Which Renewable Energy Resources Are Bringing The World Closer To Net-Zero?

The energy landscape is changing as the world moves towards net-zero. Renewable Energy has a crucial role to play in this transition as technologies become more advanced, cheaper, and more reliable. For example, according to the Energy Saving Trust,

‘In 2010, just 7% of electricity in the UK came from renewable sources. A decade later, the figure was 42%, as renewable electricity in 2020 overtook electricity generated from gas and coal plants for the first time.’

But which are the world’s top renewable energy resources bringing us ever closer to carbon neutrality?

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Biomass – A versatile source of energy

Biomass is renewable organic matter that comes from plants or animals. Within the energy sector, it refers to any organic matter that is used to generate energy. Traditional biomass was the main source of energy worldwide until the early 20th century, when coal, and then oil and gas, took over.

However, consumption of traditional biomass energy has remained relatively stable over the past two centuries, and today, of all the sources of renewable energy, bioenergy (energy generated from biomass) is the most used worldwide. According to the IEA (International Energy Association),

‘Its contribution to final energy demand across all sectors is five times higher than wind and solar PV combined.’

Whilst some use the terms biofuel and biomass interchangeably, biomass is generally referred to as the biological material used to produce the fuel, whilst biofuel generally refers to a gaseous or liquid fuel most often used for transportation.

Biomass can encompass matter such as:

• Wood and wood processing wastes

• Waste materials and agricultural crops

• Biogenic materials found in municipal solid waste

• Animal manure and human sewage

One of the main benefits of biomass is its versatility. In addition, its carbon footprint is far lower than traditional carbon-intensive sources of energy. It can be converted into liquid fuels that can replace traditional fossil-based fuels but can also be used to produce heat, electricity, and bioproducts.

Hydropower – The most reliable renewable energy

Hydropower is one of the oldest sources of energy. Farmers in Ancient Greece were already using the power of flowing water to spin wheels and grind their grain. Fast-forward to the present day, hydropower has become one of the most reliable, low-cost, and efficient sources of responsible waste management and clean electricity.

Hydroelectricity also presents the benefit of having the highest electricity yield of all the renewable energy sources. Modern hydro-turbines can convert up to 90 per cent of the available energy into electricity. Not only that, but hydropower also provides solutions when it comes to flood control, clean drinking water, and irrigation support.

Hydropower technology generates energy by using the elevation difference, created by a diversion structure or a dam, of water flowing in on one side and out, much lower, on the other.

There are many benefits to hydropower. Firstly, it only relies on the energy of moving water. Furthermore, it has relatively low costs throughout a full project lifetime, with low operation, maintenance, and fuelling costs. The lifespan of hydropower projects is also longer than most other renewable energy types, meaning upfront project costs are spread out over a longer period. And very importantly, hydropower facilities can provide electricity to the grid instantaneously, making it a reliable and flexible backup source of energy during disruptions and major electricity outages.

Wind – 743GW of capacity bringing the world closer to net-zero

The wind’s kinetic energy is used to generate electricity. Wind power, or wind energy, is created using a wind turbine, a machine that channels the wind’s power to produce electricity.

The way a turbine works is that wind will blow on the turbine’s blades, which are attached to a rotor, which spins to create electricity.

There are two types of wind turbines:

• vertical-axis wind turbines (VAWTs)

• horizontal-axis wind turbines (HAWTs)

HAWTs are the most common, and generally have 2 or 3 blades positioned to face directly into the wind. VAWTs have shorter, wider curved blades.

Wind turbines can come in a whole range of sizes, from smaller 100 kilowatts turbines that can power a single home to 16 GW turbines that can power thousands of homes and that measure hundreds of meters tall.

The electricity generated by the turbines will either be used directly, connected to an electrical grid, or stored for future use.

Currently, there is 743 GW of wind energy capacity worldwide, from a combination of offshore and onshore wind farms and turbines.

The largest wind farm in the world is the Gansu Wind Farm in China, with a planned capacity of 20GW. Once completed, the farm will consist of 7,000 turbines and will generate enough electricity to power a small country.

Solar – An abundant source of renewable energy

Solar Energy refers to the radiation from the sun which produces heat, causes chemical reactions, or generates electricity.

The sunlight that reaches us consists of about 50% visible sunlight, 45% infrared radiation, and the rest amounts to ultraviolet and other forms of electromagnetic radiation.

According to the Encyclopædia Britannica,

‘The potential for solar energy is enormous, since about 200,000 times the world’s total daily electric-generating capacity is received by Earth every day in the form of solar energy.’

And as stated by the US Office of Energy Efficiency and Renewable Energy,

‘The amount of sunlight that strikes the earth's surface in an hour and a half is enough to handle the entire world's energy consumption for a full year.’

However, even though solar energy has become a lot more affordable in recent years, collection, conversion, and storage costs are still relatively high, limiting how extensively it can be used.

The radiation emitted from the sun can be converted either into thermal energy or electrical energy.

The most common devices to produce thermal energy are flat-plate collectors (generally a blackened sheet of metal covered by a sheet of glass that is heated by the sun), used for solar heating purposes. The heat collected is then transferred to water or air found behind the plate and can be used directly or stored. Most often, this technology will be used for house or water heating.

Solar energy can also be turned into electricity when light hits a panel, where it reacts with the silicon crystals in the panel, producing an electric current. This electricity is then fed into a grid or used directly. Electricity can also be produced using mirrors that concentrate solar radiation into a single spot. This is called Concentrated Solar Power (CSP).

Currently, the top producers of solar energy are China (254GW), the US (76GW), and Japan (67GW).

Geothermal – Energy coming from deep down under our feet

Geothermal energy was first used in Italy in 1904 and its use has been steadily increasing since then. According to IRENA, the International Renewable Energy Agency, global geothermal energy grew from 10 GW in 2010 to 13.3 GW in 2018.

Geothermal energy is the eat that comes from the subsurface of the earth, most often contained within fluids or rocks beneath the earth’s crust and can go as far down to the earth’s magma (molten or semi-molten natural material from which all igneous rocks are formed).

To produce power from geothermal energy, a well is dug deep down into the ground – about a mile deep – to reach underground reservoirs which contain hot water or steam, which can then be used to drive turbines connected to electricity generators.

There are three types of geothermal energy facilities:

• Dry steam: This is the oldest type, which uses steam from underground to directly drive a turbine.

• Flash: Flash plants pull high-pressure hot water from underground and mix it with cooler low-pressure water. This creates steam that is used to drive a turbine.

• Binary: Binary plants use hot water passed through a secondary fluid that has a lower boiling point than water. The secondary fluid is turned into vapour which drives a turbine.

Currently, geothermal energy is used in about 20 different countries, and the United States is its biggest producer. The country also has the largest geothermal field in the world, named “The Geysers” in California, which spans 117 square kilometres and feeds 22 power plants, totalling 1.5 GW in capacity.

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