Newsday: Hefty new federal tax credits and ambitions for cheaper, cleaner energy have lured record numbers of Long Islanders to install solar energy systems this year, raising concerns about LIPA’s ability to keep up. Applications for the Long Island Power Authority’s generous rebates in the first quarter were triple last year’s levels, and LIPA has already committed around half of its $12.5-million 2009 solar rebate budget. Solar proponents and contractors worry that LIPA will reduce …