Page 354 - A Comprehensive Guide to Solar Energy Systems

Chapter 17 • Energy and Carbon Intensities of Stored Solar Photovoltaic Energy 359

1. Flexible power generation and energy storage come with a cost. energy delivered from
storage has greater carbon and energetic intensities than energy delivered directly
from power generation technologies, and depending on the technology, the energy,
and carbon penalties for storage can be large.
2. The carbon intensity of solar PV plus most storage technologies including PHS, Li-ion,
and VrB are far lower than those of the uS grid. CAeS and PbA technologies yield
higher carbon intensities than the uS Grid. All storage technologies when paired with
solar PV trade higher energy intensities for lower carbon intensities.
3. not all storage technologies are created equal. PHS performs best and traditional PbA
batteries perform worst. CAeS trades low energy intensity for high carbon emissions
associated with combustion of natural gas. Li-ion and VrB perform best among
electrochemical storage solutions with Li-ion providing the lowest energy intensity
and VrB the lowest carbon intensity. Traditional PbA batteries perform poorly by
these metrics. Although they have low energy requirements for manufacture, their low
number of charge-discharge cycles leads to frequent replacement and a high-energy
intensity of 0.17.
4. The curtailment of solar resources provides flexibility with higher carbon and energy
costs in comparison to the implementation of energy storage technologies except for
PbA. This is due to the fact that solar PV panels are energetically intensive to produce.
Curtailing these resources forfeits energy that incurred high energetic costs. These
costs, in the case of PV, are greater than the cost of incorporating storage, especially
storage with low energy intensity values such as PHS and Li-ion.

energy storage and curtailment can provide the flexibility the power grid will require as
the fraction of variable resource supply increases. This chapter shows the benefits of using
systems-level energy intensity and carbon intensity analysis to compare performance of
flexible options for solar PV [28]. Policy makers and consumers that consider the effects
of deploying storage with solar PV can better identify environmentally sound solutions.

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