🗊Презентация Lecture # 11 PV1. Solar Photovoltaics, AUA Solar System

Solar Photovoltaics, AUA Solar System IE350

Photovoltaics - PV Photo Voltaic effect – phenomenon, when light energy directly converts into electricity. First was detected in 1839 by French physicist Alexandre-Edmond Becquerel. A quintessential source of energy – operation is absolutely clean environmentally, no moving parts. However its production process is not perfect, but overall PV performs environmentally much better than any other source.

Trend: PV capacity growth EPIA - European Photovoltaic Industry Association - forecast 2014-2018

Photovoltaics: Principles Introduction - Quantum mechanics Physical principles of Photovoltaic (PV) Conversion Efficiency, degradation, price Various realizations: - flat panel - concentrator - tracking/non-tracking Materials: Si, Thin film

Popular Quantum Mechanics Interference of Particles. Bohr’s model of atom. Energy states in a crystal. Metals, semiconductors, insulators. P-N-Junction PV modules PV system components.

Electromagnetic (EM) radiation

Dualism of EM radiation EM radiation exhibits both wave behavior and particle behavior

Double slit experiment LIGHT

Double slit experiment Electrons

Bohr’s model of atom.

Electron can change its “orbital” by receiving or releasing a photon or thermal energy.

Absorption only happen if the photon energy match the atom’s energy discrete values! Emission generates a photon with strictly discrete value.

Atom Energy Levels Isolated atom’s energy levels correspond to the orbitals The Pauli exclusion principle is the quantum mechanical principle that states that two or more identical fermions (particles with half-integer spin - electrons in our case) cannot occupy the same quantum state within a quantum system simultaneously.

A system of two atoms N=2 Energy levels are split into two levels

N – atom system

Solid body – crystalline lattice:

When N >>, e.g. in solid bodies, 1023 atom per cm3.

Electronic Energy Bands In solids the atomic energy levels turn into bands

Metal vs. Semiconductor, vs. Insulator

At non-zero temperatures,

Silicon crystal structure

P-N-Junction P-N-Junctions have the ability to form built in electric field in the space charge region.

PV power generation

Now, what will happen if a semicon-ductor structure’s p-n-junction is bombar-ded with photons?

P-N-Junction The interface of the p-doped and n-doped semiconductors is called P-N-Junction P-N-Junction in fact is a diode P-N-Junction has a built in electric field, without spending any electric power P-N-Junction electric field separates the photogenerated electron-hole pairs, and creates external voltage and current.

Summary of physical principles of Photovoltaic (PV) Conversion

P-N-Junction

PV power generation

Light emission diode = LED LED performs the opposite function – converts electric power into visible light. Conversion is performed due to recombinative radiation

Sensitivity Spectrum Why PV cells are sensitive to light spectrum? What will happen if a photon, with energy of h ≤ Eg will hit the semiconductor? Semiconductor will be transparent to this radiation.

Sensitivity Spectrum – via wavelength or equivalent via photon energy

Summary of physical principles of Photovoltaic (PV) Conversion

Summary of physical principles of Photovoltaic (PV) Conversion

Factors Influencing Efficiency Semiconductor related Percentage of spectral overlapping Quantum efficiency, Absorption depth vs. p-n-junction depth and thickness Recombination of electrons and holes in the bulk of Si: diffusion length L or lifetime . The reverse current in the p-n-junction, because of recombination

Percentage of spectral overlapping

Spectrum vs. Energy

Absorption depth vs. p-n-junction depth and thickness

Recombination of electrons and holes

The reverse current in the p-n-junction – defects inside SCR that enhance recombination, i.e. loss of electron-hole pairs.

Shockley-Queisser Limit

Factors Influencing Efficiency Factors outside the semiconductor Surface reflectance Shading by collecting electrode, effective surface. Optical Fill Factor (OFF). Unbalanced load – non-maximal power point. Electrical Fill Factor (EFF).

Surface reflectance By the semiconductor surface By the weather encapsulation By the low-iron, tempered glass Anty-reflective coatings decrease the reflectance but are expensive.

Optical Fill Factor (OFF) The area that is open for the radiation Shading by collecting electrode Effective surface of the module Distance between modules Distance between rows in the solar field The solar system total area

Electrical Fill Factor (EFF) is the Preal/(IscVoc), Isc = short circuit current, Voc = open circuit voltage

Max Power Point

Organic PV cell test, AUA

Types of Solar Converters Crystalline Silicon: Single-crystal (c-Si) – eff 22% Crystalline Silicon: Multi-crystalline (mc-Si) or Poly-crystalline Si (poly-Si) – eff 17% Amorphous Silicon (Si-A) – eff 9%, degradation. All Si technologies make 86% of the market. Thin Film: CdTe is easier to deposit and more suitable for large-scale production. Eff = ususally 6%-10%, up to 15.8% in experiments. Copper Indium Gallium Selenide (CIGS) are multi-layered thin-film heterojunction composites. 19.5% Potentially up to around 30%, could be put on polyamide base. Multijunction stacks - Gallium arsenide (GaAs), eff = 47%!!! - space applications. Albeit extremely expensive, - thus uses in the concentrated PV

PV cell materials in the market Market share percentage of PV cell technologies installed in Malaysia until the end of December 2010 Production by country, 2012

PV cell materials in the market Market share percentage of PV cell technologies installed in Malaysia until the end of December 2010 Production by country, 2012

Efficiency In 1884 the first Selenium Solar cell had 1% efficiency. The theoretical maximum is 64% for stacked PV structures! The real, economically productive values are 16% - 24%.

Stacked multi junction solar cells

Stacked multi junction – MJ – solar cells

Components of the PV System Photovoltaic (PV) panels Battery Bank Charge controllers Invertors Load

PV System calculation approach for net metering case Find out from your monthly bills your total annual kWh-s of consumption - Ee. Find out your local monitoring data – amount of global horizontal (GH) kWh-s (Em). At tilted angle (30⁰ for Yerevan) you can have more than 20% advantage, reaching 1800 kWh/m2 annually. However due to shading or other losses – you will need to make an assessment – you can take for Em e.g. 1500 kWh/m2 for calculation. Remember that since @ 100% efficiency your modules 1 m2 corresponds to 1 kW of rated power, the Ee/Em = PS your needed system power capacity. E.g. @ Ee= 3000; Em e.g.= 1500 kWh/m2 annually, PS = 2 kW. Here 1500 kWh/m2 is replaced by 1500 kWh/kW. Homework: calculated the price of your system, look at previous slide.

Types of Solar Converters Photoelectrochemical cells – now up to eff of 10% in experiments. Polymer solar cells = 4-5% nanocrystal Si (nc-Si) solar cells, quantum dot technology

Concentration PV Photovoltaic concentrators have the added benefit of an increase in efficiency due to the nature of solar cells. Commercial solar cells operate with an efficiency of around 15% in standard sunlight, however when the sunlight is concentrated the efficiency can go above 21%. Concentrators reduce the cost. Solar cell are fairly expensive, however mirror and optics are much cheaper. So a small solar cell concentrated can produce more energy with mirrors or optics than the equivalent area with a larger solar array.

Multi-junction Solar cells under illumination of at least 400 suns, MJ solar panels become practical

Amonix concentration systems

BIPV

BIPV Similarly, if it is possible to use part of the windows or glazing of the construction to integrate PV cells inside, one can avoid paying for the PV modules’ glazing the second time, as well as economize on the support structure. At the same time the Integrated PV is an innovative, aesthetically interesting element that can be a part of the architectural idea - recently popular PV module placement location is the south facing portions of the building envelop, perfectly helping to address both economizing dimensions of the integrated PV.

Efficiency In 1884 the first Selenium Solar cell had 1% efficiency. The theoretical maximum is 64% for stacked PV structures! The real, economically productive values are 16% - 24%.

2009 vs 2003

03 November, 2011

20 November, 2012

11 November 2013

November 2014

November 2015

How to compare solar cells? Efficiency Longevity – time to degradation Peak watt price

Notion of the peak power price (PPP) Price of a cell, module or a system, per conditions when the solar illumination in normal incidence is equal to standard reference radiation, 1000W/m2, in $/Wpeak. Note that this is more important than the solely the efficiency. Correct way of comparing the prices of various solar options – for any technology. Is there a peak watt notion for wind?

How to compare PV cells, modules? Peak power price - $/Wp. Lifetime – years before substantial degradation, e.g. 15% Efficiency, %

PV module cost per peak watt

PV module cost per peak watt – logarithmic

2004 world status of PV industry.

Types of Solar Converters Photoelectrochemical cells – now up to eff of 10% in experiments. Polymer solar cells = 4-5% nanocrystal Si (nc-Si) solar cells, quantum dot technology

PV manufacturing from Ore to Cells. Silicon resource, abundant, but… … stringent requirements to the ore Metallurgic silicon Silane gas Poly-Silicon Czochralsky (CZ) method Other methods New alternate methods

Realizations Fixed tilted flat panel Concentration PV (Tracking systems) Integrated PV

PV systems

PV standalone solar system

PV grid connected solar system

PV grid connected solar system

AUA SPVS general information Each panel has approximately 0.7 square meters surface and 70 watts of peak power The 72 solar photovoltaic panels are installed on a special earthquake resistant structure Total battery bank storage is 1150 amper hours at 48 volts. Equiv. of 57.5 kWh Output is 3-phase 400 volt through 3 x 230 V, 10 kVA

PV Arrays

PV Arrays

Current Rooftop Setup

AUA Solar Rooftop Strategy

Support Structure

AUA SPVS general information Project Participants: SEUA Heliotechnics Lab team Viasphere Technopark Transistor Plus team AUA team with Dr. Melkumyan’s group

Components of the PV System Photovoltaic (PV) panels Battery Bank Charge controllers Invertors Load

PV Cells Manufactured by Krasnoye Znamye, Russia 125 x 125 mm rounded square Capacity of each cell – 2.2 Watt Price of each cell – $4.62 Price per peak Watt – $2.1 Number of cells – 2800 Efficiency – 15% (actually almost 16%)

PV Cells

PV Panels manufactured in Armenia PV panels are manufactured by Heliotechnics Laboratory of the SEUA Used is a Windbaron Laminator Glass bought in the USA – by a price of small lot EVA and Tedlar bough by a discount Frame manufactured in Armenia

PV Panels manufactured in Armenia

Battery Bank The voltage used is DC 48 Volts We use eight Rolls Solar Deep Cycle batteries, connected in series Each - 6 volt, of 1150 amper-hour capacity Total battery bank storage is 1150 amper hours at 48 volts. Equiv. of 57.5 kWh storage

Charge Controllers The PV array is devided into 3 sub-arrays: - Right - Center - Left Charge controllers use three steps of connection: 1, 2, or 3 subarrays Charge controllers are Xantrax, 40 amps, 120 amps total

Inverters – made in Armenia Designed and Manufactured by Transistor Plus of the Viasphere Technopark who has a long history of power supply/inverter design and manufacture Output is 3-phase 400 volt through 3 x 230 V, 10 kVA, - 3 sine-wave inverters

Inverter Performance

Load Currently the load is the DESODEC (Solar HVAC) equipment With two controllable powerful duct fans, drives, pumps, valves, controlls, sensors, etc. A circuitry automatically switches the load to the electric grid when the battery bank is exhausted

Performance and benefits of the system Efficiencies of the different components: - PV panels: > 12% - cables: 90% - batteries 60% - 90% - Inverters 90% Dependency on weather Dependency on load

PV System calculation approach See the handout “PV System calculation approach”

Homework List the main components of the solar PV system. Which components can be omitted in urban areas? Imagine your PV system costs $2400 per installed kW. Calculate the cost of 1 kWh in Yerevan if the system lifecycle is 50 years. Remember AUA solar monitoring data. In which cases a solar PV system is feasible or more economical in contrast to electric power supplied from the grid? Explain.