The German manufacturer will install six of its N90-2500 machines on the 15MW Jack's Lane wind farm in Norfolk in the east of England.
Woolley Hill wind farm in Cambridgeshire, also in eastern England, with a capacity of 10MW, will feature the N100-2500 turbine.
Construction of some of the infrastructure has already begun at both projects. The turbines are due to be delivered in the middle of the year, with commissioning due before the end of 2014.
RES and Nordex have previously worked together on several projects in Northern Ireland with a total installed capacity of 90MW.