A new type of gas-fired domestic water heater being developed in the US could operate at efficiency levels of greater than 100 per cent, its creators claim.
The ‘semi-open’ natural gas fired design, which has emerged from research by scientists at the US Department of Energy’s Oak Ridge National Laboratory and the University of Florida, reduces the cost and complexity of traditional closed systems by streamlining some components and eliminating others.
The resulting design combines water heating and dehumidification functions that are typically found in separate architectures. A novel absorber device acts in place of the traditional evaporator component, pulling water vapour directly from the air through a membrane into a liquid solution. As the vapour is absorbed, much of the heat is transferred to domestic hot water.
The simpler semi-open system would operate at the surrounding atmospheric pressure, using a non-sealed pump. Eliminating the need for vacuum pumps responsible for purging gas build up in closed systems would allow manufacturers to replace bulky metal components that are susceptible to corrosion with cheaper lightweight polymer alternatives.
"When applied, the new concept could result in better than 100 per cent energy efficiency, because the system draws energy from the surrounding air as well as from the natural gas," said Oak Ridge scientist Kyle Gluesenkamp, who is lead author of a paper describing the technique published in Renewable Energy: An International Journal.
The researchers believe a new class of ultra-efficient heat pump water heaters based on their work could become commercially available to homeowners within a few years.