TIME SERIES PLOT
Graph 1: Time-series plot of wind-hydrogen system
The time series plot, Graph 1, provides valuable insights into how the system operates over time. It allows observation of fluctuations in both demand and generation, from wind turbines and hydrogen generators. The system's primary focus is on serving the electric demand/load, which is mostly fulfilled by the wind turbines. However, during periods of low wind or high demand, the hydrogen generator steps in to meet the demand.
When wind resources are abundant and there's excess energy generated, an electrolyser is utilized to produce hydrogen; from the graph, it can be seen that it runs steadily. The produced hydrogen is then stored in the hydrogen tank for later use (here the hydrogen generator). The graph allows tracking of variation in hydrogen levels, showing a decrease when the hydrogen generator is active due to its consumption during the generation process.
Analyses for various scenarios have been conducted. In Case 1, elucidated in Methodology, the Levelized Cost of Hydrogen (LCOH) was examined across different locations.
Graph 2 indicates the annual wind speed and Levelized Cost of Hydrogen (LCOH) across various diesel-dependent communities in Greenland. For the simulation, the same wind turbine model and hydrogen load assess the impact of average wind speed over LCOH.
Graph 2 exhibits an inverse relationship between LCOH and wind speed. The highest wind speed, 8.08 m/s, correlates with the lowest LCOH of 3.14$/kg. According to the Hydrogen Council[18], an LCOH below 6.5$/kg shows an optimum value and most value falls within this range. For further analysis (simulation), 4 locations with the highest wind speed/lowest LCOH were filtered.
Four specific locations – Paamiut, Qaqortoq, Nanortalik, and Ittoqqortoormiit – were selected for further simulations based on the filtering criteria
Graph 2: (a) Wind speed and (b) LCOH calculated across different locations.
In the second simulation phase, parameters were adjusted; the hydrogen load was excluded, and an electric load was introduced. This modification was necessary as a hydrogen generator was incorporated into the system, converting hydrogen into electricity. The electric load for each location was calculated based on the diesel consumption of that location. The optimal number of turbines for each location was determined through an optimization process considering both the local demand and the capacity of the wind turbines available
Table 3: HOMER optimisation results
The optimization table in HOMER provides valuable data regarding the generation and consumption patterns of our system components. Within the electrical generation column, wind turbines are the primary contributors, accounting for approximately 95% of electricity generation, while the hydrogen generator contributes around 5% in all scenarios.
Of the total generated electricity, 75% is allocated for community consumption (electric load), while the remaining 25% powers the electrolyzer for hydrogen production.
The economic variables, including LCOE, NPC, Operating cost, and CAPEX, were thoroughly analyzed at the selected locations. Notably, Ittoqqortoormiit displayed the lowest LCOE at $0.13/kWh, attributed to its high wind speeds. However, this figure surpasses the International Renewable Energy Agency (IRENA)[19] benchmark of $0.033/kWh, suggesting potential feasibility concerns. Nonetheless, when compared to Greenland's average LCOE[20] for onshore wind projects, which stands at $0.25/kWh, the values remain within an optimal range.
Table 4: Project economics for four locations
To compare the economic variables to current alternatives, further simulations were conducted in different configurations: Wind-Hydrogen (current system), Wind-Battery, Wind-Diesel, and Diesel only.
Graph 3: LCOE for different configuration
Graph 4: CAPEX for different configuration
Graph 3 illustrates that the LCOE values for the Wind-Hydrogen system are lower than those for the Wind-Diesel/Diesel system but higher than those for the Wind-Battery system. However, it is essential to note that the Capital Expenditure (CAPEX) for the Wind-Hydrogen system is the highest among all configurations due to its technological investment.
To contextualize the CAPEX/kWh values, they were compared to a reference value of $1500/kWh for a wind project of similar scale, as recommended by the National Renewable Energy Laboratory (NREL)[21].
Across all locations, the values exceeded this reference point. Particularly Nanortalik, having the lowest wind resource, exhibited the most significant deviation from the reference value.
Graph 5: Comparison of LCOE with reference value
Comparison and Validation of Results
The simulations results conducted using Aspen Plus and HOMER indicated a similar level of hydrogen production. This alignment serves as a confirmation that both the models, utilized within HOMER and Aspen Plus, are accurately configured, as they consistently produce matching results.
Table 5: Comparison and Validation of Results from HOMER and Aspen Plus
Electrolyzer Consumption
Product H2 from Aspen Plus
Product H2 from HOMER
Grow Your Vision
REFERENCES:
[18] Hydrogen Council, ''Hydrogen Insights 2023 December Update'', 2023. [Online]. Available: https://hydrogencouncil.com/en/hydrogen-insights-2023-december-update/ (Accessed on: 20 March 2024)
[19] International Renewable Energy Agency, ''Renewable Power Generation Costs in 2022'', 2023. [Online] Available: https://www.irena.org/Publications/2023/Aug/Renewable-Power-Generation-Costs-in-2022 (Accessed on: 23 March 2024)
[20] International Renewable Energy Agency, ''Global Atlas for Renewable Energy'', 2024, Available: https://globalatlas.irena.org/workspace (Accessed on: 2 April 2024)
[21] National Renewable Energy Laboratory, ''2021 Cost of Wind Energy Review'', 2022, Available: https://www.nrel.gov/docs/fy23osti/84774.pdf (Accessed on: 2 April 2024)
[22] Jose Pedro, ''Wind Energy Utilization in Arctic Climate – RAMCO 2.3'', 2016, Available: http://www.diva-portal.org/smash/get/diva2:1046990/FULLTEXT01.pdf (Accessed on: 20 March 2024)
[23] Daniel Chade, et. al, ''Feasibility study of wind-to-hydrogen system for Arctic remote locations-Grimsey island case study'', 2015, Available: https://doi.org/10.1016/j.renene.2014.11.023 (Accessed on: 15 March 2024)
[24] Monica Sanchez, et.al, ''Aspen Plus model of an alkaline electrolysis system for hydrogen production'', 2020, Available: https://doi.org/10.1016/j.ijhydene.2019.12.027 (Accessed on: 20 February 2024)