Development and Outlook  
of Clean Energy Power  
Generation Technology  
( B r i e f
 
V
e r s i o n )  
Global Energy Interconnection  
Development and Cooperation Organization  
(GEIDCO)  
Development and Outlook of Clean Energy Power Generation Technology  
PREFACE  
With the continuous reduction in the availability of fossil energy  
along with the increasingly severe climate change situation and  
the increasing accumulation of environmental pollution, higher  
requirements have been put forward for energy reliability,  
environmental protection and sustainable development. Clean  
development is the core of sustainable development, and the key  
to clean development is clean energy power generation  
technology. After years of development, clean energy power  
generation technology has achieved considerable progress.  
Hydropower generation, wind power generation, and  
photovoltaic (PV) power generation technologies are now widely  
applied, and concentrating solar power (CSP) generation,  
geothermal power generation, and ocean power generation also  
present strong development potential. Such advancements and the  
reduction in cost of clean energy power generation is the most  
important driving force for the transition to clean energy and the  
construction of a Global Energy Interconnection.  
This report contains 6 chapters in total to cover the 6 main clean  
energy power generation technologies currently available. Each  
chapter introduces the basic principles of one technology;  
1
Development and Outlook of Clean Energy Power Generation Technology  
summarizes its development status based on the investigation  
results; analyzes the main difficulties that is faced by each  
technology in conjunction with the demands for clean energy  
transition; proposes its development goals and research directions  
in the future through technical and economic research based on  
the assessment of technology readiness; analyzes the main  
technical factors affecting the economic efficiency, and  
determines the trend of changes in the economic efficiency based  
on the development goal by applying the analysis method which  
combines the multiple linear regression method with the deep  
self-learning neural network.  
Global Energy Interconnection is an optimum solution with the  
aim of realizing the optimal allocation of clean energy and  
alleviating complex issues such as the global energy dilemma and  
climate environment. Clean energy power generation technology  
is the foundation for the development of the Global Energy  
Interconnection and has broad development space and application  
prospects. This report, as one of the key technology achievements  
of the Global Energy Interconnection, is intended to enable  
readers to know the current status and key development trends of  
main clean energy power generation technologies, and provide an  
important reference for people inside and outside the industry,  
2
Development and Outlook of Clean Energy Power Generation Technology  
especially policy makers, to fully understand the clean energy  
power generation technologies. Additionally, it is of great  
significance to further consolidate the technical foundation of the  
Global Energy Interconnection, promote the large-scale  
development, global deployment and efficient utilization of clean  
energy, and realize the sustainable development of economies,  
societies and the environment around the world.  
3
Development and Outlook of Clean Energy Power Generation Technology  
CONTENTS  
1.  
2.  
3.  
4.  
5.  
6.  
Hydropower Generation Technology..........................................6  
1.1 Overview.....................................................................................6  
1.2 Key Technologies........................................................................9  
1.3 Development Prospect ..............................................................14  
Wind Power Generation Technology ........................................17  
2.1 Overview ................................................................................17  
2.2 Key Technologies ...................................................................19  
2.3 Development Prospect............................................................24  
Photovoltaic Power Generation Technology ............................27  
3.1 Overview ................................................................................27  
3.2 Key Technologies ...................................................................31  
3.3 Development Prospect............................................................35  
Concentrating Solar Power Generation Technology...............38  
4.1 Overview ................................................................................38  
4.2 Key Technologies ...................................................................41  
4.3 Development Prospect............................................................44  
Geothermal Power Generation Technology .............................47  
5.1 Overview ................................................................................47  
5.2 Key Technologies ...................................................................50  
5.3 Development Prospect............................................................55  
Ocean Energy Power Generation Technology .........................57  
6.1 Overview ................................................................................57  
4
Development and Outlook of Clean Energy Power Generation Technology  
6.2 Key Technologies ...................................................................59  
6.3 Development Prospect............................................................61  
5
Development and Outlook of Clean Energy Power Generation Technology  
1. Hydropower Generation Technology  
Hydropower generation technology is an engineering technology  
that converts the potential energy of water into electrical energy  
through hydropower stations. Hydropower technology boasts the  
advantages of mature technology, economical development,  
flexible dispatch, clean and low-carbon, and high safety and  
reliability, and can also serve for irrigation, flood control,  
shipping and other social tasks. With the increasingly serious  
energy scarcity and environmental pollution, the energy  
development modes based on traditional fossil energy have  
become unsustainable, and the rational development of green and  
low-carbon renewable energy such as hydropower resources and  
the gradual transformation of the energy structure can effectively  
alleviate the energy shortage and contribute to a sustainable  
development.  
1.1 Overview  
Hydropower station is a facility in which the potential energy of  
water flow of rivers and lakes running from a high place is  
converted into the kinetic energy of the hydraulic turbine, and  
then the Hydraulic turbine works as the prime power to drive the  
generator to generate electricity. The schematic diagram of the  
working principle of the hydropower station is as shown in  
6
   
Development and Outlook of Clean Energy Power Generation Technology  
Fig.1.1.  
Fig.1.1 Working Principle of Hydropower Station  
The hydropower generation is characterized by mature  
technology, low cost, renewability, clean and low-carbon, zero  
chemical and thermal pollution, and such operation advantages as  
high mobility and flexibility, and low management cost. The  
hydraulic turbine generator unit is a device that converts the  
potential energy of water into electrical energy. It is generally  
composed of a hydraulic turbine, a generator, a governor, and an  
excitation system.  
Hydraulic turbine is a hydraulic machine that converts the  
energy of water flow into rotating mechanical energy. According  
to the water flow energy conversion mode of the turbine runner,  
it is divided into pelton turbine and reaction turbine. The pelton  
turbine is mainly composed of flow divider, distributor, runner,  
spindle, guide bearing and casing. The reaction turbine is mainly  
composed of spiral case (referred to as the inlet rotor for a tubular  
turbine), stay ring, distributor, runner, spindle, guide bearing and  
7
Development and Outlook of Clean Energy Power Generation Technology  
draft tube. According to the flow line direction of rotor shaft  
surface where the water flow enters, it is divided into Francis  
turbine, diagonal turbine, axial flow turbine and tubular turbine.  
Generator is usually consisted of rotor, stator, frame, guide  
bearing, cooler and other parts. The hydraulic turbine works as its  
prime power to drive its rotor to rotate to convert water energy  
into electrical energy. By stabilizing the speed of the generator  
unit at the synchronous speed, the unit can output electric energy  
that meets the requirements of the grid.  
Governor is mainly intended to adjust the generator frequency  
and active power output. Specially, it adjusts active power output  
of the hydraulic turbine generator unit according to the grid load  
to maintain the speed or frequency of the generator unit within  
the specified range, and effectively guarantee the quality and  
reliability of power supply.  
Excitation system is intended to adjust the generator voltage and  
reactive power, and mainly composed of the excitation power unit  
and the excitation regulator. The excitation power unit provides  
excitation current to the rotor of the synchronous generator, and  
the excitation regulator controls the output of the excitation  
power unit according to the input signal and the given regulation  
criterion, so that the generator rotor can form a stable rotating  
magnetic field.  
8
Development and Outlook of Clean Energy Power Generation Technology  
1.2 Key Technologies  
The key technologies of hydropower generation are mainly  
involved in the following three aspects. (1) Site selection and  
construction of project. The hydropower project is generally  
developed from the easier to the harder, and currently, the sites of  
completed projects or projects under construction are selected in  
areas with better development conditions. In the medium and long  
term, the technical difficulty of development of hydropower  
project will increase, and the key technologies involved include  
high arch dam construction technology under complex terrain and  
geological conditions, flood discharge and energy dissipation  
technology, superlarge underground power station cavern group  
excavation technology, and environment-friendly RCC (Roller  
Compacted Concrete) high- thin arch dam technology, etc. In  
addition to traditional problems including geological topography  
and construction material, the friendliness to local environment  
becomes more important in the project construction as more  
focuses are put on the ecological environment issue, and  
ecological protection and restoration technology have gradually  
become the key to hydropower development. (2) Design and  
manufacture of hydraulic turbine generator unit. To make full  
use of the hydropower resources in a concentrated and efficient  
manner, most of the superlarge hydropower stations are located  
in mountains of higher height, and due to the high operating head  
9
 
Development and Outlook of Clean Energy Power Generation Technology  
and limited layout conditions, the hydropower projects are  
gradually becoming more complex and larger. Correspondingly,  
conventional Hydraulic turbines are developed towards higher  
head and larger capacity, and the improvement and development  
of the design and manufacturing level of superlarge hydropower  
facilities has great significance. On the other hand, with the  
increasing proportion of wind power generation, photovoltaic  
power generation and the power generation by other fluctuating  
energy in the grid, the large-capacity pumped storage power  
stations with rapid regulating capability have gradually become  
an important flexible regulation resource in the grid. In order to  
increase the regulating capacity of the pumped storage generator  
unit, functions such as large head and VFSR are required. (3)  
Operation control of hydropower stations. In order to make full  
use of hydropower, generally more than one hydropower stations  
are arranged in a cascaded manner in the same river basin, and to  
improve the overall benefits of those hydropower stations in the  
basin, it is necessary to implement joint dispatching, unified  
dispatching, and optimized operation dispatching management  
system throughout the basin1 to realize the tacit cooperation of  
cascade hydropower stations and maximize the use of water  
energy. For this purpose, the key is the multi-objective operation  
optimization technology of large-scale river basin cascade  
1
China Electric Power Press. China Hydropower Science and Technology Development  
Report: 2012 Edition [M]. 2013.  
10  
Development and Outlook of Clean Energy Power Generation Technology  
hydropower stations, including the intelligentization,  
modernization and asset digitization of power station  
management system, and the construction of digital hydropower  
stations containing control systems and regional network projects.  
Table1.1 Key Technologies of Hydropower Generation  
11  
Development and Outlook of Clean Energy Power Generation Technology  
Technical  
dimension  
Breakdown  
Key Technologies  
Geophysical exploration technology and  
3D geological modeling technology of  
water conservancy and hydropower  
Geological  
survey  
Fine excavation technology of arch dam  
foundation surface, key technology of  
concrete cut-off wall under ultra-deep  
and complex geological conditions, key  
technology of high arch dam construction  
under complex terrain and geological  
conditions (high arch dam foundation  
treatment technology, dam concrete  
temperature control and cracking  
Dam  
construction  
technology  
prevention technology, ultra-high arch  
dam seismic technology), flood discharge  
and energy dissipation technology,  
underground cavern excavation technology  
for generator unit of 1,000,000 kW,  
environment-friendly RCC high-thin arch  
dam technology, etc.  
Engineering  
construction  
Safety construction technology of high  
and steep slope, geological disaster  
prevention technology, dam intelligent  
construction technology  
Construction  
control  
Water and soil conservation and  
ecological restoration technology:  
surface planting soil protection  
technology, high and steep slope  
Ecological  
protection  
treatment technology, reservoir hydro-  
fluctuation belt treatment technology,  
vegetation restoration technology, etc.  
Fish pass structure layout technology:  
fishway, fish lift, fish lock, etc.  
Large Francis hydraulic turbine  
generator unit and its supporting  
devices  
Hydraulic  
turbine  
generator  
unit  
Equipment  
manufacturing  
VFSR pumped storage generator unit  
Large pelton turbine  
12  
Development and Outlook of Clean Energy Power Generation Technology  
Technical  
dimension  
Breakdown  
Key Technologies  
Geophysical exploration technology and  
3D geological modeling technology of  
water conservancy and hydropower  
Geological  
survey  
Fine excavation technology of arch dam  
foundation surface, key technology of  
concrete cut-off wall under ultra-deep  
and complex geological conditions, key  
technology of high arch dam construction  
under complex terrain and geological  
conditions (high arch dam foundation  
treatment technology, dam concrete  
temperature control and cracking  
Dam  
construction  
technology  
prevention technology, ultra-high arch  
dam seismic technology), flood discharge  
and energy dissipation technology,  
underground cavern excavation technology  
for generator unit of 1,000,000 kW,  
environment-friendly RCC high-thin arch  
dam technology, etc.  
Engineering  
construction  
Safety construction technology of high  
and steep slope, geological disaster  
prevention technology, dam intelligent  
construction technology  
Construction  
control  
Water and soil conservation and  
ecological restoration technology:  
surface planting soil protection  
technology, high and steep slope  
Ecological  
protection  
treatment technology, reservoir hydro-  
fluctuation belt treatment technology,  
vegetation restoration technology, etc.  
Fish pass structure layout technology:  
fishway, fish lift, fish lock, etc.  
Multi-objective operation optimization  
technology of large-scale cascade  
hydropower stations  
Operation  
Joint  
monitoring  
dispatching  
13  
Development and Outlook of Clean Energy Power Generation Technology  
1.3 Development Prospect  
The hydropower generation technology and facilities have  
matured after more than one hundred years of development and  
global application. Currently, the world's largest Francis turbine  
has a unit capacity of up to 770MW, and the Baihetan  
Hydropower Project which adopts the Francis turbine with a unit  
capacity of 1,000MW is now under construction; the variable  
frequency speed regulation (VFSR) pumped storage generator  
unit has a maximum unit capacity of 480MW, a maximum head  
of 778m, and a highest speed of 500r/min. The pelton turbine  
generator unit has a maximum unit capacity of 423.13MW and a  
highest water head up to 1,869m. Hydropower generation enjoys  
a favorable economic efficiency, and the LCOE of hydropower  
generation is currently maintained worldwide within 4-6  
cents/kWh.  
The key technologies involved in the hydropower generation  
include site selection and construction, the design and  
manufacture of wind turbine generator units and the operation  
control of hydropower plants. With the further and deeper  
development of hydropower resources globally, the focus in the  
future will be on the design, development and manufacture of the  
most widely-applied large-size Francis turbine, the pelton turbine  
for the development of high head hydropower resources and the  
VFSR pumped storage generator unit for peak load regulating of  
14  
 
Development and Outlook of Clean Energy Power Generation Technology  
power system. The key issues to be tackled are the design and  
stability research of hydropower generation technology,  
electromagnetic design and structure optimization, thrust bearing  
manufacturing and the control of hydraulic turbine generator  
units. Based on the technological advancement, it is envisaged  
that by 2050, the large-size Francis turbine will embrace a unit  
installed capacity of 1,500MW with a maximum head of 800m;  
the pelton turbine generator unit will realize a stand-alone  
capacity of 800MW and a maximum head of 2,200m; the VFSR  
pumped storage generator unit will achieve a unit installed  
capacity of 750MW, with a maximum head of 1,000m and a  
rotation speed of 700r/min.  
Fig.1.2 Key Technologies Developing Target of Hydro-turbine  
Although there may be slight fluctuations and regional  
differences in global LCOE due to the improvement of  
technology, the reduction of facility costs and the increasingly  
complex hydropower resource development conditions, it will  
generally be stably maintained within 4-6 cents/kWh. For some  
projects featuring abundant resources and low non-technology  
investment, for example, the Inga Power Plant on the Congo  
15  
Development and Outlook of Clean Energy Power Generation Technology  
River, the LCOE is expected to be reduced to 3-3.5 cents/kWh.  
Fig.1.3 Chart for Predicated Trend of Global Hydropower Project LCOE  
16  
 
Development and Outlook of Clean Energy Power Generation Technology  
2. Wind Power Generation Technology  
Wind power technology is a technology that converts the kinetic  
energy of the wind into electrical energy through a wind turbine.  
At present, wind power generation is the most mature, largest-  
scale, and highly commercialized renewable energy power  
generation technology, and it is also one of the key clean  
alternative technologies for coping with resource scarcity,  
environmental pollution, and climate change.  
2.1 Overview  
The wind turbine generator works with a wind turbine which  
rotates under the influence of wind to convert the kinetic energy  
of the wind into mechanical energy, and then drives the generator  
to convert the mechanical energy into electrical energy.  
A wind turbine generator is mainly composed of blade, hub, gear  
box, nacelle, tower, base （foundation ）and box transformer  
substation, with the nacelle housing generator, frequency  
converter, wind measurement system, yaw motor and pitch  
control systems etc., as shown in Fig.2.1.  
Wind turbine is a key component for capturing wind energy, and  
it consists of blades, a hub, and a pitch control system in the hub.  
Nacelle includes gear box, generator, converter, yaw control  
system, anemometer, etc. Generator converts the mechanical  
energy of the wind turbine into electrical energy. The converter  
17  
 
Development and Outlook of Clean Energy Power Generation Technology  
controls the rotor speed to achieve maximum power point tracking  
on one hand, and converts the electrical energy into 50 Hz three-  
phase AC current on the other hand to achieve grid integration.  
Tower is a steel cone-shaped cylinder housed with upward and  
downward channels and working platform. Base is a reinforced  
concrete structure with a pre-embedded foundation ring, which is  
connected to the tower with high-strength bolts for securing the  
wind turbine generator and embedded with the grounding system.  
Yaw control system generally includes wind vane that senses the  
wind direction, yaw motor, yaw planetary gear reducer, yaw brake  
(yaw damper or yaw caliper) and rotator gearwheel, etc. When the  
wind direction changes, the two steering wheels (its rotation plane  
is perpendicular to the rotation plane of the wind turbine) rotate to  
deflect the wind turbine through a geared transmission system,  
and when the wind turbine is realigned to the wind direction, the  
steering wheel stops and the wind direction alignment process  
ends.  
Pitch system mainly includes drive motor, gear box and variable  
pitch bearing. The pitch drive motor installed between the blade  
and the hub drives the slewing bearing to rotate, thereby changing  
the blade angle of attack and controlling the lift of the blade to  
18  
Development and Outlook of Clean Energy Power Generation Technology  
control the torque and power acting on the blade. When the wind  
speed is lower than the rating, the maximum power tracking is  
achieved by adjusting the blade angle; when the wind speed is  
greater than the rating, the blade angle is adjusted to maintain the  
speed and power to the optimal level.  
Fig.2.1 Structure of Wind Turbine Generator  
2.2 Key Technologies  
The key technologies involved in the wind power generation  
include:  
(1)Research and development of wind turbine generator. The wind  
turbine generator system is mainly composed of blade, tower,  
19  
 
Development and Outlook of Clean Energy Power Generation Technology  
foundation, generator, converter and control systems (yaw control  
system, pitch control system, etc.). The development goal of wind  
turbine generator technology is to reduce costs, and improve  
reliability and power generation efficiency. An effective way for  
this is upsizing of wind turbine generator. Arotor of large diameter  
and high hub strength, though increasing the initial investment  
and unit power cost, improves the power generation capacity,  
reduces the LCOE, ensures better use of wind resources and  
reduces power output fluctuation.  
(2) Construction, control and O&M technology of wind farm. The  
offshore area features abundant wind resource, high wind speed  
and low wind speed fluctuation, and the site of wind farm is now  
extending from onshore to offshore. However, the special natural  
environment offshore (sea breeze, sea waves) is very complex and  
puts forward new requirements for wind turbine load analysis,  
wind turbine component transportation, and wind turbine hoisting.  
A wind farm is composed of multiple independent wind turbine  
generators, and those generators are different from each other in  
status and characteristics. Therefore, the overall O&M  
management and optimization control of the wind farm are more  
complicated. With the development of technologies such as big  
data and cloud computing, the operation and maintenance of wind  
20  
Development and Outlook of Clean Energy Power Generation Technology  
farms is developing towards digitization and intelligence with a  
goal to achieve optimized control of wind power, reduce failure  
rates, and increase power generation capacity.  
(3) Grid-source coordination technology. Wind power is a  
fluctuating energy source, and its power fluctuation will affect the  
frequency and voltage of the grid. The wind farm is connected to  
the power grid through power electronic devices, which will cause  
the rotation inertia of the grid, and poses risks of subsynchronous  
resonance; besides, power electronic devices are sensitive to the  
disturbance of the grid, and any failure will cause large-scale grid  
disconnection of wind farm. The key technologies for friendly  
grid integration of wind farms mainly include wind farm reactive  
voltage control, virtual inertia control, fault ride-through,  
subsynchronous resonance suppression, etc. The development  
goal is to minimize the impact of wind power grid integration on  
the security and stability of the grid.  
(4) Fine modeling of wind farm power generation capacity and  
evaluation technology of system consumption capacity. With an  
increasing penetration rate and an increasingly complex power  
grid structure, minimizing the uncertainty of power generation  
capacity and system consumption capacity becomes particularly  
important, which includes correction and verification of power  
21  
Development and Outlook of Clean Energy Power Generation Technology  
generation capacity model with measured data to adapt to seasonal  
and annual fluctuation and change of wind source; optimization  
of micro-site selection methods to minimize the impact of wakes;  
study of evaluation method for economy of complementarity of  
multiple renewable energy sources and energy storage & power  
generation combination; study of analysis model for system  
consumption capacity of higher time resolution with  
interconnection of different regions considered.  
Table2.1 Key Technologies for Wind turbine Generators and Wind Farms  
Component  
Key Technologies  
Blade  
Enlargement, light-weight, segmented  
technology, optimized design  
Gearbox  
Tower  
Connection method with main shaft and  
motor, fixing method, compact design,  
load capacity improvement; lubrication &  
cooling system  
New steel material, coating, segmented  
technology  
Foundation Design of floating foundation for  
offshore wind power generator, corrosion  
protection of anchor bolts, concrete and  
reinforcement consumption reduction,  
basement soil treatment methods  
Wind turbine  
generator  
body  
Generator  
Converter  
Oversizing, light-weight  
Large capacity converter, overcurrent and  
overvoltage protection, intelligent  
control  
Yaw control Optimal control under overall load and  
system  
hardware constraints, yaw control under  
complex terrain and complex wind  
conditions  
22  
Development and Outlook of Clean Energy Power Generation Technology  
Pitch  
control  
system  
Downsizing of pitch gear drive system,  
lightning protection device, and control  
strategy for grid faults and extreme  
weather  
Antifreeze Antifreeze material, physical heating,  
system intelligent protection  
Anti-typhoon Reasonable site selection, anti-typhoon  
technology design of foundation, tower and blade,  
design of pitch and yaw control systems  
for sudden changes in wind speed  
Construction From onshore to offshore  
Coordinated Optimized layout, on-farm reactive power  
control  
optimization, on-farm loss optimization,  
and relay protection  
Wind farm  
Operation  
and  
Intelligentialization and digitalization,  
optimized control, troubleshooting  
maintenance  
Grid  
Reactive power compensation, frequency  
integration fluctuation, fault ride-through, virtual  
inertia, subsynchronous resonance, power  
prediction, wind power dispatch, wind  
farm equivalent modeling, DC grid-  
connection technology, offshore converter  
station  
Grid-source  
coordination  
Power Correction and verification of power  
generation generation capacity model, and micro-site  
capacity  
Power  
selection methods to minimize the impact  
of wake current.  
Power  
generation  
and  
Evaluation method for economy of  
consumption complementarity of multiple renewable  
consumption  
capacity  
capacity  
energy sources and energy storage & power  
generation combination, analysis model  
for system consumption capacity of higher  
time resolution with interconnection of  
different regions considered.  
23  
Development and Outlook of Clean Energy Power Generation Technology  
2.3 Development Prospect  
After decades of development, the wind power generation  
technologies and facilities have matured. At present, onshore wind  
turbine generator units and offshore wind turbine generator units  
have an average unit capacity of 2.6MW and 5.5MW respectively,  
and an average turbine diameter of 110.4m and 148m respectively.  
Amongst all of the currently available new energy power  
generation technologies, wind power generation is the most  
economical, with the LCOEs of onshore wind power generation  
and offshore wind power generation down to 4.7 cents/kWh and  
7.8 cents/kWh respectively.  
There are two key aspects involved in wind power generation. The  
first is the research and development of technology for wind  
turbine generator units. It is expected that, to improve the power  
generation efficiency, wind turbine generator units will become  
larger and larger, placing the upsizing issue of turbine blades in  
the critical position The design of the blade structure, the design  
of the blade tip velocity, materials and the segmented blade  
technology are crucial for addressing the issue of upsizing turbine  
blades.. The second aspect is the construction, grid integration and  
O&M control technology of wind power plants. Considering that  
the wind speed in offshore and polar regions is higher with smaller  
24  
 
Development and Outlook of Clean Energy Power Generation Technology  
fluctuations, and in order to improve wind power development  
efficiency and save land resources, the site of wind power plants  
is now extending from onshore to offshore and polar regions. The  
key to the development of offshore wind power is the  
improvement of the wind turbine foundation technology, and for  
this, the important issues to be tackled for the foundation of  
offshore wind turbine generator units include the structure  
selection and structure modal analysis of foundations, pile  
foundation design, load calculation and fatigue analysis of  
foundations. The key to the development of polar wind power is  
the low temperature operation technology, the important issues to  
be tackled for this include the research and development of low  
temperature resistant blades, the selection of low temperature  
resistant oil and sealing materials and blade de-icing technology  
amongst other technologies.  
Fig.2.2 Key Technologies Developing Target of Wind Turbine  
It is predicted that, by 2050, the onshore wind turbine generator  
units and offshore wind turbine generator units will embrace a unit  
25  
Development and Outlook of Clean Energy Power Generation Technology  
capacity above 12MW and 20MW respectively, with an average  
turbine diameter of up to 220m and 250m respectively. Based on  
the increasing turbine efficiency resulting from turbine upsizing,  
the reduction of O&M cost and the further development of  
offshore/polar wind power , it is expected that by 2050, the  
LCOEs of onshore wind power generation and offshore wind  
power generation will drop down to 2.6 cents/kWh and 5.5  
cents/kWh respectively.  
(a)Onshore  
(b) Offshore  
Fig.2.3 LCOE Predication of Onshore and Offhsore Wind Power  
26  
 
Development and Outlook of Clean Energy Power Generation Technology  
3. Photovoltaic Power Generation Technology  
Photovoltaic power generation technology is a technology that  
converts the solar energy directly into electrical energy by using  
the photovoltaic effect of semiconductors. Photovoltaic power  
generation is less subject to geographical restrictions, and is safe,  
reliable, noiseless and less polluting, with zero fuel consumption  
and short construction period, and thus it has great development  
potential.  
3.1 Overview  
The photovoltaic power generation system is mainly composed  
of photovoltaic cells and their components (or arrays), inverters,  
step-up transformers, and auxiliary facilities for measurement,  
data acquisition and other purposes (错误!未找到引用源。).  
Fig.3.1 Composition of Solar Photovoltaic Power Generation System  
1) Photovoltaic cells and modules  
Photovoltaic cell is the basis and core of the photovoltaic power  
27  
 
Development and Outlook of Clean Energy Power Generation Technology  
generation system, which can directly convert solar energy into  
electrical energy. Now, commercially available solar cells mainly  
include crystalline silicon cells and thin-film solar cells.  
Photovoltaic cells are generally not used directly as power  
sources due to the following reasons: first, the cell is made of  
monocrystalline silicon or multicrystalline silicon, and is thin  
(about 0.2mm thick) and fragile, and cannot withstand large  
impacts; second, the photovoltaic cell electrodes, through the  
moisture resistance and corrosion resistance are improved due to  
the improvement of material property and manufacturing process,  
cannot meet the needs of long-term exposure during use; third, the  
voltage and current output of single silicon cells are determined  
by the property of silicon material and the light condition, and are  
generally incompatible with the requirements of general electrical  
equipment. Therefore, in actual use, the single cells are usually  
combined in series and parallel to form a photovoltaic module.  
Photovoltaic modules are composed of single photovoltaic cells,  
toughened  
glass,  
backsheet,  
encapsulating  
material,  
interconnecting bars, busbars and aluminum alloy frames.  
Toughened glass is installed on the outermost layer of the module  
to protect the photovoltaic cells. Backsheet is installed on the  
back of the photovoltaic module mainly for protecting and  
28  
Development and Outlook of Clean Energy Power Generation Technology  
supporting the solar cells. At present, the most commonly used  
backsheet in the photovoltaic industry is the TPT backsheet.  
Encapsulating material is used for bonding photovoltaic cells,  
copper tin welding strip, backsheet and photovoltaic glass  
together, and the most widely used encapsulation is EVA film.  
The quality of the transparent EVA film directly affects the life of  
the module. The EVA exposed to the air is prone to aging,  
affecting the light transmittance of the module and thereby the  
power generation capacity of the module. Interconnection bar and  
busbar are used for circuit connection and current collection,  
which is a copper substrate wrapped with tin-lead alloy plating,  
and also called tin-coated copper ribbon.  
Fig.3.2 Photovoltaic Modules  
Photovoltaic array is a DC power generation unit which is  
composed of a series of photovoltaic modules assembled together  
mechanically and electrically and has a fixed supporting structure.  
29  
Development and Outlook of Clean Energy Power Generation Technology  
The photovoltaic arrays are classified into fixed type and  
automatic tracking type according to the availability of automatic  
solar tracking capability.  
Fig.3.3 Photovoltaic Module and Photovoltaic Array  
2) Inverter  
In addition to the efficiency of photovoltaic modules, the power  
generation efficiency of photovoltaic system is also affected by  
the conversion efficiency of the inverter system, and thus the  
important goal of photovoltaic power station design is to improve  
the conversion efficiency of the inverter system. Inverters are  
usually used to convert the DC electricity from photovoltaic  
modules (or arrays) into AC electricity. The currently maximum  
available conversion efficiency of inverter is 99%, and  
conversion efficiency of the grid-connected inverter is more than  
30  
Development and Outlook of Clean Energy Power Generation Technology  
98.5%. The research on the inverter itself has been improved.  
However, the selection of inverter is based on full power, and at  
a lower power, the high-power elements in the inverter will cause  
excessive power loss. Photovoltaic power generation capacity is  
affected by weather and sunlight, and operating losses will be  
inevitable in low light conditions. The commonly-used inverters  
at present mainly include centralized inverter, series inverter and  
distributed inverters.  
3.2 Key Technologies  
The key technologies involved in the solar photovoltaic power  
generation include: (1) Photovoltaic cell manufacturing related  
technology. For crystalline silicon cells, the key technologies  
include surface texturing technology, anti-reflection film  
technology, back contact technology, gettering and passivation  
technology, screen printing, electroplating, laser transfer, and film  
spraying technology to reduce optical loss, carrier-recombination  
loss and series-shunt resistance loss to improve the conversion  
efficiency; for thin film cells, key technologies include: (1)  
Further optimization of the preparation technology of CdTe cell  
absorber, and adjustment of CdS layer structure, etc.; (2) defect  
passivation of module absorber, adjustment of band gap,  
replacement of cadmium-free materials for barrier layer,  
31  
 
Development and Outlook of Clean Energy Power Generation Technology  
adjustment of large-area uniformity, and research on the  
preparation process of CIGS cell on flexible substrate of CIGS  
cell. In addition, through the laminated preparation of multiple  
PN junctions with different band gaps in silicon cells and thin film  
cells, the solar spectrum range that can be absorbed is expandable,  
and a breakthrough in the theoretical efficiency of a single PN  
junction is achieved.  
(2) Photovoltaic power station O&M technology. With the  
scale expansion of photovoltaic power stations, the increasing  
quantity of photovoltaic modules, improving the overall  
efficiency of the photovoltaic power station and reducing its  
power loss become the key technologies for the operation of a  
photovoltaic power station. The main factors affecting the overall  
power generation efficiency of photovoltaic power stations  
include temperature coefficient, dust and shading, module  
matching, inverter efficiency and power transmission loss. The  
key technologies to solve these problems include high-efficiency/  
high-reliability high-power DC/DC converter; automatic solar  
tracking technology; refined design of power station layout,  
series matching, equipment selection, etc.; power station  
automated O&M technology (including anhydrous automatic  
32  
Development and Outlook of Clean Energy Power Generation Technology  
cleaning robot, expert fault diagnosis system) etc.2  
(3) Improvement of the adaptability of photovoltaic power  
stations in extreme environments. The regions with the most  
abundant solar energy resources in the world are mainly located  
in the deserts, Gobi, plateau and other areas with relatively harsh  
natural environments, and the extreme environments in these  
regions, such as extremely low temperature, strong wind, high  
radiation, and excessive dust, put forward high requirements for  
the performance of photovoltaic modules and the O&M of power  
stations. The key technologies to improve the performance of  
photovoltaic modules in extreme environments mainly include  
improvement of strength of protective glass, and adjustment of  
photovoltaic glass density and transmittance; improvement of  
chemical stability, viscosity and low temperature resistance of  
encapsulating material (EVA, PVB etc.), and enhancement of  
mechanical strength, toughness and aging resistance of backsheet.  
(4) Grid-source coordination technology. The photovoltaic  
power generation is quite different from traditional power  
generation technologies such as thermal power and hydropower.  
For example, photovoltaic power generation is volatile and  
intermittent due to the influence of light; the grid integration of  
large-scale photovoltaic power station will affect the voltage and  
frequency of the grid; photovoltaic modules is connected to the  
2China Association for Science and Technology. 2014-2015 Power and Electrical Engineering  
Discipline Development Report [M]. China Science and Technology Press, 2015.  
33  
Development and Outlook of Clean Energy Power Generation Technology  
grid by power electronic devices which will reduce the moment  
of inertia of the power grid; power electronic devices are more  
sensitive to the disturbance of the power grid, and is more likely  
to cause large-scale photovoltaic disconnection under a fault. In  
addition, the rapid development of distributed photovoltaic  
generation projects will have a certain impact on the operation  
analysis, load predication and dispatching of power grid.  
Research on grid-connection friendly technologies for  
photovoltaic power stations is the key to grid-source coordination,  
which include power prediction, virtual inertia control, reactive  
power compensation, and fault ride-through. The key  
technologies in the field of photovoltaic power generation are as  
shown below in 错误!未找到引用源。.  
Table3.1 Key Technologies in Photovoltaic Power Generation  
Classification  
Component  
Key Technologies  
Texturing technology, anti-  
reflection film technology,  
back contact technology,  
aluminum back surface  
technology, gettering and  
passivation technology,  
screen printing,  
Crystalline  
silicon  
cell  
Improve the  
conversion  
efficiency of  
photovoltaic  
cells  
electroplating, laser  
transfer, and spraying  
Photovoltaic  
cell  
CdS layer structure  
adjustment, absorber defect  
passivation, band gap  
Thin film  
cell  
adjustment, cadmium-free  
material replacement, CIGS  
cell preparation technology  
on flexible substrates,  
34  
Development and Outlook of Clean Energy Power Generation Technology  
multi-PN junction lamination  
preparation technology  
High-efficiency/ high-  
reliability high-power DC/DC  
converter, automatic solar  
tracking device, refined  
design, power station  
Improve the operation  
capacity of photovoltaic  
power stations  
automated O&M technology  
Improve density and reduce  
the transmittance of solar  
photovoltaic glass; improve  
the chemical stability,  
viscosity degree and low  
temperature performance of  
encapsulating material (EVA  
film); enhance the  
Improve the performance  
of photovoltaic power  
stations in extreme  
environments  
Photovoltaic  
power  
generation  
system  
mechanical strength,  
toughness and aging  
resistance of backsheet  
Reactive power compensation,  
frequency fluctuation, fault  
ride-through, virtual  
Grid-connected operation  
inertia, subsynchronous  
resonance, short-circuit  
current, power prediction,  
solar power dispatching  
3.3 Development Prospect  
The solar photovoltaic power generation technology has more  
than 160 years of development history, and since the mid-1950s,  
the materials for photovoltaic cell panels has been improved  
rapidly, and the solar photovoltaic power generation technology  
and facilities have matured. At present, the conversion efficiency  
of crystalline silicon photovoltaic cells and thin film cells reach  
24.4% and 19.2% respectively. Over the past 10 years, the LCOE  
35  
 
Development and Outlook of Clean Energy Power Generation Technology  
of solar photovoltaic power generation technology has been  
greatly reduced, and now stands at about 4.6 cents/kWh.  
There are two key technologies involved in solar photovoltaic  
power generation. The first technology is the research and  
development of photovoltaic cells, the key is to improve the  
conversion efficiency For this, the important issues to be tackled  
include the reduction of optical loss, carrier-recombination loss  
and series-shunt resistance, and the key to break through the  
efficiency limit of the single-junction cell is to develop new  
multi-PN junction tandem cells. The second technology is the PV  
module related technologies, the key with this is to improve the  
performance and life of PV modules in severe environments  
such as those with extremely low temperatures/strong radiation  
environment, and for this, the important issues to be tackled  
include the improvement of photovoltaic glass density and  
transmittance, the improvement of chemical stability, viscosity  
and low temperature resistance of encapsulating material (EVA  
film), and the enhancement of mechanical strength, toughness  
and aging resistance of backsheet.  
36  
Development and Outlook of Clean Energy Power Generation Technology  
Fig.3.4 Key Technologies Developing Target of PV  
By 2050, it is envisaged that the conversion efficiency of  
crystalline silicon photovoltaic cells, the CIGS thin film cells and  
the new multi-PN cells will be increased to 27%, 25% and 35%  
respectively. Based on the breakthrough of cell material  
technology and improvement of the manufacturing process, it is  
also expected that by 2050, the LCOE for scale development of  
solar photovoltaic power generation will fall to 1.5 cents/kWh,  
and for some areas with abundant resources and low non-  
technology investment, it may be reduced to 1 cent/kWh.  
Fig. 3.5 Predication of LCOE of Photovoltaic Power Stations  
37  
 
Development and Outlook of Clean Energy Power Generation Technology  
4. Concentrating Solar Power Generation Technology  
Concentrating solar power (CSP) technology is another common  
solar power generation technology in addition to photovoltaic  
power generation technology. This technology works to collect  
solar energy by reflecting sunlight to the collector, and then  
generate high-pressure superheated steam through the heat  
exchanger to drive the steam turbine to generate electricity,  
realizing the conversion of “light - heat - electricity”. In order to  
cope with the intermittency and volatility of solar energy, CSP  
stations are generally equipped with heat storage subsystems to  
ensure a stable power supply.  
4.1 Overview  
CSP plants usually consists of three subsystems, namely  
concentrating and heat collecting link, heat transfer and storage  
link, and power generation link, with the energy transfer between  
each link realized through the heat transfer medium, as shown in  
Fig. 4.1 (take parabolic trough CSP station as an example). The  
concentrating link converges the sunlight to the solar energy  
collection device through a mirror, and then heats the heat transfer  
medium in the collection device; the heat transfer medium enters  
the power generation link and then heats the water to form  
superheated steam to drive the generator to generate electricity;  
38  
 
Development and Outlook of Clean Energy Power Generation Technology  
the heat transfer medium can also flow into the heat storage  
device for heat exchange to realize heat storage or heat release.  
Fig.4.1 Composition of CSP System  
Heat Collecting link, which is usually composed of a  
concentrating field and a heat absorber, collects solar radiation  
and converts it into thermalenergy. At present, the concentrating  
link of CSP plants mainly has 4 technical forms: Parabolic trough  
type, tower type, dish type and Fresnel type. The heat transfer  
medium may be water/steam, mineral oil or molten salt. For early  
CSP plants without heat storage system, the water/steam is  
usually used as the heat transfer medium to directly drive the  
steam turbine, reducing heat exchange link.  
Heat transfer and storage link is a subsystem used to transfer,  
store and release thermal energy. When the solar radiation is  
strong, part of the heat collected in the heat collecting link heats  
39  
Development and Outlook of Clean Energy Power Generation Technology  
the water into superheated steam through heat exchanger to drive  
the steam turbine to generate electricity; the other part is surplus  
heat which is stored and released when the solar radiation is  
insufficient, which can effectively stabilize the intermittent solar  
radiation and increase the power generation time of the CSP plant.  
The technologies available for heat transfer and storage medium  
include sensible heat storage, phase change thermal storage, and  
chemical heat storage. At present, the mature heat transfer and  
storage media include mineral oil, molten salt, and quartzite,  
which have a higher heat transfer and storage efficiency than  
water/ steam. The heat storage container can be divided into  
single-tank type and dual-tank type. In the single-tank  
configuration, the cold and hot heat storage media are stored in  
the same container, and the heat insulation is realized through the  
movable barrier or the temperature transition layer of the heat  
storage medium. In the dual-tank configuration, the cold and hot  
heat storage media are stored in two different tanks and can be  
independently controlled.  
Power generation link converts the collected thermal energy into  
electrical energy through an energy conversion device. Except for  
dish CSP plants that generally use Stirling engines, the power  
generation links of other types of CSP plant are basically the same  
40  
Development and Outlook of Clean Energy Power Generation Technology  
as conventional thermal power plants, and then the heat  
exchanger heats the water into superheated steam to drive the  
Rankine cycle generator to generate electricity.  
4.2 Key Technologies  
The key technologies involved in CSP include:  
(1) Improvement of performance of CSP equipment. The CSP  
system contains many kinds of equipment, mainly including  
collector field equipment (such as the receiver tube of parabolic  
trough CSP station, heliostat of solar power tower station), power  
generation system equipment and heat storage system equipment.  
For the concentrating link, the key technologies include various  
technologies to improve the concentration ratio of the  
concentrating equipment, such as the design and manufacturing  
of the parabolic condenser of parabolic trough CSP station, and  
the solar tracking technology of the heliostat of the solar power  
tower station to improve solar energy collection efficiency;  
design and manufacturing technology of high-performance  
collectors, including glass and metal encapsulating material of  
vacuum collector tubes of parabolic trough CSP station, vacuum  
maintenance and selectively absorbent thin film preparation  
technology etc., to reduce losses in the heat collection process;  
research and development of high-performance heat transfer  
41  
 
Development and Outlook of Clean Energy Power Generation Technology  
medium and supporting technologies to increase the temperature  
of the heat transfer medium and improve the thermoelectric  
conversion efficiency of the system.  
For the heat storage link, the key technology is the development  
and application of new heat storage media to enhance the heat  
storage capacity of the CSP plant and improve the utilization  
efficiency and flexibility of the power plant. The technologies  
involved in sensible heat storage include molten salt steam  
generator design, and optimized design control of molten salt  
pumps and heat storage system etc.; large-scale preparation  
processes for solid heat storage materials such as concrete and  
ceramics. The technologies involved in latent heat storage include  
manufacturing technology of high-performance phase change  
materials such as paraffin wax, organic alcohols and molten salt,  
high-reliability sensible heat - latent heat composite heat storage  
technology, latent heat storage unit and heat storage system  
coordination optimization technology, latent heat storage system-  
level control technology, etc. The technologies involved in  
chemical heat storage includes research of chemical reactions  
with engineering application potential, efficient chemical reactor  
and chemical heat storage system design technology, system  
integration technology, etc.  
42  
Development and Outlook of Clean Energy Power Generation Technology  
For the power generation link, key technologies include the  
design and manufacturing technology of small efficient Stirling  
generators, and the design, manufacturing, and optimized control  
technology of Brayton cycle generators using supercritical CO₂  
as the medium.  
(2) Optimized control and O&M technology of CSP plants. The  
CSP plant involves many links, and their coordination,  
cooperation and optimization strategies are complicated, and  
generally after long-term trial operation and continuous  
correction the better operating results can be achieved; besides,  
each link has many equipment, and they are different from each  
other in characteristics, and thus higher requirements are  
proposed for the operation and maintenance of each equipment.  
Optimized control and O&M technology of CSP plants are  
essential to improve the power generation efficiency of power  
plants. For example, the coordinated and optimized control  
technology of massive heliostats in solar power tower stations can  
ensure that the temperature of the collectors is within a reasonable  
range; in special environments, key technologies related to wind  
and sand resistance of CSP plants and the system thermal  
insulation capacity shall be improved.  
43  
Development and Outlook of Clean Energy Power Generation Technology  
Table4.1 Key technologies of CSP  
Classification  
Link  
Key Technologies  
High-performance trough collector  
design and manufacturing, trough  
vacuum collector tube glass and metal  
Concentrating encapsulation, vacuum maintenance and  
link  
selectively absorbent thin film  
preparation technology, new heat  
transfer medium and supporting  
technologies, etc.  
CSP equipment  
Research and development of new heat  
storage medium, optimized control of  
heat storage system, etc.  
Heat storage  
system  
Stirling generator design and  
manufacturing, supercritical CO₂  
Brayton cycle power generation  
technology  
Power  
generation  
link  
Precision control technology of  
heliostat field in tower power plant,  
new tracking technology  
Control  
System  
optimized  
control and  
O&M  
Wind and sand resistance technology,  
system heat preservation technology,  
mirror field automatic cleaning  
technology  
Operation and  
maintenance  
4.3 Development Prospect  
Since the oil crisis of the 1970s, solar power generation  
technology has become a research hotspot After decades of  
development, the parabolic trough solar power generation  
systems and solar power tower systems have been applied  
worldwide for commercial purposes (the Parabolic through solar  
power generation system mainly applies the water or heat transfer  
oil as the heat transfer medium, and the system operating  
44  
 
Development and Outlook of Clean Energy Power Generation Technology  
temperature is 230~430 ℃; the solar power tower system  
applies the molten salt as heat transfer medium, and the system  
operating temperature is 375~565℃). The solar dish thermal  
power system and linear Fresnel reflector solar power system are  
still at the engineering demonstration stage. Currently, the LCOE  
of concentrating solar power plant is relatively high at about 19  
cents/kWh.  
Involved in the concentrating solar power generation are two key  
technologies. The first is the improvement of the solar thermal  
conversion efficiency, with the key to improve the concentration  
ratio of the collector field. The important issues to be tackled for  
this include the improvement and innovation of mirror and  
tracking method of the collector field. The second technology is  
the improvement of thermoelectric conversion efficiency, the key  
is to develop and select the heat transfer medium of higher  
performance and improve the system operating temperature, for  
this, the important issue to be tackled is the development of new  
heat transfer mediums such as silicon oil, liquid metal, solid  
particle and hot air, and the application of new power generation  
technologies such as supercritical CO2 Brayton cycle.  
45  
Development and Outlook of Clean Energy Power Generation Technology  
Fig.4.2 Key Technologies Developing Target of CSP  
It is envisaged that the heat transfer medium with higher heat  
transfer efficiency and higher heat capacity ratio will be used by  
2050, and the system operating temperature will be increased to  
between 800~1,100℃. Though the concentrating solar power  
generation faces a series of challenges such as complicated  
system construction, severe site selection requirements and  
thermoelectric conversion limitations, it is predicted that by 2050,  
the LCOE of concentrating solar power generation will be  
lowered down to 5.3 cents/kWh due to the increase of  
concentrating solar power plant efficiency and the improvement  
of facilities and industry chains, which, however, is still very high  
when compared with other technologies. In the future, the CSP +  
photovoltaic combined development mode in the power  
transmission scenario of pure solar power generation bases  
integrates the low cost feature of photovoltaic power generation  
technology and the adjustment ability of concentrating solar  
power generation technology, and thus such mode enjoys good  
development prospects.  
Fig.4.3 Predication of CSP LCOE  
46  
 
Development and Outlook of Clean Energy Power Generation Technology  
5. Geothermal Power Generation Technology  
5.1 Overview  
The geothermal resources used for power generation can be  
classified into hydrothermal type and hot dry type rock  
geothermal resources based on geothermal resource carriers.  
Hydrothermal type geothermal energy generally refers to  
geothermal resources consisting of steam, liquid water or steam-  
water mixture, with temperature of 90~200 ℃ in general.  
Hydrothermal type geothermal resources can be classified into  
dry steam, wet steam and geothermal water. The carrier of hot  
dry rock geothermal energy is high-temperature rock mass that  
contains no water or little water and has a temperature higher than  
200℃ in general.  
Table5.1 Classification of Geothermal Resources  
Classification  
Key Technologies Typical Distribution  
Low-temperature 25℃≤ temperature  
＜90℃  
geothermal energy  
Widely distributed  
inside the plate  
Hydrothermal  
type  
Medium-  
temperature  
geothermal energy  
90℃≤ temperature  
＜150℃  
geothermal  
energy  
High-temperature  
geothermal energy  
Temperature≥150℃  
Temperature≥200℃  
The narrow zones on  
the edges of tectonic  
plates  
Hot dry rock type geothermal  
energy  
At present, hydrothermal type geothermal power generation  
technology is mature, and its commercial demonstration  
47  
 
Development and Outlook of Clean Energy Power Generation Technology  
application has been realized in some regions with good resources;  
hot dry rock type geothermal energy has a great development  
potential but still faces technical bottlenecks. For hydrothermal  
type geothermal power generation, underground steam and hot  
water are exploited directly with drilling and completion  
technologies to act as the power source and to drive the rotation  
of the gas turbine for power generation. For hot dry rock type  
geothermal power generation, artificial geothermal reservoirs  
are formed in the low-permeability dry hot rock mass  
underground (3,000m - 6,000m) by means of hydraulic fracturing,  
etc. Low-temperature water is transferred to thermal reservoirs  
via injection well, and then, low-temperature water is heated to  
high-temperature steam (about 150℃-200℃) by the heat of the  
hot dry rock. Afterwards, the high-temperature steam in rock  
fractures is extracted to the surface via producing well for power  
generation3.  
3
Hu Bin and Wang Yu. Brief Discussion on Geothermal Power Generation Technology [J].  
Dongfang Electric Review, 2019, 033 (003): 84-88.  
48  
Development and Outlook of Clean Energy Power Generation Technology  
Fig.5.1 Hydrothermal Type and Hot Dry Rock Type Geothermal Power  
Generation Technologies  
Since different geothermal resources have different properties,  
there are different power generation methods that mainly can be  
classified into three categories, i.e., power generation with dry  
steam method (including back-pressure power generation and  
condensing power generation), flash evaporation power  
generation and dual fluid (intermediate medium method) power  
generation. Different geothermal resources have different power  
generation methods. Corresponding power generation methods  
can be applied to hydrothermal type geothermal resources based  
on temperature of the heat source. However, dual fluid power  
generation technology is mainly applied to hot dry rock resources,  
which is able to prevent equipment safety hazard due to quality  
of geothermal fluids. At present, flash evaporation power  
generation and dual fluid power generation technologies take a  
large proportion in the existing geothermal power generation  
projects around the world.  
49  
Development and Outlook of Clean Energy Power Generation Technology  
5.2 Key Technologies  
Many key technologies are involved in the development and  
utilization of geothermal energy, including geothermal well  
development technology, geothermal fluid collection technology,  
geothermal power generation equipment design technology and  
geothermal field reinjection technology.  
Geothermal well development mainly includes resource  
assessment and drilling. The installed capacity of geothermal  
power stations is closely related to the geothermal resources of  
geothermal wells. On one hand, it is necessary to provide  
geothermal wells with sufficient resources to ensure the operation  
at full power; on the other hand, it is necessary to avoid the failure  
to meet the full life cycle operation requirements of the project  
due to inadequate thermal storage. Therefore, a thermal storage  
model shall be established at the early development stage of a  
geothermal power station to analyze the internal changes of the  
geothermal field and assess the actual situation of the geothermal  
well correctly. Particularly, as for emerging hot dry rock  
geothermal power generation technologies, it is necessary to  
perform further research on the assessment method of hot dry  
rock geothermal resources. Geothermal well drilling is the only  
method to explore and acquire geothermal resources. It can be  
50  
 
Development and Outlook of Clean Energy Power Generation Technology  
divided into drilling and well completion. Among them, drilling  
is the precondition for geothermal fluid exploration. Drilling  
depth, complexity of geological structure, geographical location,  
advanced depth, etc. have impact on drilling cost. Well  
completion is also known as completion, which is a key factor for  
the development of geothermal energy and determines the quality  
of geothermal fluids. For this reason, corresponding technologies  
shall be chosen based on the actual situation. With the deepening  
of high-temperature geothermal fields (e.g., hot dry rock), it is  
necessary to conduct research on key equipment and technologies  
for high-temperature drilling, including safety control technology  
for high-temperature drilling, high temperature resistant  
cementing slurry technology, high temperature resistant  
downhole tools, well trajectory monitoring and control  
technology, high temperature resistant drilling bit technology and  
drilling speed increasing technology, and high-temperature  
geothermal well completion and test technology.  
As for the collection of geothermal fluids, it is required to drill  
multiple geothermal wells on the same geothermal field. However,  
since the wells are far away from the powerhouse of the  
geothermal power station, it is necessary to connect all  
geothermal wells with the turbine by geothermal fluid collection  
51  
Development and Outlook of Clean Energy Power Generation Technology  
system, including pipe, support, hanger and other equipment.  
Producing well plant selection, pipe network design, steam  
separator design, drainage system design, supports and hangers  
design and insulation design need to be taken into account for the  
design of the geothermal fluid collection system. Additionally, the  
difference in the geothermal fluid parameters between different  
producing wells needs to be taken into consideration for the  
collection system.  
As for geothermal power generation equipment design  
technology, since the Earth's crust is composed of compounds  
containing multiple elements, the geothermal fluids exploited  
from geothermal wells usually contain a larger amount of mineral  
substances, such as silica, silicate and carbonate. The mineral  
substances in geothermal fluids are easy to have scaling along  
with the changes in fluid parameters, and much scaling will affect  
the flow resistance and heat transfer effect of geothermal fluids,  
thereby affecting the unit economy. In addition, the corrosive  
compositions in geothermal fluids will lead to different degrees  
of corrosion on the blade, pipe, valve and other metal surfaces,  
which will affect equipment service life. Therefore, when  
designing the pipe, valve, cylinder, blade, condenser and other  
equipment in the geothermal power generation system, the  
52  
Development and Outlook of Clean Energy Power Generation Technology  
characteristics of the geothermal fluids shall be fully considered,  
and corresponding measures shall be taken to ensure efficient,  
safe and continuous unit operation. Currently, the power  
generation technologies and supporting technologies for medium  
and low temperature geothermal resources have reached  
modularization, integration and industrialization development  
level, and organic Rankine cycle (ORC) and Kalina cycle power  
generation systems have been established. The key of medium  
and low temperature geothermal power generation technology in  
the future is to conduct foundation and engineering application  
research on organic working fluids, heat transfer components,  
unit modularization, new cycles, etc., as well as in-depth research  
on different technology roadmaps, such as organic fluid turbine,  
single and twin screw expander and efficient steam turbine  
modified by centrifugal refrigeration compressor. For hot dry  
rock type geothermal resources, the enhanced geothermal  
system (EGS), i.e., the method for exploiting deep thermal energy  
from low-permeability rock mass by forming a geothermal  
reservoir manually, has been proposed. The key technology of  
EGS lies on new corrosion and scale prevention processes, new  
corrosion resistant materials, etc. At present, Europe has made  
great progress on artificial heat storage, loop circulation, on-line  
53  
Development and Outlook of Clean Energy Power Generation Technology  
corrosion monitoring and anti-scaling technology.  
As for the reinjection of geothermal fields, to maintain the  
power generation capacity of geothermal fields and avoid  
environmental pollution due to direct geothermal wastewater  
discharge, it's necessary to take measures to convey geothermal  
wastewater and sewage back to the underground heat storage  
structure, and when necessary, supplement clean surface water, so  
as to ensure the heat-producing capability of the geothermal well  
and maintain the pressure of the geothermal fluids. Geothermal  
reinjection is a complex engineering technology, in which  
multiple factors, such as location selection of reinjection well,  
reinjection water flow direction, temperature control and  
reinjection pipe design need to be taken into account. Generally,  
a reinjection test needs to be performed to monitor the reinjection  
effect and research the motion law of the reinjected water in the  
thermal storage structure prior to large-scale reinjection, so as to  
develop a rational geothermal field reinjection scheme4.  
Table5.1 Key Technologies in Geothermal Power Generation Field  
Classification  
Key technologies  
Geothermal  
well  
Geothermal  
resource  
Geothermal resource exploration and  
assessment technology  
development exploration  
4
Mo Yibo, Huang Liuyan, Yuan Chaoxing, et al. Research Summary on Geothermal Energy  
Power Generation Technologies [J]. Dongfang Electric Review, 2019 (2).  
54  
Development and Outlook of Clean Energy Power Generation Technology  
Drilling technology, completion  
Geothermal  
technology, key high-temperature  
well drilling  
drilling equipment and processes  
Producing well plant selection, pipe  
Recovery of geothermal  
fluids  
network design, steam separator design,  
drainage system design, supports and  
hangers design and insulation design  
Efficient steam turbine, new corrosion  
and scale prevention processes and new  
corrosion resistant materials  
Geothermal power  
generation equipment  
Location selection of reinjection well,  
Reinjection of geothermal reinjection water flow direction,  
temperature control and reinjection pipe  
design  
field  
5.3 Development Prospect  
The hydrothermal type geothermal power generation technology  
has matured since the building of the first geothermal power plant  
in the early 1900s, and is now applied for commercial purposes  
in many countries and regions around the world. The hot dry rock  
resource are buried deep and have huge development potential,  
while the enhanced geothermal system (EGS) is now still under  
trial and has not yet been commercialized. The LCOE of  
geothermal power generation is presently about 7.2 cents/kWh.  
The key technologies involved in the geothermal power  
generation include geothermal well development, the collection  
of geothermal fluid, the design of geothermal power generation  
facilities, and the reinjection of geothermal field. The future  
development of geothermal power generation technology will  
55  
 
Development and Outlook of Clean Energy Power Generation Technology  
mainly focus on three directions: (1) Medium-low temperature  
geothermal technology to further reduce the steam exhaust  
temperature and improve the overall cycle efficiency; (2)  
Breakthrough of resource evaluation and site selection, high-  
temperature drilling and reservoir transformation and other  
technologies for dry hot rock based geothermal power generation;  
(3) Multi-energy complementary joint power generation with  
other clean energy power generation technology to improve the  
energy utilization efficiency. Based on the economic efficiency  
improvement brought about by the breakthrough of well drilling  
and completion technology, it is expected that, by 2050, the  
LCOE of geothermal power generation will have fallen to 5-6  
cents/kWh.  
56  
Development and Outlook of Clean Energy Power Generation Technology  
6. Ocean Energy Power Generation Technology  
Ocean energy is the joint name of all forms of energy contained  
in ocean water, including tidal range energy, wave energy, ocean  
current energy, ocean thermal energy and ocean salinity energy.  
The ocean covers 71% of the surface of the Earth. The ocean  
contains rich resources and energy. Full exploitation and  
utilization of ocean energy resources will provide human beings  
with an option for solving energy crisis.  
6.1 Overview  
Ocean energy is generated by multiple factors, such as heating of  
seawater by solar energy, the sun's and the moon’s attraction to  
seawater and the Earth’s rotation force. It is a kind of  
inexhaustible renewable energy. Ocean energy has a great  
development potential. The global theoretical reserve is about  
2,000PWh/a, and the technically exploitable scale is about 6.4TW.  
See 0 for the theoretical potential of various kinds of ocean energy  
in the world.  
Table6.1 Theoretical potential of Various Kinds of Ocean Energy in  
the World5  
Unit: TWh/a  
Type  
World  
China  
Characteristics  
5
The Press. China Electric Power Encyclopedia [M]. China Electric Power Press, 2014.  
57  
     
Development and Outlook of Clean Energy Power Generation Technology  
Both the flow velocity and  
Tidal  
range  
energy  
direction follow obvious semi-  
diurnal, diurnal or semimonthly  
periodic variation  
8000  
289  
Has instantaneous randomness  
and periodic variation of  
average value in a time scale  
longer than one month  
Wave  
energy  
29500  
2186  
Ocean  
current  
energy  
4200  
444000  
2000  
-
Relatively stable  
Very stable  
Ocean  
thermal  
energy  
2000  
66.2  
Ocean  
salinity  
energy  
Has obvious annual and seasonal  
variation  
There is a large theoretical reserve of global ocean energy, but the  
energy density is lower than conventional energy. For example,  
the temperature difference between the sea surface and the 500-  
1,000m deep seawater is only about 20℃, which is far less than  
the temperature difference after power generation work of the  
superheated steam of thermal power plants. In addition, the large  
tidal range is only 7-10m, the wave height is about 3m, and the  
current velocity is only 4-7 nautical miles/h. Both the water head  
and the flow velocity are very small compared with those of  
hydropower stations. Therefore, the existing conventional power  
generation technologies are hard to be applied to the development  
58  
Development and Outlook of Clean Energy Power Generation Technology  
of ocean energy directly. It is necessary to make research on ocean  
energy acquisition mechanism, highly nonlinear hydrodynamics  
of fluid-solid coupling and other fundamental subjects, and make  
breakthrough on high-reliability control device, offshore  
construction, operation and maintenance as well as other  
engineering application technologies.  
6.2 Key Technologies  
The tidal power generation technology is the most mature among  
all of the ocean energy power generation technologies, and has  
been developed commercially. Wave energy now has several  
demonstration projects, while ocean current energy and ocean  
thermal energy are still undergoing principle research and pilot  
testing, and the ocean salinity energy is still at the laboratory  
research stage.  
The key aspects involved in tidal energy power generation  
include the prediction and evaluation of tidal energy and the  
design of tidal power stations, among others. In the future, the  
sites with good conditions will be fully developed, and the  
periodicity of tidal power generation and the special  
characteristics of wind power, photovoltaic power and other clean  
energy power generation technologies will be fully implemented  
to achieve clean energy utilization and energy complement. The  
59  
 
Development and Outlook of Clean Energy Power Generation Technology  
key technologies of wave energy power generation include  
wave load design and its survival technology in the marine  
environment, plant construction and ocean engineering  
technology during construction, and design and operation  
optimization technology of power plant in irregular waves etc. In  
the future, it is expected to be developed with offshore wind  
power to share power transmission channels, and improve the  
comprehensive availability of the system. The key technologies  
involved in the ocean current power generation include the  
design of high-efficiency blades, and the improvement of power  
control methods, self orientation accuracy, and installation,  
anchoring and maintenance technologies etc.. In the future, it will  
play an important role in the power supply in the open sea and the  
deep sea. The key technologies involved in the ocean thermal  
power generation include heat exchanger corrosion protection  
and marine microbial attachment protection technology, and the  
manufacturing and installation technology of cold sea water pipes  
etc. In addition to power generation, the deep seawater can be  
utilized comprehensively, and marine aquaculture, seawater  
desalination and other industries can be developed together. The  
key technologies involved in the ocean salinity energy power  
generation include the improvement of osmosis membrane  
60  
Development and Outlook of Clean Energy Power Generation Technology  
efficiency, the reduction of osmosis membrane manufacturing  
costs, the extension of osmosis membrane service life and a  
breakthrough of bottlenecks in technology and site selection to  
gradually realize the transition from laboratory tests to  
engineering applications.  
6.3 Development Prospect  
The focus for the future development of ocean energy power  
generation technology includes: (1) Improvement of power  
generation efficiency and installed capacity of power plants; (2)  
Improvement of the operation reliability of power plants and  
power generation facility in the high-salinity and high-corrosion  
environment; (3) Reduction of power plant construction costs and  
O&M costs to improve the economic efficiency of ocean energy  
resources development.  
61