An inverter is an essential part of any system that generates DC power and converts it into AC power. Modern renewable energy generation systems produce DC, mostly by using solar panels, so special inverters have been developed, depending on the way they are connected.
Large wind turbines that you see dotted around the countryside generate AC power, so don’t need any conversion. They need to be synchronized to mains grid power so that generated power can flow seamlessly into the general supply.
Unlike their bigger versions, smaller wind turbines that might be used for domestic electricity generation generally produce DC power and needs a wind turbine inverter to convert the direct electricity to AC power suitable for household appliances and the grid.
What does an inverter do?
A solar panel is a conversion device. It converts the sun’s energy or radiation into electrons which flow together as an electric circuit. A wind turbine produces electricity in a very different way by using a rotating generator consisting of magnets and copper windings.
Small wind turbines are very similar in operation to a car alternator. All generators create a wave of electricity because they move in an arc. If a turbine is used to charge batteries, such as used for energy storage in off-grid domestic generation systems, then the electricity is converted into DC by a commutator mounted on the rotating part.
Another circuit consisting of rectifiers, capacitors and reactance coils to smooth out the resulting DC ‘ripple’.
The output of a DC wind turbine is used much like solar output, either for charging batteries used as energy storage or in the household for appliances. Paradoxically, the DC power has to be converted to a suitably smooth form of AC before it can be used in the home.
Are wind turbine inverters different from solar inverters?
All power generation components have a power curve, or voltage-current curve. The MPP or Maximum Power Point for solar panels and wind turbines is different and so inverters used for each will be slightly different.
In particular, solar panels output is very predictable over the irradiation range, while the output of a wind turbine can vary dramatically, needing an inverter with a wider range and the ability to accommodate greater peaks in power generation.
There are inverters on the market which can handle both types of generation using switching to adjust connections of internal components, but in general it’s a good idea to use dedicated inverters for each purpose. Wind turbine inverters can be purchased for both off-grid and grid-tie installations.
Do I need a wind turbine inverter?
It all depends on the purpose of the wind turbine. If you have DC appliances or devices, then there’s no need for an inverter. In an off-grid situation it’s normal to have a substantial bank of deep-cycle batteries and it makes sense to use the DC output from a turbine to do this.
Is a wind turbine charge controller the same as a solar charge controller?
A wind turbine charge controller is different from a solar charge controller. It ensures that the turbine doesn’t over-speed and run out of control once the batteries are charged up or there is no load on the output.
How to Choose A Wind Turbine Charge Controller
The majority of wind turbine charge controllers have been adapted from solar charge controllers, so it’s quite rare to find one developed specifically for the purpose.
Make sure that the specifications of each device match:
- Type of output – single phase AC, 3 phase AC or DC
- Controller power rating – should be 50% more than the maximum turbine output
- Battery type – not all charge controller support all battery chemistry
- Battery voltage – the charger output will have a range, do not exceed
What is a dump load controller?
A wind or water turbine generates power as long as the force that drives it is maintained. Once a battery bank is fully charged, the generated electricity is no longer required and the turbine sees this as an almost no-load condition.
The resistance to rotation normally presented by the magnets inside the machine no longer applies and the turbine rotates dangerously fast, as fast as the wind blows. A wind turbine can actually self-destruct if some means of slowing it down isn’t built in.
A dump load is a way of maintaining a turbine’s output load so that its speed is kept down to the working range. A common way of doing this is to automatically switch in a resistance load to ‘soak up’ the extra power. This function is managed by a dump load controller, also known as a diversion load controller.
A great way to do this is to this is to connect water heaters as a dump load, either domestic of in the form of heat exchangers for an outdoor pool heater. In this way the power is not going to waste.
Are domestic wind turbines worth it?
Well, the jury’s still out on that one. It depends on who you listen to. My general feeling is that it really does depend on your location. If you live in an area that has consistent wind speeds substantially above the minimum recommended of 5m/s, for 9 months of the year, then it can be viable.
Even so, it’s advisable to install a solar-wind hybrid system, so that wind is available when the sun is not and vice versa.
How much does a home wind turbine cost?
A professionally installed domestic wind turbine will cost about $8.50 per watt, so quite substantial. The average house will need about 5 to 10kW of generation capacity, so at the upper end you would need a capital outlay of $85000!
For comparison, you could have over 28kW of solar panels installed for the same price. There are added advantages with solar, like no moving parts, a dump load is not necessary, parts need much less maintenance and the overall life is longer.
Maintenance costs tend to be in the range under 1% of capital costs, so for our hypothetical 10 kW installation you may need $850 per annum – much less than solar which is about $350 per year.
Although household renewable energy costs are tumbling down year over year, either solar or wind still represents a huge investment that takes 7 to 10 years to amortize, even with government assistance in the form of grants.
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The cost is greater if an off-grid system is considered, simply because a large bank of deep-cycle batteries adds something like 30% to the overall cost. A much better option is to opt for a grid-tie installation.
In a grid-tie wind-turbine system a dump-load is not required because there is always a load in the form of the electricity grid. If the household appliances are not pulling current then the supply grid accepts as much as a wind turbine can produce.
Extra safe-guards need to be put in place if the grid goes down. In this case, if the load is lost (the grid) and the turbine can overspeed, possibly destroying itself, so an emergency dump-load would need to be switched in temporarily.
Can I use a solar charge controller for wind?
No. Although many wind charge controllers have been developed from solar controllers and they both regulate battery charge levels, wind controllers need to dump excess load once the batteries are fully charged. If excess load is not dumped, then the wind turbine can overspeed and even self-destruct.
How much wind in your area? windy.com
Global Wind Atlas globalsolaratlas.info
Solar Direct Wind Power SolarDirect