How many shapes and forms can you imagine water to have? Normally, it comes in liquid, solid, gaseous and aqueous diluted forms. How about gases or electricity? Those amazing-looking plasma balls, born from high-voltage electrodes and noble gases can be used in many ways. We can take a number of energy resources and give them many shapes and looks.
Even though we haven't really mastered the ideal way to harness and distribute renewable energy yet, one thing is for sure - they are a better long-term alternative than non-renewables.
- Here, we’ll learn about renewable energy resources.
- We’ll start by describing the meaning of renewable energy resources.
- Then, we’ll see some examples of these resources.
- We’ll continue with the renewable resources list.
- We’ll finish analysing the advantages and disadvantages of renewable energy resources.
The Meaning of Renewable Resources
Renewable energy resources are those which can be replenished or regenerated over short amounts of time.
Whatever we consume at a faster rate than it takes to naturally replenish becomes unsustainable. Something that is certainly not going to run out within our lifespan is solar power, for instance.
Fig. 1: The use of molten salt and sunlight to generate power. A series of mirrors focus sunlight into one single source: the salt, heating it up to very high temperatures. Then, the salt will remain hot and emanate heat for long amounts of time.
Do the same principles apply to other renewable energy sources?
All renewable resources are slightly different from each other or generated by different biotic and abiotic processes.
Non-renewable resources, such as fossil fuels and the radioactive metals used in nuclear fission (e.g. uranium, plutonium, thorium), are usually replenished after geological eras (a hundred million years or more).
Renewable resources examples
Other renewable resources include wind power, geothermal, and water, as well as materials like wood or plant fibers like bamboo. Wind and water power can be used indefinitely to produce mostly electricity and kinetic (movement-based) power (e.g. grain-crushing windmills).
Fig. 2: The image shows a concept art of Oceanbird, Wallenius Marine's wind-powered cargo ship. There are all sorts of hybrids and models, but generally, modern wind-assisted ships use large sails that can be operated by a small number of people or even only one person!
Our harvesting techniques of renewable resources need to be safe enough to not cause their net total reduction. I will explain how that can happen in the example below.
Both saltwater and freshwater could be evaporated faster than they get condensed and precipitate back onto Earth. How? Climate change and rising temperatures kickstart higher evaporation processes. This is an example of total net reduction. Net refers to what remains after other processes have occurred.
Most renewable resource availability depends on planetary cycles. Any activities that affect these cycles (e.g. the water cycle aiding cloud formation) will also affect our ability to tap into the supply of renewable resources.
Wind power is unlikely to disappear because it is generated by the Coriolis effect - the axial rotation of the Earth caused by gravitational forces causing more buoyant objects such as water and air to move from one specific direction to another.
The sustainability of renewable energy resources
Sustainable refers to a method, activity or element that can positively support social and ecological processes of continuity as time goes on. An energy source that is sustainable does not get to be permanently damaged or depleted.
Renewable resources are usually deemed sustainable, whereas non-renewable energy sources are deemed unsustainable. It is important to remember this is not always true. So, why is this?
Renewable energy can be both sustainable and unsustainable.
Unsustainable renewable resources include biofuel produced from clearing rare forest habitats and water used from underground reservoirs that affect the water table levels (underground water levels on which animal, plant, etc. species depend). The unsustainable use of renewable resources can further cause extinctions among migratory aquatic species such as sturgeons, salmonoids and river dolphins.
Other organisms also need renewable resources in order to survive and thrive.
Wood (timber) also needs to be protected against overexploitation, like bamboo. This is because different trees have different growth rates. A pine wood plantation may be harvested every 30 years, whereas oak trees may only reach maturity at 100 years old. If they're harvested earlier, they don't have time to produce acorns and thus won't propagate to ensure the species' survival!
Sustainable renewable resources include hydropower, wind, and solar.
The human constructions that come alongside hydropower stations may affect the way water flows and functions, to such a degree that it can make it disappear altogether. How? Take a look at this Mekong River analysis:
Hydropower dams cause unnatural river drought and flood-like conditions because they often divert water around entire sections of rivers, making them dry or worse. The upstream construction of hydropower dams may drastically intensify climate change impacts due to changing the natural river flood-drought cycle and reducing the amount of water that flows into the lower Mekong Delta.1
Renewable resources list
There is a traditional list of renewable resources that can typically be exploited through the use of technology, and it is really very interesting, not least because it needs to be updated every other year due to new discoveries. Elemental energy will include solar, geothermal, wind and water energy.
Fig. 3: Electricity generated in the UK has become more renewable in the later years after the 1990s.
Solar power is the conversion of sunlight into electricity. Technologies that can harvest solar radiation usually turn it into electricity or heat, for example, the use of PV (photovoltaic) panels and solar thermal systems, respectively. The energy can also be obtained by orienting a building towards the direction in which the sun rises (South), and using materials that have good thermal absorption and retaining properties (i.e. anti-reflective, fig 1).
Air-source and ground-source heat pumps use thermal energy (heat) as their energy source, although they can also use non-renewable sources to function. PVs come in multiple shapes and sizes, even as individual cells, and there are transparent PV panels that can be placed in windows. Mirror or lens systems that concentrate solar radiation in one spot are usually called CSP (concentrated solar power).
Water power includes hydroelectric power (HEP), wave power, and tidal power.
HEP typically includes two types of turbines: low head for shallow waters, and helical, which are most commonly used commercially, and they are both selected depending on water height and flow volume. Wave and tidal power both aim to harvest the kinetic energy of water for activities such as electricity production, desalination, etc. Their placement differs in that wave power may be placed near the surface of waters where strong currents and winds create waves, whereas tidal power needs additional constructions for power, such as a dam, enclosing an area of the sea, like tidal lagoons do, or in-stream marine turbines that can use oceanic currents as well.
Wind power has traditionally been associated with sail ships (wind-assisted ships) which still exist today (Fig. 3). Both vertical and horizontal wind turbines typically provide electricity or physical power needed to grind materials, like windmills used to do.
Horizontal Axis Wind Turbines (HAWT) have blades parallel to the wind stream, and Vertical Axis Wind Turbines (VAWT) have blades perpendicular to the wind stream.2 Power and maintenance are influencing factors when selecting a wind turbine.
Geothermal power is unique in that it comes from beneath the Earth, from the active magmatic processes.
Geothermal power can be very high temperature, but low-temperature technology prefers a ground fluid maximum of 150 °C, which can then be used to heat multiple living blocks or houses, fisheries or industrial processes.3
Biofuels are an interesting "renewable" energy resource because they have, at times, not been renewable, due to wildlife habitats being removed for monocultures with plants fit for biofuel productions.
Biofuels come from plant biomass most often, and can be produced by:
- Anaerobic digesters (microorganisms confined in large chambers) in the form of heat and pressurized gas or even liquid (biogas - carbon dioxide and methane).
- Intentionally grown crops that ferment quickly and produce alcohol-based fuel (ethanol), like sugarcane.
- Matter that decays rapidly, such as algae, which produce large quantities of hydrogen.
We have been dreaming about nuclear fusion for a while. It definitely helps that it can be obtained from what happens to be the most abundant gas in the universe - hydrogen. A Tokamak is a fusion nuclear reactor still in the experimental stages that aims to recreate nuclear fusion on Earth.4
Uses of renewable resources
Many renewable resources are crucial to life on Earth. Some renewables may offer a more sustainable alternative to finite fossil fuels. They also have some drawbacks, such as their intermittent nature and initial high cost, but offer a promising solution for the future of our planet.
Renewable resources advantages
Let's summarize some of the advantages of renewable resources:
- It is abundant and exists in many forms.
- Wind, solar and hydropower tend to be more cost-effective than oil and gas extraction, which require refineries and special platforms.
- Renewable energy is constantly evolving meaning we are constantly finding new ways to produce it.
- Fossil fuels are also associated with health problems from their released greenhouse gases and toxic pollutants. Renewable energy sources do tend to have lesser polluting qualities, although it still depends on the facility in which the technology that harvests renewable energy is manufactured and according to what environmental standards and specifications are followed.
- It is a constantly developing field meaning the pricing of renewable energies will continue to go down.
Technology that efficiently harvests renewable energy sources can be difficult to develop but may be able to operate more independently and be more long-lasting.
Gas and thermal energy can both be compressed in chambers and stored for later use. These are both considered new energy storage methods. This helps with the production of hydrogen fuel cells, rechargeable batteries, or the conversion of surplus energy (power to gas systems) in what is known as "the hydrogen economy". In a hydrogen economy, hydrogen produced from renewable resources may be pumped into gas pipes and blended with other fuel gases to generate heat!
Smart charging has also become extremely popular, especially due to electric cars. This means that people connect their cars to an electricity grid in order to get power. Reverse "charging" where the car gives back power to the grid is currently investigated as an option (vehicle to grid systems).
Disadvantages of renewable resources
Now, let's compare to some of the disadvantages of renewable resources:
- A lot of renewable resources depend on the location they are in eg. Solar panels require sunlight.
- Distribution networks must be created in order to utilise the power obtained from renewable resources and this often requires use of fossil fuels.
- Storage capabilities are required to ensure the energy can be accessed 24/7.
- In many instances, renewable energy relies on fossil fuels and biofuels still releases pollutants when burnt.
- Some forms of renewable energy take up lots of space.
- Renewable energy sources are known to be intermittent and to fluctuate depending on seasons, day and night cycles (24h), or other factors.
The technology for transportation and storage is still being developed, and renewable energy resources are not yet as reliable in terms of power output as fossil fuels however it's important to remember that renewable energy sources are constantly advancing.
Hopefully you now know more about renewable resources as well as some of their advantages and disadvantages.
Renewable Resources - Key takeaways
- Renewable energy resources are important because of the urgent need for sources that do not emit greenhouse gases or toxic pollutants that further aggravate climate change or pose significant public health concerns.
- Nuclear fusion, such as from the Sun, could be considered the ultimate renewable energy resource as it is the least likely to be extinguished, and forms the basis of all trophic chains in nature.
- Wind power tends to be the most used renewable resource, whereas tidal remains the most underrepresented.
- Renewable energy resources, or our access to them and methods of harvesting, can be considerably improved, such as through developing better fuel batteries.
- Some renewable energy resources aren't necessarily sustainable, for example, certain hydropower turbine and dam placements are deleterious to wildlife and have led to multiple extinctions.
References
- Hydropower dams, river drought and health effects, sciencedirect, 2021, https://www.sciencedirect.com/science/article/pii/S2212096321000097. Accessed 02/09.22
- Difference Between Horizontal and Vertical Axis Wind Turbine, S. Khillar, 2019, http://www.differencebetween.net/technology/difference-between-horizontal-and-vertical-axis-wind-turbine/. Accessed 05.09.2022
- Low Temperature & Coproduced Resources, energy.gov, 2022, https://www.energy.gov/eere/geothermal/low-temperature-coproduced-resources. Accessed 05.09.22
- Nuclear Fusion Power, world-nuclear, 2021, https://world-nuclear.org/information-library/current-and-future-generation/nuclear-fusion-power.aspx. Accessed 05.09.22
- Fig. 1: 50 MW molten-salt power tower in hami (https://commons.wikimedia.org/wiki/File:50_MW_molten-salt_power_tower_in_hami.jpg) by Csp.guru (no author page), under CC BY-SA 4.0 License
- Fig. 2: Wallenius Marine’s Oceanbird ship concept (https://commons.wikimedia.org/wiki/File:Wallenius_Marine%27s_Oceanbird_ship_concept.jpg) by Wallenius Marine (no author page), under CC BY-SA 4.0 License
- Fig. 3: Hannah Ritchie, Max Roser and Pablo Rosado (2022) - "Energy". Published online at OurWorldInData.org. Retrieved from: 'https://ourworldindata.org/energy' [Online Resource]
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