12.4 Wind Hybrid Systems

Frank R. Leslie, B. S. E. E., M. S. Space Technology, LS IEEE

3/15/2010, Rev. 2.1

fleslie @fit.edu; (321) 674-7377

www.fit.edu/~fleslie

In Other News . . .

Wind Turbines in Chicago Tribune 3/14/10http://www.istockanalyst.com/article/viewiStockNews/articleid/3946002

(Source: Chicago Tribune) By Julie Wernau, Chicago Tribune “Mar. 14--Months have passed since anyone has waved hello

to one another in Waterman or Shabbona in rural DeKalb County. Some people claim they've even stopped going to church to avoid having to talk to former friends.

"It's gone. The country way of living is gone," declares Susan Flex, who lives in Waterman with her husband and their nine children.

The animosity stems from the greenest of energy sources: a wind farm. “

Complaints of noise and light flicker

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12.4 Overview: Wind/Solar Hybrid Systems

Erratic energy sources like wind and solar are not dispatchable, that is, available on command of utility dispatchers

Sometimes or often, the wind blows when it is cloudy, or the sun shines when the wind is calm

A system that combines various energy sources is called a “hybrid” system

Diesel generators are often used for “reliable” power, and wind or solar are used to decrease the fuel costs

Studies of a site can indicate the optimal combination of wind, solar, and diesel (or gasoline) to provide power at the lowest overall annual cost

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12.4 About This Presentation

12.4.1 Energy Mixture Availability12.4.2 Hybrid Mixes12.4.3 Economics of System Combination12.4.4 Hybrid System Design12.4.5 Balance of System (BOS)12.4.6 Power Control12.4.7 Power Availability12.4.8 Hybrid System Examples12.4 Conclusion

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12.4.1 Energy Source Mixture Availability

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Assessment of wind vs. solar for a specific site uses a small representative turbine or anemometer and a PV moduleThe energy ratio plotted throughout a year

indicates the relative energies available, which can then be compared with system cost ($/kWh)

The actual energies available can then be compared with longer-term climate data to estimate annual variations

Life-cycle costs of the two systems must be included to get a comprehensive determination of an optimal system design

One of the systems might be omitted if the energy contribution is less than ~5% of the totalWhy bother if $/kWh is too high?

12.4.1 Energy Source Cost Choices

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Assess cost of various mixes of energy, enter total costs, sketch contours to seek lowest cost region

Wind

Solar

Fuel

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$HypotheticalCost Line

http://dna-view.com/triangle.htm

0%S, 100% F100%W, 0% F

33.3%S, 33.3%W, 33.3% F

12.4.2.1 Wind/Diesel

Wind/diesel systems work well where sunlight is limited, as above the Arctic Circle or below the Antarctic Circle

Wind turbines have worked well at the South Pole Station, but diesel generators are also hard at work there

Gasoline engines also can be used, but may lack the life of a heavy diesel engine

Diesel fuel costs $2.90; gasoline $2.77 as of 3/15/2010

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www.renewableenergyaccess.com

12.4.2.1 Wind/Diesel

3/15/2010 diesel prices

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12.4.2.1 Wind/Diesel

1970-2009 crude oil $ vs. production million barrels per day

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12.4.2.2 Solar/Diesel Hybrids

Solar power has a much more stable short term output than wind power; the solar energy is less “volatile” than wind to use an economics term

As the insolation rises in the morning, the diesel engine might be shut down until late afternoon or when clouds reduce solar power for a certain number of minutes

The controller could run the diesel engine only when the battery voltage drops below a very low set point, such as 10.5 voltsThe diesel would be stopped when the battery

voltage rose to approximately 13.9 voltsA battery-charging procedure minimizes the number

of engine starts and ensures full-load engine operation

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12.4.2.3 Diesel Engines

A 9.2 kVA diesel package plant from Genasys Systems in a quieting package (top)

Multiple large diesel sets (bottom)

A small diesel might require 2.5 L/hr at idle and 7.5 L/hr at 14 kW changing somewhat linearly from idle to full load

100315http://www.eere.energy.gov/windpoweringamerica/

12.4.2.4 Propane Engine Generator

Liquefied petroleum gas (LPG) in the United States is primarily propane, but also contains propylene, butane, and butylene

Gasoline-carbureted generators may be converted to propane; often done in pickup trucks in Western US

The Onan (Cummins) generator shown below produces 5.5 kW and costs ~$2970 (~$540/kW)

One gallon/hour of liquid propane will produce ~10kW

100315 http://www.emnrd.state.nm.us/ecmd/html/propane.htm

http://www.merequipment.com/Frequently%20Asked%20Questions/Powergard_Elliott_faq.htm

12.4.2.5 Tripartite Systems

A wind/solar/diesel system is only somewhat more complex than the wind/solar type

The system balance between wind and solar is determined as in a conventional system, adjusting the costs of each to match the available energyIf the sun rarely shines, the solar equipment

would not be cost-effectiveIf the wind rarely blows, the wind equipment

would not be cost-effectiveEach of these sources offsets the need for diesel

consumption, yet including some diesel capacity improves the availability and reliability of power

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12.4.2.6 Fuel Consumption

The rate of diesel fuel consumption is critical to the analysisDiesel fuel costs ~20% more than gasolineBiodiesel is even more costlyFuel transportation raises the actual fuel cost

and must be included in the total priceThe engine speed must be matched to the

generator/alternator to optimize efficiencyWhen the generator runs, it should do so at full

load, charging batteries as necessary, then shutting down completely to save fuel

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12.4.3 Economics of Plant Combination

The location is the prime driver of the cost-analysis

When the remoteness and lack of roads makes fuel-hauling or helicopter transport too costly, the wind or solar components must be increased to ensure reliable power

Mountain-top radio repeaters exemplify the inaccessible site, and access may be limited to hiking or horseback (pack trains) The handset radio has 5W to reach the

repeater, the repeater receiver audio is patched to the 50W transmitter on another frequency, and the high power signal reaches other receivers farther away

Matching of the load times to the energy times determines the need for storage capacity

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Scottish Moor

http://www.windsund.com

12.4.4 Hybrid Installation Design

Some rules from Manwell, et al.:Without storage, the load limits what energy

may be used or extractedLoad matching for time of day limits output as

wellDiesel engines must be sized for highest load

to carry the loads in normal operationThe savings is never greater than the fuel

savings

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12.4.5 Balance of Systems (BOS)

The balance of system must include the necessary fuel tanks, piping, transportation support, etc.

Local shops may be needed to perform engine overhaul, since the distance to civilization may be great

BOS must include means of transporting fuel to the engineIf a truck is normally used to travel to a location

that has fuel, there might not be an extra trip or expenseWith dual truck tanks, one might be used just for

hauling fuel for the generatorThe labor (driver) cost is increased slightly for

getting fuel, but increased greatly if the trip would not have been otherwise made

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12.4.5.1 Balance of Systems (Wiring)

An installation in China

Please don’t do this!

Wiring should be neat and well secured to prevent fires!

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12.4.5.2 Balance of Systems (Diesel)

Fueled systems will require tanks, lines, and possibly pumps

In cold weather, diesel oil thickens, and insulation or heating of the lines may be requiredHot water tubes can be run parallel to the fuel lines

Small car engines may use 3 liters per 100 km (78 mpg)If at 78 mph, that would be 3 L/hr, or to avoid

mixed units systems, approximately 3/4 gallon/hour

A typical 500 gallon tank would hold ~500 hours of fuel, so replacement fuel must be obtained faster than that to keep the tank filled so the generator doesn’t stop

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12.4.5.3 Battery Storage

Batteries provide an “inexpensive” form of storageThey are required for wind and solar energy, but diesel

(gasoline) generators could run to carry the loadFor reliability, some diesel service might expensively be

kept online at all times to avoid starting delaysLarge battery systems require some maintenance

checks but usually last for many years (7-20)A large Uninterruptible Power Supply (UPS) can carry

the load for minutes to hours or longer depending upon the amount of battery ampere-hours that supports it

Adding storage means that the energy available is “leveled” and unnecessary engine starts are avoided

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12.4.5.3.1 Battery Storage (Australia)

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This shipping container contains the controller and a very large battery

http://www.solarshop.com.au

12.4.6 Power Control

System monitoring by computer allows programming of automated supervisory monitoring and determines actions to take in response

The system functions in software might includeStart an engineControl battery chargingControl energy load dumping for wind turbineChange loads to match available powerEngage engine clutchReport alarms to a distant operator

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12.4.6.1 Power Control for Backup Engine-Generator

The engine-generator starting sequence automatically begins when the line voltage sags (drops) below perhaps 105 voltsA transfer switch changes the load from the wind/solar

inverter output to the engine-generator outputThe battery is connected to the starter motor and the

engine is cranked to start under a solenoid-controlled choke fuel enrichment

As the starter turns over the engine-generator, the speed is sufficient to provide voltage to the load

Once the engine is running, the choke is opened to provide a normal fuel mixture

The entire sequence is so fast that lights on the load side don’t noticeably flicker

When inverter power returns for thirty seconds, the load is switched to the inverter (after a delay) and the engine is stopped

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12.4.6.2 Power Control for Continuous Hybrid System

In a full hybrid system, the engine runs continuously and the wind/solar sources subsidize (add to) the available energy, saving fuel by shutting down the engine whenever possible

The inverter is synchronously matched to the power frequency and voltage, providing more or less power as is available

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12.4.7 System Availability

As long as the engine works and the diesel fuel lasts, system availability is high

If the renewable sources are low, the fuel will be used faster (and require replenishment more often)

If the engine fails and there is no storage (battery), the system will only have the varying renewable energy and might not function at all due to voltage variations

Solar energy might carry the load until mid-afternoon, but the wind system would be too variable in many locations

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12.4.8 Example: Alaskan Hybrid Site

Coast Guard Station in Alaska

Wind and solar energy seem to be augmented by five large propane tanks near the base of the turbineIf so, a propane-fueled

generator would be used instead of diesel

There is likely a really long fill hose on the supply boat that can connect to the tanks

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http://www.uaf.edu/energyin/webpage/pages/other_important_topics/hybrid.htm

12.4.8.1 Example: San Clemente Island, CA

US Navy turbine installation to reduce diesel fuel use by a navigation light

NREL determined that cost of energy (COE) was $0.193/kWh vs. $0.45/kWh baseline with all diesel power

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12.4.8.2 PV Installation in Australia

See www.solarshop.com.au for details

060217 http://www.solarshop.com.au/

Diesel generator supplies backup power

12.4 Conclusion: Wind Hybrid

Combinations of energy sources will provide more reliable power than any one source alone --- energy diversity

Diesel, propane, or gasoline engine-generators produce power on demand, and can self-start when the power line voltage is dropping

Natural gas can be piped to some areasWhen wind or solar energy is available, the fueled

generator will shut down, saving its fuel costAlthough overall costs are higher, the power is

more reliable

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Olin Engineering Complex 4.7 kW Solar PV Roof Array

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Questions?

References: Books

Boyle, Godfrey. Renewable Energy, Second Edition. Oxford: Oxford University Press, 2004, ISBN 0-19-26178-4. (my preferred text)

Brower, Michael. Cool Energy. Cambridge MA: The MIT Press, 1992. 0-262-02349-0, TJ807.9.U6B76, 333.79’4’0973.

Duffie, John and William A. Beckman. Solar Engineering of Thermal Processes. NY: John Wiley & Sons, Inc., 920 pp., 1991

Gipe, Paul. Wind Energy for Home & Business. White River Junction, VT: Chelsea Green Pub. Co., 1993. 0-930031-64-4, TJ820.G57, 621.4’5

Patel, Mukund R. Wind and Solar Power Systems. Boca Raton: CRC Press, 1999, 351 pp. ISBN 0-8493-1605-7, TK1541.P38 1999, 621.31’2136

Sørensen, Bent. Renewable Energy, Second Edition. San Diego: Academic Press, 2000, 911 pp. ISBN 0-12-656152-4.

Texter,

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References: Websites, etc.

http://www.uaf.edu/energyin/webpage/pages/other_important_topics/hybrid.htm

http://www.sandia.gov/wind/

http://gttserv.lth.rwth-aachen.de/~sp/tt/gtt-news/gttn_13.html triangle plotting of proportions

http://www.nrel.gov/international/china/pdfs/vp_workshop_2002/wallace_undp.pdf RE systems

http://alaska.bp.com/alaska/beyond_petroleum/limevillage/limevillage.htm Lime Village, Alaska by BP

http://www.eere.energy.gov/windpoweringamerica/pdfs/workshops/2002_wind_diesel/san_clemente_california.pdf

____________________________________________________________________________awea-windnet@yahoogroups.com. Wind Energy elistawea-wind-home@yahoogroups.com. Wind energy home powersite elistmailto:energyresources@egroups.com rredc.nrel.gov/wind/pubs/atlas/maps/chap2/2-01m.html PNNL wind energy map of CONUS windenergyexperimenter@yahoogroups.com. Elist

for wind energy experimenterstelosnet.com/wind/20th.htmlwww.google.com/search?q=%22renewable+energy+course%22solstice.crest.org/dataweb.usbr.gov/html/powerplant_selection.htmlhttp://tonto.eia.doe.gov/oog/info/gdu/gasdiesel.asphttp://www.pruftechnik.com/fileadmin/user_upload/COM/Condition_Monitoring/Products/Online_Systems/VIBROWEB_XP/

Brochure/PRUFTECHNIK_WindBrochure2010_en.pdf

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Notes hybrid

Sorenson p. 851

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