Stainless steel AISI 316 grade in the production of renewable energy

By Srikumar Chakraborty, ex ASP/SAIL, Freelance Consultant

Introduction

A large proportion of the greenhouse gases that blanket the Earth and trap the Sun’s heat are generated through the burning of fossil fuels to generate electricity and heat. Fossil fuels, such as coal, oil, and gas, are by far the largest contributor to global climate change, accounting for over 75 per cent of global greenhouse gas emissions and nearly 90 per cent of all carbon dioxide emissions. The science is clear: to avoid the worst impacts of climate change, emissions need to be reduced by almost half by 2030 and reach net-zero by 2050. To achieve this, global need is to end our reliance on burning fossil fuels and invest in alternative sources of energy that are clean, accessible, affordable, sustainable, and reliable.

The good news is that the growth in clean energy seems unstoppable. According to reports, wind and solar power generation are poised to surpass that from nuclear power and hydropower sources.

Renewable energy sources

Renewable energy refers to energy derived from a natural source that won’t run out or is self-replenishing, and usually has a low or zero-carbon footprint. Examples are wind power, solar power, bio-energy (organic matter burned as a fuel) and hydroelectric, including tidal energy.

These energy sources are available in abundance all around our planet. Today, around 29 per cent of electricity currently comes from renewable sources which is accelerating the transition to clean energy as a pathway to a healthy, livable planet.

The role of 316

Wind power is the largest producer of renewable electricity in both the UK and the US. Onshore and offshore wind farms generate electricity by spinning the blades of wind turbines. The turbines convert the kinetic energy of the spinning blades into electric energy by turning a drive shaft and gear box, which is connected to a generator. Electricity is then converted into higher voltages and fed into the national grid. Common parts of a wind turbine include the rotor blade & pitch control system, the yaw system (to adjust and orientate the wind turbine), nacelle (turbine housing), gear box, generator & control system, rotary union, slip ring, lighting protection etc. Stainless steel grade 316 is a common choice for metallic parts.

Solar power is one of the planet’s most freely available energy resources, which you might assume would make it the number one source of renewable energy. But of course, the amount of sunlight we get can vary greatly depending on location, season and time of day. Solar power generates electricity by capturing sunlight on solar panels in a joint chemical and physical reaction, known as the ‘photovoltaic effect’ (or PV). Common parts of a solar power unit are the panel, inverter, module mounting Structure, cables, battery. Again, stainless steel grade 316 is often used for the metallic items.

Hydropower is created using the movement of flowing or falling water. Hydroelectric power plants are found at dams and generate electricity through underwater turbines that turn a generator. Hydro power also encompasses wave and tidal power, which rely on ocean forces to generate electricity at the mouths of large bodies of water, using similar technology. The main parts of a hydropower system include the dam or weir, reservoir, piping & ducts, turbine, generator & alternator, engine housing, transformer, transmission line etc. Stainless steel 316 is often selected for such systems. Corrosion resistance and durability make 316 a valuable choice for tidal and wave energy applications.

Bio-energy involves generating electricity by burning organic matter as a fuel source. These fuels are known as biomass and can include anything from plants to timber to food waste. Carbon dioxide is emitted when bio-energy is made, but these fuel sources are considered renewable because they can be regrown and absorb as much carbon as they emit across their lifespan.

Hydrogen production via electrolysis is another important component of the ‘renewable energy’ basket as it acts as a clean energy carrier. Excess electricity produced via solar or wind power can be used to electrolyze water. The hydrogen thus generated can be easily stored for later use. That includes producing electricity or use as a clean fuel in hard to abate sectors. Stainless steel 316 is an ideal material for electrolyzers. Given hydrogen’s rising prominence as an energy carrier, stainless steel’s involvement in its production is pivotal in manufacturing industries looking to replace heating by fossil fuels.

Characteristics of 316

This grade emerges as an indispensable and ideal catalyst for the renewable energy revolution. With beneficial properties such as corrosion and heat resistance, strength, hardness, endurance, and aesthetic appeal, it plays a role throughout renewable energy generation, transport and storage. Stainless steel is preferred in clean and sterile environments as it is simple to clean and does not corrode. Austenitic stainless steel grades, particularly AISI 304/304L and 316/316L, are ideal for equipment and components in renewable energy systems thanks to their remarkable characteristics and adaptability.

Whilst the entire austenitic family of stainless steels is corrosion resistant, among all the grades in the 300 series, stainless steel 316 is comparatively the best material for the renewable energy industry. It has proven its worth in both offshore and onshore wind power energy generation as well as in various solar applications, from thermo-solar systems to photovoltaic cells. It is particularly useful in flexible substrates for thin-film solar cells. These substrates provide a stable base for the photovoltaic material, enhancing the cell’s durability and flexibility, essential for various architectural applications.

Table 1: Comparison of the chemical and physical properties of 304 and 316

Comparing 304 and 316

Corrosion properties: both stainless steel 304 and 316 are very corrosion resistant but the addition of molybdenum in 316, increases the grade’s ability to withstand harsh environments (see Table 1). It is therefore often referred to as marine-grade suitable for use in marine environments that are more aggressive than ambient. PREN (Pitting Resistance Equivalent Number) 304 is 17.4-20.8, that of 316 is 22.3-28.5. Stainless steel 316 has good resistance to oxidation in intermittent service to 870 °C and in continuous service to 925 °C. However, continuous use at 425-860 °C is not recommended if corrosion resistance in water is required. In this instance 316L is recommended due to its resistance to carbide precipitation.

Where high strength is required at temperatures above 500 °C, grade 316H is recommended.

Machinability: 316 steel has a machinability rating index of 60, while 304 has a rating of 70. (Ref: AISI Standard)

Process metallurgy: the melting temperature of stainless steel 304 is 1400-1450 °C while 316 melts at 1375-1400 °C. Both 304 and 316 are melted in EAF/IF, refined in AOD, with the liquid steel processed through the Concast route as bloom/ billet, finally rolled as long products such as bar and pipe in a rolling mill. A limited number of components are precision forged in close die followed by heat treatment.

Fabrication: 304 and 316 both possess unique and beneficial properties, hence comparing the two grades is as timeless activity no matter what the intended usage. However, when choosing from a comparison of 304 and 316 stainless steel for use in a renewable energy project, this author maintains that 316 is best choice based on an understanding of its properties. The benefits of 316 stainless steel include its high corrosion resistance in acidic, alkaline, and chloride environments due to the higher nickel content and additional 2% of molybdenum. It is also flexible, machinable, and weldable making it another top material for rapid prototyping. Finally, note that 316L filler metal is the appropriate choice for welding 316 austenitic stainless steels.

Global scenario

Global renewable electricity generation is forecast to climb to over 17,000 terawatt-hours (TWh) by 2030, representing an increase of almost 90 per cent from 2023. To provide perspective, that would meet the joint power demand of China and the United States in 2030. Notable advances have been made in China in the past two decades, so much so that China is currently the single largest generator of renewable energy. In 2023, renewable energy accounted for 35 per cent of China’s electricity requirements, with hydro the largest single source of clean power at 13 per cent. In Europe, more than EUR 584 billion of investment is needed this decade to achieve the Fit for 55 target of deploying 42.5 per cent renewable power into the grid by 2030, according to the European Commission. Worth noting is that Germany is the world’s third country when ranked by installed total wind power capacity.

Finally, renewable energy in Japan made up 21.7 per cent (2,189 TWh) of the total power supply in FY2022. New policies are being introduced to ensure the FY2030 target is reached.

Conclusion

Renewable energy generation to realise environmental and economic benefits has become the prime responsibility all over the world. Generating renewable energy does not produce greenhouse gas emissions and hence contributes to reducing air pollution. Other benefits include a diversified energy supply and reduced dependence on imported fossil fuels. Stainless steel 316 and renewable energy are reliant on each other for high performance and long lasting equipment. From pipes, nuts and bolts, to heat exchanges, tanks, pumps, flanges, turbines and gaskets, stainless steel can be found in nearly any part of a power generation plant Stainless steel 316 is an alloy that is durable, long-lasting, strong, corrosion-resistant and easy to clean. 316 stainless steel is therefore a serious asset to the power generation industry, both in traditional scenarios and in renewable energy. There is no doubt that stainless steel 316 has a vital role in helping to provide a safe, sustainable solution for the production and distribution of energy.

About this Tech Article

Appearing in the August 2025 issue of Stainless Steel World Magazine, this technical article is just one of many insightful articles we publish. Subscribe today to receive 10 issues a year, available monthly in print and digital formats. – SUBSCRIPTIONS TO OUR DIGITAL VERSION ARE NOW FREE.

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