Benefiting from abundant reserves of natural gas, Saudi Arabia can readily produce hydrogen through processes like steam methane reforming (SMR), paving the way for immediate hydrogen city development while building up green hydrogen production capabilities, said Alberto Boretti, a New Zealand-based independent scientist.
Saudi Aramco can leverage these resources to offer low-cost hydrogen solutions, making the concept of a hydrogen city financially viable and immediately attractive, Boretti said in a letter first published by the International Journal of Hydrogen Energy.
Saudi Aramco recently announced its plans to set up a hydrogen hub in Jubail Industrial City, about 100 km north of Al Khobar along the Arabian Gulf coast. The complex could start operations by 2027.
Boretti told pv magazine that Al Khobar is unique for a number of reasons: natural gas production, average income levels, strategic location, vast solar and wind potential, regional expertise in oil and gas projects, economic diversification goals, and a focus on innovation and technology.
“Al Khobar Hydrogen City could be the first eco-city in the world to be powered by a mix of light blue, white, and green hydrogen, plus solar and wind electricity,” wrote Boretti, adding that natural gas should be used instead of hydrogen in the initial phases of the project. “The best ad-interim solution would be to build up wind and solar generating capacity and hydrogen production by electrolyzers.”
The missing electricity to match grid demand could be produced by combined-cycle gas turbine plants running on natural gas and hydrogen blends. The fuels needed for non-electric energy use could be produced using hydrogen and natural gas.
If generation from wind and solar is higher than grid demand, the electricity will power electrolyzers to produce hydrogen.
Boretti presented two possible configurations for a city with a 200 MW energy demand. This assumption serves as a starting point for estimating the needed capacity, but is subject to revision “as further studies are conducted and as the city develops.”
Possible configurations
The first configuration focuses solely on supplying the city with dispatchable renewable electricity. It involves the development of renewable energy generation capacity, such as wind and solar power, along with energy storage systems to ensure reliable electricity supply, even when renewable resources are intermittent. This configuration would require the city to install 1 GW of wind and solar capacity.
This second configuration extends beyond supplying dispatchable renewable electricity also to include additional renewable fuel production, specifically green hydrogen. The city would need 1.3 GW of solar and wind capacity and 73 MW of average renewable fuel power output.
“In addition to renewable energy generation and storage infrastructure, this configuration involves the development of additional hydrogen production facilities using electrolysis powered by renewable energy sources,” said Boretti. “Green hydrogen produced can then be used for various applications such as transportation, industry, and heating.”
The electrolysis capacity would be 997 MW in both cases, going down to 509 MW in case of parallel battery adoption.
“In the case of no adoption of batteries, the electrolysis capacity would indeed need to match the maximum excess renewable energy generation to utilize all available surplus energy for hydrogen production,” said Boretti. “However, in the case of cutting out outliers and adopting batteries to filter out oscillations of excess energy, the need for electrolysis capacity can be drastically reduced.”
The final amount of electrolysis capacity would depend on various factors, such as the efficiency of the storage system, the frequency and duration of excess generation events, and the desired level of hydrogen production.
In his model, Boretti said the hydrogen storage capacity should reach 145,000 MWh.
“The capacity of the hydrogen storage is generally dictated by the interannual and decadal variability more than the seasonal variability,” he said.
The scientist noted that inter-annual power generation oscillations are between +15% and – 15% for wind, and +6% and – 4% for solar.
“A mix of 50% wind and 50% solar installed capacity could deliver interannual fluctuations in the total energy produced every year between +18% and − 8%,” he said, adding that inter-annual variability may require a drastic increment in the hydrogen energy storage more than in the capacity of the electrolyzers.
Climate change is one of the factors increasing the seasonal, inter-annual, and decadal variability of wind and solar electricity production.
“Climate change could affect computations related to renewable energy production in many ways,” Boretti stated.
He noted a shift in long-term weather patterns and the growing frequency and intensity of extreme weather events.
“Unfortunately, this long-term variability of the resource is difficult to predict, as there is no certainty past occurrences will repeat in the future with perfect periodicity, and the exercise only gives a rough idea of the storage parameters,” he said.
Gulf projects
Saudi Arabia has also started constructing the world’s largest green hydrogen plant in Neom City, on the Red Sea. The plant, which is expected to be operational by 2026, will produce up to 600,000 kg of green hydrogen per day.
“A successful hydrogen city requires a comprehensive approach, combining technological innovation, supportive policies, public engagement, and collaboration among various stakeholders to create a sustainable and integrated urban environment,” said Boretti.
He claimed the study could lay the foundations for similar projects in other Gulf countries.
“By adapting the study’s methodologies, considering local factors such as geography, climate, energy demand, and regulatory environments, similar net-zero energy systems could be designed and implemented in other Gulf countries like the UAE, Qatar, Kuwait, Bahrain, and Oman,” he explained.
In its letter, Boretti assumes a 75% efficiency for hydrogen production and 55% for reusing hydrogen to produce electricity. An efficiency of 75% means that 75% of the electrical energy input is effectively converted into hydrogen gas, while the remaining 25% is lost as heat or other forms of energy.
A 55% efficiency range would mean that 55% of the energy stored in the hydrogen gas would be effectively converted into electrical energy, while the remaining 45% is lost as waste heat or other losses.
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