Regenerable aerogel-based thermogalvanic cells for efficient low-grade heat harvesting from solar radiation and interfacial solar evaporation systems

Direct conversion of low-grade heat into electricity by thermal electrochemical cells is a promising strategy for energy generation. For stable heat-to-electricity conversion, maintaining a low-grade heat induced temperature difference between the cell electrodes is essential. Here, a thermogalvanic cell consisting of a cellulose fiber-based porous aerogel, a liquid electrolyte, a reduced graphene oxide light absorber, and carbon nanotube-based electrodes is designed for low-grade thermal energy harvesting and conversion. The low thermal conductivity of the porous cellulose aerogel enables limited heat transfer from the hot side to the cold side, and thermal energy management effectively reduces heat loss from the hot side to the environment. Thus, a sustainable temperature difference between the electrodes is maintained and a corresponding maximum power output of 6.94 mW m(-2) is achieved under natural solar irradiation. The obtained thermal electrochemical cells are also integrated into an enclosed interfacial solar evaporation device to harvest the latent heat released from vapor condensation for electricity generation. In addition, the thermal electrochemical cells can be regenerated after 18 months of storage and show no performance degradation. This design thus offers a novel alternative strategy for practical low-grade heat harvesting.