CCS: Will the U.K. ever capture the moment?

In this month's issue of Professional Engineering (the publication of the IMechE), there's an interesting overview of the U.K's stalling plans towards Carbon Capture & Storage (CCS). In 2007, the Department Of Energy & Climate Change (DECC) launched a competition to build the U.K.'s first demonstration CCS plant, a competition that, as various entrants pulled out in the midst of the economic crisis, was won by default as much as merit by Longannet in Fife. That came to an underwhelming, if predictable end last October, as it was announced that the scheme would be scrapped, under crippling financial concerns primarily over the cost of piping required to transport the captured CO2 to the North Sea.

It is immensely frustrating when you consider that the U.K. has so much in place to become global leaders in CCS. On the geological side, there's the extensive experience of oil and gas drilling in the North Sea. In terms of technical knowledge, the U.K. has, in the likes of Cambridge and Imperial, some of the key academic institutions looking into both the array of capture technologies and the modelling of geological storage. And whilst CO2 is more corrosive than natural gas, the U.K.'s existing gas pipe network means that the infrastructure is, at least in part, in place.

Plants such as Longannet also provide a part of that infrastructure; the most developed capture technologies, such as solvent-based capture, are predominantly post-combustion, which means that they are retrofittable to existing plants. This introduces a significant efficiency penalty to the plant (somewhere around a third of the standalone plant's thermal efficiency is typical), but steadily-advancing technologies such as Chemical Looping Combustion, whereby the use of metal oxides to provide oxygen for combustion makes CO2 separation an inherent part of the process, may eliminate such penalties for future new-builds.

There is light at the end of the tunnel. Last December saw the £21 million CO2 capture installation at Ferrybridge power station in West Yorkshire go online. This post-combustion project works by capturing the CO2 from the flue gas in an absorbing column using solvents before heat-assisted regeneration of the sorbent, and the resultant release of the captured CO2. A joint project between SSE, Doosan Power Systems and Vattenfall, the demonstration plant captures 100 tonnes of CO2 per day, equivalent to 5MW of the plant's 2000MW capactiy; there's no storage of CO2 at this stage, but the project will provide extremely valuable insight into the handling of hot flue gases which will inform potential future CCS projects, such as that in Peterhead jointly helmed by SSE and Shell, which may come into operation as early as 2016.

Whether the capture technology is post-, pre- or oxy-fuel combustion, retrofit or new-build, the costs of CCS are substantial. But with the relative readiness of the technology, and its ability to integrate readily with existing infrastructure, it's hard to imagine, new nuclear builds aside perhaps, another technology that can readily take such a big chunk out of the U.K.'s CO2 emissions than CCS.

Fast Reactors - the answer to the U.K.'s stockpiles?

Prof David Mackay, Cambridge University Professor and Chief Scientific Advisor to the Department of Energy & Climate Change (DECC) has suggested that a new generation of fast reactors might offer the solution for dealing with the U.K.'s stockpile of nuclear waste, and further sweeten the deal for the U.K.'s potential nuclear renaissance. According to Mackay, the transmutation and subsequent fission of a stockpile which currently comprises 100 tonnes of plutonium and 35,000 tonnes of depleted uranium could provide the U.K. with 500 years of low-carbon electricity.

Unlike conventional thermal reactors, fast reactors do not use neutron moderators to reduce the velocity of released neutrons, a technique used to help sustain the fission reaction for uranium 235-rich fuel. These high-speed neutrons are more suited to the conversion of plutonium and other waste material, and the final waste product has a much shorter half-life than the original stockpile, thus providing relief to the substantial issue of waste disposal, as well as the nagging concern over terrorists plundering the stockpile for weapons-grade plutonium.

The favoured design is GE Hitachi's Prism Reactor, which started life as a U.S. government-funded research project. The commercial plant would be much smaller than a typical plant, producing around 311 MWe. A non-moderating coolant with a high heat capacity is required; multiple loops of liquid sodium would be used to transfer the heat from the reactor to a steam generator to power a turbine. Given the compact size of the reactor, multiple reactors could be combined; the present scheme proposes a pair of Prism reactors to be installed in place of the now defunct MOX (Mixed Oxide) Plant at Sellafield.

Fast reactors are less proven and more difficult to harness than the more commercially popular thermal reactors, but GE Hitachi insist that with the latest passive safety systems, reactor meltdowns such as that of Fukushima last year are a virtual impossibility.

Full article on the Guardian website.