Stena Line are seeking novel, cost-effective approaches to recover energy from exhaust gases from ship engines and transform into a more useful energy form (e.g. electricity to supply hotel loads onboard the ship).
What's the challenge?
The companies comprising the Swedish-based Stena Sphere represent one of the largest private shipping groups in the world. We are seeking solutions that can be applied to cargo and passenger ships that travel in all of the world’s oceans.
Currently, combustion engines onboard ships have an efficiency of 50% or less. If we consider a ship consuming 10000 tonnes of fuel in one year, less then 5000 tonnes is transformed into ”usable” energy.
These energy losses are primarily radiant heat loss and the sensible heat of exhaust gases. About 30% of the total energy available is lost through the exhaust gases. Typically, the temperatures of the exhausts are in the region of 250-350 degrees Celsius.
In the ideal case, we would like to convert a significant portion of this waste heat directly into electricity in a cost effective manner.
Also, a 1MW engine produces a mass flow of about 7 tonnes/hour. We would also be interested in approaches to transform a portion of the kinetic energy of this exhaust stream into electricity.
Do you have the solution?
Today there are different solutions for capturing the energy, but they are capital intensive, energy inefficient, and costly to maintain. As a result, interest in investment in these kinds of systems is limited in the marine industry.
Examples of known technology applied on ships are:
- Exhaust gas boiler that generate steam to drive a turbine
- Direct exhaust gas turbines
We are especially interested in industrial scale applications of Thermoelectric Generators (TEG) that use the temperature difference between the exhaust gas and the ambient air to directly transform waste heat into electricity
We would also be interested in efficient turbine systems that generate electricity from the kinetic energy from the massflow and velocity of the exhaust gases.
Technical viability - Solutions proposed must be based on sound scientific principles and have pilot scale data that demonstrate efficacy. Also, the associated equipment must be able to withstand the harsh environment inside an exhaust stack.
Scale-up potential - Solutions proposed must have a clear pathway to be application on commercial ships. Solutions already practiced in marine markets have higher value. The ideal partner would be able to lead the design and installation of full-scale systems.
Capital and operating costs - Solutions would need to provide reasonable return on investment, consistent with the 30% energy losses experienced today. The return on investment assumptions for any proposed solution should include a full life-cycle analysis (including capital/installation costs, maintenance costs, installation time, etc.)
Ownership - Solutions covered by patents have higher value. At a minimum, proposed solutions must not be prohibited by other patents in the field.
Ship operations - Solutions should not impact the normal operation of the ship engine. The equipment space and weight must be able to be retrofitted onto existing vessels. Moreover the equipment should not increase back pressure to the point it effects engine performance.
Intellectual property requirements - None required when using exiting solutions, however where Stena takes technology and creates a bespoke applied solution then patents and IP may need to be sought.
Killer issues - Solutions will not be considered if, in Stena’s opinion:
- Installation and maintenance costs should not be prohibitive for broad application
- Proposals lack sufficient supporting laboratory or pilot scale data
- Solutions don’t adhere to global maritime environmental or safety regulations
- Solutions would void guarantees from engine suppliers. Approval may be needed.
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