The plant will have a 40MW installed capacity.
The High Court has stopped the State from acquiring land from the Nairobi National Park.
The project will be tackled by Kenya, Uganda and Rwanda as a block.
The project began in 2009 following the award of the tender to China Road and Bridge.
The first three berths in the port of Lamu will be completed in three years.
The airport will have the capacity to handle heavy commercial aircraft.
This marks the start of the process of construction of the much awaited bypass.
The security system is jointly funded by the World Bank and the Kenyan government.
Experts say the project is likely to destroy the environment, especially mangrove plantations.
17 companies had tendered for the project by the October 12 deadline.