The mine will need to operate 24/7 and the sun don't shine 24 hours and the wind may not blow. Gas provides energy security and reliability, and why I think it might be chosen on this occasion even if the solution is more costlier, but doesn't look the case so far (unless a solar/wind option can work, obviously tied to VRFBs in remote locations of this type for 24/7 operations IMO). Both the the SS and PFS have supported a gas option by the way.
For solar/wind, you will need to either have backup diesel generators (for night time) and/or large battery storage units. Diesel generators, of the scale required, i.e. see below, are IMO expensive to run. You would need to assess this capital cost against the gas option for a 24/7operation, and I suspect gas will be ahead, which is probably why the PFS has gone with gas given remoteness of location and access to a gas pipeline nearby the resource (when assessed on security/reliability issue in particular, unless of course a VRB can be installed to meet the needs of the mine when required with solar/wind operating during the day and for wind during the day and night if the wind blows).
But, given the power requirements of the plant, the wind and solar farm land area would also be very large IMO btw, which feeds into your capex costs. Where solar and wind may have an advantage over gas is around 'capex efficiency' since gas fired plant has thermal efficiencies of 50% whilst you might get more from wind/solar giving bang for buck. But most assume solar has similar thermal efficiency to gas which I find strange to start with btw -
https://en.wikipedia.org/wiki/Solar_thermal_energy and
https://www.sciencedirect.com/science/article/pii/S187661021500497XIn the Pre Feasibility Study (Dec 2018 page 43) the following is stated:
"
The estimated project consumption of natural gasis in the order of 6TJ/day including supplying a build own operate (BOO) natural gas power plant generating electricity for the operation."
6 Terajoules of gas per day roughly equates to a power station need of 40 MW (for gas).
The role of energy in the roasting kilns is significant (not surprising given the heat required in the roasting process is likely to be around 800 to 1000 degrees celsius from recollection) and generating that heat requires a lot of energy/electricity. So people might be able to understand the below, a typical household in Australia consumes annually 7000 kWh electricity, refer
.. 1 megawatt at 90% load factor generate 7884 MWh of electricity (1 *365 days * 24 hours * 90%) or the equivalent of 7,884,000 kWh, so in effect powering 1125 houses for the year. Just putting this down so people can understand the energy requirements below.
6 terajoules per day equates to a power station need of 39.6 MW using certain assumption, so that gives you an idea as to how big your equivalent solar and wind farm needs to be at that scale of MW plant.
Below are my calcs for the gas need, and the opex cost of gas at certain prices (i.e. obviously excludes the capex costs of the pipeline which I can't recall at this stage, and the capex cost for the power plant). Obviously been able to share pipeline and power station costs with TMT will help the capex costs of both projects, but at the moment need to assume there will be no sharing given both TMT and AVL see each other as 'competitors' as against 'friends'.
All IMO
(20min delay)