IEEE Power & Energy Magazine - November/December 2021 - 41

A hybrid resource is flexible, typically with advanced
software and analytics, and it may provide a set of offers
for both energy and ancillary services.
level of performance. That includes battery state-of-charge
management, using probabilistic forecasts of RE components
with meaningful confidence intervals to supplement
a battery's energy during some periods, adjusting offers for
different periods to levels that can be confidently provided,
and so forth.
In principle, market operators could manage risk at a
system level and compensate market participants according
to their performance. In practice, this may mean that each
resource needs to perform at least as well as the forced outage
rate of a conventional one. By combining multiple technologies
with different performance attributes, it may be easier
for a hybrid resource to meet this threshold. This would
enable it to avoid penalties for nonperformance and qualify
as a provider of capacity and ancillary services when colocated
resource technologies could not. Quantifying the value
of such capabilities through time will heavily depend on the
assumptions of how various services will be valued and how
those values may change.
Hybrid resources come with inherent plasticity. Once you
allow for a mix of resources to interface with a system operator
as one holistic unit, it is natural to consider incremental
changes in a hybrid resource's technologies (e.g., adding
more PVs or batteries, upgrading software, and adding longduration
storage, other generation technologies, and even
load technologies within the hybrid resource). This flexibility,
reconfigurability, reprogrammability, and upgradeability
of hybrid resources creates option value that is valuable to
potential investors.
A market operator may change or otherwise redefine
a set of grid services. The adaptability of many hybrid
resources could enable an operator to quickly change its
offers and strategies to respond to alterations in services
and the value of various offerings in the marketplace. A
simple example would be a solar-plus-storage hybrid re -
source. The initial optimized design may have a relatively
small storage capacity that reflects the original marketplace.
However, grid transformation may result in longer
periods of system need in the future. As longer-duration
storage gets more valuable and batteries continue to get
cheaper, hybrid resources will respond by adding more
battery capacity.
The plasticity of hybrid resources should be valuable to
a system. To the extent that changes do not alter the electrical
properties at the point of interconnection (which
could require additional studies for reliability purposes),
it is logical to encourage such upgrades and modifications
november/december 2021
within hybrid resources. As long as market prices reflect a
system's need, the analytics of hybrid resources will identify
such opportunities. The concept of a hybrid resource as an
" energy and grid services factory " that can quickly innovate
and adapt to make essentially any sort of " more valuable
energy widget " is attractive. The question then becomes
whether this creates enough value to justify the extra investment
in flexibility and reconfigurability.
A related question is whether the power system models
used for network planning and operations will fully capture
the way hybrid resources will perform and respond to
AC Integration at Substation
* Separate Pad Mounts and Inverters
* Battery Building at substation
Battery
Charge
Battery
Discharge
(a)
DC Integration Before Inverter
* Same Pad Mounts dc/dc Converter for Storage
* Containers Distributed Throughout Site
Battery
Charge
Battery
Discharge
(b)
DC Generation
AC Output
figure 6. A comparison of available PV energy for battery
charging for (a) ac integration at a substation and (b) dc
integration before an inverter. (Source: NextEra Energy;
used with permission.)
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IEEE Power & Energy Magazine - November/December 2021

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