AC manufacturer Greencore has come up with a long-awaited solution to the inherent problem in solar-powered air conditioning units-solar panels are still not efficient enough to power the energy-gobbling machines on their own. The company's 10200 model uses a single 170-watt solar panel during the day and electricity from the power grid during the night to charge its batteries, leading to massive energy savings even if the solution isn't 100% solar. Greencore has three versions of its AC system, a fixed one, a portable one with two batteries and another portable with four batteries. All three run on 24 volts DC and have a cooling capacity of 10,200 BTUs and a heating capacity of 13,400 BTUs. According to the company, McDonalds and the US Navy are already on board with testing the units. [Treehugger]