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 person? 416 m 2 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!
Comparitive Cost 6/1/2005 HEATING ENERGY Energy Source (Dollars per 90 mm. BTU) 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? • • 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
Efficiency Evolution In Solar Power
ELECTRIC ENERGY Energy Source Levelized Costs *** Environmentally Sound (Cents per k. Wh) ! 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.
Typical Yearly Saving Curve For Solar Power
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
S L O R A A P E N S L $ / 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
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!
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