Transcript Slide 1

Solar Energy: Is It Feasible
In Greenhouse Operations
By Paul A. Thomas,
University of Georgia
2006 Oklahoma Conference
A naturally balanced budget
Fact:
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
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!
HEATING ENERGY
Energy Source
Comparitive Cost
6/1/2005
(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
Types of Solar Power: Electrical
Who are the biggest users
of Solar Power…Hippies?
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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 systems
Support the outdoor security lighting, the
swimming pool and the domestic hot water
system.
Shell
The Big Players
In Solar Technology
Cumulative Installed PV in the US
Total On-Grid
140
120
MegaWatts(peak)
100
80
Total Off-Grid
Source: The 2000 National Survey Report of
Photovoltaic Pow er Applications in the U.S.
For the IEA Co-Operative Program on PV
Pow er Systems. Prepared by Paul D.
Maycock and Ward Bow er.
60
40
20
0
1992
1993
1994
1995
1996
Year
1997
1998
1999
2000
Efficiency Evolution In Solar Power
ELECTRIC ENERGY
Energy Source
Levelized Costs
*** Environmentally Sound
(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**
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 ***
NR
!
!
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 Greenhouse
Uses For Solar Technology
Horizontal Air Flow Fans
Cooling Pad Pumps
Emergency Lights
Photoperiod Lighting
Heating Pads
Water Heaters
Well / Storage Water Pumps
Auto Shade Cloth System
Computer 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.
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$10.00
4/1/2000
$20.00
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2/1/2000
Typical Yearly Saving Curve
For Solar Power
Savings With Photovoltaics
$110.00
$100.00
$90.00
$80.00
$70.00
$60.00
$50.00
$40.00
$30.00
Monthly Savings
Moving Average
$0.00
So What Does It Take
To Install a PV System
1: Assess Your Energy Needs
In 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 the
Amp-hours increase!
This allows you to
configure how many
volts, at how many
amp-hours your need
Wire Sizes
Resistance
eats power!
The more amps
you send, the
thicker the
wire needs to
be……and the
longer the run
of wire, the
more amps
you need!
2: Determine The Type of Solar
Panels You Wish To Use
How Panels Are Rated
BP 4175 – Silicon-nitride mono
Rated Power (Pmax): 175 watts
Power tolerance: ± 5%
Nominal voltage: 24 volts
Limited Warranty: 25 years
$ / watts generated
Solar Energy Works In The South!
Solar power incident on a collector at
30 deg. South, winter day.
Wm-2
1000
Steered collector
slanted
500
horizontal
rise
time
set
Panel Orientation
• Affects output!
Charge Controllers
Prevent 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 …they
can explode! Golf cart
batteries 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 planned
for 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
Absolutely
required 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!