7 research outputs found
Electrolyzer Scheduling for Nordic FCR Services
The cost competitiveness of green hydrogen production via electrolysis
presents a significant challenge for its large-scale adoption. One potential
solution to make electrolyzers profitable is to diversify their products and
participate in various markets, generating additional revenue streams.
Electrolyzers can be utilized as flexible loads and participate in various
frequency-supporting ancillary service markets by adjusting their operating set
points. This paper develops a mixed-integer linear model, deriving an optimal
scheduling strategy for an electrolyzer providing Frequency Containment Reserve
(FCR) services in the Nordic synchronous region. Depending on the hydrogen
price and demand, results show that the provision of various FCR services,
particularly those for critical frequency conditions (FCR-D), could
significantly increase the profit of the electrolyzer.Comment: Accepted for IEEE SmartGridComm 202
A Conic Model for Electrolyzer Scheduling
The hydrogen production curve of the electrolyzer describes the non-linear
and non-convex relationship between its power consumption and hydrogen
production. An accurate representation of this curve is essential for the
optimal scheduling of the electrolyzer. The current state-of-the-art approach
is based on piece-wise linear approximation, which requires binary variables
and does not scale well for large-scale problems. To overcome this barrier, we
propose two models, both built upon convex relaxations of the hydrogen
production curve. The first one is a linear relaxation of the piece-wise linear
approximation, while the second one is a conic relaxation of a quadratic
approximation. Both relaxations are exact under prevalent operating conditions.
We prove this mathematically for the conic relaxation. Using a realistic case
study, we show that the conic model, in comparison to the other models,
provides a satisfactory trade-off between computational complexity and solution
accuracy for large-scale problems
Flexibility of Integrated Power and Gas Systems: Modeling and Solution Choices Matter
Due to their slow gas flow dynamics, natural gas pipelines function as
short-term storage, the so-called \textit{linepack}. By efficiently utilizing
linepack, the natural gas system can provide flexibility to the power system
through the flexible operation of gas-fired power plants. This requires
accurately representing the gas flow physics governed by partial differential
equations. Although several modeling and solution choices have been proposed in
the literature, their impact on the flexibility provision of gas networks to
power systems has not been thoroughly analyzed and compared. This paper bridges
this gap by first developing a unified framework. We harmonize existing
approaches and demonstrate their derivation from and application to the partial
differential equations. Secondly, based on the proposed framework, we
numerically analyze the implications of various modeling and solution choices
on the flexibility provision from gas networks to power systems. One key
conclusion is that relaxation-based approaches allow charging and discharging
the linepack at physically infeasible high rates, ultimately overestimating the
flexibility
Optimization of Hybrid Power Plants: When Is a Detailed Electrolyzer Model Necessary?
Hybrid power plants comprising renewable power sources and electrolyzers are
envisioned to play a key role in accelerating the transition towards
decarbonization. It is common in the current literature to use simplified
operational models for electrolyzers. It is still an open question whether this
is a good practice, and if not, when a more detailed operational model is
necessary. This paper answers it by assessing the impact of adding different
levels of electrolyzer details, i.e., physics and operational constraints, to
the optimal dispatch problem of a hybrid power plant in the day-ahead time
stage. Our focus lies on the number of operating states (on, off, standby) as
well as the number of linearization segments used for approximating the
non-linear hydrogen production curve. For that, we develop several
mixed-integer linear models, each representing a different level of operational
details. We conduct a thorough comparative ex-post performance analysis under
different price conditions, wind farm capacities, and minimum hydrogen demand
requirements, and discuss under which operational circumstances a detailed
model is necessary. In particular, we provide a case under which a simplified
model, compared to a detailed one, results in a decrease in profit of 1.8% and
hydrogen production of 13.5% over a year. The key lesson learned is that a
detailed model potentially earns a higher profit in circumstances under which
the electrolyzer operates with partial loading. This could be the case for a
certain range of electricity and hydrogen prices, or limited wind power
availability. The detailed model also provides a better estimation of true
hydrogen production, facilitating the logistics required.Comment: Accepted for IEEE PES PowerTech 202