Solar thermal is the partner for hydrogen to decarbonise heat

The world has reached the point at which harnessing all options to mitigate climate change, is the only option: a variety of renewable energy technologies in combination are required to decarbonise global energy systems.

In this piece, we discuss the role of solar thermal technologies and hydrogen in our journey to reach net-zero carbon emissions globally.

We argue that whilst hydrogen will play a role in decarbonising our energy system in the future, particularly for so-called “hard-to-abate” sectors, solar thermal delivers higher carbon reduction in comparison to hydrogen-ready boilers for thermal energy generation. Therefore, solar thermal must be at the forefront of the conversation around the decarbonisation of heat.

As more than half of the global energy demand is in the form of heat, it becomes paramount to address the issue systemically.

In many buildings gas boilers are being used to generate space heat and hot water. Most current gas boilers would accept a small fraction of hydrogen blended in the gas mixture through a small technical modification, and many major manufacturers now have gas boilers that will accept a 20% hydrogen fraction. However, older gas boilers may need to be forfeited and replaced by newer ones. With the UK government banning gas boilers for new builds by 2025, alternatives must be found.

In the path towards heat decarbonisation, many governments including the UK are considering the option of blending hydrogen gas with its natural gas supply. With a 20% blend in natural gas composition, hydrogen can lower carbon dioxide emissions by 6% according to various reports [S1, S2, S3]. However, the difference is not proportional, as hydrogen has one third of the calorific value of natural gas on a volumetric basis. The reduction percentage is small and counterintuitive on a macro scale as we are aiming to maximize carbon reduction and reduce carbon dioxide emissions.

Depending on the source, the 6% reduction in emissions can be even lower. For instance, the use of brown hydrogen, produced from the steam reformation of natural gas, or grey hydrogen, produced from the gasification of coal or lignin, will result in a hydrogen gas with a higher carbon footprint in comparison to green hydrogen produced from renewable electricity – such as wind farms [S4].

The production of green hydrogen also suffers from energy conversion inefficiencies. Green hydrogen involves the generation of renewable electricity to generate hydrogen by electrolysis, which is used in heating or power production [S5]. With the emissions factor of the grid being higher than that of natural gas, it is hard to justify the use of green electricity for electrolysis, instead of direct consumption, to decarbonise.

On the other hand, a typical solar thermal system or hybrid solar photovoltaic thermal (PVT) collector can contribute upwards of 50% of the thermal demand of a building. By integrating a solar heat system, gas use can be reduced by 50%, leading to a 50% reduction in carbon emissions; 8 times higher than the 6% reduction achieved with hydrogen blended gas.

Given the current state of infrastructure and cost, it is hard to see hydrogen as a necessity at this stage for thermal energy generation in comparison to solar thermal technology.

However, Hydrogen will most certainly be an essential technology in the pathway towards net zero carbon and in the mitigation of global warming. This is especially truefor the “hard-to-abate” sectors, such as heavy transportation or the steel industry where it will undoubtedly shine.

Naked Energy’s VirtuPVT is an innovative design and features transforming solar technology and enabling decarbonisation in commercial and residential sectors alike. VirtuPVT is the world’s first evacuated combined heat and power solution with the highest energy density and efficiency in a modular design. Virtu is also suitable for industrial applications that often require higher temperature heat than domestic projects. Naked Energy’s Virtu technology delivers a high grade of heat up to 120°C and high energy outputs from relatively small areas, making it suitable for many industrial processes.

Naked Energy is a British design and engineering business, leading the globalinnovation in solar thermal and solar PVT with a mission to change energy for good.The business has set out to decarbonise heating and cooling globally, and so supportthe transition to net zero carbon. Naked Energy’s high energy density solutions arecapable to decarbonise heat affordably given its distributed nature, and its solar PVTtechnology delivers up to 3.5 times the energy per m2 in comparison to conventional solar electricity or PV technology.

References:

S1: IEA-GHGR&D, "Reduction of CO2 emissions by adding hydrogen to natural gas," IEA Greenhouse Gas R&D Programme, 2003.

S2: Z. McDonald, "Injecting hydrogen in natural gas grids could provide steady demand the sector needs to develop," S&P Global, 2020.

S3: J. Lalach; A. Bellini, "How about some clean, green hydrogen with that natural gas?," Gowling WLG, 2021.

S4: "Green hydrogen production: Landscape, projects and costs," Wood Mackenzie, 2019.

S5: T. DiChristopher, "Hydrogen technology faces efficiency disadvantage in power storage race," S&P Global, 2021