Water access and the risk of scarcity is a growing concern for the energy industry as the climate changes. But while the hydrogen sector remains confident that will not push the dial on project economics, it is investigating alternative streams to freshwater for future hydrogen production.

An electrolyser requires at least 9kg of water for every kilogram of hydrogen produced, while steam methane reformation consumes a minimum of 4.5kg per kilogram of hydrogen. To prevent clogging by particulates, the water must also be as free of salt, minerals, organic matter and other contaminants as possible.

A letter to the non-profit American Chemical Society notes that, while 2.3gt of green hydrogen would require 20.5gt of freshwater, this is still only two-thirds of the amount of freshwater used in fossil fuel-related uses.

“Risk of water scarcity is certainly one of the factors that developers are looking into when it comes to cost-benefit analysis of a given location, but it is not necessarily a determining factor for whether a project goes ahead,” Tracy London, partner at law firm Bracewell, tells Hydrogen Economist.

9kg — Water required to produce 1kg green hydrogen

She adds that one of the advantages of siting hydrogen production projects at the site of former coal-fired power plants—such as Moorburg in Germany or Sines in Portugal—is the presence of an existing water source that can be repurposed for the new plant.

Jack Brouwer, director of the Clean Energy Institute at University of California Irvine, agrees that, while water presents “a geospatial challenge”, it can be accounted for within project development. “Some of the places where we have the best solar and wind resources—like the north of the Los Angeles basin—we do not have access to water. So the question is, do we build transmission lines from renewable energy to locations where we do have water, or do we build new water pipes to deliver the water to electrolysers co-located with renewables?”

He adds that, in the US, it is “very difficult to permit high-voltage transmission lines”. This has driven interest in transporting renewable energy stored as green hydrogen via pipelines, which is “less efficient, but easier to permit”.

Drying up

However, the changing climate presents a major risk for water access, particularly in regions already experiencing drought. The UN Intergovernmental Panel on Climate Change’s most recent assessment report notes that there is “medium confidence” that droughts have caused global thermoelectric and hydropower production to fall by 4–5pc compared to average utilisation rates since the 1980s, with some regions severely impacted. The organisation notes that many mitigation measures—such as CCS, bioenergy, and afforestation and reforestation—can have a high-water footprint, and that greater penetration of renewables in the energy mix could reduce the water intensity of the sector—although hydrogen is not mentioned in either case.

“In California, we are seeing an increase in water scarcity as a result of worsening droughts—this means less water for hydropower, less for pumped hydro storage,” Brouwer says. “We do not use a lot of water for electrolysis at the moment, but it is a risk factor. In addition, these dry conditions lead to an increase in fire risk from electrical lines, so there are a lot of compounding issues that will make wastewater and saltwater quite attractive for making green hydrogen in the future.”

Water, water everywhere

Electrolysis of treated wastewater could be an option for projects co-located with industrial parks that already use significant volumes of water or that are located near demand centres.

A working group led by water industry body UK Water Industry Research (UKWIR), in collaboration with engineering firm Stantec, consultancy Ikigai Capital and Scotland’s Heriot Watt University, has been set up this month to assess the feasibility of scaling hydrogen production in relation to water consumption in the UK and Ireland. The team will also evaluate potential feedstock for hydrogen production from wastewater-derived bioenergy.

“UK water companies are committed to achieving net-zero carbon emissions and are keen to understand the degree to which we can be both producers and consumers of hydrogen from renewable sources,” says Dan Green, head of sustainability at utility Wessex Water and UKWIR’s programme lead.

“We are also aware that conventional hydrogen production requires a lot of clean water—so we want to quantify the potential impacts of larger scale hydrogen production on water resources,” he adds.

Seawater presents another avenue for abundant water supply. Researchers at universities in the US, China and Australia are investigating methods of direct electrolysis of seawater—although this may not be the biggest hurdle to offshore or coastal projects. While water desalination is costly, the process is estimated to add less than 1¢/kg of hydrogen produced.

Offshore green hydrogen projects are more likely to stumble when it comes to cost of electricity. “In terms of total systems cost, offshore wind is one of the most expensive renewable technologies we can invest in for a largescale project,” says Juan Gea Bermudez, energy policy analyst at the European Commission and co-author of analysis comparing offshore and onshore electrolysis published in the Energy Policy journal.

A pipeline from an offshore green hydrogen hub would cost less than an electricity cable to shore but may present less value overall to an integrated energy system, he adds. Electricity cables can provide valuable flexibility to the system, but while excess heat from onshore electrolysis can be processed into district heating networks, this is wasted offshore.

The maturity of the offshore wind industry also presents a challenge. The US has recently ramped up its efforts to install the first wave of commercial offshore windfarms on both coasts. “In California, we lifted the moratorium on offshore wind development just last year. Unlike countries along the North Sea, we are only just starting to issue permits for the first offshore windfarm. As we start to build more and more offshore wind, we will naturally need hydrogen as a vector of energy storage, but for the moment, the focus is on direct electricity transmission,” says Brouwer.

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Author: Polly Martin