Red Rocks Community College

ENY 130 Grid-Tied PVFall 2009Module 2

Grid-Tied Applications:

Anything that utilizes electricity

Flexible design works for both residential and commercial applications

Advantages of Grid-Tied

Improved Economics: No need for a large system to cover all needs.

No need for the cost of battery back up High start-up loads can be provided by the grid PV power always offsets grid power and reduced electrical bills

Net metering

Design Flexibility Most any size system can be connected to the grid

Though must be able to support the grid voltage Cannot exceed 600 volts

Increased reliability Two independent power systems-redundancy Can offset electrical needs during potential brown out

Disadvantages of Grid-Tied

When utility power goes down, so does the power from the inverter to the building.

You must have a separate system beyond the grid-tied portion of your system for the PV to provide power while the grid is down.

Grid-Tied Components

Source: Powered naturally

Watt vs. Watt Hour This is often a confusing concept

A PV system is sized by “Watts” The PV power produced is the watts

multiplied by the duration of production. A 4kW (kilowatt = 1000 watts) PV system

producing for 6 hours produces 24000 watts, or 24 kWh (kilowatt hours)

Which produces more work?

Two guys working hard….

Or 1 PV module laying in the Sun ?

Energy Comparisons Average home consumes 22

kWh/day(8000kWh/yr) 1 person generates 75w/hr (x 8hrs=.6 kWh/day) 1 ton coal = 2460 kWh (costs $300)

32,800 labor hrs (value@$20/hr = $656,000) 1 Barrel of oil = 1700 kWh (costs $100)

22,600 labor hours (value@$20/hr=$450,000)

1 Solar Module = 1.2 kWh/day(40yrs is 14,500 kWh)

(Value @ $20/hr = $300,000) 16 Labor hours 1 solar module laying in the sun produces as

much energy as 2 people working

AC / DC

Alternating Current -where the direction of current flow reverses at frequent intervals. This is the current provided by utilities

Direct Current -where electrical current flows in one direction. Typical of batteries and PV cells.

Alternating Current wave

Direct Current…wave

Electrical Circuits

Electrical Circuit is the continuous path of electron flow from a voltage source.

Open Circuit- when there is no completed path for current. Switched off or wires disconnected

Closed Circuit- when path is completed and current flows. Switched on.

Series and Parallel Circuits

Series Wiring….. Which one? …… The voltage is added while the

amperage stays the same

Parallel Wiring…..which ones?

….. The amperage is added while the voltage stays the same

Series and Parallel wiring of Modules

Series and Parallel Exercises in Book

End of 2