* RWE says needs to respond to strong wind power supply
* Has enough thermal capacity to meet peak winter demand
* Grid firm TenneT says adjusts reserves accordingly
FRANKFURT, Jan 29 (Reuters) - Germany can cope with high wind power supply in coming days which will stress transmission grids already struggling with peak winter demand, power industry firms said on Monday.
It has to rely on better grid management and call up reserve power more often since it switched off eight big nuclear plants in 2011, following a political reaction to the Fukushima nuclear disaster in Japan.
Some experts say the risk of black-outs has risen because although renewable energy over last year provided a good fifth of all power - but it comes and goes in spurts.
Conventional power generation has to provide back-up functions for the volatility, as it can run around the clock.
RWE, Germany's biggest generation company, said that it was prepared to scale back coal-fired and nuclear plants if wind power output should rise to 18 gigawatts (GW) as forecast by meteorologists.
"Conventional power plants will have to respond flexibly," it said in a statement.
The highest demand this winter was seen on Jan. 22 at 84 GW but wind and solar power only delivered 4.3 GW and RWE's thermal power plants produced flat out, it said.
The biggest transmission grid firm TenneT early on Monday made a pre-emptive call for 0.85 GW of reserve power to be activated for the first time this winter to to even out the effect of gusty wind locally.
A spokeswoman for TenneT said on Tuesday that later in the day, there was less of a discernable need, but given notice times, around half of the reserve was producing on Tuesday.
No reserves had been ordered for Wednesday in the early afternoon, she said.
"We have to assess and re-assess the situation as we go along and respond accordingly," she said. "The security buffer is being used as envisaged."
The reserves also serve to counterbalance shortages in particularly cold regions, where spot demand cannot be met easily because of the loss of nuclear plants and excess wind elsewhere is too far away. (Editing by William Hardy)