Overview of Photovoltaic and Solar Hot Water Systems

1. Overview of Photovoltaic and Solar Hot Water Systems Mike Morris National Center for Appropriate Technology New England Farm Energy Conference Manchester, NH March 16, 2010

2. Photovoltaics (“Solar electric”) solar cell PV panel or module • Typical cost $7 per peak watt of DC (direct current) power. • Add inverter to convert DC to AC (alternating current). solar array

3. Electricity 101 • Most panels 12, 24, or 24 volts and 5-200+ watts. • Amps X Volts = Watts • Wire in series to increase voltage or in parallel to increase amps. From Backwoods Solar, www.backwoodssolar.com For example, two, 12-volt panels wired in series runs a 24-volt DC pump.

4. Siting • Panels very sensitive to shade. • Array should be un-shaded from at least 9 AM - 3 PM. • Move array to avoid shading, or oversize array.

5. Solar mounts • Pole mounts, roof mounts, trackers (active or passive). • Mount collectors at an angle equal to your latitude for year round performance (43 degrees in Manchester). • For better summer production, decrease tilt angle • For better winter production, increase tilt angle

6. Do panels have to face south?

7. Agricultural Uses • Common • Electric fence chargers • Pumping • Lighting • Small motors, e.g. fans • Irrigation system surge valves • Less common • Wheel line (side roll) sprinkler mover. • Solar tractors

8. Solar Pumping

9. How a Solar Pumping System Works PV Array Motor/Power Controller Storage Tank Pump/Motor

10. Work with a dealer.

11. Solar (DC) water pumps: many to choose from Surface Pumps Submersible Pumps Suncentric Slowpump Solar Force Solar Ram Shurflo 9300 Series Lorentz PS Grundfos SQ Flex

12. FAQs • How is the system sized? • Batteries? Or no batteries? • Tracking or fixed rack? (Or trailer mount?) • Reliability? Durability? Vandalism? • AC or DC pump? • Diaphragm pump? • Can I run my sprinkler irrigation system with solar panels? • How do PV, wind, and (gas, diesel, propane) generator compare?

13. Tomlinson Ranch, Gold Creek, MT • 25 cow-calf pairs; 2-3 miles from power • Two 120-Watt solar panels • Submersible diaphragm pump (DC) delivers 1 GPM from 160’ well or 900 GPD • Cost of solar components: $3,200 • Benefits: Improved reliability and convenience, compared to gas-powered generator

14. Schraudner Ranch, Lavina, MT • 150 cow-calf pairs; over a mile from power • Seven 60-Watt solar panels (trailer-mounted) • Submersible centrifugal pump (AC) delivers 6.5 GPM from 60’ well or 3,600-4,000 GPD. • Cost of solar components: $10,650 • Benefits: Increased forage base to extend grazing season; reduced pressure on riparian area; water source during drought.

15. Ueland Ranch, Anaconda, MT • 500 cow-calf pairs; ½ mile from power • Twelve 64-Watt solar panels • Submersible centrifugal pump (DC) delivers 17 GPM (Feb. through April) from 50’ well. • Cost of solar components: $7,700 • Primary benefits: Fisheries benefits from reduced pressure on riparian areas, drinking water for cattle at feeding area.

16. Sauerbier Ranch, Alder, MT • 350 cow-calf pairs; >5 miles from power • 24 120-Watt solar panels on two tracking racks • Surface piston pump (DC) delivers 11 GPM or 7,500 GPD from stream. • Cost of solar components: $24,500 • Primary benefits: Increased forage base, increased herd size, fisheries benefits for rare population of West Slope cutthroat trout.

17. Sauerbier Ranch, cont’d • Pumps surface water over two miles to the top of a ridge, against over 400 feet of head. • Fills 8,000 gallon storage tank and six 1,000+ gallon stock tanks

18. Solar Water Heating (“Solar thermal”) • One of the most cost-effective uses of solar energy. • Currently eligible for 30% federal tax credit. • Image problem dating back to the 1980s; modern equipment works very well. • Suitable for any farming operation that uses a lot of hot water. • Dairies should probably do heat recovery on refrigeration system and/or heat exchange on milk first. • Works well with radiant floor heating.

19. The basic idea (with many variations) From www.builditsolar.com

20. Flat Plate Collector SC Solar, Inc. • Durable copper, aluminum and glass design • Sheds snow well because collectors get warm

21. Flat Plate Collector Drawing courtesy of SC Solar, Inc.

22. Evacuated Tube Collector SC Solar, Inc. • New technology; most expensive. • Highest temperature output. • Do not shed snow & ice.

23. Transfer Fluids • Propylene Glycol- Non-toxic • Ethylene Glycol- Toxic • Hydrocarbon Oil (bray oil) • Synthetic Oils • Distilled Water • De-mineralized Water • Potable Water

24. System Types Active vs. Passive • Active systems use a pump to circulate fluid • Passive systems rely on tendency of hot water to rise. Direct (“open loop”) vs. Indirect (“closed loop”) • Direct systems use potable water in the solar collectors • Indirect systems use water or glycol in a separate loop from the potable water.

25. Passive Batch System

26. Active Indirect System (“Drainback”) System controller measures temperature difference between sensors. ON 8-20 difference OFF 3-5 difference

27. Solar Water-Heating for Greenhouses • Design issues • Freeze protection a must. • No toxic fluids around crops or leaking into soil. • Need to dump heat (or disable) in summer months, if sized for winter needs. • Backup heating system desirable. • Tubing can be buried or above-ground, depending on use of greenhouse.

28. Cherry Research Farm, Goldsboro, NC • Cost $8,000; $3,900 after NC and federal incentives. • 250 gallon water “drain down” system • Cut propane costs from $3,000 to $1,000 per year.

29. Thank you for your attention! NCAT: www.ncat.org or 1-800-ASK-NCAT ATTRA: www.attra.org or 1-800-346-9140 Mike Morris: mikem@ncat.org or 919-251-9680 Farm Energy resources: www.attra.org/energy