<?xml version="1.0" encoding="UTF-8"?><rss version="2.0" xmlns:content="http://purl.org/rss/1.0/modules/content/" xmlns:wfw="http://wellformedweb.org/CommentAPI/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:rssdatehelper="urn:rssdatehelper"><channel><title>Earthpower Blog</title><link>http://www.earthpower.co.za</link><pubDate></pubDate><generator>umbraco</generator><description>Earthpower Blog</description><language>en</language><item><title>Constant current drivers vs Constant voltage drivers</title><link>http://www.earthpower.co.za/blog/2011/9/28/constant-current-drivers-vs-constant-voltage-drivers.aspx</link><pubDate>Wed, 28 Sep 2011 09:36:27 GMT</pubDate><guid>http://www.earthpower.co.za/blog/2011/9/28/constant-current-drivers-vs-constant-voltage-drivers.aspx</guid><content:encoded><![CDATA[ 
<p>Electronic equipment has for many years been designed to be
driven by constant Direct Current voltage, most commonly
12vDC.&nbsp; Some companies prefer to drive their electronic LED's
by giving them a constant current (amps or milliamps) rather than
constant voltage.&nbsp; It is cheaper to manufacture than a
constant voltage driver and you get max light output from the
led..<br />
Their is a problem with this, particularly when switching on.&nbsp;
Often the electronics delivering the constant voltage do not switch
fast enough, so if the load (led's connected) is very little, then
initially the current output of the driver is too much for the LED
and it pops.&nbsp; In other words, the driver needs some time to
balance the output load to the draw being called by the leds in the
circut.&nbsp; This time to take to balance the load may be too long
for the diodes on the circuit.&nbsp; At the same time this device
will fully drive the led at all times, which in will cause it to
run hotter, emit more light, but shorten lifespan considerably.
With a constant current driver, the circuit should be switched off
frequently in order for the LED to cool down.&nbsp;</p>

<p>Then you have the risk when you switch on again.....&nbsp;</p>

<p>Small LED's run at lower than 12vDC voltages.&nbsp; They are
diodes, a diode is an electronic component that only allows
electrons to flow&nbsp;thru in one direction.&nbsp; Initially that
was their primary function, so they were an integral component in
any circuit filtering AC and delivering DC
electricity.&nbsp;&nbsp;Light emitting diodes were discovered by
accident when it was noticed that diodes glowed when they got hot
in a radio transmitter, back in 1907.</p>

<p>Basically what is happening is&nbsp;that a "toll" of a photon is
emitted when an electron goes thru the gate(diode)</p>

<p>So,&nbsp;I recommend rather that constant voltage be used to
drive LED's and then a simple resistor can be used to lower this
voltage to the LED's spec.&nbsp; This way you can actually drive
the LED at about 90% current which will cause it to loose only
about 5% of light output, but it will run much cooler and for a lot
longer.&nbsp; Constant voltage drivers, e.g. switch mode power
supplies, are much more tolerant of varying input voltages, which
is also important for protecting electronic equipment on an
unstable or varying grid supply which we often have in Africa.</p>
]]></content:encoded></item><item><title>Bargin Box</title><link>http://www.earthpower.co.za/blog/2010/10/7/bargin-box.aspx</link><pubDate>Thu, 07 Oct 2010 14:33:56 GMT</pubDate><guid>http://www.earthpower.co.za/blog/2010/10/7/bargin-box.aspx</guid><content:encoded><![CDATA[ 
<p>Earth Power's bargin box contains going out of stock items that
have been reduced to clear.</p>

<p>&nbsp;</p>

<p>Please browse over to our led section to see what is currently
in our bargin box section.</p>
]]></content:encoded></item><item><title>New 2kw and 3kw cast aluminum wind turbine (1)</title><link>http://www.earthpower.co.za/blog/2010/9/17/new-2kw-and-3kw-cast-aluminum-wind-turbine-(1).aspx</link><pubDate>Fri, 17 Sep 2010 12:46:48 GMT</pubDate><guid>http://www.earthpower.co.za/blog/2010/9/17/new-2kw-and-3kw-cast-aluminum-wind-turbine-(1).aspx</guid><content:encoded><![CDATA[ 
<h1><strong>New 2kw and 3kw cast aluminum wind
turbine</strong></h1>

<p><strong><img src="/media/4773/1_500x418.jpg"  width="500"  height="418" alt="1"/></strong></p>

<p><img src="/media/4786/2_499x545.jpg"  width="499"  height="545" alt="2"/></p>

<p><img src="/media/4791/3.png" width="464" height="685" alt="3"/></p>

<h3>The rear tail could autofurl&nbsp; to protect the wind
turbine</h3>

<h3>against high wind speed.</h3>

<p>During periods of high wind speeds the AutoFurl system will
automatically protect the wind turbine. When furled, the power
output of the turbine will be significantly reduced. In winds
between 15 m/s and 25 m/s it is normal for the turbine to
repeatedly furl, unfurl and then furl again. In winds above 25 m/s
the turbine should remain continuously furled.<br />
 AutoFurl is a simple and elegant method of providing high wind
speed protection. The AutoFurl system is based on aerodynamic
forces on the rotor, gravity, and the carefully engineered geometry
of the wind turbine. The aerodynamic forces acting on the blades
cause a thrust force pushing back on the rotor. This force
increases with increasing wind speeds.<br />
 The thrust force acts through the centerline of the rotor, which
is offset from the centerline of the tower pivot axis (yaw axis).
Therefore, the thrust force on the rotor is always trying to push
the rotor over to the side, away from the wind.<br />
 But the rotor is kept facing into the wind at speeds up to ~ 15
m/s by the wind turbine's tail assembly. The tail, in turn, is kept
straight by its own weight because its pivot at the back of the
nacelle is inclined. So the weight of the tail holds it against a
rubber bumper and the tail holds the rotor into the wind.<br />
 The AutoFurl system is completely passive, so it is very reliable
and since there are no wear points, like in a mechanical brake
system, it is very robust.</p>

<p><img src="/media/4796/4_497x370.jpg"  width="497"  height="370" alt="4"/></p>

<p><img src="/media/4801/5_497x295.jpg"  width="497"  height="295" alt="5"/></p>

<p><strong>NEW 2KW SPEC</strong></p>

<table border="0" cellspacing="0" cellpadding="0"
style="width: 531px;">
<tbody>
<tr>
<td width="229" valign="top">
<p>Rotor Diameter (m)</p>
</td>
<td width="271" valign="top">
<p>3.6</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Material and number of the blades</p>
</td>
<td width="271" valign="top">
<p>Reinforced fiber glass*3</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Rated power/maximum power</p>
</td>
<td width="271" valign="top">
<p>2000/2800w</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Rated wind speed (m/s)</p>
</td>
<td width="271" valign="top">
<p>10</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Startup wind speed (m/s)</p>
</td>
<td width="271" valign="top">
<p>2.5</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Working wind speed (m/s)</p>
</td>
<td width="271" valign="top">
<p>3~35</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Survived wind speed(m/s)</p>
</td>
<td width="271" valign="top">
<p>50</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Rated rotate speed(r/min)</p>
</td>
<td width="271" valign="top">
<p>380</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Working voltage</p>
</td>
<td width="271" valign="top">
<p>DC48V/350V</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Generator style</p>
</td>
<td width="271" valign="top">
<p>Three phase, permanent magnet</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Charging method</p>
</td>
<td width="271" valign="top">
<p>Constant voltage current saving</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Speed regulation method</p>
</td>
<td width="271" valign="top">
<p>Autofurl + electromagnetic brake</p>
</td>
</tr>

<tr>
<td width="224" valign="top">
<p>Weight</p>
</td>
<td width="275" valign="top">
<p>68kg</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Tower height (m)</p>
</td>
<td width="271" valign="top">
<p>9</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Suggested battery capacity</p>
</td>
<td width="271" valign="top">
<p>12V/200AH Deep cycle battery 8pcs</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Life time</p>
</td>
<td width="271" valign="top">
<p>15year</p>
</td>
</tr>
</tbody>
</table>

<p style="text-align: center"><strong>NEW 3KW SPEC</strong></p>

<table border="0" cellspacing="0" cellpadding="0"
style="width: 518px; height: 411px;">
<tbody>
<tr>
<td width="229" valign="top">
<p>Rotor Diameter (m)</p>
</td>
<td width="271" valign="top">
<p>4.0</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Material and number of the blades</p>
</td>
<td width="271" valign="top">
<p>Reinforced fiber glass*3</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Rated power/maximum power</p>
</td>
<td width="271" valign="top">
<p>3000/3800w</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Rated wind speed (m/s)</p>
</td>
<td width="271" valign="top">
<p>12</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Startup wind speed (m/s)</p>
</td>
<td width="271" valign="top">
<p>2.5</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Working wind speed (m/s)</p>
</td>
<td width="271" valign="top">
<p>3~35</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Survived wind speed(m/s)</p>
</td>
<td width="271" valign="top">
<p>50</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Rated rotate speed(r/min)</p>
</td>
<td width="271" valign="top">
<p>350</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Working voltage</p>
</td>
<td width="271" valign="top">
<p>DC48V/350V</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Generator style</p>
</td>
<td width="271" valign="top">
<p>Three phase, permanent magnet</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Charging method</p>
</td>
<td width="271" valign="top">
<p>Constant voltage current saving</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Speed regulation method</p>
</td>
<td width="271" valign="top">
<p>Autofurl + electromagnetic brake</p>
</td>
</tr>

<tr>
<td width="224" valign="top">
<p>Weight</p>
</td>
<td width="275" valign="top">
<p>85kg</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Tower height (m)</p>
</td>
<td width="271" valign="top">
<p>12</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Suggested battery capacity</p>
</td>
<td width="271" valign="top">
<p>12V/200AH Deep cycle battery 12pcs</p>
</td>
</tr>

<tr>
<td width="229" valign="top">
<p>Life time</p>
</td>
<td width="271" valign="top">
<p>15years</p>
</td>
</tr>
</tbody>
</table>
]]></content:encoded></item></channel></rss>

