* So far, no blackouts due to power supply shortages
* Tesla battery wins kudos for stabilising grid
* February demand may yet stress the network
By Sonali Paul
MELBOURNE, Feb 5 (Reuters) - Australia's strained power supply grid has largely withstood soaring temperatures this summer, but a year after the nation's biggest city, Sydney, was hit by blackouts, the real test comes this month.
Outages in February, when demand typically peaks as schools, factories and offices return to full swing and temperatures can soar above 40 degrees C (104 degrees F), could reignite a national debate over the push for renewable energy.
A state-wide blackout in South Australia in September 2016 sparked a conservative backlash over the use of solar and wind at the expense of dirtier but 'always-on' coal-fired generation and a scramble to add back-up power.
So far this summer, so good. South Australia, the country's most wind energy-dependent state, has installed the world's biggest lithium ion battery from Tesla Inc and diesel generators. The only outages have been due to fuse faults on the distribution network.
"If the lights went out in South Australia, it's likely you'd have the blame put squarely on renewables," said Dylan McConnell, a researcher at the University of Melbourne's Climate and Energy College.
The state's new power supply was part of an emergency A$550 million ($435 million) energy plan unveiled by last March to ensure homes would not be left in the dark and industry would not be crippled again.
"South Australia has experienced two heat waves this summer, and our system coped very well," state Energy Minister Tom Koutsantonis said in comments emailed to Reuters.
The Tesla battery has dispatched power dozens of times since it was switched on in late November, including injecting 100 megawatts of power in a split second when a unit at the biggest coal-fired power station in neighbouring Victoria tripped in December.
It has also been credited with helping to keep wholesale prices down by providing competition for expensive fast-start gas-fired power that is otherwise tapped to stabilise network frequency.
The state hasn't needed to use its dirty diesel power yet. Australia's energy market operator leapt into action, too, including persuading three generators to revive mothballed gas-fired plants and setting up a A$70 million programme to pay some power users to curb their demand, following the closure of the market's dirtiest coal-fired plant, Hazelwood, in March.
"We are pleased with the performance of the power system so far under some extreme conditions already experienced," Australian Energy Market Operator spokeswoman Avi Tan said.
The market operator did not want to speak too soon on the outlook for February, saying it would provide a full report on how the system performed at the end of summer.
Miners hit hardest by outages in South Australia in 2016 and early 2017 are relieved that all the measures to beef up power reserves have worked so far, after leading calls to tackle what they saw as a looming crisis as coal-fired plants shut down with the rapid rise of wind power.
Global miner BHP had to shut its Olympic Dam copper mine in outback South Australia for two weeks after a 2016 blackout, while aluminium giant Alcoa's Portland smelter narrowly averted permanent closure after an outage caused molten aluminium to freeze solid.
"February is typically a time of peak demand," said Rebecca Knol, chief executive of the South Australia Chamber of Mines and Energy.
"There are always extreme weather events, but I think we're much better positioned to deal with those this year."
Knol said it didn't matter how much the Tesla battery had cost the state -- a figure which the government and the company have declined to reveal.
"What we're all after is system security here. So if it has provided system security, then it has done its job."
($1 = 1.2609 Australian dollars)
Reporting by Sonali Paul; editing by Richard Pullin