Oak Ridge National Laboratory scientists have developed a novel method that could yield lower-cost, higher-efficiency systems for water heating in residential buildings. Described in a new report the newly termed “semi-open” natural gas-fired design reduces the cost and complexity of traditional closed gas-fired systems by streamlining, and even eliminating, certain components.

The team of scientists from the Department of Energy’s Oak Ridge National Laboratory and the University of Florida developed the novel method that could yield lower-cost, higher-efficiency systems specifically for water heating in residential buildings.

A new class of gas-fired heat pump water heaters, based on a novel semi-open sorption concept, could replace the evaporator in a traditional devices with a vapor-permeable membrane that more efficiently absorbs and transfers heat for residential applications. Image Credit: ORNL Click image for the largest view.

A new class of gas-fired heat pump water heaters, based on a novel semi-open sorption concept, could replace the evaporator in a traditional devices with a vapor-permeable membrane that more efficiently absorbs and transfers heat for residential applications.
Image Credit: ORNL Click image for the largest view.

The theory behind the newly termed “semi-open” natural gas-fired design, has been explained in a research paper “Efficiency Analysis of Semi-Open Sorption Heat Pump Systems.” published in Renewable Energy: An International Journal.

ORNL’s Kyle Gluesenkamp, lead author of the paper said, “When applied, the new concept could result in better than 100 percent energy efficiency, because the system draws energy from the surrounding air as well as from the natural gas.”

The versatile design combines water heating and dehumidification functions, which are typically found in separate architectures. In the semi-open scenario, the novel absorber device acts in place of the traditional evaporator component, pulling water vapor directly from the air through a membrane into a liquid solution. As the vapor 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 an inexpensive, non-sealed solution pump. This approach eliminates the need for vacuum pumps found in closed systems that purge gas build up. It also allows manufacturers to consider lower-cost, lightweight polymers instead of costly, bulkier metals to build equipment, making it less susceptible to corrosion.

Sounds great, if all the presumptions are scalable hot water at temperatures used for homes and offices could get quite a bit less costly. Current water heaters are pretty good, most without any moving parts, and have non corrodible glass lined tanks. It will be interesting to see if the known best practices and the new technology will come to market working together.


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