Clean Energy and Sustainability Accelerator Act This bill establishes and capitalizes a Clean Energy and Sustainability Accelerator. The independent, nonprofit accelerator must invest in clean energy technologies and infrastructure to reduce greenhouse gas emissions. The accelerator must make capital available to state, territorial, or local green banks. The banks must be public or nonprofit specialized finance entities that use finance tools to mitigate climate change. The accelerator may also provide technical assistance and funding to states and other political subdivisions that do not have green banks to establish such banks. When investing in projects that mitigate greenhouse gas emissions, the accelerator must prioritize investments that serve climate-impacted communities (e.g., communities of color or low-income communities). In addition, the accelerator must explore the establishment of a program to provide low-interest and zero-interest loans, up to 30 years in length, to any school, metropolitan planning organization, or nonprofit organization seeking financing for the acquisition of zero-emissions vehicle fleets or associated infrastructure. Finally, the accelerator must explore the establishment of an accelerated clean energy transition program to (1) expedite the transition within the power sector to zero-emissions power generation facilities or assets, and (2) invest in local economic development in communities affected by this transition away from carbon-intensive facilities or assets.