Post on 22-Jan-2016
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Solar Energy: Is It FeasibleSolar Energy: Is It FeasibleIn Greenhouse OperationsIn Greenhouse Operations
By Paul A. Thomas, By Paul A. Thomas, University of GeorgiaUniversity of Georgia
2006 Oklahoma Conference
A naturally balanced budget
Fact:
A patch of 100 square miles of open space covered with efficient solar panels such as in Nevada, where sun rays are powerful, could generate all the electrical power needs of the United States.
National Renewable Energy Laboratory
FACT!
Making sense of that statement….
How much area is this per person?
416 m2 per person 4,500 square feet to meet the average persons energy needs
Ways of using solar energy
• Direct heating of flat panel (fluids, space heating)
• Passive heating of well-designed buildings
• Thermal power generation (heat engine) via concentration of sunlight
• Direct conversion to electrical energy
Types of Solar Power: Thermal
• Active • Passive
Passive Solar Storage (Heat)
Thermal Panel Features
Hot Water Floor Heating
Solar water heating systems are ideal for greenhouses that use hot water systems under the floors. It is very efficient.
Hot water systems do
require planning, and
a backup heating
system!
Energy Source6/1/2005
Comparitive Cost (Dollars per 90 mmBTU)
Coal $ 816.00
Gas (Natural, Propane) $ 900.00 / $1360.00
Heating Oil $ 1,467.00
Hydro-Electric Not applicable
Biomass $ 750.00
Wind Generated Not Applicable
Solar Heat $ 3,000.00
Retail Electricity (General ) $ 3,065.00
Wood $ 709.00
Nuclear Not Applicable
Photo-Voltaic Not Applicable
HE
AT
ING
EN
ER
GY
Types of Solar Power: Electrical
Who are the biggest users of Solar Power…Hippies?
• The National Park Service
• The Department of Transportation
• State Governments
• Primary and Secondary School Systems
• Most Universities
• Large Corporations
• California / Arizona / Nevada Homeowners
Countries Other Than the U.S.!
What Does The White House Think Of Solar Power?
In 2002, George Bush had 167 Solar Panels installed at the white house, and two solar hot water systems installed. The systemsSupport the outdoor security lighting, the swimming pool and the domestic hot water system.
Shell
The Big PlayersIn Solar Technology
Cumulative Installed PV in the US
0
20
40
60
80
100
120
140
Meg
aWat
ts(p
eak)
1992 1993 1994 1995 1996 1997 1998 1999 2000
Year
Total On-Grid
Total Off-Grid
Source: The 2000 National Survey Report ofPhotovoltaic Power Applications in the U.S.For the IEA Co-Operative Program on PV Power Systems. Prepared by Paul D.Maycock and Ward Bower.
Efficiency Evolution In Solar Power
Energy Source*** Environmentally Sound
Levelized Costs (Cents per kWh)
Coal 4.8 – 5.5
Gas (Natural, Propane) 13.9 – 20.2
Heating Oil 9.0 - 18.0
Hydro-Electric 5.1 – 11.3** NR
Biomass 5.8 - 11.6
Wind Generated 3.8 - 6.0 ***
Solar Heat 11.0 – 15.5***
Retail Electricity ( General ) 8.70 – 19.0
Wood 10.0 – 36.0
Nuclear 11.1 – 14.5 NR
Photo-Voltaic 12.5 - 20.0 ***
EL
EC
TR
IC E
NE
RG
Y
!
!
!
Cost Of Electricity Rising Slowly
Cost Of Solar Energy Is Declining Rapidly !
Solar Technology Fits!
Solar Farms?
Solar Energy Works In The South!
VERY GOOD!
Roof Top Solar Facility
The conversion is accomplished by the material absorbing light and ionizing crystal atoms, thereby creating free, negatively charged electrons and positively charged ions.
These then go to opposing sides of a charged system and form a flow of electrons or “electricity!
Source: Karl W. Boer
Practical GreenhouseUses For Solar Technology
Horizontal Air Flow FansCooling Pad PumpsEmergency LightsPhotoperiod LightingHeating PadsWater Heaters Well / Storage Water PumpsAuto Shade Cloth SystemComputer Controll systems / Solenoids
Consider the HAF Fan
• It runs during “peak cost” hours during the winter.
• It is needed most at night if pad and fans system is used during the summer.
• The SUMMER sun could power the pad and fan pump system directly, and charge the batteries to run the fans at night! In WINTER the system could run the fans during the day using direct DC power.
Typical Yearly Saving Curve For Solar Power
Savings With Photovoltaics
$0.00
$10.00
$20.00
$30.00
$40.00
$50.00
$60.00
$70.00
$80.00
$90.00
$100.00
$110.00
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/20
00
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/1/2
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0
11
/1/2
00
0
12
/1/2
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0
1/1
/20
01
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/20
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3/1
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10
/1/2
00
1
Monthly Savings
Moving Average
So What Does It Take To Install a PV System
1: Assess Your Energy NeedsIn Terms Of Watts Per Hour
Energy Assessment
• Add up the watts used on each appliance.
• Determine how many hours / day
• Determine seasonal use patterns
• Ad up the total amp-hours needed to be supplied during the greatest period of use for your system’s voltage. Design accordingly!
The Water Wheel
If you have a small, old fashioned water wheel, a hose, and an adjustable spray nozzel you can understand electricity!
If you point the hose at the water wheel, the wheel turns…increase the pressure (volts) or increase the volume of water (amps), and you’ll find the increased force (watts) makes the wheel turns faster!
Basic Electricity
• Amphere = The number of electrons flowing past a point at any given time. (gallons per minute = volume!)
• Volts = The pressure the electrons are under. Remember pounds per sq inch (PSI) for water!
• Watts = The total force the electron flow exerts
• Ohms = The resistance the hose exerts on the flow of the water.
Here Are Some Household Examples
• Typical Electrical Appliance Wattages
Television: 300-400 running watts, 300-400 starting/surge watts
Microwave oven: 700 running watts, 1000 starting/surge watts
Furnace blower (1/3 hp): 600 running watts, 1800 starting/surge watts
Vacuum cleaner: 600 running watts, 750 starting/surge watts
Refrigerator/Freezer: 800 running watts, 2400 starting/surge watts
Toaster: 1200 running watts, 1200 starting/surge watts
Coffee maker: 1200 running watts, 1200 starting/surge watts
Stove element burner: 1500 running watts, 1500 starting/surge watts
Water heater: 5000 running watts, 5000 starting/surge watts
Water well pump (1/2 hp): 1000 running watts, 3000 starting/surge watts
Sump pump (1/3 hp): 700 running watts, 2100 starting/surge watts
Washer: 1440 running watts, 1440 starting/surge watts
Dryer: 5520 running watts (which is why it was hard to use)
Series: Volts increase, Amp-hours remain the same
Parallel: Volts remain the same and theAmp-hours increase!
This allows you to configure how many volts, at how many amp-hours your need
Wire Sizes
The more amps you send, the thicker the wire needs to be……and the longer the run of wire, the more amps you need!
Resistance eats power!
2: Determine The Type of Solar Panels You Wish To Use
How Panels Are Rated
BP 4175 – Silicon-nitride monoRated Power (Pmax): 175 wattsPower tolerance: ± 5%Nominal voltage: 24 voltsLimited Warranty: 25 years
SOLAR PANELS
$ / watts generated
Solar Energy Works In The South!
riseset
time
Wm-2
1000
500
Steered collector
Solar power incident on a collector at30 deg. South, winter day.
slanted
horizontal
Panel Orientation
• Affects output!
Charge ControllersPrevent overloads and night energy leakage
MPPT vs PWM Controllers
Maximum power-point tracking. It is like a transmission system in your car, it adjusts charging based on need or demand of the battery…very accurate and efficient.
Pulse Width Modulation – Reduces charge current according to the batteries need or status. It slows charging down when near fully changed to prevent overloads. Good, but less efficient.
MPPT vs PWM Controllers
MPPT is much,
much better at
maintaining
battery life than
PWM controllers,
and more costly!
Solar Batteries• Output measured in Amp-Hours!
Example: A battery which delivers 5 amperes for 20 hours delivers 5 amperes times 20 hours, or 100 ampere-hours.)
Types of Batteries
• Starter Batteries - This lead plates &rapid release of power, if discharged often, losses battery life
• Deep Cycle Batteries - Thicker led plates and can be discharged often and fully without loss of life
Flooded - Require frequent addition of battery acid
Sealed - Require less care, difficult to balance
Gel - Requires very little maintenance – Balance?
What Kind Is Best
A typical 6-volt golf cart battery will store about 1 kilowatt-hour of useful energy (6 volt X 220 amp-hr X 80% discharge = 1056 watt-hours).
Avoid using deep-cycle marine batteries …theycan explode! Golf cartbatteries are designed for complete discharge!
Batteries Designed for Solar
Rolls-Surrette Tasman
Batteries Designed for Solar
Battery Storage
Needs to be isolated
Requires maintenance
Must be vented!
Needs to be plannedfor peak demands
Safety equipment required!
DC to AC Power Converters
• Reduces the cost effectiveness of solar
• Must be “scaled” to the load of the system
You May Need to Convert to Direct-Current Equipment
• Lighting and fans are easy to swap out.
• Sump-pumps, solenoids, motors are not!
• The RV industry is 10 years ahead of agriculture, in that almost anything you can use in an RV is now sold as a DC unit!
Basic Solar (PV) System
Basic Greenhouse System
Dual-Backup Electrical System
Grid Connect System System
Grid Access Control Systems
Control excess or redirected power flow to the grid system
Absolutelyrequired by all power companies
Being Your Own Utility Company
The federal PURPA regulations passed in 1978 allow you to interconnect a suitable renewable energy powered generator to your house or business to reduce your consumption of utility supplied electricity.
This same law requires utilities to purchase any excess electricity production at a price (avoided cost) usually below the retail cost of electricity.
The Greenhouse Of The Future?
The Farm Yard of the Future!
SUMMARY
• Solar energy may be useful as primary electricity source if energy efficient, direct-current equipment is used in the greenhouse facility, or if battery efficiency improves.
• Solar energy is already a useful backup or emergency energy source for key systems such as pumps, lights, vents and fans.
• As cost decreases and solar panel efficiency increases, the use of a combined solar electricity and thermal water solar systems to heat greenhouses may be the best way to go. Hot water is the most efficient transfer method!