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Solar or Wind ? Here's some calculations on wind and solar for our location in north central Indiana
These are the averages for Kokomo Indiana and Howard County. For the comparison we'll use the 50 Meter data from NREL 70 and 100 Meter data is also provided.
Click any of the above to enlarge. Most of Kokomo Is in the 6 to 6.5 Meters per second zone. The surrounding parts of Howard County are in the 6.5 to 7 Meters per second zone. Multiply Meters per second< M/S > by 2.2 for Miles Per Hour.<MPH> Notice that there's quite a difference between the wind at +150 feet compared to the National Weather Service data for 24 feet up at the top of the page.. For all the calculations we'll use 6 meters per second (that's 13.2 MPH) as the average wind speed. This should be a reasonable value since most small winds systems are not taller that 15 meters. We'll use the published output at 6 M/S in KW times 24 hours and then 365 days. Now there are several Wind Generator choices on the market today, and for reference we'll figure the wind blows the perfect average for the year. Skystreams are rated at 2.4kw full output. From Skystream's own brochure there unit will make 400 Watts an hour in a 6 M/S wind. From that we can calculate that for a day output is 9.6 kWh and for the year the yield is 3504 kWh. (What should be noted is that the manufacturer shows a monthly yield of 450kWh using the "mean" wind speed. Mean wind speed is the midpoint between the annual maximum and minimum wind speeds. Our wind blows @ 40 mph quite often and other times it's calm. From that the "mean" would be 20 mph. This would tend to exaggerate advertised yields. "Caveat Emptor" - let the buyer beware...) Now consider the data on a Kestrel e400 at 6 M/S. The e400 full output is rated at 3.3KW. Power out is 500 Watts at 6 m/s, so for 1 day yield is 12 kWh and for the year its 4380 kWh. Their published yearly yield for 6 M/S is 5000 kWh - very close to our calculations. The Kestrel makes more power -- it's nearly the same cost, and has over 20 years of service in the harsh conditions in South Africa. Next look at the Evance R9000. This is a larger unit, rated at 5 kWh. At 6 M/S the R9000 produces 1100 Watts so on the day 26.4 kWh, and 9636 kWh/year. That's almost 3 times the calculated output of the Skystream. (The Evance data sheet also lists a yield based on mean wind speed, and shows a 30% higher annual yield than we calculate here, similar to the Skystream numbers, which show a 40+% higher yield than the calculations based on average wind speed). Most wind generators need wind Speeds in the 11 to 14 M/S < 24 to 30 MPH > to run at rated output. The wind does blow that hard around here but not all the time. The speed given by NREL takes in the seasonal variations and provided a flat average. Maintenance is an important consideration. One should only consider a wind generator if they are prepared to commit to the maintenance, either performed by themselves, or contracted by the installer. An investment of this magnitude should be protected! The purchase of a small wind turbine should only be done after research of real data. Contact us for more details or data.
So what about the Big Wind generators? Here is the data sheet on the GE 1.5MW Wind Turbine. You'll note that the unit shows only a 400kw output at our 6 M/S and even at the ideal of 100 meters its only 8 M/S and the output would be 900kwh or .9MW. Far from the 1.5mw rating. Rough prices on the above systems are: Skystream, 13-16k installed; Kestrel e400, 18-22k installed; and an R9000 will run 35-40k. Most of the price variance is pole height and foundation work. These are rough estimates to give an idea of scale. To determine an accurate cost, an assessment of the location is required.
Some further points on wind. You need a good open location with no close trees or buildings (The rule of thumb on tower height is that the center of the turbine should be 20' above any obstructions within a 300' radius) and you need the property to be large enough that if the unit falls it falls inside your property lines. So if you put up a 60ft pole you need 60 ft in all directions from the base as clearance. For most locations in the county this is not a problem. Zoning in the city makes small wind an administrative challenge, and in town there's so much turbulence there is very little useable wind
Now lets compare solar to the wind data above.
A 2.4 kW crystalline PV system would cost around 15k - 17k. < a Basic roof mounted system consisting of 10 panels, 1 inverter, and mounting hardware > The Average sunlight exposure in N-Central Indiana for the year is 4.2 "peak hours" per day. < this includes cloud cover and seasonal changes > That's 10.08 kW per day or 3679 kW per year. <The Elkin System is producing more and is showing the production to be closer to 4.5hrs a day > The data from the Elkin System also shows that a 10kw system in Central Indiana will yield nearly 15,000 kWh per year. So for every 1kw of installed rated solar output the yearly yield is 1,500 kWh. (These numbers represent a fixed-mount system.) One great way to improve solar output is the use of trackers. A tracking system changes the panel orientation throughout the day to optimize the angle at which the sun strikes the surface of the panels. Here in Central Indiana, dual axis trackers provide yield improvements of nearly 40% and only add 10 to 15% to the total system cost. (data provided by NREL research, the source of the maps below)
The 2.4kw solar system discussed earlier would cost roughly 17.5k - 19k with a tracking mount, but from the increase of correct angle constant positioning, the daily average peak sunlight is now over 6 hrs a day, yielding 14.9 kWh a day and 5445 kWh for the year. Compare this closely to wind numbers listed above. One other thing to think about is when the power is generated. In most of the Midwest, wind resource is very low in the summer. Most of our wind is in the late fall thru winter and into early spring. Solar yields are lowest when the days are the shortest in winter. When do you use the most power??? Wind makes the most power in winter and solar makes the most in summer. Utility records for power consumption are usually set mid day in the extreme heat of summer, right when solar makes the most power. I live in town, so there's no way I can do wind -- but my roof is perfect for solar. For me, one 5 panel 1kw system on my roof will take away almost 2 of my average monthly electric bills per year, and all for installed cost of round 6k. 1kW on a fixed mount gives 4.2 kWh a day, or 1533 kWh a year. At $0.12 per kWh, that's $184/year saved.
The choice of Wind or Solar is not a simple one. Compare systems closely and understand what's involved in maintaining both types for many years. If you want to know more about wind go here -- great info http://www.wind-works.org/ For wind data online go here http://www.windenergy.org/ For general information Indiana Renewable Energy Association is a great source.
Some great links on solar:
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700 E. Firmin St #212,Kokomo, IN, 46902765-480-4138
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Green Alternatives Inc
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