Made: Energy-generating coatings

Industry and university researchers are uniting to create buildings that make their own energy from the structure itself

What: Energy-generating coatings
Where: Specific pilot plant, Port Talbot 

A building that can act as its own power station? Whose every external surface has the ability to generate electricity from its very skin rather than through photovoltaics? Sounds slightly far-fetched, even in our sustainability-driven world, but it’s clear this idea has a lot riding on it – at least in south Wales. Just along from construction giant TATA Steel’s Port Talbot works and less than a month before the firm announced 600 job losses at the plant, business secretary Vince Cable and Wales first minister Carwyn Jones opened the Sustainable Product Engineering Centre for Innovative Functional Industrial Coatings’ (Specific) first pilot production plant. Its job is to bring forward the high performance coatings produced by university-based research for adoption on a mass scale – all in the hope of kick-starting a new £1bn industry and generating 10,000 new construction jobs.

The pilot plant is the product of an initiative which, says Specific research director Professor David Worsley, aims to plug the gap between university research and industry and manufacturing. Central and local government has sunk £20m of funding into the Specific project, matched with industry know-how and manpower from TATA, NSG Pilkington Glass and BASF. The job is to create a electrically conductive coating that can be economically applied to both steel and glass, developing huge possibilities for energy generating cladding.

Specific research director and  Swansea University professor of engineering David Worsley (left), and Specific industry director, TATA Steel’s Paul Jones.
Specific research director and Swansea University professor of engineering David Worsley (left), and Specific industry director, TATA Steel’s Paul Jones.

Paul Jones, industry director for Specific, has been seconded from TATA to bring commercial nous to academic innovation. ‘A scientist will want to create the most efficient system, but my job is to optimise processes so they’re fit for industrial scale roll out and suitable for the market,’ he says. ‘We’re here to strike the balance between the amount of energy that can be created from the coating and the upscaling of the process for a production line’. The aim is to perfect a coating that, while half as effective as a standard PV panel, can cover the building facade and costs far less per square metre. 

‘TATA makes 100 million m2 of steel composite cladding a year and NSG Pilkington 200-300 million m2 of glass, and just 10% of this could generate as much energy as a peak load nuclear power station,’ says Worsley. ‘The material bends, so architects will be able to form energy generating curved panels,’ he adds. The potential, and its rewards, are enormous.

Developing the all-important conductive coating involves constant iteration between laboratory conditions, where the properties of the conductive material are ascertained, and the pilot plant, where application to metal and glass panels and drying techniques are being developed to see whether they can be translated into factory scale processes. Economies of industrial production are not generally allied with laboratory environments, as lab techniques often use processes and chemicals that are inconsistent with large-scale production. Materials used in manufacture have to be cheaply available, economic to make and non toxic. 

Other factors also come into play. One team is working on battery technology, analysing the surfaces that will store the accumulated energy from cladding panels for future use. Another is looking at how coatings can be formed of precision-engineered particles with a surface area 5000 times greater than the surface it sits on; a third at how these surfaces can be pulled up like stalagmites from the substrate to radically increase the range of sun angles they remain effective in. One specialist team is looking at the generation of thermoelectric energy through temperature differentials across two surfaces of a composite panel, technology that was first used on the space shuttle programme.

Perhaps all this blue sky thinking has driven Specific’s plans to generate real-world applications on site – notably with cladding its own factory. Meanwhile this fusion of academia and industry continues to learn how to live together. ‘This is innovation at the sharp end,’ says Worsley, conceding that this open-ended research does not sit easily with the traditional results-based thinking of industrialists. ‘But they’re coming around to the thinking that if you can plan for it, then you’re not dealing with a breakthrough technology.’


1. PV Coatings Pilot Plant

TATA’s interest in the development of thermodynamic and electroconductive coatings for steel started in 2008. The high quality and long product warranties of its steel sheets offered potential for manufacturing cladding that could have ‘functionalised’ surfaces. The photovoltaic conductive compounds mixed with dyes – the most efficient of which are brown tinted (pictured left) are being developed and tested in the laboratory. But they also have to make manufacturing and economic sense in the pilot production facility across the road from the lab, where the aspiration is for 20 tonne reel-to-reel coils of steel rather than batch processes. While the pilot line is a ‘clean room’ facility, it does not reach the levels of those seen at, for instance, silicon wafer manufacturing plants – and this distinction is important in production terms. Here, the aim is merely to minimise the coating’s exposure to debris, which on the finished glass or metal sheet could potentially create a ‘short circuit’.

2. Lab testing: Coating efficiency

Since the darkest, most heat absorbent surfaces are the best electrical generators, black would be the most efficient. But black is a problematic colour for a glazed panel, so organic dyes were introduced to the compounds, which, while reducing efficiency, increase marketability. Brown and purple are efficient, but NSG Pilkington wants to concentrate on blue prototypes as it currently sells far more blue than brown glass. Red and yellow dyes, with lowest conductivity, are also being looked at for their appeal to the commercial market. Coating degradation is analysed over time in the lab to assess longevity under long-term exposure to sunlight.  

3. Screen printing

Four fundamental pieces of equipment in the pilot plant  facilitate the potential full-scale application of the conductive material on a panel’s surface. These allow them to be screen printed or coated, with a prototype industrial dryer and a unit for special high temperature treatment if necessary. Two production lines can fit in the space, one of which is currently producing coated steel and glass sheets of around 1m2. This time next year it is hoped a 2m wide reel unit will be installed, increasing speed of production. Any developments will be subject to production efficiencies, economics and any designs’ likelihood of market uptake.

4. Roller Coating

The two main units are a flat bed screen printer printing patterns and contacts in the electroconductive medium – but with limited capacity for single sheets – and a roller coater. Both are suitable for coating glass and are off-the-shelf machines. Depending on the substrate, coating layers typically range from 5-100 microns, but layer consistency is key. Too thick and resistance can build up and cause electrical loss through heat generation; too thin and conductivity disappears. The team is looking for the ‘sweet spot’ where thickness and consistency optimise electrical conductivity. The production line is also geared up for future ink jet printing.

5. High temp treatment

Once screen printed or coated, sheets pass through an oven on a conveyor. The speed at which the sheet is passed through it dictates the drying temperature, with slower movement producing a higher sheet temperature. Glass and metal heat up at different rates, which also affects conveyor speed. The surface treatment unit is a bespoke piece of equipment that uses high intensity light to generate a 500°C blade of heat, requiring 300kW of heat energy to be directed over a small area of the panel via high-voltage units (right). A factory can replicate these temperatures, but they are an order of magnitude above standard production line processes.