The Seven Types of Renewable Energy

What is ‘renewable’ energy?

Renewable energy is a term that all of us will be well aware of by now. It has managed to find a spot in our vocabulary with many of us still having no idea what it actually is. Many could ramble through an explanation, maybe hitting a few buzzwords along the way – but there is no genuine understanding there.

We aim to change that.

What is the difference between renewable energy and… well, energy? Both traditional fuel sources and renewable energy finish at the same finish-line, they just run very different races.

The main difference is the original source of the energy. Traditionally there has been a reliance on finite fossil-fuel sources – burning things like coal to release and utilise the energy stored within. The problem with these fuel-types is that they are both incredibly dirty, and will run out eventually.  

Renewable energy comes from clean, naturally replenishing sources. It does not matter how much energy we harvest from the sun, as it will keep shining the following day for us to harvest all over again. Renewable energy implies that we will be able to continue exploiting the source indefinitely.

Solar Energy

Sunlight is fortunately one of the most abundant sources of renewable energy – and can be found and harnessed all across the globe. It is incredible to think that the total amount of energy that hits the surface of the earth in one hour is more than enough to satisfy our yearly energy demands.

Solar energy is certainly beginning to be a lot more commonplace too – just take a short drive to the local shops and no doubt you will be able to spot a few solar panels installed on some roofs.

Solar energy uses slices of crystalline silicon to produce solar cells that are then placed in direct sunlight. These panels then absorb photons from sunlight and convert them into electrons. This is a process called ‘the photovoltaic effect’. Source: Phys

In the past, solar-panels were only ever used by small or medium-sized installations to generate just a little energy. However, in the last thirty or so years, this has changed dramatically.

The biggest issue facing solar energy production – is how to deal with no sun. This is just common-sense, but the amount of solar energy that can be used is directly dependant on time of day, season, location, and weather. It is easy to

Wind Energy

It is worth noting that humans have been harnessing the power of the wind for thousands of years. Traditional wind-mills to drive grind-stones, large sail-boats to traverse oceans, or even using it to drive rudimentary water-pump systems.

Thousands of years of use across a whole host of different sources, and we are still no closer to running out as the day we started – how incredible.

These days, wind energy is harnessed through massive turbines planted upright into the earth. The huge blades of the turbine will begin to spin when hit by wind, which will then run a generator that will turn the kinetic (moving) energy into electrical energy that can then be used in homes across the country. It is a common misconception that winds will have to be fast-moving or strong in order to begin turning turbine blades.

It is true that the faster the wind blows, the more electricity will be generated. This only holds true to a certain level, however. When wind-speed doubles almost eight times as much electrical energy is produced. If the wind passes into the threshold of being too strong then turbines will shut down to protect against any unnecessary damage.

Not every site is suitable for installation of wind-turbines. It is difficult to find the right conditions that are needed to run wind-farms/turbines at their production capabilities. There are few countries in the world that are blessed with the consistent wind and suitable landscape needed to build large-scale wind farms.

Luckily for us in the UK, we are perfectly situated on the North-West tip of Europe to be exposed to just the right amount of wind. Scotland in particular is actually the windiest country in the whole of Europe, which has led it to be dubbed as the…

“…Saudi Arabia of wind power…”

– Boris Johnson, Prime Minister of the UK

Tidal Energy

Tidal energy is still in its infancy when compared to other sources of renewable energy.

Our oceans cover around 70% of the earth’s surface. If we were able to unlock the secrets to harnessing the energy that is currently left untapped there, then it is difficult to see us ever struggling for renewable energy ever again. Tides are steady and predictable – which sounds great, in theory.

The problem with tidal energy lies in the logistics. It is incredibly difficult to find a suitable location that contains enough wave power, as-well as fulfilling other financial and logistical check-boxes. Historically, cost has always won the trade-off with reward. In other words, investors think tidal energy projects are too expensive and the potential returns/reward simply does not justify original investment.

Recent technological developments and improvements in turbine design and technology have actually improved this. By increasing potential returns and lowering costs, tidal power projects are finally starting to receive the attention (and more importantly, funding) that they deserve.

In 2015 – the first ever grid-connected wave-power station went online off the coast of Western Australia. This project, dubbed CETO after the Greek goddess of the sea, was developed by Carnegie Wave Energy. The power station cleverly operates underneath the surface of the water by using undersea buoys to pump a series of pumps anchored onto the sea-floor, which in turn will generate electricity. It is still early days – but tidal energy is coming, a lot faster than many anticipated. Source: Phys

Geothermal Energy

Geothermal electricity relies on the heat that is naturally produced by and from the earth. This can be from sources like magma conduits, hot-springs, or even hydrothermal circulation. This heat is then either harnessed to produce steam and spin turbines and generate electricity, or directly used to heat buildings.

A huge problem with taking geothermal energy production further is that there is a severe lack of suitable sites to be found. How often do you encounter a natural hot-spring in your day-to-day life? Or, if there are multiple sites then they often lie in close proximity to another or in an area too remote or hostile to develop infrastructure. This means that only very few countries can even possibly produce geothermal electricity.

What it does offer, is an opportunity for countries with high-levels of geothermal activity to exploit an easily accessible and cheap fuel-source. This encourages the migration away from fossil-fuel energy sources wherever possible. When talking about ‘world-leaders’ in renewable electricity production, it is often the same handful of wealthy countries that will crop up. Geothermal electricity allows countries like El Salvador, Costa Rica, The Philippines, Kenya, and Iceland to enter the conversation. This is not just a random list, but rather a list of countries who currently source more than 15 percent of their energy demands from renewable geothermal sources.

Biomass Energy

Biomass can be considered to be any organic material from plants or animals – which can include crops, waste wood, or even animal by-products. Most commonly the biomass will be burned and energy released as heat, which can be harnessed to drive a steam turbine and generate electricity.

It may be surprising to some that burning biomass is considered to be renewable. Is it really sustainable to burn thousands of acres of forest in order to generate electricity? Biomass energy production is often labelled as clean, renewable, and a brilliant alternative to fossil fuels.

This isn’t universally true however, as many forms of biomass will actually produce higher carbon emissions than some fossil fuels. Not only this, but some sources are incredibly damaging to local flora and fauna.

When looking for great renewable sources of biomass – it is better to focus on any waste produce from industry. It is now common practice for large sawmills to gather sawdust and wood-chips and send them onwards to be burnt. Although there are still emissions released, these are mitigated somewhat by the fact that the chips would simply be left to rot otherwise.

Hydro-Electric Energy

Hydro electric electricity generation relies on fast-moving water as a source of renewable energy generation. Fast moving water is sourced in either large rivers, or rapidly-descending water from hills and mountains. This energy is used to spin turbine blades that will be transformed into electrical energy by a generator. It is almost comparable to a re-imagined wind energy turbine.

The jury is still out regarding the classification as a renewable energy source, but this is more a case of semantics rather than any ground-breaking scientific discovery. There have been well-documented cases of huge hydro-electric dams diverting and restricting natural flows of water – negatively impacting reliant human and animal populations. In any cases of dam failure, the results are catastrophic. The Mekong basin flood in Southern Laos as a result of a nearby hydro-electric dam failure, and should be used as a case-study of poor practice. Read about it here

The nature of this and other failures in hydro-electric power plants are mainly down to scale of operation, which is why it is deemed to be semantics. Huge dams are far more likely to permanently alter natural flows of rivers or rapids, which leads to them being deemed as ‘non-renewable’. Small hydro-electric plants that are carefully managed have been shown to not have the same adverse effects (any site with production less than 40 megawatts). Source: NRDC

Solar Energy – Heat

In order to avoid confusion, this renewable source has been left until last to deal with. We have already covered how solar energy can be transformed by the photovoltaic effect into usable electricity, much like how a plant would harness the sun’s energy. There is another method in which we can harness the sun’s power.

CSP plants (concentrating solar panels) concentrate the heat from sunlight, and use this thermal energy instead of the photovoltaic effect. This is done through complicated series of high-powered lenses and mirrors focussing sunlight onto a heat-carrying medium and turning it into steam to drive turbines. This technology is not quite as developed as other areas of solar renewable energy. Source: National Geographic

As you can imagine, CSP faces much of the same problems as other areas of renewable energy production. There is an incredible shortage of CSP experts, as so many solar energy specialists are headhunted into photovoltaics. Issues with funding arise commonly, as capital start-up costs and manpower costs are astronomical. Not only this, but there are very few suitable locations for CSP plants due to the need for intense year-round sunlight.

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