References
https://www.hindawi.com/journals/mpe/2010/684742/
https://www.sciencedirect.com/science/article/abs/pii/S0925231201007020
http://www.caiso.com/market/Pages/ReportsBulletins/RenewablesReporting.aspx
https://www.bp.com/en/global/corporate/energy-economics/statistical-review-of-world-energy.html