Gary L. Hawkins, Ph.D.

University of Georgia – Tifton

Agent Training

29 May 2013

SOLAR POWER 101

THE BASICS OF SOLAR ENERGY

BASIC TERMINOLOGY

• Solar Electric

• Uses Solar Panels or Photovoltaic (PV) Panels

• Solar Thermal

• This is Solar Hot Water Heating

ADVANTAGES OF PV TECHNOLOGY

• Reliability

• In harsh conditions the system has been shown to work

• Durability

• Most modules are guaranteed for 25 years with production even after that

• Low maintenance cost

• Systems require periodic inspection and occasional maintenance

• No fuel cost

• No liquid fuel to deal with to produce power

• Reduced sound pollution

• Only sound produced is from the pump and tracking system if used

ADVANTAGES OF PV TECHNOLOGY

• Photovoltaic modularity

• Modules can be added to increase power

• Safety

• No fuel required to be stored or used

• Independence

• Based on the use, it system can be a stand alone system with no grid tied

components

• Electric grid decentralization

• For larger systems a small decentralized power station can reduce power outages

DISADVANTAGES OF PV TECHNOLOGY

• Initial Cost

• The cost of a solar power system generally has to be expended up front and benefits

received over time

• Variability of solar radiation

DISADVANTAGES OF PV TECHNOLOGY

• Energy storage

• If power is required outside daylight hours, then batteries are generally needed.

These batteries are high amp-hours, seep cycle batteries. Cost can range from $250

- $500.

• Efficiency improvements

• The use of solar power for home, office, barn, etc. use FIRST requires that energy

conservation be practiced

• Education

• Learning how solar systems are different from the electric grid is one of the first

things that needs to be understood from potential users of the systems

OUTLINE

• PV System Components

• Terminology of Electricity

• Electric Circuits

• Designing a small PV system

• Sizing a system

PV SYSTEM COMPONENTS

• Photovoltaic Cells

Picture from http://upload.wikimedia.org/wikipedia/commons/9/90/Solar_cell.png

SOLAR CELL CONSTRUCTION

PV SYSTEM COMPONENTS

• Module or Panel (generally interchangeable with each other)

PV SYSTEM COMPONENTS

• Array – One or more panels joined together for a specific voltage or amperage

PV SYSTEM COMPONENTS

• Charge Controller

• Battery

• Inverter

• DC Load

• AC Load

A complete

solar power

system

OUTLINE

• PV System Components

• Terminology of Electricity

• Electric Circuits

• Designing a small PV system

• Sizing a system

TERMINOLOGY

• Electricity

• Flow of electrons through a circuit

• Volt (V)

• A unit of force (electric pressure) that has potential to cause electrons to flow in a wire

TERMINOLOGY

• Ampere or Amp (A)

• Unit of electrical current flowing through a wire

• Watt

• A unit of electrical power equivalent to a current of one amp under a pressure of one

volt.

EQUATIONS

• Power = Watts (W) = Volts (V) X Amps (A)

• 1000 watts = 1 kilowatt

• Energy = Watt-hours(Wh) = Watts X hours

• 1000 Wh = 1 kilowatt-hr (kWh)

• Amp-hour (Ah) = amps X hours

EQUATIONS

• Pop Quiz

How much electrical energy is consumed if a 100 watt light bulb is used for 10

hours?

• 100 watt bulb X 10 hours = 1000 watt-hours or 1 kWh

OUTLINE

• PV System Components

• Terminology of Electricity

• Electric Circuits

• Designing a small PV system

• Sizing a system

ELECTRIC CIRCUITS

• Electric circuit is a continuous path of electron flow from a voltage source, such as a

battery or PV panel, through a wire to the load and back.

Battery or

Solar Panel

Battery

Solar

Panel

-1.5

-1

-0.5

0.5

1.5

012345678

AC curve

DC curve

ELECTRIC CIRCUITS

• Series circuit is a circuit where the positive (+) end of each panel is connected to the

negative (-) of the next panel.

• This configuration increases the voltage of the system but NOT the amperage.

ELECTRIC CIRCUITS

• Parallel circuit is a circuit where the positive (+) end of all panels are connected together.

• This configuration increases the amps but NOT the volts.

ELECTRIC CIRCUITS

• Hybrid circuit is a circuit where part of the panels are connected in parallel and part are

connected in series.

• This configuration increases both the amps AND volts.

OUTLINE

• PV System Components

• Terminology of Electricity

• Electric Circuits

• Designing a small PV system

• Sizing a system

DESIGNING A SMALL PV SYSTEM

• Let’s take a small cattle watering system:

• How many cows are we watering? – 25 cows

• How deep is the static water level in the well? – 40 feet

• How far does the water have to be pumped? (this is the dynamic head) – 300 feet up

hill 30 feet

• What size pipe are we using? -- 1 inch pipe

• Do we have a storage tank? – storage tank at top of hill, tank is 5 foot tall

DESIGNING A SMALL PV SYSTEM

• Where to start?

• Generally a lactating cow needs 20 gallons of water daily

• Therefore with 25 cows we need 500 gallons of water DAILY

• Assuming only 5 hours of sun daily (this should be very conservative figure)

• Then we need 100 gallons per hour to be pumped

• Or 1.7 gallons per minute to provide ample water for all cows

DESIGNING A SMALL PV SYSTEM

• What’s next? – Designing the Dynamic Head requirement

• How deep is the static water level in the well? – 40 feet

• How far does the water have to be pumped? (this is the dynamic head) – 300 feet up

hill 30 feet

• What size pipe are we using? -- 1 inch pipe

• Do we have a storage tank? – storage tank at top of hill, tank is 5 foot tall

• All of this data will be used to determine the amount of head to pick a pump.

Total

Dynamic

Head

Calculation

http://www.michigan.gov/documents/deq/deq-wb-dwehs-gwwfwim-section7_183032_7.pdf

80 feet

1 foot

300 feet

.305 feet/100 ft

1.5 inch PVC

6 gpm

1.5 inch PVC

.305 feet/100 ft

0.2 foot

82 feet

50 psi

115.5 feet

197.5 feet

RENEWABLE AND

ENERGY EFFICIENCY

REBATES, TAX

INCENTIVES, REFUNDS

HTTP://WWW.DSIREUSA.ORG/

QUESTIONS?

Gary L. Hawkins

University of Georgia

Tifton Campus

229-386-3377

ghawkins@uga.edu