Thermal performance assessment of aqua-ammonia in space heating applications

• Aqua-ammonia (A-A) evaluated as an alternative fuel for residential space heating. • A-A enables safe, low-pressure energy transport via existing gas pipeline infrastructure. • 13% A-A concentration meets UK home heating needs with up to 97.5% system efficiency. • A-A systems require 65–200 × less flow capacity than water-source heat pump networks. • Gray/blue ammonia offer near-term cost parity with NG; green ammonia feasible by 2050. As countries move toward net-zero emissions, replacing natural gas (NG) in residential heating systems has become a critical challenge—especially in the UK, where gas boilers are still the norm. This study explores aqua-ammonia (A-A)—a liquid mixture of ammonia and water—as a promising alternative fuel. A-A remains stable at room temperature, is far less toxic and corrosive than pure ammonia, and can be transported using existing gas infrastructure with minor adjustments. Through detailed thermodynamic modelling, the research assesses how A-A performs in both energy transmission and household heating. The findings show that A-A concentrations above 6% can deliver more energy than NG in urban pipelines. Concentrations between 13% and 25% are well-suited for space heating, with 13% sufficient to meet typical UK household demands without any additional fuel input. System efficiencies reach up to 97.5%, and even at peak winter use, daily consumption is modest—around 150 L, or roughly 38% of a household’s daily water usage. Compared to water-source heat pumps, A-A systems require up to 200 times less fluid flow, easing pressure on distribution networks. Cost analyses indicate that heating with grey or blue ammonia can already rival or undercut NG, and green ammonia may offer even lower costs by 2050. Overall, A-A offers an efficient, adaptable, and low-carbon solution for residential heating, with clear advantages in both infrastructure compatibility and long-term sustainability.