100% target achievement

Tasmania is taking 10,500 gigawatt hours (GWh) per year as a baseline consumption.

While this might seem simple, because Tasmania is part of the interconnected National Electricity Market, it is more complex. Every minute of every day consumption levels fluctuate, as does energy generation from rainfall, wind and solar photovoltaic panels.

This is why we have taken the approach to look at average annual consumption (expressed in gigawatt hours per year) balanced against the expected annual average renewable energy generation, based on installed capacity and average generation. This can be summarised as:

Expected annual renewable energy generation from installed Tas renewables ≥ average annual demand

Tasmania has now reached a position, following the commissioning of the Cattle Hill Wind Farm and the 29 (of 31) turbines at Granville Harbour Wind Farm, where we can confidently say that we now have the installed capacity to meet our annual electricity needs from on-island renewable energy generation.

In 2017, the Tasmanian Energy Security Taskforce assessed the long term average inflows to the hydro storages as being the equivalent of 9 000 GWh per year. This is a conservative estimate, developed by the Taskforce after extensive consultation with Hydro Tasmania.

Tasmania is also blessed with a world class wind resource. We have 308 megawatts (MW) of installed capacity at the windfarms at Woolnorth (Bluff Point and Studland Bay) and at Musselroe.

The state’s new wind farms, at Cattle Hill and Granville Harbour, bring an additional 148.4 MW and 104.4 MW of installed capacity. This brings our total installed capacity for wind generation to 560.8 MW. This capacity will increase to 568 MW when Granville Harbour’s two final turbines are fully commissioned in mid-December 2020.

Wind, like rain, can vary from season to season, but Tasmania is blessed with a world class wind resource.  The “capacity factor” of a wind farm represents the average output of a wind farm against its installed capacity.

For example, a wind farm with an installed capacity of 100 MW and a capacity factor of 40 per cent would have its expected output calculated by multiplying its capacity of 100 MW by 8,760 hours in the year by 40 percent. This would equal 350,400 megawatt hours (MWh), or 350.4 GWh.  In AEMO’s 2019 Integrated System Plan, the capacity factor for wind in the relevant Tasmanian locations has been assessed as ranging from 37 per cent to a potential maximum of 51 per cent in some years.

We have taken a very conservative approach, and used a 35 per cent capacity factor to calculate expected wind generation output.

Based on this calculation, our combined total of 560.8 MW of installed wind capacity could be expected to generate 1,719 GWh of electricity in a year. This means that, with commissioning of 29 of the 31 turbines at the Granville Harbour Wind Farm, Tasmania now has the installed capacity and conservatively estimated expected yield from the combined hydro system and wind farms to be able to generate, on a net basis, just over 10,719 GWh per year of renewable electricity. This is illustrated in Table 1 below.

Using our methodology, we can apply this total generation output as follows:

Expected annual renewable energy generation from installed Tas renewables of 10,719.41 GWh is greater than baseline consumption of 10,500 GWh.

What happens if we have a dry year and we don’t get the same amount of rainfall?

Some years we have less rain, and some years we have more rain.  On average we can expect to have enough rain so that inflows to Tasmania’s hydro dams are sufficient to generate a robust 9 000 gigawatt hours per year. Some years we may have less, but this will be balanced by the years when we have more. In the years when we have more rainfall, we will be able to generate more than 100 per cent of our baseline needs.  And this is when we will be on net export – selling reliable, renewable energy into the national grid.

Does this mean that all the electricity Tasmanians use will always be from renewable sources?

Not quite. That is why we refer to meeting our target on a "net basis". Hydro Tasmania will still import electricity via Basslink, and we may still, on occasions, need to use gas-fired generation at the Tamar Valley Power Station.

Why will we still be importing electricity from the mainland?

The way the national electricity market works means that we can import electricity from the mainland at times when Victorian prices are particularly low.  This means that we can keep water in our major storages, our “batteries”, so that we have enhanced energy security.  It also means that when electricity demand and prices in Victoria are higher, we can export electricity to the mainland.

Why do we still need the gas fired power station in the Tamar Valley?

The Energy Security Annual Report, issued by the independent Monitor and Assessor, notes that the Tamar Valley Power Station (TVPS) at Bell Bay provides diversity and acts as a safeguard in Tasmania’s energy mix.  It contributes to Tasmania’s energy security, though its utilization has been decreasing with the development of wind generation in the State.

What about including solar energy?

Tasmania currently has around 31 000 customers with connected solar PV systems [1].  Much of the generation is used by the households or businesses where it is installed and cannot be independently measured.  It is estimated that solar contributes in the order of 200 GWh per year, or around 2 per cent of consumption.[2] This includes both the electricity consumed on the premises as well as exported to the grid.

What about gas, LPG, and fuel for cars?

The target relates only to renewable sources for electricity generation.  Gas and other fuel sources still have a place while they are the most practical and economic options, particularly for direct heat and for transport.

Future innovations, including the opportunities presented from hydrogen technology, and the potential for electric vehicles, will provide greater opportunities for emissions reductions beyond the electricity generation sector.

[1] OTTER Energy in Tasmania Annual Report, February 2020

[2] Source – Opennem.org.au, based on data from AEMO Bureau of Meteorology and the Australian PV Institute