China cell turns heat into electricity without sun

November 29, 2024

A novel hydrovoltaic cell developed by researchers at the Chinese Academy of Sciences (CAS) can continuously generate electricity using little water and no sunlight. This feature could help deploy the device in remote places, in harsh conditions, and at night when solar-powered energy generators do not work. 

With the increasing demand for cleaner sources of energy, researchers are working on innovative approaches that can help us meet our energy demands without the carbon emissions seen from fossil fuels. 

A hydrovolcanic cell generates electricity by absorbing energy from the interaction of water with other surfaces. Like their photovoltaic counterparts, hydrovolcanic cells depend on sunlight to power their operations, and their outputs have been limited by environmental conditions like sunlight and wind. 

Typically hydrovoltaic cells require a continuous supply of water and low humidity environments to function at their best efficiencies. However, researchers at CAS overcame this by hermetically sealing the cell and making it an almost closed system that can operate without being impacted by external conditions.

How does the hydrovoltaic cell work?

The hermetic hydrovolcanic cell (HHC) consists of an internal electricity generation unit made from carbon black and tissue paper.

A small heterogenous wicking bilayer designed for the cell sets up a continuous water circulation using capillary flow from the tissue paper and slight fluctuations in the ambient temperature that cause evaporation. 

The electricity generation unit converts ambient heat into power output. According to the researchers, their unit generated a stable electricity output for 160 hours with negligible water consumption, making it ideal for deployment in water-scarce areas such as deserts or even underground engineering sites.

The researchers also found that intense light can promote HHC output. This is likely due to increased absorption by the carbon black, which increases the moisture gradient inside the cell through the photothermal effect. This improves the electricity generation in the HHC.

Fluctuations the key

Research efforts into the development of the HHC also brought a previously unknown internal circulation effect to the fore. While it has been assumed that temperature fluctuations are detrimental to energy generation, in the case of this cell, they facilitated a closed-loop circulation, leading to continuous power generation.

The HHC has a moderate open-circuit voltage, but researchers suggest it has the highest energy conversion efficiency since it does not consume any new water. The approach also addresses the limitations posed by environmental conditions.

The researchers are confident that their approach helps generate electricity at a low cost and is easily accessible. Moreover, since ambient heat is an inexhaustible energy source, the team has successfully converted this low-grade energy source into usable power. 

With a stable output and no additional water consumption, the approach can easily meet energy requirements at various types of locations. The researchers hope that their approach inspires other groups to innovate further in this field and develop much more efficient designs in the future.