People have used moving water to create energy for thousands of years. Today, pumped hydro is the most common form of grid-connected energy storage in the world.
This technology is in the spotlight because it pairs so well with solar and wind renewable energy. During the day, when solar panels and wind farms may be generating their highest level of energy, people don’t need really need much electricity. Unless it is stored somewhere the energy is lost.
Pumped hydro can cheaply and easily store the excess energy, releasing it again at night when demand rises.
Here’s how it all works:
How it works
Put as simply as possible, it involves pumping water to a reservoir at the top of a hill when energy is in plentiful supply, then letting it flow back down through a turbine to generate electricity when demand increases.
Like all storage systems, you get less energy out than you put in – in this case, generally around 80% of the original input – because you lose energy to friction in the pipes and turbine as well as in the generator. For comparison, lithium ion batteries are around 90-95% efficient, while hydrogen energy storage is less than 50% efficient
The benefit is we can store a lot of energy at the top of the hill and keep it there in a reservoir until we need the energy back again. Then it can be released through the pipes (this is called “penstock”) to generate electricity. This means pumped hydro can create a lot of additional electricity when demand is high (for example, during a heatwave).
The disadvantage of pumped hydro is you need to have two reservoirs separated by a significant elevation difference (more than 200m is typically required, more than 300m is ideal). So it doesn’t work where you don’t have hills. However, research has identified 22,000 potential sites in Australia.
Pumped hydro is traditionally paired with relatively inflexible coal or nuclear power stations, using under-utilised electricity when demand is low (weekends and nighttime), then providing additional generation when demand increases during the day and into the evening.
With the rapid increase in deployment of wind and solar, pumped hydro is again gaining interest. This is because the output of wind and solar plant is subject to the variability in the weather. For example, solar power plants generate the most electricity in the middle of the day, while demand for electricity is often highest in the evening. The wind might die down for hours or even days, then suddenly blow a gale. Pumped hydro can play a key role in smoothing out this variability.
If the electricity being produced by wind and solar plant is greater than demand, then the energy has to be curtailed (and is lost), unless we have a way to store it. Using this excess power to pump water up hill means the solar or wind energy is not wasted and the water can be held in reservoirs until demand rises in the evening.
There are lots of different kinds of energy storage technologies, each with their own advantages and disadvantages. For large-scale grid-connected systems where many hours of storage are required, pumped hydro is the most economically viable option.
The world can limit global warming to 1.5℃ and move to 100% renewable energy while still preserving a role for the gas industry, and without relying on technological fixes such as carbon capture and storage, according to our new analysis.
The One Earth Climate Model – a collaboration between researchers at the University of Technology Sydney, the German Aerospace Center and the University of Melbourne, and financed by the Leonardo DiCaprio Foundation – sets out how the global energy supply can move to 100% renewable energy by 2050, while creating jobs along the way.
It also envisions how the gas industry can fulfil its role as a “transition fuel” in the energy transition without its infrastructure becoming obsolete once natural gas is phased out.
increasing electrification in the heating and transport sector
significant increase in “energy productivity” – the amount of economic output per unit of energy use
the phase-out of all fossil fuels, and the conversion of the gas industry to synthetic fuels and hydrogen over the coming decades.
Our model also explains how to deliver the “negative emissions” necessary to stay within the world’s carbon budget, without relying on unproven technology such as carbon capture and storage.
If the renewable energy transition is accompanied by a worldwide moratorium on deforestation and a major land restoration effort, we can remove the equiavalent of 159 billion tonnes of carbon dioxide from the atmosphere (2015-2100).
We compiled our scenario by combining various computer models. We used three climate models to calculate the impacts of specific greenhouse gas emission pathways. We then used another model to analyse the potential contributions of solar and wind energy – including factoring in the space constraints for their installation.
We also used a long-term energy model to calculate future energy demand, broken down by sector (power, heat, industry, transport) for 10 world regions in five-year steps. We then further divided these 10 world regions into 72 subregions, and simulated their electricity systems on an hourly basis. This allowed us to determine the precise requirements in terms of grid infrastructure and energy demand.
‘Recycling’ the gas industry
Unlike many other 1.5℃ and/or 100% renewable energy scenarios, our analysis deliberately integrates the existing infrastructure of the global gas industry, rather than requiring that these expensive investments be phased out in a relatively short time.
Natural gas will be increasingly replaced by hydrogen and/or renewable methane produced by solar power and wind turbines. While most scenarios rely on batteries and pumped hydro as main storage technologies, these renewable forms of gas can also play a significant role in the energy mix.
In our scenario, the conversion of gas infrastructure from natural gas to hydrogen and synthetic fuels will start slowly between 2020 and 2030, with the conversion of power plants with annual capacities of around 2 gigawatts. However, after 2030, this transition will accelerate significantly, with the conversion of a total of 197GW gas power plants and gas co-generation facilities each year.
Along the way the gas industry will have to redefine its business model from a supply-driven mining industry, to a synthetic gas or hydrogen fuel production industry that provides renewable fuels for the electricity, industry and transport sectors. In the electricity sector, these fuels can be used to help smooth out supply and demand in networks with significant amounts of variable renewable generation.
A just transition for the fossil fuel industry
The implementation of the 1.5℃ scenario will have a significant impact on the global fossil fuel industry. While this may seem to be stating the obvious, there has so far been little rational and open debate about how to make an orderly withdrawal from the coal, oil, and gas extraction industries. Instead, the political debate has been focused on prices and security of supply. Yet limiting climate change is only possible when fossil fuels are phased out.
Under our scenario, gas production will only decrease by 0.2% per year until 2025, and thereafter by an average of 4% a year until 2040. This represents a rather slow phase-out, and will allow the gas industry to transfer gradually to hydrogen.
Our scenario will generate more energy-sector jobs in the world as a whole. By 2050 there would be 46.3 million jobs in the global energy sector – 16.4 million more than under existing forecasts.
Our analysis also investigated the specific occupations that will be required for a renewables-based energy industry. The global number of jobs would increase across all of these occupations between 2015 and 2025, with the exception of metal trades which would decline by 2%, as shown below.
However, these results are not uniform across regions. China and India, for example, will both experience a reduction in the number of jobs for managers and clerical and administrative workers between 2015 and 2025.
Our analysis shows how the various technical and economic barriers to implementing the Paris Agreement can be overcome. The remaining hurdles are purely political.
Summer is here with a vengeance. On hot days it’s very likely something in the power system will break and cause someone to lose power. And the weather bureau expects this summer to be hotter and drier than average – so your chances of losing power will be higher than normal.
We’ve analysed outage data from the electricity distribution networks over the past nine years and linked it to Bureau of Meteorology maximum daily temperature data for each distribution network. The findings are stark: customers are without power for 3.5 times longer on days over 35 degrees than on days below 35.
Hot weather puts more stress on all parts of the power system. Wires sag and short, fuses blow, transformers overheat, and fires and storms damage power lines. And demand spikes when people get home from work and turn on the air-conditioner.
When the air-conditioner doesn’t work during a heat wave, people get upset and politicians rush to assign blame. They often point the finger at a lack of electricity generation capacity – just ask the current federal energy minister, who responded to a report forecasting supply shortages in Victoria this summer by saying:
This is a direct result of Victorian government policies forcing out reliable 24/7 power, and a failure to prioritise firming of heavily subsidised intermittent wind and solar generation.
There have been generation shortfalls in Australia on only three days in the past fourteen years, whereas there are network failures every summer all around the country, every year.
The last time a lack of generation affected large numbers of customers was in Victoria and South Australia in January 2009. But even on very hot days that summer, Victorians and South Australians lost 14 times more power because of network failures and weather damage than generation shortfalls.
Outages caused by generation shortfalls are also easier to manage than network problems. Power can be restored at a flick of a switch, as soon as demand falls or supply increases. And the blacked-out areas can be rotated, to reduce the impact on any individual customer. By contrast, if your power goes out because of a network failure or storm damage, you’re stuck with the problem until a crew can come out and fix it.
Our analysis of outages shows almost all customers affected by generation shortfalls in 2009 were back on line in less than an hour. By contrast, if your power goes out for other reasons, you will normally be waiting more than an hour to get back on line. In the worst cases, you can be left waiting for more than five hours.
What should we do (or not) about summer blackouts?
The main thing governments should to address summer blackouts is… nothing, just sweat it out. If governments over-react to newspaper headlines about blackouts, customers will pay more in the long run. Power failures on a hot day are unpleasant, but the bill to avoid them entirely would almost certainly be worse.
Blackouts in 2004 prompted the New South Wales and Queensland state governments to tighten network reliability standards. This caused over $18 billion of network over-spending and delivered only modest improvements in reliability. Network costs were the largest cause of increasing residential electricity prices in those states over the past decade, which increased more than 50% above inflation in New South Wales, and more than 70% in south-east Queensland.
Customers are unlikely to be willing to pay for more network “gold-plating”. Research by Energy Consumers Australia shows more customers are satisfied with the reliability of their power supply than with the price they pay.
Customers can also play an important role. If your power does go out, don’t buy into the political blame game. Contrary to the impression the politicians and media might give, it’s very unlikely the outage will have been caused by a lack of power supply – whether coal, gas or renewable.
So be sceptical when a hot-headed politician tells you the solution is their preferred energy generation technology. Neither a new coal-fired power station nor a giant solar-fed battery will keep the power on if your local network fails.
Opposition Leader Bill Shorten announced last week that a federal Labor government would create a Just Transition Authority to overseee Australia’s transition from fossil fuels to renewable energy. This echoes community calls for a “fast and fair” energy transition to avoid the worst impacts of climate change.
Based purely on the technical lifetime of existing power stations, the Australian market operator predicts that 70% of coal-fired generation capacity will be retired in New South Wales, South Australia and Victoria by 2040. If renewables continue to fall in price, it could be much sooner.
We must now urgently decide what a “just” and “fair” transition looks like. There are many Australians currently working in the energy sector – particularly in coal mining – who risk being left behind by the clean energy revolution.
Coal communities face real challenges
The history of coal and industrial transitions shows that abrupt change brings a heavy price for workers and communities. Typically, responses only occur after major retrenchments, when it is already too late for regional economies and labour markets to cope.
Coal communities often have little economic diversity and the flow-on effects to local economies and businesses are substantial. It is easy to find past cases where as many as one third of workers do not find alternative employment.
We often hear about power stations, but there are almost 10 times as many workers in coal mining, where there is a much higher concentration of low and semi-skilled workers. The 2016 Census found almost half of coal workers are machinery operators and drivers.
The demographics of coal mining workers in Australia suggest natural attrition through early retirements will not be sufficient: 60% are younger than 45.
Mining jobs are well paid and jobs in other sectors are very unlikely to provide a similar income, so even under the best scenarios many will take a large pay cut.
Another factor is the long tradition of coal mining that shapes the local culture and identity for these communities. Communities are particularly opposed to change when they experience it as a loss of history and character without a vision for the future.
Lastly, the local environmental impacts of coal mining can’t be neglected. The pollution of land, water and air due to mining operations and mining waste have created brownfields and degraded land that needs remediation.
However, using the concept of energy justice, there are three main aspects which have to be considered for workers, communities and disadvantaged groups:
distributing benefits and costs equally,
a participatory process that engages all stakeholders in the decision making, and
recognising multiple perspectives rooted in social, cultural, ethical and gender differences.
A framework developed at the Institute for Sustainable Futures maps these dimensions.
A just transition requires a holistic approach that encompasses economic diversification, support for workers to transition to new jobs, environmental remediation and inclusive processes that also address equity impacts for marginalised groups.
The politics of mining regions
If there is not significant investment in transition plans ahead of coal closures, there will be wider ramifications for energy transition and Australian politics.
In Australia, electricity prices have been at the centre of the “climate wars” over the past decade. Even with the steep price rises in recent years, the average household still only pays around A$35 a week. But with the closure of coal power plants at Hazelwood and Liddell, Australia is really only just getting to the sharp end of the energy transition where workers lose jobs.
There are some grounds for optimism. In the La Trobe Valley, an industry wide worker redeployment scheme, investment in community projects and economic incentives appears to be paying dividends with a new electric vehicle facility setting up.
AGL is taking a proactive approach to the closure of Liddelland networks are forming to diversify the local economy. But a wider transition plan and investment coordinated by different levels of government will be needed.
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.
Low energy efficiency is already a major problem for petrol and diesel vehicles. Typically, only 20% of the overall well-to-wheel energy is actually used to power these vehicles. The other 80% is lost through oil extraction, refinement, transport, evaporation, and engine heat. This low energy efficiency is the primary reason why fossil fuel vehicles are emissions-intensive, and relatively expensive to run.
Based on a wide scan of studies globally, we found that battery electric vehicles have significantly lower energy losses compared to other vehicle technologies. Interestingly, however, the well-to-wheel losses of hydrogen fuel cell vehicles were found to be almost as high as fossil fuel vehicles.
At first, this significant efficiency difference may seem surprising, given the recent attention on using hydrogen for transport.
and finally deliver hydrogen to a fuel cell vehicle.
Herein lies one of the significant challenges in harnessing hydrogen for transport: there are many more steps in the energy life cycle process, compared with the simpler, direct use of electricity in battery electric vehicles.
Each step in the process incurs an energy penalty, and therefore an efficiency loss. The sum of these losses ultimately explains why hydrogen fuel cell vehicles, on average, require three to four times more energy than battery electric vehicles, per kilometre travelled.
Electricity grid impacts
The future significance of low energy efficiency is made clearer upon examination of the potential electricity grid impacts. If Australia’s existing 14 million light vehicles were electric, they would need about 37 terawatt-hours (TWh) of electricity per year — a 15% increase in national electricity generation (roughly equivalent to Australia’s existing annual renewable generation).
But if this same fleet was converted to run on hydrogen, it would need more than four times the electricity: roughly 157 TWh a year. This would entail a 63% increase in national electricity generation.
A recent Infrastructure Victoria report reached a similar conclusion. It calculated that a full transition to hydrogen in 2046 – for both light and heavy vehicles – would require 64 TWh of electricity, the equivalent of a 147% increase in Victoria’s annual electricity consumption. Battery electric vehicles, meanwhile, would require roughly one third the amount (22 TWh).
Some may argue that energy efficiency will no longer be important in the future given some forecasts suggest Australia could reach 100% renewable energy as soon as the 2030s. While the current political climate suggests this will be challenging, even as the transition occurs, there will be competing demands for renewable energy between sectors, stressing the continuing importance of energy efficiency.
It should also be recognised that higher energy requirements translate to higher energy prices. Even if hydrogen reached price parity with petrol or diesel in the future, electric vehicles would remain 70-90% cheaper to run, because of their higher energy efficiency. This would save the average Australian household more than A$2,000 per year.
Pragmatic plan for the future
Despite the clear energy efficiency advantages of electric vehicles over hydrogen vehicles, the truth is there is no silver bullet. Both technologies face differing challenges in terms of infrastructure, consumer acceptance, grid impacts, technology maturity and reliability, and driving range (the volume needed for sufficient hydrogen compared with the battery energy density for electric vehicles).
Battery electric vehicles are not yet a suitable replacement for every vehicle on our roads. But based on the technology available today, it is clear that a significant proportion of the current fleet could transition to be battery electric, including many cars, buses, and short-haul trucks.
Such a transition represents a sensible, robust and cost-efficient approach for delivering the significant transport emission reductions required within the short time frames outlined by the Intergovernmental Panel on Climate Change’s recent report on restraining global warming to 1.5℃, while also reducing transport costs.
Together with other energy-efficient technologies, such as the direct export of renewable electricity overseas, battery electric vehicles will ensure that the renewable energy we generate over the coming decades is used to reduce the greatest amount of emissions, as quickly as possible.
Meanwhile, research should continue into energy efficient options for long-distance trucks, shipping and aircraft, as well as the broader role for both hydrogen and electrification in reducing emissions across other sectors of the economy.