What factors make it more complicated to increase the amount of renewable...

There are a number of major challenges. Firstly, voltage: in creating the power system it was always assumed that power would start at the generator and flow towards the consumer. Now we have ‘generators’ through rooftop solar PV installed at houses and businesses, which push power in the opposite direction when feeding into the grid. This has the effect of increasing the voltage in the system, causing unintended outcomes which can result in reduced quality of supply for consumers. The more energy we put in at a consumer level, the more significant voltage management becomes.

Another condition of a reliable energy systems is that enough inertia is maintained to cope with unplanned events, such as a cloud coming over and rapidly reducing solar generation, or perhaps someone driving into a power pole. Inertia is the capacity for an object to remain in motion. In traditional power systems spinning generators have provided inertia and thus an ability to resist disturbances, giving the system time to respond to changing conditions. One of the reasons Future Grid has placed emphasis on the integration of household batteries into the network is their potential for providing virtual inertia in certain circumstances. The level to which we can increase the amount of solar in the system is limited by our ability to provide a mechanism to offset the required inertia.

Inertia and operational reserve (generation capacity that is online, controllable and ready to respond to meet demand) act like a shock absorber. The more renewables you add into the system, the bigger that shock absorber needs to be, which starts to become very expensive. So, the question is: are there other ways to provide that shock absorption into the system, such as batteries or other support mechanisms? This is part of what Future Grid is investigating.

Finally, a characteristic of the Alice Springs grid that differentiates it from many other grids is its isolation. Alice Springs doesn’t have anywhere else to which it can push surplus energy or draw upon additional energy when our network is under stress. There are plenty of isolated grids and stand-alone power systems servicing remote communities in Australia, but Alice Springs is an unusual size and regulated. This is unlike most other large grids, which link a variety of types of generation (such as coal, wind, hydro, solar) which can be adjusted to help maintain balance. A larger number of consumers is also helpful to maintain a stable system as traditional modes of generation struggle to operate at minimum loads. Alice Springs faces isolation, low loads, and fluctuating solar generation which makes it a challenging system to manage.