The Integration of Fluctuating renewable energy using energy storage

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Energy storage is often portrayed as an ideal solution for the integration of fluctuating
renewable energy (RE) due to the flexibility it creates. However, there is uncertainty
surrounding energy storage in terms of the technologies that currently exist, the additional RE
it enables, and its role in modern electricity markets. These uncertainties have hampered the
deployment of large‐scale energy storage and hence, this research examined these concerns.
This research began by identifying the most feasible energy storage technology available for
the integration of fluctuating RE, specifically for Ireland. Due to its technical maturity and
large‐scale capacities, pumped hydroelectric energy storage (PHES) was deemed the most
viable technology, but the literature outlined a lack of suitable sites for its construction.
Therefore, a new software tool was developed in this study to search for suitable PHES sites,
which was then applied to two counties in Ireland. The results indicate that these two counties
alone have over 15 sites suitable for freshwater PHES, which in some cases could be twice as
large as Ireland’s only existing PHES facility. Hence, the next stage of this research assessed the
benefits of constructing large‐scale energy storage in Ireland. To do this, a model of the Irish
energy system was needed and so a review of 68 existing energy tools was completed. From
this review, EnergyPLAN was chosen and subsequently it was used to simulate various
capacities of wind power and PHES on the 2020 Irish energy system. The results reveal that
PHES could technically integrate up to 100% penetrations of fluctuating RE if very large
capacities were used under certain operating strategies. However, the economic assessment
indicates that this would cost more than the reference 2020 scenario. In addition, alternatives
were identified which could offer similar savings as PHES, while also being more robust to
changes in fuel prices, interest rates, and annual wind generation, but they did consume more
fossil fuels. Finally, a new practical operating strategy was created for energy storage while
operating in a wholesale electricity market. Results indicate that approximately 97% of the
maximum feasible profits are achievable. However, the annual profit could vary by more than
50% and hence, energy storage will need more profit stability to become feasible for investors.
To summarise, this work concludes that PHES is the most promising energy storage technology
for integrating fluctuating RE. More sites do exist than previously expected and constructing
them will enable higher penetrations of fluctuating RE. However, based on predicted 2020
costs, using PHES is more expensive than the reference scenario and alternatives could be
more cost‐effective, which really need further analysis. Finally, if energy storage is required,
electricity markets will need to create more certainty surrounding their potential profits.