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Why can’t I use the battery from my electric car to export solar power to the grid when I don’t need it?
Technically it is possible. You could charge your electric vehicle (EV) with solar photovoltaic panels (or any other means), and if the EV is not used, the stored energy could be pushed back into the grid, especially during hours of peak demand for electricity when market prices are high.
This is known as vehicle-to-grid technology and is seen as the future as we move towards more electrification of transport and a smart grid.
But manufacturers of electric vehicles have been reluctant, at first, to allow the bidirectional flow of power, for two reasons.
First, it could accelerate the degradation of batteries, which means they would need to be replaced more often. Second, the EV has to connect to the grid in the same way a solar photovoltaic system does, complying with standards to protect line operators and maintenance personnel working on the grid.
Such advanced bidirectional charge controllers come at an additional cost. Nevertheless, EV manufacturers such as Audi and Nissan have now taken steps to enable vehicle-to-grid connection with some of their models.
For EV models that do not have onboard inverters (to convert the DC electricity in the electric car to AC electricity we use in our homes), there are now bidirectional inverters available to connect any electric car. But the issue of battery life remains.
The continual charging and discharging through a 90% efficient converter shortens the life of the battery, and depending on brand and model, it may need replacing every five years. At more than NZ$5,000, this is a significant price tag for “energy prosumers” – people who both produce and consume energy.
There are other considerations that are very context-specific. These relate to the additional charges for enabling the export of electricity from households, which vary between lines companies and retailers (or local authorities), as well as the buy-back rate of the electricity, which again depends on the purchaser of the electricity.
At the moment, these specific circumstances are seldom favourable to justify the additional cost of the infrastructure needed to connect an electric car to the grid.
There are also practical considerations. If the EV is used for the morning and evening commute, it is not at the home during the day to be charged with a solar system. And if it is (hopefully) not charged during peak demand hours, but mostly in off-peak hours at night, then the vehicle-to-grid route makes less sense.
It only starts to make sense if an EV is not used daily, or if EVs are available to a larger network than just one household. There are major opportunities for EVs to be used in communities with microgrids that manage their own generation and consumption, independent of the larger grid, or if large smart grid operators can manage distributed EVs remotely and more efficiently.
Lithium-ion batteries have changed the world. Without the ability to store meaningful amounts of energy in a rechargeable, portable format we would have no smartphones or other personal electronic devices. The pioneers of the technology were awarded the 2019 Nobel Prize for chemistry.
But as society moves away from fossil fuels, we will need more radical new technologies for storing energy to support renewable electricity generation, electric vehicles and other needs.
One such technology could be lithium-sulfur batteries: they store considerably more energy than their lithium-ion cousins – in theory as much as six times the energy for a given weight. What’s more, they can be made from cheap materials that are readily available around the world.
Until now, lithium-sulfur batteries have been impractical. Their chemistry allows them to store so much energy that the battery physically breaks apart under the stress.
However, my colleagues and I have engineered a new design for these batteries which allows them to be charged and discharged hundreds of times without breaking down. We hope to have a commercial product ready in the next 2–4 years.
What’s so good about sulfur?
Lithium-ion batteries require minerals such as rare earths, nickel and cobalt to produce their positive electrodes. Supply of these metals is limited, prices are rising, and their mining often has great social and environmental costs.
Industry insiders have even predicted serious shortages of these key materials in the near future, possibly as early as 2022.
In contrast, sulfur is relatively common and cheap. Sulfur is the 16th most abundant element on Earth, and miners produce around 70 million tonnes of it each year. This makes it an ideal ingredient for batteries if we want them to be widely used.
What’s more, lithium-sulfur batteries rely on a different kind of chemical reaction which means their ability to store energy (known as “specific capacity”) is much greater than that of lithium-ion batteries.
Great capacity brings great stress
A person faced with a demanding job may feel stress if the demands exceed their ability to cope, resulting in a drop in productivity or performance. In much the same way, a battery electrode asked to store a lot of energy may be subjected to increased stress.
In a lithium-sulfur battery, energy is stored when positively charged lithium ions are absorbed by an electrode made of sulfur particles in a carbon matrix held together with a polymer binder. The high storage capacity means that the electrode swells up to almost double its size when fully charged.
The cycle of swelling and shrinking as the battery charges and discharges leads to a progressive loss of cohesion of particles and permanent distortion of the carbon matrix and the polymer binder.
The carbon matrix is a vital component of the battery that delivers electrons to the insulating sulfur, and the polymer glues the sulfur and carbon together. When they are distorted, the paths for electrons to move across the electrode (effectively the electrical wiring) are destroyed and the battery’s performance decays very quickly.
Giving particles some space to breathe
The conventional way of producing batteries creates a continuous dense network of binder across the bulk of the electrode, which doesn’t leave much free space for movement.
The conventional method works for lithium-ion batteries, but for sulfur we have had to develop a new technique.
To make sure our batteries would be easy and cheap to manufacture, we used the same material as a binder but processed it a little differently. The result is a web-like network of binder that holds particles together but also leaves plenty of space for material to expand.
These expansion-tolerant electrodes can efficiently accommodate cycling stresses, allowing the sulfur particles to live up to their full energy storage capacity.
My colleagues Mainak Majumder and Matthew Hill have long histories of translating lab-scale discoveries to practical industry applications, and our multidisciplinary team contains expertise from materials synthesis and functionalization, to design and prototyping, to device implementation in power grids and electric vehicles.
The other key ingredient in these batteries is of course lithium. Given that Australia is a leading global producer, we think it is a natural fit to make the batteries herea.
We hope to have a commercial product ready in the next 2–4 years. We are working with industry partners to scale up the breakthrough, and looking toward developing a manufacturing line for commercial-level production.
A year ago today, Tesla’s big battery in South Australia began dispatching power to the state’s grid, one day ahead of schedule. By most accounts, the world’s largest lithium-ion battery has been a remarkable success. But there are some concerns that have so far escaped scrutiny.
But not every aspect of Tesla’s big battery earns a big tick. The battery’s own credentials aren’t particularly “green”, and by making people feel good about the energy they consume over summer, it arguably sustains an unhealthy appetite for energy consumption.
The problem of lithium-ion batteries
The Hornsdale Power Reserve is made up of hundreds of Tesla Powerpacks, each containing 16 “battery pods” similar to the ones in Tesla’s Model S vehicle. Each battery pod houses thousands of small lithium-ion cells – the same ones that you might find in a hand-held device like a torch.
It’s important that Tesla is held account to the above claim. A CSIRO report found that in 2016, only 2% of lithium-ion batteries were collected in Australia to be recycled offshore.
However, lithium-ion batteries aren’t the only option. Australia is leading the way in developing more sustainable alternative batteries. There are also other innovative ways to store energy, such as by harnessing the gravitational energy stored in giant hanging bricks.
Tesla’s big battery was introduced at a time when the energy debate was fixated on South Australia’s energy “crisis” and a need for “energy security”. After a succession of severe weather events and blackouts, the state’s renewable energy agenda was under fire and there was pressure on the government to take action.
On February 8, 2017, high temperatures contributed to high electricity demand and South Australia experienced yet another widespread blackout. But this time it was caused by the common practice of “load-shedding”, in which power is deliberately cut to sections of the grid to prevent it being overwhelmed.
A month later, Cannon-Brookes (who recently reclaimed the term “fair dinkum power” from Prime Minister Scott Morrison) coordinated “policy by tweet” and helped prompt Tesla’s battery-building partnership with the SA government.
Since the battery’s inception the theme of “summer” (a euphemism for high electricity demand) has followed its reports in media.
The combination of extreme heat and high demand is very challenging for an electricity distribution system. Big batteries can undoubtedly help smooth this peak demand. But that’s only solving a symptom of the deeper problem – namely, excessive electricity demand.
Time to talk about energy demand
These concerns are most likely not addressed in the national conversation because of the urgency to move away from fossil fuels and, as such, a desire to keep big batteries in a positive light.
But as we continue to adopt renewable energy technologies, we need to embrace a new relationship with energy. By avoiding these concerns we only prolong the very problems that have led us to a changed climate and arguably, make us ill-prepared for our renewable energy future.
The good news is that the big battery industry is just kicking off. That means now is the time to talk about what type of big batteries we want in the future, to review our expectations of energy supply, and to embrace more sustainable demand.
To unlock nature’s secrets, ecologists turn to a variety of scientific instruments and tools. Sometimes we even repurpose household items, with eyebrow-raising results – whether it’s using a tea strainer to house ants, or tackling botfly larvae with a well-aimed dab of nail polish.
But there are many more high-tech options becoming available for studying the natural world. In fact, ecology is on the cusp of a revolution, with new and emerging technologies opening up new possibilities for insights into nature and applications for conserving biodiversity.
Electronically recording the movement of animals was first made possible by VHF radio telemetry in the 1960s. Since then even more species, especially long-distance migratory animals such as caribou, shearwaters and sea turtles, have been tracked with the help of GPS and other satellite data.
But our understanding of what affects animals’ movement and other behaviours, such as hunting, is being advanced further still by the use of “bio-logging” – equipping the animals themselves with miniature sensors.
Many types of miniature sensors have now been developed, including accelerometers, gyroscopes, magnetometers, micro cameras, and barometers. Together, these devices make it possible to track animals’ movements with unprecedented precision. We can also now measure the “physiological cost” of behaviours – that is, whether an animal is working particularly hard to reach a destination, or within a particular location, to capture and consume its prey.
Taken further, placing animal movement paths within spatially accurate 3D-rendered (computer-generated) environments will allow ecologists to examine how individuals respond to each other and their surroundings.
These devices could also help us determine whether animals are changing their behaviour in response to threats such as invasive species or habitat modification. In turn, this could tell us what conservation measures might work best.
Coupling autonomous vehicles with sensors (such as thermal imaging) now makes it easier to observe rare, hidden or nocturnal species. It also potentially allows us to catch poachers red-handed, which could help to protect animals like rhinoceros, elephants and pangolins.
Despite 3D printing having been pioneered in the 1980s, we are only now beginning to realise the potential uses for ecological research. For instance, it can be used to make cheap, lightweight tracking devices that can be fitted onto animals. Or it can be used to create complex and accurate models of plants, animals or other organisms, for use in behavioural studies.
Keeping electronic equipment running in the field can be a challenge. Conventional batteries have limited life spans, and can contain toxic chemicals. Solar power can help with some of these problems, but not in dimly lit areas, such as deep in the heart of rainforests.
“Bio-batteries” may help to overcome this challenge. They convert naturally occurring sources of chemical energy, such as starch, into electricity using enzymes. “Plugging-in” to trees may allow sensors and other field equipment to be powered cheaply for a long time in places without sun or access to mains electricity.
All of the technologies described above sit on a continuum from previous (now largely mainstream) technological solutions, to new and innovative ones now being trialled.
Emerging technologies are exciting by themselves, but when combined with one another they can revolutionise ecological research. Here is a modified exerpt from our paper:
Imagine research stations fitted with remote cameras and acoustic recorders equipped with low-power computers for image and animal call recognition, powered by trees via bio-batteries. These devices could use low-power, long-range telemetry both to communicate with each other in a network, potentially tracking animal movement from one location to the next, and to transmit information to a central location. Swarms of drones working together could then be deployed to map the landscape and collect data from a central location wirelessly, without landing. The drones could then land in a location with an internet connection and transfer data into cloud-based storage, accessible from anywhere in the world.
Realising the techno-ecological revolution will require better collaboration across disciplines and industries. Ecologists should ideally also be exposed to relevant technology-based training (such as engineering or IT) and industry placements early in their careers.
South Australia’s last coal-fired power station closed on Monday this week, leaving the state with only gas and wind power generators.
The Northern Power Station, in Port Augusta on the northern end of the Spencer Gulf, has joined Playford B – the state’s other coal-fired power station which has already been retired.
The coal mine at Leigh Creek that supplied brown coal to the power stations also closed earlier this year, so there is no easy option for re-opening the power stations.
The immediate impact of the closure was a brief wobble in wholesale electricity prices, with more energy brought in from Victoria’s brown coal power stations (adding to carbon emissions).
But how could it affect the state in the long term?
Could South Australia run out of power?
Average electricity demand in South Australia is 1.4 gigawatts, and the state record for peak demand of 3.4 gigawatts was set in January 2011. In the past two years the highest demand was 2.9 gigawatts.
Rollout of rooftop solar panels is one of the reasons demand from the grid has been going down. The impact on the peak demand – the time of day when most people are using appliances – is less clear, because if the peak occurs after sunset, solar panels will not reduce it.
With the closure of the 520 megawatt Northern Power Station, South Australia is left with 2,800 MW of capacity in its gas-fired generators, which can be fired up when needed, and 1,500 MW of wind farms, which of course produce energy only when the wind blows. Most gas generation capacity comes from the Torrens Island A (480 MW) and B (800 MW) installations, built in the 1960s and 1970s, respectively.
There have been discussions about retiring Torrens Island A (it was mothballed for a period in 2014), but the departure of Northern appears to have delayed those plans.
The state also has a total of about 600 MW of rooftop solar, but, as noted above, this technically counts as reducing demand rather than adding to supply.
South Australia is also connected to Victoria via two transmission lines, one at Heywood (recently upgraded to 650 MW) and one at Murray Link (220 MW). This gives the state access to a potential 870 MW of Victorian power.
If South Australia gets close to record demand, the state clearly outstrips the capacity of the local gas generators. If the wind isn’t blowing, then the state will depend on the interconnectors.
It may sound unlikely, but South Australia is at risk of failing to meet demand. This would depend on a very specific set of circumstances:
record demand (despite the increase in rooftop solar reducing demand)
failed interconnectors (or failure of local generators).
A role for storage
This situation means the state is the most likely location for investment in storage. The Australian Renewable Energy Agency (ARENA) recently published a report on storage that identified several locations in South Australia that would be logical places to install commercial-scale batteries.
We at the Melbourne Energy Institute have previously written about pumped hydro storage options, in particular the novel approach of using salt water. This may be of particular use in a very dry state such as South Australia.
But batteries are only going to be attractive investments if there is sufficient volatility in the market to provide arbitrage opportunities. Arbitrage, put simply, is the process of buying low and selling high.
Storage systems need be able to be charged with low-cost energy (for instance, overnight when demand is low, or when the wind is blowing hard) and dispatch the power back onto the grid at a sufficient profit to cover the investment costs.
We are currently in a low-demand period of the year (the shoulder seasons have both low heating and cooling requirements). This means there has not been much shift in electricity prices coming out of South Australia with the removal of Northern. It might not be until next summer, with hot temperatures and increased demand from air conditioners, that we are able to see the true magnitude of the impact of this exit on electricity prices and market volatility.
To date (only a couple of days since the closure), the wind has been blowing hard and there has been no need to increase substantially the generation from other fossil generators. Likewise, there have been no discernible shifts in the spot market prices.
Finally, the impact on carbon emissions will also be interesting. This will depend on how the remaining generators respond. The gap left by Northern may be filled with South Australian gas, in which case total emissions will fall, but more likely the gap will be filled with Victorian coal power via the interconnectors, resulting in no reduction in net emissions.
We will know the net result in due course – watch this space.
The following link is to an article on a major wind power project in Texas, USA. The technology being developed as part of this scheme could be of major importance for energy production and storage around the world. Being able to store electricity generated by wind power in massive batteries is an interesting development.