I'm at Rottnest Island. Each year over half a million people visit to enjoy a
range of activities. But something that everyone here wants is access to
electricity. Today we're going to discover the orchestra of science and
engineering going into electricity on Rottnest Island.
Rottnest Island has a ridiculous amount of sunny days and they've taken advantage
of that by installing the solar farm. At the moment it's producing about 500
kilowatts of power but that's not all being used - people are out enjoying their
days to the beach and energy demand is low. On the other hand when the Sun goes
down people start turning on their lights and
air-conditioning; so demand goes up- but there is no energy being produced.
We need to find a way of storing the excess energy produced during the daytime and
releasing it during the night when demand is higher.
One common method of energy storage is using hydroelectric dams. As I'm demonstrating for you now they work
by using excess energy to lift water up to a certain height where we can then
use it to fill up a dam. When demand for energy is high but production is
low we can then and release some of the water using it to reduce electricity.
Unfortunately this system isn't going to work for Rottnest. That's because we
don't have high enough mountains to pump water into, and we don't even have enough
water in the first place. Because of these reasons we're going to have to
find an altered of storing energy. Rather than making energy supply meet demand
instead we can make demand meet supply. Behind me is the Rottnnest's desalination
plant. It takes in salty water from the ocean and passes it through a fine-mesh to
take out the salt and gives us fresh water. It's really effective in fact lots
of the water you drink at Rottnest is from this plant. But it's also very energy
intensive taking up a significant portion of Rottnest energy budgets. Once
the salt is removed this water can then be pumped up into one of these massive
storage containers. Combined these can supply the island with about 30 days to
clean drinking water. This means that Rottnest can turn it's
desalination plant on or off depending on renewable energy production as
compared with customer demand. When lots of energy is being produced but people
aren't using it, the desalination plant uses this excess energy to purify water.
When people are using the energy the desalination plant turns back off but
because the storage containers fresh water is still available. The excess power
is there to make up for any deficits, but because the biggest energy drain is
turned off much less fuel needs to be used. Just across from the desalination
plant we have the Rottnest Island wind turbine. At the moment it's producing
about 350 kilowatts power due to the wind blowing in from the Indian Ocean,
but that wind power and the energy being produced can vary wildly over the space
of only a few minutes. Electricity through a wire is bit like water through a host pipe.
Everything that goes in in one end has to come back out or the other. If too
much energy is being supplied, but not enough used then this excess energy will
try to get out in any way that it can; resulting in blown fuses and molten
wires. On the other hand if not enough is being produced then your electronic
devices just won't work. Larger power grids which supply entire cities are a
little bit more robust, but Rottnest's smaller grid has to exactly balance
energy in with energy out. There are two ways of keeping our system stable; have
fine control over supply, or fine control over demand. For supply a common method
is by using a diesel generator. If not enough energy is being produced then we can
speed up the generator. Too much and then slow it down. This does work, but takes a
while to respond to changes in energy because of the larger inertia of the
motor. Another problem is you have to keep it
running at all times, meaning the regardless of how much
renewable energy you're producing you still have to be burning at least some
diesel. The alternative to this is by using a resistor. Behind me is the
solution to Rottnest's power variability problems. This is a dynamic resistor
meaning it can change its impedance to the flow of electricity on a
moment-by-moment basis. As you can see in the infrared, it does this by converting
electrical energy into heat energy. You can increase the resistance if too much
energy is being produced and then decrease it if too little. Because of the dynamic
resistor Rottnest is able to use about five percent less diesel fuel every year.
A question that you might be asking is why don't we just install a really big
battery to solve this problem for us, and that's a good point.
In fact Elon Musk just installed such a system in south
Australia. But there are a few issues with this. First of all it's really
expensive and the lithium used is environmentally damaging. But what I
think is the most important is that what we shown here are Rottnest is that we
Australians have the skills and passion to solve our own problems; finding
solutions that are unique to our own specific circumstance. Of all the things
we've learned here at Rottnest today I think that is the most important.
Massive thank you to the Rottnest Island Authority for letting me come and film here. This
is such an amazing island to explore and I'm so happy that they shared it with us.
New episodes of Perth Science are landing every month so make sure to
subscribe the channel so as not to miss them. Until next time this has been James
Dingley from the Atomic Frontier. Keep Looking Up.