Carbon capture and storage: a risk worth taking?

The opening of a carbon capture pilot plant for research and training in central London this week suggests that some companies are preparing for the technology to become an important part of their business.


But the launch coincided with a report from the UK Energy Research Centre (UKERC) that reminds us just how many challenges still remain if we hope to use this technology to cut emissions while still burning fossil fuels


Though we are some way from setting up a commercial-scale carbon capture and storage (CCS) system in the UK and many engineering challenges remain in doing this, listening to the report’s authors makes it seem likely that the biggest barriers won’t be technical. In fact, plants with a total annual capacity of 35.4m tonnes of CO2 capture are already operating round the world.


Instead the report highlighted a huge range of uncertainties surrounding the political and economic development of CCS that could hinder or even kill its progress in the UK, from getting financial incentives right to sorting out who’s liable if CO2 ends up accidentally being released into the atmosphere.


With so many chances for costly error in a process that could tie us to a strategy for the next few decades, you can’t help but wonder whether it’s all worth it. Indeed, one of the comments made about my article on the pilot plant questioned what the overall benefits of CCS were once you take into account the additional energy use.


The problem in answering this question is the same problem faced by government and industry in trying to plan CCS’s development. We won’t really know all the answers until we build one of these things, a point keenly stressed by the report’s authors.


There are other reasons the UK should pursue CCS at this stage. If we are going to use a mixture of nuclear and renewables in the next few decades, CCS-fitted fossil fuel power stations could provide a sensible way of meeting demand when the wind doesn’t blow during peak times.


There’s also great potential in our empty North Sea oil fields to store carbon dioxide — something that most other European nations don’t have — and so it could become a source of income for the UK, as could the technology and expertise involved. And, as UKERC researcher Prof Stuart Haszeldine of Edinburgh University pointed out, you could argue the UK has a moral responsibility to clear up the mess of carbon emissions it started with the Industrial Revolution.


But perhaps the strongest argument is still that we need to trial CCS so that we have the best range of options available to us and can make the most informed decision about our energy future. Setting up an industry race between nuclear, renewables and CCS could help avoid rash commitment to costly vanity projects, said the report’s editor, Prof Jim Watson of Sussex University.


‘That idea of the race puts pressure on there to keep the costs down by saying it’s up to industry to choose which technologies make the most sense to meet the overall policy goals, which are emissions reduction, keeping the lights on, affordability etc. It’s not a policy goal that we must have CCS in the long run; it’s one of the suite of options there.’


For all the potential pitfalls, the report managed to propose a pathway to CCS success, drawing from examples such as flue gas desulphurisation technology and the development of nuclear reactors. But we need to take a long-term view and not close down options too early.


‘The race timescale is over decades. This is a marathon not a sprint,’ said Haszeldine. ‘So although government is trying to set out this competition between different technologies, they’re not all starting from the same starting line … There’s the possibility for technological failure to discover it really is a high cost but what the pathways also show is that there is plenty of opportunity for the government to mess it up on the way by making premature decisions.’


Listening to this, it’s no surprise that the researchers welcomed the government’s decision to start a new CCS competition after the failure of a previous one, this time opening it up to all technologies instead of focusing on a specific niche.


However, the next opportunity for a government mess-up is rapidly approaching, they argued, in the form of electricity market reform. A plan to provide the rest of the funding needed for the competition’s projects through energy bills needs to happen if companies are to get the financial backing they need.


But the detail has so far been thin and reforms have to be passed in enough time for companies to put their plans together for the competition, said Watson. ‘If they can’t get that coordination to work, the risk is you end up with no projects.’


This article first appeared on The Engineer.

Imperial's new carbon capture pilot plant opens for business

Superconducting cables head to the cities

Cold current: using superconducting cables to carry electricity within cities has many advantages, but the difficulties are also considerable

A steady stream of liquid nitrogen will next year begin flowing beneath the city of Essen in the Ruhr region of Germany. Its purpose: to cool the world’s longest superconducting cable, part of a trial to replace the city’s high-voltage transmission system with a safer, smaller and cheaper alternative.

Underground high-voltage cables are commonly used to carry 110kV of electricity or more beneath urban areas, connecting the national transmission grid to local distributions networks, where the voltage is reduced before entering people’s homes and businesses. But in the last 10 years a new alternative has emerged – implemented first in the US and due to be installed in Germany in 2013 – where superconductors are used to transmit energy at lower voltages using less material and requiring smaller trenches and fewer transformers.

A superconductor is a material that carries electricity with virtually no resistance when cooled to very low temperatures, usually below -200°C, meaning less energy is lost as heat. Some materials behave as superconductors at relatively higher temperatures and using these as electrical cables allows power to be cost-effectively transmitted at lower voltages, which would usually produce energy losses that were prohibitively expensive.

Superconducting cables can carry more current than conventional copper without generating magnetic fields

The €13.5m “AmpaCity” project in Essen will see German utility company RWE, working with cable firm Nexans and the Karlsruhe Institute of Technology, install a 1km underground high temperature superconductor (HTS) transmitting electricity at 10kV. Because it will connect to other medium voltage parts of the grid, it will allow RWE to reduce the number of urban transformer stations needed to step down the power from the long-distance transmission voltage of 110kV, freeing up valuable space in the city.

‘This makes the application of superconductors very attractive,’ said Mark Stemmle, project manager for superconducting cable systems for Nexans, which has designed the cable that will form the core of the AmpaCity project. ‘It’s not really an attractive application at the moment for areas in the country because normally you have a lot of space. But if you go inside the cities, you find there are often constraints in building space.’

Superconducting cables are larger than conventional power lines but only one is needed to carry the same amount of power as five traditional medium voltage cables. They don’t produce as much heat so need less insulation, nor do they create external magnetic fields, unlike conventional cables that can sometimes induce currents in adjacent underground pipes.

The smaller space needed for the cables frees up the distribution company to develop simpler network configurations, further reducing the amount of land used. A study the AmpaCity partners conducted last year found that a typical urban network of 20 transformers could be reduced to 15 using superconducting cables. Having fewer transformers is cheaper, and also reduces risks in the event of a fire in the city.

The study also found that superconductor cables – despite needing a flow of liquid nitrogen to cool them – would be cheaper both to install and run over a 40-year period than conventional high voltage lines, which require high levels of maintenance as well as the additional network infrastructure.

The smaller trenches needed for superconducting cables help reduce the impact of the installation

The superconducting cable Nexans will produce is the product of the company’s decade of experience since their involvement in the world’s first superconductor installation on Long Island in New York. It features three concentric insulated circles of cable made from bismuth strontium calcium copper oxide (BSCCO), cooled to 68K (-205°C) using liquid nitrogen that flows one way through the centre of the cable and back around the outside to be recooled. ‘The reason we chose this design is because it’s the most material-efficient and therefore also ­relatively cheap, especially when you look at superconducting material, which is quite expensive still,’ said Stemmle.

As well as enabling superconduction, the nitrogen cooling is also what allows the cable to use the concentric arrangement. It means you don’t need three separate wires (unlike conventional AC transmission systems) and cancels out the cables’ magnetic fields. But pumping two to three litres per metre of cable presents one of the biggest challenges. ‘Since you have the different flows of the liquid nitrogen within one cable, there’s also a kind of heat exchange between the inner and outer flow,’ said Stemmle. ‘So you need to make sure that works because otherwise the concept won’t work.’

The first superconducting cable was installed on Long Island, New York

Although the superconductor allows energy losses to be reduced enough to make medium voltage transmission cost-effective, it still leaks more energy than a high voltage cable would – it’s the reduced cost of installation and maintenance that makes it the cheaper option. This is because to reduce the voltage but maintain the power you must increase the current, which in this case leads to an estimated average 20 per cent increase in energy losses over a one-year period.

How does Nexans expect to reconcile this with the current pervasive trend for energy efficiency? ‘There’s a reason why they originally designed the grids like they did, with high, medium and low voltage, where you transport very large amounts of power at very high voltage,’ said Stemmle. ‘Even if you’re not really more efficient in terms of energy, you’re more efficient in terms of materials. It also depends on the loading: if you have high loading in the high voltage cable it could turn in favour of the superconducting cables.’

The cable is due to be installed by the third quarter of 2013 and its use studied for the following two years. ‘We’ve already showed in other projects that it’s technically possible,’ said Stemmle. ‘This project is important to demonstrate it in a real application, we are connecting two substations within a city and this has never been done before. I think this will help the technology to gain some more trust by the utilities, which most of the time are quite conservative.’

This will be vital if superconducting technology is to become more widely used in grid systems. In the UK, no utility firms have announced any plans for similar trials and National Grid sees the technology is not sufficiently advanced for longer distance transmission, although it says it is monitoring the situation.

‘If we look far in to the future, the trend we are seeing is that metals like copper and aluminium are getting more expensive and this will be an advantage for superconducting solutions because it can be even more cost-competitive,’ said Stemmle. ‘At the moment the cooling system is still quite expensive but as we use this type of system more and more you could have a totally new concept for a city grid because you could have three or four cooling systems shared between all the cables and this would increase the efficiency.’

This article first appeared on The Engineer.