by Vassilios Agelidis and Tim Dixon, Australian Energy Research Institute, UNSW Australia
There are many new technological developments that have the potential to dramatically affect the electricity grid. These disruptive technologies are often feared by utilities, networks and distributors due to their ability to fundamentally redefine the way electricity grids need to be designed, managed and operated. And these technologies are already starting to redraw the relationship between grid owners/operators and electricity consumers – a worrying trend for many in the industry.
In the Australian context, it is widely acknowledged that traditional consumers are transforming into a new species of customer – the prosumer – becoming ever more proactive in the way they manage their electricity use, as well as increasingly generating electricity themselves through rooftop solar photovoltaic (PV) systems. There are currently estimated to be around 1.4 million small scale PV generators installed on Australian dwellings; there were just 3,500 nationwide ten years ago.
Yet up to this point the abundance of rooftop solar in Australia, while contributing to decreased demand for grid power, has not by itself been enough to entice large numbers of customers to disconnect from the grid altogether. Nor have the large numbers of grid-connected distributed PV generators significantly increased the total percentage of renewable energy in the grid. Indeed, in the states where renewables do make up a significant proportion of generation, that honour has fallen to hydro or utility-scale wind farms.
The fact that solar generation and typical load curves don’t match have meant that, although household consumption has fallen, most people remain firmly connected to the network, relying on grid-supplied power for much of their total energy, and all of it after dark.
However, the development of a particular strain of disruptive technology – energy storage – promises to significantly increase the penetration of renewables into the grid, and perhaps in the long term, make grid disconnection a viable alternative for many households.
Efficient, cost effective, and reliable energy storage is in many ways the ‘Holy Grail’ of renewable energy, and is seen by many as the key enabler for the integration of renewables with the electricity grid in ever higher quantities, without jeopardising network stability and security of supply. Storage can offer flexibility that renewable generation alone often cannot, moderating the peaks and troughs of PV or wind power already in the system, as well as alleviating those same peaks and troughs on the demand side.
But to implement significant levels of storage into the grid we must face the critical realisation that there is no silver bullet when it comes to storage technologies. Just as there is no single power generation technology which meets all our environmental, reliability, cost and flexibility requirements, neither is there a storage technology which ticks all these boxes. Whether it is solar thermal, pumped hydro, or the next generation of lithium-based or other chemical batteries, each technological solution has its own strengths and weaknesses. Research and development efforts will address some of the shortcomings of individual technologies at the materials and design level, maximising performance and reducing production costs for individual types of storage technologies. However, perhaps most important of all is intelligent management of the whole storage system and lifecycle.
From the engineering side, there needs to be an effective energy arbitrage – matching generation and load characteristics with the most appropriate storage technologies, and making them work together to create a more flexible storage system. Some storage technologies are very good at providing a steady, reliable supply of low voltage energy over longer periods of time, while others are better at providing faster, deeper discharges of power with minimal effects on asset longevity. Intelligent control systems that charge to and dispatch from the most appropriate storage sources depending on generation and load profiles are critical to increasing the efficiency, reliability, lifespan and cost-effectiveness of the storage system as a whole.
There is also a need for intelligent use of storage based on price signals in the market. Each time a storage unit is used to discharge electricity, the lifespan of that asset decreases and maintenance costs rise. Therefore, every kWh that is dispatched from a solar thermal system or battery has a cost over and above the initial generation cost. So storage operators must be able to recognise when it is profitable to use their storage assets, by integrating real time price signals into their storage systems, allowing them to dispatch only when the price of electricity is high enough to translate into a meaningful profit.
But why should utilities and networks take up the lead when it comes to developing a better storage system for the grid?
First, there are proven benefits for generators, utilities and networks alike, as intelligently deployed storage (for example, to deal with peak demand) can more than pay for itself in the form of deferment of more costly capital investments.
Second, the worst thing the industry could do is sit back and watch on. It did just that ten years ago, when solar PV systems were too expensive for most consumers to consider installing them – and as we all know, the price of PV cells fell sharply, coinciding with a rise in electricity prices. As power prices continue to rise, you would have to be pretty naive not to think that as storage technologies become more mature and the cost of storage inevitably falls, many Australians will consider disconnecting from the grid altogether.
Indeed, that scenario may not be as far off as we think. The latest generation of electric vehicles (EVs) with ranges in excess of 500km are already on Australian roads. But far from just being a new source of ‘plugged in’ demand, in some scenarios, the proliferation of EVs (particularly as second cars) may actually enable households to further reduce their reliance on grid-supplied power. EVs are essentially huge mobile batteries, and householders may soon be able to use them to power their homes during the evening peak, while charging them during the day from their own PV systems. And when they are ready to upgrade their cars, EV owners may be able to recycle the batteries from their old vehicle to further complement their own energy use.
Cheaper, more flexible and more efficient storage is not just an idea which has great present and future benefits to utilities and networks, it is the future, like it or not. The question is, is the Australian industry ready for the next revolution?
Vassilios Agelidis and Tim Dixon are, respectively, the Director and Manager of the Australian Energy Research Institute at UNSW Australia (www.aeri.unsw.edu.au). Vassilios is Professor in the School of Electrical Engineering at UNSW, and his team is currently working on a number of research projects dealing with energy storage and integration of renewables into the electricity grid.