* Most of 36 national grids prepared, except Italy, Poland
* Plant closures tighten Italy's availability
* Poland could run short during early afternoons
By Vera Eckert
FRANKFURT, June 7 (Reuters) - Sustained heatwaves this summer could cause problems for Italian and Polish electricity networks, potentially causing disruption to supplies, but most other grids in Europe look prepared, a power network lobby group warned on Wednesday.
Various grids may require more imports to cover expected demand rises when consumers switch on air conditioning devices and thermal generation plants need more cooling water, ENTSO-E said in its biannual "adequacy report" on 36 countries.
The report covered the outlook from June 1 through Oct. 2 and stretched from central European countries as far as Turkey, Kosovo, Malta, and Burshtyn Island in Ukraine.
Most of Europe should experience above-normal temperatures from June to August, except the northern half of Britain and most of Scandinavia which will be cooler than average, a recent report from the Weather Company predicted.
"Italy has potential supply deficit situations over several weeks between mid-June until the end of July," Alban Joyeau an expert in ENTSO-E's system development group, said in a webinar.
This was due to reduced generation capacity in the North and Central North regions after plant closures and could be worsened by a combination of temperatures above 28 degrees Celsius (82.4°F) and low hydroelectric resources, he said.
But Italy's transmission system operator (TSO), Terna , was preparing to take countermeasures such as more imports, demand side response - when consumers agree to take less electricity - and the temporary use of idled plants.
TSOs are in charge of getting electricity to consumers in an increasingly unified market in Europe, while facing the challenge of more intermittent renewable energy, as countries strive to curb their reliance on carbon-polluting fossil fuels.
ENTSO-E monitors and co-ordinates their efforts to ensure that supply is secure at all times.
Joyeau said Poland could be exposed if there was little or no solar and wind capacity during daytime consumption peaks of 1300 to 1400 Central European Time.
The weeks starting July 17 and July 24 were likely to be most critical, he added.
Although solar capacity in neighbouring Germany is high and could potentially help, Poland's import capacity is limited, which in August 2015 led to enforced plant closures and sent local prices sky-high.
The report also said that there could be some unwanted solar power surpluses in southern Italy and the islands of Sicily and Sardinia during sunny Sundays, when consumption is low.
Electricity flows between the EU's two main power markets, France and Germany, are sizeable and represent capacity equivalent to five nuclear reactors, providing regular and efficient exchanges of supply. (Editing by Alexander Smith)