Under the terms of the LOI, ESS will prepare the route for the 100-mile interconnector cable for the £1.2bn Caithness-Moray transmission link project.
ABB is responsible for the project’s undersea link.
ESS will undertake boulder clearance operations and pre-lay trenching prior to the laying of the transmission cable, which will run from Spittal in Caithness to Blackhillock in Moray.
Back-fill operations will be carried out thereafter to conceal and protect the cable.
The Caithness-Moray cable is expected to transfer 1.2GW of renewable energy generated in the North of Scotland to the main UK electricity transmission network.
Scottish Energy Minister Fergus Ewing said: "ESS is a significant local employer, with around 80 staff, and its involvement in the Caithness-Moray project will secure an additional 20 jobs over the next two years.
"As well as having significant local and national supply chain benefits, the Caithness-Moray project will enable 1.2GW of new renewable generation to connect to the high-voltage network providing enough electricity to power the equivalent of over 500,000 homes and also making a substantial contribution toward our renewable electricity target.
"Reinforcement of the grid in this resource-rich part of the country will also help to pave the way for future island connections to Orkney and Shetland."
Pre-engineering work has been started already by ESS on the project.
