[RE-wrenches] GT with batteries in Calif.

Phil Undercuffler solarphil at gmail.com
Thu Jul 3 14:48:13 PDT 2014


Hi all,

The kW is correct, although it does run counter to most every definition of
a battery we're used to -- I guess you could say the vectors of physics and
policy are not always aligned.

The entire "kW" issue ties back to the self-generation incentive program
(SGIP), which currently pays about $1.80/Watt for energy storage.  I had
many long discussions this past year with policymakers and the program
administrators at the CCSE, and they really helped me understand the
reasons behind how energy storage came to be defined in kW, not kWh. The
Governor and other policymakers want to achieve reduced greenhouse gas
emissions, and in order to do that we need a more efficient grid --
renewables are now as cheap or cheaper than traditional generation, but due
to the variability (of loads and generation) and increased reliance on
natural gas GHG emissions are trending up, not down.  We can't generate our
way out of this cycle; storage is a key tool in moving to the next stage,
and the policymakers wanted to provide tools to increase the adoption of
storage on the grid.

In the sometimes convoluted way that policy sometimes takes, the best tool
they had available was SGIP, so they added Advanced Energy Storage to SGIP.
 Since SGIP is a "generator" program, in order to make this work they had
to define AES in terms of a generator.  Therefore, the battery is rated in
terms of the capacity that it can provide to (or the capacity that it
replaces from) the grid, for a period of time, which is defined as a two
hour period.

To turn that into actual (if rough) numbers, let's say you have a 200 AH
battery. The 200 AH is only at the 100 hour rate, so you need a
manufacturer that provides the one or two hour rate, where it's good for
103 AH, or 4.944 kWh per string to total exhaustion.  You don't want to
flatline the battery, so let's use  80% DOD, which would be 3.95 kWh per
string.  You need to be able to provide this capacity for two hours, so cut
that number in half for 1.97 kWh rated capacity.  Per the SGIP handbook, "The
purpose of the SGIP is to contribute to Greenhouse Gas (GHG) emission
reductions, demand reductions and reduced customer electricity purchases,
resulting in the electric system reliability through improved transmission
and distribution system utilization; as well as market transformation for
distributed energy resource (DER) technologies."  Put two strings of that
battery together with a ~4kW battery based inverter and a program that
meets that purpose, and you're off to the races.

If the inverter/battery is 10kW or less per this definition, there are no
metering requirements.  For systems larger than 10kW, or if you wish to use
the metering requirements of systems larger than 10kW you can meter the
load, the generation and the total energy flow at the PCC, and the utility
can't charge you more than $600 for all of this metering.  There's a
writeup on the OutBack website on how to use two meters plus a NEM meter to
do this.

Hope this helps,

Phil Undercuffler


On Thu, Jul 3, 2014 at 8:56 AM, Bruce Erickson <bruce at mendocinosolar.com>
wrote:

> Hi Wrenches,
>
> Here is the only info I've seen regarding NEM with batteries in
> California. It's a May 15 news post from CALSEIA, which Brad allowed me to
> post here.
>
> One problem clearly is defining the categories, because what is a storage
> system "larger than 10 kW"? Seems like there's an "h" factor missing.
>
> Even for category 1, "internal metering devices" could be a Mate3 for
> instance, but how can a Mate report directly to the utility?
>
> This whole thing is a mess, IMO. I'm still curious, are any other
> California Wrenches dealing with utility NEM departments for systems with
> storage in the last few months, and what has been your experience?
>
> Official CALSEIA Membership AnnouncementEmail not displaying correctly?
> View it in your browser
> <http://us4.campaign-archive2.com/?u=a0487692bb2e2f280211c4298&id=24ddc73bfb&e=01b7850b6c>
> .*News Alert* Dear CALSEIA Members,
>
> Earlier today, the California Public Utilities Commission voted to
> finalize the decision on the interconnection of solar systems paired with
> energy storage systems under net metering.
>
> First, and most importantly, the decision restores the ability of solar
> systems paired with storage to qualify under the standard net metering
> tariff. For the past year, utilities had refused to connect systems with
> batteries under NEM.
>
> However, the decision includes new requirements. It effectively creates
> three categories of systems.
>
> 1. Storage systems smaller than 10 kW maximum output power can be paired
> with any size solar system and do not have to install a second meter. The
> associated solar systems will have to report system production to the
> utility using internal metering devices to make sure NEM credits are only
> going to solar output and not battery output.
>
> 2. Storage systems larger than 10 kW with maximum power output less than
> 150% of solar system capacity will have to install a second meter at a cost
> of up to $600 to make sure NEM credits are only going to solar output and
> not battery output.
>
> 3. Storage systems larger than 10 kW with maximum power output more than
> 150% of solar system capacity will be on the NEM-MT tariff rather than the
> standard NEM tariff. In addition to the $600 meter, they will have to pay
> an application fee of $800 and could potentially be subject to standby
> charges and distribution system studies and upgrades. They will still get
> net metering credits for electricity they put on the grid from the solar
> system.
>
> These limits are an improvement over the limits that were in the proposed
> decision. The Commission did not include all of CALSEIA's recommendations,
> but it included some significant movement in the right direction.
>
>    - The threshold between the categories above was changed from 100% to
>    150% of the paired generator’s output power.
>    - A kWh storage limit of the storage system was eliminated (how many
>    hours worth of electricity can be stored).
>    - A de-rate formula that would have potentially reduced the value of
>    NEM credits was abandoned.
>    - Utilities must refund application fees that were illegally collected
>    over the past year.
>
> I would be happy to answer any questions you have with regard to how the
> conditions in the decision would apply to specific system configurations.
>
> Thank you for your help in achieving this decision.
>
>
> Brad Heavner
> Policy Director, CALSEIAwww.calseia.org
> <http://calseia.us4.list-manage1.com/track/click?u=a0487692bb2e2f280211c4298&id=a0f6b695c3&e=01b7850b6c>*Copyright
> © 2014 CALSEIA, All rights reserved.*
>
>
> *Bruce Erickson*
> Mendocino Solar Service
> PO Box 1252
> Mendocino, CA 95460
> 707-937-1701
> 707-937-1741 fax
> bruce at mendocinosolar.com
>
> *Celebrating 20 Years in Solar!* 1994-2014
>
>
>
>
>
>
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