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Sustainable Energy: Top 10 Alternative Sources


Posted on June 20 2018


What is sustainable energy?

Sustainable energy is a form of clean and renewable energy that can be harnessed to meet our present's needs without compromising the future generations’ ability to face their needs. Simply put, sustainable energy is energy that will never expire or deplete in time, aka, inexhaustible. The list below will briefly describe each one of the 10 most used sustainable energy. From SUAOKI we hope that this article will help you have a clearer and better understanding of sustainable energy.

Solar Energy

There are 2 main types of solar energy; namely, passive and active. Passive solar energy; buildings are designed to collect, store, and distribute the heat energy generated from sunlight. On the other hand, active solar energy makes use of electrical technology and mechanical technology to capture, convert and store energy for present or future use, for example, solar panels.

In order to harness solar energy, solar panels are a necessity. They are easy to install, durable and require little or no maintenance. It is the most widespread and popular renewable energy due to its adaptability and its unlimited solar energy supply, produced by the sun. Nevertheless, it is ineffective in colder regions with little to no sunlight.

Wind Energy

[caption id="attachment_309" align="aligncenter" width="641"]Sustainable Energy - windmills by China Leading Global Wind Energy Market[/caption]

Wind power is the conversion of wind energy, via windmills, into mechanical power or electricity. It is a 100 % renewable and sustainable energy; does not cause any type of pollution. Windmills are generally installed in areas which experience high winds. In order to be effective Wind farms (a large number of windmills installed in clusters) are situated in high elevation or over open water.

Wind turbines convert the kinetic energy, produced by the effect of air currents, into mechanical power. The wind drives propeller blades through a mechanical system which rotates the rotor of a generator that produces electricity.

Despite the fact that wind produces roughly 1.5% of electricity consumed worldwide, in some countries, it is growing rapidly. In the United States, for example, wind energy installations power about 20 million households per year, and this number keeps growing. However, this form of sustainable energy also presents some challenges. Wind turbines can cause visual pollution and may be dangerous to some forms of wildlife.


[caption id="attachment_314" align="aligncenter" width="666"]Sustainable Energy - hydro power dam by GE[/caption]

Hydro-power generates electricity using the power of moving water. It is the most widely used form of renewable and sustainable energy. Dams use radial gates (also called tainter gates) to control the water flow. The water flows through an intake and the gravitational force drives the blades in a turbine, situated at the bottom of the dam, causing them to turn. The turbine then rotates the generator to produce electricity.

In small areas where other power sources are not viable, small-scale hydro or micro-hydro power is an appropriate sustainable energy source alternative. Since small-scale power systems make no use of a dam or major water diversion, it can be easily installed in small rivers or streams with little-to-none environmental footprint.

Tidal Energy

Tidal energy or tidal power is another form of hydropower. It exploits enormous amount of energy within the ocean tides, produced by gravitational forces of the sun and moon, to generate electricity. A tidal barrage helps to harness the tidal energy.

As compared to wind energy and solar power, tidal energy is more predictable. Tidal stream generators use the kinetic energy of the ocean to power turbines. Although it is a fairly new technology, tidal power has enormous potential for future electricity generation.

However, like the other forms of sustainable energy, tidal energy also has its flaws; it is dependent on the strength of tides, requires a suitable site, danger to fish and other sea-life, etc.

Ocean Thermal Energy Conversion

Ocean Thermal Energy Conversion (OTEC) technology takes advantage of the difference in the temperature between the ocean surface waters and the deeper ocean waters to operate a turbine and produce electricity. Oceans cover two-thirds of the earth's surface and contain 97% of its water, which make OTEC a highly sustainable energy source.

OTEC uses the ocean's warm surface temperature of around 25°C (77°F) to vaporize a working fluid (Ammonia). The vaporized fluid expands and drives a turbine connected to a generator to produce electricity. The seawater, with a temperature of around 5°C (41°F), pumps from deeper ocean layers, then cools down the vapor. This process condenses the vaporized fluid back into a liquid form.

OTEC needs a big temperature difference to be more efficient. This technology is viable mainly in tropical areas where the year-round temperature differential is at least 20°C (36°F).

Geothermal Energy

Geothermal energy is the extraction of heat from the earth. Commonly used in ancient Rome for space heating and bathing, nowadays we use geothermal energy to produce electricity. On a small scale, we use the geothermal heat pump to provide heat for a household, whereas on a very large scale energy is produced via a geothermal power plant.

Geothermal energy is present anywhere on Earth and is an abundant sustainable energy source, as the Earth will never stop producing heat. A thermal mass flow meter is generally used to tap the energy and generate electricity. Areas with high underground temperatures are the most suitable to tap.

This power source has huge potential and is increasingly growing in popularity (+5% growth in 2015). However, it also has downsides: while releasing the heat the Earth may also release harmful gases.


[caption id="attachment_312" align="aligncenter" width="700"]Sustainable Energy - biomass energy by BigGreenSwitch[/caption]

Biomass is the conversion of biological materials and wastes into energy sources for heating, power generation, and transportation. It constitutes carbon, hydrogen, and oxygen. There are 4 types of biomass, namely solid waste, wood & agricultural biomass, landfill gas and last but not least, alcohol fuels. There are 4 different ways to convert those into energy, namely, burning, bacterial decay, fermentation, and conversion.

The main difference between biomass and fossil fuels is the time difference it needs to replenish for each source. During growth, biomass takes carbon dioxide from the atmosphere and returns it back during combustion. The ideal way to manage it as a viable and sustainable energy source is to replant new growth, which will take up CO2 from the atmosphere released by combustion of the previous harvest.

Biomass can be the ideal replacement for coal which will considerably reduce net carbon dioxide emissions. On the other hand, the use of wood may result in deforestation and its drawbacks can lead to groundwater contamination and irreversible erosion patterns.


Biogas is a sustainable energy source that belongs to the category of bio-fuel. It comprises methane, carbon dioxide, hydrogen and hydrogen sulfite. Anaerobic degradation of organic wastes naturally produces biogas. It takes a problematic gas (methane) and converts it into a much safer form (carbon dioxide). This decomposition takes place in an anaerobic environment (an environment absent of oxygen) and produces biogas as its outcome.

Biogas can be used as fuel for heating purposes such as cooking, or can be compressed, like natural gas, and used to power vehicles.

Nowadays, the biogas technology is becoming popular in both small (farm, household) and large (industrial) scale production. Being a clean and sustainable energy source, biogas is applicable to developing as well as developed countries.


[caption id="attachment_315" align="aligncenter" width="739"]Sustainable Energy - Bio fuel farm by NREL[/caption]

Biofuel is the conversion of renewable biomass material directly into liquid fuels to help meet the ever-growing transportation and fuel needs. The 2 widely used types of biofuels are ethanol and biodiesel.

Ethanol can also be produced through gasification systems, whereby high temperatures and low-oxygen environments are used to convert biomass into synthesis gas. Biodiesel, however, results from merging alcohol (methanol) with animal fat, vegetable oil, or recycled cooking grease.

According to the United States Department of Agriculture, there is an increase in the adoption of biofuels and in 2012 they accounted for around 7% of transport fuel consumption. However, extraction requires dedicated machinery, which can contribute to indirect emissions, since biofuels themselves don't.


Hydrogen is one of the most abundant elements on earth. Water, coal, and petroleum in compound form integrate natural hydrogen. Similar to electricity, hydrogen is also a clean energy carrier. It is a clean fuel source and it does not leave any waste behind (besides water). Hydrogen is the lightest element and at normal temperature and pressure, it exists in gas form.

Although it is a clean and sustainable energy source, hydrogen remains expensive, mainly because its extraction is quite costly due to the fact that it takes a lot of energy to separate hydrogen from other elements. Moreover, it is not easy to store and move it around in its gas form because it is highly flammable.


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