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How South Australia can function reliably while moving to 100% renewables

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The Conversation

Despite the criticism levelled at South Australia over its renewable energy ambitions, the state is nevertheless aiming to be carbon neutral by mid-century), which will mean moving to 100% renewable electricity over the next 15-20 years.

The biggest challenge will be meeting the 2-3 hours of peak demand during the evenings, when wind generation happens to be low. This will require a mix of different technologies and strategies, including solar, wind, storage, and possibly a new interconnector to New South Wales.

The issue is the variable nature of some renewable energy technologies – wind turbines only generate electricity when there’s sufficient wind, solar panels when the sun shines. But peaks in demand occasionally coincide with periods of low renewable generation, as was the case during the heatwave a few weeks ago. Although sufficient gas-fired generated capacity existed to pick up the slack, it was not all available at the time and short, localised blackouts were implemented.

Without strategic preparation, these events are going to be more difficult to handle in future as wind and solar farms grow, especially if the interconnector between SA and Victoria fails at a critical time.

But here are some of the things we can do in the short term (the next 2-3 years) and medium term (the coming decade) to create a reliable system on the path to 100% renewable electricity.

The short-term

The key point is that the challenging periods will be infrequent and only last for a few hours. Coal or nuclear power stations, which operate best when run continuously at full power, are too inflexible in operation to pick up the slack at peak demand. They would also be too expensive, hazardous and slow to construct.

In the short term, then, we need to install options that are flexible and dispatchable (i.e. able to generate when required). The options include open-cycle gas turbines (OCGTs), preferably each with a dedicated gas storage; concentrated solar thermal power with thermal storage (CST); and batteries. With the right policies these technologies could make significant contributions to peak supply within 2-3 years.

Currently 320 megawatts of OCGT capacity have been proposed for SA. These generators have the advantage of low capital cost and, as they would be operated infrequently, low annual operating cost. They can be started from cold in about 10 minutes, compared with up to a day for coal power. OCGT owners would be compensated for keeping their units on standby, ready to go when we need it. OCGTs are also sustainable when they operate on renewable fuels – biofuels, hydrogen and ammonia.

There are already several proposals for CST power stations near Port Augusta. Initially about 100MW could be installed. Subsequently, as the global CST market expands and the cost declines, more modules could be added. To use CST for evening peak demand periods, we would need to pay a time-variable feed-in tariff or a contracted price that is highest for supply during those periods.

Battery prices are declining rapidly as mass production takes off, so they could also make a significant short-term contribution. Together with solar panels on both residential and commercial rooftops, batteries could help reduce the overall demand on the grid. Residential and commercial solar owners should be given incentives to install batteries by raising electricity prices during peaks in demand, thus increasing the economic savings from self-consumption and the benefit of feeding-in any excess power generated.

While extra solar and wind farms should be constructed, they should also be balanced by flexible, dispatchable renewable electricity generation. To drive the implementation of CST and large batteries in the absence of federal government support, SA could hold reverse auctions, as Canberra does.

To offset, at least partially, increased peak electricity prices and to help electricity users reduce unnecessary demand, state and federal governments should also expand their energy-efficiency programs.

The medium term

Globally, we are at the beginning of a transition to “smart” grids, in which demand for electricity can be modified almost instantaneously by both the customer and the utility. For the utility to do this, a contract is needed to reward customers for being occasionally and partially “offloaded” (that is, having your air conditioning, refrigerator, or hot water turned off for a short period of time). Currently, only some huge electricity consumers such as aluminium smelters are subject to offloading.

For this to be expanded to residential and smaller commercial customers, we need some kind of “smart” switch. These would be operated remotely, turning off supply to electricity-hungry appliances. While the technologies already exist for smart demand reduction, it could take 5-10 years to mass-produce and roll them out on a large scale.

The cheapest form of electricity storage for the grid is pumped hydro. This is where excess electricity generated during off-peak periods – for instance by wind and solar in the middle of the day – is used to pump water from a low to a high reservoir. During peak periods, the water is then released from the upper reservoir and flows through a turbine, generating electricity.

Pumped storage is well established and can even be found on the Tumut River as part of the Snowy Mountains hydroelectric scheme. Although SA has negligible potential for hydro based on rivers, it appears to have considerable potential for pumping seawater up into many small reservoirs in coastal hills. A research group, led by Andrew Blakers at ANU and funded by ARENA, is investigating this.

Another option is to build a new transmission line to join SA directly to eastern New South Wales via Broken Hill. Although such a line could take a decade to plan and build, and would be expensive, it would make the National Electricity Market grid more resilient and controllable, and would link up renewable energy generation in South Australia (wind and possibly future geothermal) and western NSW (solar and wind) with demand centres in the east. Since it would be valuable national infrastructure, the cost could be shared between the federal and state governments.

A 100% renewable future

Over the next 20 years it is entirely feasible for SA to aim for 100% continuous renewable electricity. The important requirements for reliability and stability are a diverse set of renewable energy sources, especially a balanced mix between variable and flexible-dispatchable technologies, storage, geographic dispersion of wind and solar farms, smart demand management, energy efficiency and possibly a new interconnector joining SA and NSW.

Furthermore, CST, OCGTs, batteries with appropriate inverters, and synchronous condensers can all contribute to a stable and 100% renewable SA.

As a driver of long-term investment, a national carbon price that steadily increases to a high level would compensate for the environmental costs of burning fossil fuels. Furthermore, the Renewable Energy Target (RET) should be extended from 2020 to 2030 and increased in scale. We should also create separate targets for CST with thermal storage and large-scale storage. Finally, the NEM Objective and several of its rules will have to be changed.

However, even without national drivers, SA could transform its grid to one that is renewable, reliable and affordable – in the process showing other states how it can be done.

Source: The Conversation. Reproduced with permission.  

  • wmh

    Heating uses an
    annualised 60% of household energy in Sydney (Ausgrid data) and a lot more than
    that in winter. A well insulated house would need to have stored perhaps 20 or
    30kWh of energy for central heating on a cold, cloudy winter’s day. This would
    be expensive storage if implemented using batteries at more than $680 per kWh
    (the latest Powerwall battery cost without installation).

    The solution is to store energy for heating as heat. Hot water storage (45 to
    90 Celsius operating range) can store 52 kWh per 1000 litres, water is cheap
    ($2 / 1000 litres) so most of the cost is the tank. This can be a cheap
    unpressurised tank for hydronic heating or a normal mains pressure tank for the
    domestic hot water service. The tank needs to be well insulated of course but
    insulation is cheap.

    THE SIMPLEST HOT WATER
    STORAGE

    Anybody with an electric hot water service can heat all their domestic hot
    water using 3 or 4kW of solar PV. Most PV owners in NSW have now been
    net-metered and so need only fit a “Diverter” to control the power
    into their existing hot water service. Diverters are common in the UK and are
    now available in Australia.

    • john.boland

      Just one note from my perspective – I do not think that central heating is needed in SA.

      • wmh

        Adelaide’s average temperature is below 20 C for 7 months of the year. How many people live in one or two rooms in winter?

        • john.boland

          to my mind there is no need for heating in bedrooms for example. We certainly have no problem at all without central heating and in fact, I know very few people with it.

    • Peter F

      Absolutely right. 100L of well insulated hot water per bed in new and
      renovated housing Using 85C maximum and a mixing valve 3 days of hot water.
      Unlike batteries,flywheels etc, it can’t support the grid so the storage has less value but it is far cheaper.
      Also the load is not always accessible when you need it but it does flatten the so called “duck curve” and therefore makes gas plant load more manageable and efficient.
      If such storage was mandated we could have more than one million units in 5 years
      time, each with effectively 18kWhr of storage. That is a controllable load of
      18GWhrs.that is equivalent to about 1.5m Powerwall IIs.

      The additional cost for the smart hot water systems about $400m. 1.5m Powerwall II’s even allowing for halving of prices over 5 years $14 billion.

      As you say the concept works even better with hydronic heating, a 600-1500 L tank tank and a heatpump. A few more valves and small second tank and the system can make ice/cold water for cooling

  • john.boland

    “To offset, at least partially, increased peak electricity prices and to help electricity users reduce unnecessary demand, state and federal governments should also expand their energy-efficiency programs.”
    Note that to do this properly the House Energy Ratings (HER) scheme needs adjusting. The star rating is based on year round energy use so an energy efficient house under this scheme can easily be a house that still has a high peak demand in summer. The summer and winter loads need to be evaluated separately to provide comfort all year round.

  • DogzOwn

    While efficiency can obviously help, peak demand keeps increasing with more heatwaves and more people splurging on aircon. Trouble is efficiency standards are slack, so many brands and models, many illegal imports in other countries. Main sales pitch is “cheap”. So how about purchase rebate for above COP6 and surcharge for lower COP? Better still, Oz GHG’s are 28t/p/y(tonnes per person per year), world average is 5 and long term target is 3. So don’t we need to abstain, big time, as well reduce consumption? Most of all need fee-and-dividend carbon price system, easily transferable and fair across national boundaries, which cannot be said for poker games with ETS and EIT.

  • DogzOwn

    While efficiency can obviously help, peak demand keeps increasing with more heatwaves and more people splurging on aircon. Trouble is efficiency standards are slack, so many brands and models, many illegal imports in other countries. Main sales pitch is “cheap”. So how about purchase rebate for above COP6 and surcharge for lower COP? Better still, Oz GHG’s are 28t/p/y(tonnes per person per year), world average is 5 and long term target is 3. So don’t we need to abstain, big time, as well reduce consumption? Most of all need fee-and-dividend carbon price system, easily transferable and fair across national boundaries, which cannot be said for poker games with ETS and EIT.

  • Mark Roest

    Regarding “a new transmission line
    to join SA directly to eastern New South Wales via Broken Hill.
    Although such a line could take a decade to plan and build, and would be
    expensive” — we need to know how expensive, AND what the cost will be to supply it in a large-scale heat wave when the market is bidding up gas prices — and suppliers are holding back to push prices even higher.
    Then we need to know how many kWh might be needed, and we need to multiply that not by battery prices today, but those 5 years from now — probably between $70 and $100 per kWh capacity, with 20,000-cycle lifetimes or better, so half a cent per kWh or less to store and retrieve the electricity, as against 4 to 12 cents today.
    The odds are that even putting extra solar and batteries up in BOTH NSW and SA would be cheaper than the transmission line and a fossil fuel plant and the fuel to run it for its expected life. (Remember, solar 5 years out will likely cost 50 cents a Watt or less.)
    Getting out ahead of the game that way will also pave the way for massive renewable energy penetration, driving fossil fuels out much sooner.

  • solarguy

    Mark, Soon I will have my Hybrid system up and running with up to 28kwh of usable storage for use overnight if needed. The last thing I would be happy about is the network turning off my A/C’s, when I’m self sufficient for power, both in generation and storage.