Type of Renewable Energy have been increasing with development in Technology and the imperative of using Alternative Energy as Fossil Fuels deplete and increase in costs. Besides Global Warming has made the benefits of Renewable Energy seem more attractive with each passing year. Note though there are many niches Renewable Energy types, the Three Major Forms of Renewable Energy are Solar Energy,Wind Energy and Biomass Energy (Biofuels).

Nuclear and Hydro Energy are not considered  as Renewable Energy according to the strict definition of Renewable Energy. However Hydro and Nuclear Energy both are responsible for more than 15% of global electricity production each. The clean energy industry saw a 30% increase in investments to $243 billion in 2010 which was another record year for Renewable Energy Capacity addition. Around 18 GW of Solar Energy and 38 GW of Wind Energy were installed with Solar Energy Capacity increasing by a whopping 150% from 2009. Wind power continued to lead at $95 billion. The solar sector is experiencing significant growth, with investments growing at 53% to $79 billion (source Pew).

Each Type of Renewable Energy has Advantages and Disadvantages which are specific to that type of Alternative Energy. For example Solar and Wind are intermittent in nature while Geothermal Energy has no such problems however Geothermal Energy suffers from a lack of good sites and takes a long time to get installed.

Main Types of Renewable Energy

Solar Energy

Solar Power has been the fastest growing energy source in the last decade showing a compounded annual growth of over 50%. In 2010 alone, solar energy demand grew by almost 150% beating the most optimistic forecasts as costs kept on declining for this renewable energy source. While Solar Power continues to be one of the most expensive forms of energy, it is also the energy source where the costs are declining rapidly. With solar costs going down by another 10% each year over the next few years, expect Solar Energy to grow at a further fast rate in the future as well after growing at 50% CAGR over the last decade.

Wind Energy

Wind Power has become the biggest source of renewable energy in the world after Nuclear and Hydro Energy (if you consider Nuclear/Hydro to be renewable energy that is). The reason for the huge increase in wind energy has been the sharply falling costs which have roughly become equivalent to Gas fired Energy. While Solar Energy costs are still falling, they are still way above the costs of fossil fuel energy. Wind Energy unlike other forms of fossil fuel energy should have much  less opposition however it is not so. Unlike Coal, Gas and Oil Energy it does not lead to increase in Greenhouse Gas Emissions and contribute to pollution. It does not lead to deaths of hundreds of miners each year nor has the danger of a catastrophic nuclear meltdown leading to death and disability of thousands. It also does not have the drawback of  massive ocean pollution leading to an ecological disaster.

Biomass Energy

Biomass Energy is the oldest source of Energy known to mankind and till the 19th century was the primary energy source. Even now Biomass Energy is used of Heating and Cooking by a large percentage of the Human Population. Biomass Energy with improving technology is being now used to construct large biomass power plants. Growing Concerns over Climate Change and soaring Coal Prices are making some Power Plants convert from Coal to Biomass as a Fuel Source. Biomass Energy has many advantages such as being Carbon Neutral, using Animal and Crop Wastes in a useful manner, being poor friendly etc. However Biomass Energy like other Renewable Energy forms of Geothermal Energy faces problems of resources.

Quasi Renewable Energy Forms

Hydro Energy

Hydroelectricity is one of the largest sources of energy accounting for roughly 20% of the worldwide demand of electricity with around 800 GW of capacity installed. There is considerable potential still left and developing countries like India and China can be expected to install another 500 GW over the coming years. Hydroelectricity is very important as it does not lead to GHG emissions and contribute to global warming. It also does not have the drawbacks like other renewable energy forms of high costs and intermittency. The advantages of hydroelectricity are substantial enough to far outweigh any disadvantages. But like nuclear energy, hydro power has some tail risks which can lead to catastrophic damage.

Nuclear Energy

Nuclear Power has come under assault in the aftermath of the Fukushima Nuclear Accident with Nuclear becoming a four letter word. However Nuclear Energy cannot be ignored because its benefits are unique in some applications and cannot be substituted by any other means. Nuclear Power also cannot be replaced in the short term from its most widely used application of generating Electricity. Note Nuclear Power accounts for almost 15% of the Global Electricity and in some countries is the major source of energy. For example France which has 80% of its power coming from Nuclear Fission, its impossible to think of shutting down nuclear plants like Germany which gets around 20%. Nuclear Energy has almost infinite potential but if you apply a strict definition, it is not exactly renewable in the sense that uranium fuel once used cannot be renewed to be usable again.

Minor Renewable Energy Forms

Geothermal Energy

Geothermal Energy is regarded as a poor cousin to its more glamorous cousins Wind and Solar. Geothermal Energy Capacity has been installed and the growth rate is a pathetic 3-4% compared to the over 50% CAGR seen for solar energy and around 30% for Wind Energy. However Geothermal Energy possesses one attribute that the others do not. Its 24 hour generation capability is a massive plus compared to the intermittent nature of Wind and Solar Energy. However long project development time and large capital investments have deterred fast growth in geothermal energy in the world. However some countries like Iceland, Indonesia, Philippines and USA have a strong geothermal energy industry.

Tidal Energy

Tidal Energy is a niche form of Renewable Energy with less than 500 MW of Electricity Capacity worldwide. Tidal Energy generates less than .001% of the worldwide electricity generation as the Technology of this Alternative Energy is still quite immature. However numerous companies are researching ways to develop Tidal Energy as it offers almost unlimited potential at low costs and with no pollution. Tidal Wave Energy has not seen much commercial success except the almost 45 year old Tidal Wave Power Plant in France.

Wave Energy

Like Tidal Energy, Wave Energy is another niche Clean Energy Source. Waves are caused by the wind blowing over the surface of the ocean. In many areas of the world, the wind blows with enough consistency and force to provide continuous waves. There is tremendous energy in the ocean waves. Wave power devices extract energy directly from the surface motion of ocean waves or from pressure fluctuations below the surface. Wave power varies considerably in different parts of the world, and wave energy can’t be harnessed effectively everywhere. Wave-power rich areas of the world include the western coasts of Scotland, northern Canada, southern Africa, Australia, and the northwestern coasts of the United States.

Summary

Besides the above mentioned Renewable Energy sources there are other clean energy forms like Fuel Cells which are not exactly Renewable Energy but come under the Clean Energy Category. Waste Energy or Energy from Methane comes under the broad heading of Biomass Energy which also encompasses Biofuel from Celluloid and non-Celluloid Sources.