Some industries are almost impossible to decarbonise completely. If we are to achieve net zero, residual emissions from the likes of cement, chemical and steel manufacturing need to be counterbalanced by the active removal of CO2 from the atmosphere. This is where negative emissions technologies (NETs) come in –to ‘suck’ greenhouse gases out of the air to compensate for their ongoing release within the most challenging sectors.
What level of negative emissions is needed? Estimates for the UK vary from 30 to 130 megatons of CO2 per year, the equivalent of between 10 and 37 per cent of current annual emissions.
There is, however, Government recognition of the potential value of NETs, with up to £100 million of innovation funding and a £1 billion carbon capture, utilisation and storage (CCUS) fund. The latter will equip two of the UK’s major industrial clusters with infrastructure for capturing, transporting, and storing CO2 by the mid-2020s, with two more clusters targeted by the end of the decade.
Maximising Carbon Capture
Since 2014, Hampshire-based Bluebox Energy has been developing ultra-low carbon combined heat and power (CHP) solutions for homes, business parks and agriculture. CHP is an energy-efficient technology that generates electricity and captures the heat that would otherwise be wasted to provide thermal energy.
Bluebox Energy’s technologies include a new method to convert heat to electricity using a hot air turbine which takes in filtered air and compresses it in a turbo-compressor. This air is heated using energy from a hot gas stream, such as flue gas from the combustion process. The hot pressurised air then passes through the turbo-compressor and power turbine to produce electricity.
The electrical output from the turbine generator is converted to grid power in a dedicated inverter. The air emerging from the power turbine is still at a temperature of around 400°C so can be used for heating, steam production or direct drying.
In 2019, Ricardo and Bluebox Energy began to explore the potential of biomass pyrolysis as an ultra-low carbon solution. Biomass is renewable organic material such as wood and crop waste; pyrolysis is the decomposition of that organic material at a high temperature in an inert atmosphere.
“a new method to convert heat to electricity using a hot air turbine which takes in filtered air and compresses it in a turbo-compressor”
The charcoal that results, known as biochar, can be used as animal feed or to enrich soils. The carbon in the biochar is very slow to break down, which means the carbon it absorbed from the atmosphere while it was still biomass is locked up for hundreds or even thousands of years.
As Jonathon McGuire, Chief Executive Officer of Bluebox Energy, explains: “This project perfectly combines the expertise of Bluebox Energy and Ricardo. First, we had Bluebox Energy’s concept of capturing 50 per cent of CO2 in biochar (resulting from pyrolysis using a hot air turbine CHP system) with the other 50 per cent released into the atmosphere. Second was Ricardo’s belief that most of the 50 per cent emitted could also be captured using chemical absorption.
“Achieving this would allow us to capture 90 per cent of the remaining emissions and, as a result, increase the overall CO2 capture to 95 per cent of total emissions.”
Attracting Carbon Credits
A current drawback of most negative emission technologies is that they are only considered viable for large-scale emission sources such as power and industrial plants. Earlier this year, however, Ricardo and Bluebox Energy won funding through the Net Zero Innovation Portfolio to design a greenhouse gas removal system that could operate at a community scale.
Known as BIOCCUS, the system works by taking sustainably sourced waste wood from domestic timber production and then processing it in three ways: producing biochar; generating heat and power; and capturing and storing the CO2. The technology captures up to 95 per cent of the CO2 absorbed by the trees; commercially marketable biochar can be used in farming; and the CO2 can be deployed for low-carbon concrete. All of which attract valuable carbon credits that can be traded.
This first phase of the project lasts until December 2021 and could potentially lead to the consortium being selected to develop a prototype and demonstrate the technology between 2022 and 2024. Ricardo is leading the design of the CO2 capture system.
“Ricardo is aiming to become a world leader in integrating carbon capture with pyrolysis-based CHP systems for community-scale applications,” says Dr Gareth Milton, Chief Engineer with Ricardo Automotive and Industrial EMEA Division.
“This system shows how we can achieve negative emissions while generating revenue streams for industry and local communities through waste heat and sequestered carbon products. What’s more, an organisation could use decarbonised or net-negative CHP technology to improve its own environmental impacts.
Providing a Zero Carbon Alternative
Ricardo is part of a consortium aiming to connect solar electricity generation directly to the railway network and provide zero carbon power cheaper than from the grid.
“Plugging solar directly into the railways opens up opportunities to use renewable energy technologies in ways not previously possible” says Ivan Stone, CEO of Riding Sunbeams
“At its core,” he continues, “this is a simple idea. But you have to remember: it had never been done before.”
A Case Study in Rail
Four years ago, recalls the chief executive officer of Riding Sunbeams, experts from the Energy Futures Lab at Imperial College London, Community Energy South and electrical engineering specialists Turbo Power Systems gathered trackside near Aldershot station in Hampshire.
“We were there to find out whether it was possible to install a solar farm close to an electrified train track and, instead of connecting to the grid like a conventional solar array, create a direct link to the track to provide traction power for the trains.” The answer was: yes.
The experiment proved that the grid could be bypassed completely. Thus was born Riding Sunbeams’ mission to find an unsubsidised route to market for community energy and to decarbonise railways – Britain’s largest electricity consumer – in a way that would also maximise social benefit. “Railways and solar photovoltaics (PV) are,” says Stone, “a match made in heaven.”
Alternatives to Carbon
Transportation is responsible for around one-fifth of global carbon dioxide (CO2) emissions. Within this sector, rail is among the most efficient and lowest emitting modes, according to a report, ‘The Future of Rail’, published in 2019 by the International Energy Agency.
Rail accounts for eight per cent of the world’s passenger movements and seven per cent of freight transport yet uses just two per cent of transport energy demands. Three-quarters of total rail passenger movements and half of rail freight rely on electricity, making it uniquely positioned to take advantage of renewables.
Projects around the world are showing that low-carbon energy alternatives do exist and are no less efficient. Ricardo provided safety case development and certification for the mainline test of the UK’s first hydrogen powered train, HydroFLEX [see RQ Spring 2021], while Indian Railways has equipped nearly 60 passenger coaches with solar panels to supply light and fan power since 2017.
The station at Guwahati in Assam is 100 per cent solar powered and solar PV installations are planned at 8,500 more stations in the coming years. Similar projects are underway in Australia and Argentina.
Founded by climate charity Possible and Community Energy South, the aim of Riding Sunbeams is to take solar potential a significant step further, in the belief that direct supply to rail traction systems opens up opportunities for decarbonising metro, tram and railway systems everywhere. Ricardo has been working with Riding Sunbeams since 2019 on solutions for systems at each stage of the proposition.
Overcoming Technical Challenges
Thirty per cent of railways are currently electrified, using either a third rail parallel to the track carrying DC power or overhead AC or DC cables. Cost is a significant factor to electrify the remaining 70 per cent; Riding Sunbeams not only provides clean power, but it also reduces cost.
Deploying solar energy to power railways faces a number of technical challenges. Two-thirds of the UK’s existing electrified routes – and all plans for new rail electrification – use AC overhead lines to power trains. Most of the electrified train lines around the world do likewise.
The technology needed to provide lowcost power conversion from renewables to AC rail traction systems has not previously existed. Ricardo is part of the Riding Sunbeams-led collaboration, working with Turbo Power Systems and Network Rail, that is seeking to show it’s possible to create a direct connection between renewables and AC rail networks.
“With Ricardo’s support,” says Stone, “we will be able to apply our low-cost, lowcarbon traction supply model to most of the electrified routes in the UK and around the world. This will also support lowcost electrification of some of the most challenging remaining diesel-powered lines. “Proof of capability will bolster our attempts to enter the traction power supply market as a small and medium-sized enterprise with an innovative value proposition that can be applied in the UK and many other countries.”
A study commissioned by Indian NGO Climate Trends and Riding Sunbeams and conducted by Ricardo Energy and Environment has found that a direct supply of solar energy to Indian Railways, without the need to connect via the grid, would save almost seven million tonnes of carbon per year. It could also potentially power at least one in four trains on the national network.
Making a World-First Connection
In 2019, the team successfully demonstrated a direct connection between solar PV panels and the DC third rail traction system. That summer, a test unit of just over 100 panels was installed next to the track at a demonstrator site outside Aldershot station. Named ‘First Light’, this was the first time in the world that renewable zero carbon electricity had been directly supplied to an adjacent rail line without causing either system to malfunction.
The 30 kilowatts peak (kWp) unit was connected to an ancillary transformer on the traction system of Network Rail’s Wessex Route, with the energy captured from the panel array used to power signalling and lights. Ricardo provided its expertise in power generation research and experience of connecting renewable energy technologies to existing DC third rail infrastructure.
“this was the first time in the world that renewable zero carbon electricity had been directly supplied to an adjacent rail line without causing either system to malfunction”
“Taking our idea off the drawing board and onto the tracks was a pivotal moment,” adds Stone. “We’ve shown that plugging solar directly into the UK railways can be done safely and without disruption to train services and opens up opportunities to use renewable energy technologies in ways not previously possible. “At the same time, we have been gathering electricity demand data from potential community solar farm sites in the south of England. By putting this real-world data together, we’ll be able to work out how to plug in much larger solar arrays to power trains in future.”
The model allows transport system operators to buy competitively priced low carbon energy directly from a community solar farm. Riding Sunbeams estimate that each megawatt (MW) of solar capacity connected to the rail traction system will deliver annual savings of around 245 tonnes of carbon dioxide equivalent (CO2e).
Projects in the Pipeline
Late last year, Riding Sunbeams secured funding from Thrive Renewables and the Friends Provident Foundation to develop a pipeline of new renewable energy projects in South East England and South Wales. This was followed by a £2.5 million award from the UK government’s Getting Building Fund to build a 4 MW solar farm in East Sussex which will directly power the main line railway between London and Eastbourne. Ricardo contributed feasibility insights, including financial models for delivery of the solar farm, and options for the electrical connection between the solar farm and the railway. This project will become operational in mid-2022.
Riding Sunbeams’ work has informed Network Rail’s Traction Decarbonisation Network Strategy as well as the Department for Transport’s Transport Decarbonisation Strategy. It could ultimately see one in every ten UK trains running on energy direct from the sun. The projects have also helped to inform both Transport for London and HS1’s new tender processes to procure renewable traction energy direct from lineside generators.
Last year Riding Sunbeams completed a new feasibility study with Transport for Wales for direct supply to 25 kV AC overhead electrified routes, looking at the potential for community solar to power the South Wales Metro.
“Community energy – where local people own the renewable energy and benefit from it – is at the heart of this work,” says Stone. “We want to provide a commercial route to market for community energy groups looking for new projects to develop and connect them to regional rail network operators like Network Rail who will pay a fair price for their power.
“Our mission is to see community- and commuter-owned solar farms powering the railways – for the benefit of the railway routes, the communities that host them and of course the planet. Get on board – here comes the sun!”