The company said it may choose to raise up to £120m depending on how its pipeline of potential purchases progresses. The £85m would cover the price of two solar and three onshore wind facilities in the UK and Ireland.
Included within that is the 12 turbine Meikle Carewe wind farm near Stonehaven which is currently owned by RES Group.
The other proposed wind farm purchases are in Cumbria and Rockchapel, County Cork in Ireland.
Both solar parks are still under construction in the south of England but are expected to begin operating by the end of this month.
The five new assets would give TRIG an additional 78 megawatts of generating capacity and taking its overall capacity to 366MW.
It said it is also in discussions about buying other assets which collectively generate more than 200MW.
TRIG already owns wind farms in Caithness, Moray and Ayrshire which it bought as part of its first portfolio of 14 assets. It raised £300m through an initial public offering last year to fund that purchase.
Separately, Eneco UK has bought the Burn of Whilk wind farm near Wick from RWE Innogy UK.