Solar Schoolhouse and San Mateo CollegeDesigning and Installing Solar Electric Systems

Types of Solar Electric SystemsFor Technology Teachers

San Mateo CollegeMay 17, 2008

Disclaimer

• This workshop does not certify you and

• Solar Schoolhouse and San Mateo College are not responsible for anything you do with this knowledge

Three Basic Types:

Stand Alone Simple Grid Tied

Grid Tie with Battery

Grid Tie Solar Electric Systems

Quick View

Simple Grid-tie system(Utility intertie)

Solar Array

Inverter Distribution Panel

Utility

Attaching Rack System To The Roof

Mounting bracket bolted into rafter; rack then bolted to mount.

Series Wiring with MC Connectors

Conduit From Array to Disconnects

Simple Grid Tie with Two Inverters: Disconnects, Inverters, and Subpanel

To PGE DisconnectAnd toMeter

Subpanel

Solar AC in fromInverter

Lightning surge arrestor

AC from inverter to

PG&E disconnect

then back to breakers

Stand Alone Systems

I.e. No Grid

SIMPLE: Load directly powered by solar photovoltaic module

With Storage: Solar ModuleBatteryLoad

Stand Alone Residential System

Solar Array

Charge Controller

Battery

DC to AC Inverter

Distribution PanelAC

Distribution PanelDC

Small Stand Alone

System

(to power an office)

Solar Array

Charge Control

Storage: Battery

“Fuel Gauge”

Inverter DC to AC

Roof mount Solar Array: 4 SM55220 Watts wired in parallel

Stand Alone System Components

Disconnect Between Solar Panel and the Battery (via Charge Control)

Breakers and fuses must be DC rated. Can purchase “special for PV application” equipment.

In this system we used Square D QO which is ok for DC up to 24 volts

Charge Control for Battery:note display and battery type selector

Storage: Battery:Flooded, Sealed, AGM, or Gel

Fuse: Circuit ProtectionMust be large enough to allow maximum designed current (+ x%) to flow

through circuit and blow before wire overheats (maximum size determined by ampacity rating of wire).

Inverter: DC to AC Pure sine wave: Turns DC electricity of PVs and Batteries into AC current.

DC in

AC out

Wire Strategy

• Select wire sizes that minimize Voltage Drop: based on distance and current

• Select insulation types depending on where wire is located and whether or not it is in conduit. (UV, temperature, moisture)

• Be strategic in which voltage you use for system: depends on wattage and length of wire runs

Balance of System

Inverter

Charge Control

“Fuel Gauge”

Battery

Safety at Schools, etc

• Follow good wiring practice: keep unshielded wire out of the reach of people: in conduit, behind transparent barrier such as glass or lexan.

• Fusing, breakers, ground fault protection. DC lines must use DC rated equipment.

• Batteries must be inaccessible to unauthorized people…i.e. locked

• Use Adequate Mounts for Solar Panel

Larger Stand Alone Systems: 1 kw

Combiner Box

MX60 Charge Controller in Action

Grid Tie with Stand Alone Capability

Solar Array

InverterDistribution

Panel

ChargeControl

Battery

Utility