Most of the components of modern wind turbines are cast in ductile iron with nickel added into the casting process so the turbine resists low temperatures

Meeting the material challenges

The Nickel Institute

There is no shortage of proposals, or indeed a single solution, on how to address climate change. Solar, wind or nuclear will not be sufficient to replace coal and oil. Efficiency alone will not improve fast enough. Sequestration will not bury enough CO₂. It is a combination of multiple, varied efforts which will reduce greenhouse gas emissions on the scale needed to avoid disastrous climate change impacts.

Many technologies require specialised materials that withstand extreme environments or catalyse chemical reactions. The selective use of nickel-containing alloys and chemicals can provide a cost-effective solution. Nickel is already used in clean energy and fossil fuel technologies of today – and can be tomorrow.

Integral to renewables

Most of the components of modern wind turbines – the shafts, rotor hubs, gears and base plates – are cast in ductile iron. Nickel is added into the casting process to ensure the turbine resists low temperatures which sometimes reach -20°C. It is one of the few elements that strengthens the iron casting without making it brittle. A single turbine, composed of 45 tonnes of iron castings, contains close to half a tonne of nickel.

Solar energy is becoming more widely used globally, but two challenges remain. Energy created in the day needs to be stored for night use and to be dispatched elsewhere. Both of these problems may be solved by coupling molten salt with concentrating solar power (CSP).

CSP technology concentrates the sun’s power to create steam which turns a turbine to make electricity. Molten salt is used as a heat-storage medium that retains thermal energy very effectively over time. It remains in a liquid state throughout the plant’s operating cycle – even at temperatures greater than 500 °C, the temperature reached by the most efficient steam turbines. Nickel-containing stainless steel tubes, valves and vessels are used throughout the CSP system to provide resistance to the corrosive properties of the salt.

	Construction of Concentrating Solar Power (CSP) technologies depends on nickel-containing stainless steel for its ability to resist corrosion from the circulating molten salt

Ethanol, from corn, sugar cane or wheat, is an increasingly common alternative biofuel. One particular second-generation biofuel, cellulosic ethanol, can be produced from any plant material, including grain, straw, grasses and trees, and even municipal waste.

Cellulosic ethanol is popular because it reduces greenhouse gases by 85% over petroleum-based fuels. However, these plant materials require a variety of pre-treatment processing before they can be converted into a useful form of ethanol. This can involve harsh environments and corrosive materials – a common pre-treating agent is sulphuric acid. The production equipment that handles this must be extremely durable and corrosion-resistant. Nickel-containing stainless steels and higher nickel-containing alloys are preferred materials.

Enthusiasm for nuclear power has risen and fallen. It was popular in the 1970s and, in recent years with the threat of climate change, there has been renewed interest. Nuclear power plants contain numerous components made of nickel-containing stainless steel and nickel-base alloys, used primarily for their strength and resistance to corrosion. A typical reactor uses up to 20 different nickel alloys – for components such as the internal elements of the reactor, tubes in the steam generator and piping for coolants and heated water.

Improving the present

Coal is the largest source of energy for electricity generation with worldwide consumption at more than six billion tonnes annually. It is also one of the largest sources of CO₂ emissions. Carbon capture and storage (CCS) technology can capture CO₂ emitted from burning coal in industrial plants and prevent it entering the atmosphere. One option is mineral carbonation, or simply put, fixing CO₂ in the form of inert minerals. However, the corrosive carbonation reactions occur at higher temperatures and pressures, necessitating the use of corrosion-resistant nickel alloys.

High temperature fuel cells promise clean, efficient energy in sufficient quantities to power cities. But, so far, they have been too expensive for widespread use. Low-temperature fuel cells are already found in laptops and buses, but they produce relatively little power. In contrast, high temperature solid oxide fuel cells (SOFCs) can generate the power promised. And their heat can be channelled into other uses, such as heating buildings or turning steam turbines. Nickel is used in the fabrication of the anode in the high-temperature SOFC fuel cell. Given its thermal expansion properties and relative low cost compared to noble metals, nickel is key to enabling this technology and, potentially, its widespread deployment in the next twenty years.

The Nickel Institute
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