transmission systems. The Central Interconnected System (SIC) serves principally household consumers, while the "Large North" Interconnected System (SING) mostly serves large industrial customers, primarily mining interests in Chile's northern regions. The largest generating company in the SING is Electroandina, owned by Tractebel and Codelco. Renewable energy resources In January 2006, new legislation was passed to apply the benefits included in Short Laws I & II (see Recent Developments section below for details) to renewable energy production. The new regulation provided for exemptions in transmission charges for new renewable energy sources (i.e. geothermal, wind, solar, biomass, tidal, small hydropower and cogeneration) below 20 MW of capacity. It also simplified the legal procedures for projects below 9 MW. Previously, besides hydro, no other renewable source had a significant contribution to the Chilean energy mix, but this has changed. Hydro At the end of 2021 Chile was the 28th country in the world in terms of installed hydroelectric power (6.8 GW). Historically, hydroelectric plants have been the largest power source in Chile. Periodical droughts have, however, caused supply shortfalls and blackouts, which led the government to increase diversification in the country's energy mix in the 1990s, mainly through the addition of natural-gas-fired power plants. Nevertheless, hydropower projects continued to be carried out, with the 570 MW Endesa's Ralco plant, on the Biobio River, being the best example as the largest power plant in Chile. The construction of this plant was long delayed by opposition from local residents and environmental activists, but it finally began operations in 2004, the year when it also got the approval from Chile's environmental authority to be expanded to a capacity of 690 MW. Furthermore, Argentina's gas crisis has revitalized other hydropower projects in Chile. In 2007–8, Chilean power generator Colbun completed three hydroelectric projects, the 70 MW Quilleco plant on the Laja River and the Chiburgo and Homito plants, with 19 MW and 65 MW generation capacity respectively. In addition, in 2007 Endesa started operating the 32 MW Palmucho plant, which is to work in conjunction with Ralco's facility. Finally, Australia's Pacific Hydro and Norway's SN Power Invest are developing the 155 MW La Higuera and the 156 MW La Confluencia hydroelectric plants on the Tinguiririca River. The controversial 2,750 MW HidroAysén project was cancelled in 2014. Solar power At the end of 2021 Chile was the 22nd country in the world in terms of installed solar energy