The 'other' thing a city can do with 480,000 cubic metres of cave

Shu Sun leads research and analysis in energy storage, hydrogen and fuel cells at Bloomberg New Energy Finance. As part of the Energy Smart Technologies team in London, he produces extensive research on the key issues of these evolving markets, from lithium ion battery supply chain and pricing index to emerging grid energy storage.His work focuses on the economics of different technologies, the policy environment and feasible investment opportunities. More BNEF opinion editorials here.

Jurong Island is the heart of Singapore's chemicals industry, hosting 94 petrochemical companies and over 31 billion dollars in total investment. One of its expansion projects is Jurong Rock Caverns, a cave hewn from rock 100 metres below the surface, which when completed will hold 480,000 cubic metres of oil and other heavy distillates. Oil storage, though, isn't the only energy application for a massive cave in a rapidly growing, energy-sensitive city.

Compressed air energy storage (CAES) is another use for geologically stable underground formations such as Jurong. These projects pressurise and store air, which is then released and expands through turbomachinery to produce large amounts of reliable electricity. For years, two CAES projects have been operational in the US and Europe. Today, there are two CAES projects online: One in Alabama, the US, and another operated by electricity giant E.ON in Germany. Seven more are being developed and when launched, the total power output for all nine projects could exceed 1.5GW, the size of a very large combined-cycle natural gas power plant.

With any given storage space, a CAES project developer must make a dispatch decision weighing storage and energy capacity. Lots of storage (many hours of dispatch) implies less capacity (less instantaneous power output in megawatts). The opposite is also true: Less storage implies more capacity. The PowerSouth project in Alabama is high in terms of storage, but has a lower capacity. E.ON's project is the opposite: Small storage, high capacity.

Compressed air energy storage's many uses

CAES can be put to many uses, with one being for "firming and shaping" an electricity service area's load during periods of rapid ramping up and down, or disruptions. It can also be used for time-shifting electrical loads within the network. Another use would be to buy power from neighbouring countries during off-peak hours, convert that energy into compressed air, and then use it during peak hours in Singapore.

What would happen if Jurong Caverns (which is 55 percent larger than the E.ON project) was converted to CAES"color: #888888;">

Jurong could generate nearly two days of electricity if needed--or meet seven hours of demand similar to a medium-sized gas turbine power plant. In the higher power configuration, Jurong would represent4.5 percentof Singapore's entire peak load of 6,494MW…and if peak demand was the most important consideration in configuring CAES, the project could be configured for much larger turbomachinery with less storage.

For Singapore, a 5-7-hour configuration could work the best, allowing it to shift the energy it produces during night time or even purchase cheaper off-peak electricity from its neighbouring countries to power its industries during the day. The next time you look at a petrochemical storage facility and wonder what is going underneath, remember that it is probably over geologic formations which store energy, and that the caves and salt domes used to store oil and gas could also be used to store surprising amounts of electricity as well.

BY : Shu Sun, Bloomberg New Energy Finance