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Batteries may be a good way to store energy in the home. Battery image from www.shutterstoc.com

The Australian government is reviewing our electricity market to make sure it can provide secure and reliable power in a rapidly changing world. Faced with the rise of renewable energy and limits on carbon pollution, The Conversation has asked experts what kind of future awaits the grid.

Storage is the word of the moment in the energy industry. Since Tesla unveiled its Powerwall, politicians, commentators and industry have hyped storage – and particularly batteries – as the solution for getting more renewable energy into electricity grids and reducing our reliance on fossil fuels.

The concept of storage is simple. A storage system takes power off the grid or from a local generation source and puts it back onto the grid or uses it locally later. It seems like a good idea if you have too much energy, or it is cheap at some times of the day and expensive at others.

So could storage be the answer, and how much would it cost?

The costs of storage

Of course storage isn’t free. It comes with both a capital cost (buying it in the first place) and a running cost, which is related to the cost of electricity to charge the battery and the round-trip efficiency – how much power is lost in the charging and discharging cycle.

To be a sensible economic investment, the benefits have to outweigh the costs. In other words, the savings on your energy bill have to be greater than the capital costs plus the running costs.

There are many different kinds of storage technologies, each with different characteristics. Lithium ion batteries are attractive as they operate effectively at small scales, are lightweight and have good round-trip efficiency. But they are currently expensive per unit of storage capacity.

Pumped hydro at the other end of the scale operates at very large scales, has good round-trip efficiency and is very cheap per unit.

Flywheels (or rotors) have low round-trip efficiency and don’t store a lot of power, but are able to dispatch lots of power in a short time and can also contribute to frequency stability.

Other storage technologies include compressed air, cryogenic (liquid air) energy storage, flow batteries and hydrogen. Each has its respective pluses and minuses.

Figure on storage characteristics. University of Birmingham Energy Storage Centre Report

Each of these technologies will have an appropriate place in the grid to be installed. Lithium ion batteries are a logical choice for a small-scale distributed application, while pumped hydro will work best at the large scale for grid management.

Flow batteries, liquid air and compressed air are in-between technologies in terms of scale, and flywheels and capacitors are most useful at the substation level for voltage and frequency control.

Batteries versus hydro

Let’s focus on lithium ion batteries and compare them to pumped hydro storage.

Lithium ion batteries are coming down in cost at a significant rate. Bloomberg has plotted the costs of lithium ion alongside solar PV. This shows the two technologies share a similar cost curve gradient, with lithium ion reducing from US$1,200 per kilowatt hour to US$600 per kWh in five years (not including installation costs).

As more batteries are built, the price gets cheaper. Bloomberg New Energy Finance

So where does lithium ion need to get to be cost-effective? Imagine a home with a 4.5kW rooftop PV system and variable electricity rate (for instance off-peak cost of 20c, shoulder of 26c and peak of 40c, similar to this tariff).

In such a home a 7kWh battery needs to cost less than A$7,000 fully installed to actually save the homeowner money. In other words, the cost per kWh of storage should be roughly A$1,000 to break even. Currently, batteries cost A$1,000-3,000 per kWh, so they are on the cusp of being cost-effective.

However, there is an important catch here. Retail electricity rates tend to exaggerate the true range in costs between peak and off-peak. The difference in the wholesale market (where retailers buy their electricity) is around 5-10c per kWh, much less than the 20c range in current variable rates. If retailers begin to lose market share, they may respond by reducing or removing these variable rates. That would make peak rates cheaper and mean that batteries would need to be correspondingly cheaper to be cost-effective.

For instance, a flat electricity rate of 25c per kWh means that batteries would need to cost around A$300 per kWh to be cost-effective. That’s less than a third of their current costs.

You could argue that using batteries also reduces the cost of the network itself. By reducing loads at peak time, we can reduce or even remove the need for infrastructure upgrades (substations and additional power lines, for instance).

But this is only true if electricity demand is growing. If demand is flat or falling, then distribution networks will tend to be under-used. Therefore reducing peak demand will not result in any savings.

Overall demand in the National Electricity Market has declined significantly since 2009, so the benefits of storage on the grid will be negligible other than in high-growth corridors. Demand has rebounded in 2015-16 and it will be interesting to watch and see if this is a resumption of the steady increase or if the demand stays low.

Demand in Australia’s National Electricity Market has been falling.

Pumped hydro, on the other hand, is a relatively inexpensive storage technology (already at around A$100 per kWh) as it can store large amounts of energy using a very inexpensive material.

All you need is some water and the means to pump it uphill. So while it can’t be used everywhere, there are many places in the National Electricity Market where it is possible. There are already 1,500 megawatts of pumped hydro in the market (Shoalhaven, Wivenhoe and Tumut 3).

This would be a more logical solution – cheaper and easier to control by the market operator. But in the same way that rooftop PV has gained more popularity than large-scale solar (even though the latter should be cheaper), distributed storage in the form of lithium ion batteries may be the eventual winner, not because of economics but because of human behaviour.

Roger Dargaville has received funding from the Australian Renewable Energy Agency

Tree campaign groups across Sheffield have been at pains to garner expert inputs to substantiate their very clear arguments against the Sheffield chainsaw massacre (Letters, 29 November). The Woodland Trust is a longstanding critic of the Sheffield “Streets Ahead” programme and its epic and disastrous plans for street tree “management”. Equally, the Sheffield Wildlife Trust has not been shy about its deep reservations. More recently, the Arboricultural Association has felt compelled to take a position. It is insulting to condemn them as “fanatics”.

Campaigners do not advocate saving every tree and have a clear position on the removal of the dead and the dangerous. Yet we live in a post-truth, post-factual world. Perhaps then we should be unsurprised when finding some rot and a little deadwood are being cast in the way of constructive dialogue.

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Global food policy needs to shift way from focusing on feeding people enough calories to nourishing people, say leading food experts.

Analysis of black organic fragments found in the Sutton Hoo boat burial reveals they are bitumen from Syria.

From an Arctic expedition to working in a studio in the school of biology and environmental science at University College Dublin, artist Siobhan McDonald collaborates with researchers to broach subjects at the edges of current scientific knowledge

• Crystalline, curated by Helen Carey, will open at the Centre Culturel Irlandais, Paris, on 26 January 2017
  

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The Russian space agency Roscosmos says it has lost contact with an unmanned cargo ship heading for the International Space Station.

Energy and climate targets are ‘well within reach’ but the transport sector is lagging behind

EU countries are on track to meet their 2020 targets for renewable energy and emissions cuts but could fall short of ambitious longer-term goals, the European Environment Agency (EEA) said on Thursday.

“The EU’s 2020 targets on energy and climate are now well within reach,” EEA executive director Hans Bruyninckx said.

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Environmentally friendly groups at Companies vs Climate Change said they will work to make sure Trump won’t undo all the progress the country has made

From his claim that global warming was a gigantic hoax masterminded by China to his promise to pull the United States out of the landmark Paris agreement, Donald Trump’s surprise election win was widely decried by those who feared that recent progress in tackling climate change was about to come undone.

Related: Donald Trump presidency a 'disaster for the planet', warn climate scientists

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Proposals by the Trump administration to roll back US environmental regulations are likely to foment opposition, say analysts.

Buzz Aldrin, the second man on the Moon, is evacuated from the South Pole after falling ill.

The last Tasmanian tiger, or thylacine, is said to have died in 1936 and was declared extinct in 1986. The Thylacine Awareness Group claims there have been 5,000 reported sightings of thylacines in the past 80 years, however, they do acknowledge video evidence is ambiguous

• Footage courtesy of Thylacine Awareness Group YouTube channel
• Tasmanian tiger sightings: ‘I represent 3,000 people who have been told they’re nuts’
  

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Efforts to curb tree clearing have failed, the government admits in its update to Unesco on work to save the world heritage site

Australia needs to work faster on lifting water quality to save the Great Barrier Reef, according to its first progress report to Unesco since the world heritage site was spared an “in-danger” listing.

The report admitted that a key plank of Australia’s conservation plan – land-clearing reforms in Queensland to staunch water pollution – had failed. It also highlighted climate change, which is the biggest threat to the reef and led to the worst recorded coral bleaching in its history this year, but which the plan makes no attempt to address.

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Waitrose, John Lewis and Argos among the first users of a new biomethane fuel for gas-powered trucks, reports BusinessGreen

Gas-powered lorries laden with Christmas parcels are set to have a lighter carbon impact this season thanks to the launch today of a new renewable fuel from CNG Fuels.

Retailers including John Lewis, Argos and Waitrose have already confirmed some of their long-distance lorries will run on the green gas – a renewable biomethane fuel derived from food waste – which is up to 40% cheaper than diesel and emits 70% less carbon dioxide, CNG Fuel says.

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Through the Export-Import Bank, the Obama administration has spent nearly $34bn on dirty energy plants in countries from India to Australia to South Africa

Seemingly little connects a community in India plagued by toxic water, a looming air pollution crisis in South Africa and a new fracking boom that is pockmarking Australia. And yet there is a common thread: American taxpayer money.

Through the US Export-Import Bank, Barack Obama’s administration has spent nearly $34bn supporting 70 fossil fuel projects around the world, work by Columbia Journalism School’s Energy and Environment Reporting Project and the Guardian has revealed.

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Leaves and branches can slow air currents and cause pollutants to settle, says health watchdog

City trees, popularly thought to remove pollutants and improve urban life, may also increase the amount of foul air that people breathe, says the UK body which gives independent health guidance to national and local government.

“Leaves and branches slow air currents, causing pollutants to settle. They may also act as sinks for particulates and chemicals that may have direct or indirect effects in air quality. Air quality [under trees] may deteriorate at street level near vehicles,” says the National Institute for Health and Care Excellence (Nice) in new draft guidance for local government to combat air pollution.

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Unchecked global warming is greatest threat to 21st-century security where mass migration could be ‘new normal’, say senior military

Climate change is set to cause a refugee crisis of “unimaginable scale”, according to senior military figures, who warn that global warming is the greatest security threat of the 21st century and that mass migration will become the “new normal”.

The generals said the impacts of climate change were already factors in the conflicts driving a current crisis of migration into Europe, having been linked to the Arab Spring, the war in Syria and the Boko Haram terrorist insurgency.

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Wolsingham, Weardale Most hedgerow blackthorns are brutally trimmed but these small trees, unpruned and unharvested by birds, are laden with fruit

In early May, this blackthorn thicket had been smothered in the most spectacular display of blossom that I had ever seen and I made a mental note to return in autumn, to see if it had fulfilled its promise.

I’d intended to return sooner. Now it felt like the first real day of winter, and my breath turned to steam in the icy wind. In the shade of the trees beside the beck, where deep shadows would linger all day, fallen leaves were fringed with frost crystals.

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If Western Power shares drop as distributed solar and storage leave grid assets stranded, mums and dads could be left footing the bill.

Record low solar panel prices, and the ratcheting-down or removal of policy levers, are sparking a boom in Australia’s residential and commercial rooftop solar markets – but also prompting warnings to consumers to avoid the lure of cheap and nasty products, and installers.

Start to tourism season prompts environment minister to override federal law and allow the nets in NSW

Josh Frydenberg overrode federal law to give the go-ahead to lethal shark nets in northern New South Wales to save the local tourist industry and nipper clubs.

The environment minister has argued that there was a “national interest” in installing the controversial nets because, with the tourism season about to start, surf shops were experiencing decreased sales and nipper clubs had fewer registrations.

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