Save excess electricity & unlock grid balancing? Call green hydrogen

Decentralised electrolysis can harness and balance fluctuating renewable energy

30. novembre 2022

Renewable electricity is finally being rolled out with pace. And while it’s not causing overwhelming grid issues as alarmists make it out, we’ll still need solutions to help balance the energy fluctuations.

That brings us to grid balancing. There are many nuances captured in this term, from grid stabilisation to energy curtailment, but the concept boils down to ensuring the correct amount of energy – no more, no less – is generated and delivered to the grid in the right place at the right time.

And green hydrogen is a solution that can contribute to this, thanks to its ability to take renewable energy regardless of location or environment and turn it into a storable and versatile energy carrier. If we can do it right, the rewards are clear.

Research from the Reiner Lemoine Instituts (RLI) found that decentralised electrolysers of up to 5MW deployed across Germany could help balance its grid using only excess renewable energy.

And the kicker? Doing so could help avoid required grid expansion costs of between 7-8% per year.

Cutting fossil fuel demand response

The important thing is that we don’t just need grid balancing; we need low-carbon grid balancing.

Typically, making up shortfall involves “peaker plants”, fossil fuel power plants that ramp up to deliver additional electricity at times of high demand – but also delivering CO2 and NOx emissions.

Greener options to aid power balancing do exist, such as pumped hydro, batteries, flywheels and supercapacitors, but also come with limitations in geography, scale, space or storage horizons.

And grid balancing isn’t just about making up for less energy if the wind drops or sun doesn’t shine, it also involves dealing with electricity when there’s too much of it. Green hydrogen can help there.

Green hydrogen balancing today

One of the most important balancing roles green hydrogen can play is seen in “sector coupling”, which involves the integration of energy supply and end-use sectors – e.g, renewables and industry.

When renewables produce more electricity than the grid needs, this excess energy can be used by electrolysers to create green hydrogen for industry instead of wasting it through energy curtailment.

For example, Lancium, a US client of our certified partner H2 Core Systems, is already doing this with a system for dynamic grid load management that contains our AEM Electrolysers.

When too much electrical energy is in the grid, the flexible electrolysis workload is increased to create more hydrogen and decreased when too little energy is present. This approach supports both grid stability – assisting in the prevention of power outages and grid damage that could occur due to excess electricity – and enables the production of cheap, regenerative green hydrogen. Lancium’s approach, planned to be expanded to a multi-megawatt level, shows how power balancing can also derive the large amounts of green hydrogen needed by industry or even heavy mobility.

Fittingly, this sector coupling method is also proposed in the RLI research on German grid balancing.

A question of flexibility

The other main approach goes by the less elegant name of “power-to-gas-to-power” – essentially making green hydrogen from intermittent renewables and then using it to generate electricity.

Green hydrogen is attractive for long-term or seasonal energy storage since properly stored H2 doesn’t dissipate over time and can balance out periods of low renewables generation.

Although round-trip efficiency losses pose challenges for its use in short-term storage, these can be overcome by deploying H2 alongside batteries or combining it with heat capture to boost efficiency. The latter can be seen in the DESIGNNETZ Project in Ibbenbüren, Germany, where an electrolyser uses wind energy to provide flexibility to the grid all year. The hydrogen it produces is mixed with natural gas and used to generate electricity in a combined heat and power (CHP) unit.

By using waste heat from both electrolysis and the CHP to preheat the plant’s natural gas, the round-trip system efficiency for this green hydrogen grid balancing system reaches 75%.

Although CHPs have lower emissions than traditional fossil fuel peaker plants, they still release carbon. Green hydrogen can also be combusted directly without any CO2 emissions, while systems that emit only water are also possible by using fuel cells to reconvert green hydrogen into electricity.

To see how the latter can work, check out the InnovaHub District emerging in the Netherlands – an energy powerplant for residential districts that balances the grid by drawing on AEM Electrolysers.

Electrolyser technology for H2 grid balancing

The widespread use of green hydrogen for grid power balancing faces a range of challenges that need to be addressed, from policy roadblocks through to questions of cost. Another is ensuring that electrolysers can operate flexibly enough to use the fluctuating renewables when needed.

Alkaline electrolysers are not as flexible as technologies such as AEM or PEM Electrolysers in response to fluctuating energy sources, and less likely to satisfactorily respond to variable loads.

Since our AEM (Anion Exchange Membrane) technology is as flexible as PEM systems and we predict our megawatt-scale electrolysers will be cheaper than PEM equivalents, we believe we can meet this challenge.

Beyond this, the design of our AEM Multicore lends itself to optimum use of fluctuating electricity: it’s a highly-modular system with many electrolyser stacks that can ramp up and down separately. This delivers system flexibility of 3-105%, unlocking the exact level of hydrogen production needed.

Sized at 1MW for each system, decentralised use of such electrolysers can make a difference.

The Balancing act

Looking beyond positives like cutting grid expansion costs, creating green fuels, and, of course, stabilising grids with ever-larger renewables share, hydrogen grid balancing has further potential.

For example, Energy Innovation’s technical expert Eric Gimon believes it could also create “a valuable feedback loop whereby demand for cheap electricity drives flexibility, in turn facilitating installation of new variable clean energy with positive reliability spillovers.” This would mean that renewable projects can sell power at a discount to hydrogen hubs when demand is low (or make their own hydrogen) and then sell power to utilities when demand is high.

Leading to a more reliable grid, additional renewable electricity and mass green hydrogen energy.

We’re looking forward to seeing it – and importantly, working with pioneers to help make it happen.

If you’re investigating green hydrogen for grid balancing solutions, reach out for an obligation-free budgetary quotation for the AEM Multicore (or EL 4.0 Electrolysers for smaller pilot projects).