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Solar panels arrive!

5/14/2015

5 Comments

 
Thanks to my sponsor, Renogy #renogysolar, I am now the proud owner of 4 of their 100-watt bendable panels!  The boat is pretty much built around these panels, so they had better work.  A few days ago I took one of them and put it up on the roof of our house facing straight up.  It gets a clear view of the sun except for a few hours in the morning and evening when shade from trees hits is.

I wired the panel to a bank of power resistors with a combined resistance of about 3.1 ohms and started logging data using my PowerLog 6S (a super-useful tool)  Fortunately, the weather has ranged from mostly sunny three days ago to mostly cloudy with thunderstorms today, excellent for testing the panel in a variety of conditions.  Here's a graph of voltage, current, and power from the mostly sunny day.  The panel doesn't quite reach the 100 watt rating, but keep in mind that the sun is not directly overhead even at noon, and I'm not operating the panel at its max power point (17.7 volts).
Picture
The graph below shows the energy (integral of power over time) collected over the course of the daylight hours for three days.  May 12 was mostly sunny, May 13 a little cloudier, and May 14 was a rare, stormy day here in drought-stricken California.
Picture
I'm really quite happy to see so much energy coming from theis panels.  I've been counting on basically getting a 24-hour average of 10 watts of useable power, or in other words 240 watt-hours per day from each 100-watt panel.  This is after taking into account all the various losses in the batteries, voltage regulation, etc. etc.  The data shown above didn't include these losses, but I think it's still safe to say that I'll get FAR more than 240 watt-hours per day per panel on an average, non-stormy day.

Of course I still have to worry about the panels getting sea scum on them, bird droppings, etc., or operating in the winter.  So I'm not about to propose using only one panel on the boat instead of two.  But it's comforting knowing that the panels really do pump out power as advertised.
5 Comments
Ryan link
6/12/2015 06:49:37 am

How is the control software going. Remind me will you get remote data back from they system? Will you trying to log data from your trip, or just run barebones control logic?

Anyway it's a super cool project.

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Ryan link
6/12/2015 06:52:55 am

Sorry it would appear English is a second language for me. Since it appears coding would be my first language let me correct that last post.

s/going./going?
s/trying/be trying

Thanks and good luck on your project.

Reply
Damon
6/24/2015 01:58:00 am

Hi Ryan,

Control software is plugging along but at this point hardware is definitely getting more attention. Yes, we'll get data back. How much and how often will depend on how much money we want to spend, but certainly we'll send health-related data (voltages, temps, etc.) several times a day. We'd like to log at least one item of scientific interest, such as water temperature, during the voyage.

Anyway, from one garage worker to another, thanks for your interest!

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sameer
4/18/2017 03:07:25 am

Over charging protection is required in this case. Since you had all this energy , why design for low speed ? Would you change design speed if you go back in time.

Reply
Damon
4/18/2017 10:05:05 am

Hi Sameer,
The battery has a protection circuit which prevents the cells from overcharging. Also, the solar panels stop producing current as the voltage gets up around 20 volts, so they inherently have overcharge protection built in.

Regarding speed, that's a good question. Maybe. Hard to say. There were definitely some times (early on) when I had more than enough energy. But there were also plenty of days when I didn't have enough. The main mistake was that I didn't have quite enough battery capacity. I should've added at least 20% more battery capacity. I had physical room for 100% more, but I was too cheap to buy the extra batteries!

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