Solar Energy System Design

Deepthi Narayana Swamy

Manjunathaswamy Antharavally

Ajinkya Bobade

Mohammed Alaswad

2016-10-17

Outline

– Introduction to Solar Inverters– Types of Solar Inverters– Working Principle – Inverter Sizing– Types of Inverter Manufacturers– Inverter connections

1

Inverters

➢ A power inverter, or inverter, is an electronic device or circuitry that changes direct current (DC)to alternating current (AC).

➢ The inverter does not produce any power; the power is provided by the DC source.

➢ A solar inverter is a component of a photovoltaic system and can be used for both, grid-connected and off-grid systems.

➢ Solar inverters: Photovoltaic off-grid Inverters are used for electrically powering remote houses. In case of grid-connected photovoltaic systems, surplus electricity is fed back into the grid.

2

String Inverters

Solar panels are arranged into groups connected by “strings.” Each string of panels is connected to a single inverter, which transforms the DC electricity produced by the panels into appliance of AC electricity.

➢ String inverters are the most cost-effective inverters.

➢ String inverters are favorable if roofs are not shaded at any point during the day and not facing different directions.

3

Micro-inverters

➢ Micro-inverters are installed on each individual panel in a solar energy system. They convert the DC electricity from your solar panels into AC electricity.

➢ Micro-inverters tend to be more expensive.

➢ Major advantage of micro-inverters is that they cancel out the negative impacts of partial or complete shading, i.e., there is no effect when one panel’s production decreases.

4

Power Optimizers

➢ A power optimizer is a DC to DC converter technology developed to maximize the energy harvest from solar photovoltaic systems.

➢ Power optimizers are located at each panel, usually integrated into the panels themselves.

➢ Power optimizers reduce the impact of panel shading on system performance, and also offer panel performance monitoring.

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String inverters Micro-inverters & power

optimizersCost Lowest Highest

Efficiency Lower High

Warranty 5-10 years 25 years(panel-integrated)

Performance when some panels are shaded Poor Good

Performance on complexi roofs Poor Good

Amount of electronics on roof Least Medium - Most

Performance with complex solar panel

arraysLow High

String Inverters vs. Micro-inverters vs. Power optimizers

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Inverter Working Principle

8

Inverter Sizing

➢ Inverter size depends on the size of the solar system.

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Inverter Sizing, Continued

➢ System size can be defined by the given equation,

𝑆𝑦𝑠𝑡𝑒𝑚 𝑆𝑖𝑧𝑒 ( )=(( ) η)/((𝑊𝑎𝑡𝑡𝑠 𝑊𝑎𝑡𝑡 ℎ𝑜𝑢𝑟𝑠 ∗ Peak )) 𝑆𝑢𝑛 ℎ𝑜𝑢𝑟𝑠Where η is the DC to AC system efficiency

Effects of under-sizing the inverter

➢ Under-sizing the inverter will mean that the maximum performance of the system will be dictated by the size of the inverter and regardless of how big the output of your solar panels is, the output will be cut-off by the inverter.

➢ Under-sizing the inverter can also lead to overheating and shorter life-span of the components in the system.

10

Inverter Sizing, Continued

Effects of over-sizing the inverter.

➢ Inverter companies predicted that a natural choice would be to oversize the inverters.

➢ As seen in the graph earlier, the optimal operation range is between 85-95% efficiency.

➢ Furthermore, if you do decide to add more panels to your existing installation the most you’ll loose is 10-15% of total system efficiency.

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Types of Inverter Manufacturers

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Types of Inverters Manufactured by SMA

Type: Optimizer Inverter

Used for: This company manufacturers inverters for voltage range of 1,000 VDC and 1,500 VDC system voltages

The image shows the type of inverter manufactured. Excess power can be given to the grid

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Type: String (Price: $1,500 to $1,600)Used for: Residential complex, power output 208VAC to 240VAC

Apart from construction of inverters SMA also do consulting, engineering and project support

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Types of Inverters Manufactured by ABBMicro inverters (0.25 kW to 0.3kW) (Price: $1,210)

String inverters (2 kW to 50kW)(Price: $2,250)

Central inverters (100 kW to 2000kW)

Turnkey stations (440 kW to 3.1 MW)

15

Enphase Energy

Manufactures micro-inverters (Price: $ 142)

Advantages of micro-inverters: Micro-inverters operate independently, so each panel performs to its fullest. One shaded or dirty panel won't affect the rest of the system. Burst technology lets micro-inverters produce more at dawn, dusk, and in low-light conditions, for a longer solar day.

Peak output power at 208 VAC: 225W

at 240 VAC: 225W

16

Solar-Edge Technologies

Manufacturer of single and three phase inverter Single-phase inverter3kW, 3.8kW, 5kW, 6kW, 7.6kW, 10kW and 11.4kW.

Three-phase inverter - 208V9kW, 14.4kWRated AC Power Output: 9000VA

Three-phase inverter - 480V10kW, 20kW, 33.3kW

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Solar System Connection

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19

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Total PV 250 panels, total power expected to be generated is 66.3 KW, one inverter (15000TL-US, see slide No. 19) shall be added to each string. PV should be distributed as :

Site -1 : 13 arrays in parallel, each with 4 panels in series, 124 VDC, 111 A. Site -2 : 13 arrays in parallel, each with 4 panels in series, 124 VDC, 111 A.

Site -3 : 13 arrays in parallel, each with 4 panels in series, 124 VDC, 111 A.

Site -4 : 12 arrays in parallel, each with 4 panels in series, 124 VDC, 103 A.

Site -5 : 12 arrays in parallel, each with 4 panels in series, 124 VDC, 103 A.

Project Connection

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References

➢ https://www.energysage.com/solar/101/string-inverters-microinverters-power-optimizers

➢ http://www.energymatters.com.au/components/micro-string-central-inverters/

➢ http://www.mpptsolar.com/en/how-does-an-inverter-work.html

➢ http://www.solar-facts.com/inverters/how-inverters-work.php

➢ https://en.wikipedia.org/wiki/Solar_inverter

➢ http://www.solarchoice.net.au/blog/optimizing-solar-panel-system-efficiency-through-inverter-

sizing/

➢ http://www.affordable-solar.com/solar-tools/inverter-sizing-guide/

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References, Continued

➢ http://www.homepower.com/articles/solar-electricity/project-profiles/microinverters-make-

simple-diy-installation

➢ http://www.greentechmedia.com/articles/read/these-are-the-top-ten-inverter-vendors-in-the-

united-states

➢ http://www.sma-america.com

➢ http://new.abb.com

➢ https://enphase.com/en-us

➢ https://usa.krannich-solar.com/fileadmin/content/data_sheets/inverter/usa/STPTL-US12-24EXP-

DUS132533W.pdf

➢ https:// www.Kyocera-KD265GX-LFB2-solar-panel-datasheet.pdf

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Thank you Questions