The water-filled glass hoping to revolutionise building design

Water-filled glass could ‘revolutionise building design’ when used as part of a wider heating system, according to Hungarian engineer Dr Matyas Gutai, who has been studying the concept for over a decade.

The research was performed at Loughborough University and in collaboration with Dr Albofazl Kheybari from the University of Kaiserslautern in Germany.

The process involves a sheet of water being trapped between a panel of glass, acting as an effective insulator. Research suggests that the system performs well in any inhabited climate – keeping buildings hot in cooler climates and cooler in warmer climates – without the assistance of any additional energy supplies.

Dr Gutai conceptualised the idea during his PhD studies in Tokyo after being inspired by rotenburo, which are Japanese hot spring baths.

He developed the idea into a working design then created two prototype buildings in Hungary and Taiwan that use water-filled glass as part of a larger mechanical system.

In warmer climates, the water absorbs external and internal heat, with the warm water later being filtered into a storage tank. This helps keep the room cool.

According to the research, the heat is stored in the tank and, if the temperature drops, can be brought back into the walls to reheat the building using a temperature monitoring system in a similar vein to central heating.

Alternatively, the stored heat can be used for hot water supply.

The system is supposed to be able to conserve energy as the water absorption and pumping consumes far less energy than HVAC systems. The technology is also claimed to have other benefits, including acoustics, less need of ‘shading’ (methods used to avoid overheating and the greenhouse effect), and there is no need to colour the glass to improve energy efficiency.

Dr Gutai has also developed a more sophisticated version of the system by adding a heat pump, which can heat and cool water depending on the season, which is examined in the latest research paper. He joined Loughborough University in 2017 and has used data gathered from the two Water Houses to develop a simulation system that can evaluate the performance of such structures.

The paper uses simulations to compare the performance of the WFG system (with a heat pump) against typical heating systems, such as central heating and air conditioning.

The study focuses on the annual energy consumption for a typical office space with one glazed facade of equilateral orientation. He simulated how this office with his system would fair in 13 different systems from all major earth climates – dry, tropical, temperate, continental and polar.

For the traditional systems, Dr Gutai looked at the performance of double glass window in low-e, and triple glass, which are filled with argon.

The primary findings of the study are that the WFG system uses the absorption of the water effectively to improve the energy performance of the glass and that the water layer lowers the load for heating and cooling effectively, minimising daily and seasonal peaks.

Simulations also highlighted that current glass technologies could lead to bigger savings if more focus was made on improving solar absorption as opposed to focusing solely on insulation.

In a statement, Dr Gutai said: “Glass is currently a liability in buildings as it compromises energy consumption, thermal comfort, acoustics and other aspects. WFG changes this paradigm and turns glass into an opportunity for sustainable construction.

“It shows us that thinking holistically about buildings and building components leads to a more efficient and sustainable built environment.

“In case of a window for example, if we see it as an isolated system, solar overheating is a challenge that needs to be remedied with cooling. If we approach this holistically, the heat surplus is an opportunity because the same heat is missing from somewhere else [a colder part of the building or hot water supply].”

Dr Gutai hopes that he can turn this concept into a tangible product and is working with various colleagues to achieve this.

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