How sleeping giants could defeat the dunkelflaute doldrums

Dunkelflaute is the German word for ‘dark wind lull’ – those flat, grey days of winter, when solar and wind energy drops dramatically.

As a Daily Telegraph article revealed, on November 5 dunkelflaute weather meant wind farms could only meet 3-4% of UK electricity demand during peak demand periods. Gas, nuclear, biomass and imports made up most of the difference.

November also saw the publication of the National Energy System Operator’s (Neso) Clean Power 2030 report, calling for a massive increase in solar, onshore and offshore wind capacity, plus battery storage. Nuclear must increase, while reliance on gas must decline, it says.

Fair enough, given that 2030 is barely five years away. Strategic energy initiatives take longer than that. But where are the UK’s longer term options for uninterrupted clean energy that are not as directly weather-dependent as wind and solar, or reliant on batteries?

We could go on about pumped water storage, flywheels, phase change material heat stores, but here are some others to consider:

Let’s get boring

The Netherlands has a ‘Master Plan for Geothermal Heat’ that is projected to deliver 5% of the country’s heating needs by 2030 and 23% by 2050 – including up to 50% of energy used by its massive horticultural industry. That’s a lot of green energy from a 100% inexhaustible, 24/7 source.

The UK by contrast has virtually no geothermal strategy in place, despite several locations being identified as far back as the 1970s oil crises as having suitable geological conditions for energy extraction.

Only in 2023 did Britain’s first major geothermal power project since 1986 open, at the Eden Project in Cornwall. The £24 million initiative delivers water at 85^oC from a 4,871 metre bore hole, providing heating for the site’s energy-hungry biomes, as well as offices.

As Sir Tim Smit KBE, Co-Founder of the Eden Project, said: “Geothermal is the sleeping giant of renewables: lying not under our noses, but literally under our feet.”

Other ‘deep’ geothermal installations include a highly successful district heating and cooling scheme in Southampton, with a 1,800 metre bore hole serving several city centre building complexes and 1,000 homes. Apart from these, there is enormous untapped potential nationally for ‘shallow’ geothermal installations, in the form of super-efficient ground source heat pumps. The deeper we bore, the hotter it gets.

Time for tidal?

Next up, tidal energy has a projected potential to deliver 11% of the UK’s electricity demand from sources which are independent of weather and 100% predictable. Projects like the Swansea Lagoon and Severn Barrage have been shelved over cost and environmental issues. But continuing advances in the development of seabed-mounted turbines and underwater kites are steadily tipping the cost/benefit in tidal’s favour.

Unlike geothermal, tidal initiatives are even attracting some significant government support.

Hydrogen’s giant future

Without doubt, the existing technology with the most dramatic potential to transform the energy ecosystem is green hydrogen. With virtually unlimited availability, ease of production and use, flexibility of transportation and storage, it could almost single-handedly defeat the dunkelflaute doldrums without reverting to fossil fuel backup generation.

The case is simple enough. Ramp up wind and solar to produce lots of hydrogen by electrolysis, when renewable generation is in surplus. Then store and distribute it to where it is needed to produce electricity, heat and motive power, either by burning it or regenerating fuel cells.

Geothermal and tidal power are indeed among several sleeping giants lurking in the energy landscape. But hydrogen must be the most environmentally friendly, powerful and easy to awaken of them all.