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How much storage and back-up do high renewable grids need?

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Exactly how much storage and back-up does renewable energy need? It’s a question at the heart of electricity planning and the subject of many of the myths peddled by vested interests in the fossil fuel lobby and the gullible media. The answer is: not nearly as much as the naysayers would have you think.

According to the CSIRO and Energy Networks Australia, which own the local and interstate grids, a level of between 30 and 50 per cent share of variable renewable energy sources such as wind and solar can be easily accommodated without any further back-up.

That’s because there is so much back-up built into the system already to support coal and gas-fired generation, either to meet peaks in demand, or to fill in gaps when coal and gas plants fail, as they do quite regularly, particularly in hot weather.

The estimate also reflects the changing view of technologies and how grids are managed. It was not so long ago that most engineers would have thought 10 per cent was the absolute maximum. The Murdoch media has been misquoting an old report saying that 20 per cent is the level at which problems occur. Some network operators think 60 per cent is the level.

The CSIRO and ENA says the amount of storage needed beyond that 30 to 50 per cent continues to be minimal until much greater levels of renewable energy are introduced, and then the extent of that back-up is largely dependent on local weather and climate, and their natural renewable energy sources.

The roadmap released by CSIRO and ENA on Friday, following nearly three years of work, includes an appendix on the levels of storage and/or peaking plant back-up needed, and how this might affect individual states.

By their own admission, the estimates are on the conservative side – because they have not allowed for greater network links between the states, and because some of the estimates do not include a mix of options. But you can get the drift.

future grid storage % renewables

“(Our findings) indicate that battery storage is generally not required until high levels of renewable energy share are achieved and may form part of an optimised system when renewable share reaches 30-50%,” the report says.

Even approaching 100 per cent renewable energy, the amount of storage in some states is only around five hours. In other states, it could be much higher (see table above).

As the renewable energy share approaches 100 per cent, the amount of battery storage increases non-linearly and approaches an average ratio of 1:1 with installed capacity of variable renewables.

Again, however, there is significant variation, and it will depend on how much alternative dispatchable energy there might be: biogas peaking plant, solar thermal, pumped hydro and the like.

Tasmania, for instance, will require a much lower ratio due to its large existing hydro power capacity, and there are circumstances where New South Wales and South Australia may be able to deploy a lower ratio of batteries.

Queensland and Victoria, however, may require a higher ratio, due to poorer wind resources in the former and poorer solar resources in the latter.

The analysis indicates that up until 80 per cent wind and solar share, less than five hours of battery storage at average state load is required to support energy balancing working together with the existing dispatchable technologies such as hydro and gas.

It notes that gas or biogas peaking plant will be more cost effective than adding additional storage capacity in circumstances where a substantial renewable generation shortfall extends for more than a third of a day – underlining the point that battery storage is best for short periods.

And if the reliance does fall on peaking plant, then there will not be a need for 1:1 back-up, because that will likely be required in mild, cloudier winter days rather than the heatwaves in mid-summer, when there should be enough solar and storage to cater for the peaks. In winter, the peaking capacity would be around 60 per cent of peak demand.

“While variable renewable generation creates a need for additional battery storage it may not necessarily be installed via a formula relating to installed capacity. Rather the total battery requirement more strongly relates to being able to meet average state load for an increasing number of hours.”

future grid storage hours

But the need for storage and back-up will be reduced if more interconnectors are built linking the renewable energy sources in one state with another.

“Solar provides a relatively economic and predictable daytime supply in all states,” it says. “However, a significant contribution from wind power is crucial to fill in the supply gaps at night together with storage and dispatchable gas capacity.”

future grid coincident wind generation

But it is the sheer volume of rooftop solar and consumer-installed battery storage that will play a critical role in managing the grid.

This graph below illustrates the phenomenal amount of rooftop solar that will be installed in each state over the next few decades – a total of 85GW across the country. By 2030 in Queensland, there will be more solar capacity than current coal capacity. The same will be true of NSW a few years later.

future grid rooftop solar by stateEven more dramatic is the amount of battery storage that is installed – nearly 100GWh across the country – as customers seek to maximise the value of their solar panels, and to lessen their dependence on the grid.

future grid storage by state

The collection of installation data is in its infancy, however, it is widely reported that existing rooftop solar owners, seeking to get greater value from their existing investment are the primary early adopter group. Battery storage also represents an opportunity for customers

“It is anticipated that battery owners may allocate control of their battery to other agents who can fine tune and aggregate battery operation to maximise the rewards they receive for assisting with energy balancing for both the local network zone substation and the state generation node,” the report says.

“This wide ranging and very important role envisaged for battery storage means that the factors that will play into state level adoption include existing and future solar installations, the specific critical peak and daily peak prices offered in each state, the state opportunities for avoided network augmentation and the relative need for wholesale market energy balancing or variable renewable penetration.”

One of the key challenges for the growing installation of rooftop solar was the stress on substations, which began to experience “reverse flows” when the penetration reached more than 30 to 40 per cent.

High shares of rooftop solar will hollow-out the load during the middle of the day, leading to rising voltages on the local distribution system, but the addition of storage allows a zone substation to potentially absorb a higher penetration of solar without running into issues.

“However, this requires coordinated action to provide incentives or rewards for a useful level of storage to be installed, and for the available capacity to be operated in a way that addresses zone substation level needs and local congestion,” the report says.

  

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  • solarguy

    Biogas above natural gas for peaker’s and long term storage is the best to target. Kill two birds with one stone.

    • Any ideas on how much biogas would be required and where it will come from??

      • Joe

        David, the Bio Gas literally comes straight from our collective arses. Every sewage treatment works is a Bio Gas Power Plant in waiting. They do it overseas but Australia as usual is way ‘behind’. It is continuous power…just keep visiting the crapper.

        • Ha ha, I can certainly contribute!

      • solarguy

        No I don’t know how much would be needed, but I can tell you where it will come from. Sewage and green waste. One of my local treatment works processes 5.6 million litres per day and 1 tonne of feed stock = 1m3 of biogas, this has the energy equivalent of 1.2lt of petrol or 6kwh of electricity.

        • Thanks. It is always good to get some hard facts rather than pure commentary.
          So assuming my units are correct that would provide 33,6MWh of electricity per day, which is significant.

  • George Darroch

    The worst demand/supply scenario for intermittent renewables is surely a long and cold (~0 degrees) clear and still night in winter affecting SA-VIC-NSW, or a very hot (30+) still night in which people leave their aircon on overnight.

    Consumer battery will be important to either scenario to complement hydro supply management.

    • George Darroch

      That, and much better insulation. It’s astounding how much of Australia’s energy goes straight out the window.

      • Michael Murray

        And how much of the heat comes in the same way. In Adelaide there are still new houses and sets of of units being built with no eaves to shade the windows and walls. They need to have an energy efficiency sticker on the outside of any new building so the owners know what they are buying.

  • Ian

    The article states we need 100GWH of storage, if a battery lasts 10 years , that’s 10GWH a year motor vehicles require 1000000 x 50KWH= 50 GWH a year, other applications would add to this. But for now, our market is 60GWH a year for batteries. We already have a model for what could be done in Battery manufacture. Check out the stats for Tesla’s gigafactory: Cost to build this: $5 billion. Output expected: 35GWH a year. Our market could be 2 Gigafactories.

    The rest of the world will be flat chat trying to take care of their own battery needs considering world motor vehicle sales are70 million a year.

    We need to build our own “gigafactory” and we need to build it now.

    These are the potential stakeholders:

    Power companies: AGL, Origin, Alina, EnergyAustralia etc,etc
    Telecom companies: Telstra, Optus, Vodafone
    Transport companies
    Banks: NAB, Westpac, Macquarie, ANZ
    Car manufacturers selling vehicles inAustralia: Tesla, Mazda,Toyota,
    Daimler,ford,Nissan, Renault, hyandai, etc,
    Data companies
    Mines
    Construction companies
    Town councils,cities
    local ,state and federal governments

    Why are these entities not doing something since the need is so urgent?

    Each of these could contribute $50 to $100 million to build a factory/ factories and the output could be shared.

    • Ian

      We should play with numbers to see how worthwhile would be such an investment in a 35GWH/year battery factory.

      Income from Factory: at a battery cost of just $100/KWH = $3.5 billion

      Cost of capital about 6 to 8% say 10% for ease of calculation that’s $500 million a year. That would leave about $3billion to actually spend on manufacture the batteries: salaries, materials, electricity etc . That would be a $3.5billion industry just for starters most this money would circulate in Australia.

      The output would be enough for about 500 000 cars. Australia’s cars do on average 13 700km a year or about 1000L/yr of liquid fuel. For each years battery output we could be saving 500 million litres of fuel a year. A car with a decent sized battery (70KWH or more) would use 0.2KWH/km =1.37TWH/year the output of about 500MW wind farm, fairly modest

  • Diotima

    All very interesting, but how much is this high penetration of renewables going to cost in real life (I mean in real money, not the jiggery-pokery advocacy accounting done by green dreamers in their projections)?

    We already know the answer. Those countries with the highest penetration of renewables have the highest electricity prices.

  • itzman

    The obvious way to make an overpriced unreliable expensive intermittent ‘renewable’ energy source cheap and reliable is to add in huge battery costs.

    I mean, its so simple, I can’t see what the fuss is about.

    Even the option of paying all the fossil fuel stations to keep running at massively reduced average output, so they have to charge far far more for what electricity they can sell, is obviously better than simply letting them run all the time at design efficiency.

    You can have whatever grid you like, as long as you are prepared to pay through the nose for it.

    What’s the problem?

    By implementing these measures Australia will destroy its economy and reduce global temperatures by 0.001C. Isn’t that a price worth paying for the moral high ground?