Growing global energy demand must be balanced with the need to reduce emissions, improve efficiency and provide secure, reliable energy. Achieving this requires a diverse mix of renewable energy, nuclear power, efficient thermal generation, energy storage and emerging low-carbon technologies.

Stainless steels contribute across this energy system. Their corrosion resistance, strength, durability, temperature resistance and ease of fabrication make them suitable for equipment exposed to water, seawater, aggressive process media, high temperatures and demanding operating conditions.

Correctly specified stainless steel can extend equipment life, reduce maintenance requirements and improve reliability. These benefits are especially important in installations that operate continuously or are difficult and costly to access, including offshore wind turbines, geothermal plants, hydroelectric turbines and nuclear facilities.

Renewable energy technologies convert energy from biological materials, sunlight, wind, water and heat below the Earth’s surface into useful electricity, heat or fuel.

The operating environments vary considerably. A biogas plant must withstand corrosive compounds created during anaerobic digestion. Offshore equipment is continuously exposed to seawater and salt-laden air. Solar thermal equipment must transfer and store heat efficiently, while geothermal systems may handle hot, mineral-rich and chemically aggressive fluids.

Stainless steel provides different benefits in each application. These may include resistance to corrosion and abrasion, hygienic surfaces, efficient heat transfer, mechanical strength, durability and reduced maintenance.

Biogas is commonly produced from organic materials such as wastewater sludge, manure, agricultural waste and by-products from food processing. The material is fed into anaerobic digesters, where bacteria break it down and produce a gas containing methane, carbon dioxide, water vapour and residual gases.

The process combines renewable energy production with organic waste treatment. The biogas can fuel an engine connected to a generator, producing both electricity and heat. It can also be cleaned before being introduced into a gas distribution system or compressed for other uses.

Biogas production creates a challenging environment for materials. Hydrogen sulphide, ammonia, organic acids and other process compounds can cause corrosion. Avoiding equipment failure is particularly important because restarting a digester can be a long and delicate process, while organic waste continues to arrive at the plant.

Stainless steel applications in biogas plants

Properly specified stainless steels can be used in Anaerobic digesters and fermenter tanks, Feed and reception equipment, Hygienisation and pasteurisation equipment, Pumps and valves, Agitators and mixing equipment, Screw pumps, Pipes and fittings, Heating and cooling systems, Biogas drying units, Gas-cleaning and purification equipment and Storage equipment.

Stainless steel digester tanks can be constructed from comparatively thin plate and assembled using a relatively simple lifting system. Publications identify shorter construction times, reduced logistical requirements, gas and water tightness, resistance to hydrogen sulphide and ammonia, easier maintenance and residual material value as potential advantages.

Stainless steel pipes also offer small bending radii and better heat transfer than plastic alternatives. This can be useful where the pipework forms part of the digester’s heating or process-control system.

Biofuels, combined heat and power, and gasification

Stainless steels are also used in the production of bioethanol and biodiesel, where equipment is exposed to demanding chemical and process conditions. Their corrosion resistance, strength, ductility, toughness and ease of fabrication make them suitable for processing and storage equipment. Applications described in the renewable-energy publication include hoppers, pretreatment steam systems, processing vessels and stripper or rectifier equipment.

Combined heat and power plants generate useful heat and electricity from the same fuel. Gasification systems can convert wood residues, municipal waste, used tyres, plastics and other materials with a useful calorific value into synthesis gas for use in an engine or turbine. Stainless steels can be used in parts of these facilities requiring resistance to heat or corrosion.

Solar energy can be used to produce hot water, provide heating and cooling, or generate electricity. Stainless steel is used in both solar thermal and photovoltaic systems.

The material is particularly valuable where thin sections, reliable heat transfer, corrosion resistance, hygiene and long outdoor service life are required. It can be formed into tubes, sheets, tanks, absorbers and architectural components, allowing the energy-generating function to be integrated into the building.

Solar water-heating systems

Direct thermosiphon systems use the natural movement of heated water. Solar radiation heats fluid in the collector, and the warmer, less dense water rises towards the storage tank. Cooler water then flows back towards the collector, creating a natural circulation process.

Stainless steel can be used for both the inner water tank and its outer shell. The inner tank remains in contact with domestic hot water and therefore benefits from stainless steel’s hygienic surface and corrosion resistance. The outer shell protects the tank and its insulation from atmospheric exposure. Higher-alloyed stainless steels can also be selected for more aggressive coastal environments.

Indirect pressurised systems are used where frost protection is required. A separate fluid containing an antifreeze agent circulates through a closed primary circuit, transferring heat to the domestic water through a heat exchanger. Thin corrugated stainless steel tubes support effective heat transfer while providing the mechanical strength required to withstand operating pressure.

Solar absorbers and collectors

Stainless steel can be made into thin absorber panels that transfer solar energy directly to a circulating fluid. In stainless steel cushion absorbers, only a thin sheet separates the solar radiation from the fluid. This compact design reduces the distance across which heat must be transferred.

Applications in solar thermal systems include Inner and outer shells of hot-water tanks, Heat exchangers, Thin-walled and corrugated tubes, Connectors and fittings, Glazed cushion absorbers, Unglazed roofing panels, Frames for thermal collectors, Fasteners and mounting components and Solar cooling equipment.

Photovoltaic systems

Stainless steel can also support the direct conversion of sunlight into electricity. Applications include flat and tilted roofs, architectural solar façades, mounting systems and fasteners. Thin stainless steel foil can serve as the substrate for flexible photovoltaic cells, allowing modules to be incorporated into roof and façade elements.

Building-integrated solutions demonstrate how the material can provide weather protection, structural support, architectural expression and a surface for energy generation. Existing worldstainless case studies include a solar façade in Bursins, Switzerland, a photovoltaic roof at the German Nautical Museum in Stralsund and stainless steel absorber panels at a housing development near Madrid.

Cooling accounts for significant energy use in buildings and in commercial and industrial activities such as food handling. Conventional cooling systems generally use an electrically powered compressor.

Adsorption chillers offer an alternative approach in which heat drives the cooling process. The heat can come from solar thermal installations, industrial processes or another available source. Stainless steel contributes to the heat-transfer equipment at the centre of these systems, helping transform available heat into useful cooling.

Potential applications include adsorption chiller components, heat exchangers, cooling circuits, solar thermal interfaces, hot- and chilled-water pipework and industrial heat-recovery systems.

This is an important link between renewable energy and energy efficiency. Instead of generating additional electricity to operate a conventional compressor, a thermally driven system can make use of heat that is renewable or would otherwise remain unused.

Hydroelectricity is an established source of renewable power. Micro hydro systems extend the principle to smaller rivers, streams, water networks and industrial flows. They can provide distributed energy generation in rural or remote areas and can also recover energy from downward fluid flows in industrial processes.

Different turbine types are selected according to water flow and the available head:

• Pelton turbines for high heads and lower flow
• Kaplan or propeller turbines for low heads and higher flow
• Francis, Turgo and crossflow turbines for intermediate conditions

Components in continuous contact with water require corrosion resistance, while moving components must also resist wear and cavitation erosion. Water can strike components at high speed in impulse turbines, while Kaplan and Francis turbines must handle high flow rates.

Stainless steel applications in micro hydro turbines

Applications include turbine runners, guide vanes, pelton turbine nozzles and needles, wear rings, rotors, housings and casings, shafts, gates and flow-control components, fasteners and water-contact fittings.

Martensitic stainless steel grades were identified for runners, guide vanes, nozzles and wear rings, and austenitic stainless steels for housings and casings. More corrosion-resistant austenitic or duplex grades can be considered where the operating environment requires them.

For remote installations, dependable materials can be particularly valuable because access, inspection and repair may be difficult.

Offshore wind equipment must operate in an environment characterised by seawater, salt spray, wind, movement and restricted maintenance access. Durable materials can help reduce the frequency of maintenance and repairs.

Stainless steel can be used in electrical boxes and enclosures, fasteners, davit cranes, safety cables, braided hoses and fittings.

Further opportunities may exist in access systems, cooling and hydraulic circuits, cable-protection systems and other components requiring a combination of mechanical performance and corrosion resistance.

Floating offshore wind extends generation into deeper waters where fixed-bottom foundations may not be practical. It also introduces movement, fatigue and more complex mooring and cable systems. Stainless steel applications should be assessed against the specific mechanical, fatigue and corrosion requirements of each component.

Geothermal energy uses heat from below the Earth’s surface for electricity generation, district heating, greenhouse heating, fish farming and building heating.

Geothermal fluids may contain chlorides, fluorides, sulphates and other mineral compounds. High-temperature geothermal sources can also produce aggressive superheated water. Corrosion-resistant materials are therefore needed to support reliable operation.

Stainless steel applications in geothermal systems

Identified applications include condensers, flash units, filters, heat exchangers, pipes, pumps, valves, pump shafts and district-heating equipment.

Enhanced geothermal systems seek to access heat at greater depths. The resulting conditions can place additional demands on well components, surface equipment and heat-transfer systems.

Heat pumps provide another way to use the energy stored in the ground. Stainless steel applications include heat exchangers and protective external frames for equipment exposed to weather.

Nuclear power generation depends on the reliable operation of systems and components under tightly controlled conditions. Material selection must consider temperature, pressure, radiation, water chemistry, corrosion, mechanical loading, fabrication and the safety classification of the installation.

Stainless steels are used where their combination of corrosion resistance, mechanical performance, fabricability and surface properties meets the requirements of the particular system.

Potential applications include process and cooling-water piping, tanks and vessels, heat exchangers, condenser tubing, pumps and valves, fuel-handling equipment, nuclear fuel reprocessing equipment, waste-handling equipment, liners, supports and selected structural components.

Technical publications are available covering material selection for nuclear fuel reprocessing facilities, the performance of materials in reactor environments, corrosion issues in nuclear power plants and the design of safety-related steel structures in nuclear facilities.

Because nuclear applications are safety-critical and highly regulated, the appropriate material and fabrication requirements must always be determined for the specific system and applicable technical standards.

The energy transition increasingly depends on technologies that convert, store and transport energy, not only on those that generate electricity.

Hydrogen production

Electrolysers use electricity to split water into hydrogen and oxygen. Depending on the electrolyser design and operating environment, potential stainless steel applications include frames and structural components, selected bipolar and separator plates, water-treatment equipment, pipes and fittings, pumps and valves, heat exchangers, pressure vessels, compression equipment, hydrogen storage and refuelling installations.

Material selection must consider the electrolyte, electrical potential, operating temperature, pressure and susceptibility to hydrogen-related damage.

Battery production and energy storage

Battery energy storage helps manage variations in renewable electricity generation and demand. Stainless steel opportunities exist particularly in battery manufacturing, process control and thermal management.

Applications can include mixing and process vessels, chemical-handling systems, production-line equipment, water-purification equipment, cooling circuits, temperature-control equipment, fire-protection systems, structural supports and fasteners.

Thermal energy storage

Energy can also be stored as heat for subsequent use in buildings, district heating networks, concentrated solar installations or industrial processes.

Potential stainless steel applications include hot-water tanks, storage vessels, heat exchangers, process pipework, pumps and valves, molten-salt equipment and industrial heat-recovery systems.

Renewable and low-emission fuels

Sustainable aviation fuel, renewable diesel, methanol and low-emission ammonia require processing, storage and distribution infrastructure.

Potential applications include reactors, process and pressure vessels, distillation equipment, heat exchangers, storage tanks, pumps and valves, transfer pipework and marine fuel-handling equipment.

The appropriate material depends on the fuel, process chemistry, pressure, temperature and impurities present.

Selecting the appropriate stainless steel

There is no single stainless steel grade suitable for every power-generation application. Selection should take account of:

• Temperature and pressure
• Chemical composition of process fluids
• Chloride and sulphide exposure
• General, localised and crevice corrosion
• Mechanical and fatigue loading
• Wear, abrasion and cavitation
• Hygiene and water-quality requirements
• Fabrication and welding
• Inspection and maintenance access
• Intended service life
• Applicable codes and technical standards

Specialist advice should be obtained before specifying a grade for a particular installation.