A "Side by Side Comparison" of the
Raum 3.5kw Turbine and Skystream 2.4kw Turbine
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Raum 3.5 kw rated at 24.4 mph** AWEA Standard Skystream 2.4 kw rated at 29mph** Not AWEA Standard
Down Wind Machine Down Wind Machine
5 Bladed 3 Bladed
Cut in Wind Speed 7.5mph Cut in Wind Speed 8mph
Blade Length 4 meter Blade Length 3.72 meter
Inverter Built to Install on Wall Out of the Sun *** Inverter Built into Turbine Head at top of Tower
3 Phase Wild A/C Permanent Magnet Brushless Generator with Bridge Rectifier 3 Phase Wild A/C Permanent Magnet Brushless Generator with Bridge Rectifier
Passive Yaw Control No Brushes **** Yaw Control with Brushes
Active Braking System Redundant Braking Relay
No Scheduled Maintenance No Scheduled Maintenance
5 Year Warranty 5 Year Warranty
Grid Tie or Battery Charging ***** Grid Tie with Battery Charging Capability
Remote Software Monitoring Ability Skyview Software for Remote Monitoring
Can Use longer runs of smaller wire due to 3 Phase delivery.

3 Phase has less Voltage drop. Why do you think the Power Company delivers
all the power by 3 phase until it gets right to the house? Then they use step
down transformers. They can use Smaller Runs of Wire to deliver more power
which means less money spent on wire conductors.  		 Longer Runs of wire must be sized larger due to 120/240 volt delivery from the turbine, because the inverter is built into the nacelle. This is proven by a voltage drop calculation on all wire runs. All electricians know this, and use those calculations to prove it.
   
** If Skystream Rated at the Same wind Speed of 24.4 mph as The Raum 3.5kw, the Skystream Rating would be closer to 2.1kw. Why buy a 2.1kw Turbine when you can buy a 3.5kw Wind Turbine at the same price point.

AWEA stands for American Wind Energy Association
(1.5.2.1 AWEA Rated Power: The wind turbine’s power output at 11 m/s (24.6 mph) per the power curve from IEC 61400-12-1, except as modified in Section II of this Standard.)

*** Larger Swept Area is able to generate more power than a smaller swept area (See its all about Rotor Size below)

**** Inverters are made of Electronic Components. Electronics are more efficient when they are in a climate controlled or cooler area out of the direct sunlight. Raums Inverter is made to be installed out of the sun unlike the Skystreams Inverter which is built into the turbine nacelle exposed to direct sunlight and harsh weather.

**** No Brushes to fail (eliminates additional parts that can fail)

***** Raum Battery Charger can be purchased instead of the Grid Tie Inverter if battery charging is required (No Extra Expense to have a grid Tie Inverter--- inverting power then having to convert back to dc voltage to charge batteries which is very inefficient.

Here is a typical application of the above voltage drop law.
˝ circuit length of 200’for 40amp single phase 120volt would be sized at #2
˝ circuit length of 200’ for 40amp single phase.240 volt would be sized at #4
˝ circuit length of 200’ for 40amp three phase 208 volt would be sized at #4
˝ circuit length of 200’ for 40amp three phase 277 volt would be sized at #6
#6 wire is smaller and less costly than #4 wire therefore more efficient.

Some people are confused it seems about wild 3 phase power and DC Power.

They are not the same and should not be compared in any way. This should dispel any myths about Wild 3 Phase not being efficient or that 120/240 volt is the best way to deliver power. If that were true the Power Company would not even have 3 Phase Power. Any Real Electrician can tell you that. If you have any questions about the best wind turbine for residential use, please feel free to call!

Below is a Chart of Wire Run Lengths and Sizes for both Raum and Skystream from their Installation Manuals.

Raum 3.5kw with 3 Phase Delivery
  
Skystream 2.1kw with 120/240 Delivery
Size
Meters
Feet
  
Size
Meters
Feet
#12
44
144
  
#12
37
121
#10
74
242
  
#10
58
190
#8
117
383
  
#8
92
301

 

Its All About the Rotor Size

In a wind energy system, the turbine rotor serves as the collecting device of the wind turbine. The rotor allows the wind generator to convert moving air masses into the rotating motion necessary to drive its electrical generator. Since most rotors operate at more or less the same efficiency, the only way to intercept more of the power in a given air mass is to increase the size of the wind generator’s collecting device — the rotor. This makes swept area, or even rotor diameter, a better tool for comparing different models of wind turbines than the generator’s rating.

The rotor’s swept area is the area of the circle delineated by the wind generator’s rotating blades. The equation for determining area of a circle is

 

Area = Pi x r2


The value of Pi is approximately 3.1416. The radius (r) is one half of the rotor diameter, or about the length of one blade in the rotor. It should be pointed out that since rotor area is a function of the square of the radius (or the length of one blade) small increases in blade length can result in rather large increases in swept area. In fact, doubling the rotor diameter yields a fourfold increase in swept area, with a corresponding increase in electrical generation.

Since most home-sized wind turbines are operating at about the same efficiency, rotor diameter or swept area rather than generator size makes a far better yardstick for comparing the various models offered by different manufacturers. While not a perfect measure by any means, comparing swept areas is far more accurate than relying on a wind turbine’s generator capacity. For example, it can be fairly safely assumed that a wind turbine with a swept area of 200 square feet will produce about twice as much electricity as a model sporting a rotor with a swept area of only 100 square feet.

 

Lesson #2

 

And it’s all about Tower Height

More Tower = More Power


The lesson we have learned from many wind turbine installations is that taller is better. The simple law of physics we follow is evident in one equation: P=1/2dAV3
P is power available
d is the density of the air
A is swept area of rotor (remember our first lesson? Its all about Rotor size)
V is the wind speed

We have no control over the air density, so the only variable is the V, wind speed.

So we can really rewrite the equation to look like this, P~V3. To put it simply an increase in wind speed from 8 miles per hour to 10 miles per hour (which is a 25 percent increase in wind speed) will result in a 100 percent increase in power. Do not allow anyone to confuse you with irrelevant facts. The simple law of physics cannot be changed, rewritten or remarketed in a slick package. Doubling the wind speed does not result in doubling of power available, but instead you get an 800 percent increase. That is why wind farm turbines are mounted atop such tall towers.

We try very hard to discourage our customers from trying to save money on a shorter tower. In the end its all about energy production and energy delivered. And that will only be achieved with a taller tower.

Event Horizon Solar takes this law of physics very seriously. That is why we offer a 60’ tower at the same price as our competitors system on a 45’ or 55’ tower. On top of that the Raum 3.5kw turbine is rated at a lower wind speed and has a larger rotor diameter than our closest competitor. Simply put, The Best Turbine at the Best Price for the Most Energy Delivered by the best Renewable Energy Company in the Midwest. Our goal is always more Electricity!
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