Arlington-based The AES Corp. and Canada-based Alberta Investment Management Corp. (AIMCo) said Friday they have agreed to acquire FTP Power LLC (sPower) for $853 million in cash and the assumption of $724 million in debt. Salt Lake City-based sPower is the largest independent owner, operator and developer of utility scale solar assets in the United States. AES and AIMCo, one of Canada’s largest investment managers, plan to purchase sPower from Fir Tree Partners and its minority owners. AES and AIMCo will each own slightly below 50 percent equity interests in sPower. After the deal closes, AES’ ownership of renewable energy projects in operation and under construction will grow from 8,278 megawatts to 9,552 megawatts, including hydro, wind, solar and energy storage. The deal is expected to close by the third quarter of 2017.It is subject to review or approval by the Federal Energy Regulatory Commission, the Committee on Foreign Investment in the United States and the expiration or termination of any waiting period under the Hart-Scott-Rodino Act.