By the 1960s solar power was the standard for powering space-bound satellites. In the early 1970s, solar cell technology became cheaper and more available ($20/watt). Between 1970 and 1990, solar power became more commercially operated. Railroad crossings, oil rigs, space stations, microwave towers, aircraft, etc. Now, houses and businesses all over the world use solar cells to power electrical devices with a wide variety of uses. Solar power is the dominant technology in the renewable energy field, primarily due to its high efficiency and cost-effectiveness. By the early 1990s, photovoltaic conversion had reached an unprecedented new height. Scientists used solar cells constructed of highly conductive photovoltaic materials such as gallium, indium, phosphide and gallium arsenide that increased total efficiency by over 30%. By the end of the century, scientists created a special type of solar cells that converted upwards of 36% of the sunlight it collected into usable energy. These developments built tremendous momentum for not only solar power, but for renewable energy technologies around the world.