[RE-wrenches] Large Off Grid Inverter?

[Ray]

I appreciate everyone's replies so far. First, we already have an 
electronic soft start control, it just needs to be reprogrammed to 
reduce the starting surge more.  Second, we are way beyond 48v land.  We 
are in the realm of commercial scale inverters of at least 500 kW to 1.5 
MW.  They will be running at 600 vdc min and probably 1500 v range.  
Output is 480v 3 phase.

When I mentioned SMA, it was not their Sunny Island, its their larger 
scale Grid tie equipment syncing to a generator.

https://www.sma-america.com/industrial-systems/pv-diesel-hybrid-applications.html

Most of the inverters we are looking at are primarily being used with 
batteries for peak shaving to reduce demand charges on grid. Some, such 
as Dynapower can work off grid, but I am not finding evidence that 
anyone has much real life field experience off grid.  Princeton Power 
has their 100 kW inverter in Haiti forming a micro-grid, but I have very 
few details at the moment.

Even if your experience with these large battery inverters is just on 
grid, I'd love to hear about it. Offline is fine, if its not all good news.

Thanks,

Ray Walters

Remote Solar


On 4/26/18 5:23 PM, Kevin Pegg wrote:
> Hello Ray,
>
> I have a couple 60/100 kW SMA Sunny Island systems out there, systems with 100 kW generators, 400 kWh battery banks and generally token renewable inputs. I feel with this configuration we close maxing out what can be done with 48VDC.
>
> Getting into the MW scale scares me to be honest. I think that will be well beyond what can be handled at 48VDC and is well beyond capacity of the SMA systems. Really need to look into higher DC voltages to handle this kind of current.
>
> If this was my client I would first look to the loads and see if there are any alternatives to the 250 HP motor. I have learned there are often massive levels of engineering overkill in the industrial world. What is the duty cycle of that motor, what does it do, etc? Would they be better to go directly diesel for that?
>
> In terms of system designs I'd investigate a direct diesel/PV interface skipping battery storage. Perhaps a group of 250 kW synchronized generators that can ramp up/down based on demand. Perhaps similar tech to what Tesla is doing in Australia.
>
> Kevin
>
>
> -----Original Message-----
> From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Ray
> Sent: April-25-18 12:37 PM
> To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
> Subject: [RE-wrenches] Large Off Grid Inverter?
>
> Greetings Fellow Wrenches;
>
> We are consulting on a power system for a large off grid facility that is currently operating on a 1500 kW gen set.  The loads are enormous for normal off grid: in the neighborhood of 600 amps continuous at 480 v 3 phase.  Surges are close to 2000 amps, but we are working on control programming to bring that number down substantially.  That is due primarily to a 250 Hp motor start. (that's not a typo!). EPA and local regulations are dictating that the current generator be retired in the near future.  Grid power is a possibility, but we need to offer a viable off grid option as well.
>
> My question to the group: does anyone have real off grid experience with large format battery based inverters?   I've heard of some micro-grid systems running in Haiti on Princeton Power inverters, and Dynapower has a 250 kW inverter that has a "grid forming" mode.  As we all know, it is easier to make claims in spec sheets than to deliver hard motor starting power in a remote location.  We need proven products, with a track record of reliability.
>
> We are considering SMA type systems that use AC coupled PV to offset fuel consumption of a generator, but those seem dependent on the generator to maintain the stability of the micro grid during hard starting loads. Ideally we would want to reduce the generator run time to under 200 hrs/ yr and reduce its size to 500 kW.  We have excellent solar resources year round, and the possibility of  limiting operations during cloudy weather to meet these goals.
>
> Thanks,
>
> Ray Walters
>
> Remote Solar
>
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