Wind energy is one of the renewable sources of energy, extremely popular and useful in the modern industry. Energy is acquired with a help of special wind turbines. Turbines convert mechanical energy into electricity. Wind energy is also used in tall ships.

The wind energy is primarily associated with windmills. It is known since the days of Hammurabi, when it was used for water pumping and drainage fields. Initially, the rotation axis was vertical, horizontal setting was introduced in 1105 years, and is still used.

Most wind energy is produced by Germans, as much as 40% of world production.

Wind turbines have both opponents and supporters. Some, criticize the construction of such facilities in the vicinity of the houses due to high intensity of noise, which is caused by the turbine. The aesthetic considerations and the threat to birds is also a decisive factor. Cluster of wind turbines may also contribute to changes in local climate. However, a great advantage of wind power is the reduction of emissions of harmful carbon dioxide into the atmosphere. The turbines generate electricity without combustion of any fuel. Greenpeace reports predict that by 2020 wind turbines will produce over 10% of the total electricity.

Cost-effectiveness of wind power plant construction is associated with the terrain and the location of the construction in the area. Windless areas categorically disqualify start of such an investment.

Increasingly popular building a backyard wind turbine is becoming. Turbines are  commonly installed on the roof of the house. This gives an additional power source. The cost of building such a plant ranges from 15 thousand. However, its cost-effectiveness requires the right conditions, a constant wind with a force of at least 5 m/s. House should also be very well insulated.

Solar energy is an extremely important source of renewable energy. Solar energy is a rapidly growing sector of the industry, because of the cost-effectiveness and protection of the natural environment.

The acquisition of solar energy is enabled by photovoltaic cells (also called photo elements, solars, or solar cells). This device converts obtained solar energy to electricity. This is a result of the use of semiconductor pn-type connectors, and the flow of electrons leads to an electrical voltage. The effect of photovoltaic was noticed by A.C. Becquerel in 1839. Energy generation using photovoltaic cells, is associated with higher costs than in the case of nuclear energy. However, this solution is used to provide electricity either in areas isolated from other sources, or in homes situated in unfavorable terrain. Solar cells also allow us to produce a small voltage in portable devices with low power, such as calculators, clocks and lamps. They also work well in space, where there is no shortage of solar energy and other sources would require specific fuels.

It happens, that photovoltaic cells are used to power telephones, cameras, traffic monitoring and measuring devices. This is possible because of the small amount of time required to power these devices. In the case of price reductions of photo cells, there would be a possibility of using them in larger devices, without having a drastic increase in prices on the items or equipment.

Most commonly, solar energy is used to generate electricity by using special rechargeable batteries. Processing of solar is allowed thanks to water and air collectors, they produce heat that can be used to heat homes and other facilities, heat water  and dry agricultural products.

Extremely futuristic way of generating energy extracted from solar radiation, can be based on the power mirrors. In the first version, it uses the so-called Stirling engine. The heat gathered from the system of mirrors, with the help of engine, drives the electric generator, thus creating a solar power plant with an average power of 25 kW. Another option provides an extensive system of movable mirrors in the center of which there would be a heating tower. Obtaining heat at a temperature of up to 3000 Celsius degrees and directing sunlight to a specific point on the tower (the stove, filled with liquid sodium), would provide the power of the order of 11 MW.

Years ago, before there were electrical machinery and electricity became common in every home and farm, primarily hydropower was used. Especially to drive mills, forges, saw mills and other industrial plants, where this kind of energy, worked out very well.

Another advantage of hydropower is its price. It’s much cheaper than fossil fuels and nuclear energy. For this reason, industrial plants which use hydropower, attract businesses due to lower electricity costs. Increasingly, also the need for taking care about the environment decides.

Hydropower is not a major source of electricity as water resources, necessary to produce it, are very limited. In addition, most water sources are located in remote locations. Low cost of energy, however, involves the construction of the high cost hydroelectric power plant. This type of investment also requires a long waiting time for a profit. Despite this, more and more of hydropower plants are being built, especially in the areas with large water tanks.

There are several types of power plants, one of them are plants with natural water supply. Another is regulatory power plants, a reservoir, with a special reservoir, in which periodic changes in the amount of flowing water are balanced. There are also flow (non-reservoir) power plants built, in this case the amount of energy produced, is depending on the amount of water flowing in the river at a given time. The last type are pumped - storage. They are built between two water reservoirs - the upper and lower level. This arrangement allows the accumulation of energy when it is not really needed (if there is water in the upper reservoir), and its elimination at the time of high demand (draining of the tank top to bottom using water turbines.) Another division of power plants depends on their power. Large power plants are those, with the minimum capacity of 10 MW. Small plants produce energy of 200 to 10 kW. There are also micro electric plants, with a capacity below 200 kW.

The largest hydropower plant in the world is on the border between Brazil and Paraguay, exactly the Itaipu dam on the Parana. It was built in 1983.