Wind grid tie inverter

booboo

Is there a grid tie inverter that works with small wind generators. I am looking at building a few homemade wind generators mostly as a hobby but would like to have them produce. I am not going to have batteries. I just need an inverter that will handle one to several of these wind generators. Cost would be the bigest factor rather.

BB.

Re: Wind grid tie inverter

The smallest I have seen is the SMA 700 watt WindBoy for around $1,500 (not listed on our host's website--but the can probably get them if you ask). This is not a "cheap" inverter... And I do not know if you can connect several wind turbines in parallel to one inverter or not. Lastly, I do not know if you can attach a "home made" non-UL listed wind turbine legally to a Wind Grid Tied Inverter...

I looked for a manual on SMA's site--and did not find one for the WindyBoy 700... So I do not know how it handles times when it is not converting power (AC down, etc.)--should be a load bank or short on the wind turbine output to prevent over-speed in windy conditions (or would require a wind turbine to manage its own over-speed protection).

The other issue I have read about is a concern about how the Anti-Islanding feature should be implemented... Many of the solar GT inverters (all?) seem to require both the output (AC Mains) and the Input (Panels) to have stable voltage (and frequency) for a period of 5 minutes before "connecting" to the grid (on the grid side, this requirement makes sense--grid needs to be stable before power is pumped back into the grid).

However, the way many GT inverters also require input power to be stable (above minimum input voltage/current requirements of the inverter's input stage) for 5 minutes works for solar--during the day, with anything other than "black" cloud cover, the 5 minute time-out is not a big issue...

However, with something as variable as wind, the inverters that have a 5 minute time-out waiting for "stable" wind turbine output--can reduce total output a whole bunch--between turbulent wind, over/under speed conditions with normal wind variability--it sounds like a major output killer with respect to wind.

I don't know if the 5 minute timeout on input power was required by UL/NEC, or just an interpretation by each of the manufacturers...

Also, this 5 minute delay may have been designed into the hardware... For example, the designer may have used the power from the DC input to run the processor to monitor the AC line voltage (as well as DC input). Not a big problem with Solar--which is, over all, a pretty stable DC input. Also, this saves wasted electrical power/load on the AC mains by powering the "electronics" from DC input--if there is not enough DC power available to power the electronics, there is no reason for the rest of the inverter electronics to be "awake".

But, every time the DC goes below minimums with a wind turbine (gust/lull), the processor resets (and turns off), and restarts the 5 minute timer... This type of design would be very difficult (if not impossible) to "fix" without a complete redesign of the GT Inverter.

Massachusetts Small Wind Report (PDF):

• The average capacity factor for 191 existing small wind turbines currently installed and reporting to the Production Tracking System (PTS) is 4%. This is less than half of the target capacity factor of 10%.
• Installers, on average, are significantly overestimating annual energy production. On average installers are overestimating energy generation by a factor of 3 to 4.
• The most prolific small wind installer, with 6 installations included in this analysis, is Installer 10. These systems are performing with an average capacity factor of 3%. The most commonly installed small turbine, using MTC funds, is the Bergey Excel‐S, with an average capacity factor of 4%.
• The cause of the overall poor performance of installed small wind energy systems is not known with complete certainty. Known contributing factors include inverter synchronization/standby time, higher than expected site turbulence, and lower than expected average wind speeds.
• Of the 19 systems analyzed, 16 have been inspected by Cadmus. Of these 16, only 6 were found to meet the estimated 10% capacity factor requirement of the SRI program, based on Cadmus’ site survey and use of the SWEET modeling tool.

-Bill

Windsun

Re: Wind grid tie inverter

..The smallest I have seen is the SMA 700 watt WindBoy for around $1,500 (not listed on our host's website--but the can probably get them if you ask). ...

The Windy Boy in some version has been listed by SMA for years, but availability has always been poor to nil, so we gave up on listing it.

booboo

Re: Wind grid tie inverter

Sounds like it is not really possible.