@ Khalid U R awesome dude. 
I think "We got work to do" Hopefully some others agree on that.
BTW I failed to answer one of the questions. He asked why a wind turbine requires mppt while a solar panel doesn't. The answer is this. If a wind turbine is trying to charge a battery, the turbine will be spinning at different speeds. Both dc and ac motors produce different voltages at different speeds. The higher the speed, the higher the voltage. OK, so as long as the output voltage of a turbine is below the battery voltage, there is no charging because the battery is pushing harder at the electrons than the wind turbine. In fact, the system will most likely require some kind of diode to prevent the battery from dumping current into the wind turbine. .. Not what we had in mind... OK, so the rpm rises, the voltage rises the voltage reaches battery voltage and a tiny bit of current starts to flow. The voltage rises to around 2 volts more and a ton of current starts to flow. (btw I was keeping track of the wind turbine generation faq on alt.energy.renewable around 1995) .. So a ton of current starts to flow and it acts as a barrier to the increase of the wind turbines speed because the wind turbine can't produce the energy demanded by the current flow. So it slows down (or refuses to speed up). Well, when the turbine is spinning slowly, the force on the blades may rise a little, allowing for more current, but the energy output of the turbine will be proportional to force (torque) multiplied by angular speed. So, now that the turbine is blocked at a particular rpm from spinning faster, it can't collect the energy that is available because the speed can't rise. The solution to this problem is mppt. The mppt algorithm watches the current flow/voltage in tandem and scans the current/voltage dimension for the combination which produces the most power. When that optimum in power is produced at a voltage (respective turbine speed) above the battery voltage, the algorithm buck-converts the higher voltage down to battery voltage with higher current and presto ..... more power
Now, let's talk about the solar panel. The solar panel is basically an arrangement of P-N junctions. They convert light into current. Basically, a 2 electron volt photon is incident onto the panel and it jumps an electron over a two volt junction gap producing 2 electron volts of available power. If more 2 ev photons are incident on the panel, then more electrons jump the 2 ev junction gap, but they are still only at 2 volts potential because that is all the energy available in the 2 ev photons. We arrange a bunch of these in series, to raise the voltage up to something that can match our batteries. Now, what happens when more sunshine hits the panel is that because of quantum mechanics above, the voltage output from the panel doesn't really change (not much anyways). In stead, the panel becomes capable of sourcing more current.
Now, not all photons are red 2-ev photons, so this makes the dynamic a little more complex. If we raise the voltage required to charge the battery, what happens is that the 2 ev photons are close to being the weakest of the bunch. There are also infrared photons, but the panels will not be designed to receive them because receiving them means shrinking the junction gap voltage and hence the cell voltage, and hence the cell power. ok, if we raise the voltage demanded of the panel, The red 2 ev photons will discover that the voltage on the junction has risen above 2 volts and they can no longer push the electron over the gap, so we lose current. However, there are higher voltage photons in the mix. Visible light contains half the energy of sunlight, and the panels are tuned to be most receptive to particular photon energies. So, what happens as we demand more voltage from the panel is that the higher energy photons can still jump the gap. Visible light is a concoction of photons between 2 and 4 electron volts. The cells are probably not particularly sensitive to 4 ev photons (blue) because they just can't engineer the silicon to be optimally receptive to all photon energies. Next, keep in mind, that if a 4 ev photon is incident on the panel, it can jump only one electron over the gap which is operating at around 2 ev. This means that the extra 2 ev in the photon are wasted.
So the designers of the panel are caught in a conundrum of shrinking the gap and receiving the IR photons, but wasting the extra energy of the higher energy photons and the alternative of raising the gap energy to receive the full power of the higher energy photons, but excluding the use of the lower energy photons. So you can see why pvs have efficiency problems. Recent attempts to produce panels that can split the energy of a single high energy photon into two and jump two electrons across the gap have been successful. However, these cells/panels are not ready for production and may never be.
So the way this boils down is that panels produce only slightly more current if short circuited (like maybe 25% more) then at voltage ranges from small up to their designated maximum power point, their output current is nearly constant and it begins to drop off as we demand more voltage from the panel than it can produce. So there is this sweet spot of about +- 6% of the panels output voltage where it produces very close to its maximum power. If we demand voltage below that, then we waste voltage. If we demand higher voltage, then the panels current sharply drops off. It's better to demand lower voltage than higher voltage because if you raise the voltage required of the panel as much as even 15% above its maximum power point, you will discover that it outputs very little power. Most of the photons incident on the panel will be unable to make electrons jump the gap.
Once again, the photon energies in sunlight are pretty much the same no matter how much light you are getting, so the panels output voltage pretty much stays the same. It just becomes more current-capable.
So, if we charge a 24 volt battery with a 30-31 volt panel in a relay configuration, the panel and the battery are closely matched. MPPT is useless because there is no spare voltage to dc-convert down, and PWM is bad because the pwm transistors will absorb the last volt or so, causing a mismatch between the panel and the battery. So, if we use a 35-37 volt panel in stead, then MPPT is slightly useful (get us maybe 5-7% advantage). PWM is perfect for the 35 volt panel, but becomes wasteful for the 37 volt panel. So, the next thing we do is we say ... we hate line losses and purchasing a lot of copper, so we raise the panel voltage up a lot higher by putting them in series. Then, MPPT really shines because it transforms the extra voltage into extra current. Basically, MPPT controllers can be considered to be dc-dc converters. PWM and Relays do not do this. So the answer is ... if you are running power a long distance (say a couple hundred feet) then you want an mppt controller, and the more distance you run, the more voltage you want the mppt controller to accept. Midnite solars highest voltage mppt controller accepts 250 volts and dc-dc converts it down to battery voltage. Now, when matching panels to the mppt controller, you have to consider the panels open circuit voltage which will be some 10-20% higher than its maximum power voltage. Failing to do this could cause a failure when the controller turns the current flow off and the panel output voltage rises to its peak. We will basically risk crashing through the dc-dc converter transistors. So, what this means is that for the 250 volt controller, you want to run a maximum power voltage of around 180-190 volts.. so you choose your panels to do this.
BTW, crashing through the mppt converter transistors is a high risk for wind power because the voltage output is so drastically variable. So, if you are using wind and MPPT, then you are wise to include a voltage clipping stage that will cut the voltage down to MPPT maximum if it goes higher.