Integration of renewable energy into the grid
There is an enormous imperative to change the way we produce and use energy to mitigate climate change while eradicating energy poverty. Solar and wind power are increasingly replacing coal and gas-fueled energy generation towards a sustainable energy future. However, variable renewable generation is reliant on new technologies to efficiently and reliably integrate energy supply into the electric network.
Researchers from Monash Energy Institute's Grid Innovation Hub are undertaking studies into how additional renewable energy can be connected to our electric grid. In this article, we introduce some of the complexities faced by our electric grid and the work that Grid Innovation Hub PhD scholars are doing towards addressing challenges faced by our energy sector.
A grid that I used to know
The electric grid is commonly segmented into two networks; the distribution network and the transmission network. In Australia, the distribution network delivers electricity from substations to homes and businesses and ranges from a low voltage (415 volts) to high voltage (66,000 volts). Our houses are connected to a low-voltage distribution network with 230 volts of power supply. In contrast, the transmission network functions under very high voltages, between 33 and 275 kilovolts, suitable to transmit bulk power.
Our electric grid is evolving
One in five Australian households now own rooftop solar photovoltaics (PV) and are connected into our distribution network changing the way our grid behaves. We have moved from a unidirectional power flow to a two-directional power flow. Consumers generating power at the household level is complicating our power system. We now need a complete picture of the grid’s topology to help us manage our distributed energy resources (DERs), the way they interact with our grid, and reliably deliver power to the people.
At the same time, our transmission network is facing challenges arising from a rapid transition to renewables. In the past, we relied on synchronous generators, typically fuelled by gas, coal or hydro, to generate electric power and provide grid support. Utility-scale renewable energy farms are usually located in remote areas and offshore. They use long transmission lines to send power where it is needed. Australia’s National Electricity Market (NEM) network is very long, skinny and connects five regional market jurisdictions – Queensland, New South Wales (including the Australian Capital Territory), Victoria, South Australia, and Tasmania. The characteristics of long transmission lines make them vulnerable to sudden changes in the grid. Connecting wind and solar farms to these weak grids can make the system unstable, or create subsynchronous oscillations (anything below 50 Hertz) that can also damage synchronous generators connected to the network.
Dr Behrooz Bahrani (Senior Lecturer, Faculty of Engineering/ Department of ECSE and Director of Grid Innovation Hub, Faculty of Engineering) says that “both networks are evolving and will impact each other. There will be more players at the distribution and transmission levels, and effective large-scale batteries will allow us to store the generated energy. Some are already being installed in the National Electricity Market (NEM). Until 2024, four years from now, there will be around 1.5 gigawatts of batteries installed in the NEM, which is a significant amount, and it will only increase. So, we will have a lot more renewables in the system, but at the same time, energy storage technologies will help the grid to manage itself.”
Dr Reza Razzaghi (Lecturer, Faculty of Engineering/ Department of ECSE, Faculty of Engineering), notes that “power grid is probably one of the most sophisticated systems we have designed, if you think of the complexity of the Australian power system, expanding over thousands of kilometres. It is a challenging job to make sure it operates reliably and securely. And the job is becoming harder. Traditionally, the distribution networks were designed to be ‘passive’ and just consume power. The integration of Distributed Energy Resources (DER), such as small scale residential PV into the distribution network, transforms this ‘passive grid’ into an ‘active grid’, requiring new tools to control and operate it securely and efficiently”.
Dr Christoph Bergmeir (Senior Research Fellow at Data Science and AI Dept., Faculty of Information Technology), states the importance of accurate forecasts for power network stability and price stability. “Forecasting is important both for renewable energy and for energy demand. Renewable energy is not available on-demand like fossil fuels but is constrained by weather behaviour. So, to have a reliable and affordable energy supply, we need to predict the likely availability and capacity of wind and solar power.
This needs to then be matched against likely demand, so we need to predict
the demand as well, which can be quite uncertain (e.g. due to uptake of electric vehicles)”.
Enabling the next generation to power a sustainable world
In this two-part series, we feature research conducted by five Monash University PhD students who received supplementary scholarships from the Monash Energy Institute’s Grid Innovation Hub. The scholarships were partially funded by Indra and the Australian Renewable Energy Agency.