A solar hydrogen system that co-generates heat and oxygen

Date:
April 17, 2023
Source:
Ecole Polytechnique Fe'de'rale de Lausanne
Summary:
Researchers have built a pilot-scale solar reactor that produces
usable heat and oxygen, in addition to generating hydrogen with
unprecedented efficiency for its size.


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FULL STORY ==========================================================================
A parabolic dish on the EPFL campus is easily overlooked, resembling a satellite dish or other telecommunications infrastructure. But this dish
is special, because it works like an artificial tree. After concentrating
solar radiation nearly 1,000 times, a reactor above the dish uses that
sunlight to convert water into valuable and renewable hydrogen, oxygen,
and heat.


========================================================================== "This is the first system-level demonstration of solar hydrogen
generation.

Unlike typical lab-scale demonstrations, it includes all auxiliary devices
and components, so it gives us a better idea of the energy efficiency
you can expect once you consider the complete system, and not just the
device itself," says Sophia Haussener, head of the Laboratory of Renewable Energy Science and Engineering (LRESE) in the School of Engineering.

"With an output power of over 2 kilowatts, we've cracked the 1-kilowatt
ceiling for our pilot reactor while maintaining record-high efficiency
for this large scale. The hydrogen production rate achieved in this work represents a really encouraging step towards the commercial realization of
this technology." The work builds on preliminary research demonstrating
the concept on the laboratory scale, using LRESE's high-flux solar
simulator, which was published in Nature Energy in 2019. Now, the team
has published the results of their scaled-up, efficient, and multi-product process under real-world conditions in the same journal.

Waste not, want not Hydrogen production from water using solar energy
is referred to as artificial photosynthesis, but the LRESE system is
unique for its ability to also produce heat and oxygen at scale.

After the dish concentrates the sun's rays, water is pumped into
its focus spot, where an integrated photoelectrochemical reactor is
housed. Within this reactor, photoelectrochemical cells use solar energy
to electrolyze, or split water molecules into hydrogen and oxygen. Heat
is also generated, but instead of being released as a system loss, this
heat is passed through a heat exchanger so that it can be harnessed --
for ambient heating, for example.

In addition to the system's primary outputs of hydrogen and heat, the
oxygen molecules released by the photo-electrolysis reaction are also
recovered and used.

"Oxygen is often perceived as a waste product, but in this case,
it can also be harnessed -- for example for medical applications,"
Haussener says.

Industrial and residential energy The system is suitable for industrial, commercial, and residential applications; in fact, LRESE-spinoff SoHHytec
SA is already deploying and commercializing it. The EPFL start-up
is working with a Swiss-based metal production facility to build a demonstration plant at the multi-100-kilowatt scale that will produce
hydrogen for metal annealing processes, oxygen for nearby hospitals,
and heat for the factory's hot-water needs.

"With the pilot demonstration at EPFL, we have achieved a major
milestone by demonstrating unprecedented efficiency at high output power densities. We are now scaling up a system in an artificial garden-like
setup, where each of these 'artificial trees' is deployed in a modular fashion," says SoHHytec co-founder and CEO Saurabh Tembhurne.

The system could be used to provide residential and commercial central
heating and hot water, and to power hydrogen fuel cells. At an output
level of about half a kilogram of solar hydrogen per day, the EPFL
campus system could power around 1.5 hydrogen fuel cell vehicles driving
an average annual distance; or meet up to half the electricity demand
and more than half of the annual heat demand of a typical four-person
Swiss household.

With their artificial photosynthesis system well on its way to scale-up, Haussener is already exploring new technological avenues. In particular,
the lab is working on a large-scale solar-powered system that would
split carbon dioxide instead of water, yielding useful materials like
syngas for liquid fuel, or the green plastic precursor ethylene.

* RELATED_TOPICS
o Matter_&_Energy
# Solar_Energy # Thermodynamics # Alternative_Fuels #
Materials_Science
o Earth_&_Climate
# Energy_and_the_Environment # Renewable_Energy #
Environmental_Science # Water
* RELATED_TERMS
o Scale_model o Absolute_zero o Fujita_scale o
Distributed_generation o Fuel_cell o Solar_power o
Greenhouse_effect o Richter_magnitude_scale

========================================================================== Story Source: Materials provided by
Ecole_Polytechnique_Fe'de'rale_de_Lausanne. Original written by Celia Luterbacher. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Isaac Holmes-Gentle, Saurabh Tembhurne, Clemens Suter, Sophia
Haussener.

Kilowatt-scale solar hydrogen production system using a concentrated
integrated photoelectrochemical device. Nature Energy, 2023; DOI:
10.1038/s41560-023-01247-2 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/04/230417142442.htm

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