Ammonia-Powered Systems Advance Energy Transition While Producing Sustainable Electricity and Freshwater

Ammonia could become more than a carbon-free fuel for ships and power stations: a new energy-system design proposes using it to produce electricity and freshwater at the same time. The concept, developed by Mohammadreza Mohammadpour, Amirreza Mohammadpour, Mehdi Ashjaee and Ehsan Houshfar, combines an ammonia-fed solid oxide fuel cell with a hybrid desalination plant and a thermoelectric generator. The architecture is designed to extract value from nearly every stream leaving the system. Electricity is generated electrochemically, salt water is processed through reverse osmosis and humidification–dehumidification desalination, and otherwise wasted heat is converted into additional power. The study evaluates the arrangement using energy, exergy, economic and sustainability analyses, and applies a genetic algorithm to search for operating conditions that balance competing goals. Its appeal lies in the integration: instead of treating heat, brine and exhaust gases as unwanted by-products, the system attempts to turn them into useful outputs for homes or small communities.

The central fuel is ammonia, or NH₃, a molecule that contains no carbon. Burning it does not directly produce carbon dioxide, although its manufacture can still be emissions-intensive unless powered by low-carbon electricity or supplied with hydrogen made from renewable sources. Compared with pure hydrogen, ammonia is easier to liquefy, store and transport, and its pungent odor can make leaks rapidly detectable. It also carries hydrogen in a chemically dense form. The proposed system exploits those properties in a solid oxide fuel cell, a high-temperature electrochemical device that converts chemical energy into electricity without combustion as its primary conversion step. Unlike a conventional battery, the fuel cell continuously receives reactants. Unlike a combustion engine, it can avoid the temperature-limited expansion process that typically discards a large fraction of chemical energy as heat, although it still produces substantial high-temperature exhaust that must be managed carefully.

Inside the fuel cell, ammonia is first heated to temperatures at which it can decompose into nitrogen and hydrogen. The governing equilibrium reaction is 2NH₃ ⇌ N₂ + 3H₂. The hydrogen then participates in electrochemical reactions at the anode, while oxygen from air is reduced at the cathode. Oxygen ions migrate through the ceramic electrolyte and react with hydrogen to form water, releasing electrons that travel through an external circuit. In simplified form, the cathode receives half an oxygen molecule and two electrons to create an oxide ion, while the anode combines hydrogen with that ion to produce water and return the electrons to the circuit. The process generates direct-current electricity, which is subsequently converted to alternating current by an inverter. Because the fuel cell operates at about 1,000 kelvin in the study’s baseline model—roughly 727 °C—the incoming ammonia and air must be preheated before entering the stack.

High temperature is both the system’s advantage and its engineering challenge. It accelerates ammonia cracking and supplies heat that can be reused, but it also creates opportunities for material degradation, thermal stress and unwanted emissions if the chemistry is not controlled. The model accounts for voltage losses caused by activation, concentration and ohmic resistance. Activation losses arise because electrochemical reactions require finite driving forces; concentration losses appear when reactants or products become unevenly distributed near the electrodes; and ohmic losses result from resistance in the electrodes, electrolyte and interconnections. The cell voltage is therefore lower than its ideal Nernst voltage, which depends on temperature and the partial pressures of hydrogen, oxygen and water. Fuel and air utilization factors determine how much reactant is consumed inside the cell. The baseline assumptions use a fuel-utilization factor of 0.85 and an air-utilization factor of 0.167, leaving residual gases available for further heat recovery.

Those residual gases enter an afterburner, where unreacted hydrogen and ammonia react with oxygen. The resulting hot exhaust is not treated simply as waste. It first transfers heat to the incoming fuel and air in a preheater, helping the fuel cell reach its operating temperature. It then supplies heat to other components, including a heat exchanger connected to the water-treatment section and a thermoelectric generator. Thermoelectric generators rely on the Seebeck effect: when two sides of a suitable semiconductor material are maintained at different temperatures, a voltage develops and electrical current can flow. The device has no moving parts, produces no direct emissions and can operate quietly, but its efficiency is constrained by the material’s thermoelectric figure of merit and by the temperature difference available across it. In the proposed arrangement, the hot side receives heat from the fuel-cell exhaust while the cold side is cooled by another working stream. The study calculates the generator’s performance relative to its Carnot limit, the theoretical maximum efficiency for converting heat between the hot and cold temperatures.

The water-production side of the design uses two desalination processes in sequence. Reverse osmosis pushes seawater through a semipermeable membrane at high pressure. Water molecules pass through more readily than dissolved salts, producing a freshwater stream and a concentrated brine stream. The pump is an important electrical load because the pressure required rises with salinity and membrane conditions. Rather than discard the brine, the proposed system sends it to a humidification–dehumidification unit. In HDH desalination, heated saline water contacts a carrier gas, commonly air, allowing some water to evaporate while leaving most dissolved salts behind. The warm, moisture-rich air then reaches a dehumidifier, where cooling causes water vapor to condense as freshwater. The approach operates at relatively moderate temperatures and can tolerate feed-water conditions that may challenge some other desalination technologies. By giving RO brine a second treatment stage, the design aims to reduce brine discharge and increase the total freshwater yield from the original seawater feed.

The proposed plant also includes a Pelton turbine associated with the pressurized water pathway. In principle, pressure energy that would otherwise be dissipated can be converted into mechanical power before or around the desalination process. The model tracks the mass, energy and exergy flows through the fuel cell, afterburner, preheater, heat exchanger, thermoelectric generator, pump, turbine and both desalination units. Energy efficiency measures how much of the ammonia’s chemical energy becomes useful net electrical output after accounting for pumping demand. Exergy efficiency is more demanding: it evaluates the quality of energy and identifies how far the real system operates from an ideal reversible process. Heat at a low temperature, for example, contains less ability to perform useful work than electricity, even if both carry the same amount of energy. The researchers also use a sustainability index linked to exergy destruction. In that framework, higher values indicate fewer internal irreversibilities and more effective use of the fuel’s available work potential.

Economic analysis is essential because a technically efficient system may still be too expensive to deploy. The study estimates equipment costs for the solid oxide fuel-cell stack, thermoelectric generator, reverse-osmosis unit, preheater, heat exchanger, afterburner, humidifier, dehumidifier, high-pressure pump and Pelton turbine. It applies a capital-recovery factor over a presumed 20-year lifetime, uses a 15% interest rate and assumes 7,500 operating hours per year. These assumptions allow the researchers to translate capital investment, maintenance and operating time into an equivalent cost rate. The approach also exposes where design improvements could matter most. Fuel-cell stacks are often costly because they require specialized electrochemical materials and high-temperature seals, while desalination costs are strongly influenced by membrane area, pressure requirements and water throughput. The thermoelectric generator may recover otherwise lost heat, but its economic justification depends on whether the additional electricity outweighs the cost of the modules and heat-transfer hardware.

The researchers do not seek a single performance measure in isolation. Increasing ammonia flow, for example, could raise power production while also increasing equipment size, heat rejection and fuel cost. Raising fuel utilization may reduce chemical losses but alter temperature profiles and electrochemical voltage. Greater humidifier or dehumidifier effectiveness could improve water production, yet require more surface area and capital investment. The study therefore uses the NSGA-II evolutionary genetic algorithm, a method designed for multi-objective optimization. It generates candidate operating points, ranks them according to whether one solution outperforms another across the selected objectives, and evolves the population through crossover and mutation. The resulting Pareto frontier represents compromises that cannot be improved in one direction without sacrificing another. The model varies parameters including ammonia molar flow, fuel and air utilization, dehumidifier effectiveness and desalination mass flow. This matters because the most practical operating point for a residence, an industrial facility or a remote settlement may differ substantially: one site may prioritize electricity, another freshwater, and a third low cost or reduced thermodynamic waste.

The study’s broader significance is that it treats energy and water as a coupled infrastructure problem rather than separate technological challenges. Ammonia can provide dispatchable chemical energy when solar or wind output fluctuates, while the fuel cell’s high-grade heat can support thermal desalination and auxiliary power generation. Reverse osmosis supplies the pressure-driven part of water purification, and HDH uses the rejected brine and available heat to recover additional water. The thermoelectric generator adds a small but potentially useful electrical stream without introducing rotating machinery. Yet the concept is not automatically climate-neutral: the environmental outcome depends heavily on how ammonia is produced, how long the fuel-cell materials last, how much water the process consumes and whether nitrogen-oxide emissions form in the afterburner. The analysis is a system-level design and simulation study, not evidence that a commercial plant has already been built or demonstrated. Its viral potential comes from the striking promise of one integrated machine producing two essentials—electricity and drinking water—but its real test will be whether the chemistry, durability, cost and life-cycle emissions can match the elegance of the thermodynamic concept.