The UK’s Carbon Trust has released £1 million of funding for seven new carbon technology projects. Meagan Ellis investigates the processes behind three of these projects.
The Carbon Trust, an independent company funded by the UK Government to support the development of low carbon technologies, has announced £1 million worth of funding for seven low carbon technology projects, ranging from novel LEDs and natural ventilation systems to biomass energy generation.
The Carbon Trust Applied Research scheme requires each project to pass a thorough application process. The winning applicants had to show genuine innovation and the potential to help substantially reduce UK greenhouse gas emissions.
Horizon Ceramics Ltd, based in Penrith, UK, was awarded just over £114,000 for its plans to transform kiln construction.
Traditional kilns used for ceramic firing have a high thermal mass, making them energy intensive. Over the past 20 years, attempts have been made to construct kilns from ceramic fibre blocks in order to reduce their mass and improve insulation. But these fibres degrade over time, leading to airborne hazardous fibrous dust and structural integrity losses.
Horizon is attempting to produce interlocking hollow ceramic modules that are sufficiently load bearing to be self-supporting without requiring superstructures.
‘The idea for interlocking modules came from construction used to build “lead castles”, which are used as protection against radiation in nuclear and medical physics experiments,’ explains Professor Ron Jones of Horizon. ‘The modules have grooves on two adjacent edges and the opposite [extensions] on the other two edges, so they interlock on all four edges [see image below]’. By varying the shape, the kiln can be constructed entirely from the modules.
The key requirement for an interlocking system of ceramic modules is accuracy, which can be problematic, as ceramics will sometimes shrink by up to 25% after firing, so no two parts are the same. To overcome this, Horizon has developed a manufacturing process called ‘freeze casting’ whereby the hollow modules are filled with a low density (200-300kg/m3) foamed ceramic of the same composition as the outer structure (silica, sillimenite or alumina). This near-net shape method of manufacturing is free of distortion or shape changing.
‘The materials being used for module construction have been thermally cycled in many other refractory components over five years and show excellent stability against thermal shock and fatigue,’ says Jones. The thermal mass of the kiln is expected to be around 70% lower than monolithic refractories. ‘Our calculations indicate that there can be up to a 60% energy saving compared to many conventional kilns.’
Scaled units of the kiln have been built, and Horizon is drawing up designs for a test kiln that can operate in a production environment.
Making a splash
The automotive paint shop is a major consumer of energy and a producer of volatile organic compounds. According to a 1994 report from the US Department of Energy, an assembly plant’s paint system consumes 260kWh per car.
The Warwick Manufacturing Group at the University of Warwick, UK, received £250,000 from the Carbon Trust for their project which aims to do away with the automotive paint shop. The Group estimates that between 45 and 90t a day of carbon dioxide could be saved by removing the need to paint plastic components in the conventional way.
Their novel approach involves ‘exploding’ paint directly into a moulding tool during plastic injection. A precise quantity of paint is sprayed into a mould with a nitrogen carrier gas under very high pressures and in a short time period – a matter of milliseconds. The plastic is then injected into the mould, where it is evenly coated.
‘By blasting [rather than injecting] into a mould, [the paint] covers the whole surface in a random way, such that we have complete coverage but no flow lines,’ explains Dr Gordon Smith, Principal Research Fellow with the Warwick Manufacturing Group. ‘It’s a bit like if you dropped a bag of flour – the flour would go everywhere.’
The process is clean, as there are no emissions associated with it, there is no additional energy input at the injection stage and there is no need for post-mould coating. And, says Smith, the technique can easily be incorporated into automotive assembly plants.
The method works with solid and metallic paint, but researchers are hoping to extend the technology to any type of paint – pigmentation or mica. At the moment, the technique is only being developed for plastic parts, but Smith would like to see it used for metallic ones as well.
‘One of the interesting things that we came up with was that the paint not only forms a uniform thickness over the complete surface, but it is also a very thin coating – down to 20 microns,’ says Smith. ‘This potentially gives us the opportunity [to] build up the paint rapidly. If we want a thick coating, we can shoot the paint in repetitively – it takes no more than milliseconds. We can [deposit] many layers of paint, or different kinds of paint – a clear coat [and then] a coloured coat. We could [also] build up new types of coatings which might be layers of sensors.
‘We’re still at the early stage of testing, but the possibilities are quite exciting.'
Researchers at Coventry University, UK, have received £150,000 to develop a technique to reduce the amount of energy used in aluminium smelting, which consumes 4.98tWh of electricity in the UK each year.
For electrolysis to be sustained, the anode and cathode must remain separated by the electrolyte. During electrolysis, electric current fluctuations can cause ripples on the surface of the aluminium pool. ‘In effect, these are interfacial gravity waves, modified by the external magnetic fields, which pervade the cell,’ explains Professor Sergei Molokov, Director of Coventry’s Applied Mathematics Research Centre. ‘When a certain stability threshold is exceeded, these waves can grow by absorbing the energy from the ambient electric and magnetic fields.’
In order to suppress these ripples, a constant DC magnetic field is applied. But to guarantee the continued operation of the cell, a minimum electrode separation must be maintained. The greater the electrode separation, the greater the resistance of the cell, and the more electricity consumed.
Researchers at Coventry have mathematically modelled the most essential features of the electromagnetic process to better understand the basic mechanism underlying these ripples.
Through this investigation, the team has proposed a better way to control the suppression of ripples by applying a powerful AC magnetic field on the cell. ‘The determination of the amplitude/frequency spectrum on the imposed magnetic field is the essential part of the invention. Analytical investigations, as well as numercial simulations using idealised models of the cell, have confirmed the basic idea,’ says Molokov. ‘The numerical model is based on the so-called shallow-water approach, taking advantage of the fact that the ratio of the thickness of both aluminium and cryolite layers is smaller than the horizontal bath dimensions.
'In other words, we’re trying to induce a wave to counter and suppress the unstable wave.’
By this method, it may be possible to achieve lower electrode separations and electricity consumptions, and thus reduce carbon dioxide emissions by 10% or more.
Coventry University is working with the University of Warwick to design, build and commission a model cell in which smelting performance and energy consumption will be evaluated in the presence of applied dynamic AC magnetic fields of different frequencies and amplitudes. A major developer and vendor of aluminium smelting technology will also evaluate the technology by running a series of production oriented tests.
The next call for proposals for the Carbon Trust will open on 15 October.