Storing energy: The final challenge
Renewable power can be harnessed and kept until it is needed, even at household level
We are in the middle of the renewable energy revolution. Prices of solar and wind plants have plummeted. But nature is tricky: wind strength varies and a sometimes shy sun enjoys hiding behind clouds.
Nuclear and coal power stations have an edge because they can provide baseload energy. But rapid advances in renewable energy storage are curtailing this rearguard action.
This process technically kicked off in the mid-1800s, when a French scientist invented the rechargeable lead-acid battery. Humanity’s relationship with energy changed: instead of having to use it immediately, energy could be stored and used at a more convenient time.
Now massive renewable energy plants — generating up to 3 000 megawatts of electrical capacity — are forcing the industry to evolve.
Its objective is simple: create a battery that can store energy for long enough so that renewables can provide predictable energy all year long. Do that and the argument for other baseload energy types vanish.
The greatest challenge is the structure of global energy. Most of this is produced by big utilities. They build big power stations, and send their energy to where it is needed. In South Africa, this means coal-fired power stations in Mpumalanga keep the lights on in East London homes.
The growth of renewables hasn’t changed this. Solar farms in the Northern Cape still have to get their energy to Johannesburg.
But small-scale energy will remove the reliance on these large transmission networks. In even more localised forms, researchers for the United States Army are creating a system that harvests energy from each step taken by soldiers to power their equipment. Going off the grid, once an idea reserved for greenies, is now becoming part of local building regulation. That future is here, and technology is making it mainstream.
Pumped storage
The world’s biggest battery is a pumped storage scheme in Virginia. This uses excess electricity in the day to pump water to the top of a reservoir. That water is then released during peak demand hours, driving turbines and creating 3 000MW worth of energy capacity.
South Africa has two of these schemes along the Drakensberg; the technology is expensive and wastes electricity moving water.
Best renewable on hold
Concentrated solar plants should be the only type of solar built on a large scale. Here, energy coming from solar towers is stored in materials such as molten salt. This allows the energy to sit around when it is not needed, ready to use during peak hours or at night. It is the only renewable that can provide baseload capacity.
The 100MW Ka Xu Solar One plant in the Northern Cape can only store an equivalent amount of energy for 2.5 hours, but other plants in Spain are extending that to 18 hours. The technology should be replacing all other forms of energy, especially in South Africa.
The technology was hamstrung by the 2010 Integrated Energy Plan, the energy department’s planning document for what power capacity should be built. But it did not price concentrated solar properly, overlooking the fact that it is the only renewable that comes with storage. An update to the plan — which showed that concentrated solar is better than conventional solar panels, and called for more to be built — was shelved because the update said the country did not need to build new nuclear plants.
Tiny batteries
Most of the batteries lying around your house will be made from alkaline technology. Electric cars and small storage plants use lead-acid batteries. These technologies are cheap to mass-produce. But they can only handle so many recharges, and are difficult to recycle.
Improvements to small battery technology is therefore at the forefront of research. The first step came with the creation of lithium-ion batteries. These could store more energy in a smaller pack. That advance drove the rise of mobile technology.
Harvard University estimates that the technology needs to store five times more energy in five times less space for these batteries to give renewables a real source of storage.
In the meantime, the university has created metal-free batteries. These borrow from plants and use organic molecules to store energy.
Mobile storage
The internal combustion engine is bad for the environment. It spews out greenhouse gases — warming the world — as well as substances, such as sulphur dioxide, that make people in densely populated areas sick. Replacing diesel and petrol with electricity has been a Holy Grail for developers for decades.
Most of the initial cars that resulted weren’t good — their batteries couldn’t take them far and needed days to recharge.
But recent developments in lithium-ion battery technology mean electric cars can travel 200km between charges, and only need half an hour to charge.
Borrowing from Formula One, the cars now harvest energy from their brakes and other movement and store it. That energy can drive the car, or be used power up a house at night.
The final frontier
Homes are a good illustration of what is wrong with the current energy system: coal is burnt at power stations hundreds of kilometres away, then sent to where it is needed. A quarter of that is lost on the way.
This makes homes the key battleground between utility-scale power generation and smart grids with storage.
But people like Elon Musk, who realise that substantive change can be driven by making things look pretty, are popularising home storage.
A Tesla Powerwall or Nissan xStorage is now something that people want to be seen to have. The former produces 6.4 kilowatt-hours of energy after being charged. That’s enough to power a house overnight (a TV uses 0.1kWh and a washing machine uses 2.3kWh).
Success here means more investment in battery technology. Better batteries mean houses can disconnect from a grid. Office buildings and city blocks will follow. Instead of large-scale energy, every building will create and store its own energy.