Appendix Utilising LNG 'waste' cold
Natural gas is refrigerated to -162C to become Liquefied Natural Gas (LNG) for transport by supertanker from producing to consuming nations. At the import terminal the LNG is warmed to re-gasify before entering the pipeline network, and most of the cold that kept it in compact liquid form during the sea voyage is usually discarded. This spectacular waste of energy is increasingly significant since the IEA forecasts European LNG imports will double to 120 billion cubic metres per year by 2040.
Each tonne of LNG contains the cold energy equivalent of 240kWh, quite apart from the chemical energy contained in its methane molecules, and typically 80% of this cold energy is thrown away. The global LNG trade is expected to double to 500 million tonnes per year by 2030, representing cold energy of 120TWh, theoretically equal to the annual output of 14 1GW nuclear power stations. To save energy, emissions and cost it is vital to find productive uses for LNG waste cold.
Large users of cold such as data centres could be built close to LNG plants to access its waste cold 'over the fence'. But to make use of as much of the waste cold as possible, it needs to be transformed into a storable and transportable form, allowing it to be used in vehicles and at remote locations. One way to achieve this is through liquid air.
When LNG is re-gasified from its liquid state at -162C to enter the gas grid, the cold it gives off can be recycled through a co-located air liquefaction plant to help produce liquid air or nitrogen at around -196C.
This reduces the electricity required to produce the cryogen and its carbon intensity by about two thirds, and the cost by almost half. This approach has been demonstrated for some years at an LNG terminal at Osaka in Japan. If it were adopted more widely the impact could be huge. Our modelling suggests:
- the cold given off by the Isle of Grain LNG terminal each year could fuel London's entire bus fleet as liquid air 'heat hybrids' more than six times over, reducing diesel consumption by 25%;
- the waste cold from India's projected LNG imports in 2022 could provide liquid air cooling for over half a million refrigerated trucks, or fuel 230,000 heat hybrid buses or 1 million zero-emission autorickshaws;
- the projected global LNG trade in 2030 could provide liquid air cooling for 4.2 million refrigerated delivery trucks - double the current global fleet.
Once converted into liquid air, LNG waste cold could be used in applications as diverse as static and vehicle refrigeration, heat hybrid truck and bus propulsion engines, zero-emission emergency electricity generation, and bulk energy storage and grid balancing. These applications would reduce diesel consumption, greenhouse gas emissions and local air pollution, and would reduce costs even more than those operating on conventionally produced liquid nitrogen. In this way LNG waste cold could provide a 'fuel' for the Cold Economy.