Current Situation and Prospect of Tidal Energy and Geothermal

Energy

Hewen Bai

1,*

and Haoze Qu

Jilin University College of New Energy and Environment, Jilin University, Changchun, Jilin, 130015, China

School of Chemical Engineering, Ocean and Life Sciences, Dalian University of Technology,

Dalian, Liaoning, 116081, China

Keywords: Tidal Energy, Geothermal Energy, New Energy, Enhanced Geothermal Systems.

Abstract: In the case of increasing shortage of traditional fossil energy, tidal energy and dry hot rock geothermal

resources have attracted much attention because of their huge development potential. However, the

development of tidal and geothermal energy is still in its infancy, and the amount of resources that have been

developed is small. In this paper, the development prospect, development technology and cost of tidal energy

and geothermal energy are discussed in detail, and a comparative analysis is made. Studies have shown that

the efficiency of current tidal energy applications is too low, there are technical barriers to intelligent control

and installation maintenance, and the impact on biodiversity, fisheries and other fields. Improving renewable

energy equipment technology and substituting advanced materials is the way to solve the dilemma of tidal

energy development. Enhanced geothermal systems (EGS) technology of geothermal energy has some safety

risks such as low development and application efficiency, easy to induce earthquake and so on. Changing

reservoir reconstruction methods to reduce safety risks and using new hydraulic fracturing methods to

establish horizontal fracture network to achieve high efficiency exchange of heat energy are the methods to

improve EGS performance. In the future, it is necessary to continuously improve the development, reserve

and application technology of tidal energy and geothermal energy. This study hopes to broaden.

1 INTRODUCTION

With the decreasing of the three traditional resources,

the human thirst for new energy is getting stronger

and stronger, and the development and utilization of

renewable energy has become an important

development direction. Tidal energy and geothermal

energy have attracted worldwide attention because of

their low carbon, high efficiency and renewable

characteristics. The two kinds of energy have

abundant reserves and broad prospects and have great

research significance. Tidal energy refers to energy

from the ocean and tidal movements, while

geothermal energy refers to energy from deep heat

sources on Earth.

In the early 20th century, some countries in

Europe and the United States began to study tidal

power generation, in 1913 Germany established the

world's first tidal power station on the North Sea

coast, France, the Soviet Union, and Canada have

Corresponding author

built tidal power stations. It has been more than 100

years since the establishment of the first tidal power

station, and now the technology of tidal power

stations is becoming more and more mature, and the

power stations are also slowly turning to large-scale

(Luo, 2015). Nowadays, most of the areas that use

tidal energy widely are distributed in the coastal

countries of Europe, Canada, Australia, South Korea,

China and so on.

The specific distribution of geothermal dry hot

rocks is known: the Gulf of Mexico of the United

States, the Pacific coast countries of South America,

the Korean Peninsula, Japan, northwest of China and

other regions. In the 1970s, geothermal energy

research began, initiated by the United States, then

Britain, France, Japan and other countries joined the

engineering research, to verify the feasibility of

mining hot dry rock heat. Influenced by this

achievement, the hot and dry rock research has started

in the world. The United Kingdom and Japan have set

Bai, H. and Qu, H.

Current Situation and Prospect of Tidal Energy and Geothermal Energy.

DOI: 10.5220/0013895300004914

Paper published under CC license (CC BY-NC-ND 4.0)

In Proceedings of the 2nd International Conference on Renewable Energy and Ecosystem (ICREE 2024), pages 235-240

ISBN: 978-989-758-776-4

235

up special studies on rock mechanics, respectively,

and come to the conclusion that natural fractures are

affected by the original ground stress, and thus affect

the effect of artificial thermal energy extraction (He,

2021). These two kinds of energy have a wide range

of application prospects in the world, and provide

unlimited possibilities for human production and life.

With proper planning and development, the use of

tidal and geothermal energy will contribute to

sustainable development worldwide.

The main purpose of this paper is to explore two

new energy sources, tidal energy and geothermal

energy, based on the world's demand for new clean

energy. Firstly, the development status, development

technology and advantages and disadvantages of tidal

energy and geothermal energy are introduced, hoping

that more people can understand tidal energy and

geothermal energy. Then, the similarities and

differences of the two new energy sources are

compared from multiple angles. Finally, the paper

puts forward suggestions for the future development

direction of two new energy sources.

2 TIDAL ENERGY

2.1 Development Status

Tidal energy is a kind of renewable energy which uses

the kinetic energy and potential energy generated by

the periodic fluctuation of sea water to generate

electricity. It has the advantages of green, renewable,

stable and reliable. Currently, the total installed

capacity of tidal power generation worldwide is

small, only about 500 megawatts, but in recent years,

as countries' demand for clean energy continues to

increase, the development of tidal energy has received

more and more attention. Europe, particularly the

United Kingdom, France and Ireland, has made

significant progress in tidal energy technology and

construction, accounting for more than 86% of the

world's installed tidal power capacity. In comparison,

the installed capacity in the Asia-Pacific region is

relatively small, but as China and South Korea speed

up the development and construction of tidal power,

the region of the tidal power market is expected to

rapid growth in the coming years.

2.2 Advantages and Disadvantages of

Tidal Energy

Tidal energy is a renewable energy source that

persists in the ocean, does not cause energy shortages

due to the exhaustion of renewable energy sources,

does not produce carbon dioxide, nitrogen oxides,

sulfides and other pollutants, and is less polluting to

the environment. Tidal energy has a relatively long

time period during tidal fluctuations, so it is more

stable and reliable than solar and wind power, and the

energy quality is higher. At the same time, there are

many coastlines around the world, so tidal power

generation is relatively flexible in terms of

application, especially for those areas that are not

suitable for solar and wind power generation, tidal

power is a good alternative energy source. However,

the technology of tidal power generation is costly and

may also have an impact on the Marine ecological

environment.

2.3 Development Technology of Tidal

Energy

Traditional tidal energy development and utilization

are mainly single-pool bidirectional, single-pool

unidirectional, dual-pool unidirectional and dual-pool

bidirectional. At present, the single reservoir mode is

mainly used in the international operation of

damming tidal power station (Liu et al, 2018). For

example, the Lancs Tidal Power Station (240 MW),

built in 1966 at the mouth of the St. Malo River in

France, uses a single reservoir bidirectional operation

mode, that is, it can generate electricity at high tide or

low tide; Built in 1979, the Bell Island Tidal Power

Station (2.7 MW) in Canada uses a single reservoir

one-way operation mode, that is, electricity is

generated only at high tide. In addition, both have

only one reservoir. In addition to the traditional dam-

type Tidal energy technology, research institutions in

the United Kingdom, the Netherlands and other

countries have also carried out research on open Tidal

energy development and utilization technology, and

proposed the Tidal Lagoon, Dynamic Tidal Power

and other environmentally friendly new tidal energy

technologies (Liu et al, 2018).

2.4 Existing Problems

At present, the energy conversion efficiency of tidal

power generation equipment is relatively low. This is

mainly because the movement characteristics of tidal

waves are complex and it is difficult to fully convert

them into electricity. In the course of the research,

there are still technical difficulties in the replacement

of advanced materials, the arrangement and

arrangement of power generation equipment,

predictive models and intelligent control. At the same

time, the initial cost of tidal power generation projects

is high, and the maintenance and operation cost of its

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installations and equipment is also high, which limits

the commercial application and promotion of tidal

power generation.

In addition, the development and utilization of

tidal energy will cause damage to Marine ecosystems,

which will have an impact on biodiversity, fisheries

and other fields. For example, the wastewater of the

Swansea Bay Tidal power Station project in the

United Kingdom was discharged into the local

wetland area, resulting in the adverse impact on the

ecosystem of the area, and the biodiversity of the

wetland area was destroyed. During the construction

of the Yukon River Tidal power Station project in the

United States, the sound of the engine of the

construction vessel disturbed the normal behavior of

the surrounding Marine animals, resulting in whales

and dolphins and other animals had to leave the

construction site. Noise from the construction of a

tidal energy project in Queensland, Australia, has

damaged the local Marine ecosystem and disrupted

the generation succession of fish and seabirds, which

has had an impact on local fisheries and birdwatching.

2.5 Application Prospect

At present, there are few commercial tidal power

stations built and put into operation, but tidal energy

still has great development prospects because of its

advantages of stability, reliability, clean and

renewable. Many coastal countries and regions all

have the requirement of building tidal power station.

According to an EU study, there are 106 coasts and

ports in Europe suitable for tidal power stations, and

British offshore turbine research Institute expert

Frank Peter has pointed out that many coasts in Japan,

China, the Philippines and other countries have the

conditions for the construction of tidal power stations

(Yang et al, 2019).

In general, with the gradual attention paid to tidal

power generation technology, more and more experts

and scholars carry out research in this area, Tidal

power station investment construction cost will

become lower and lower, and the power station to

provide power quality will become higher and higher,

and Tidal power generation technology of large-scale

commercial application will be implemented step by

step. Tidal energy will become a part of the future

energy structure and play a valuable role in energy.

3 GEOTHERMAL ENERGY

3.1 Introduction and Development

Status

The Earth's interior is a huge heat source, with

temperatures at its core reaching more than 7,000

degrees Celsius. Geothermal energy is the natural

heat energy extracted by the Earth's crust. This energy

comes from the lava inside the earth and exists in the

form of heat. Geothermal energy is a new

underground energy with wide spatial distribution,

known abundant reserves and safe and reliable

operation.

3.2 Advantages and Disadvantages of

Global Geothermal Energy

At present, hydrothermal shallow geothermal

resources have been partially utilized, but dry thermal

lithologic deep geothermal resources are still in the

exploration stage 。 The whole life cycle of

geothermal energy of hot dry rock is basically divided

into the construction period of underground part, the

construction period of above-ground part, the

operation period and the retirement period. In the

underground part of the construction period, the main

method is to increase the injection pressure (hydraulic

fracturing, hydraulic shear) and reduce the rock

fracture strength (chemical stimulation, thermal

stimulation). The former has low cost of working

medium, but the risk of inducing earthquake is

greater. Although the latter injection pressure is low,

but there is environmental pollution, wellbore damage

(chemical stimulation), time and economic costs are

high (thermal stimulation) and other problems.

Geothermal energy is not affected by environmental

weather, can be exploited at any time, and maintain-

stability is its advantage different from other energy

sources (Qi & Zhang, 2019).

3.3 Geothermal Energy Development

Technology

Enhanced geothermal systems (EGS) are the main

way to obtain underground heat of hot dry rocks, EGS

technology uses "hydraulic stimulation" to enhance

and create the heat available in hot dry rock. The main

principle of the system is: in the dry hot rock, drill a

straight well or injection well, use fracturing fluid and

other large displacement fracturing, high-temperature

rock cold crack. In the case of continuous high

pressure, the fracture continues to extend and increase

Current Situation and Prospect of Tidal Energy and Geothermal Energy

237

with the continuous injection of low temperature

water, forming the artificial thermal storage

disturbance rock. At the same time, production Wells

are constructed near injection Wells to extract high-

temperature water and high-temperature water vapor

(He, 2021). The high-temperature water and water

vapor are finally generated by direct steam method,

expansion method and intermediate medium method,

so as to form a cycle. Because the direct steam method

requires the extraction of high-temperature steam

from the well and is less efficient, it is rarely used. In

the expansion method, hot water in the production

well is first transported to the expansion vessel, and

the steam generated by the decompression and

expansion drives the turbine to generate electricity.

The most widely used is the intermediate medium

cycle, such as the organic Rankine cycle and Carina

cycle. In the whole cycle process of geothermal

energy application, no exhaust gas, waste liquid and

waste are emitted, so the impact on the environment

is very small, and the whole life cycle sustainable

development and utilization is achieved.

3.4 Existing Problems

EGS technology is still immature, and field tests in

several countries and regions have demonstrated the

microseismic risk of hydraulic fracturing methods.

For example, the hot dry rock development in Basel,

Switzerland, triggered four earthquakes of magnitude

3 or greater during the water injection, causing

damage to buildings, forcing the project to be

terminated, leading to a huge investment failure and

numerous legal disputes. In 2017, a hot dry rock

development project in Pohang, South Korea,

triggered a MW5.4 earthquake on a nearby fault and

caused severe economic damage, forcing the South

Korean government to suspend the project's operation

(Yin et al, 2019). The main factor restricting the

development of deep geothermal energy in China,

especially hot dry rock geothermal energy, is the

exploitation technology, especially in the reservoir

transformation and heat transfer, there are still many

scientific and technical problems to be overcome. In

addition to technological immaturity, geothermal

energy development also faces the problem of time

and economic costs. Due to the different geothermal

energy reserves in different places, a lot of

exploration and preliminary preparation are needed to

determine the development field, which greatly

increases the development cost.

3.5 Application Prospect

China is rich in geothermal resources, which are

equivalent to hundreds of billions of tons of coal in

the country's sedimentary basins. It has a broad

development prospect and is widely distributed.

Ground source heat pump is one of the main forces

for future energy structure adjustment and clean

energy development. Geothermal energy is not only

abundant in reserves, but also widely used in various

fields. The ground source heat pump can draw heat

from the underground soil to heat the room through

its own air conditioning system in winter and recharge

heat to cool the room in summer. The ground source

heat pump can realize the transfer of energy from low

temperature heat source to high temperature heat

source by input a small amount of high grade energy

(electric energy). In the Yangtze River Basin of

China, heating in winter and cooling in summer can

be achieved by relying on ground source heat pumps,

which remove heat from the soil in winter and input

heat into the soil in summer. At the same time,

geothermal energy also has biological, medical,

agricultural and other fields of value. Although the

investment cost of geothermal energy development

and application is high in the early stage, the income

from geothermal energy is characterized by

sustainable stability and can be suitable for long-term

investment and development.

4 COMPARISON OF TIDAL

ENERGY AND GEOTHERMAL

ENERGY WITH OTHER

ENERGY SOURCES

4.1 Comparison of Tidal Energy and

Geothermal Energy

Both tidal and geothermal energy rely on the Earth's

internal energy sources, and both are clean, reliable,

and stable sources of non-fossil energy, and both of

them have technical defects and problems of time and

economic cost, which can not be commercialized on

a large scale. In terms of power generation efficiency,

tidal energy is comparable to geothermal energy in

terms of power generation efficiency usually around

20%. However, due to the regularity and stability of

ocean tides, the actual efficiency may be higher.

Geothermal power generation is usually divided into

three types: direct steam method, expansion method,

indirect medium method. Power generation steam is

divided into dry steam generation and flash steam

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power generation. Overall, geothermal power is

between 10 and 30 percent efficient. In terms of

operating cost, the operating cost of tidal energy is

slightly higher than that of geothermal energy, mainly

including equipment maintenance, manual

inspection, and the impact of Marine environment on

equipment. The operating cost of geothermal power

generation equipment is lower than that of tidal

energy, because the fuel source of geothermal energy

is the heat energy inside the earth, and the emission of

pollutants is less, and there is no need to carry out fuel

purchase and pollution treatment costs.

4.2 Comparison with Other Energy

Sources

4.2.1 Comparison of Tidal Energy with

Other Energy Sources

Tidal power generation has a more environmentally

friendly and sustainable life cycle than fossil fuels.

Tidal power produces no greenhouse gases such as

carbon dioxide and is less polluting than conventional

fossil fuels. Compared with renewable energy sources

such as solar and wind, the practical application of

tidal power generation is subject to some limitations,

such as site selection and technology, so more

preparation and investment are required. Among the

subsequent operating costs, the operating cost of tidal

energy is slightly higher than that of other clean

energy sources, mainly including equipment

maintenance, manual inspection, and the impact of

Marine environment on equipment. Energy density:

The energy density of tidal energy is about 0.8Wh/kg,

which is lower than fossil fuels (248,000 Wh/kg) and

nuclear energy (109,000 Wh/kg). For power

generation efficiency, Tidal power is on par with wind

power and slightly less efficient than solar power,

usually around 20 percent. In terms of

commercialization prospects, compared with

traditional energy, tidal energy has a unique

advantage, because of its strong stability and high

reliability characteristics, tidal energy is regarded as

one of the most promising new energy in the future.

Although the current tidal energy technology is not

very mature, commercialization is also facing various

challenges, but its basic research and technology

research and development has been carried out, and

there is also a huge potential of tidal resources, so the

commercial prospect of tidal energy is still very broad

(Malcolm & Gorlov, 2019, Tsai et al, 2014, Kim et al,

2012) .

4.2.2 Comparison Between Geothermal

Energy and Other Energy Sources

For life cycle, compared with fossil fuels, geothermal

energy is cleaner and more reliable, and can achieve

zero or low carbon emissions throughout the life

cycle. For commercial prospects, because of its

reliability and stability, although the early

development and application of geothermal energy

investment cost is high, but geothermal energy

income has the characteristics of sustainable stability,

can be suitable for long-term investment and

development. At present, the commonly used

geothermal power generation technologies include

dry steam power generation and flash evaporation

power. The efficiency of dry steam power generation

is generally between 10% and 23%, while the

efficiency of flash evaporation electricity can reach

20% to 30%. Compared with clean energy such as

solar energy and wind energy, geothermal energy is

not affected by environmental weather, can be

exploited at any time, and remains stable (Qi &

Zhang, 2019). Compared with fossil energy,

geothermal energy has the advantages of pollution-

free and clean emission.

5 CONCLUSION

Coal, oil and natural gas are the traditional energy

sources for human daily survival. With the increasing

shortage of traditional energy sources, tidal energy

and geothermal energy, as clean and efficient new

energy sources, can help alleviate the current energy

pressure and contribute to the goal of carbon peak and

carbon neutrality. The tidal power generation

technology has some defects, such as low collection

efficiency, immature equipment maintenance

technology, high initial construction cost and easy

impact on ecological environment. However, EGS

technology has some problems, such as immature

geothermal reservoir reconstruction technology,

imperfect heat transfer system, low life of technical

tools in extreme environment and easy to cause

earthquake disasters during construction. However,

tidal energy and geothermal energy have the

advantages of continuous resource reserves, low

carbon and efficient renewable and stable operating

mechanism, so there is still a large development space

and commercial prospects. In the future, we should

continue to increase scientific research, improve

production technology and reduce production costs

with the support of the government and the people, so

Current Situation and Prospect of Tidal Energy and Geothermal Energy

239

as to achieve the large-scale and safe application of

the two.

AUTHORS CONTRIBUTIONS

All the authors contributed equally and their names

were listed in alphabetical order.

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