Korea Maritime & Ocean University developed two new heat recovery systems that can boost energy efficiency in LNG ships.
Using LNG as fuel can help ships reduce their ghg emissions. However, LNG ships are currently inefficient, with massive heat losses. Thus, university researchers developed new heat recovery systems for better energy efficiency.
Currently, LNG ships lose up to 25 per cent of their input heat in the form of exhaust gas. Recovering this heat is key to energy efficiency. In a recent stud, a team from Korea Maritime & Ocean University , led by Dr. Yeong-Seok Choi , developed these new systems for LNG ships.
Choi explained: “By increasing the energy efficiency of LNG systems, we are directly contributing to environmental protection.”
The research is based on what is called the ‘organic ranking cycle (ORC). In ORC, an organic fluid is first boiled, then used to turn a turbine to generate electricity, during which it loses heat. The fluid is then condensed and reheated in a continuation of the cycle. In LNG ships, ORC also allows the preheating of cold fuel before burning.
Two heat recovery systems for LNG ships The first of the systems is the double stage ORC system (DSO). It uses the heat from the engine exhaust gas to run two ORCs with connections to two generators.
The second, the added double stage ORC system (ADSO), additionally features a third ORC; also, two of its ORCs exchange heat with each other.
The team examined the workings of DSO and ADSO with combinations of different organic fluids. They then performed energy, exergy, and economic analyses on the systems.
In conclusion, the DSO had better overall energy efficiency, ADSO was more suitable for cramped engine spaces. They also saw that performance depended greatly on a fluid combination. Overall, the new designs achieved substantial improvements in energy efficiency.
“Although our research is focused on shipping, this work can be applied to several other industries and cryogenic hydrogen research as well,” said Choi.