# Mike Dodd's posts

#### Posted by Mike Dodd on Oct 8, 2012 09:27 pm

#1 -
Okay, PV panels are really inefficient -- around 15%. With 1 KW of solar energy falling on every square meter of the earth's surface at noon, I can expect up to 150 watts of electrical power from a typical PV panel.

What can I expect from a typical water heater panel?

Each hour, that 1 KW of solar energy is equivalent to 3,412 BTU, so a 30 sq.ft. (2.79 sq. meters) water panel will receive 2.79 KW or 9,519 BTU per hour.

How much of this heat is transferred to the water?

Asked another way, if water at 60F enters a 30 sq.ft. panel in full sun, what will be its temperature when it exits?

Thanks for any definitive information.,

--- Mike

#### Posted by Mike Dodd on Aug 31, 2012 12:50 pm

#2 -
I'm installing 14 290W Suntech PV panels 200' from the equipment room. The panels will be wired as seven series-pairs, and all seven pairs will connect to a common point inside a Midnight combiner box.

Due to the distance, I'm using individual #2 type XLP-UF aluminum wires from the PV array to the Outback load center in the house.

Sadly, due to the fact that the wire is aluminum, the power loss through the #2 wires will be 10% -- too high for me.

So I want to use TWO #2 wires in parallel for each feeder (two for positive and two for negative), to cut the resistance and the power loss in half.

Can someone tell me if the code allows this? When I asked Outback tech support, I was told that I can't use parallel wires (and that I need a combiner box, which told me he probably was confused).

All I want to do is to connect TWO wires to the combiner box's positive TBB and TWO wires to the negative TBB, then connect the other ends each pair to the same positive and negative TBBs inside the load center in the house. According to the aluminum wire table, this gives me the same resistance as 2/0 wire.

NOTE: The aluminum ampacity table shows that ONE #2 wire is large enough for the 53 amps of current my PV array can produce, so I'm not trying to parallel the wires to handle more current -- only to reduce power loss in the cables.

Thanks in advance for any definitive information.

#### Posted by Mike Dodd on Aug 31, 2012 12:24 pm

#3 -
Hello from a new solar power convert.

I originally posted this in the general-discussion forum, but then discovered that the most recent posting there was in 2007! So I decided to also post here, where activity seems to be a bit more lively.

My wife, Louise, and I are in the process of installing 4KW of PV panels and an 8KW Outback Radian inverter for backup and emergency use. We're not planning to go off-grid at this time.

During the planning phase, I wrote a little program to calculate and display hourly sun position and PV production. This program proved to be very helpful, so I'm making it freely available to all. The Sun Angle Calculator (SAC) has these features:

* User-specified latitude, local horizon, and PV characteristics (number of panels, watts per panel, azimuth, tilt).

* Graphs hourly sun positions and PV power relative to a local horizon on a specified month and day.

* Calculates hourly sun position and PV power relative to the local horizon on a specified day over 12 months, and produces a detailed report.

* Reduces available PV power by a user-specified factor when the sun is shining through leafless trees or is obscured completely by leaves.

* Calculates the optimum PV azimuth and tilt for one month or an average for all 12 months.

* Northern hemisphere only.

You can learn more about SAC, see a screen shot, read the 16-page PDF user manual, and download the ZIP file on our family website <http://house.mdodd.com/update_solar.html#SAC>. The program is free for all to use.

I hope folks find this software useful. Comments are welcome.

#### Posted by Mike Dodd on Aug 27, 2012 11:36 am

#4 -
Hello from a new solar power convert. My wife, Louise, and I are in the process of installing 4KW of PV panels and an 8KW Outback Radian inverter for backup and emergency use. We're not planning to go off-grid at this time.

During the planning phase, I wrote a little program to calculate and display hourly sun position and PV production. This program proved to be very helpful, so I'm making it freely available to all. The Sun Angle Calculator (SAC) has these features:

* User-specified latitude, local horizon, and PV characteristics (number of panels, watts per panel, azimuth, tilt).

* Graphs hourly sun position relative to a local horizon on a specified month and day.

* Calculates hourly sun position and PV output power position relative to the local horizon on a specified day over 12 months, and produces a detailed report.

* Derates available PV power when the sun is shining through leafless trees or is obscured completely by leaves.

* Calculates the optimum PV azimuth and tilt for one month or for all 12 months.

* Northern hemisphere only.

You can learn more about SAC, see a screen shot, read the 16-page PDF user manual, and download the ZIP file on our family website <http://house.mdodd.com/update_solar.html#SAC>. The program is free for all to use.

I hope folks find this software useful. Comments are welcome.

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