Solar Power Systems

Energy from the Sun

Solar Energy

Practical Uses of Solar Energy

Solar Water Heaters

Photovoltaic Development

Edmund Becquerel 1839

William Grylls Adams 1876

Gerald Pearson, Daryl Chapin, and Calvin Fuller 1953

Russell Ohl 1940

Space Race Saves PV

Vanguard I Satellite 1958 One Watt

Telstar Satellite 1962 14 Watts

From Novelty to Real World Applications

Buoys and Lighthouses

Offshore Oil PlatformsRR Crossings Rex, GA 1974

P-N Junction

Photovoltaic cell

Electrical Properties of a Solar Cell

Isc

– V +

I

)1( BVeA

External circuit (e.g., battery,

lights)

)1( BVeA

0

5

0.0 0.6Diode Volts

Dio

de A

mps

Diode current

)1( BVeA

)1( BVsc eAII

V

I

Isc

Voc

Im

Vm

, where A, B, and especially Isc vary with solar insolation

0

0

Increasing solar insolation

mm IVP max

Maximum power point

)1( BVsc eAII

I – V Curves

Terms• Solar Irradiance (density), average 1 kW per square

meter at noon on a clear day at sea level• Solar Insolation: hours per day that solar panel delivers

rated voltage, varies seasonally• STC: standard test conditions, 25° C, 1 kW per square

meter irradiance & AM 1.5• AM: Air Mass, density & clarity of air sunlight passes

through to reach the modules

PV Panel Ratings

Nameplate (STC) Rating

Field Rating

The PV Cell & Panel Families

Monocrystalline Panel

Thin Film Panel

Polycrystalline Panel

PV Cells and Panel Assembly

Monocrystalline PanelMonocrystalline Panel

Polycrystalline PanelPolycrystalline Panel

Thin Film Panel

PV Basics PV Basics

PV CELL OVERVIEW

SINGLE CRYSTALLINEPOLYCRYSTALLINE

CELLSTRING RIBBON

AMORPHOUS OR THIN FILM

Typically dark blue in color

Typically dark blue in color

Typically dark blue in color

Typically black in color

Efficiency averages 10% to 12%

Efficiency averages 9% to 11%

Efficiency averages 10% to 11%

Efficiency averages 6% to 9%

Degradation averaging 0.25% to 0.5% per year

Degradation averaging 0.25% to 0.5% per year

Degradation averaging 0.25% to 0.5% per year

Degradation averaging 0.25% to 0.5% per year

Vendors typically guarantee power 90% for 10 years , 80% for

25 years

Vendors typically guarantee power 90% for 10 years, 80% for

25 years

Vendors typically guarantee power 90% for 10 years , 80% for

25 years

Vendors typically guarantee power 90% for 10 years, 80% for

25 years

• 36 Cells in Series Make a 12V-Class Panel (Voc 19V)

•Two 12V-Class Panels in Series Make a 24V-Class Array (Voc 38V)

9 cells x 4 cells is acommon configuration

• 60 Cells (5x12) in Series Make a 30.2V Nominal Panel (Voc 36.8V)

PV Panel Arrangements

PV Systems

Utility Intertie

Stand alone direct connected

Stand alone PV System

Typical Grid Tie without BatteryTypical Grid Tie without Battery

20 panel 2.5 kW PV System Santa Rosa CA

DC Disconnect & Inverter

TOUMeter

Metering Data

TOU rate 31¢/kwh Noon to 6PM (peak solar production); non-peak rate 11¢/kwh

Quantifying the Resource

Location, Location, Location

PV Mounting SystemsPV Mounting Systems• Does your site location need to meet special building

requirements? • What is the maximum wind speed that it must be designed for?• What is the maximum snow loading that it must be designed for?• What structures best use the soil type in your area?• Can you drive piers directly into the ground or do you need

concrete? This will require a geotechnical study of the site and can result in a significant cost savings.

• Can you use a ballasted system?• What height does your system need to be to avoid being covered

by snow, or vegetation?• If you decide to track, what are the lowest temperatures that

system will see?

Single Axis TrackingSingle Axis Tracking

Tracker A:Individual drive for each row.Electric screw jack driveBacktracking controllerVariable spacing between rowsHeight can be modified by userSite welding required

Tracker B:Single drive for multiple rowsElectric screw jack driveBacktracking controllerHeight limited by size of support columns and Drive support.Fixed row spacingSite welding requiredSite needs to be flat and level

Tracker C:Single drive for multiple rowsElectric screw jack driveBacktracking controllerHeight limited by size of support columns and Drive support.Fixed row spacingSite welding requiredSite needs to be flat and level

Tracker D:Single drive for multiple unitsElectric screw jack driveBacktracking controllerHeight limited by size of support Fixed row and column spacingSite welding requiredSite needs to be flat and level

A 2 AXIS A 2 AXIS

B 2 AXISB 2 AXIS

C 2 axisC 2 axis

Your roof top is valuable real estate, without the permitting problems associated with brownfield installations

Rack PV roof mounting systemAccepts most standard PVRoof loading dependent on tilt angleFrom 2 lbs/ft 2 with penetrations to a ballasted system with no penetrations.

Examples of Roof Top InstallsExamples of Roof Top Installs

Phizer = KW 337 Tilt Angle 5 deg. Number of Modules 1,372

California Residence2.5 kW, 20 panels

DC Circuit CombinerDC Circuit Combiner

PV ARRAYPV ARRAY14 modules in series forms one string 10 strings in parallel form an array

Combiner box

Inverter Input

1 MW PV Array1 MW PV Array

Sub Array Combiner Box with String Monitoring

Field Combiner Boxes

Grid Tie Inverter

The grid tie inverter must synchronize its voltage & frequency with that of the grid. A typical modern GTI has a fixed unity power factor. Grid-tie inverters are also designed to quickly disconnect from the grid if the utility grid goes down. This requirement ensures that in the event of a blackout, the inverter will shut down to prevent harm to line workers who are sent to fix the power grid.Peak power tracking voltage: This represents the DC voltage range in which the inverter will operate. The designer must configure the strings so that during the majority of the year, the voltage of the strings will be within this range. This can be a difficult task since voltage will fluctuate with changes in temperature.

Most grid-tie inverters include a maximum power point tracker on the input side that enables the inverter to extract an optimal amount of power from its intended power source.

Grid Tie Inverters

Prewired System with Inverter, Transformer & Fused Combiner Boxes

Concentrated Solar Power CSP

Rick Downer – POWER Engineers Inc.IEEE IAS April 18, 2011