The global 0.5% sulphur cap will be introduced in 2020, and up to 70,000 ships may be affected by the regulation according to IMO. Shipowners around the world now need to adopt solutions to lower the exhaust emissions and improve fuel efficiency. What options do they have to comply with the upcoming regulations?
LNG ships utilise liquefied natural gas that is stored at temperatures of -162 °C. LNG is a clean fuel compared to HFO with 100% reduction of SOx emissions. The largest hurdle for adopting LNG is the capital cost needed for the infrastructure in ports and retrofitting current ships.
Marine gas oil (MGO) is a distillate fuel. It has a lower viscosity than HFO and only contains 0.1% sulphur. Switching is a straight forward solution and MGO can already be used in most HFO systems, although minor adjustment in auxiliary equipment is needed in some cases. The downside is that MGO is significantly more expensive – the average price of MGO is almost double that of HFO.
In essence, exhaust scrubbers expose the exhaust gas to a water spray to scrub out SOx emissions. There are three primary types of scrubbers: open-loop (a once through scrubber using seawater), closed-loop (a recirculating scrubber using alkaline) and hybrid system that can utilise one or both at a time. The main objection to scrubbers, apart from the high upfront investment, is the fact that it doesn’t reduce sulphur, it merely transfers it from the atmosphere to the sea.
Waste heat recovery
The efficiency of a ship’s combustion engine is usually between 30-40%, about 50 % of the total fuel energy is lost in the combustion as heat to the surroundings. Typically, the heat was viewed as low quality and could not be captured. However, new systems have been engineered to convert this waste heat into electricity at high efficiency. One example is the Climeon Heat Power system that can convert waste heat into electricity, resulting in fuel savings.
The process is simple and works for retrofit, newbuild and for all fuel types.
The Climeon Heat Power system exploits the temperature difference between hot and cold water to generate clean electricity which reduces the fuel consumption and the CO2 emissions.
The technology operates at low pressure levels compared to traditional heat power solutions, which are both larger in size and less efficient at low temperatures.
At these low temperatures Climeon delivers up to 50% higher efficiencies than other solutions on the market.
The system's low-pressure levels allow a compact and modular design, making it easily scalable from 150 kW modules up to 2 MW systems for larger installations.
Fuel cells are an alternative to combustion engines. If powered directly by hydrogen they produce electricity with water as the only by-product. Due to the complexity and safety aspects it is currently not feasible to bunker hydrogen on ships. However, with a reformer on board hydrogen can be produced from LNG or methanol and fed directly to the fuel cells without bunkering large quantities of it. The fuel to electricity efficiency of a fuel cell can be as high as 60%.
Li-ion batteries on ships are charged while in harbour, using the more efficient city power plant or renewable energy on land. The use of Li-ion batteries has increased due to a decrease in battery price, increase in energy density and increasing fuel costs. The barriers in using batteries come from the high capital cost and short life cycle when compared to a diesel generator.