Natural gas is the cleanest burning fossil fuel that meets stringent environmental norms to reduce carbon dioxide emissions. With the inevitable global shift to a natural gas-based economy, there is an increasing need to develop technologies to store natural gas on a large scale. Where pipelines are absent, liquefied natural gas (LNG) becomes an efficient medium to transport natural gas for long distance due to its high volumetric capacity (600 v/v). However, natural gas cannot be stored as LNG due to its continuous boil-off problem (due to heat transfer) and high cooling cost requirements. On the other hand, compressed natural gas (CNG) requires high pressure for storage, and this poses a high risk for large scale natural gas storage.
In Singapore, about 97 per cent of electricity is generated from natural gas fired at the power plants. Hence, effective and efficient natural gas storage is of high national importance for Singapore’s energy security and resilience.
A team from the NUS Centre for Energy Research and Technology (CERT) led by Praveen Linga, an Associate Professor of Chemical and Biomolecular Engineering, is developing Solidified Natural Gas (SNG) technology that can overcome challenges in storing natural gas to provide energy to Singapore. This research project is funded in part under the Energy Innovation Research Programme (EIRP), which is administrated by the Energy Market Authority (EMA), and funded by the National Research Foundation (NRF) and Industry Partner, Lloyds Register Global Technology Centre Singapore.
SNG technology involves the storage of natural gas in the form of ‘gas hydrates’, which comprise cages made up of water molecules that serve as host to store guest gas molecules like methane at certain pressure and temperature conditions. The guest gas is stored in its original molecular form, and held only by weak physical bonds inside hydrate cages, enabling easy recovery of pure gas that can be readily used for suitable applications.
This technology is highly advantageous in being ‘non-explosive’; it is extremely safe to handle, environmentally friendly, cost effective, and offers a very compact mode of storage with high capacity. Moreover, the energy requirement for hydrate formation and storage could be provided by LNG cold energy.
Although SNG technology has been known since 1990s as a potential technology for storing and transporting natural gas, commercialisation of this technology has not taken place due to major challenges that include the slow gas hydrate formation, as well as limited knowledge on long term storage methods of hydrates at moderate temperature/pressure conditions.
“Our research team aims to develop a suitable method for continuous production of gas hydrates for commercial deployment of SNG technology. Our innovation is in the design of process and identification of a suitable promoter that can mitigate both the process and storage challenges,” said Associate Professor Linga.
Associate Professor Linga and members of his team – Professor Karimi, who is co-principal investigator; Mr. Hoon Kiang Tan, industry collaborator; and Dr Hari Prakash Veluswamy, Research Fellow – are geared up in their efforts to make SNG technology viable for commercial use. The researchers are now working to build a prototype of the SNG technology process chain to prove its economic and technical feasibility. If successful, this innovation could be a turning point in the development of a new technology for efficient and effective large scale storage of natural gas.