Abstract
Among the possible solutions for large-scale renewable energy storage, Power-to-Gas (P2G) and Compressed Air Energy Storage (CAES) appear very promising. In this work, P2G and an innovative type of CAES based on underwater storage volumes (UW-CAES) are compared from a techno-economic point of view, when applied in combination with a 48 MWe offshore wind power plant, selecting an appropriate location for both high productivity and favorable seabed depth. An optimization model is employed to study the system design and operation, maximizing the lifetime plant profitability, while considering differential installation and operation costs, market values of the products (i.e., hydrogen and electricity), and technological constraints. In the current economic and technological scenario, the resulting P2G system has a nominal power equivalent to about 10% of the wind park capacity, with a small hydrogen storage buffer. On the other hand, the compressor and the turbine of the UWCAES have a nominal power close to the full wind farm capacity, and large underwater compressed air tanks are required. Both options significantly impact the wind plant management but the most beneficial applications of the two systems are different: the P2G results in a compact and flexible unit, whereas the UW-CAES is able to exploit a higher average conversion efficiency (about 80% round-trip) against a much higher installed power and investment cost. Anyway, considering the current framework, the resulting economics are still inadequate, but their competitiveness can improve compatible with the expected evolution of energy markets in the next future.
Highlights
The global energy consumption has seen a huge increase in the last centuries, supported mainly by fossil fuels, but in the last decades new installations have largely moved towards renewable energy sources (RES)
The results of a set of cases simulated for the P2G and the UW-Compressed Air Energy Storage (CAES) systems are reported
The base-case simulation is performed with reference to 2019 wind profile from [29], but the influence of wind profiles is assessed by means of synthetic profiles functions with the same statistical distribution and persistence characteristics
Summary
The global energy consumption has seen a huge increase in the last centuries, supported mainly by fossil fuels, but in the last decades new installations have largely moved towards renewable energy sources (RES). RES installed capacity in the world has almost tripled with respect to the beginning of the 2000s, with a huge spread of wind and solar energy systems, especially for electricity generation. Problems related to increasing grid congestion, unpredictable energy transits in the grid in terms of either quantity or direction, and the fact that conventional plants are called upon to play a role in covering concentrated load peaks with a general efficiency loss must be faced. Energy storage systems can be allocated into the grid in order to store energy and release it when needed, contributing to the balancing of the grid and to making electricity more dispatchable [3,4]
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