6/3/20 “no worries, no-one can see my roof” Solar PV Solar Geysers IrradiaVon Irradia5on PV technologies Cable calc. Volt drop Series and parallel config Moun5ng Structures PV Fuse Combiner Boxes Inverter calc Voltage Standards SPD’s, Calcula5ons LPS & Earthing DC vs AC Disconnect Pr Safety & Cos5ng BaHeries Energy Efficiency Off-Grid 48 24
6/3/20 InsolaVon vs irradiance • (Photovoltaic) • PV Power varies based on available insolaVon. • This variaVon could be effected by changes in the atmosphere, weather pagerns and seasonal changes. • InsolaVon is defined as the amount of radiaVon striking the earth • Note the difference in the terms – Irradiance : Intensity of Solar energy kW/m2 – InsolaVon : QuanVty of Solar energy kWh/m2 49 The solar constant 1367W/m 2 – World RadiaVon Centre ReflecVon, DeflecVon & AbsorpVon Reference: Duffie Beckman 1991 50 25
6/3/20 Sun hours calculaVon • Peak Sun Hours are used to calculate power generaVon of PV modules • Peak Sun Hours can be calculated by dividing annual sun hours by the number of days per year. • e.g. 2000kWhrs/m 2 divided by 365 = 5,47kWh/m 2 • 5,47kWh/m2/day or 5470Wh/m2/ day • 51 CalculaVon tools for design confirmaVon • PVSol • PV Syst • Helioscope 26
6/3/20 Link to GRS Solar Tool • hgps://re.jrc.ec.europa.eu/pvg_tools/en/tools.html#PVP • GHI - Global horizontal irradiaVon is used for PV applicaVons • DNI - Direct Normal irradiaVon figures are used for solar Thermal applicaVons • hgps://www.suncalc.org/ #/-30.8331,24.3049,2.5266666666666775/2019.07.30/14 :30/1/3 Global Horizontal Irradiance (GHI) is the total amount of shortwave radiation received from above by a surface horizontal to the ground. This value is of particular interest to photovoltaic installations and includes both Direct Normal Irradiance (DNI) and Diffuse Horizontal Irradiance (DIF). 53 Incline 54 27
6/3/20 Trackers • Single axis trackers • Implemented in SA • Shows approx. 30% improvement on yield • Maintenance Centurion Solar should be considered in feasibility criteria Sishen 75MW 55 Summer and winter solsVce 63 o 43 o 33 o 56 28
6/3/20 Impact of incline on yield 10 33 33 8 6 53 53 4 2 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 57 Impact of incline on yield - JHB 9 33 o CPT 7 33 o JHB 5 4 2 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 23 33 43 58 29
6/3/20 InsolaVon energy (Bfn 30 o ) hgp://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php?map=africa 8000 6000 Watts per day 4000 2000 0 Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Due North West & East South Due North 60’ Tilt 59 Summary - Impact of orientaVon • 1000W/m2 is used as the reference value and global average. • Solar IrradiaVon E varies according to region and season. W N 60 30
6/3/20 AC & DC • AC IS NOT COMPATIBLE WITH DC • The frequency of AC in SA is around 50Hz meaning there are 50 ‘waves’ or cycles per second • To Convert – AC to DC we use a RecVfier – DC to AC we use an Inverter • Inverters invert DC to AC. By definiVon Inverters cannot charge ba/eries 61 Harmonics • Both inverters and recVfiers are sources of Harmonics • Harmonics are caused by non-linear loads • Pre-1970 all loads were linear as they were mostly resisVve • The fundamental, is defined as the lowest frequency of a periodic waveform 31
6/3/20 AC & DC • Only some inverters can synchronise to a reference, i.e Grid Ved inverters that feed power back to the grid • MulVple sources of AC need to be synchronised, i.e. Voltage + Frequency + Phase angle With DC no synchronisaVon is required. 63 Power and Energy • DisVncVon between power and energy is important – When sizing systems • Energy requirement is used to size the bageries or storage devices • Power requirement is used to size the inverter • Understanding the difference gives the consumer confidence in the knowledge of the sales and installaVon teams 32
6/3/20 Power and energy • Solar Modules are rated in Power Capacity • Loads are rated in Power Capacity • Li-ion Bageries generally rated in Energy Capacity • Lead Acid bageries – Energy capacity must be calculated 65 Power and energy - ConsumpVon • Example: Let’s take 12 LED downlighters from the previous slide as the load • Each downlighter consumes 23W • 12 x 23W = 276W • Energy = Power x Time • Energy = 276W x Time • Energy = 276W x 8hrs = 2208Wh or 2,2kWh 33
6/3/20 Power and energy - GeneraVon • As per the data sheets - Page B2 – ‘60 cell module’ • Energy = Power x Vme = 260W x 5,5hrs = 1430Wh • Modules for a site is selected based on: – Roof size – Module orientaVon – Stock availability – Price – Ease of on-site operaVon Power and energy - Storage • Power can be calculated by multiplying Volts with Amps • W = Volts x Amps • Energy = Power x time or Wh = W x hrs • Energy = ( V olts x A mps) x hr • When the energy in a Lead Acid battery is calculated the Amp-hour rating of the battery is multiplied by the nominal Voltage • Lead Acid Battery: Energy = Ah x V • 100 Ah x 12 V = 1200Wh 34
6/3/20 ConsumpVon – Storage - GeneraVon • Energy = Power x time = 260W x 5,5hrs = 1430Wh • Energy = 276W x 8hrs = 2208Wh or 2,2kWh • Energy = Ah x V = 100Ah x 12V = 1200Wh Basic Terminology • What is Volt? – Voltage can be explained as being electrical pressure • What is Amp? – The movement of current is measured in Amps • Nominal voltage • What is Series? See next slide • What is Parallel? See next slide 35
6/3/20 Series configuraVon • Voltage increases and the current stays the same Series ConfiguraVon • When connecVng in series the voltage is mulVplied by the number of panels to get to the system voltage. • The inverter or charge controller needs to be able to operate in the system voltage temp ranges Modules in Series V oc Ave. Per cell Module V oc -15 ℃ 80 ℃ 36 Cell X 8 Modules 0,6 21,6 193 144 54 Cell X 8 Modules 0,6 32,4 290 216 60 Cell X 8 Modules 0,6 36 322 240 72 Cell X 8 Modules 0,6 43,2 387 288 Values are es5mated and have been calculated using a temp co-eff. of 0,30%/ ℃ 72 36
6/3/20 Parallel configuraVon • Current increases and the voltage stays the same Parallel ConfiguraVon • Using Branch connectors • Same power being produced as previous slide • Lower Voltage • Current X 2 of a single string Modules in Series V oc Ave. Per cell Module V oc -15 ℃ 80 ℃ 36 Cell X 4 Modules 0,6 21,6 96 72 54 Cell X 4 Modules 0,6 32,4 145 108 60 Cell X 4 Modules 0,6 36 161 120 72 Cell X 4 Modules 0,6 43,2 193 144 74 37
6/3/20 Parallel ConfiguraVon • Using a combiner box • Same power being produced as previous slide • Offers the advantage of • individual string disconnecVon • Housing for SPD’s To Inverter 75 Ohm’s Law • Ohm's Law is a formula or range of formulas used to calculate the relaVonship between voltage, current and resistance in an electrical circuit. 38
6/3/20 Power triangle • The power Triangle is a range of formulas clarifying the difference between Power, Current and Voltage System sizing when storage is included 39
6/3/20 How bageries charge • Batteries charge with current • The current changes the internal resistance of the battery • The result is an increase in voltage PV Technology Irradia5on PV technologies Cable calc. Volt drop Series and parallel config Moun5ng Structures PV Fuse Combiner Boxes Inverter calc Voltage Standards SPD’s, Calcula5ons LPS & Earthing DC vs AC Disconnect Pr Safety & Cos5ng BaHeries Energy Efficiency Off-Grid 80 40
6/3/20 PV History 1839 - Edmund Becquerel discovers the photovoltaic effect 1883 - Charles Fritz creates first solar cell (gold coated selenium) 1953 - Bell labs create Solar Cells that are 6% efficient 1958 - Solar energy is used in space 1982 - First 1MW plant is built in California 1994 - NREL creates 30% efficient Gallium Indium phosphate 2015 - 5% eff. Flexible Solar cells are printed using a printer 81 Costs of PV over Vme 1MW CosVng around R13/w Oct 2016 Freight 0,01 Profit Margin 0,02 Cell 0,20 BoM, EVA 0,12 $0,38(US) Manufacturing & Assembly 0,04 Total 0,39 2016 82 41
6/3/20 Basic Electrical Principles Irradia5on PV technologies Cable calc. Volt drop Series and parallel config Moun5ng Structures PV Fuse Combiner Boxes Inverter calc Voltage Standards SPD’s, Calcula5ons LPS & Earthing DC vs AC Disconnect BaHeries Off-Grid 83 Different PV technologies 84 42
6/3/20 NREL PV Performance over Vme 85 General PV Module Efficiency Cell Material Lab Actual Concentrated pv (Sharp May 2014) 47% - Mono-crystalline silicon (Panasonic Feb 2014) 24.7% 18% Poly-crystalline silicon 20.4% 17% CdTe (Cadmium-Tellurid as at July 2015) 21.5% 16% CIGS (Copper Indium Gallium di Selenide July 2014) 18.3% 13% Amorphous Silicon (a-Si August 2014) 12% 10% 43
6/3/20 Crystalline Silicon Cells Mono-crystalline Poly-crystalline 87 Solar Cells • Cells are approximately 0,2mm thick Do not stand on modules!! Grid fingers Busbars/ Ribbons 88 44
6/3/20 Series cell configuraVon • Ribbons or busbars are soldered onto the face of one cell. • And then joined onto the back of the next cell • One side of the cell has one polarity and the other side has the opposing polarity 16W Module - Cell configuraVon Grid fingers Busbars/ Ribbons 90 45
6/3/20 Solar Cells configuraVon • 36 Cells - TradiVonally called 12 Volt modules • 54 Cells • 60 Cells • 72 Cells - TradiVonally called 24 Volt Modules 91 Module ConstrucVon • Some modules consist of 5 layers • Globally most module manufacturers use 3.2mm tempered low-iron glass • Hydrofobic & Hydrophilic coaVng • AnV-reflecVve coaVngs • AnV-dust / water • Nano CoaVngs • Hail tesVng done with 25mm hailstones at approx. 80km/h 92 46
6/3/20 Thin-film - CIGS & CdTe • CIGS – Solar FronVer moved out of SA in 2016 • CdTe – First Solar Barloworld • Material and workmanship warranty for ten (10) years and a power output warranty of 90% of the nominal output power raVng (PMPP+/- 5%) during the first ten (10) years and 80% during twenty-five (25) years subject to the warranty terms and condiVons. 93 Cell, Module, String, Array • Cell, module, string, array 1 x Cell 1 x Module 1 x String 1 x Array Image is an example only Induced Voltages – Do not connect this way 94 47
6/3/20 PV Cell Electrical parameters Current changes along with cell • size • 100 x 100 cell = approximately 4.5Amp 150 x 150 cell = approximately • 8.7Amp • Voltage of cells remain more or less the same at • 0.5V oc(open circuit) to 0.7V oc(open circuit) • Under varying temperature condiVons 95 PV Cell Electrical parameters • Calculate the voltage of the string of cells above? If the cells were 100 x 100, what would the • Current be that can be produced? 96 48
6/3/20 Main PV technologies Thin-Film Silicon wafers Major Issues Major Issues (Mono & Poly) (CIGS) Micro Cracks (snail trails) DelaminaVon DelaminaVon Thermal images: courtesy Sinani Energy 97 Understanding the Data Sheet • Power output tolerances • Cells vary in performance. SorVng limits relate to possible variances in panel performance • I SC The short-circuit current is the maximum current through the solar – cell (i.e., when the solar cell is short circuited). Voc • – Open-circuit voltage is the difference of electrical potenVal between two terminals of a device when disconnected from any circuit. – There is no external load connected. No external electric current flows between the terminals. – 98 49
6/3/20 All values in specificaVons are at STC & NOCT • STC corresponds to: NOCT is the temperature • 1000W/m2 reached by open circuit cells in a module under the conditions as • At 25°C cell temperature, listed below: • with an Air Mass 1.5 • Open back mounted module (AM1.5), • At a 45° Vlt angle from the horizontal • as defined in IEC 60904-3 • Total irradiance of 800 W/m2 and • 20°C ambient temperature where a • 1 m/s wind speed is available • on a panel in an open circuit condiVon 99 Air Mass • One and a half Vmes the spectral absorbance of the Earth’s atmosphere. It refers to the amount of light that has to pass through Earth’s atmosphere before it can hit Earth’s surface, and has to do mostly with the angle of the sun relaVve to a reference point on the earth. evaluaVng spectrally selecVve PV materials with respect to • Modules used in space are performance measured under tested against AM=0 as the varying natural and arVficial atmosphere is not a factor in sources of light with various space. spectral distribuVons. 100 50
6/3/20 PV Panel DegradaVon 101 Electron Flow Benjamin Franklin • – Glass & Silk Experiment – Kite experiment • Electrons – Charged ‘negaVve’ – Move from areas of abundance to areas of depleVon • The same principles can be seen in solar modules 102 51
6/3/20 Current flow in a cell - video 103 By-Pass diodes in panels No Visible Diodes Polarity: PosiVve is always on the right and negaVve always on the leu in crystalline modules 104 52
6/3/20 How to overcome the effect of shading • Most good quality panels are factory figed with Diodes. • A diode can be explained as a one way valve for current. • These diodes are referred to as bypass diodes • Bypass diodes do not have an impact in reverse current Typical bypass diode wiring configuraVon Centre pin connected to posiVve Long pins connected to negaVve 105 Spacing of rows - rule of thumb • Rule of thumb for panel installaVon in CT, EL & PE= 1,9 X height • Rule of thumb for panel installaVon in DBN & BFN = 1,8 X height • Rule of thumb for panel installaVon in JHB = 1,6 X height 106 53
6/3/20 IV Curves explained • IV characterisVcs show the current and voltage generated across the terminals of a module. • With a variable resistor connected between the terminals, the operaVng point can be determined from the resulVng IV characterisVcs. • When R is small the module is a constant current source • When R = 0, Isc condiVons result. At Isc, voltage is 0 • When R is large (approaching infinity, modules behave as a voltage source creaVng the max Voc. At Voc current is 0 107 Effect of temp. on PV panels 108 54
6/3/20 Hot vs Cold days - String Voltage 700 650 Max 660V 600 550 500 450 Min 460V 400 350 300 15 Jun 2015: Coldest 250 winters day. 5 Jan 2016: Heat 200 wave in summer. 150 100 50 0 20 modules in a string - 4 strings / mppt - 3 mppt’s per inverter 109 Temp co-efficient calculaVons • ObjecVve: Calculate the module’s summer and winter voltages • Summer Voltage is the lowest possible voltage at the highest temperature • Winter Voltage is the highest possible voltage at the lowest temperature Module Voltages are High Module Voltages are Low Winter Summer Temperatures are low Temperatures are high 55
6/3/20 Temperature co-efficient calcs • -0,45%/ ℃ 260W 60 cell Maximum Voltage (VDC-max) • Eff of temp = 30,9V mp x 0,45%/ ℃ = Vmp Max_STC (Solar PV) x 1.15 • = 0,139V =Vmp Min_STC*0.75 Add co-efficient 36V mp 30,9V mp Deduct co-efficient 23V mp -15 ℃ 0 ℃ 5 ℃ 25 ℃ 46 ℃ ±2 60+ ℃ 70 ℃ 80 ℃ Molteno NC PE & CT EL STC NOCT CT GP NC Actual Cell Temperature - Values based on resident survey 111 Sunny vs rainy days 62,500 8th January 2016 5th January 2016 4th May 2015 Clear Summer : Produced 386kWh Cloudy Summer : 50,000 for the day. Produced 316kWh for the day. 37,500 25,000 Clear Winter : Produced 248kWh 12,500 for the day. 0 112 56
6/3/20 Effect of Light intensity on current and voltage 113 Min & Max Current - Edge of cloud effect A maximum value of 1195W/m 2 was observed on 31/7/2015(PE) 114 57
6/3/20 Standards Irradia5on PV technologies Cable calc. Volt drop Series and parallel config Moun5ng Structures PV Fuse Combiner Boxes Inverter calc Voltage Standards SPD’s, Calcula5ons LPS & Earthing DC vs AC Disconnect Pr Safety & Cos5ng BaHeries Energy Efficiency Off-Grid 115 Consumer point of supply 116 58
6/3/20 Dedicated Feeder NRS 097 < 75% < 75% 117 Shared Feeder NRS 097 • Maximum PV System sizes • LSM > 7 < 75% • < 50 % conversion to PV • Shared liability <25% < 25% 118 59
6/3/20 Typical demand curve for residenVal installaVon Evening Peak Demand Morning Peak Demand PV Power generaVon vs convenience 119 Inverter / system size selecVon Typical demand curve for office block installaVon Mid day Peak Demand PV Power generaVon 120 60
6/3/20 Solar PV Service Technician(Separate Trade) 1. Occupational Tasks 2. Planning and preparing for maintaining, testing, diagnosing, repairing and replacing PV system electrical and mechanical components (Level 4) 3. Inspecting, testing, diagnosing, replacing and maintaining PV panels (Level 5) 4. Inspecting, testing, diagnosing, replacing, repairing and maintaining inverters in PV systems (Level 5) 5. Inspecting, testing, diagnosing, replacing and maintaining batteries and charge controllers and repairing charge controllers in PV systems (NQF Level 5) 6. Inspecting, testing, diagnosing, replacing, repairing and maintaining transformers in PV systems (Level 5) 7. Inspecting, testing, diagnosing, replacing and maintaining cables, cable inter-connections, smart boxes, PV junction/string boxes, string diodes, connectors and fuses in PV systems (Level 5) 8. Inspecting, testing, diagnosing, replacing, repairing and maintaining switchgear and control gear in PV systems (Level 5) 121 How do i qualify as an electrician • Influx of diverse range of occupaVons in energy sector – Many not skilled in electrical trade – RPL vs standard apprenVceship route – 4 years experience with >N2 Electrical – 6 years experience with no academic electrical background – Merseta, Ceta, EWseta – Same cerVficate & Red Seal – Register with D.o.L – = single phase tester – Electrical trade = N4 – Unlocks more opportuniVes, i.e. N4 electrical academic online 122 61
6/3/20 Legal, Standards & Regulatory Framework • Commissioning report – Installer tested system and it was working – Line diagram • Should accompany design but could become as-built – Standard operaVng procedure • Manuals and documents – Maintenance Procedure • Improve overall performance (up-sale SLA) – Lock out or disconnecVon procedure • What happens when the system – Stops working – Needs to be maintained – Electrical C.o.C 123 Compulsory Standards related to solar ▪ LOA’s are required by all manufacturers and importers of commodities that fall under the scope of the compulsory specifications prior, to the sale of the product. • NaVonal Regulator for Compulsory Standards – Leger Of Authority • SANS IEC 61010 - Safety requirements for electrical equipment for measurement,control and laboratory use • SANS IEC 61558 - Safety requirements for power transformers, power supplies,reactors and similar products • VC8075 - Compulsory SpecificaVon for the Safety of Electric Cables with Extruded Solid Dielectric InsulaVon for Fixed InstallaVons (300/500V to 1900/3300V) • VC8077 - Compulsory SpecificaVon for the Safety of Medium-Voltage Electrical Cables. 124 62
6/3/20 Solar standards developed by UVliVes ECB & ECA Eskom AMEU 277 177 NRS SANS 125 Labelling - NRS 097-2-1:2017 • 4.2.7 Labelling • 4.2.7.1 A label on the distribuVon board of the premises where the embedded generator is • connected, shall state: “ON-SITE EMBEDDED GENERATION (EG) CONNECTED. THE EG IS • FITTED WITH AN AUTOMATIC DISCONNECTION SWITCH WHICH DISCONNECTS THE EG IN • THE CASE OF UTILITY NETWORK DE-ENERGIZATION.” • 4.2.7.2 The label shall be permanent, coloured red, and with white legering of height at least 8 mm. 126 63
6/3/20 Harmonics - NRS 097-2-1:2010 • 4.1.6.4 Total harmonic current distorVon shall be less than 5 % at rated generator output in accordance with IEC 61727. Each individual harmonic shall be limited to the percentages listed in table 1. Current distorVon limit as a funcVon of harmonics (Source: IEC 61727:2004) 1 2 Odd harmonics DistorVon limit 3rd through 9th Less than 4,0 % 11th through 15th Less than 2,0 % 17th through 21st Less than 1,5 % 23rd through 33rd Less than 0,6 % Even harmonics DistorVon limit 2nd through 8th Less than 1,0 % 10th through 32nd Less than 0,5 % 127 UVlity compaVbility – NRS 097-2-1:2017 • 4.1.1.6 The maximum size of the embedded generator is limited to the raVng of the supply point on the premises. • 4.1.1.7 Embedded generators larger than 13,8 kVA shall be balanced three-phase type. • A customer with a mulVphase connecVon shall split the embedded generator over all phases if the EG is larger than 6 kW. 128 64
6/3/20 SynchronisaVon - NRS 097-2-1:2010 • 4.1.8.2 AutomaVc synchronizaVon equipment shall be the only method of synchronizaVon. • 4.1.8.3 The limits for the synchronizing parameters for each phase are • a) frequency difference: 0,3 Hz, • b) voltage difference: 5 % = 11,5 V per phase, and • c) phase angle difference: 20°. 129 NRS Standards applied • hgp://resource.capetown.gov.za/documentcentre/Documents/Forms,%20noVces, %20tariffs%20and%20lists/Approved%20Photovoltaic%20(PV)%20Inverter %20List.pdf • Product: KLNE • Model: Solartec D15000 • Test House: TUV Rheinland • Requirement: RCD Type B required on the supply side 130 65
6/3/20 Solar standards developed by Industry ECB & ECA Technical SABS Eskom Commigee Industry associaVons ECB & ECA Working Eskom Group Industry associaVons Specialist Reps. 131 Standards issued or being developed • SANS 60364-7-712 (Fuse and cable sizing) • SANS 61215 PV Module standard • SANS 62040 UPS systems • IEC 62930 Electric cables for photovoltaic systems (Feb 2018) • Local standard development – Same colour cable on DC – TesVng procedure on PV – AddiVonal DB – Surge protecVon before and auer – Level of electrician to sign-off bagery installaVons • Hazardous locaVons 132 66
6/3/20 Bageries Irradia5on PV technologies Cable calc. Volt drop Series and parallel config Moun5ng Structures PV Fuse Combiner Boxes Inverter calc Voltage Standards SPD’s, Calcula5ons LPS & Earthing DC vs AC Disconnect Pr Safety & Cos5ng BaHeries Energy Efficiency Off-Grid 133 C-RaVng of bageries • Both Lead-acid and Li-ion Bageries have C raVngs • “C” indicates 3 important criteria. – Energy Capacity – Charge rate – Discharge rate 67
6/3/20 Bagery Capacity • Capacity of the bagery provides the storage capacity of a bagery, e.g. 100Ah • Bageries are usually marked as C 10 , C 5 , C 2 , C 1 or C 0.5 . The subscripts 10, 5, 2, 1 or 0.5 gives the charge/discharge rate • If we have a bagery denoted by C 10 , having a capacity of 40 Ahr, then (40/10) = 4 Amps of current can be drawn from such a bagery for 10 hours. 135 Cost of energy equaVon - Life cycle cost Bagery Price __________________________________ Cost of Energy = (Energy (Ah*V) x DoD x #Cycles x Round trip efficiency) R1200 __________________________________ Cost of Energy (SMF) = (1,2kWh x 50% x 120 x 90%) Cost of Energy (SMF) = R18,52/kWh • Energy = Power x Time • Power = Volt x Current 136 68
6/3/20 D.o.D & RTE • D.O.D • R.T.E – Depth Of Discharge – Round Trip Efficiency Four main storage technologies • Flow bageries • Li-ion bageries • Lead acid bageries • Super capacitors 138 69
6/3/20 Redox Vanadium Flow Performance not affected by temperature Can be drained 100% over full service life Life unlimited or 10 years Charge Voltage 54VDC System weight 1800kg - 3000kg 5 year standard warranty WxDxH 2.20 x 1.22 x 2.15 m 2,7m 2 139 hgp://www.cesa.org/webinars/showevent/flow-bagery-basics-part-1-what-they-are-how-they-work-where-they-re-used?d=2014-06-19 Li-ion Chemistries 70
6/3/20 Li-ion bagery layouts Li-Fe Bagery technology • Lithium Iron Phosphate • No significant heaVng during charging and discharging process. • Larger bagery architecture. • Lithium Iron NMC (Nickel Manganese Cobalt) Tesla • Significant heaVng – Tesla - Water cooled system • approx. 880 small bageries to create 48V packs stepped up to 400V(DC-DC Converter) • 6,4kWh per day at a max of 3,3kW peak.(18MWh) • Full closed loop recycling by 2020 142 71
6/3/20 Lead Acid Family • Lead acid bageries are not an exact science – The energy storage and draw-off is as a result of a chemical reacVon subjected to external factors Lead Acid VLA (Vented Lead-Acid) VRLA (Valve Regulated) Flooded (Non Spillable) Absorbed Glass Standard Maintenance Free Gel Mat (AGM) Lead Antimony Lead Calcium Lead Calcium Lead Calcium Higher level of gassing Calcium = Lower level of gassing & self discharge Requires higher charge **Tip -Compare voltage weight 143 Lead Acid ConstrucVon • Bageries have posiVve and negaVve plates separated from one another to prevent short Deep cycle posiVve plate circuit condiVons. – Standard lead acid (car bagery) • 2,2mm posiVve & • 1,4mm negaVve plate • Deep Cycle (brand dependent) • 3,3mm posiVve & Car bagery posiVve plate • 2,3mm negaVve plate 144 72
6/3/20 Lead Acid ConstrucVon • 12 Volt bagery = 6 x 2V cells • 2 Volt bageries • (photo: 1000Ah x 2V cells) – Which always produce approx. 2,1 - 2,3 Volts/Cell • Series & Parallel regardless of size of cell. 1 2 3 4 5 6 145 Bageries • Bageries with a high power density and low energy density – Good for delivering large volumes of power over a Car short period of Vme • Good for vehicles • Semi-TracVon Bageries (a happy medium) – Good for delivering smaller volumes of energy over Leisure a longer period of Vme in light duty applicaVons • Also referred to as “Leisure” Bageries • Bageries with a low power density and high energy density – Good for delivering smaller volumes of energy over a Deep Cycle longer period of Vme • Good for solar 146 73
6/3/20 Bageries – D.o.D, End of life • Cycle life – Number of cycles it was designed to deliver • End of life – A fully charged bagery that can only deliver 60-80% of its rated capacity may be considered to be at the end of its cycle life • Design life – See next slide 147 Design life under float condiVons • Bageries remaining in a floaVng state may or may not last longer than bageries that are cycled • When not in service all bageries self-discharge at a rate of about 1-15% per month depending on the type of bagery. 148 74
6/3/20 Live fast die young • Higher temperatures = Lead acid bagery being more efficient • Hoger bageries die faster • The rate of self- discharge increases as the temperature increases. 149 Depth of Discharge vs Cycles 12000 M-Solar Cell FNB Omnipower 10000 Trojan J185 Hoppecke OPzV Energizer Victron Li-ion 8000 6000 4000 2000 0 10 20 30 40 50 60 70 80 90 100 • If only cycled to 10% DOD, a bagery will last about 5 Vmes as long as one cycled to 50%. 150 75
6/3/20 Bageries - Storage • Myth: Storing bageries on concrete floors will cause them to discharge. – About 100 years ago, bagery cases were made up of wood and asphalt. The acid would leak from them, and form a slow- discharging circuit through the now acid- soaked and conducVve floor. – Wood is not used in modern bagery cases • Bageries should not be placed directly onto concrete during operaVon in order to prevent large temperature differences between the upper and lower regions. 151 Li-Fe Brands for Solar sector • Local landscape (Brands Available) • SolarMD (MyPower24) • Blue Nova • Freedomwon • i-G3N • REVOV • LG Chem • Li-ion bageries need to be managed by a BMS in order to prevent thermal • BagCo. runaway and damage to the bagery • Icon • Tesla • BMZ • Zegajoule • Extra2000 (SolaX) • Python (Pylontech) 152 76
6/3/20 Lead Acid Charging cycle - 3 stages Voltage Current AbsorbVon Voltage Float Bulk Time Bulk charge (aka constant current charge) Current stays constant and voltage increases Absorbtion Charge (aka Topping charge) Voltage remains constant and current drops consistently until battery is fully charged Float stage Charge voltage is reduced to between 13 & 13,8V and held constant while the current is reduced to less than 1% of battery capacity. 153 Charging and discharge • Discharge takes place through the posiVve terminal • Charging takes place through the negaVve terminal VS. 154 77
6/3/20 Bagery charging • Recommended Charging current – 10% of bagery capacity in Grid assisted areas – 20% of bagery capacity in certain off-grid areas – 30% of bagery capacity in all other off-grid areas • (Sonnenschein) The charge current must not exceed 35A / 100 Ah nominal capacity. (35%) • Higher currents will not lead to relevant gain of recharging 9me. Lower currents will prolong the recharging Vme significantly. • The cell / bloc temperature must never exceed 45°C. If it does, stop charging or switch down to float charge to allow the temperature to decrease 155 Why are these configuraVons incorrect? Charging into the first row only Charging cable lengths EqualizaVon 156 78
6/3/20 Correct InstallaVon Why 12 / 24 / 48V Charging & Show series & parallel discharging across bank Equal cable lengths EqualizaVon taken care of with busbars 157 Busbar & Disconnector Layout 158 79
6/3/20 Bus bar calculaVon - Rule of thumb Please double check busbar thickness for safety & applicaVon • Bus bar calculaVon as a rule of thumb • width x height x 2 should = bagery capacity • 5mm x 20mm x 2 should be sufficient for a 200Ah bagery bank. • (SANS10142-1 6.6.2) for current >1600A = 1,6A per mm 2 • current <1600A = 2Amps per mm 2 159 Bagery charging • Very important for background sevngs. • Adjust the cable resistance in order to ensure the correct charging voltage. • (grid Ved hybrid inverters) Some can be controlled not to feed back into the grid (Grid-LimiVng) • AddiVonal equipment • Meter • Modbus • costs about R4k 80
6/3/20 Bagery - Summary • Minimize voltage drop • Use the correct size cables • Locate bagery and load close to PV panel • Choose a large enough bagery to store all available PV current • VenVlate or keep bagery cool, respecVvely, to minimize storage losses and to minimize loss of life • The 744 rule: Is a genset/grid available for boost charge ? 161 Off-grid Irradia5on PV technologies Cable calc. Volt drop Series and parallel config Charge Moun5ng Structures controller Inverter Voltage Calcula5ons DC Disconnect Pr BaHeries 162 81
6/3/20 System sizing when storage is included Step 1 - Calculate consumpVon Step 1.a) Power Requirement in W Step 1.b) Daily ConsumpVon in Wh 164 82
6/3/20 Step 2 - Bagery Sizing • Lead Acid System Losses vary between ±22 to 30% 5 • Li-ion System Losses vary between ±18 to 22% 5 15 hgp://www.bagerysizingcalculator.com • 2 Inverter Charge controller Cabling System (Batteries + connections) Inverters 165 Bagery Sizing – Lead Acid Step 2.a) Multiply Daily requirement with losses (as a factor) = 7994Wh x 1,27 = 10152Wh Daily Storage required This value represents 27% Losses Step 2.b) Divide Daily storage by DC voltage = 10152Wh / 48V = 211Ah of Average Daily Ah needed The “48V” value is found in the datasheet Step 1.a showed us we need 3576W of Power. At least a 5000W inverter would be required. From the datasheet Page B1, we will see the 5000W inverter uses a 48V bagery / bagery bank. Step 2.c) Adjust to depth of discharge = 211Ah / 0,5 = 422Ah Sub Total of storage required Use 0,5 for 50% D.o.D, 0,4 for 40% D.o.D and so on . . . . . 166 83
6/3/20 Bagery Sizing – Lead Acid Step 2.d) Make provision for rainy days =422Ah x 2 days = 844Ah Total Storage required This value is just a guess and would vary based on the number of rainy days for that area The battery bank needs to be 48V 844Ah according to our calculations. Step 2.e) Select battery to match both both 48V and 844Ah as close as possible. 12 Volt Bagery 200Ah 2 Volt Cell 840Ah 4 in series to reach 48V 200Ah 24 in series to reach 48V 840Ah 167 Bagery Sizing – Lead Acid Step 2.f) Check to ensure that the chosen battery can handle the rate of discharge (c-rating) Step 3.a) Calculate Power required to charge batteries. (Group Exercise) Power = Volts x Amps Step 3.b) Select modules to match Power Requirement, roof space and ease of handling (Group Exercise) Step 3.c) Module layout and design is done according to charge controller power, voltage and current limitations. (Group Exercise) 168 84
6/3/20 Step 4 - Select Charge Controller • Microcare vs Victron recommended chart • Please check other manufacturer specificaVons 169 Bagery Fuse calc’s Irradia5on PV technologies Cable calc. Volt drop Series and parallel config Moun5ng Structures PV Fuse Combiner Boxes Inverter calc Voltage Standards SPD’s, Calcula5ons LPS & Earthing DC vs AC Disconnect Pr Safety & Cos5ng BaHeries Energy Efficiency Off-Grid 170 85
6/3/20 Bagery SCC • The short circuit current of a bagery (considered to be a finite power source) depends on: – the resistance of the path, and – the state of charge and – internal resistance of the bagery which depends on variables, such as: • the material and dimensions of the grids and terminal posts, • the surface area and composiVon of acVve material, • the specific gravity, and • the thickness of the separators • REf : StaVonary Bagery and DC Power System Electrical ProtecVon Design ConsideraVons; K. Uhlir 171 Bagery PSSC SANS 10142-1:2012 • The prospecVve short-circuit current of bageries can be calculated using the following values in a formula: (I=V/R) • EB is the open-circuit voltage of the bageries; if this informaVon is not known, then use • EB = 1,05 x UNB V (where UNB = 2,0 V/cell); • RBBr is the total resistance of the upstream network, in ohms, including the internal resistance of the bagery and the resistance of the conductors; • RBBr = 0,9 x RB + RBL + Ry Ω (see figure 8.1); • RB is the internal resistance of the bagery; • RBL is the resistance of the bagery connecVons; • Ry is the resistance of the conductors. • NOTE The internal resistance of the bagery can be obtained from the manufacturer’s data. 172 86
6/3/20 Bagery PSCC • A conservaVve approach in determining the short-circuit current that the bagery will deliver at 25°C is to assume that the maximum available short-circuit current is 10 Vmes the 1 minute ampere raVng (to 1.75 V per cell at 25°C and specific gravity of 1.215) of the bagery • Ref:hHps:www0.bnl.gov/isd/documents/88634.pdf • Page 10 Sec5on BaHeries 10 X 38 PV fuse 173 Bagery Fuses • Varied Philosophies on fuse sizing – Could be based on: • RecommendaVon by Manufacturer, or; • Calculated based on current consumpVon, and on potenVal short circuit current, or; • Various rules of thumb. 174 87
6/3/20 Basic bagery discharge principles I = __ P V 230W @ 48V 230W @ 230V = 4,79A = 1A Inverter TV + Losses 48 Volt Battery Bank 175 Cable sizing for bageries - 0.259V drop max. 176 88
6/3/20 Conductors Irradia5on PV technologies Cable calc. Volt drop Series and parallel config Moun5ng Structures PV Fuse Combiner Boxes Inverter calc Voltage Standards SPD’s, Calcula5ons LPS & Earthing DC vs AC Disconnect Pr Safety & Cos5ng BaHeries Energy Efficiency Off-Grid 177 Conductor resistance • InternaVonal Annealed Copper Standard (IACS) Metal / Material Conductance IACS Silver 105% Copper 100% Gold 70% Aluminium 61% Brass 28% Zinc 27% Nickel 22% Iron 17% Iron 17% Tin 15% Phosphor Bronze 15% Lead 7% Nickel Aluminium Bronze 7% Steel 3 to 15% 178 89
6/3/20 Solid or stranded? • Solid wire is cheaper, but does not put up with the constant flexing of power cords. • Solid core wire in our walls where it does not need to move and cost magers • Stranded wire in our power cords where a solid wire would quickly harden and break from conVnuous flexing. • Why would wire work harden, embrigle and break? • Strand diameter relaVve to the bend radius is what determines how much strain is imparted into the wire. Solid wires have large strand diameters and see lots of strain. Stranded wires have strands with small diameters. • Welding & bagery cables use thin strands to compensate for movement 179 Solar cable & conductors • General Cable • Halogen-free wiring will typically have a higher conVnuous use temperature raVng, and is more suitable for pv operaVng environments.(Popular sizes 4 & 6mm) • Rated from 900 – 1500V Crosslinked Special Polyolefin • Flexible Vnned mulV stranded wire • XLPO • 36 Shore D • Halogen free • Weather- and UV-resistant • Ozone resistant 180 90
6/3/20 Avoid loops - Induced voltages 181 TerminaVng Solar cable • MC4 type connectors are rated • 22A-30A 4mm 2 -6mm 2 (please check parVcular brand) • For safety reasons do not cross mate coupler brands • Use only PV cerVfied cables (Vnned mulV-stranded, double insulated) • Avoid colour cables (long term UV resistance) 182 91
6/3/20 ConnecVng solar Cable 183 Volt drop CalculaVon • AssumpVons & Figures correspond to SANS 10142-1 Page 305 & table 6.2 Convert from mV to Volts. Max distance = 20m @ 110V • 4mm cable volt drop = 11mV/a/m • 6mm cable volt drop = 7.3mV/a/m 184 92
6/3/20 Combiner boxes Irradia5on PV technologies Cable calc. Volt drop Series and parallel config Moun5ng Structures PV Fuse Combiner Boxes Inverter calc Voltage Standards SPD’s, Calcula5ons LPS & Earthing DC vs AC Disconnect Pr Safety & Cos5ng BaHeries Energy Efficiency Off-Grid 185 93
6/3/20 AC & DC Combiner boxes • Black cable only in a DC network. Is it allowed? 187 Combiner boxes – Examples 188 94
6/3/20 Combiner boxes – DC Combiner • Combine mulVple strings in parallel • Design is based on – Inverter requirements – Site/safety requirements – Designer/ client preference 189 AC Combiner boxes • Combine mulVple inverters onto the same AC connecVon point • Design is site / client / safety and applicaVon specific • Moulded case breakers recommended for commercial installaVons 95
6/3/20 Tips & Trends • Tip **BT Consult conducted a study to determine the temperature inside housings for electrical equipment. Findings were that internal housing temperature was between 8-10 o C higher than outside ambient temperature. This value has reference to the fuse deraVng temperature as per the next slide. • Tip **Use molded case breakers in larger systems • Trend *Use fuse box opposed to a combiner box on installaVons where the inverter comes figed with a combiner box 191 Fuse deraVng ▪ Fuse calculations: ▪ I sc x 1,56 ▪ Edge of cloud ▪ Fuse Derating ▪ 1 string not required ▪ 2 string not required ▪ 3 string maybe ▪ 4 string yes ▪ (n-1)Isc * 1,25 192 96
6/3/20 CalculaVng String fuses • Capability of the fuse should be • Where • Voc = Open Circuit Voltage • Ns = Number of modules in a string • Fuse Voltage Capability • = 1,2 x V oc x N s • Current Capability • = 1,56 x Isc 193 Earthing, LPS & SPD’s Irradia5on PV technologies Cable calc. Volt drop Series and parallel config Moun5ng Structures PV Fuse Combiner Boxes Inverter calc Voltage Standards SPD’s, Calcula5ons LPS & Earthing DC vs AC Disconnect Pr Safety & Cos5ng BaHeries Energy Efficiency Off-Grid 194 97
6/3/20 Earthing / Grounding • The simple definiVon of an earth is: • to connect the electric circuit or equipment to the earth’s conducVve surface. • Systems are earthed because of: • personal safety and protecVon in the event of accidental contact • equipment safety and protecVon in the case of a lighVng strike, surge and or fault condiVons. 195 Surge protecVon without LPS (62305) Class 2 Class 2 196 98
6/3/20 Surge ProtecVon with LPS Class 2 Class 2 197 Surge ProtecVon with LPS Class 1&2 Class 1&2 198 99
6/3/20 AC vs DC Switching Irradia5on PV technologies Cable calc. Volt drop Series and parallel config Moun5ng Structures PV Fuse Combiner Boxes Inverter calc Voltage Standards SPD’s, Calcula5ons LPS & Earthing DC vs AC Disconnect Pr Safety & Cos5ng BaHeries Energy Efficiency Off-Grid 199 Breaking the current • Fuse Wire / Fuses – Melt or disintegrate • Circuit breakers – Can be reset – Do not use a CB with an AC raVng on a DC Circuit 200 100
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