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Prof. YANG Hongxing

Renewable Energy Research Group (RERG)

Department of Building Services Engineering,

The Hong Kong Polytechnic University

13-12-2018

Development of building-integrated photovoltaics for solar energy applications

Contents

Development of solar PV power in the world

Potential PV and BIPV applications in the

future

Study on PV integration in vertical PV wall

Study on PV integration in windows

Conclusions

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Annual PV installation 2000-2017（MW, DC）

• Total annual installation in 2017: 98GW• Annual installation in China in 2017: 53GW，

54% of the world total

Accumulated PV capacity 2000-2017（GW, DC）

At end of 2017: 402,5 GW.

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Until 2017，Asia contributes 54.5% to the total PV capacity, which is still growing；Percentage of PV in Europe is declining: 28% in 2017；American continent: 19%.

Total regional PV capacity 2000-2017（GW, DC）

Top 10 countries of PV installation in 2017（GW）

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>5%: 6 countries；

>3%: 15 countries；

>1%: 29 countries；

Honduras: 13.26%；

Germany: 7.47%；

Greece: 7.34%；

Europe: 4%；

China: 3%。

Percentage of power generation in 2017（%）

In 2017:

• Monocrystalline:45%；

• Poly-crystalline: 51%；

• Thin film: 4%。

Type of PV modules 2007-2017（%）

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• The cost has been decreasing, from 4700€/kWp in 2016 to 1100€/kWp in 2017.

• PV module cost is decreasing• BOS’ percentage is increasing。

PV system costs in Germany

Average PV module cost: 0.53$/W in 2016 to 0.34$/W in Oct 2017.

Indian PV costs

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PV costs in different regions and countries (2016)

Item Mainland China Germany USA Hong Kong

PV module (HK$/Wp) 5.74 7.8 7.8 7.8

Inverter (HK$/Wp) 0.8 2.6 3.3 3.9

Other devices (HK$/Wp) 1.6 1.8 3.6 12.4

Profit (HK$/Wp) 1.9 4.8 25.9 19.4

Installation (HK$/Wp) 10.0 16.9 40.5 43.4

Solar radiation (kWh/m2 Yr) 1000-2000 900-1200 1200-2400 1350

Energy cost (cents/kWh) 47.8 100.8 150.5 202.2

PV installation and power generation in 2022

In 2020，world PV installation capacity: 700GW, and power generation: 730TWh；In 2022，wolrd PV installation capacity: 860GW，and power generation: 900TWh.

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In 2035，0.3USD/W --0.4USD/W.

PV module cost in 2035

In 2050, total power will be 6300TWh, 16% of the total power consumption.

Prediction of PV power until 2050

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Prediction of energy resource structure

From German Advisory Council on Global Change （Title：World in Transition –Towards Sustainable Energy Systems, Flagship Report 2003）.

Rapid development of PV power in China

The 1GW PV project at Zhongwei City, Ningxia, China

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Future trend of solar photovoltaic applications

——Building integrated Photovoltaics (BIPV)

BIPV：refers to using photovoltaic materials, viz. solar cells and PV modules, to replace conventional building materials in parts of the building envelope such as the roof, skylights, windows or facades where the PV modules simultaneously serving as building envelope material and generating power.

Functions of BIPV

Power generator

Part of construction materials

Water proof

Shading

Noise barrier

Insulation

Natural lighting

Future trend of solar photovoltaic applications

——Building integrated Photovoltaics (BIPV)

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Future trend of solar photovoltaic applications

——Building integrated Photovoltaics (BIPV)

Advantages of BIPV

Power generation from renewable energy: clean and CO2

emission reduction;

No need of expensive land is used in urban areas;

Reduction of construction cost due to replacement of cladding;

No power transmission is needed and power is used in the building;

Peak power demand is reduced as solar power is generated when needed;

Cooling load and lighting load may be reduced.

An overview of applications of PV modules in buildings.

BIPV applications

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BIPV projects-rooftop

斜屋顶

平屋顶

BIPV projects: semi-transparent facade

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BIPV Projects

Skylight and atrium

Shading type

1MWp solar roof project in Shenzhen

Shenzhen World Garden Flower Exhibition Park

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Installation capacity: 10.67 MW.(The biggest single BIPV project in the world)PV module type: Poly-Si

BIPV of the South Railway Station in Nanjing

Annual energy output: 9.12 GWhAnnual CO2 emission reduction: 9000 tons

BIPV of the Museum of Natural Science in Jiangxi

Installation capacity: 3.05 MWPV module type: a-Si hollow PV moduleInstallation method: BIPV on facades and roof

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BIPV of Zhujiang City in Guangzhou

Installation capacity: 185 kWPV module type: a-Si PV moduleInstallation method: BIPV on the east and west facades

BIPV in Huangshi of Hubei

Installation capacity: 3 MWPV module type: Poly-Si PV moduleInstallation method: BIPV on facades, roofs and shading panels

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BIPV of Hanergy in Jiangsu

Installation capacity: 67 KWPV module type: a-Si PV moduleInstallation method: BIPV on facadesAnnual energy output: 33919 kWhAnnual CO2

emission reduction: 10 tons

New BIPV claddings from Hanergy

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BIPV applications in Taiwan

1MWp at Kaohsiung National Stadium (2009)

PV in Hong Kong

Advantages of BIPV

•No land use;

•BIPV provides electricity at the point of use;

•The PV elements become an integral part of the building and reduce building material use;

•Power is generated on site;

•Cooling load can be reduced;

•Renewable for low-carbon emission buildings.

EMSD HQ in Hong KongPolyU in 1999

Lamma Power Plant

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BIPV in Hong Kong:Wai Chai Tower BIPV project

Year of installation

2002

Power capacity

55 kWp

Type of integration

Vertical façade; semi-transparent modules; roof integrated modules

The BIPV systems in the Science Park: •roof integration, •sun-shaded type and façade integration

The BIPV projects in the Science Park

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Government building

EMSD Headquarters at Kowloon Bay (350 kW)

PV modules: DuPont (Amorphous thin film)

Developer: HK Electric

The Largest PV installation in Lammar Island:

1.0MWp

Amorphous silicon photovoltaic modules of 5,500 pieces and 3,162 amorphous/ microcrystalline silicon tandem junction TFPV modules;

Total generating capacity of 1 Megawatt and is expected to generate 1,100,000 kWh

Reduce 915 tonnes of carbon dioxide emission every year;

Capacity Factor – 12.9%

Design life – 20-25 years

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Details of the FiT in Hon Kong

Capacity of the Renewable Energy System

FiT rate(per unit of electricity -kWh)

≤ 10 kW HK$ 5

> 10 kW - ≤ 200 kW HK$ 4

> 200 kW - ≤ 1MW HK$ 3

Three types of FiT rates will be offered according to the installation capacity of your RE system:

The rates listed above are effective from 1 Oct 2018 onwards and will be reviewed regularly.

BIPV potential study in Europe

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1. Rooftop installation potential & PV output

The potential total active rooftop area of PV modules was calculated as 37.4km2. The total potential installation capacity is estimated as 5.97 GWp.

The potential PV electricity output is about 5,981GWh,accounting for 14.2% of the total electricity use in 2011.

Reduce the imports of coal and natural gas by 25% and 54% respectively and mitigate about 3 million tons of GHG emissions yearly.

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With an average global CAGR of 39% during 2014–2020, the annual global BIPV installation in 2020 is anticipated to be 11 GW.

Source: (Global Industry Analysts, 2015)

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The total installed BIPV capacity in Europe will be 4.8GW in 2020!

European market analysis and forecast

Source: (Global Industry Analysts, 2015)

Current and forecasted BIPV penetration within the PV market for the period 2014-2021

The global BIPV sales will triple by 2019, growth by 18.7%;Currently the BIPV market holds a market share of around 2% of the overall PV market, 13% by 2022.

Source: Nanomarkets , “Nanomarkets report BIPV Market Analysis and Forecast 2014-2021,” 2015.

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BIPV market

The most evolved BIPV market regions are Europe and the USA which combined currently account for around 70% of the worldwide market share.

Source: Nanomarkets , “Nanomarkets report BIPV Market Analysis and Forecast 2014-2021,” 2015.

Main applications for BIPV: roofing, walling and glass

For 2020, around 3.5B€ will be invested in BIPV roofing in each Europe and USA, with a total worldwide BIPV annual investment exceeding 10B€.

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BIPV Glass

The total worldwide demand for BIPV glass will increase from €1B in 2015 to €6.3B in 2022. Europe will still be the largest market and will remain so through most of the forecast period 2015-2021.

BIPV Walls

In agreement with the other BIPV markets, Europe and the USA are and will be the regions leading the market. The total BIPV walling market will exceed €5B by 2021.

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Our research in BIPV in Hong Kong

Study of the overall energy performance of BIPV facade: real-time power generation performance thermal performance natural lighting performance

(1) Solar PV windows

Airflow and heat transfer in open/close cavity

0 xT

0 xT

VY ,

UX ,TVU ,,

Transparent PV module

Close cavityClose cavity

Open cavityOpen cavity

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Structure of the ventilated PV-DSF

Constituted by:• a-Si PV laminated• inward opening window• airflow cavity• air louvers

Advantages of the design: air exchange & solar passive heating improved daylighting performance ventilation design

• reducing cooling load• enhancing PV energy efficiency

Annual overall performance in Hong Kong

The maximum monthly energy output : 5.6 kWh/m2

Annual energy output: 38 kWh/m2

Saving cooling energy use: 70 kWh/m2/yr.

Lighting can be powered by the PV-DSF itself in winter.

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Cooling electricity use

PV-DSF 6 mm clear glass

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BIPV test bed at Tung ChungPV shading

PV-IGU

PV-DSF

Experimental studies

The Housing Authority BIPV project

• Roof integration

• PV walls

• PV windows

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Study on semi-transparent solar PV windows - Data acquisition system

Efficiency: 6.3%Transmittance: 20%Rated power: 63W/m2

Efficiency: 6.8%Transmittance: 20%Rated power: 68W/m2

Ventilated PV window

Hollow PV window

Study on semi-transparent solar PV windows

- Inside views of PV windows

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(2) Energy performance of PV DSF and PV IGU

The heat transfer model, daylighting model and PV power generation model in EnergyPlus were adopted to investigate the corresponding performance simultaneously.

PV double skin façade PV insulating glass unit

PV glazing Inner glazing

Outdoor Indoor

PV-IGU

Structures of PV-IGU and PV-DSF

PV-DSF

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PV-IGU PV-DSF PV shading

Power output of PV-IGU on a typical sunny day Power output of PV-DSF on a typical sunny day

Power output of solar PV shading on a typical sunny day Monthly power output of PV systems

Experimental studies

Simulation tools: Berkeley Lab WINDOW, EnergyPlus

A generic representative model

Continuous dimming control

Sandia Array performance Model• Empirical-based• More accurate for thin-film solar cells

（3） Single-glazed PV glazing VS energy-efficient glazing

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1) Significant difference among different months: more in winter and less in summer.

2) Annual electricity output varies with orientations: SW > SSW > WSW > S > … > E

Monthly power output per unit area of south facing solar PV windows

Annual power outputs per unit area of solar PV windows in different orientations

Power generation performance in Hong Kong

Single-glazed PV glazing VS energy-efficient glazing

Glazing type PV-I PV-II PV-III

Transmittance (%) 10 20 30

Maximum power, Pm (W) 58 51 44

Maximum power voltage, Vm (V) 69 69 69

Maximum power current, Im (A) 0.84 0.74 0.64

Open circuit voltage, Voc (V) 89 89 89

Short circuit current, Isc (A) 1.01 0.89 0.77

Fill factor, FF 0.64 0.64 0.64

Efficiency, η (%) 7.3 6.5 5.6

Temperature coefficient of Isc (%/˚C) 0.02 0.02 0.02

Temperature coefficient of Voc (%/˚C) -0.20 -0.20 -0.20

Temperature coefficient of Pm (%/˚C) -0.19 -0.19 -0.19

Dimension 1.245 m * 0.635 m

Electrical properties of PV glazing

Energy performance of PV-IGU

Simulation setup – glazing materials

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Energy performance of PV-IGU

Annual PV power output

Location: Beijing > Harbin > Kunming > Shanghai > Hong KongHigher transmittance → Lower power output

MBE(%) = 3.4%CVRMSE = 23.7%

MBE(%) = 3.4%CVRMSE = 29.1%

MBE(%) = 5.0%CVRMSE = 29.8%

Energy performance of PV-DSF

Test bed Simulation model Window heat gain

Daylighting illuminance Power output

Model development and validation

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Energy performance of PV-DSF

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Harbin Beijing Shanghai Hong Kong Kunming

PV-DSF PV-IGU

Energy saving potential of PV-DSF and PV-IGU compared to reference window

-6%

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PV-IGU

PV-DSF

57%

52%

4. Energy saving potential of solar PV shadings

Research gap• Daylighting performance is rarely considered in previous studies. However,

both external and internal shadings affect the daylighting performance of the room.

• Comparison between external solar PV shadings and interior shading devices has not been reported yet.

Due south, Tilt angle: 55˚, Error: 5%Simulation model of solar PV shadings Validation of the electricity output

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Best orientation: South

S>SE>SW>E>W (tilt angle<30˚)S>SW>SE>W>E (tilt angle>30˚)

Optimal tilt angle: 30˚Annual electricity generation of solar PV shadings

Energy saving potential of solar PV shadings

43 kWh/m2

Power performance

5. Advanced VPV IGU

• A novel vacuum PV insulated glass unit (VPV IGU) is proposed to combine

the advantage of the high thermal insulation performance of vacuum glazing

and the power generation capability of STPV windows.

The structural details of VPV IGU

The cross-section of VPV IGU

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Results and Discussion

• The average U-value is calculated as 1.5 W/m2*K which is much lower than

common double pane window with the U-value of 2.5W/m2*K.

• Considering the edge heat transfer which would strongly affect the heat flux

measurement when the sample is small, it can be expected that the center U-

valve of vacuum PV glazing should be lower in a large-scale application.

Power generation Performance

• The difference of the power generation among different BIPVsystems is less than 1%, and the single-pane PV glazingproduced the most electricity output.

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2. Development of self-cleaning nano-coating for PV

Super-hydrophobic , θ(Lotus leaf):>150°

Super-hydrophilic，θ（clean glass surface）:<10°

Super-hydrophobic self-cleaning glass

Super-hydrophilic self-cleaning glass

Advantages of our product: Superior self-cleaning property and cheaper cost

The comparison between two PV modules after twomonths. The self-cleaning coating has superior super-hydrophilicity.

With self-cleaningcoating

Without self-cleaningcoating

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Conclusions

• Solar photovoltaic develops very fast. The cost is nearlyclosing to traditional energy resources for power generation.

• BIPV represents the future of renewable power generation inurban areas.

• Introduction of the FiT leads to bright future for BIPV inHong Kong, but long-time policy is necessary and offshorewind power should be included.

• Vacuum PV glazing façade has the lowest U-value as well asSHGC compared with double-pane glass, double PV glazingand pure vacuum glazing.

• All types of the PV-IGU can achieve significant energysaving potential compared to reference IGU in all climatezones in China.