Energy Engineering: The Blueprint of Our Sustainable Future

Our planet is on the brink of climate catastrophe!

Scientists warned us of "untold suffering due to climate crisis", according to The Guardian, if greenhouse-gas emissions are not reduced drastically in the foreseeable future [1].

Greenhouse gas emissions. Photo from Unsplash

It is an easier task said than done. Unfortunately, even though we can turn off the AC when not needed, it is not enough to turn the tide.

Evolution of the electricity supply is fundamental. Instead of recklessly devouring fossil fuels, a transition to greener and renewable energy resources is a must. This concerns the field of energy engineering, as innovative energy supply-system is utmost necessary for efficient renewable energy usage [2].

Nations and Big Companies Starting to Use Renewable Energy

In the last decades, as renewable energy became one of the main pillars of many nations' policies, sustainable energy infrastructures become high in demand.

Until recent years, renewable electricity consumption in the EU totals at about 18%, while over 25% worldwide [3, 4]. Besides governments, major corporations are also leading the renewable energy movement.

Starting in 2014, Apple's California main data centre has been completely powered by renewable energy. Another example is INTEL, which has spent over 3 billion kW hours of various green electricity and constructed solar plants to supply its facilities a huge amount of power [5, 6].

How exactly do these renewable energy infrastructures create our daily electricity? And how do these sites affect the surrounding environment and our society?

Most popular renewable energy resources

1. Hydro

Globally speaking, hydropower makes up 3.6% of the estimated renewable energy consumption [4], and China is well-versed in constructing hydropower facilities.

The Three Gorges Dam in Hubei has been crowned one of the largest hydropower plants in the world [7].

The Three Gorges Dam. Photo from Flickr

How exactly does a hydropower plant work?

Well, with a dam holding back the upstream water of a river, the river must rush through the dam gates, spinning the bulky turbines and the attached generators placed inside at racing speed. The generated electricity is transferred through connected power lines, while the used water is released downstream via the gates [8].

No fossil fuels are burnt, meaning hydropower is clean and renewable. Additionally, the amount of water flow can be controlled to suit the ever-changing needs during different periods. The economy in that region can also gain from recreational businesses surrounding the dams, such as sightseeing and fishing [9].

However, hydropower plants can also be quite problematic. Take the Three Gorges Dam as an example, right from the beginning of the construction, locals living upstream were evicted, and their villages were soon submerged.

These locals then suffered from low-earnings and expensive living costs after relocating to major cities. The animal and plants also lost their habitat, and biodiversity on that area was destroyed. Besides the construction itself, landslides also destroyed homes, as they were by-products of the riverbanks being eroded by the manipulated rise and fall of water levels.

But perhaps a terrifying unforeseen consequence is the increased seismic activity by the constant shifts of water volume, which might lead to earthquakes [9,10].

2. Wind

Wind power is not new. Wind energy have been used to propel boats and pump water as early as 5000 BC. However, the idea of generating electricity through wind turbines did not surface until the late 1800s.

Wind power plant. Photo from Unsplash.

Wind turbines use the wind speed (about 8 to 16 miles per hour) to rotate their blades (3 of them, mostly about 60m long), causing the shaft inside to spin up to 1800 rotations per minute, driving the generator for electricity production [11].

The costs of wind energy infrastructures are getting lower due to its increasingly common use, in return reducing electricity bills. Landowners can profit from the wind power market, by renting the land to directly providing electricity service. Due to the lack of fuel cost, wind farms bring profits to both major and small electricity providers in the long term.

Nonetheless, some setbacks we need to bear in mind, namely the danger to wild birds, the alleged "noise pollution" brought to residential areas (about 40 to 50 dB, like that of an air conditioner) [12], and the unreliability of wind. Storms can damage the wind turbines, putting surrounding residences in danger; thus, strict maintenance routines are necessary.

Besides the regular windmill, Australian inventor Saul Griffith wants to use kites to access high-altitude wind power. "… majority of 3600TW wind power in high-altitude, which we can't access, is enough to supply humanity over 200 times," stated Griffith during his TED talk in 2009, "… we are working towards megawatt-scale machines that fly over 2000ft to generate tons of clean electricity… a Gulfstream-sized kite (28.5m wide) can generate 1MW."

This means, when its potential is maximised, wind energy might be able to replace oil and become the most common energy resource [13].

3. Solar

In 2019, the International Energy Agency (IEA) forecasted 60% of the expected growth of renewable power capacity to be led by solar energy.

There are many solar technologies, such as solar thermal electricity and solar heating/cooling, but the most well-known one is solar photovoltaics (PV), commonly known as solar panels.

Usually, solar PV is made from silicon, with phosphorous and boron coated onto the top and bottom layers, respectively. The positive and negative electrons on the two coatings are separated by the silicon, creating an electric field in between. When the sunlight particles hit the PV, electrons are pushed out of the silicon layer. Metal conductive plates catch and transfer these stray electrons to the wires, where they flow as electricity [14].

The main reason for the steady growth of solar PV use is the continuous price drop. This is possible because researchers keep discovering cheaper and more productive materials than silicon.

For instance, scientists in Colorado State University found that the combination of cadmium telluride and selenium retain more light and heat while requiring 100 times fewer materials than silicon.

At CEITEC BUT, Jan Macák and his Advanced Low-Dimensional Nanomaterials research group are also testing various nanomaterials for solar PV.

Solar panels. Photo from Unsplash

Solar panels can be integrated into construction materials such as roofs and windows, thus can be incorporated into domestic lives easily.

However, although still functional, solar panels generate significantly less electricity during rainy and cloudy weather, not to mention night-time. Plus, some people might not like their solar panels taking up all their backyards. Adding up the costs wiring and inverter, the installation of a solar panel can be high. Hopefully, this will change in the future [15].

However, generally speaking, using solar electricity saves money in the long run [15]. To put it into perspective, the cost of solar PV is euro 0.09/ kWh (continuing to decrease), while that of fossil fuels fluctuates from euro 0.045 to 0.16/ kWh [16].

Ultimately, the biggest advantage of solar panels is that it allows people to live off-grid (independently), as opposed to on-grid (a central generation at the dispatch centre distributing electricity to users, connected by the electrical grid).

With solar panels installed, people living in isolated regions can produce their electricity, thus improving their quality of life.

"Every household a proud producer as well as consumer of energy. That's the democracy of energy." Said Amar Inamdar, East African investor with a vision of bringing power to disadvantaged consumers [17].

4. Biomass

Biomass has the most extended history. Since man discovered fire, wood and crops had been burned for heating and cooking.

As of 2017, bioenergy accounted for around 12% of total renewable energy supply globally, according to REN21 (Renewable Energy Policy Network for the 21st Century).

Biomass is most commonly burned in a boiler to create steam, pushing the interior turbines to rotate, and thus activating the attached generator to produce electricity.

Liquid biofuels, namely Ethanol and biodiesel are both by-products of fermented crops. By separating glycerin from the oils in plants and food wastes, only methyl esters are left, which is the chemical name for biodiesel [18, 19].

Usually, liquid biofuels are used for transportation. And lastly, biogas, which is a combination of methane and carbon dioxide, is the by-product of fermentation of organic matters, such as manure from livestock, sewage, and agroindustrial wastes. In biogas plants, wastes are poured into airtight fermenters for heating and stirring. Gas forms as bacteria and other microbes digest the fat and carbohydrates in the wastes [20].

Woods and crops can be used as biomass. Photo from Pixabay.

Biomass production requires constant inputs, such as water for replantation of trees and crops. This can be a burden for the water supply, especially in regions with frequent droughts.

Speaking of replantation, higher yields are necessary to satisfy both food and fuel needs, which can be competing interests. Farmers ought to beware of exhausting farm soils of its minerals and nutrients.

Overuse of chemicals such as pesticides also damages the quality of soil in the long run [21]. Assessing, purchasing, replanting, harvesting and transporting of biomass are never-ending. On the bright side, numerous jobs for different procedures can be created. Various industries can share the economic benefits of biomass energy production [22].

Although biomass is gone forever once used, it is considered renewable because of replantation. This makes biomass energy carbon neutral. Meaning that even though the use of biomass releases carbon dioxide, the gases can be absorbed back by replanted trees and plants, or through re-incorporation of plant residues, such as cereal straw, into the soil, creating a neutralising cycle [21].

But the renewal of biomass depends heavily on our effort [21]. Close monitorization is necessary to balance the released and reabsorbed amount of carbon dioxide. If biomass is used faster than it is restored, the issue of pollution, as well as soil depletion, resumes.

Similarly, if the demand for biomass energy exceeds the supply, more biomass will have to be harvested, leading to the risk of deforestation.

But the issue with pollution does not end there. When biomass is combusted, black and flaky impure pollutes called "soot" may be released. Depending on the amount, breathing in these pollutes can lead to sickness and premature death.

Residents near biomass plants are in danger of health issues after a long time [23]. Careful consideration is essential for the locations of biomass plants, as well as the types of biomass being combusted, and the measures taken for exhaust containment.

With such disadvantages, one may wonder why the world should invest in biomass development. Firstly, as the earth becomes increasingly over-crowded, the amount of waste from humans and livestock inevitably rises. Using biowaste, as well as discarded food as fuels, serve as waste reduction [21].  Why not use our wastes to generate power for the world?

Also, biomass is praised for its versatile variabilities. Unlike other types of renewable sources, crops can be grown for biomass. Industrial wastes such as sawdust can be mixed into wood pellets to be burned; animal wastes are available from cattle ranches. If one is unavailable, there are always other options [21].

5. Geothermal

The estimated temperature underneath the sub-surface of the earth is 6000 C0.

Like solar heat, the energy released by geothermal heat is immense. The International Renewable Energy Agency (IRENA) estimates geothermal heat currently amounts to about 0.3% of global electricity generation, with countries having plenty of hot springs or volcanic activities, such as Iceland and New Zealand, being the biggest producers and consumers [24].

Geothermal power plant in Iceland. Photo from Pixabay.

Geothermal heat is carried through underground water.

In a geothermal power plant, wells are drilled to pump hot water up to the surface. Water turns to steam as atmospheric pressure drops. The steam spins the turbines, activating the linked generators into producing electricity. Afterwards, the steam flows into a cooling tower, where it is condensed and pumped back into the underground [25].

Geothermal heat can't be extinguished, meaning it is renewable, as fossil fuels are not burned, and carbon dioxide emission is low. It is also available 24/7 all year round.

However, "greenhouse gases" do not only consist of carbon dioxide. The lack of carbon dioxide emissions is replaced by other toxic gases, such as sulphur dioxide and hydrogen sulphide, both are common by-products of hot springs and volcanic activities, released from magma.

The American Lung Association states that sulphur dioxide is particularly harmful to people with asthma. To those without asthma, this gas can induce respiratory symptoms such as shortness of breath and chest tightness.

Similarly, hydrogen sulphide is a rotten egg-smelling toxic gas that, when inhaled in high concentration, can result in nausea, coughing, eye damages, and even death.

When installing geothermal power plants, underground reservoir rocks need to be drilled. As a result, seismic activities can become more frequent, increasing risks of earthquakes. This also highlights another issue: although geothermal heat is available constantly, it is only found in specific locations with volcanic activities. Therefore, geothermal heat is not suitable for numerous regions around the globe [26, 27].

6. Ocean Waves (Hydrokinetic)

With the sweeping of wind over the surface of the ocean, come waves, storing stronger kinetic energy for generating electricity [28].

However, despite potential wave electricity generation estimated to be 1700 TWh per year globally, which is about 10% of global need [29], it is not as widely utilised as the other energy sources. Countries that have wave power stations include the UK, Portugal, Greece, and so on.

As of now, 3 leading wave energy converters (WEC) are most used in generating electricity from waves. There are the absorbers, shaped like point-shaped buoys. By floating on the ocean surface, they store the kinetic energy from the oscillating flow of waves.

The energy goes through the connecting cables to the generator, all under the ocean, for conversion and distribution [30]. Second, an attenuator, like an absorber but is long and tube-shaped, placed across the waves. Flexing with the movements of the waves, the attenuator captures the motions and the energy [30].

Straying away from the two mentioned floating devices, we also have oscillation water columns (OWCs). Imagine having an awning, its bottom submerged into the ocean. The top is attached to the shore, trapping air inside the column. As waves crash onto the shore, they rush into and out of the bottom between the awning and the shore, thus compressing and decompressing the packed air above. The air pushes and pulls the turbine connected [30].

A attenuator. Photo from Flickr [44]

Wave energy holds promising potentials, as it is reliable and renewable [31]. Also, as the ocean is the largest body of water on our planet, it is suitable for many regions. Transportation to power plants is not needed, meaning the carbon footprint is small [32].

No greenhouse gases are emitted [30]. Wave energy infrastructures can also contribute to job demands along the coastal regions, contributing to the economy [32].

Then why is it that wave energy is not as popular as wind and solar energy?

To start, the ocean is harsh- saltwater and wave crashings can be corrosive to the devices [33]. That is why wave frequency and wave direction assessments prevent unnecessary damages [31].

Another thing is the complicated calculation of the wave energy. For other energies, the stronger the wind or sunlight the better.

But for wave energy, the wave heights, speed, length and density ought to be considered [34]. Considering installation, assessments and maintenance, establishing wave power farms can be expensive [30]. That's why most wave energy infrastructures are small-scaled. As such, studies about the influences of larger-scaled wind energy infrastructures on marine life are few [30].

Still, it is merely too regretful to abandon such a vast and ready resource. Existing technologies are imperfect but functional; that is why many companies like Ocean Power Technologies aim to improve buoy-based technology [33].

Fully submerged WECs also receive much attention. The company M3 Wave experiments on submerged devices- passing waves from above push air to move between compartments inside the device, thus spinning the attached turbine [33]. Besides companies, EU funded researchers are also developing a WEC system built with more advanced generators and much cheaper, flexible and robust materials [35].

7. Hydrogen

When natural gas is heated with steam, ranging from 700 C0 to 1000 C0, the methane in the natural gas decomposes into hydrogen and other gases, such as carbon monoxide, which is always further disintegrated into more hydrogen [36].

Should hydrogen be considered renewable energy?

By logic, over 90% of hydrogen is manufactured with natural gases. However, 5% of it comes from renewable sources, such as solar and biomass. This means hydrogen could be renewable, but the common practice makes it not so [37].

Hydrogen is mostly used in transportation.

Hydrogen fuel cells can power electric vehicles (EVs). Much like filling in gas at a gas station, pressurised hydrogen can be purchased and refilled into the fuel cells. While other EVs are recharged by plug-in, hydrogen fuel is converted into electricity by the batteries while driving.

This eliminates recharging time, making car rides longer and more convenient. Speaking of efficiency, hydrogen EVs also have a better fuel economy compared to traditional vehicles, meaning they use only half the fuel for the same distance.

Hydrogen EVs also release over 30% fewer greenhouse gases than conventional vehicles. Hydrogen fuel cells emit mostly water vapour, as hydrogen is combined with oxygen [38].

Electric vehicles. Photo from Pxfuel

But despite being very clean, hydrogen EVs are not commonly seen on roads, as hydrogen EVs can be quite expensive.

Costly platinum is used for the catalysts that speed up chemical reactions in hydrogen fuel cells. With the high price, demand for hydrogen EVs is too low for widescale hydrogen charging infrastructures set up, making switching to hydrogen EVs a challenging option [38].

Researchers from the Technical University of Berlin have tried using copper-platinum nanoparticles instead of pure platinum.

Another research team from Princeton University wants to replace platinum with hafnium-based materials.

CEITEC-BUT is a participant of the Industry 4.0 project of Research and Innovation Centre on Advanced Industrial Production (RICAIP). One of the objectives is to increase the use of hydrogen EVs in the Czech Republic [39]. Improving charging infrastructures and fuel cells productivity is the way to go.

Energy Storage: Save it for Later

A prominent issue with many renewable energy resources is that they are not available constantly. Sometimes you want to watch TV all day, but it is too cloudy for the solar panels to work; then other times the strong wind is spinning your windmills at full force, but the electricity is wasted because you are at work.

By saving electricity for later, on-grid users can save up on electricity bills, while off-grid users can ensure self-efficiency. Storage for electricity, namely a battery, is essential for renewable electricity utilisation.

Lithium-Ion Battery (LIB) and alternatives

The ongoing decrease of costs of battery storage systems has led the installations number to rise by 3-fold as of 2019, mainly driven by LIB.

Right now, LIB is one of the most common rechargeable battery, used for cell phones, electric cars and power grids [40].

As charged lithium ions go through a liquid electrolyte substance between the positive cathode and negative anode, stored electricity is activated [40]. Compared to other batteries, such as nickel-cadmium cells, LIB does not need regular discharge. It has a longer lifespan, higher voltage and density, thus enabling longer battery lives for electronics [41].

For all that, the robustness of LIB needs further improvement, as battery protection circuit are necessary to prevent the battery from passing its safe operating limit. LIB ages poorly as well, deteriorating after several hundred times of charging. Not to mention the relatively high manufacturing cost when compared to nickel-cadmium cells [41].

Above all, lithium extraction is harmful.

Lithium reservoirs are mostly in South America, coincidentally some of the driest places on the planet. During the mining process, holes are drilled deep into the ground, then approximately 500 000 gallons of water are poured in.

As the water evaporates, which can take over a year, 1 metric ton of lithium is to be collected on the surface. This procedure can take up around 65% of the water in the region. Also, with surfaced toxins seeping into the groundwater system and inducing acid rain, surrounding people and wildlife are threatened [42]. In many nations, the minings for lithium are often coupled with races for political control and financial gains [42]. Still, lithium is natural and, though limited, still bountiful, thus a revolution of its extraction and optimisation is necessary.

A Li-ion battery. Photo by Tony Webster, from Flickr

Even with all these limitations and many alternatives, such as sodium and cobalt, LIB remains the market's favourite, due to the continuous decline of price, pre-existing investment, and many unexplored potentials.

Tesla had tried plugging LIB into the grid, though the electricity supply only lasts for a few hours [40]. Sila Nanotechnologies and BMW Group cooperate in experimenting with a silicon-based anode, with larger lithium capacity and thus larger energy storage [40].

That's not to say that competitions do not exist for LIB. Here are some of the most prominent ones:

Graphene-based batteries are the runner-up in popularity.

Researchers and investors emphasis its faster charging time, longer lifespan, and lower risk of explosion (think Samsung Galaxy Note 7) [43].

Still, it remains in the lab for now. Another possibility is hydrogen fuel cells, but its high cost hinders its popularisation. As mentioned, CEITEC BUT is an integral member of RICAIP's Industry 4.0 project. One of the goals is to increase the use of hydrogen energy storage in the Czech Republic [39].

Lowering the material costs is a good way of doing so. Aquion had come up with saltwater battery in 2011. Designed for solar energy storage, it is environmentally friendly, fire-resistant and low priced. But its capacity is also small (about 1.6 kW per hour), requires cold operating temperature, and the unit is bulky.

Last but not least, dual carbon batteries have both electrodes made of the same material, carbon. In 2014, Power Japan Plus attempted to commercialise dual carbon batteries. They are also promoted to be reliable and safe.

At CEITEC BUT, Martin Pumera, the leader of Future Energy and Innovation research group, envisions the creation of solid LIB that can store more energy, and firmly believes in exploring the possibilities of futuristic energy storage and electricity generation ideas. 
Currently, he and his research team collaborate with Institutes in Singapore on electrochemical energy systems.

There is also Jan Macák, the research group leader of the Advanced Low-Dimensional Nanomaterials research group at CEITEC BUT. He is leading his team to study the application of titanium dioxide nanotubes to photovoltaic cells and batteries.

Ultimately, users need the security of knowing their batteries can be easily recharged.

For that, infrastructures for electricity back-ups, such as facilities for battery recharging ought to be sufficiently implemented.


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Written by Sophia Man

Edited by Somsuvro Basu & Markus Dettenhofer

Publication date: 30.04.2020