Overcoming water-related challenges.
An electrolyzer of 100 MW capacity consumes roughly 500 tons of water per day (tpd) and produces roughly 50 tpd of hydrogen. If the system is water-cooled, the water required will be doubled. Thus a large hydrogen project, say 30,000 MW, will require at least 150,000 tpd of pure water. This is approximately the water demand of a city with a population between 500,000 to one million people.
Locations ideal for solar energy farms won’t necessarily have a readily available water source.
It’s unlikely that new water consumption of this scale will be accepted at many inland locations. But many inland locations (i.e. the southwestern United States, central and western Australia, North Africa, or the high plains of South America) are ideal for solar energy production. Since solar energy will often be paired with hydrogen production, water supply is a key issue to address.
This is why we must look to the sea.
The sheer magnitude of water required for hydrogen production will be most readily available from the ocean. Seawater desalination plants can provide pure water for electrolysis at whatever scale is required. And because of that, we frequently incorporate this option into our clients’ plans.
In cases where the renewable energy source is not co-located with the electrolyzer, trade-off studies will be needed to determine the optimum location for the electrolyzer. Which has a better cost-benefit? An electrolyzer located inland, with water transported from the ocean? Or locating the electrolyzer near the ocean, while accounting for the renewable energy lost during transmission from the energy source.
What sources can be used when seawater simply isn’t available?
When seawater desalination is not available, large-scale hydrogen production will be recognized as a major new consumptive water use. One that may need to be weighed against other uses. Consequently, many regions, even those not traditionally considered water-stressed such as Northern Europe, may turn to large-scale wastewater reuse to meet this new water demand.
We know this to be true since we recently assisted a large city in Northern Europe develop plans to create a major new industrial water supply using wastewater as the raw water source. This concept is used increasingly in major cities around the globe. In Queensland AU, Worley was part of a 2.5 billion dollar wastewater reuse and transport project capable of supporting both industrial users and the water supply for metropolitan Brisbane’s 2 million people.
Out with the old to make room for the new.
As evaporatively cooled coal power plants become obsolete, the large amount of water they consume can be reallocated. Freeing up that water supply will permit new electrolytic hydrogen production in renewable energy-rich areas, which are currently considered water constrained. For instance, a water-cooled 2000 MW coal-fired power plant consumes around 100,000 tons of water per day. If the coal power plant is closed and its water offtake rights become available for hydrogen production, there will be enough water to support at least 18,000 MW of electrolysis.
Much of the water consumed in electrolysis can be recovered if hydrogen is used in processes that permit steam recovery. Such processes may include hydrogen-fueled ore smelters and fuel cells.
Fuel cells offer the potential to simultaneously produce power, heat, and water. In severely water-constrained locations (such as the high plains of Chile), by-product water from industrial use of hydrogen for power generation and metal smelting, will prove especially useful.
Hydrogen production also yields large quantities of a potentially valuable by-product, oxygen. For each megawatt of electrolyzer power, approximately 3.9 tons per day of oxygen is released. This poses an enormous opportunity for the development of innovative oxygen-dependent applications including chemicals processing, waste treatment, and aquaculture.
The supply of vital process reagents is a key logistical problem.
A lack of process reagents may potentially affect hydrogen projects relying on offshore and onshore wind energy fields. Remote solar power fields coupled with hydrogen projects may experience similar logistical constraints.
However, this problem can be overcome by producing reagents locally. When there is a large supply of sea water, electricity, hydrogen, and oxygen it is possible to produce most typical water treatment reagents on site such as:
- Sodium chloride from sea salt
- Sodium hydroxide via chloralkali process
- Chlorine gas and other chlorine products via chloralkali process
- Hydrochloric acid combustion of chlorine with hydrogen
- Oxygen from electrolyzer by-product, or air plus electricity
- Ozone from oxygen and electricity
Hydrogen storage and handling poses another logistical challenge.
Hydrogen requires liquefaction for storage and transport. Some of the logistics associated with this can be overcome through a complementary technology, ammonia production.
Much of the world’s food supply depends upon fertilizer made from synthetic ammonia, manufactured using fossil fuel. However, ammonia is an efficient transport vector for hydrogen, because hydrogen is much harder to liquefy and transport than ammonia, and ammonia has a very high hydrogen density.
Ammonia can be used as a fuel for combustion systems without requiring a hydrogen extraction process. Ammonia plant wastewater must also be managed.
What are the core water decisions our clients face?
Water availability is a deciding factor for any hydrogen project but there are many other details to consider. And it’s best to consider these trade-offs early, during source and treatment selection.
Facility design factors add to the challenge. These might include source water, pretreatment, heat integration, redundancy, peak demand flows, and storage.
You also need to make environmental design considerations and consider local weather at your site. Seasonal changes to water temperature will impact your treatment approach. Water salinity and water quality changes whether seasonal, weather related, or tidal can all have an impact on water treatment as well.
We're here to help you solve all these water challenges and more.
Early water management planning will ensure smooth sailing throughout your hydrogen project journey. We provide total water management solutions, from source selection, permitting, and treatment, to operations and maintenance, through to waste management. If you are facing water challenges on your hydrogen project we’re here to help. Reach out to our global water team at WET@advisian.com.