pollution has a negative impact on the environment / air quality / water quality / society & solar energy rarely causes pollution ->  solar energy rarely has a negative impact on the environment  solar energy rarely has a negative impact on the environment & harming something has a negative impact on / effect on that something ->  solar energy rarely harms the environment  solar energy rarely harms the environment & if something happens rarely then that something likely happens the least ->  solar energy likely harms the environment the least  solar energy likely harms the environment the least & solar energy is a source of electricity ->  solar energy is a source of electricity that likely harms the environment the least  solar energy is a source of electricity that likely harms the environment the least & solar power means solar energy -> solar power is a source of electricity that likely harms the environment the least