Marine waste heat recovery turns exhaust and cooling-water heat into electricity or shaft power, with full steam-cycle systems recovering about 5% of fuel energy and Siemens reporting fuel savings of up to 12% on container ships. Since 2024 the growth has shifted to modular organic Rankine cycle units and hybrid turbochargers that work at low load and suit retrofits.
What it is and how it works
About 25% of the fuel energy fed to a large two-stroke engine leaves through the exhaust, according to an ABB container vessel brochure. Marine waste heat recovery captures part of that energy, plus heat from cooling water, and converts it into electricity or shaft power. A full steam-cycle system (WHRS) pairs a dual-pressure exhaust gas boiler with a condensing steam turbine generator and an exhaust gas power turbine on the same generator; ABB says adding the power turbine more than doubles electrical output, that recovered electricity equals roughly 5% of fuel energy, and that recovery is typically around 10% of main propulsion shaft power (ABB).
Two newer approaches avoid the boiler and steam turbine. Organic Rankine cycle (ORC) units use a low-boiling working fluid to generate power from low-grade heat such as engine jacket water, HT cooling water and low-pressure steam. Hybrid turbochargers integrate a motor-generator on the turbocharger shaft to turn surplus exhaust energy into electricity.
Why it matters now
IMO GreenVoyage2050 notes that power-turbine and steam-turbine WHR cannot be fully utilised at engine loads below about 80%, so slow steaming eroded the steam-cycle case and confined it to very large container ships. Alternative fuels have reversed the economics for low-grade heat: every recovered kWh on a methanol or LNG ship displaces fuel costing far more than HFO, and EEXI and CII reward the gain.
Key players and products
ABB and Siemens supply steam-cycle WHRS. Alfa Laval's E-PowerPack is a self-contained ORC unit generating electricity from exhaust gas and lower-temperature sources such as jacket water; the company claims payback in as little as 2-3 years and EEDI, EEXI and CII benefits. Climeon sells the HeatPower 300, Orcan Energy offers skid-mounted ORC packages installed with Goltens, and MHI and Calnetix developed the Hydrocurrent ORC and the MET hybrid turbocharger (Calnetix). Accelleron, the former ABB Turbocharging, presented the ACCX300-L axial turbocharger at CIMAC 2025 and reports low ammonia risk to its turbochargers after material tests (CIMAC 2025).
Figures that matter
Siemens' WHRS reduced fuel consumption by up to 12% on UASC container ships, and ABB won more than USD 23 million of WHRS orders for fourteen container ships in 2013. Industry overviews put typical savings at 5-10% on suitable large engines and up to about 15% in favourable cases, with OEMs citing up to about 14% (ShipUniverse). MHI reported that its MET83MAG hybrid turbocharger could supply all of a bulk carrier's electric power in normal seagoing operation, and that its electro-assist turbocharger saves about 30% of electric power versus conventional auxiliary blowers (MHI). All of these are vendor figures, and no fleet-level WHRS adoption statistic was found.
| Metric | Value | Source type | Source |
|---|---|---|---|
| Fuel energy lost in two-stroke exhaust | about 25% | vendor | ABB brochure |
| Full WHRS electricity recovered | about 5% of fuel energy; about 10% of shaft power | vendor | ABB |
| Siemens WHRS fuel saving, UASC boxships | up to 12% | vendor | — |
| ABB WHRS orders for 14 container ships, 2013 | more than USD 23 million | vendor | ABB |
| Typical WHRS saving, industry overview | 5-10%, up to about 15% | trade-press | ShipUniverse |
| Load limit for full power-turbine use | about 80% engine load | regulatory | IMO GreenVoyage2050 |
| Alfa Laval E-PowerPack payback (claim) | 2-3 years | vendor | — |
| MHI electro-assist turbocharger saving | about 30% of blower electricity | vendor | MHI |
Developments 2023-2026
- Early 2025: Climeon completes commissioning of a HeatPower 300 on a container vessel and later commissions all units on a six-vessel HD Hyundai Heavy Industries newbuild series (Inderes).
- September 2025: Climeon announces a programme with Jiangsu New Yangzi Shipbuilding for a 13,000 TEU methanol dual-fuel container ship and delivers its first HeatPower system for a 2027 ship delivery; the unit recovers heat from jacket water, HT cooling water and steam (Climeon). A repeat order follows from NovaAlgoma Cement Carriers.
- November 2025: Orcan Energy and Goltens offer skid and split-skid ORC packages for retrofit in constrained engine rooms (MarineLink).
- ElectraTherm and the US Navy demonstrate a shipboard ORC on a 390 hp helicopter-turbine exhaust as proof of concept for fuel savings of up to 10% (ElectraTherm).
Outlook
Full steam-cycle WHRS remains a large-ship, high-load niche. The growth segment is sub-megawatt ORC on low-grade heat because it works at low load, fits retrofits and avoids boiler and steam-turbine complexity. Hybrid turbochargers and ORC compete for the same exhaust energy; on dual-fuel engines with lower exhaust temperatures and tighter turbocharger matching, low-temperature ORC looks the more robust choice.
