A renewable-energy-based economy is coming
Written by Mark Taylor, Hesperia
My observation over the last few years of working with developers and government on energy strategies and policies for buildings and residential estates, is that everyone sees the same future: an economy built on plentiful, cheap renewable energy. And everyone is mapping out the best way of getting there; looking for the co-benefits that suit their operation and staging their transition to suit. There are still some big picture challenges and resulting opportunities.
The transition to a renewable-energy-based economy has interim challenges, like how to keep electricity grids and markets performing well while the generation mix changes radically. These problems will be worked through over the next two or three years. However, a deeper challenge is that the cheap and proven renewable energy generation technologies are intermittent; photovoltaic (PV) and wind generators vary in output depending on naturally varying inputs that can, on occasion, change dramatically and unexpectantly.
Responses to this challenge will be mix of things, including:
- Demand-side management
Diversity in this case means looking at a range of technologies, across a range of locations. Investment in geothermal and wave power technologies has yielded promising but so far insubstantial results. This leaves us with solar and wind. The variability of cloud cover means that PV systems spread over a wider area will produce a more stable output in aggregate as clouds pass over and a similar approach suits wind farms. The installation of long transmission lines that pass a variety of suitable wind and solar farm sites will improve stability in the long term. Governments may need to assist with this. Offshore wind turbines may enable generation sites to spread along the coast without as large an impact on land use and aesthetics.
Demand-side management is going to be big. In the same way that many industrial plants have been set up around 24-hour operations at a constant rate, matching the way electricity was being supplied, the new breed of plants will be able to respond to variable energy costs and availability. Constant power supply will still be available, but the cheapest power may be variable.
Energy storage is probably the most discussed response to intermittency in renewables. For many of us with solar on our rooftops, a battery is the next energy upgrade we plan for our homes.
The Australian Energy Market Operator (AEMO) identifies three ‘depths’ of energy storage that are required to fully support a grid that is largely based on renewable energy generation that is intermittent by nature:
- Shallow storage – this category helps keep the grid stable as loads and generation inputs fluctuate. New ideas, such as Virtual Power Plants (VPPs) that can enable small household batteries to serve both the home and the grid
- Medium storage – for intra-day shifting and includes 4-hour batteries, 6 to 12-hour pumped hydro. This is what we typically think about when we’re looking at batteries installed in homes: moving the energy that is harvested during the sunny or windy part of the day to the evening when the main energy peak tends to occur
- Deep storage – for Variable Renewable Energy ‘droughts’ and seasonal smoothing and includes 24 to 48-hour pumped hydro and includes Snowy 2.0 and Tumut 3. This is required because renewable energy generation depends on natural systems that can have extended weak periods and seasonal cycles. A fundamental but not always well understood aspect of solar PV is that it is seasonally variable; winter production can be half that of summer. Wind also has seasonal cycles. Seasonal storage may also be addressed through industrial processes, with green hydrogen and desalination of sea water both providing opportunities to use huge amounts of cheap renewable energy and store their products for long periods.
The final ingredient in this transition needs to take the concept of ‘renewable’ beyond just the fuel source, such as the wind or the sun, and into the materials and supply chain that will deliver the new energy system. Recyclability of PV modules and lithium batteries is increasingly discussed but there has been little action. The excitement about being net zero emission as a nation in 2050 will quickly turn sour if it is achieved on the back of environmental destruction around mining and refining, and if poor design continues to render renewable energy equipment difficult or impossible to recycle.
We know where we are going. Intelligent planning and targeted technical development are required – now – to get there in good time and in good shape.
Page 51, ISP 2020 (AEMO, 2020)