ORC technology is a very relevant solution to reduce fuel consumption on ships. Enertime held a conference at the National Maritime School of Marseille (ENSM) on the subject.
The implementation of ORC machines on ships aims at recovering heat from exhaust fumes and replacing the engine cooling systems to produce power. Enertime estimate that this solution could increase engines' efficiency by 5 to 8% with a Return on Investment of 3 to 5 years at present cost of fuel.
The advantages of ORC technology in this context are:
- The opportunity to recover low temperature heat
- Simple operation and easy maintenance of the modules
- The small size of the module which is easy to install even in closed and limited spaces
Various cases have been studied to confirm the performances announced.
Here are two examples:
- A ship with diesel-electric propulsion system running at 15 MW as base load using gas-oil and thermal power rejected in the fumes at 5 MW.
Power production from an ORC modules will reach 800 kWe of power corresponding to 3.5 tons/day of fuel savings for an investment cost of 3 US$/W and a return on investment of 3 years for a cost of fuel at 900 US$/ton and 300 days of operation.
- A ship running on heavy fuel oil with a slow propulsion engine delivering 15 MW and equipped with auxiliary diesel generators plant with 3 generators of 300 kW each, including one on standby.
Waste Heat Recovery: 3 tons of steam/hour with 1 to 1.5 used for fuel pre-heating.
Power production from an ORC module will reach 200 kWe.
Recovering the energy used to cool the engines could produce an additional 100 kW and allows stopping one auxiliary diesel generator.
ROI: 4 to 5 years
On a long-term basis, numerous opportunities exist to increase the performances of ORC marine applications:
- To use sulfur-free fuel with clean exhaust gases would allow more off-gas cooling, therefore recovering heat sources at lower temperature and generating 30 to 40% more for both heat and power.
- To improve turbine performances will help increase efficiency.
Using transcritical cycles will help increase efficiency further compared to the cycle used today.