Page 36 - Energize September 2022

VIEWS AND OPINION

Why not aggregate and optimise PVs,

batteries and EVs?

By Fereidoon Sioshansi, Menlo Energy Economics

n attractive opportunity has Such customers can avoid buying
emerged with so many homes expensive power during periods when
Aand businesses installing solar the rates are 56 US cents/kWh on the
panels on their roofs – with many EV2-A schedule by powering their home
pairing/backing them up with batteries. with the battery and be paid $2 per kWh
At the same time, the uptake of electric for exporting power from the battery
vehicles (EVs) is accelerating in many key – and potentially from the EV – to the
markets. grid.
EVs can be thought of as massive The idea sounds compelling in
batteries on wheels. Instead of allowing theory. But will it pan out in practice?
each customer or EV owner to generate, Using data from his own solar plus
consume and store energy individually storage at his house, Faruqui examines
and haphazardly – which is currently what happens on a mild vs. an extremely
the case – why not aggregate them and hot day.
optimise the entire portfolio’s assets? On 29 June 2022, a mild sunny day,
The technologies and tools to do this are his 8 kW solar system produced
mostly available. It is merely a matter of 49,41 kWh while the house consumed Fereidoon Sioshansi
aggregating and managing, which can be 23,32 kWh, with the balance exported
achieved through software and artificial to the grid. Faruqui also has a battery customers. The shortages occurred
intelligence (AI) – at least on paper. rated at 9,8 kWh and a Tesla EV, which during the evening ramping period, the
In a 14 July 2022 PV Magazine means he can store some of the excess dreaded neck of the “duck curve.”
article titled Can homes with solar plus generation for later use – and potentially Faruqui notes that during such
storage act as virtual power plants? discharge to the grid given sufficient episodes, “… Homes such as mine did not
Ahmad Faruqui explores how this can incentives and the necessary gadgets. have much of a surplus to send to the
be done using his own solar generation, On most sunny days, the house was grid. I was actually concerned whether I
consumption and storage profile. self-sufficient until almost midnight. He had enough to keep my lights on in case
Faruqui notes that for a customer could have availed himself of the VPP the grid lost power. Why would I have
on Pacific Gas & Electric Company’s mode and come out ahead. exported power to the grid on either
(PG&E) EV2-A tariff, “… the off-peak Needless to say, aggregating day?”
period begins at midnight and runs to thousands of such solar plus battery On 14 August, his system generated
15h00. The peak period begins at 16h00 systems represent a significant untapped 32,79 kWh while the house consumed
and runs to 21h00. All other hours are resource. Which explains why Customer 63,12 kWh – it was a very hot day
the mid-peak period. When the sun is Choice Aggregators such as MCE are indeed. As seen in the accompanying
charging the battery in the morning, the enticing customers with solar plus graph, “… around 5 pm, the battery
house is buying power from the grid at batteries to enroll in programmes to do was unable to keep up with the
the lowest rate. When the battery begins precisely what Faruqui refers to, namely consumption…” which meant that
discharging at 16h00, the house avoids allowing the operation of their assets to Faruqui was “… importing power from
buying power at the most expensive rate. be optimised by a third party. the grid. This would not have been the
Typically, customers don’t let the battery But what about those really hot days time to release whatever battery power
discharge totally. They keep a certain when the California Independent System I had remaining to the grid, regardless of
amount of battery power in reserve, such Operator’s (CAISO) network is stretched the price being offered to me.”
as 30%, to guard against power outages.” to the limit? Can the customers with A similar pattern was encountered on
With California’s notorious “duck solar + storage come the rescue? the following day, 15 August, another hot
curve” and chronic shortages during During an extreme heat wave on 14 day, when his system generated 34,76 kWh
extreme heat waves, why not turn homes and 15 August 2020, CAISO encountered while the house consumed 60,55 kWh.
with solar plus storage into virtual power a serious emergency resulting in outages Faruqui notes, “On neither day would I
plants (VPPs)? affecting hundreds of thousands of have wanted to export any power from

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