A wind turbine is made up of two major components and having looked at one of them, the rotor blade design in the previous tutorial, we can now look at the other, the Wind Turbine Generator or WTG’s which is the electrical machine used to generate the electricity. A low rpm electrical generator is used for converting the mechanical rotational power produced by the winds energy into usable electricity to supply our homes and is at the heart of any wind power system.
A study of the material consumption trends and requirements for wind energy in Europe found that bigger turbines have a higher consumption of precious metals but lower material input per kW generated. The current material consumption and stock was compared to input materials for various onshore system sizes. In all EU countries the estimates for 2020 exceeded and doubled the values consumed in 2009. These countries would need to expand their resources to be able to meet the estimated demand for 2020. For example, currently the EU has 3% of world supply of fluorspar and it requires 14% by 2020. Globally, the main exporting countries are South Africa, Mexico and China. This is similar with other critical and valuable materials required for energy systems such as magnesium, silver and indium. In addition, the levels of recycling of these materials is very low and focusing on that could alleviate issues with supply in the future. It is important to note that since most of these valuable materials are also used in other emerging technologies, like LEDs, PVs and LCDs, it is projected that demand for them will continue to increase.[53]
In October 2018, the American Council for an Energy-Efficient Economy (ACEEE) released its annual "State Energy Efficiency Scorecard." The scorecard concluded that states and electric utility companies are continuing to expand energy efficiency measures in order to meet clean energy goals. In 2017, the U.S. spent $6.6 billion in electricity efficiency programs. $1.3 billion was spent on natural gas efficiency. These programs resulted in 27.3 million megawatt hours (MWh) of electricity saved.[160]
“California Invests in ‘By Location’ Distributed Energy Resources” • California leads the US with several pilot projects to reward rooftop solar energy generators and other distributed energy resources in specific locations as an alternative to having utilities meet needs by investing in upgrading their electricity generation networks. [CleanTechnica]
Renewable energy, after its generation, needs to be stored in a medium for use with autonomous devices as well as vehicles. Also, to provide household electricity in remote areas (that is areas which are not connected to the mains electricity grid), energy storage is required for use with renewable energy. Energy generation and consumption systems used in the latter case are usually stand-alone power systems.

Since the 1970s, Brazil has had an ethanol fuel program which has allowed the country to become the world's second largest producer of ethanol (after the United States) and the world's largest exporter.[125] Brazil's ethanol fuel program uses modern equipment and cheap sugarcane as feedstock, and the residual cane-waste (bagasse) is used to produce heat and power.[126] There are no longer light vehicles in Brazil running on pure gasoline. By the end of 2008 there were 35,000 filling stations throughout Brazil with at least one ethanol pump.[127] Unfortunately, Operation Car Wash has seriously eroded public trust in oil companies and has implicated several high ranking Brazilian officials.
List of onshore wind farms List of onshore wind farms in the United Kingdom List of offshore wind farms in the United Kingdom List of offshore wind farms in the United States Lists of offshore wind farms by country Lists of offshore wind farms by water area Lists of wind farms by country List of wind farms in Australia List of wind farms in Canada List of wind farms in Iran List of wind farms in New Zealand List of wind farms in Romania List of wind farms in Sweden List of wind farms in the United States List of wind turbine manufacturers
So does it make a difference what type of electrical generator we can use to produce wind power. The simple answer is both Yes and No, as it all depends upon the type of system and application you want. The low voltage DC output from a generator or older style dynamo can be used to charge batteries while the higher AC sinusoidal output from an alternator can be connected directly to the local grid.

A solar cell, or photovoltaic cell (PV), is a device that converts light into electric current using the photovoltaic effect. The first solar cell was constructed by Charles Fritts in the 1880s.[5] The German industrialist Ernst Werner von Siemens was among those who recognized the importance of this discovery.[6] In 1931, the German engineer Bruno Lange developed a photo cell using silver selenide in place of copper oxide,[7] although the prototype selenium cells converted less than 1% of incident light into electricity. Following the work of Russell Ohl in the 1940s, researchers Gerald Pearson, Calvin Fuller and Daryl Chapin created the silicon solar cell in 1954.[8] These early solar cells cost 286 USD/watt and reached efficiencies of 4.5–6%.[9]