There’s no point ramping up hydrogen if other resource constraints are going to bring it to a halt. Here, Herib Blanco at IRENA summarises their research into how much water will be needed in the production of hydrogen through electrolysis (i.e. from water) and the costs involved. A wide range of analyses have been reviewed to calculate the amount of water used during the hydrogen production, and by the energy source used to power it (renewables or gas). Assuming the world is using over 70EJ of electrolytic hydrogen by 2050, the water consumption will be about 25 bcm. That is relatively small compared with the global figure of 2,800 bcm for agriculture (the largest consumer), 800 bcm for industrial uses, and 470 bcm for municipal uses. It would be equivalent to a developed country with 62 million inhabitants (400 m3/capita). Even in the most conservative case, where water desalination is used, the water cost (treatment, transport) would be less than 2% of the total hydrogen production cost and the energy consumption for water desalination would be only about 1% of the total energy needed for the hydrogen production. Blanco notes that the water footprint is very location-specific and depends on the local water availability, consumption, degradation, and pollution. The impact on the ecosystem will have to be considered too. But the numbers suggests that water consumption shouldn’t be a major barrier for scaling up renewable hydrogen, says Blanco.
Water consumption for green hydrogen: is it a constraint for scaling up?
Hydrogen is an essential component of a net zero emissions energy system. It complements electricity by providing an energy carrier with high energy density that is more easily transported and stored than electricity. Hence, it enables the decarbonisation of applications that are difficult to electrify.
Similar to electricity, hydrogen can be produced from multiple energy sources. The electrolytic route allows splitting water into oxygen and hydrogen by using of electricity. This allows taking advantage of the continuously declining renewable electricity costs, providing flexibility to the power sector and enabling an integrated energy system rather than separate sectors.
One common concern for electrolysis is the water consumption that is used as input and if it could pose a limitation to the large-scale production of hydrogen. This article aims to answer some of the key questions related to this issue.
How much water does electrolysis consume?
…Step 1: hydrogen production
Water consumption comes from two steps: hydrogen production and the production of the upstream energy carrier. Looking at hydrogen production, the minimum water electrolysis can consume is about 9 kg of water per kg of hydrogen. However, taking into account the process of water de-mineralisation, the ratio can range between 18 kg and 24 kg of water per kg of hydrogen or even up to 25.7-30.2 according to .
For the incumbent production process (steam reforming of methane), the minimum water consumption is 4.5 kgH2O/kgH2 (needed for the reaction), which increases to 6.4-32.2 kgH2O/kgH2 when considering the water for the process and cooling [1, 2].
…Step 2: the energy source (renewable electricity or natural gas)
The other component is the water consumption for the production of renewable electricity and natural gas. Water consumption for PV can vary between 50-400 l per MWh (2.4-19 kgH2O/kgH2) and between 5-45 l per MWh for wind (0.2-2.1 kgH2O/kgH2) . Similarly, natural gas production can be 1.14 kgH2O/kgH2 increasing to 4.9 kgH2O/kgH2 for shale gas (based on US data) .
In sum, the total water consumption for hydrogen from PV and wind can be, on average, around 32 and 22 kgH2O/kgH2 respectively (see Figure 1 below). Uncertainties arise from the solar radiation, lifetime and silicon content . This water consumption is in the same order of magnitude as hydrogen production from natural gas (7.6-37 kgH2O/kgH2 with an average of 22 kgH2O/kgH2) [1, 2].
Total water footprint: lower when using renewable energy
Similar to the CO2 emissions, a pre-condition for the electrolytic route to have a low water footprint is the use of renewable energy. If just a fraction of fossil-based generation is used the water consumption associated to the electricity is much higher than the actual water consumed in the electrolysis process.
For instance, water consumption for electricity production from natural gas can be up to 2,500 l per MWh . This is also using the best case for fossil fuels (from natural gas). If coal gasification is considered, it can consume 31-31.8 kgH2O/kgH2 for hydrogen production  with another 14.7 kgH2O/kgH2 from the coal production . Water consumption for PV and wind is also expected to decrease over time as the manufacturing process becomes more efficient and the energy output per unit of installed capacity also improves.
Figure 1. Lifecycle water consumption for various hydrogen production pathways / Sources: [2, 3].
Total water consumption in 2050
Future global hydrogen use is expected to be many times larger than today. For example, the World Energy Transitions Outlook from IRENA  estimates the 2050 hydrogen demand will be about 74 EJ, of which about two thirds will be from renewable hydrogen. This compares to 8.4 EJ today (for pure hydrogen).
Even if the entire 2050 hydrogen demand would be satisfied with electrolytic hydrogen, the water consumption would be about 25 bcm. Figure 2 (below) puts this number in perspective with other anthropogenic water consumption flows. Water consumption for agricultural use is the largest one of the order of 2,800 bcm, water for industrial uses is close to 800 bcm and 470 bcm for municipal uses [7-9]. Current hydrogen production from natural gas reforming and coal gasification has a water consumption of about 1.5 bcm.
So, even though a large growth of water consumption is expected due to the change to the electrolytical pathway and to the demand growth, water consumption for hydrogen production will still be much smaller than other flows for human use. Another point of reference is that the water withdrawals per capita is between 75 (Luxembourg) and 1,200 (US) m3 per year . Taking an average value of 400 m3/(capita*year), the total 2050 hydrogen production would be equivalent to a country with 62 million inhabitants.
Figure 2. Water consumption by application (circle size is proportional to water use in each application with agriculture at almost 2,800 km3/yr) / Sources: [7-9].
What is the cost and energy consumption of the water supply?
The electrolysers need high-quality water which requires water treatment. A low-quality water can lead to faster degradation and shorter lifetime. Many elements, including the diaphragm and catalysts for alkaline and the membrane and porous transport layer for PEM, can be adversely affected by water impurities such as iron, chromium, copper, among others. Water with conductivity of less than 1 μS/cm and total organic carbon of less than 50 μg/L is required.
Water is a relatively small share of both energy consumption and cost. The worst case for both parameters is the use of water desalination. The dominant technology for desalination is reverse osmosis with almost 70% of the global capacity and the main technology installed since early 2000s . This technology has a cost of USD 1,900-2,000/(m3/d) with a learning curve rate of 15% . With such an investment cost, the treatment cost is about USD 1/m3and potentially lower in regions with low-cost electricity.
Furthermore, transport cost can roughly add another USD 1-2/m3 . Even in such a case, the water treatment cost would be around USD 0.05/kgH2. To put this in perspective, renewable hydrogen cost can be USD 2-3/kg H2 today with good renewable resources and USD 4-5/kgH2 with average resources.
Thus, the water cost would represent less than 2% of the total cost in this conservative case (see Figure 3, left). Using seawater would increase the water intake by 2.5-5 times (based on the recovery ratio) .
Looking at energy consumption for water desalination, this is also very small compared to the electricity required as input to the electrolyser. Reverse osmosis plants in operation today consume around 3.0 kWhel/m3. In contrast, thermal desalination plants have a much higher energy consumption, ranging from 40 to 80 kWhth/m3, with additional electrical energy requirements of 2.5 to 5 kWhel/m3, depending on the desalination technology . Taking the conservative (i.e. higher energy demand) case of thermal plants, the energy demand would translate to about 0.7 kWh/kg of hydrogen assuming the use of heat pumps. To put this in perspective (see Figure 3, right), the electricity demand for the electrolyser is about 50-55 kWh/kg, so even in the worst case, the energy demand from desalination is in the order of 1% of the total energy input of the system.
One challenge with seawater desalination is the disposal of the brine, which could have a local impact on the marine ecosystem. The brine could be further treated to reduce its environmental impact increasing the cost of the water by another USD 0.6-2.4/m3 . Additionally, a stricter water quality for electrolysis compared to drinking water could lead to higher treatment cost but this is still expected to be small compared to the electricity input.
Figure 3. Contribution of water desalination to overall (a) production cost of hydrogen (b) energy consumption / Sources: [12, 15].
Water footprint is a very location-specific parameter that depends on the local water availability, consumption, degradation, and pollution. Balance with the ecosystem and impact from long-term climate trends should be considered. However, it is not foreseen that water consumption will be a major barrier for scaling up renewable hydrogen.
How much electricity is needed to make hydrogen? A completely efficient electrolysis system would require 39 kWh of electricity to produce 1 kg of hydrogen. However, the devices commonly found in operation for this process are less efficient. A typical operational figure is about 48 kWh per kg of hydrogen.How much energy does it take to electrolyze water? ›
The electrolysis of water under standard conditions requires a minimum of 237 kJ of electrical energy input to dissociate each mole of water. This is the standard Gibbs free energy of water formation..How much water does it take to make a kg of hydrogen? ›
In electrolytic hydrogen production, water is used directly as a feedstock. Using water's density and relative atomic populations, it is estimated by a mass balance that approximately 2.38 gallons of water are consumed as a feedstock to produce 1 kg of hydrogen gas, assuming no losses.Does hydrogen production use a lot of water? ›
Green hydrogen production will consume 1.5 ppm of Earth's freshwater or 30 ppb of saltwater each year, an amount smaller than what is currently consumed by fossil fuel-based energy production and power generation.Can you separate hydrogen from water without electricity? ›
One of the most common hydrogen production techniques is splitting water into hydrogen and oxygen. There are several ways to split water, such as with an electric current (electrolysis), heat, sunlight, or a substance that chemically reacts with water. Such substances include aluminum, zinc, and silicon.How much energy is 1kg of hydrogen? ›
In electrical terms, the energy density of hydrogen is equal to 33.6 kWh of usable energy per kg, versus diesel which only holds about 12–14 kWh per kg. What this really means is that 1 kg of hydrogen, used in a fuel cell to power an electric motor, contains approximately the same energy as a gallon of diesel.How much water do you need for green hydrogen? ›
The need for water
According to the National Hydrogen Strategy, the electrolysis process (the 'green' method for producing hydrogen with zero carbon emissions, when the electrolyser is powered by renewable electricity) needs significant water input, requiring around 9 litres for every 1 kilogram of hydrogen produced.
The lower the energy used by a generator, the higher its efficiency would be; a 100%-efficient electrolyser would consume 33.33 kilowatt-hours per kilogram (120 MJ/kg) (LHV, there is no water evaporated) of hydrogen, 12,749 joules per litre (12.75 MJ/m3).Is it energy efficient to produce hydrogen? ›
Electrolysis consists of using electricity to split water into hydrogen and oxygen. Electrolysis of water is 70–80% efficient (a 20–30% conversion loss) while steam reforming of natural gas has a thermal efficiency between 70 and 85%.How many Litres is 1kg of hydrogen? ›
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Hydrogen is now viewed as a viable alternative to fossil fuels. The hydrogen manufacturing process uses and produces water. In an era of water insecurity, it is crucial that the hydrogen industry makes it clear that it doesn't negatively impact water security or other water-heavy industries.How much hydrogen is in a Litre of water? ›
So one liter of water gives 110g of hydrogen gas, which is about 1.3 cubic meters of gas at normal temperature and pressure.Does hydrogen production require pure water? ›
A reliable, consistent water supply is critical to electrolyzer performance. Pure water is critical for hydrogen fuel production.How much water does a hydrogen car use? ›
On average, BEV-210s consume the smallest amount of water at 2 gal/100 miles when solar power is used, while the water consumption increases to 26 gal/100 miles when US grid electricity is used.How much hydrogen energy is in a gallon of water? ›
Re: How much Hydrogen from a Gallon of Water? The molecular weight of water = 18g/mol, and 2g of each 18g is hydrogen atoms, then the answer is 2/18 of the total starting material. 1 imperial gallon weighs 4.54kg or so, depending upon temperature, so there are 4.54kg x 2/18 = around 0.5kg of hydrogen to be had.Can you produce hydrogen without electricity? ›
Stemming from the phrase 'electrolysis'—chemical decomposition that occurs by passing an electric current through an electrolyte—Trolysis demonstrates an unprecedented way to conduct electrolysis of water in order to create hydrogen, sans the use of electricity.What is the most efficient way to produce hydrogen? ›
The carbon monoxide is reacted with water to produce additional hydrogen. This method is the cheapest, most efficient, and most common. Natural gas reforming using steam accounts for the majority of hydrogen produced in the United States annually.Does splitting water create energy? ›
Making water from its elements produces a large amount of energy. Chemical reactions that produce energy are also called exothermic reactions. In the case of hydrogen and oxygen the released energy is so high that it is almost impossible to control, and most of the time it leads to an explosion.How much energy is in a ton of hydrogen? ›
1, A kilogramme of hydrogen - the unit most often used – has an energy value of about 33.3 kWh.  So a tonne of hydrogen delivers about 33 MWh and a million tonnes about 33 terawatt hours (TWh).How much energy is in a Litre of hydrogen? ›
Hydrogen at 50 atmospheres pressure provides about 0.13 kilowatt-hours per litre, and liquid hydrogen provides 2.36 kilowatt-hours per litre. (Petrol or oil provide about 10 kilowatt-hours per litre.)
But it doesn't tell the whole story. In any of the latest fuel cell cars, 1 kg of hydrogen will let you drive 97 – 100 km.How long does it take to produce 1kg of hydrogen? ›
One electrolyser module produces 12 Nm³ of hydrogen gas in 24 hours, weighting >1kg (1.0785kg).How much water does a hydrogen fuel cell produce? ›
In a typical hydrogen fuel cell, each kilogram of fuel produces 9 kg of water.Where will the water come from for green hydrogen? ›
Nearly 85% of the green hydrogen capacity in the global pipeline may need to source its water from desalination, adding substantially to the cost of the H2 produced, according to Rystad Energy.How much hydrogen does a 1 MW electrolyser produce? ›
Hydrogenics will provide a 1 MW electrolyser that, powered by intermittent renewable energy, will produce 200 m3/h of hydrogen.Why are hydrogen fuel cells inefficient? ›
Hydrogen's efficiency problem
The reason why hydrogen is inefficient is because the energy must move from wire to gas to wire in order to power a car. This is sometimes called the energy vector transition.
The equivalent round trip from electricity into hydrogen by electrolysis and back into electricity through a fuel cell is less efficient as there are losses in the conversion and elsewhere in the process of getting energy into vehicles.Is hydrogen cheaper than electric? ›
Electric vehicles are also cheaper than hydrogen powered cars, while the cost of recharging is also less during off-peak grid times, making electric vehicles a good long-term investment.Is electric or hydrogen power better? ›
However, as hydrogen cars densely pack their energy storage, they're usually able to achieve longer distances. While most fully electric vehicles can travel between 100-200 miles on a single charge, hydrogen ones can get to 300 miles, according to AutomotiveTechnologies.Which countries produce the most hydrogen? ›
China is the largest producer of hydrogen today, at about 25 million tons (Mt), or roughly a quarter of the global total. Most of the volume is produced from fossil fuels (60 percent from coal, and 25 percent from natural gas) as feedstocks in refineries or chemical facilities.
Since each mole of water requires two moles of electrons, and given that the Faraday constant F represents the charge of a mole of electrons (96485 C/mol), it follows that the minimum voltage necessary for electrolysis is about 1.23 V.How much current is needed for H2 gas? ›
so the current required is 17.2321 amp.How much electricity does it take to split water? ›
The energy required to split water into hydrogen and oxygen by electrolysis is about 260 kJ per mole of water. Splitting one litre of water would take at least 16 MJ (4.4 kWh), which is an enormous expense on an industrial scale. It would be impossibly expensive.How long does it take to produce 1kg of hydrogen? ›
One electrolyser module produces 12 Nm³ of hydrogen gas in 24 hours, weighting >1kg (1.0785kg).How many amps does it take to produce hydrogen? ›
At 1 amp, it takes 96500*2 = 193000 seconds, 2 days, to generate one mol of hydrogen (that's 2 grams H2 or 22.4 liters, enough to fill a garment bag).How do you split hydrogen from water? ›
Electrolysis is the process of using electricity to split water into hydrogen and oxygen. This reaction takes place in a unit called an electrolyzer.How do you calculate hydrogen produced? ›
The electrical energy required to produce one kilogram hydrogen= Q x Vsplit. Practically one needs more than 1,229 V to split the water and the overvoltage required causes a conversion efficiency less than one.How many Litres is 1kg of hydrogen? ›
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1 liter of water = 1 kg of water. Molar mass of water = 18g, of which H2 = 2g, O = 16g. So 2/18 = 1/9 = 11%. So one liter of water gives 110g of hydrogen gas, which is about 1.3 cubic meters of gas at normal temperature and pressure.How much hydrogen energy is in a gallon of water? ›
Re: How much Hydrogen from a Gallon of Water? The molecular weight of water = 18g/mol, and 2g of each 18g is hydrogen atoms, then the answer is 2/18 of the total starting material. 1 imperial gallon weighs 4.54kg or so, depending upon temperature, so there are 4.54kg x 2/18 = around 0.5kg of hydrogen to be had.
Combining all the energy input totals, Gleick and Cooley found that producing bottled water requires between 5.6 and 10.2 million joules of energy per liter, depending on transportation factors (a typical personal-sized water bottle is about 0.5 liters).How hard is it to separate hydrogen from water? ›
Separating Hydrogen and oxygen from water is really simple. It can be as easy as sticking two wires leading from a battery into water and watching the bubbles form.What is the most efficient way to separate hydrogen from water? ›
To extract hydrogen from water, researchers insert two electrodes across the water and pass current, which can separate the hydrogen from water. The process called electrolysis of water.How much does it cost to make 1 kg of hydrogen? ›
This is in good alignment with the DOE analysis, which shows that hydrogen can be produced via PEM electrolysis at a cost of ~$4 to $6/kg for specific conditions.What is the cheapest way to produce hydrogen? ›
The carbon monoxide is reacted with water to produce additional hydrogen. This method is the cheapest, most efficient, and most common. Natural gas reforming using steam accounts for the majority of hydrogen produced in the United States annually.How far can a car travel on 1 kg of hydrogen? ›
But it doesn't tell the whole story. In any of the latest fuel cell cars, 1 kg of hydrogen will let you drive 97 – 100 km.