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-boun...@lists.re-wrenches.org] On Behalf
Of Ray
Sent: April-25-18 12:37 PM
To: RE-wrenches <re-wrenches@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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