Canadian Solar Inc. · PDF fileCanadian Solar Inc. ... 16 3.4 “PV + Internet” &...

Canadian Solar Inc.545 Speedvale Avenue West GuelphOntario, Canada N1K 1E6www.canadiansolar.com

SOLAR INDUSTRY TECHNOLOGYREPORT 2015-2016

Compiled by: Canadian SolarOctober, 2016

Dr. Shawn Qu, Chairman and CEO of Canadian Solar Inc.

ACKNOWLEDGEMENTSThe following resources are referenced within this report: The “2015-2016 Annual Report

on Chinese Solar Industry” from the China Photovoltaic Industry Association (CPIA), the

“International Technology Roadmap for Photovoltaic 2016” from ITRPV, and “The Power To

Change: Solar and Wind Cost Reduction Potential to 2025” from IRENA, all of which

contributed crucial data analysis and infographics to this report. At the same time,

Canadian Solar would like to thank all our supporters within the industry for their

continued and heartfelt assistance.

Editorial staff:

Guoqiang Xing, Xusheng Wang, Weifang Liu, Bin Liu, Chuanjun Yun,

Xiaoling Wang, Haitao Jin, Yesuo Ni, Liguang Cui, Baohua He,

Tao Xu, Zhengyue Xia, Jingbing Dong, Jun Chen, Hui Wang

Translated by Chong Zhang Qu, Yuan-yuan Qu, George Qin, Marc Wallowy

Canadian Solar project, PSEG Solar Power Plant, California USA, 19.3 MW

NO.1 SOLAR COMPANY IN THE WORLD IN 2015 ACCORDING TO PHOTON2015 REVENUE $3.5 BILLION

2015 NET INCOME $172 MILLION2015 SHIPMENTS 4.7 GW

2016 SHIPMENT GUIDANCE 5.1 – 5.2 GW2016 PROJECT PIPELINE 20.4 GW

TOTAL MODULE SHIPMENT 16 GWOVER 500 TECHNOLOGY PATENTSOVER 8,900 GLOBAL EMPLOYEES

TABLE OF CONTENTS

ACKNOWLEDGEMENTS·········································································································································Ⅰ

EXECUTIVE SUMMARY········································································································································ 01

I. SUMMARY OF TECHNOLOGIES IN THE SOLAR INDUSTRY········································································ 02

1. Technology Trends in Crystalline Silicon ·································································································021.1 The Silicon Material Industry and Its Technological Progress·································································021.2 The Silicon Wafer Industry and Its Technological Progress·····································································04 1.3 The Solar Cell Industry and Its Technological Progress··········································································· 061.4 The Solar Module Industry and Its Technological Progress ··································································· 08

2. Thin-Film Solar Cell and Module Technological Progress······································································112.1 Silicon-Based Thin-Film Solar Cells···············································································································112.2 Cadmium Telluride (CdTe) Solar Cells··········································································································122.3 Copper Indium Gallium Selenide (CIGS) Solar Cells·················································································· 13

3. Solar System Technological Progress········································································································153.1 Tracking Systems and Grid Parity················································································································ 153.2 Innovation Fuels Inverter Development······································································································163.3 Solar Power in Complex Regions················································································································· 163.4 “PV + Internet” & “PV + Energy Storage”······································································································16

II. SILICON PV MODULE TECHNOLOGICAL PROGRESS·················································································18

1. Silicon Material Main Technological Progress·························································································181.1 Modified Siemens Method Further Optimizable, Remains Crucial··························································181.2 Silane Based Fluidized Bed Reactor (FBR) Method·····················································································19

2. Silicon Wafer Main Technological Progress····························································································· 192.1 Massive Cost Reductions for Czochralski Silicon ······················································································ 192.2 Multicrystalline Ingots Continually Improve····························································································· 202.3 Diamond Wire Cutting Becomes Mainstream··························································································· 21

3. Solar Cell Technological Progress·············································································································· 223.1 Diamond-Wire Cutting + Black Silicon cells lower costs··········································································· 223.2 Mono-PERC Raises Efficiency and Output·································································································· 243.3 Multi-Busbar Technology····························································································································· 263.4 N-Type Bifacial High-Efficiency Cells··········································································································· 28

4. Module Technologies Progress ················································································································· 334.1 Half-Cell Modules·········································································································································· 334.2 DCI Super-High Performance Modules······································································································ 364.3 Double-Glass Modules·································································································································· 37

4.4 1500 V Systems Essential for Lower Costs································································································· 404.5 Smart Modules, Key to the Door of Smart Energy ·················································································· 42

III. PV SYSTEM TECHNOLOGICAL PROGRESS································································································· 46

1. Technology Development of PV System Components·········································································· 471.1 Technical Development of Photovoltaic Mounts······················································································· 471.2 Inverter Technology Development············································································································· 511.3 Technological Development of Other System Components···································································· 53

2. Development of PV Power Stations in New Application Environments············································ 532.1 Mountain Power Station Systems················································································································ 532.2 Agricultural PV Systems·································································································································552.3 Fishery and Water Surface PV Plants··········································································································· 55

3. The Development of The Energy Internet and Energy Storage··························································· 573.1 “PV + Internet”·················································································································································583.2 “PV + energy storage”··································································································································· 593.3 The Development of Energy Storage Technologies·················································································· 63

IV. SUMMARY······················································································································································· 67

EXECUTIVE SUMMARYThe solar industry has experienced steady growth on a global scale this past year thanks to the support of many countries

who have chosen to adopt solar energy into their lands. With constant technological breakthroughs happening within the

industry and the steady growth it is enjoying, solar energy is playing a key role in the adoption of clean renewable energy

sources for the world. In the past year, the solar industry has grown by approximately 22%, the fastest rate of growth found

within any energy sector, and this growth is in no small part due to increasing efficiencies and dropping costs, with grid

parity being an obtainable goal in the near future. In the latter half of 2016, several Chinese solar projects have seen final

bidding prices of 0.6 RMB/ kWh, or nearly $0.09/ kWh.

Solar has proven itself to be a highly competitive player in the renewable energy market, and is now experiencing a gradual

shift from utility-scale projects to more numerous, but smaller scale projects. In China, an increasing number of projects are

not built in the sparsely populated Western fringes of the country, but towards the East, where the majority of the

population is concentrated. To save land, a variety of innovative applications are being implemented in China, including

solar modules installed on greenhouses, on fishing ponds, floating on water, or on farmers’ rooftops.

The cost decrease of solar energy could not have been achieved without the advances in technology that the industry has

enjoyed in this past year. This document focuses on the innovations achieved within the area of crystalline silicon

photovoltaic (PV) technology, analyzing the industrial chain and elaborating on the key technology developments. Chapter 1

is a brief summary of the technological changes and innovations in the industry. Chapter 2 elaborates on some key

improvements within each link of the PV value chain. Chapter 3 presents innovations on system level, and chapter 4

provides a projection on the efficiencies and costs for solar energy in the future.

01

Canadian Solar project, "Saishang Jiangnan" Solar Power Plant, Ningxia, China, 10 MW

SUMMARY OF TECHNOLOGIES IN THE SOLAR INDUSTRY

02

I.SUMMARY OF TECHNOLOGIES

IN THE SOLAR INDUSTRY

The solar PV industry is heavily focused on crystalline silicon and thin-film technologies. Chapter 1 presents a brief introduction to the advancements in these two technology sectors, with focus on crystalline silicon technology, which encompasses more than 90% of the current market.

1. Technology Trends in Crystalline Silicon

Silicon is the most abundant semiconductor element found in the earth’s crust with bandgap energy of 1.12 eV. From an energy conversion efficiency standpoint, bandgap energy of 1.1 eV to 2.1 eV is the ideal range for PV modules. As such, silicon is the ideal material for solar in regards to both conversion efficiency and bandgap range.

Crystalline silicon-based PV modules are advantageous in the following categories:�� High stability and reliability� Long lifetime over 25 years� Technological support from the micro-electronics sector� Mature cell manufacturing technology

Due to these advantageous characteristics, crystalline silicon PV modules have maintained a strong presence in the solar PV industry. The following pages present and discuss the four major sectors within the industry value chain:��

1.1 The Silicon Material Industry and Its Technological Progress

In 2015, the production capacity of polycrystalline silicon rose to 470,000 metric tons worldwide, up 80,000 metric tons from 2014’s maximum capacity of 390,000 metric tons. This totalled at 345,000 metric tons of polycrystalline silicon produced in 2015, an increase of 14.2% compared to the 302,000 metric tons produced in 2014.


03

Figure 1.1 2010-2015 Global polycrystalline silicon production volume (104 Tons)

Data sourced from: CPIA 2016

The technological progress for silicon material can be sorted into two categories:��

Due to fierce competition, the Siemens method continually improved. By doing so, energy and material consumption was reduced and production was boosted, creating a stable foundation for the PV industry to continue its path towards grid parity. Through technological progress, the total electricity consumption at this stage can be reduced to below 60 kWh/kg-si.

�� !�� Fluidized Bed Reactor technology is primarily utilized to produce granular silicon material. It can be continuously produced without the need of silicon seed rods. The total electricity consumption can be reduced to below 25 kWh/kg-si. Because of the cost advantage it provides by increasing the charge amount per crucible by filling out the spaces between silicon chunks and by enabling continuous charging, there is a rising demand for granular polycrystalline silicon within the industry.

According to the most recent predictions by ITRPV, modified Siemens technology and FBR technology will dominate within the next 10 years.

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Figure 1.2 Future trends for silicon material technology

Data Sourced from: IRTPV 2016

1.2 The Silicon Wafer Industry and Its Technological Progress

Figure 1.3 2010-2015 Global silicon wafer production capacity/volume/GW


Due to the recent rebound of the global PV industry, silicon wafers have enjoyed a period of rapid growth and expansion. Supported by the optimization of the crystallization process, the widespread application of diamond wire sawing technology for mono wafers and the numerous advancements in poly wafer technology, the year of 2015 resulted in a 20.6% increase in production capability towards the previous year.


production capacity

production volume

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Main progress in crystal growth and wafer technology:

�� #��' �� Compared to silicon ingot casting for poly wafers, the Czochralski process of growing monocrystalline silicon ingots was comparatively suboptimal leading to low production rates. In recent years, the cost of growing mono ingots has been lowered to below 50% of its former levels by increasing the speed and loading capacity of crucibles in combination with the Continuous Czochralski method (CCZ) and similar innovative methods. Due to the rapid drop in cost and the consistent advancements being made, industry demand for mono wafers has been on the rise.

��* �� Polysilicon ingots have grown from G5 (5x5=25 bricks) in 2009 to current G6/G7 (6x6/7x7) formats, with a load capacity of 1200 kg, up from 420 kg in past years, resulting in a 50% increase in production capability. As technology and equipment advanced, the production yield of polysilicon ingots increased, lowering defect rates and costs. With poly cell efficiency reaching 18.3% in 2015, the cost-effectiveness of polysilicon wafers was maintained.

��;��'�� '�� Since 2015, diamond wire cutting has been successfully implemented in the manufacturing process for mono silicon wafers. However, the same method could not be utilized for poly wafers due to the incompatibility with the current texturing process, and only recently was there a breakthrough to allow this. In 2015, black silicon matured technologically and facilitated a successful introduction of diamond wire cutting in the manufacturing of poly wafers. Once black silicon texturing becomes widespread and diamond wire cutting can be utilized for poly cells, the cost-effectiveness of poly wafers will improve further.

��<�� '�� Following the increased demand for high-efficiency solar cells, the competition surrounding the technology behind silicon wafers has fuelled the research for newer, innovative methods. N-type mono-like wafers are an example of this phenomenon, being a combination of N-type mono-wafers and mono-like wafers, a hybrid achieving conversion efficiency rates of 19.5% and beyond.

Figure 1.4 Efficiencies of various poly/mono wafers compared



poly mono-like mono

�� >��?��#�� @��[\]�^��_�[`]�^�?�@��the steady rate at which costs for solar power are falling, there is a demand to drive silicon wafer research ��{�>�� <|�*}�'�� ?�' ��@��[~]�^��@��]��?�� @��@�� [�]�^��#��{�

��

Data sourced from: ITRPV 2016

Additionally, the silicon wafer industry is likely to experience a period of standardization, with a universal size and thickness being set for silicon wafers. By changing dopant, lowering oxygen content and introducing other technology improvements, the silicon wafer’s quality will improve further, leading to a greater increase in conversion efficiency, lower light-induced degradation (LID) and a longer effective lifetime of the solar modules.

1.3 The Solar Cell Industry and Its Technological Progress

With the global solar industry on a positive growth path, the production of solar cells has followed this trend, growing 23.5% in terms of total volume in 2015, with a total of 62.1 GW of solar cells manufactured worldwide.

Figure 1.6 2010-2015 Global solar cell production volume (GW)


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Production volume

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<��][�?�� ' �� ]{]��[\{~��'��_��attributed to the improvement of silicon wafers, front metallization, emitters and the aluminium paste on the back. As of now, the aluminum back surface field (BSF) is the main factor limiting the cell efficiency of a traditional solar cell. Various high-efficiency cells are now being developed to tackle the problem. Solar cells such as PERC cells, N-type bifacial cells, IBC cells, HJT cells and TOPCON cells will have an increasingly large share.

Figure 1.7 2015-2026 Relative cell shares within the global industry


Main progress in solar cell technology

��#�' �� '��' �� Black-poly cells owe their conception to the inclusion of intricate nano-structures on the surface of the cells, which results in exceeding levels of light absorption due to a significant increase in the relative surface area capable of doing so. Such a technique results in a vast decrease in the reflective properties of black-poly cells, and greatly improves the conversion efficiency of black-poly cells. By combining this technology with highly cost-efficient diamond wire processing, poly solar cells can see their relative costs drop by over 26%, greatly boosting their competitiveness.

�� *��@ �� '�� PERC, also known as Passivated Emitter and Rear Cell, utilizes the passivation effect to reduce the surface recombination on the back side of solar cells, resulting in an overall increase of at least 1.0% in conversion efficiency for Mono-PERC cells compared to normal mono cells. Due to this advantage, we witnessed a global leap of PERC technology in both mono and polycrystalline cells in 2013. In 2015, the global production of PERC cells surpassed 7 GW in capacity, a stunning increase of 180% compared to 2014, and there’s no sign this trend will stop in 2016.


08

��'��@��@�� The current status quo for solar cells is to incorporate 4 busbars in their construction. Pioneered by Canadian Solar in 2015, and then followed by other corporations, solar cells utilizing 5 busbars were introduced to the solar market. At the same time, an increasing number of corporations have funneled efforts into developing cells with more than 5 busbars and bar-less cells. With the characteristic of maintaining and even increasing the conversion efficiency of a cell and decreasing the consumption of conductive silver paste, the introduction of increasingly varied busbar counts in cells is driving changes in the solar industry.

Figure 1.8 Relative paste consumption against busbar count

Data sourced from: Canadian Solar R&D

Figure 1.9 2015-2026 Projected multi busbar growth


1.4 The Solar Module Industry and Its Technological Progress

At the eve of 2015, the global production capability of solar modules reached a maximum of 99.8 GW, with a � �� {~��;� �� {��;�� !�@��_�� {[��compared to the previous year.


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Figure 1.10 2011-2015 Global solar module production volume/capacity (including thin-film module) (GW)


Since 2012, silicon PV modules have experienced a relatively stable increase of 0.3% in efficiency annually. In order to boost this growth while reducing the cell-to-module encapsulation loss and extending the effective lifetime of modules, manufacturers have utilized a variety of measures.

Main progress in solar module technology

�� ' ��Following the growing market demand for high wattage modules, half-cell modules have returned to the limelight. By cutting normal cells into halves and stringing them to form a module, every string of half-cells experiences a 50% reduction in the current flowing through the circuit, thus reducing the electrical resistance loss within the string and boosting output. If a module consists of 144 halved PERCs, which is equivalent to a 72-cell PERC module, the output of the half-cell module can reach beyond 380 W, an increase of 2.5%. For certain half-cell module designs, the half-cell module’s hot spot temperature can be 20°C cooler than that of the full-cell version, greatly reducing the risk by reducing the power in each sub string.

During the 2016 SNEC and SPI Exhibitions, REC, GCL, LERRI, Hanwha, and HT-SAAE sequentially unveiled their half-cell modules. It is predicted that by 2017 half-cell modules will enter the market and achieve GW-levels of production.

��<�� <!�� Compared to the traditional method of soldering solar cells together by copper ribbons, DCI technology utilizes a zero-soldering method of connecting strings. Solar cells are hereby cut to five or six thin strips. The thin strips overlap in a manner similar to roofing tiles, and a conductive adhesive is applied to the overlapping areas as conductive medium. This arrangement eliminates any gaps between the cells. By utilizing the available surface area efficiently, the light absorption by forgoing ribbons that would otherwise cover up portions of the cells is increased and the electrical resistance loss is reduced, leading to record high values in the wattage and efficiency of a DCI module.

However, a number of key issues remain with DCI modules:��@��#��'�� '�� ' �� @��@�� @��


Production volume

Production capacity

10

With the steady expansion of solar applications, solar plants in certain weather and climate conditions have set new demands for solar modules, including a high resistance to wind/sand corrosion, humidity, PID, micro cracks, snail-trails and chemical corrosion. In order to facilitate reliable operation in increasingly harsh environments, double-glass modules were created. With a 30-year operational guarantee, an annual degradation rate of 0.5%, and high reliability, double-glass modules were widely implemented soon after their debut. According to an EnergyTrend study, Chinese manufacturers shipped 800-900 MW of double-glass modules in 2015.

��[~]]�}�� Based on the statistics of IRENA for 2009 - 2015 regarding the cost development for PV systems, 1000 V systems are now reaching a bottleneck. A higher input/output voltage can reduce electrical loss from the DC/AC cables, the DC-AC inverters and the low voltage coil of the transformers, increasing the efficiency of a PV power plant by up to 2%. Furthermore, the efficiency of converters and transformers will increase while decreasing in volume, causing a reduction in transport fees, which benefits the overall cost structure of solar systems. To achieve grid parity, 1500 V systems are a must, and ITPRV predicts that 1500 V systems and those with a higher voltage will lower energy costs and become the industry standard in the near future.

Figure 1.11 2009-2025 Total cost averages for utility-scale PV projects

Data sourced from: IRENA 2015

Figure 1.12 Cost predictions of varying voltage systems

Data sourced from: GTM

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�� Smart modules integrate specialized power electronics and have enhanced functionality. Their four main features are:a) Rapid shutdownb) Module surveillancec) DC-DC efficiency enhancement, allowing for maximum power point tracking (MPPT)d) DC-AC efficiency enhancement, allowing for MPPT

Currently, both AC and DC smart modules exist. �� ）,b）and c）��>�� ）,b）and d）

Additionally, there are low-cost alternatives in form of smart monitored modules and smart optimized modules, both of which are smart DC modules. Smart monitored modules possess rapid shutdown and module surveillance functions, while smart optimized modules have cell-string-level MPPT.The module-level MPPT enables smart modules to be installed in locations such as rooftops, where they experience complex shading. This enables higher module output, while remote surveillance and rapid shutdown add more convenience and safety. By implementing smart systems from the basis of a single module into an entire grid, a mass-optimization of the system can be achieved, lowering costs and raising both output and efficiency. By 2020, it is likely that smart module systems will be implemented on a GW scale.

2. Thin-Film Solar Cell and Module Technological Progress

Compared to silicon-based crystalline technology, thin-film technology consumes less material during production and can be produced continuously at large size, implying the potential of lower cost and shorter payback period. The semi-transparent and flexible characteristics of thin-film solar products also have advantages under certain conditions, such as handheld solar applications and curved-surface applications. Due to the above reasons, thin-film technologies have been the research focus for long time.Currently, there are mainly three types of thin-film technologies in industrial mass production: silicon-based thin-film solar cells, CdTe thin-film solar cells, and CIGS thin-film solar cells. Chapter 2 will introduce these three types of technologies briefly.

2.1 Silicon-Based Thin-Film Solar Cells

The development of silicon-based thin-film solar cells shows diversity, including single-junction or multi-junction tandem solar products, rigid or flexible substrate solar products. Currently, silicon-based thin-film solar cells produced within and outside of China are primarily composed of a-Si single-junction, a-Si/a-Si tandem-junction, and a-Si/a-SiGe/a-SiGe triple-junction.

The commonly used rigid substrates are transparent conductive glass. Below is the illustrative figure of above-mentioned three types of thin-film solar cells using transparent conductive glass as substrates, showing the structural difference between single-junction, tandem-junction, and triple-junction. The flexible substrates used mainly consist of stainless steel, polymer, metal foils and etc. Compared to glass substrate, flexible substrate has the advantages of lighter weight, foldable, and not easy to damage. Flexible solar cells have broader applications ranging from solar vehicles, planes, zeppelins, sailing vessel and rowing boats. However, silicon-based thin-film solar cells are not the main-stream due to relatively low efficiency and high module degradation.


12

Figure 1.13 The structural difference between single-junction, tandem-junction, and triple-junctionT


Figure 1.14 The flexible thin-film cell

2.2 Cadmium Telluride (CdTe) Solar Cells

CdTe solar cell is one of the compound thin-film solar cells, based on the heterojunction formed by p-type CdTe and n-type CdS. The absoption coefficient of CdTe is very high, thus very suitable for solar cell application. Theoretically 1 micro m of CdTe can absorb 99% of incident sunlight. The structure of CdTe solar cells is shown in Figure 1.15. The fabrication process is depositing TCO on glass substrate first, followed by depositing n-type CdS layer, p-type CdTe layer and rear metal electrode.

glass glass

glass

ZnO ZnO ZnO


13

Figure 1.15 CdTe Thin-Film solar cell structure diagram

Currently, the module efficiency of CdTe is about 16%. The efficiency needs further improved to compete with Si crystalline solar cells. Possible improvements are:��''�� @� '�� <�' �� @�� '�� '�� '�� ' �� '��@��#��@��#�� ' �� '�� temperature coefficient

In terms of the commercialization of CdTe solar cells, First Solar is the most successful company with 2.9 GW shipment in year 2015.

2.3 Copper Indium Gallium Selenide (CIGS) Solar Cells

Like CdTe, CIGS solar cell is also one of the compound thin-film solar cells. CIGS with chalcopyrite structure is very promising for high-efficiency solar cell application. CIGS thin-film solar cells have the highest efficiency among all single-junction thin-film solar cells, with laboratory efficiency about 23.5%, very close to silicon solar cells.

Figure 1.16 CIGS thin-film solar cell structure diagram

Glass

Metal electrode


Buffer layer

Light blocking layer

Glass

Antireflectiive film

14

Most companies use glass substrates for CIGS solar cells. Figure 1.16 illustrates the structure of CIGS solar cell, mainly consisted of sodalime glass substrate, Mo electrode, p-type CIGS absorber layer, n-type CdS buffer layer and intrinsic-ZnO/Al-doped-ZnO window layer. Besides, similar to silicon solar cells, CIGS solar cell also has AR coating and Ag electrode. CIGS layer serving as the absorbing materials is the key of the solar cell device.

The R&D of CIGS solar cells has achieved remarkable progresses. Some companies already phase into mass production. However, there are still several key technical issues to solve:�� '��@�� ' �� '�� ?�� ' �� @�� ' �� @��

Figure 1.17 Thin-film cell market share from 2009 to 2015


In conclusion, thin-film solar cells have several advantages over silicon solar cells, but also have certain severe shortcomings. Thin-film solar cells need further improvements of conversion efficiency and outdoor stability, in order to compete in the market. However, looking into the shrunk market share of thin-film solar cells from 2009 to 2015, silicon solar cells will remain dominant in the PV industry.


Market share

15

3. Solar System Technological Progress

By the end of 2015, the global cumulative installation of PV modules exceeds 230 GW, with 53 GW newly installed in 2015, up 23.3% from the previous year. According to the prediction by international energy agency (IEA), by 2030 the global cumulative installation of PV modules is expected to be more than 1000 GW. According to the forecast by European Commission's Joint Research Centre (JRC), by 2050 solar generates 25% of the world's total electricity, and reaches 64% by 2100 as the major energy for the future world.

Figure 1.18 Photovoltaic module of new installed capacity


Currently, the major applications of PV include large ground station, solar roof, BIPV and etc. With the development of PV industry, the technical requirements of solar systems gradually lead to precision, integration and intelligent. For ground stations, using tracking system to boost power generation is important to reduce LCOE. As PV stations changing from centralized to distributed, from the vast and sparsely populated areas to the densely populated areas with large electricity consumption, the land for PV stations becomes to be the limitation. All kinds of PV innovations emerge endlessly to create new PV "green economy". In the future, “PV + Internet" and "PV + energy storage" are two important directions to widen the application of PV technology. To improve the potential of PV application by increasing power grid's ability to access the intermittent energy and improve the stability of PV electricity generation.

3.1 Tracking Systems and Grid Parity

According to the regulation of stent adjustable angle and means, solar tracking system can be divided into adjustable fixed, single axial, tilted single axial and dual axial. According to experimental results, single-axis tracking can generate 10% - 20% more electricity, and tilted single-axis tracking can generate 20% - 25% more electricity, while dual-axis tracking can maximumly generate 40% more electricity. The global market size of PV tracking systems is 5 GW in 2015. According to the prediction by GTM, the global market size of PV tracking systems is expected to be 38 GW in 2021.


China

Global

Figure 1.19 Tracking Systems and Grid Parity

Data sourced from: GTM 2016

3.2 Innovation Fuels Inverter Development

The development of inverters mainly reflected by application of new materials, application of new devices, multilevel optimization technology, inverter structure optimizaiton and optimization of other related technologies. The emerging of larger current density, better thermal conductivity, lower thermal loss, higher voltage, higher switching frequency semiconductor materials greatly broaden the choice of inverter device materials. The application of GaN and SiC new materials makes further improvement of inverter’s reliability and performance. The application of new technology is mainly manifested in the introduction and combination of various multilevel technologies, making the inverter being more secure on reliability and output characteristics.

3.3 Solar Power in Complex Regions

With the large scale development of PV ground stations, people pay more and more attention on space resources. Investors began to look at the unused space or the neglected areas because of low value, such as water, roof, mountain, and steep slope areas, even reproducing tailing ponds. New applications bring up new challenges to system technologies. The specific challenges and technical solutions will be introduced in the third part of this article.

3.4 “PV + Internet” & “PV + Energy Storage”

As is pointed out in the “2016-2020 Chinese Solar Inverter Industry Deep-Research & Investment Prediction Report”, with continuous rapid reduction of PV cost in recent years, the convenience and economic advantage of PV gradually appears in the areas of high electricity price and areas lack of electricity, giving rise to the release of policies in India, South-East Asia, South America and other emerging markets, and leading to the blossoming of PV industry widely. But because of the intermittent characteristics of PV energy, the energy output is not stable influenced by the climate conditions. The continuous promotion of PV energy generation needs to concentrate on two technical directions: "PV + Internet" and "PV + energy storage".


16

0

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II. SILICON PV MODULE

TECHNOLOGICAL PROGRESS1. SILICON MATERIAL MAIN TECHNOLOGICAL PROGRESS

1.1 Modified Siemens Method Further Optimizable, Remains Crucial

For the polysilicon industry, year 2015 was a year of restructuring and reorganizing. Industry leaders focused on increasing production efficiency and product quality. Technology upgrading is widely performed to reduce materials consumption and energy consumption, in order to further decrease the costs of polysilicon modules.

Technical and Equipment Improvement are Reflected From:

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SILICON PV MODULE TECHNOLOGICAL PROGRESS

19

1.2 Silane Based Fluidized Bed Reactor (FBR) Method

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2. SILICON WAFER MAIN TECHNOLOGICAL PROGRESS

2.1 Massive Cost Reductions for Czochralski Silicon

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2.2 Multicrystalline Ingots Continually Improve

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2.3 Diamond Wire Cutting Becomes Mainstream

Through the successful application of diamond-wire sawing in the wafer section, the cost of mono wafers � '��'��][~{�� ?�� ' �� ~��#��?�� {�� ' �� @��?�� '�� production capacity. The inherent shortcomings of slurry sawing such as high silicon kerf loss, high � ��@�� ' �� '�� ' �� wafers. The application of diamond-wire sawing to polysilicon wafers draws more and more attention for the industry.

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Figure 2.2 Slurry cutting (left) and king diamond-wire cutting diagram (right)

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Figure 2.1 Diamond cutting vs Slurry cutting

3. SOLAR CELL MAIN TECHNOLOGICAL PROGRESS

3.1 Diamond-Wire Cutting + Black Silicon cells lower costs

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of charged molecules. These charged molecules accelerate within the electrical field, and are accelerated �� '��{�� ?��molecules undergo a strong chemical reaction when impacting the surface of the wafer, causing ��{��<�� ~��?��@��controlled during the creation process.

Figure 2.4 Manufacture principle of RIE

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3.1.1 Black Silicon Commercially Manufactured

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3.2 Mono-PERC Raises Efficiency and Output

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Figure 2.6 Structure of PERC

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Figure 2.7 A passivation effect (left) and light reflected on the back (right)

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Figure 2.8 Capacity of PERC is 2.5 GW in 2014 while 7.0 GW in 2015

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3.3 Multi-Busbar Technology

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Figure 2.9 History of busbar number increasing

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3.3.1 Introduction to Multiple BusBars (MBB)

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Figure 2.11 The relation between the power loss on the fingers and the number of busbars

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3.3.2 MBB Manufacturing Analysis

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Table 2.2 Main realization method of MBB

3.4 N-Type Bifacial High-Efficiency Cells

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Figure 2.14 N-type bifacial mono crystalline silicon substrate

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3.4.1 Introduction to N-Type Bifacial Cell Application

Figure 2.16 The influence of different installation to the output

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Figure 2.20 HJT cell structure diagram

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4. MODULE TECHNOLOGIES OVERVIEW PROGRESS

4.1 Half-Cell Modules

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4.1.1 Advantages of Half-Cell Modules

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4.1.2 Half-Cell Design Analysis

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4.1.3 Application of Half-Cell Module Technologies in current market

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Figure 2.25 Biopsy of portable charging PV module and solar lights

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4.2 DCI Super-High Performance Modules

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Figure 2.27 Technology Schematic of DCI

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37

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4.3 Double-Glass Modules

In recent years, customers from some special areas with extreme weather condition, such as deserts, ��'�� ?� ��@ ��''�� ?�� ?��@�� ?�� ?��*<�?�� #�free, and anti-snail-trail-pattern, etc. There may occurs cracking, yellowing, delamination and other ��@��' �� ?�� '�� ?�� {�<�� ?�� ' ��@��#�� #��?�� #� �� {

4.3.1 Advantages of Double-Glass Module

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Figure 2.28 Power contrast between standard module and DG module

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38

� <�' �� @�� @�� greatly increased, reducing the instances of micro-fractures and damaged components

Figure 2.29 Double glass module loading tests

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Figure 2.30 UL fire test: Class A

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39

Figure 2.31 DG in BIPV and bifacial DG

4.3.2 Double-Glass Module Market Situation

� �@�� @��@��?�� '��<*}��<��*}!��>*}��>��*}!?�� '��{�� @��?�� @�� @��' �� '�� ?�� ?�� ?��?� ��#�� ?��{�<��][~?�� @�� '��'� �� '��{�>�� |��?�� @�� '��'�� \]]�`]]��;�@��][~?��|��@��'��?�� @��'' �� {�

Figure 2.32 China's double glass shipments of 2015

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4.3.3 Introduction to double-Glass Module Manufacturing

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Figure 2.33 Problems of double-glass modules

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Figure 2.34 Application cases of DG module

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4.4 1500 V Systems Essential for Lower Costs

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40

Figure 2.35 The cost comparison of 1000 V and 1500 V

�� |��][~4.4.1 1500 V System Design Requirements

Figure 2.36 2 MW 1500 V system design

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4.4.2 1500 V System Requirements

Table 2.4 Design criteria of 1500 V modules

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4.5 Smart Modules, The Key To Smart Energy 4.5.1 Advantages Of Smart Module

<�� ' ��'��?��'�� @��?�� ?� ��?� � �� @�� ' @��?� � � �� ?� ��{� >�� unexpected situation may result in energy loss of the system, low utilization rate of the roof, potentially �� ?� � �� ?� �� ' ��@�� safety of the clients.

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Figure 2.37 Intelligent DC module (left) and intelligent AC modules (right)

4.5.3 Market Predictions for Smart Modules

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Figure 2.38 Shipments forecast of smart DC and smart AC

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46

III. PV SYSTEM TECHNOLOGICAL

PROGRESS

As reported by “Solarzoom New Energy Thinktank News”, the International Energy Agency Photovoltaic Power Systems Programme (IEA PVPS) and the International Renewable Energy Agency (IRENA) both published reports on photovoltaic and renewable energy sources during the first half of 2016. Their data shows that in 2015, the global new PV capacity installed reached 222 GW, with China, Japan, the US, England, India, and Germany accounting for more than 80% of the total capacity installed.

Figure 3.1 Global distribution of newly installed PV capacity

Figures from SOLARZOOM new Energy ThinkTank, 2016

The IEA predicts that by 2030, the cumulative global capacity of PV installed is expected to exceed 1,000 GW. The European Commission’s Joint Research Centre (JRC) predicts that by 2050, solar PV generation will account for 25% of the world’s total power generation; and that it will account for 61% by 2100, becoming the world’s primary energy source. In addition to PV modules, PV racks, inverters, and other system components must make great technological progress if we are to achieve this pace of development. At the same time, with the global expansion of PV power generation, PV systems continue to be used in increasingly complex environments. These environments bring a new set of challenges that require system design and technological advancements to accommodate them. Below is a brief introduction to the technological development of system components and the development of PV technology in new environments. The last section of this chapter will discuss the development of future technologies including “PV + Internet” and ”PV + Energy Storage.”

PV SYSTEM TECHNOLOGICAL PROGRESS

China Japan US UK India Germany

47

1. Technology Development of PV System Components

1.1 Technical Development of Photovoltaic Mounts

There are six methods of mounting for PV power plants:�� '�� !��@��#�� #��|��#��#��@��*}��

Figure 3.2 Tracking PV system

Besides initial investment and O&M costs, the biggest distinction between different PV systems is the difference in their generation capacity. When compared side-by-side in the same area throughout the seasons, tracking mount systems perform better than fixed systems in terms of power generation.

In addition to generation capacity, the initial investment and O&M costs must be taken into account when considering mounting systems. In terms of initial investment, O&M costs and acreage, we see the following: ��#��ª��#��ª�� #��ª��@��#��ª�� '�� {

<�� #��?�� #��{�>�' ��#�� the above points into account in order to achieve the lowest cost of electricity possible. According to GTM forecasts, the market share of tracking systems will gradually increase.


48

Figure 3.3 Forecast of installed capacity with various mounting methods in 2015-2021 (GW)

Figures from GTM 2016

1.1.1 Tracking Systems Finally Lead to Grid Parity

PV tracking systems use a combination of mechanical, electrical, electronic circuits and other components to �� *}�� '�� #�� ' ��generated. Tracking systems are sorted according to tracking angle and mechanism into categories such as ��@��?�� ?��#��{�>�� ?�horizontal single-axis systems can increase the power output by 10% - 20%, tiled single-axis by 20% - 25% and dual-axis by up to 40%.

Currently, there are three widely-used automatic tracking systems: the horizontal single-axis tracking, the ��#��#��{�� #��tracking have only one degree of freedom, whereas dual-axes have two. The tracking control strategy adopted by all three tracking systems is an active tracking control strategy. The orientation of the sun in the sky is �� '� � � ��{�

� �� #�� *}�� #�the sun’s path without tracking the sun’s declination angle, and are thus only used in lower latitudes. Tilted ��#�� {��#�� #��@��having the PV array move along two rotational axes, allowing it to simultaneously track the changes in the ��{�|�� ?� �� angle of zero.

Figure 3.4 Horizontal single-axis tracking system (left) and tilted single-axis tracking system (right)

2015 2016E 2017E 2018E 2019E 2020E 2021E

Trancking

Fixed Tilt

Rooftop


49

Figure 3.5 Dual axis-tracking system

The solar market is maturing with the increasing amount of power plants. In order to protect internal returns on investment, more and more PV power plants are adopting tracking mounting systems to realize lower generation costs. For example, 40% - 50% of US PV plants use single-axis tracking systems. Companies such as NEXTracker, Array Technologies have emerged in the tracking space. China’s current large-scale PV plants are predominantly ground-based power plants. With the decline in subsidies and the introduction of a series of policies such as PV bidding, the development of effective tracking systems to improve power generation efficiency has become increasingly important. The main players within the 2015 global PV tracking system's 7 GW market are NEXTracker, Array, First Solar and SunPower. According to GTM forecasts, the global PV tracking system market size is expected to reach 38 GW by 2021.

Figure 3.6 Tracking market distribution in 2015 (MW)



23.70%

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18.20%

10.20%

4.20%

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3.30%

3.20%

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10.40%NEXTracker

Array Technologies

Fist Solar

SunPower

Grupo Clavi�o

Soltec

Sun Action Trackers

Exosun

Sti Norland

Convert Italia

Other

50

Figure 3.7 Forecast of installed tracking system in different regions (2015-2021) in GW


1.1.2 Flexible PV Mounting Systems for Special Environment Installations

Figure 3.8 Flexible support mounting at a sewage treatment plant

Flexible PV mounting is predominantly used in special situations where conventional methods can’t be expanded, such as steep mountains slopes or areas panning across pools in hazardous waste plants. At Canadian Solar’s Kuancheng County PV power plant, 2 MW of flexible brackets are used on the horizontal dam surface and 0.5 MW on the mountain slope. The flexible brackets on the dam surface are RMB 0.1/watt cheaper than conventional brackets.

Figure 3.9 PV power plant with flexible mounting system

Image from Canadian Solar


0

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20000

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30000

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2015 2016E 2017E 2018E 2019E 2020E 2021E

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51

1.1.3 New Materials for the Development of PV Brackets

Given the changes in the application environment and the development of materials, materials such as fiberglass, ZAM (a new environmentally friendly and, highly corrosion-resistant steel made of zinc, aluminum and magnesium), bamboo, wood and other materials have been tested in small-scale trials for their suitability for use in PV mounting structures. ZAM materials are particularly worth noting as they have recently gained popularity in Europe and the US. ZAM material only needs to be galvanized in preheating, and does not require post-hot-dip galvanization. This can lead to a more convenient processing, shortening the process cycle. Additionally, ZAM materials can be positioned after the site has been constructed, and they have a self-healing coating, that enhances the reliability of power plants and reduces maintenance costs.

1.2 Inverter Technology Development

Current PV inverters can be divided into three types: String, centralized and distributed/central inverters. String inverters generally refer to inverters with small capacity. They use a small current MOSFET as power ��?�� ' � �� '��|�� @ �� ?�� ' �� >��full-inverters to convert.

They offer a high level of waterproof of IP65. They are small, light weighted, and capable of being mounted on the wall, suitable for small and medium-sized power plants.

Figure 3.10 System with string inverters

Centralized inverters generally refer to inverters with capacity of more than 100 kW, with power switches using ��<��|{�|�� ' � �� >�� ' �� consisted of full-bridge inverters and power frequency isolation transformers. Its waterproof level is generally <*�]��?�� {�|�� ' ��as ground power plants.


52

Figure 3.11 Centralized inverter schematics

��@��'�� @��@ ��{�|��'��'��MPPT control unit are added to minimize the efficiency loss caused by the inconsistency of component parameters, local shadowing and elevation differences. At the same time, the output voltage of the improved PV combiner box (PV controller) is increased (usually between 800 and 850 V), and the output voltage of the �� @��~]]�}�� ~~]�}��!?�� >��@��?�cutting the loss of the inverter and enhancing power generation.

Figure 3.12 System with distributed/centralized inverter

Inverter development is mainly determined by the application of new materials, the application of new devices, multi-level technology, inverter structure optimization and other technology-related optimizations. The emerging of a variety of semiconductor materials of higher current density, greater thermal conductivity, lower on-state loss, higher voltage and higher switch frequency leading to favorable inverter performance. The application of new materials such as SiC and GaN has resulted in further improvements regarding the reliability and optimization of product performance. The application of new technology is mainly reflected in the introduction and integration of a variety of multi-level technologies, which allow greater reliability and output quality.

The development of the inverter structure is mainly manifested in the development from single model to parallel module types, with an expansion of input channels and applications.

�� ?��**|��'��#�� ?�>��'��?��synchronous machines, soft-switching and advanced cooling technologies, have been greatly enhanced. In addition, the introduction of the 1500 V inverter allows the 1500 V system to be realized, which has positively


influenced the reduction in LCOE.

1.3 Technological Development of Other System Components

The high degree of system integration leads to efficiency gains. Integrating the inverters and transformers together can increase system efficiency by 0.6%. The introduction of smart combiner box and the development of centralized/distributed inverters has greatly enhanced the overall efficiency of the system.

2. Development of PV Power Plants in New Application Environments

With the large-scale development of PV power plants in the world, the spatial resources are receiving more and more attention. Investors have started looking for unused land, or areas that hold little value such as water surfaces, roofs, mountain areas, steep slopes, and even recycled tailings ponds. New environments '�� {�|�� @�� '��suitable components according to the characteristics of the space in order to fully develop these new spatial resources, reduce input costs, and achieve the highest economic and environmental benefits. For example, PV plants can be installed onto unique settings such as fisheries and farms, and thus not only reap the traditional product of fishers and farms, but also generate green power and take part in the new green economy.

2.1 PV Power Plants On Top of Mountain

Characteristics PV power plants on top of mountain:��}�� @��@�� |�� '��@��'�� *}�� '��'�� ?��#�� equipment

Figure 3.13 PV power plants on top of mountain

These power plants are located on complex terrain with significant differences in elevation. Selecting a reasonable layout for the array, setting array spacing, inclination and azimuth are both the design focuses and challenges of such a system. The construction of mountain PV plants should take the following aspects into consideration:

53


54

��|�� ' ��'�� '�� '�?�� @��eliminated and more usable areas can be selected

�� *}�' ��'��Inverter selection should be based on the details of the region, terrain, climate characteristics and other local conditions

Table 3.1 Application comparison of centralized inverter and string inverter series

Mountain PV system and power line design have three options:��@��@��@�� @��@��

Table 3.2 Comparison of the three methods of power line design for mountain PV systems

�� [\��;�*}�' ��'��¢�� ?��@��* ��{�<�� on a mountain tailing reservoir, and it’s the first of its kind in China.

Figure 3.14 Canadian Solar's 18 MW Mountain PV Plant

Image from Canadian Solar

Applicable environments for centralized inverters

a. Array is centered

b. Modules are oriented

in the same direction

c. Mountain slope is oriented south

Applicable environments for string inverters

a. Layout site has complex terrain

b. Array layout is more dispersed

c. Big difference in PV array capacity

d. Modules are oriented in different

directions

Proposal

Cables directly buried

Cables laid along bridges

Cables laid overhead

Economy

The best

Good

common

Applicability

Excavatable mountains with thick soil layer

Rocky and inexcavatable mountain

Complex mountain terrain and scattered solar arrays


55

2.2 Agricultural PV Systems

In 2015 - 2016, as agricultural PV system technology gradually matured and become market-oriented, tons of diversified development schemes have shown up in the market. The nature of agricultural PV systems lends itself to a number of different iterations, the most representative of which is the PV greenhouse. PV agricultural greenhouses and conventional agricultural greenhouses are compared and contrasted in Table 3.3.

Figure 3.15 PV greenhouse

Table 3.3 Comparison between common greenhouse and solar PV greenhouse

In order to promote the development of distributed PV power generation, the Memo on Further Implementing ��* �� @��*� � � ��* �� @�� >�� «�][�¬�� {��]�?�� ' ��*}�� @��' ��?�� benchmarking of PV plant prices and the favourable development of PV greenhouses. In terms of application, it is generally recommended that transparent double-glass module are used in PV greenhouses and other agricultural PV power plant.

2.3 Fishery and Water Surface PV Plants

In 2015 – 2016, the installed capacity of water-top PV plants exceeded over 3 GW. In September 2016, Anhui released tender documents for 1 GW of energy tenders requiring all bids to be for floating PV plants. Shandong Jining’s 500 MW tender also required 400 MW to be compatible with fisheries. This explosive growth in fishery-compatible systems in 2016 will be conducive to the further improvement of the standards and technologies of PV systems.

Category

Growing cycles

Temperature control

Lights control

Environmental pollution

Useful life

Economic benefit

Electricity selling

Ordinary greenhouses

Twice per year

Out of control

--

Plastic film

One year

Agricultural income

No

PV greenhouses

3~4 times per year

Under control

Can filter the light

Zero

25 years

Agricultural income + Tourist income

Yes


56

The benefits for fishery PV systems are great in terms of land conserved as well as improving both the water use and the fishery model. Because bodies of water have a cooling effect on PV modules, they can help prevent module surface temperature from rising, and they have a greater power generation capacity. According to the results of experiments comparing water PV power plants with systems installed on roofs and on land at the same angle, the power generation of water PV systems can be 5% to 15% greater.

Figure 3.16 Japan Hyogo floating power station

With current technology, water PV plant are divided into two categories, fixed piles and floating stations. The main difference between a fixed pile PV power plant and a traditional PV plant is that fixed pile PV power plant place the pile in water, which increases the cost and difficulty of construction, but helps to improve power generation efficiency, module cleaning and land conservation. In deeper waters with depths of over 3m, floating PV plants are recommended. Floating PV power plants use floating buoys to withstand the weight of the solar panels and related equipment, with floating buoys fixed onshore and underwater. Floating systems can be divided into two kinds: floating body + bracket + solar panel and floating body + solar panel.

��'��-Principle: Components are supported on the bracket, the bracket is fixed to the pile and the pile placed in the water��'��@�� '��?��-Advantages: Simple construction, wide applicability, attractive construction cost, fast construction speed, water area can also be used as fish pond, high economic efficiency��''��?�� '��-Technical requirements: Use prefabricated pipe piles and terminals to construct PV mounting system. mounting system. Pile diameter to be determined in accordance with engineering conditions-Combiner box: Installed at the back of the PV bracket-Inverter: String inverter are installed on the PV rack; Centralized inverters are installed on shore or off shore based on the distance-Container transformer: Installed on shore or off shore based on the distanc


57

Figure 3.17 Pile foundation based PV plant

�� ' ��'�� £�@��#��£�*}�'��-Principle: Through the design of a reasonable floating buoy, the panels will be installed in the bracket, the bracket fixed to the floating body with buoys floating on the water, then the floating body is fixed. Main components are floating buoys, bracket and the floating platform of the PV system-Advantages: Can be arranged according to the best inclination and can increase the amount of electricity�� @� ��

Figure 3.18 Floating power plant

Floating buoys need to be flexible to allow changes to the water level, but need to be prevented from touching the shore. The distance of the floating body from the shore and the water depth should be used to determine the way to fix the buoy:

�� @� �� @�� @� �� @� �� '��@�� @� �� '��

3. The Development of The Energy Internet and Energy Storage

With continuous decrease of cost in the recent year, solar PV energy becomes more and more attractive in regions of higher electricity cost or electricity shortage. . The phenomena results in the adoption of new policies and regulations in markets such as India, South-East Asia, South America etc, help the solar industry flourish. Solar PV power will become globally mainstream in the future. We believe the direction of the solar industry in the future will be: “PV + Internet” and “PV + Energy storage” for this intermittent energy to be fully and efficiently used in high penetration.


58

3.1 “PV + Internet”

The following is a brief introduction on how the Internet contributes to an intelligent network of solar power generation and its management and maintenance.

3.1.1 The Energy Internet optimizes the consumption of solar power

The Energy Internet is a highly automated power transmission system which covers the whole process from power generation to end consumption. With the support of high-speed Internet and through advanced information systems, power measuring and grid control technologies, the Energy Internet can become a highly integrated system for power operation. This type of intelligent network is safe, reliable, economical, efficient, clean and interactive. It can monitor and control the circumstances of every end-user and key ��{�|��<��' ��' ��''��?� �� capabilities to power systems, manage relationships between the supply side and end consumers, and protect against network attacks.

Figure 3.19 Illustration of intelligent power network

|�� <��<� �� ?�� {�<� �� technology allows information to be collected, shared and utilized in real-time. Automation is needed for control and operation, and interaction makes the dialog between supplier and end users possible. The construction of the intelligent network is an ensured step to let the solar PV power be accepted and connected into the power grid. It is also an important milestone to promote the development of solar PV power industry.


59

3.1.2 Technology Of Intelligence Operation And Diagnostics Based On Large Data Base In Cloud System

Figure 3.20 Smart O&M schematic

The network monitoring technology based on cloud systems can implement the need of maintenance and collection of data information and control. The cloud system can also provide the capacity for large data storage and analysis, diagnostics capabilities, remote problem analyses and resolving. It helps to detect the ��'�� '��*<�� {�|�� @�� ' �� ]��]�� ' ��' ��{

3.2 “Solar PV Power+Power Storage”

In solar power generations, the energy storage takes the functions of the modulation of peak power output and its frequencies. This can also help the completeness and integration of micro solar power system. With the storage application, the power system can further reduce the waste of solar power during its peak hour generation. The distributed generation of power system plus storage becomes one of the mainstreams under fast development recently.

Figure 3.21 Distributed energy storage system

��'��center

Visitor & Operations staff

PC

Leadership, the owner, operations staff, analyst etc.

APP

Leadership, the owner, operations staff, sales service etc.

Smart O&M Smart city or other data center

PV power plant

PV moduleMonitoring software��#

PV moduleMonitoring software��#

PV power plant


Power SationESS

Wind Power

Solar Power

Hospital (with own generator)

Smart-office building(with hydrogen-car generator)

Apartment buildings

60

3.2.1 Modulation of Peak Hour Output And Frequencies

The installation of energy storage in solar PV power generations system can make the power output to effectively respond to the automation generation control system (AGC) to realize the flat curve of frequencies and power output.

AGC can modulate in real time the frequencies of power output to resolve the issues of randomly unbalanced power output. The biggest advantage of an energy storage system is that it can modulate the power output quickly and accurately. It can respond within one second to the instruction from AGC which is 60 times faster than thermal power generation. The energy storage system can help balance the generation and consumption sides in the power network by fast charging and discharging. It can also modulate the frequency fluctuations by controlling the speed of power charging and discharging.

Figure 3.22 Energy storage technology applications

3.2.2 Intelligent Micro Grid

With the gradual increase of percentages of solar and wind powers in the power market, the power network has been faced with increasing challenges in the areas of network safety and efficiency in operations. Energy �� '' �� '�� '�� '��efficiency in power generation, transmission, distribution and consumption. It gradually becomes one of the key components in the intelligent network.

Figure 3.23 The illustration of intelligent micro gridS


Storagebattery

Solar

micro

inverter

PV module array

61

3.2.3 The Solution of the Reduction The Waste of Solar Power Generation

In 2015, the northwestern area of China came with the situation of increasing the waste of solar energy generations. Accumulated 2600 million kWh were wasted which took a 31% of the total generated in Gansu * ��{�[\]]�� #;�� <��{�|��'' �� the storage capacities can store the output power during the low consumption load periods and discharge in peak hours. The approach can effectively increase the efficiency of the power generation management.

Table 3.4 The wasted PV power in China in 2015

�� ][~�� @��' �� '�� ' �

Figure 3.24 The storage system of solar PV power generation

3.2.4 Distributed Generation of Solar Power + Household Storage

In recent years, we see the significant increase of solar power installation, the decrease of governmental subsidized programs, the decrease of the cost of energy storage systems, and the annual progressive increase of electricity prices. We also see the significant increase of deployment of household energy storage systems. As predicated by GTM Research, Australia will have installations of energy storage 20 times more in 2016. In 2020, the annual energy storage installation will reach 244 MW and the residential and commercial installations will take up about 90%.

Province

Gansu

��

Ningxia

Qinghai

Total

Power quantity (106 KWh)

2600

1800

300

200

4900

Rate

31%

26%

7%

3%


62

Figure 3.25 Australia distributed energy storage for 2013 – 2020


Tesla of USA and Sonnen Batterie of Germany are both current outstanding performers of the technologies of household energy storages. Sonnen Batterie takes a market share of 30 - 40%.

Figure 3.26 Tesla (top) and Sonnenbatterie (bottom) energy storage products

Canadian Solar Inc. is one of the earliest companies that conduct researches and develop household energy storage systems and it has brought its household storage products in Japan and Australia.

0

50

100

150

200

250

300

2013 2014 2015E 2016E 2017E 2018E 2019E 2020E

Residential Non-residential Utility-scale


63

Figure 3.27 Canadian Solar Inc. household storage

3.3 The Development of Energy Storage Technologies

Energy storage is widely used in solar power business, including generation, transmission, distribution and end user consumptions. The technologies used for energy storage in power grid system are typically in the following categories: water pumping, air compression, chemical battery storage and super capacitor storage. Except for the energy storage of water pumping which is fully mastered, the other technologies are still in the early stage for practical use or even in the stage of research and development. In order to increase the energy efficiencies, promote the renewable energies development, and optimize the existing power systems, the �� '�' ��' �� '' �� '�� ?�which include tax reduction, one-time financial support, grant permit to solar industries to compete electricity markets and so on.

3.3.1 Technology Approaches and Analysis

<��?��#�� #��'�� '��{�>�� @�� @�� @��'�� >��[�?��][�?�� @�� [`�{]`��;�� [?�[��' ��!{�>� ��?��'��'�� #��[\�{\��;��~��' ��!?�� #��{��;��]~�' ��!?� �� #��{�[��;��]�' ��!?�� #��{]��;��`��' ��!?�� #��]{][\��;��[��' ��!�� '��#��]{]]~��;��' ��!{

Figure 3.28 The number of global total installation of energy storages in 2000 – 2016

water pumping storage95%

�� 2%

Mechanical energy storage1%

Electrochemistry storage2%

193GW


64

The energy storage deployment in China market has a promising future. According to the Plan of 2016 – 2030 of Innovation and Actions of Energy Technologies report, by year 2020, the energy storage system of 10 MW/100 MWh of compressed air technology, 1 MW/1000 MJ flying wheel array system energy storage technology, 100 MW vanadium liquid battery system technology, 10 MW sodium sulfur battery system and 100 MW lithium ion battery storage technology will all be demonstrated and promoted in China. From economic perspective, the cost of energy storage systems will be decreased quickly with the increase of the power generation scale, with shorter cost recovery period which will push the cost close to the breakeven point. It is predicted that the capacity of energy storage market will exceed 50 GW in 2020 in China.

3.3.2 Analysis of Energy Storage Technologies

The current technologies of energy storage can roughly be categorized in 5 areas:· Mechanical (water pumping, air compressing, flying wheel)· Electrochemistry (lead battery, lithium ion battery, high temperature storage and liquid battery)· Electrical (super capacity, super conductivity)· Chemistry (Synthetic natural gas, electrolysis water)®�� ?�� '�� !

Figure 3.29 Categories of energy storage technologies

Figures from Energy Storage Study from AECOM Australia Pty Ltd，2015

· Water pumping technologyWater pumping technology is the use of pumping water upwards when the grid is on low consumption load while releasing water downwards to generate power when the grid is on peak consumption load.

· Advantages: Reliable, economical, long usage life span and large power volume capacity.®�� @�� ?�� '�� loss.

· Lead battery storage technologyLead battery is made of positive array of lead penal, negative array of lead penal, electrolysis liquid and the container. The technology has a history over 150 years with proven reliability and maturity. It is the most widely used chemical electric storage in the world. The most popular places of using this type of batteries are automobiles and motorcycles. · Advantages: Cost is lower than other electrochemistry batteries and the state of discharge is comparatively stable.

®�� ' ��?�� {

Energy storage technologies

Electrical

Chemistry

�� Electrochemistry

Mechanica


65

· Lithium ion battery technologyIt is composed of lithium metal or lithium alloy metal and non-water electrolytes liquid.

®�>��?��@�� ' ��{®��'��?�' ��@��' @�� @��{

· Electrochemical flow battery technologyIt is a battery to separate positive and negative electrolytic solutions that has its own separate circulation with high efficiency.

· Advantages: Large storage capacity, high efficiency and capable of deep discharge®��?�� '�� '��{

· Super CapacitorComparing with normal capacitors, the super capacitor has higher dielectric coefficient, larger surface area size or electric voltage endurance. The whole process of energy storage does not involve chemical reactions.

· Advantages: Short recharging time, long life of usage, stable temperature performance and environmental friendly. ®�� ?�' �� '�� '�� materials like graphene.

3.3.3 The Development Of Energy Storage Technologies And The Areas Of Applying

Water pumping is the one of the energy storage technologies that is most widely used, most reliable and the ��' ��'��{�� '��years. The electrochemistry energy storage technology is the fastest in development globally and also the � �� ' ��' ��{�>�� '��under stable development and the new technologies like hydrogen storage and graphene storage begin to enter markets in recent years.

Figure 3.30 Distribution of technologies of energy storage


Based on the difference of the characteristics of different technologies (the total number of discharging, the size of megawatt and efficiencies), the applications of the technologies will be decided by different circumstances. The water pumping and air compressing technologies have the capabilities of discharging energies in large volume which can satisfy the requirement of large scale solar power plant although they have low efficiency rate (70% – 85% for water pumping and 45% – 70% for air compressing). Super capacitor and flying wheel technologies have the advantages of quick energy discharge, but their power capacity is low .

Legend

Synthetic natural gas

Research

Cap

ital r

equi

rem

ent T

echn

olog

y ris

k

Development Demonstration Deployment Mature Technology Time

HydrogenAdiabatic CAES

Supercapacitor

Flow batteriesLithium-ion batteries

Molten saltFlywheel(low speed)

Sodium-sulfur(NaS)batteries

Compressed air energyStorage(CAES)

Pumped hydro storage(PHS)

Superconducting magnetic energy storage(AMES)

Mechanical storageElectro-chemical storageThermal storageElectrical storageChemical storage


66

Electrochemical batteries are the most popularly used energy storage technologies. They have the capacities of quick response time, large discharging volume under modular combination and high efficiencies (85% -100% for lithium ion battery).

Figure 3.31 The deployment of different technologies


Fast Response Systems Grid Support and Balancing

�is

char

ge T

ime

at R

ated

Pow

er

�ou

rsM

inut

esSe

cond

s

Typical Efficiency 45-70% 70-85% 85-100%

1 KW 10 KW 100 KW 1 MW 10 MW 100 MW 1 GW

Lithium ion

Lithium ion

Flow Batteries

Advanced Lead

Fly Wheel

Super Capacitor

Compressed Air Energy Storage

Pumped Hydro Storage


67

IV.SUMMARY

As predicted by ITRPV, the photovoltaic conversion efficiency of cell can reach as high as 26% by 2026. The average power output of a 60-cell panel will go over 310 W while the average power output of a 72-cell panel will break 370 W.

Figure 4.1 Prediction of photovoltaic conversion efficiencies of cells by types for 2015-2026

Source: ITRPV 2016

Figure 4.2 Prediction of module power of the most popular 60/72 cells solar panels for 2015-2026

Source: ITRPV 2016

With the obtainment of higher photovoltaic conversion efficiencies by the development of technologies and the decrease of materials cost, the cost of solar power generation keeps going down. By the prediction of IRENA, the cost of PV will decrease by 50%, leading to the range of US$0.03 – 0.12/ kWh, which will result in solar power generation close to generation side grid-parity in most areas on earth.

240

260

280

300

320

340

360

380

400

2015 2016 2018 2020 2023 2026

60-cell module

72-cell module

SUMMARY

17%18%19%20%21%22%23%24%25%26%27%

2015 2016 2018 2020 2023 2026

BSF p-type cells mc-Si BSF p-type cells mono-SiPERC/PERT cells p-type mc-Si PERC/PERT cells p-type mono-SiPERC,PERT or PERL cells n-type mono-Si S�J cells n-type mono-SiBack contact cells n-type mono-Si

68

Figure 4.3 Prediction of the cost of KWh of large scale solar farm during 2010-2025

Source: IRENA 2016

2016 is a historic year. In the world, the PV LCOE has reached or even lower than the user side electricity price, ahead of 4 years to reach the user side grid-parity, compared with the general forecast of 2020 years. This is the result of numerous tireless efforts and constant technological innovation by our many PV associates. Looking to the future, there is still a great potential to increase efficiency and reduce costs for photovoltaic system, such as the fluidized bed polysilicon, continuous mono crystal pulling, diamond wire cutting, black �� ?��*��?��'��?�� @�� ?�� ?��<�� ?�tracking system, water surface PV plants, PV energy storage and many other new technologies to further enhance and popularize, it will promote and guide the PV cost reduction,achieving the same cost with the wind power by 2018 and the coal based thermal power by 2022. Solar energy into every household is the vision of each PV practitioners, it will also become a reality in the near future!

SUMMARY

69

SUMMARY

70�� ' ��?�*�� * ��*��?�� >

SUMMARY

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