Fluid mechanics
and the energy

Decarbonisation of the energy system is the greatest challenge we face. At Cambridge’s Institute for Energy and Environmental Flows, world-leading researchers in fluid mechanics, thermodynamics and surface science are working to develop the solutions we need to replace fossil fuels and protect our planet.

After an extremely hot, dry summer in the UK, where records were broken once again, many of us are realising that climate change isn’t some far-off possibility: it’s already here. To protect our planet for current and future generations, we need solutions now.

There is hope, however: there are options in all sectors to significantly reduce carbon emissions. Huge cost and efficiency improvements in wind and solar power are building up the renewable supply of electricity, but the associated intermittency requires substantial energy storage infrastructure to replace the gas-fired power stations which cushion against this intermittency.

Other industries, such as global shipping, aviation, cement, fertiliser, and iron and steel require radical solutions, including the possible use of hydrogen and carbon capture and storage technology.  

“We need to transition our economy to low carbon sources of power as a matter of urgency,” said Professor Andy Woods. “Universities like Cambridge are working hard to develop the science and technology to underpin this industrial revolution, in collaboration with industry.”

Woods is Director of the Institute for Energy and Environmental Flows (IEEF). The Institute was established at Cambridge in 2000, and was originally known as the BP Institute. The IEEF’s researchers work with academic and industrial collaborators from around the world, using fluid mechanics, thermodynamics and surface science to help with some of the major challenges for decarbonisation including geological carbon storage, superfast battery charging, efficient building heating systems and lubricants which reduce drag.

Developing solutions with industry

The Institute’s researchers also study ocean mixing dynamics, focusing on the timescales of carbon storage, and environmental challenges including avalanche dynamics and explosive volcanic eruptions, as well as the fluid mechanical processes controlling the melting polar ice.

The Institute collaborates on energy transition projects with energy companies, including BP and Shell, who are investing heavily in the energy transition, including the development of wind farms, carbon storage reservoirs, geothermal energy extraction, and hydrogen production: all of which are key components of a decarbonised energy system.

“Direct collaboration with industry ensures we can contribute to the critical technical challenges associated with these energy solutions,” said Woods. “For example, our work on carbon storage is helping address both the regulatory and environmental challenges to ensure safe geological storage, and to maximise the efficiency of the infrastructure needed for carbon storage.”

Storing CO2 underground

According to the latest IEA and IPCC projections, to reach the 1.5°C target of the Paris Agreement by 2050, the world needs to capture and store between 7 and 8 gigatons of CO2 per year, nearly one-quarter of present global emissions. This will be sourced from cement, iron and steel, and fertiliser production as well as from the emerging industry of direct air capture, including biofuels. Currently, just 40 megatons of carbon are stored per year.

“The transition between megatons and gigatons is enormous: the carbon storage industry needs to increase by a factor of 200,” said Woods. “We will need thousands of carbon injection wells and subsurface reservoirs by the middle of the century if we’re going to reach the Paris targets.”

Safe storage of CO2 at depths of 1-2 kilometres beneath permeable layers of rock is a major research area at the IEEF. Researchers are studying how CO2 migrates through deep porous rocks to establish the storage capacity of different geological systems, and how the CO2 becomes safely trapped.

Researchers are also exploring approaches for monitoring the migration of CO2 and for optimising the injection strategy. “This work is having a direct impact on the development of new storage sites, through close collaboration with industrial operators,” said Woods.


Lowering emissions in Cambridge

IEEF researchers are also working on improving access to geothermal energy through the use of long-reach horizontal wells, through which water flows by buoyancy forces as it recovers heat from the subsurface. There are numerous technical challenges associated with such systems, and they are closely related to some of the challenges for inter-seasonal heat storage.

Significant amounts of waste thermal energy can be stored below ground over the summer and recovered in winter. Such approaches have enormous potential within heat pump schemes. Woods, a Fellow at St John’s College, has been working with IEEF researchers to develop a plan to reduce the College’s carbon emissions associated with heating and powering its historic buildings.

The College plans to replace all its gas heating on the main site with high-temperature heat pumps. These heat pumps require a source of thermal energy, and IEEF researchers are exploring the relative merits of using the River Cam, extracting heat from boreholes on the Backs or using air heat exchangers.

“Based on the technology we’ve got right now, we estimate we can reduce the carbon emissions of St John’s College by about 45 percent,” said Woods. “The main reason we can’t reduce it any further is that the electricity supply in the national grid has a carbon intensity of about 220 grams per kilowatt hour, and the heat pumps are powered by this electricity. As the electricity system becomes decarbonised, the associated carbon emissions of our heating system will fall.”

IEEF researchers are also working to improve superfast battery charging systems by speeding up the removal of associated waste heat; working to improve the performance of wind turbines by developing new lubricants that can withstand the extreme conditions inside turbines, thereby preventing wear but also reducing drag; and working to retain the CO2 stored in peatlands while preserving farming capacity, through management of the water table.

“The researchers at the IEEF are working incredibly hard to develop solutions to support the energy transition, in collaboration with the companies who will help deliver that transition,” said Woods. “This is an exciting time for the University and through pioneering research and collaboration we can make a material impact in building a zero-carbon world.”

Images of IEEF experiments (top to bottom):

1. Laboratory model of a hot air plume in a building
2. Visualisation of the separation of particles from a fluid in a particle-driven flow
3. Experimental model of a bubble mixing system used for destratification of reservoirs
4. Viscous fingers which can develop as CO2 displaces water in a saline aquifer 

Images by Dr Nicola Mingotti

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