Alternative energy sources are alternative to fossil fuels sources or energy. By definition alternative energy has low environmental impact and doesn’t harm the nature and this is not always true. The world is heavily dependent on fossil fuels, but they are finite resources that will eventually run out. Nowadays it is becoming more expensive to retrieve those remaining. In addition to that, fossil fuels cause air, water and soil pollution. That’s why we have to utilize alternative energy sources such as solar, wind, ocean and hydrogen. They are “clean”, produce no greenhouse gases and are considered unlimited.
The sun is the most powerful source of energy we know of. The sunlight can be used for generating electricity and water heating of both residential and industrial buildings. Solar energy is collected by various solar technologies, that can be either passive or active, depending on how they capture, convert and distribute the solar energy. Active solar technologies use photovoltaic panels and thermal collectors to get the energy from the Sun. In contrast, passive solar technologies use the solar energy indirectly by choosing proper building orientation, using materials with good light dispersing properties and thermal mass, using energy-efficient systems for air circulation, etc.
The amount of solar energy Earth receives each year is so vast that it can produce twice more energy that all non-renewable energy sources (coal, oil, natural gas, etc) combined. Earth received around 174 PW of solar radiation at the upper atmosphere and reflects 30% back in space. The rest 70% are absorbed by oceans, lands and clouds. This raises their temperature and triggers atmospheric circulation to complete the water cycle. Green plants are photosynthesizing and converting the solar energy into chemical energy producing food, wood and biomass from which fossil fuels derive.
Wind is the flow of gasses in the atmosphere – warm air rises up and cooler air is replacing it. Its energy has been used centuries ago and is still used today by windmills to convert grain to food and by sail ships to transport people and goods from one place to another. Today wind energy can by captured and transformed to electricity by wind turbines. Wind power is renewable, clean and produce no greenhouse gasses. In 2010 wind-generated electricity was more than 2.5% of world energy consumption. Nowadays Denmark in generating large portion of its energy from alternative energy sources and more than a quarter of it from wind power.
Wind farms use little land and can be build offshore when appropriate. Small wind farms can be used to provide electricity for distant and isolated locations. Large wind farms consists of few hundreds individual wind turbines connected to power transmission network. The land between the turbines can be used for agricultural or other purposes. Winds are consistent on year to year basis, but quite unpredictable in short periods – this is why the energy production won’t be consistent over time.
Hydro-power or water power is derived from falling water’s kinetic energy which rotates the propellers of turbine and generate electrical energy. Water is renewable and alternative energy source that is constantly “refilled” by the global cycle of water evaporation and precipitation. The water from oceans and lakes is evaporated by the Sun and form clouds. When cooled in the upper atmosphere, the water from clouds fall back to Earth as rain or snow and gets back into rivers and oceans. It is then captured by the turbines and generators housed at many dams on its way to the ocean and converted to electricity.
Biomass is material derived from living or recently living plants or plant-derived materials. It has been used as energy source since people started using wood to cook food and warm themselves in cold weather. It is still one of the alternative energy sources that can be used either directly to produce heat or indirectly after converting to any type of biofuel. Other sources of biomass energy include crops, grasses, plants, agricultural and forestry waste, organic and industrial waste. When biomass is converted to biofuel it can be used for transportation or manufacturing purposes which would otherwise require non-renewable fossil fuels.
Hydrogen is the most common element in nature and one of the alternative energy sources with huge potential. It is always found in combination with other elements so it takes energy to separate it. Once separated it can be used to power vehicles, for heating and cooking. There are different ways to separate it and some of the methods are not so environment-friendly. In addition to that hydrogen production requires more energy than can be retrieved from it later on. The right technology to fully utilize the hydrogen power is not developed yet.
The thermal energy generated and stored inside the Earth is called geothermal energy. It originated from the formation of the planet (20%) and radioactive decay of minerals (80%). The temperature difference between the core and the surface of the planet cause continuous flow of thermal energy from the core to the surface and back. Geothermal energy is one of the most underestimated and unexplored alternative energy sources. The heat generates steam and hot water on the surface which can be used for electricity production, home heating and industrial usage.
Marine energy (sometimes referred as ocean energy) is energy generated by waves, tides and temperature differences. It consists of several renewable energy sources driven by different forces and physical laws. There is wave power – from surface waves and tidal power – from large bodies of moving water, result of gravitational forces between the Earth and the Moon. The oceans have tremendous amounts of kinetic energy that can be used to generate electricity for home and industrial uses. Ocean energy is one of the those alternative energy sources with enormous potential for which we still don’t have the right cost-effective technology.