers allow you to use the diverted current for other uses, such as running a water heating coil, a ventilating fan or a space heating system, making the wind generator an even more useful and efficient source of power.

Once a load-diverting charge controller is attached between the wind turbine and the storage batteries, your electrical system can be connected to the batteries, either directly for a matching-voltage DC system, or through an inverter for an AC or mixed AC/DC system.
Types of Wind Generators

Wind turbines come in a range of output voltages, to match the overall voltage of your electrical system. While 12 volt is common for small to mid-sized systems, large systems can be designed in 24 or 48 volt configurations.

The primary consideration in a wind generator is the average wind speed at the installation site. A different turbine will give optimum performance at a site with average wind speeds below 15mph than one at a site with speeds in the low 20mph range. Generally, low speed generators will either have longer rotor blades or a larger number of short, wide blades to maximize power drawn from minimal wind. High speed generators may be built of more durable material, and will have narrow, relatively short blades to minimize potential rotor damage in extremely high winds.

Before choosing which type of turbine is best for a particular site, some sort of wind speed measurement should be taken for a few consecutive months (or ideally, a full year). With long term wind measurements an accurate average wind speed can be calculated, as well as determining likely maximum wind speeds. Armed with this information, a turbine can be chosen that will maximize performance at the average wind speed, as well as one that will withstand the likely maximum forces.

Batteries for Storing Wind energy

The picture here is a schematic of one of the sodium-

Sulfur batteries. “The battery is made up of twenty

50-kilowatt modules. It is roughly the size of two semi trailers

and weighs approximately 80 tons. The battery is able to

Store about 7.2 megawatt-hours of electricity, with a

charge/discharge capacity of one megawatt. When the

wind blows, the batteries are charged. When the wind calms

down, the batteries supplement the power flow.

Fully charged, the battery could power 500 homes for over 7 hours.” (Credit: Xcel Energy)

Hours. So where are these batteries coming from?

“The energy storage in question — a series of sodium-sulfur batteries from NGK Insulators, Ltd. — can store roughly seven megawatt-hours of power, meaning the 20 batteries are capable of delivering roughly one megawatt of electricity almost instantaneously, enough to power 500 average American homes for seven hours.

That removes one of the big hurdles to even broader adoption of wind power: so-called intermittency. In other words, the wind doesn’t always blow when you want it to, problem Remote places faced earlier when a drop in wind generation forced cuts in electricity delivery. But with battery backup, the 11-megawatt wind farm, can deliver a set amount of electricity at all times, making it more reliable or, in industry terms, base-load generation. Plus, the battery effectively doubles the wind farm’s output at any given moment—both the megawatt being produced by the wind farms itself (that would otherwise have gone to charging the battery) and the megawatt delivered by the battery.

Business Application
Cost

Wind Batteries cost 3 million $ per Megawatt

Wind Turbines cost around 2800$ to 4000$

Wind generators cost 1.5$/watt for more than 10000 Watt wind system

Till now Wind Batteries are expensive and so is the initial establishment for wind energy storage and use. But with the renewable use concept and 5-6 time charge discharge batteries and more improvement to come ,it is and excellent idea to invest .
Carbon Credits

Carbon Credits are certificates issued to countries that reduce their emission of GHG which causes global warming.

Carbon credits are measured in units of Certified Emission Reductions (CERs).Each CER is equivalent to one tonne of carbon dioxide reduction.

Countries can trade in the international carbon credit market. Countries with surplus credits can sell the same to countries with quantified emission limitation and reduction commitments under the Kyoto Protocol.

1 CER ≡ 1 M.T. of CO2 emissions

These allowances can be sold privately or in the international market at the prevailing market price. Each international transfer is validated by the UNFCCC. Climate exchanges have been established to provide a spot market in allowances, as well as F&O market to help discover a market price and maintain liquidity

Carbon prices are normally quoted in Euros per tonne of carbon dioxide or its equivalent (CO2e).The prices of 1 CER is around 15 Euros currently.

To trade in Carbon Credits many countries and big industrialists are interested to explore in pollution free investments in developing countries. Wind energy is in that way a very promising area of investment. With the voice against pollution and depletion of resources that eye coal depletion around 2050 and strict anti-pollution laws till 2020 employing wind energy storage set-up now would be fetching never stopping profits with least employment and power consumption.

Benefits of Wind Energy

Like solar power, a wind energy system is an entirely clean source of power. The only potentially hazardous materials involved are the storage batteries. Wind turbines produce no emissions, use no traditional fuel, and can provide reliable year-round power given the right location.

Wind generators require relatively little maintenance, but it is recommended that the generator receives annual visual check-ups to ensure the propeller blades haven’t been damaged. If the turbine is located in a good spot it’s very unlikely to be damaged by any flying debris, but a chipped or cracked blade can be a hazard should it break completely, and a chipped or damaged blade will also negatively affect the turbine’s performance.

Wind turbines are very useful in almost any marine or household electrical system. In marine use, the movement of the boat will raise enough breezes to get the generator turning even when actual winds are fairly low, making them an extremely reliable source of on-board power. For residential systems, wind power can be a wonderful source of power during low-light winter months and even year-round, depending on the site. They can also be configured to power dedicated water pumping systems, which may be of particular interest to individuals currently without running water.

For commercial and industrial use, wind turbines are particularly useful in rugged remote locations such as mountaintop repeater stations or offshore oil platforms. High elevation and offshore or seaside remote sites often have fairly high year-round wind current that will make the most of wind generation systems. Industrial grade wind generators are available to withstand the worst storm winds present at such sites.
Conclusion

With the increase in Global Wind market and increased power consumption the need to store renewable resource generated energy has greatly increased. Wind energy with it’s global availability and pollution free generation appeals for a recent investment. With special batteries designed to store wind energy it can now be used with reliability to provide household plus industrial power. Also wind energy is being used in sub-marines, off shore refineries and aeronautics. Inspiring only long term investments till date, wind energy promises to keep it safe from future years recession expected with petroleum and coal depletion.

With industrialists and government feeling socially responsible to contribute against global warming and pollution issues exploring ways to store wind energy serves all causes to the best.

References :

[1] http://blogs.zdnet.com/emergingtech/index.php?cat=9&submit=view

[2] http://www.sciam.com/article.cfm?id=storing-the-breeze-new-battery-might-make-wind-power-reliable

[3] http://www.absak.com/library/wind-turbine-home-power

[4] http://www.scribd.com/search?cx=007890693382555206581%3A7fgc6et2hmk&cof=FORID%3A11&ie=UTF-8&c=all&q=storing+wind+energy&sa=Search#1349

Here I would like to thank Pranjal paliwal and Gaurav Agarwal to prepare this report.