Most people are familiar with heat recovery, an energy reduction method that uses waste heat from engine cooling and exhaust fumes to heat up the HVAC and other systems. The same is possible with cold and this blog explains how cold recovery can get a significant role as energy recovery system for maritime HVAC systems.
The main goal for a ship’s engine is to generate power and propel the vessel. Approximately 60% run on heavy fuel oil (HFO) as an energy source, a fuel that’s been in use since the introduction of internal combustion engines. This tar-like substance is refined from crude oil. It became widely used in the 1960s once refining techniques made it more profitable.
While the low price and wide availability have made HFO a popular fuel source, it has been an outright disaster for the environment. Aside from the ecological catastrophes that happen when the oil is spilled, the combustion of HFO leads to high CO2 and sulphur emissions. It’s no more than can be expected from this ancient fuel source that came after the steam engine. Now, the time to evolve to a better and cleaner kind of fuel is clearly upon us.
Although initially exempting itself from international agreements, the international shipping industry has felt increasing pressure from scientists and environmental groups. Now IMO has set the goal to reduce CO2 emissions by 40% in 2050 compared to 2008. Reaching this goal will require alternative fuel to be used. More and more shipping companies are cautiously switching to liquid natural gas (LNG) as an alternative, especially for new builds. The multi-sector industry coalition SEA-LNG reports that LNG-fuelled vessels are accounting for 30% of orders in 2021.
This is a development in which Europe is leading the way. The North and Baltic seas fall under Emission Controlled Areas (ECA) and LNG bunkering is available in all major European ports. The infrastructure is also improving on a global scale with LNG available in most major shipping hubs like the Port of Singapore.
The name LNG reflects the fact that it involves natural gas being compressed and converted into liquified natural gas in order to optimise it for storability and transport. The fuel occupies 600 times less space than in gaseous form. The LNG state is obtained by cooling the gas to minus 162°C at close to atmospheric pressure, with regasification needed for combustion.
This makes LNG very interesting for HVAC systems as the regasification process releases a significant amount of cold energy. Theoretically speaking, one tonne of LNG releases about 230 kWh of cold energy. Setting up a system with heat exchangers, this cold energy can be used to drive several HVAC cooling activities. As long as the engine is running, free cold energy is available.
As more shipping companies switch to LNG as a fuel source, cold recovery is becoming a serious option for reducing energy consumption.
Like to know more about LNG cold recovery? Contact one of our engineers. And, as always, stay tuned to heinenhopman.com for everything HVAC.