HH-Gen: High performance green hydrogen generation from solar energy

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Innovate UK
Innovate UK
Innovate UK
Innovate UK
Innovate UK

£1,337,015

Sept. 30, 2020

Nov. 30, 2021

In 2018, the IPCC concluded that limiting global warming to 2ºC requires a reduction in CO2 emissions of 25% by 2030 compared with 2010 levels, and to reach net zero by 2070\. Hydrogen is a clean-energy solution representing an important aspect of the transition to renewable energies required to prevent catastrophic climate change.

"Green" hydrogen produced from renewable sources can address critical energy challenges. It offers a route to decarbonise many sectors such as aviation, long-haul transport, chemicals manufacture, and iron and steel, where it is challenging to reduce emissions.

Hydrogen is a versatile fuel, both in terms of supply and use, which can store large quantities of energy for prolonged periods of time, and can transport energy over long distances. It can enable renewable energy resources to provide greater contribution, with potential to mitigate issues with variable output from renewables, such as solar photovoltaics (PV) and wind.

However, producing hydrogen from renewable energy resources is currently expensive, and \>90% of global hydrogen production comes from fossil fuels (so-called "grey" hydrogen. mostly steam reforming of natural gas). Although the costs of producing hydrogen from renewable electricity are falling, significant advances are required in the state of the art so that green hydrogen becomes cost competitive with alternatives.

FocalSun's technology aims to solve issues with the cost of production of green hydrogen. We seek to achieve this by focusing on eliminating inefficiencies in the processes used to produce hydrogen from solar energy.

Consider a large array of solar panels connected to the grid, which is then connected to an electrolyser to generate hydrogen through electrolysis of water. There are several inefficiencies:

* PV panels are around 18-20% efficient and typically static and do not track the sun (meaning efficiency is in reality less than 18-20%). FocalSun uses bi-axial concentrating solar optics in combination with high-efficiency multi-junction solar cells, which are ~45% efficient. In combination with thermal energy recovery, this can result in more than 80% of the incident solar energy being captured for use as part of a hydrogen production system.
* Solar cells produce DC electricity, which is converted to AC, typically transmitted several miles, then converted back to DC to power the electrolyser. DC/AC and AC/DC conversion consumes around 5-10% of the produced energy. FocalSun is designed so that the electrolyser is co-located with the solar power system, enabling direct coupling of the electrical energy, eliminating these losses.

This project will address these efficiencies to enable green hydrogen to become cost-competitive with grey hydrogen. Moreover, because the directly-coupled configuration requires a compact electrolyser, this enables us to develop high-pressure electrolysers, where the water used for electrolysis is compressed so that the hydrogen is directly produced at high pressure, thus eliminating the pumping losses to compress hydrogen for transmission. Pressurising water requires much less energy than pressuring hydrogen gas because the change in volume that occurs is far smaller. This represents a future R&D direction, and a pathway to further reducing the cost of green hydrogen.