The role of gas storage
Gas storage is provided using underground gas storage facilities, LNG storage facilities with regasification plants connected into the pipeline grid and on a smaller scale in gas pipelines.
Storage services are used in Australia for a range of purposes, including for:
- supply of gas to meet peak demand in seasonal markets, most notably in Victoria due to the impact of heating loads in winter;
- security of supply in case of supply disruption;
- supply to peaking power stations; and
- trading opportunities to buy gas during low price periods and sell in high price periods.
Storage facilities in Australia
The major underground gas storage facilities in Australia are the:
- Chookoo (SA) storage facility which was developed by Santos to manage production outages at the Ballera plant;
- Moomba (SA) storage facility owned by Santos;
- Silver Springs Gas Storage (QLD) which is owned by AGL and was developed to manage ramp gas for QCLNG;
- Kincora Gas Storage Facility (QLD);
- Roma Underground Gas Storage (QLD) which was developed by Santos to manage ramp gas for the GLNG project;
- Iona Underground Gas Storage (VIC), which is owned by Lochard Energy;
- Mondara Underground Gas Storage (WA) which is owned by APA and was expanded after the Varanus Island outage to increase security of supply; and
- Tubridgi Gas Storage (WA) which was commissioned in 2017 by AGIG.
Transmission pipelines are capable of providing storage, subject to the extent of utilisation of the pipelines for providing transportation services. Two pipelines have been built specifically to provide storage services for power stations.
The Colongra Gas Transmission and Storage Pipeline (NSW) was developed to provide storage for the Colongra peaking power station. The Braemar Linepack Connection (QLD) was developed to provide storage for the Braemar Power Station.
Storage is also provided in LNG storage facilities in Dandenong (VIC) and Newcastle (NSW).
Storage services
Storage facilities are designed with operating parameters to meet the terms of the services that they provide. The storage capacity of the dedicated storage facilities ranges from 0.68 PJ (Dandenong LNG Storage Facility) to 75 PJ (Roma Underground Gas Storage).
The Dandenong LNG Storage Facility has the lowest storage capacity, yet it has a relatively high withdrawal rate (237 TJ/day) although the LNG that is stored can be regasified and injected into the pipeline grid within hours. The high withdrawal rate of the Dandenong LNG Storage Facility reflects it’s role in peak shaving and allowing market participants to manage wholesale gas price risk in the Victorian Declared Wholesale Gas Market.
Storage facilities, such as Tubridgi Gas Storage and Roma Underground Gas Storage, that provide longer term supply security (months not hours) or to manage ramp gas have much lower withdrawal rates relative to their storage capacity. The IONA Gas Plant which has a storage capacity of 23 PJ and the highest withdrawal rate of 390 TJ/day has the flexibility to provide services for both peak shaving and longer term security of supply.
The challenge of intermittent renewables
The development of renewables in Queensland offers a useful case study and an opportunity to explore the role of gas peaking power stations to address the intermittent nature of renewable generation.
In Queensland the installed capacity of solar power stations is 1,500 MW and the capacity of residential roof top solar installations was 2,300 MW (Clean Energy Council as at December 2018). The capacity of solar power stations under construction is 370 MW and the capacity of proposed solar power stations is15,000 MW (DNRM&E).
The variability from solar generation and therefore the opportunity for gas peaking plants is highlighted in the following charts. These charts plot the output (5 am to 6pm) of solar arrays operated by the University of Queensland that are located across south east Queensland (Gatton to Brisbane) on two consecutive days in October 2019.
The above figures highlight the volatility of output from solar power stations within a day, the variability in peak output and that weather conditions can impact output of solar power stations across a region. Similar issues apply to wind power.
Coal and gas fired power stations in Australia have been in many cases located close to the source of fuel or in some cases gas fired power stations are connected to more than one gas pipeline. Therefore a single cause that could result in a generation outage was unlikely to apply to the entire generation fleet in a region.
The above figure identifies the location of operational and proposed (white symbols) solar power stations located on or near electricity transmission lines hat connect to Brisbane. There is 370 MW of existing solar power stations and 8,330 MW of proposed solar power stations in the area of the map.
Conclusions
The clustering of the proposed power stations around transmission lines creates a risk to electricity supply due to the potential for similar weather conditions across a region reducing the amount of sunlight and therefore “fuel” for these power stations.
If a significant proportion of the proposed solar power stations in Queensland are built, this will increase the potential role for fast start gas fired peaking power stations and gas storage to respond to variability in solar output due to regional weather conditions.
This could be achieved with the development of fast start power stations using aero derivative gas turbines to complement intermittent renewables.