Emily Chen
Mr. Mark Duf eld
May 10, 2022
Reflecting on the Impact of Science
“Fossil fuels are a dead end – environmentally and economically,” said
António Guterres, the secretary general of the UN. (World Meteorological
Organization) As a reliable, e cient, cost-e ective natural energy resource
with its current wide availability, fossil fuel consumption accounts for 84.3% of
world energy, and 63.3% of electricity-only. (Ritchie et al.) With the everincreasing demand for electricity and fossil fuels in industry, transportation,
construction, and households, large amounts of CO2 and CH4 have been emitted
into Earth’s atmosphere. As a result, sea-level rise, ocean heat, ocean
acidi cation, and greenhouse gas concentrations, four key global indicators of
the climate crisis broke records in 2021, according to WMO (World
Meteorological Organization)'s UN report on 18 May 2022 - “State of the Global
Climate 2021“. (World Meteorological Organization). Climate change is
happening right before our eyes, and all this change is irreversible. As Mr.
Guterres proposed in the video message, there is an urgent need to jump-start
the renewable energy transition. (World Meteorological Organization) While
fossil fuels can meet a signi cant portion of high electricity demand, starting to
use renewable energy sources such as hydropower, geothermal and solar
energy can reduce the burning of fossil fuels, thereby decelerating global
warming.
As one of the biggest carbon-free sources, hydropower is undoubtedly an
ideal energy source that has already takes up 15.8% of global electricity
consumption. (Ritchie et al.) First by building a hydroelectric dam on a wide
river that has a large drop in elevation, allowing gravity to cause it to fall
through the penstock inside the dam. (Water Science School) At the end of the
penstock, the high-pressure water ows through and turns the turbine, and the
shaft from the turbine connects to the generator upward, this is where kinetic
energy turns to mechanical energy, and produces secondary energy —
electricity. (Water Science School) The hydrologic cycle allows this power
system to function sustainably, generating renewable energy, with much less
carbon emission. (Water Science School) The construction of a hydroelectric
dam requires expensive up-front, but it’s also worthwhile and bene cial in the
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long run since the facility can function for at least 50 years with constant
electricity production. Water stored in the dam can also be used for irrigation.
(“Pros and Cons of Hydropower | EnergySage”) Furthermore, it’s produced
domestically, which means the country can take full control over its distribution,
so there’s less worry to be a ected by political standpoint and resulting in
energy being cut o , monopolized by other countries. The only disadvantage is
that it relies on the local hydrology, but as long as the facility is constructed in a
location with su cient and constant rainfall,
the impact of occasional droughts is
negligible. As it can be seen from Figure 1, in
the year 2021, hydropower accounted for
roughly 15.34% of China’s electricity
production while fossil fuel takes up 66.95%.
(Ritchie et al.) This shows that there is still
much space for improvement in the energy
transition. But overall, being in the third place
in China’s electricity production ranking with
Figure 1. Share of electricity
4206 terawatt-hours of hydroelectric power
production from hydropower (China)
shows its massive potential and a good start.
Geothermal energy is a carbon-free,
sustainable energy source that is still largely unexploited. As shown in Figure 2,
it’s currently accounted for less than 2.5% of the global electricity
consumption. (Ritchie et al.) There are three types of electricity plants with
di erent systems to harness geothermal
energy. The rst one is called ‘dry steam’,
it’s similar to burning fossil fuels, by having
steam above 150°C owing from the reservoir
to provide the mechanical force required to
spin the turbines, and then generate
electricity with the generator
connected. (ERCE) The second method is
Figure 2. Shares of different energy
called ‘ ash steam’, water with temperatures
source from total energy/electricityabove 180°C pumps up through wells in the
only consumption (worldwide)
ground by its pressure. (ERCE) It is kept
under pressure until it is ‘ ashed’ at the
surface to produce steam. (ERCE) The remaining water and condensed steam
will be injected back into the reservoir, to gain heat from the surroundings and
be reused. (ERCE) The third method is the binary cycle power plant. Water with
temperatures as low as 100°C is pumped up through wells. The heat from the
hot water boils a second uid that has a low boiling point, aka the ‘working
uid’. (ERCE) The vaporized working uid pushes the turbines, then condenses,
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and is vaporized again by the continued supply of heat from the geothermal
waters. (ERCE) The geothermal water is sent back into the ground to be
reheated for the next cycle. (ERCE) The most obvious advantages of
geothermal energy are environmentally friendly and renewable, the whole
process of generating electricity goes underground with no greenhouse gas or
waste created during the process. Another advantage of geothermal energy is
that they are available everywhere on earth as long as you have the
technologies to build the power plant enough deep and the permission from the
local government. However, geothermal energy runs the risk of triggering
earthquakes, due to its exploitation of the Earth. (TWI) This problem is more
common with enhanced geothermal power plants, which force water into the
Earth’s crust with wider gaps. (TWI) But considering that most geothermal
plants are away from the population centers, the impacts of earthquakes
caused by the exploitation are relatively minor. Another disadvantage of
geothermal energy is that they are not mature enough, at the moment, new
technologies are in the exploration stage to improve the energy process. For
example, to maintain the sustainability of the geothermal energy, the ‘working
uid’ needs to be pumped into the underground reservoirs faster than it
depletes, technologies are being created
to solve this problem. (TWI) As
demonstrated in Figure 3, the global
evolution of geothermal power started in
1950 and reached 14600MW of installed
capacity by 2018. (Zhang et al.) Thus, we
can conclude that there is a market,
demand, and basic practice of geothermal
energy, and so, this technology will likely
Figure 3. Geothermal power installed
to develop further. Overall, geothermal
capacity evolution in the world from
energy is an ideal renewable energy
1950 to 2018
source with great potential to replace
fossil fuels even though it’s still in development.
As a renewable energy that can be harnessed directly from the sun, solar
power has been widely recognized, as
shown in Figure 4, its worldwide Installed
Capacity has grown steadily during the
past ten years, from 2011 to 2021. (IRENA)
Furthermore, the growth of solar power’s
Installed Capacity in China has
accelerated during the three years
between 2015 and 2018 as displayed in
Figure 5. (IRENA) There are two ways of
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Figure 4. Solar power installed capacity
evolution in the world from 2011 to 3
2021
References
ERCE. “Untapped Geothermal Energy - ERCE.” ERCE, 21 Dec. 2020,
www.erce.energy/latestnews/untapped-geothermal-energy/. Accessed 19
May 2022.
IRENA (International Renewable Energy Agency). “Solarn Energy.” Irena.org,
2022, www.irena.org/solar. Accessed 20 May 2022.
“Pros and Cons of Hydropower | EnergySage.” Energysage.com, 2021,
www.energysage.com/about-clean-energy/hydropower/pros-conshydropower/. Accessed 20 May 2022.
Ritchie, Hannah, et al. “Energy.” Our World in Data, 28 Nov. 2020,
ourworldindata.org/electricity-mix. Accessed 19 May 2022.
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generating solar power, photovoltaics (PV)
and Concentrated solar power (CSP).
(IRENA) Compared with PV, which can be
used for both personal use and
commercial scale, CSP can only be used
industrially, because CSP requires largescale power plants to generate electricity
with cost-e ectiveness and e ciency.
CSP has the same mechanism to generate
electricity as burning fossil fuels, both by
heating the water rst, then operating the
Figure 5. Solar power installed capacity
turbine with steam and so to generate
evolution in China from 2011 to 2021
electricity, the only di erence is that the
source of heat used to evaporate water is
di erent - in this case, solar rays are concentrated by mirrors to heat the water
instead of burning fossil fuels. With advantages such as diverse application, low
maintenance, and long-term cost-e ectiveness, solar power have limitations of
weather dependent and relatively high space occupation.
Hydropower, geothermal energy and solar energy are good alternatives to
fossil fuels as low-carbon, renewable energy sources. Existing examples and
data have proven they are feasible and able to meet the high electricity demand
of households, while reduce environmental consequences of large energy
consumption of fossil fuels - global warming. However, they still have a lot of
work to do in completing the technology’s development, which can be done with
time. Overall, their potential outweighs the limitations, and most importantly,
they represent an important advance in addressing global warming.
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TWI. “What Are the Advantages and Disadvantages of Geothermal
Energy?” Twi-Global.com, 2022, www.twi-global.com/technical-knowledge/
faqs/geothermal-energy/pros-andcons#WhataretheAdvantagesofUsingGeothermal. Accessed 20 May 2022.
Water Science School. “Hydroelectric Power: How It Works | U.S. Geological
Survey.” Usgs.gov, 30 Aug. 2018, www.usgs.gov/special-topics/waterscience-school/science/hydroelectric-power-how-it-works. Accessed 20 May
2022.
World Meteorological Organization. “Four Key Climate Change Indicators
Break Records in 2021.” World Meteorological Organization, 18 May 2022,
public.wmo.int/en/media/press-release/four-key-climate-change-indicatorsbreak-records-2021. Accessed 20 May 2022.
Zhang, Lei, et al. “Geothermal Power Generation in China: Status and
Prospects.” Energy Science & Engineering, vol. 7, no. 5, 29 May 2019, pp.
1428–1450, onlinelibrary.wiley.com/doi/epdf/10.1002/ese3.365, 10.1002/
ese3.365. Accessed 20 May 2022.
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