It isn’t clear where current energy trends are going. Perhaps they may stabilize or as more and more people suggest the days of the carbon fuel fuel economy are quickly being done away with. Without CO2 based propulsion, researchers, businessmen, and engineers are on the look out for the next universal fuel. This fuel will be the first fuel in the age of the “clean fuel. ” Clean fuel refers to a non CO2 based fuel, which is renewable. The problem so far is that a universal fuel has yet to be found. Here are some of the possibilities: 1. Solar 2. Wind 3. Electric 4. Air 5. Hydrogen Solar Cars have long been the source of hope for green energy enthusiasts, mainly because the fuel is. . . free. The problem is that an efficient prototype available for mass markets has yet to be fully developed. There are some universities and other engineers working on workable solar car prototypes, but these prototypes have been relegated to the sphere of university projects despite the advances. Wind energy may not seem to be a good propulsion system for a car, but it is however a great source of primary energy to infuse the electric grid with. Wind Energy is a solid clean energy instead of carbon derived fuel, which is juicing up the grid now. This will truly move us into a purely clean fuel society. Electric Cars are not only a reality, but they are beginning to take the world by storm. Starting with Tesla and now others are beginning to jump on the band wagon. The sticking points in preventing mass consumption of electric cars have been a proper infrastructure to support the integration of electric stations and other support. This has begun to change recently as more and more smaller countries have begun to lay the foundations for turning over their carbon infrastructure to an electric one. Air Cars are another burgeoning possibility that has become very real in the last few years. They essentially work off of compressed air. The is released slowly, whose energy puts pressure on the pistons to propel the car. Air Cars are almost ready for the consumer market and when they are, they are assured of success. Hydrogen Fuel-Cell Cars have been around for a while, yet their technology has gotten to the point where they’re actually ready for the consumer market. Fuel-Cells are essentially a combination between an engine and a battery. Hydrogen is converted into energy using ions in the fuel cell. The energy is then used to power the vehicle. As with other clean fuels, hydrogen has a way to go since it lacks an infrastructure for refueling. Despite this, countries have been pushing forward with incentives and plans to build hydrogen stations. California has already done this as well as other areas of the world. Its not clear yet which clean fuel will be accepted as universal. Perhaps there won’t be a clear universal clean fuel, but rather a serious of choices built around regional and geographical situations.