Issues with renewables have been touted for years, but how far have we come in providing solutions — and can the grid cope?
On the rare occasion we experience a power blackout, we are reminded how reliant modern civilisation is on the electric grid. Anyone who uses a computer or power tools for work will just sit and wait until the power comes back on. If you are at home during a blackout, you will walk around the house for five minutes thinking of things to do, until you realise that most forms of entertainment, communication and even cooking food rely on an electrical power supply. After a few days, or even months of no power, boredom would likely progress to fear. It is no longer a matter of choice when it comes to having access to electricity. We need it. Cities would fall into anarchy, with water, sewerage, schooling, hospital and prison systems all unable to function.
Coal essentially fuelled the first industrial revolution and has provided most of the industrial world with reliable cheap electric power since the early 1900s — shaping the world we know today. But that is no longer a sustainable option. These resources will eventually run out, and the amount of carbon dioxide they produce is steadily changing the climate. We cannot continue to treat the ecosystem like an experiment; seeing how much CO2 we can add to the atmosphere before dealing with a major environmental catastrophe. With Australia’s commitment to the Paris agreement last year, and the goal to reach 100% renewables between 2030 and 2050, renewables remain firmly on the political stage.
What’s the holdup?
In Australia, most of our renewable energy comes from wind and solar. But when the wind isn’t blowing and the Sun’s not shining, we still need other sources like coal and gas to keep the power flowing. We can’t just replace fossil fuel based power stations with renewable energy sources, at least until our storage improves and the costs go down. Fossil fuel based power stations can be built right where they’re needed; by cities which need the most power. But we cannot decide where renewable sources are based. Often we generate the power quite a distance from where it’s needed, (with solar farms built large distances away from each other to soften the effect of clouds passing overhead) which means utilities have to spend huge amounts of money on power lines to get the power to where it needs to go. Transmitting power over long distances is not cheap, and the costs are often overlooked.
But it’s not only where the renewable energy sources are based that is causing problems. There are still too many issues with reliability, as was exposed by an historically large power outage during a storm in South Australia last year, which saw the entire state without power. Naturally, politicians used the event to push their policies before AEMO (Australian Energy Market Operator) was able to release their official report explaining what happened. But the problems arise from how the wind turbines are designed, the way the grid works in a crisis and how renewable energy actually connects into the electricity grid.
Traditional power stations like to work hard. If the output of the station drops, the efficiency also drops, so they like to operate as close to 100% loading as possible. With wind power, most issues stem from either too much, or too little wind.
Once wind speed increases to above 90 kph, wind turbines will apply the brakes to avoid any mechanical or electrical damage. If they’re supplying a large percentage of the total power (and they usually are in South Australia), you end up with a sudden drop in the available power, and the shortfall has to come from somewhere. This is what cause widescale blackouts back in 2016. The same is true if power demand grows and the wind isn’t blowing.
In these situations, the only way to keep up with demand is to import power from Victoria via the Heywood interconnector, which tends to come from coal power stations in the Latrobe valley. As wind farms began to shut down from high winds during the September 2016 South Australian event, the interconnector reached a maximum load and simply disconnected from the state to prevent major damage to equipment. Due to the 2015 closure of the last South Australian coal-fired power station in Port Augusta, the state has become increasingly reliant on the interconnector. When the interconnector failed, the utilities started “load shedding” to ensure there was sufficient supply to hospitals, prisons and other critical infrastructure, creating what’s otherwise known as a “brownout”.
Another reliability issue is to do with the way solar and wind energy are connected to the grid, which makes fluctuations in the supply of power from renewable sources hard to accommodate. This is because of something called grid inertia.
Keeping the frequency at 50 hertz is important for keeping the electric equipment operating correctly, as any sudden, small change in voltage or frequency can cause huge amounts of damage to many forms of equipment. Frequency control is easy for traditional power stations which consist of large spinning turbine generators that have a lot of inertia because of the speed and weight of the rotors. This means they’re very slow at responding to change, and can in fact take over 2 hours to get to full capacity from a cold start.
The inertia from the large moving parts of traditional power stations means that they can all be integrated into the grid together quite efficiently. Imagine a group of carousels linked together with a belt. If a bunch of kids all jump on at once it wouldn't slow down because of the collective momentum of the system. But wind and solar, which don’t have a lot of heavy moving parts, are considered ‘non-synchronous’ and don't add any inertia to the system. In South Australia, the largest power stations — or carousels — are shutting down. But being ‘non-synchronous’ does have its benefits. Because wind and solar respond very quickly to change, they are able to connect to the grid instantly as there are no laggy mechanical parts that we need to wait for.
This is why adding small amounts of renewables to a grid is quite simple, but with increasing percentage of the power coming from renewables — such as in South Australia — the logistics become complicated; especially when modern day society expects uninterrupted power 24/7.
Are we there yet?
Battery storage has the potential to dramatically improve the stability of the grid, rendering fossil fuel generation redundant. Better batteries mean we could store all the excess energy when the wind is blowing hard and the sun is beating down; which is why the Tesla Powerwall is causing such a stir.
Earlier this year, Elon Musk announced that the Gigafactory in the Nevada desert had started production of Lithum-ion battery cells, which are already being used in the Tesla Powerwall. By 2018, the factory will double the worldwide production of lithium batteries, with the factory likely to triple in size again. Musk is quite confident in the potential of his battery storage systems and even tweeted recently regarding the power network problems in South Australia:
These systems aren’t yet cost effective. As products like the Powerwall become cheaper, it will become a worthwhile investment for households so they can store any excess power generated from solar panels, or even store power during off-peak so they don’t have to pay the higher on-peak rates. But it’s still not efficient enough (or cheap enough!) for large power stations.
There is another way to store the unused power. Pumped hydro storage is currently the most efficient and popular method. This simply involves pumping water uphill during times of surplus power, then using that water to generate power during peak times.
A smarter grid
Even with all this new technology coming in, our power infrastructure is aging, and a lot of equipment is being pushed to do more than it was originally designed for. Engineers are slowly modernising the grid and increasing resiliency by adding two-way channels of communication between consumer and provider. The customer benefits by getting more control over their usage and access to their data. Power utilities benefit by having more information to control the grid, reduce peak loads, and the ability to quickly sense faults in the grid and re-route power around such faults. A pilot program to use smart meter information to control the supply voltage is currently being implemented in Melbourne. If the trial is successful, we will likely see this rolled out around the country.
As the electric car industry takes off, there’s also the possibility that all the car batteries just sitting parked in garages could be connected to the smart grid, with the power companies paying for the ability to store energy in people cars.
Microgrids are another way to increase the benefits of renewables while also making the main grid more resilient. Microgrids can separate from the main grid during an outage and continue to operate autonomously as an 'island' with the ability to connect back to the main grid seamlessly. These systems work perfectly with wind and solar because of the potential for self-sufficiency. As you can imagine, there are many challenges in transitioning from a 100-year-old hierarchical type grid, into a modern grid which allows small scale renewables to supply power horizontally. But progress is being made.
If reducing CO2 emissions is the primary goal, then combining renewables with nuclear is an idea that’s often mentioned. Along with having zero emissions, nuclear power plants provide very reliable base load and you can build them wherever power is needed. This would solve many of renewables’ issues — like inconsistency and plant location. There are hundreds of plants already operating around the world with over 60 new plants currently being built. New technologies are on the horizon which use thorium (an element more abundant than uranium) or nuclear waste as fuel. These systems would be over 90% efficient and inherently much safer than traditional nuclear plants. Despite the huge potential of nuclear power, there are definitely large risks involved with disaster and managing waste. If Australia goes down the nuclear path, we would need to take advantage of the latest technology to ensure the safety of people and the environment.
If the power industry can solve the issues of intermittency and grid inertia, we will be on track to meet the carbon reduction goals. The electricity market regulators (AEMO) projected how Australia could meet the target of 100% renewables between 2030 to 2050 in a report in 2013. While the report indicates that it’s possible to reach this target, the system would require much higher capacity reserves, which would mean building a lot of renewables that usually don't get used. The study assumed current day renewable technology would be used, and did not consider nuclear power.
However we meet this goal, it’s going to be expensive. I guess that’s the price we must pay to ensure that future generations aren’t left with an irreparable ecosystem. If long term economic growth is really what our policy makers want, preventing climate change should be of utmost importance. Adjustments to the grid, improvements in storage technology and renewables, might just get us there.
Edited by Bryonie Scott and Tessa Evans