Welcome to my Adventures

The pupose of this Blog is to keep in contact with many good
friends spread out all over the world.

Saturday, January 5, 2013

Medical Rescue Stint

Mark send me this photo last week. Whenever he is back in the country he is assigned to fly Rescue
Choppers. Usually at the South Coast. This photo was taken as he was taking off to sling a body
out of a river gorge in Natal. Somebody found a body floating in the river and as the location was
extremely inaccessible by foot the chopper was sent in to do the job.
He says it was a tricky bit of flying having to balance the skids on a few rocks in the river so
the medics could load him into the stretcher and then do a vertical climb.

6.3kW on a cool overcast day. 76 Amps says we are in charge limit as well

80% cloud cover

Photo Voltaic Panel Performance

One of the less well known facts about Solar Panels is that their ability to convert sunlight into electricity depends heavily on their temperature, which is to a first approximation the ambient temperature,
in other words is it a cold or hot day. There are other factors as well influencing how hot they get
such as how much cooling is available. Cooling can be just simply wind flowing across them.
Correct mounting is also important, for instance having a gap of about 3 to 4 inches (7 to10 cm)
underneath so no hot air is being trapped below the panels.
But of course they operate best on a cool day. Even if there is a substantial cloud cover.
Such a day is today. Happened to walk past the inverter and looked at the display.
Showed 6300 Watts. The duty cycle  of the MPPT was at 63% which is an indication of the
prevailing weather condition.
It shows 76A being produced. That means we are in Charge Limit, the MPPT can't handle more
and limits the current before it would self-destruct.
Took some photos of the display and the cloud cover.
80% overcast I would say. Ambient temperature about 22 degree Celsius. A cool day for us
in Johannesburg.
By comparison, yesterday we had the most exquisite day in a long time. Deep blue sky, not a cloud
in sight all day, hot as well. 30 degrees at least. The panels never managed to go much over 5000 Watts.
I've seen this many times before. If you look at the performance curves of a solar panel it is very apparent.
Solar Panels are after all nothing more than Silicon Diodes optimised for light to electricity conversion.
And all diodes exhibit a negative temperature coefficient of about 2.2mV/deg. That means the power they
produce for a given solar radiation (called Insolation for Incident Solar Radiation) is less the hotter
they are.

Vorna Valley Johannesburg

Vorna Valley Johannesburg
I live right in the middle of the picture

My Life Philosophy

My Life Philosophy