Hey New Zealanders, here’s a head-scratcher for you: do you know where your electricity comes from?
Unless you’re in the industry, or perhaps a bit of an electricity fiend, you may find it a hard question to answer.
We know that it turns our lights on when we need it, and it runs our washing machines and dryers and ovens. And it seemingly waits patiently behind our light switches and electrical sockets until we need it (quite handy really, that electricity!).
But here at Flick we think the process of electricity generation is right up there with sliced bread. Because, as it turns out, we electricity-users can have a big impact on the electricity mix in NZ. As consumers, we have a lot more power and control over our electricity generation – its cleanliness, its dirtiness, and its related environmental effects – than we realise, and we think it’s about time we all understood how it works.
Electricity Authority statistics show that during 2015 (the 2016 data hasn’t been released yet), New Zealand’s residential, industrial and commercial electricity use totalled 41,342 gigawatt-hours (or GWh – that’s one billion watt hours, or the equivalent of one million kilowatt hours of electricity). So, the big question – what generates all this electricity for us here in New Zealand?
Hydro (produces no greenhouse gas emissions)
The energy harnessed from falling water, or hydro generation, is NZ’s main source of electricity (now that’s something to be proud of). Around 60 per cent of our electricity is generated this way. Hydro generation works by damming water from a lake or river so that when the water is released, it is driven down a pipe and over the blades of a large turbine with such force that it causes the turbine to spin. The turbine is connected to a generator, which converts the turbine movement (kinetic energy) into electrical energy. The water then flows straight out into a river below. Pretty neat, huh?
Here in NZ, we have over 60 hydroelectric power stations, with the mighty Waikato and Waitaki rivers powering 8 hydro stations each. Our hydro dams, like Benmore and Clutha, hold enough water that they can be used as and when they’re needed (they each have a generator that prevents the storage dams from getting too high or too low), although building dams like these does have a heavy environmental impact. Hydro stations powered directly off river flow have their flaws too – they’re at the mercy of the river level, which means we all need to be aware of how much water we’re using during the drier months.
Wind (produces no greenhouse gas emissions)
Wind turbines generate electricity much the same way as hydro generation, except they use energy from the wind to spin the turbines. The faster the wind blows, the faster the turbines spin. And that, of course, means more electricity! Wind farms generate just 5% of our electricity (that’s from an installed capacity of 690 megawatts, according to New Zealand Wind Energy Association), but with the volatile and changeable nature of hydro electricity it seems likely that they’ll take on a much bigger role, especially given that we’re not short of a strong gust or two. At the moment, NZ has 19 wind farms either in operation or under construction.
Wind generation also needs to co-exist with another form of generation, like hydro, because we can’t store the energy produced by turbines. So when the wind stops, or the turbines are locked, back-up generation is used.
Geothermal (produces some greenhouse gas emissions)
NZ is close to the hot mantle below the Earth’s surface, which heats up the ground and gives us those iconic Kiwi treasures of hot pools and geysers. Not only this, our geothermal features provide over 16% of our electricity. Geothermal energy is generated via power stations that work by piping high pressure water and steam from wells under the ground to a generation plant, like Wairakei, just north of Taupo. Just as with hydro and wind generators, the energy from the steam then spins a turbine, creating electricity.
But we need to be careful with our geothermal energy, and it’s always closely monitored. It’s a renewable resource – but with clear environmental impacts. Our large-scale harnessing of geothermal activity has seen a number of geysers and hot pools become extinct, and it has the potential to impact land subsidence, as well as contaminating our rivers and land with waste water chemicals.
Co-generation (produces a moderately high level of greenhouse gas emissions)
Or co-gen. This is the process of using excess energy from the industrial sites of businesses or landfills to produce steam to generate electricity, which is usually then used again on-site. The business saves money by generating their own electricity and steam supply, and puts all of their excess heat to good use. If electricity is produced over and above this, it can then be fed back into the national grid for the rest of us to use – now that’s pretty cool! Co-gen occurs mainly in the upper North Island, in larger, industrial and manufacturing businesses in the wood-processing, steel and dairy industries, and in hospitals.
Coal and gas (produces lots of greenhouse gas emissions)
Both gas and coal are what we call fossil fuels, meaning they’re derived from plant and animal matter, found in the Earth and millions of years old. Naturally, this also means they’re both non-renewable resources (yes, one day we will run out of fossilised trees and Moa poo). The burning of coal and gas is a form of thermal generation. Basically, when they’re burnt their heat is converted to steam, and the pressure of the steam is used to drive a steam turbine.
Coal-fired plants, like the Huntly Power Station, provide around 4% of NZ’s electricity, and in all likelihood they won’t be around for too much longer. Gas provides around 15% of our electricity and produces far less carbon dioxide than coal, though it’s only found in the Taranaki region.
Diesel (produces lots of greenhouse gas emissions)
Yuck. It’s far from our ideal choice as an electricity generator. Thankfully it’s only called into action to generate electricity very occasionally here in NZ, when the conventional forms of generation can’t meet market demand due to low supply.
So what role do we all play in this electricity mix?
Well, because electricity can’t be stored en masse, we each have a role to play in how it’s used. Coming up, we’ll take a look at how each and every one of us can influence the mix of electricity in our grid – because the cleaner it is, the better it is for all of us.