As an AI language model, I can provide information based on the available data up to September 2021. However, please note that the ranking can change as newer projects are announced. Here is a list of some of the largest renewable energy projects announced this year:

1. Asian Renewable Energy Hub (Australia): A mega-project planned for Western Australia, which aims to generate up to 26 gigawatts (GW) of renewable energy from wind and solar sources. The project is being developed by a consortium of companies, including CWP Energy Asia, Intercontinental Energy, and Macquarie Group.

2. Star of the South (Australia): An offshore wind farm proposed in the waters off the coast of Gippsland, Victoria, Australia. If completed, it has the potential to generate up to 2.2 GW of renewable energy, making it the largest offshore wind farm in the southern hemisphere.

3. Aqua Ventus (United States): A floating offshore wind project planned off the coast of Maine, USA. This project, led by the University of Maine and New England Aqua Ventus, aims to develop a 12 MW floating wind turbine prototype.

4. Dogger Bank Wind Farms (United Kingdom): A joint venture between SSE Renewables and Equinor, the Dogger Bank Wind Farms are located in the North Sea and, once fully operational, will have a total capacity of 3.6 GW. It is set to become the world’s largest offshore wind farm.

5. RWE Sofia Offshore Wind Farm (United Kingdom): Sofia Offshore Wind Farm, located on Dogger Bank in the North Sea, would have an installed capacity of 1.4 GW. The project is being developed by RWE and has a potential annual generation capacity equivalent to powering around 1.2 million UK homes.

6. Azov Wind Farm (Russia): A 660 MW wind energy project developed by Enel Green Power, located in the Rostov region of Russia. It is estimated to generate over 2,220 GWh per year upon completion.

7. Enel Green Power’s New Wind Farms (Mexico): Enel Green Power will build three new wind farms in Mexico, totaling 593 MW of capacity. The three projects are Amistad II (168 MW), Amistad III (160 MW), and Amistad IV (265 MW).

8. Floating Solar Power Plant in Indonesia: A 200 MW floating photovoltaic solar power project planned for Indonesia. The facility will be installed on the Cirata Reservoir and is set to be the largest floating solar power plant in Southeast Asia.

9. Solar Power Plant in Bahrain: A 100 MW solar power plant planned for Bahrain, which is part of the country’s efforts to diversify its energy sources. The project will help meet Bahrain’s renewable energy targets.

10. Ørsted’s Hornsea Three Offshore Wind Farm (United Kingdom): Ørsted, a Danish renewable energy company, plans to develop the 2.4 GW Hornsea Three Offshore Wind Farm, located in the North Sea off the coast of England.

Please note that these projects are subject to change based on updates and new announcements.