HomeWaste Heat Recovery System (WHRS / WHR) Made Simple: 2025 Update

Waste Heat Recovery System (WHRS / WHR) Made Simple: 2025 Update

August 28, 2025

Your main engine throws away more energy in hot exhaust than you think. A WHRS taps that “free heat” to make steam or electricity, powering auxiliaries, heating, or even spinning a small turbine generator, so the ship burns less fuel for the same work. Steam-Rankine WHR is already standard on many large container ships, and modular ORC add-ons are now being rolled out through new 2025 partnerships.

🧪 What is it and Keep it Simple...

Waste Heat Recovery System (WHRS) means using engine heat twice. Instead of letting hot exhaust drift away, the system captures it to make steam or electricity, so your auxiliaries and heating need less bunker fuel.

  • Where the heat comes from: Main engine exhaust, jacket water, and scavenge air coolers pass through an exhaust gas economizer or boiler (EGE/EGB) to raise steam or hot water.
  • What it feeds: Hotel or process steam, fuel heating, and on larger setups a steam turbine generator that produces electrical power.
  • ORC option: An Organic Rankine Cycle module can turn lower temperature waste heat into electricity without a full steam plant.
  • Real world impact: Documented cases show meaningful cuts in fuel and CO₂, with vendors citing double digit percentage reductions on suitable duty profiles.
  • What it is called onboard: WHRS or WHR for the overall system, the heat exchanger is the exhaust gas economizer (EGE/EGB), the power add on is a steam turbine generator (STG) or an ORC unit.
  • When it shines: Long, steady steaming at medium to high loads, such as liner trades, where waste heat is abundant and consistent.
Waste Heat Recovery System (WHRS / WHR) — Advantages and Disadvantages
Category Advantages Disadvantages Notes / Considerations
Fuel and emissions Cuts auxiliary generator load and total fuel; documented savings up to low double digits on suitable duty profiles Savings shrink at low engine loads and short voyages OEMs cite up to ~14% on the right profiles; many ships see ~5–10%
Energy sources captured Exhaust gas via EGE/EGB, jacket water, scavenge-air coolers Limited by available temperature and flow Large two-stroke and diesel-electric applications benefit most
Outputs Steam for heating/process, power via steam turbine generator, or electricity via ORC module Steam plants add complexity; ORC adds working-fluid handling and extra heat exchangers Steam Rankine common on large container ships; ORC retrofits growing
Integration and footprint Newbuilds can reserve space and routing Retrofits need space for economizer surface, turbine/ORC skid, piping, controls Check exhaust backpressure limits and access for cleaning
Operations profile Best on long, steady passages at medium to high load Less effective with frequent maneuvering and variable loads Liner trades and long-haul bulk/tanker routes are strong candidates
Maintenance Mature service ecosystem for EGE/boilers/turbines Soot and deposits raise fire risk and pressure drop; needs regular cleaning Track ΔP across EGE; adopt soot-fire prevention procedures
Reliability and safety Well proven; no impact on propulsion if isolated correctly EGB fires are a known hazard; poor water quality and corrosion reduce life Install interlocks, bypasses, drains, and fire detection on uptakes
Controls and automation Power management can optimize between steam use and electrical generation Complex logic and tuning needed to avoid hunting and wet-stacking Integrate with PMS/EEMS for verified savings and CII reporting
Capex and economics Newbuild integration lowers lifetime cost; ETS exposure improves payback Retrofit capex and downtime can be material; payback depends on fuel price and load profile ORC targets lower-temp heat with modular skids; steam yields higher where space allows
Class and compliance Recognized by class; supports EEXI, CII and ETS strategies Extra documentation for boilers, pressure parts, and safety systems Engage class early for EGE sizing, materials, drains, soot-blowing regimes
Summary: WHRS turns wasted engine heat into useful steam and power. Steam Rankine systems are proven on large ships. ORC modules expand options for lower-temperature heat and retrofits. Results depend on load profile, economizer cleanliness, and good controls.

⚗️ 2025 WHRS Rundown

  • Proven in service: Large container ships use steam-based waste heat recovery to capture exhaust energy for propulsion and onboard power, with reported fuel cuts on the order of ten percent on flagship classes.
  • Savings potential: Major OEM documentation cites up to about 14% fuel and CO₂ reduction on suitable duty profiles. Typical results are lower and depend on load profile and cleanliness.
  • How much power: Steam WHR plants can deliver electrical output up to roughly 12% of main engine power on some installations, offsetting auxiliary generation.
  • ORC retrofits in 2025: Goltens and Orcan Energy announced a global partnership to engineer and install modular marine ORC systems that turn low-temperature engine heat into electricity.
  • Known risks: Exhaust gas economizers can accumulate soot. Fires are a recognized hazard and require monitoring of pressure drop, cleaning routines, and correct procedures.
  • Where it shines: Long, steady steaming at medium to high load provides abundant waste heat for reliable recovery. Techno-economic studies and recent reviews support the strongest cases on such profiles.

🧮 Waste Heat Recovery — ROI, Payback & NPV

Estimate the business case for steam-Rankine WHR or ORC retrofits. Use a preset or edit inputs.

Scenario
Fuel & ETS
Costs
Fuel saved (t/yr): —
CO₂ avoided (t/yr): —
Fuel savings (USD/yr): —
ETS cost avoided (USD/yr): —
Annual OPEX (USD/yr): —
Net annual benefit: —
One-time off-hire cost: —
Payback period: — years
NPV (— yrs): —
Abatement cost (USD/tCO₂): —

Assumptions:

  • “Typical” steam WHR fuel saving often falls in the 5–10% range on steady, high-load routes; marketing claims can cite up to ~14% on ideal profiles.
  • ORC modules usually target lower-temperature heat and deliver smaller savings than full steam plants, commonly a few percent on suitable vessels.
  • Order-of-magnitude CAPEX examples: very large container ship steam WHR can be around the low eight figures per ship; bulk/tanker steam WHR lower; ORC retrofits often in the low-to-mid seven figures depending on size and scope.
  • EU ETS exposure (share of voyages under ETS) and allowance prices materially affect payback.
  • OPEX typically includes maintenance, cleaning, water treatment, inspections, monitoring, and minor spares; a simple rule-of-thumb is a few to several percent of CAPEX per year.
  • Off-hire during installation is a one-time cost that should be included up front with CAPEX when calculating payback and NPV.
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