Energy technology

• Photovoltaic power draws electricity from solar radiation through solar cells, either locally or in large photovoltaic power plants and uses semiconductor technology.
• Solar heating uses solar panels which gather heat from sunlight to heat buildings and water.
• Solar thermal power produces electricity by converting solar heat.

Wind turbines on Inner Mongolian grassland

Wind turbines convert wind energy into electricity by connecting a spinning rotor to a generator. Wind turbines draw energy from atmospheric currents and are designed using aerodynamics along with knowledge taken from mechanical and electrical engineering. The wind passes across the aerodynamic rotor blades, creating an area of higher pressure and an area of lower pressure on either side of the blade. The forces of lift and drag are formed due to the difference in air pressure. The lift force is stronger than the drag force; therefore the rotor, which is connected to a generator, spins. The energy is then created due to the change from the aerodynamic force to the rotation of the generator. [1]

Being recognized as one of the most efficient renewable energy sources, wind power is becoming more and more relevant and used in the world.[2] Wind power does not use any water in the production of energy making it a good source of energy for areas without much water. Wind energy could also be produced even if the climate changes in line with current predictions, as it relies solely on wind. [3]

Deep within the  Earth, is an extreme heat producing layer of molten rock called magma.[4] The very high temperatures from the magma heats nearby groundwater. There are various technologies that have been developed in order to benefit from such heat, such as using different types of power plants (dry, flash or binary), heat pumps, or wells.[5] These processes of harnessing the heat incorporate an infrastructure which has in one form or another a turbine which is spun by either the hot water or the steam produced by it.[6] The spinning turbine, being connected to a generator, produces energy. A more recent innovation involves the use of shallow closed-loop systems that pump heat to and from structures by taking advantage of the constant temperature of soil around 10 feet deep.[7]

Building of Pelton water turbines in Germany.

Hydropower draws mechanical energy from rivers, ocean waves and tides. Civil engineering is used to study and build dams, tunnels, waterways and manage coastal resources through hydrology and geology. A low speed water turbine spun by flowing water can power an electrical generator to produce electricity.

Bioenergy deals with the gathering, processing and use of biomasses grown in biological manufacturing, agriculture and forestry from which power plants can draw burning fuel. Ethanol, methanol (both controversial) or hydrogen for fuel cells can be had from these technologies and used to generate electricity.

Heat pumps and Thermal energy storage are classes of technologies that can enable the utilization of renewable energy sources that would otherwise be inaccessible due to a temperature that is too low for utilization or a time lag between when the energy is available and when it is needed. While enhancing the temperature of available renewable thermal energy, heat pumps have the additional property of leveraging electrical power (or in some cases mechanical or thermal power) by using it to extract additional energy from a low quality source (such as seawater, lake water, the ground, the air, or waste heat from a process).

Thermal storage technologies allow heat or cold to be stored for periods of time ranging from hours or overnight to interseasonal, and can involve storage of sensible energy (i.e. by changing the temperature of a medium) or latent energy (i.e. through phase changes of a medium, such between water and slush or ice). Short-term thermal storages can be used for peak-shaving in district heating or electrical distribution systems. Kinds of renewable or alternative energy sources that can be enabled include natural energy (e.g. collected via solar-thermal collectors, or dry cooling towers used to collect winter's cold), waste energy (e.g. from HVAC equipment, industrial processes or power plants), or surplus energy (e.g. as seasonally from hydropower projects or intermittently from wind farms). The Drake Landing Solar Community (Alberta, Canada) is illustrative. borehole thermal energy storage allows the community to get 97% of its year-round heat from solar collectors on the garage roofs, which most of the heat collected in summer.[8][9] Types of storages for sensible energy include insulated tanks, borehole clusters in substrates ranging from gravel to bedrock, deep aquifers, or shallow lined pits that are insulated on top. Some types of storage are capable of storing heat or cold between opposing seasons (particularly if very large), and some storage applications require inclusion of a heat pump. Latent heat is typically stored in ice tanks or what are called phase-change materials (PCMs).