Nuclear power plants generate significant amounts of low-grade waste heat as a byproduct of electricity generation. This heat, often discharged into the environment, presents an opportunity for auxiliary hydrogen production through integration with complementary technologies. By recovering and repurposing this thermal energy, nuclear facilities can enhance their overall efficiency while contributing to clean hydrogen generation. Two promising methods for utilizing this waste heat are low-temperature electrolysis and thermal desalination for feedstock water preparation.
Low-temperature electrolysis, particularly proton exchange membrane (PEM) and alkaline electrolysis, can benefit from waste heat by reducing the electrical energy required for hydrogen production. Electrolysis efficiency improves at higher temperatures due to faster reaction kinetics and reduced overpotentials. For instance, raising the operating temperature of a PEM electrolyzer from 80°C to 120°C can decrease the cell voltage requirement by approximately 0.1 V, translating to a 5–10% reduction in electrical energy consumption per kilogram of hydrogen produced. When waste heat from a nuclear plant is used to preheat the electrolyzer, the system’s overall energy demand decreases, allowing more hydrogen to be generated per unit of electricity consumed.
A study on integrating waste heat with a 1 MW electrolysis system demonstrated that preheating the feedwater using low-grade heat could increase hydrogen output by up to 8% without additional electrical input. In a nuclear plant with a thermal output of 3,000 MWth, diverting just 1% of the waste heat to support electrolysis could yield an additional 1–2 tonnes of hydrogen per day, depending on the electrolyzer efficiency and heat recovery rate.
Thermal desalination is another viable application for nuclear waste heat, particularly in regions where freshwater scarcity limits hydrogen production. Electrolysis requires high-purity water, and conventional reverse osmosis desalination is energy-intensive. By contrast, thermal desalination methods such as multi-effect distillation (MED) or mechanical vapor compression (MVC) can utilize low-grade heat to produce the necessary feedstock. For every 100 MW of waste heat directed to MED systems, approximately 20,000–30,000 cubic meters of freshwater can be produced daily, sufficient to support large-scale electrolysis operations.
The synergy between nuclear waste heat and desalination not only ensures a reliable water supply but also reduces the parasitic energy load on the plant. For example, a nuclear facility coupled with a MED unit can decrease the energy penalty for water purification by 30–40% compared to electrically driven desalination. This efficiency gain directly translates to higher net hydrogen output when the purified water is used in electrolysis.
Quantifying the impact of waste heat recovery on overall plant efficiency requires examining both the thermal and electrical pathways. A typical nuclear plant operates at 30–35% thermal efficiency, meaning 65–70% of the energy is lost as waste heat. By recovering even a fraction of this heat for hydrogen production, the plant’s total energy utilization can improve by 2–5 percentage points. For a 1,000 MWe reactor, this equates to an additional 20–50 MWe worth of energy being productively used for hydrogen generation rather than dissipated.
The table below summarizes potential hydrogen yield improvements from waste heat integration in a nuclear plant with 3,000 MWth output:
Application | Waste Heat Utilized (MW) | Additional Hydrogen Output (tonnes/day)
Low-Temperature Electrolysis | 30 | 1.2–1.8
Thermal Desalination | 100 | 0.8–1.2 (via water savings)
Beyond efficiency gains, waste heat recovery for hydrogen production aligns with broader decarbonization goals. Nuclear-assisted hydrogen reduces reliance on fossil-based steam methane reforming, which emits 9–12 kg of CO2 per kg of hydrogen. By contrast, hydrogen from nuclear-coupled electrolysis or thermochemical processes can achieve near-zero emissions if the electricity is sourced from the plant itself.
Challenges remain in optimizing heat exchanger designs, managing corrosion in high-temperature electrolyzers, and scaling desalination systems for integration with nuclear facilities. However, pilot projects in Canada and Japan have demonstrated technical feasibility, with some achieving waste heat recovery rates exceeding 50% for auxiliary processes.
In conclusion, leveraging low-grade waste heat from nuclear plants for hydrogen production enhances both energy efficiency and output. Low-temperature electrolysis and thermal desalination offer practical pathways to utilize this heat, with measurable improvements in hydrogen yield and plant performance. As nuclear operators seek to diversify their energy products, waste heat recovery stands out as a strategic opportunity to advance clean hydrogen economies.