Solar tracker using Navy Sun data

[todster]

I also hated excel until I started this job. Everything here is M$ office. Once I accepted the fact I had to use excel, I quickly picked up on vba. Now I simply put VBA in a report, a button to click and send it back with a note telling them in the future they can now do their own reports  . I've reduced my workload tremendously. Now I have to make it look like I'm busy all the time.

 

[CAI_Support]

Ross,
 
Thanks for your suggestions. I will pass them to our developers.  What about the contest, do you have any rules to suggest and how much time would it take for people finish the project.
I am not sure what hardware most people use, but I imagine that can be a toy motor driving a desktop size model to run, or a real one actually turns real panels.  Ross already has the software running his trackers, he might also have some real hardware to recommend.
 
For people living in city without large space to install many solar panels, tracker will use least space to generate most power, especially with those 250W solar panel and Enphase M215 micro inverter. Very efficient and built-in MPPT function, can be DIY. However, for the contest, you don't have to even own one solar panel, just provide the PLC code. We then load into a WebControl to run motor proportionally to the proper coordination.
 
It will be nice the code is well documented, so that Ross could inspect it first, before smashing his tracker into wall or something else.

 

[rossw]

Ross,
 
Thanks for your suggestions. I will pass them to our developers.  What about the contest, do you have any rules to suggest and how much time would it take for people finish the project.
I am not sure what hardware most people use, but I imagine that can be a toy motor driving a desktop size model to run, or a real one actually turns real panels.  Ross already has the software running his trackers, he might also have some real hardware to recommend.
 
For people living in city without large space to install many solar panels, tracker will use least space to generate most power, especially with those 250W solar panel and Enphase M215 micro inverter. Very efficient and built-in MPPT function, can be DIY. However, for the contest, you don't have to even own one solar panel, just provide the PLC code. We then load into a WebControl to run motor proportionally to the proper coordination.
 
It will be nice the code is well documented, so that Ross could inspect it first, before smashing his tracker into wall or something else.

 
The only things I thought of were mentioned in my earlier post. Mostly stuff like what the code will require to operate, assumptions, connections etc.
 
I doubt anyone could realistically make a half-decent submission in less than several weeks. There are days of just thinking about how you're going to attack the problem. Then the inevitable half-way-done and change your mind. Even when finished, there's the whole "why isn't this working like I expected" testing. And most of us still have other real work to do in the meantime
 
The majority of trackers I've seen, worked with and built use ball-and-screw type linear actuators. Some use motor+gearbox+drive. One I've helped build uses a large, double-acting hydraulic ram to move an array that's 28 feet square!
 
All my own trackers are ones I've built myself from my own designs, but most use similar principles.

 

[todster]

Ross, have you ever tried using IR receivers placed at angles on the face to detect brightest light and use that to help as a fine or course for tuning?

 

[CAI_Support]

The most bright light may not produce the most power.  Smartest tracker will also need to consider output current and air temperature.  When sun is really hot, let panel reflect some the heat away may produce more electricity than absorbing all the heat.  In addition, to protect tracker against wind is also important, be able to automatically position panel flat during windy days is a big plus.  You can consider add wind sensor to WebControl frequency input or counter input, or analog input, depend on the wind sensor.  Getting weather data from weather.com is also a good way to predict against windy condition.

 

[rossw]

Ross, have you ever tried using IR receivers placed at angles on the face to detect brightest light and use that to help as a fine or course for tuning?

 

Tried it, rejected *ALL* the ones that simply chase the brightest spot.
Every one I've seen or tried has flaws and has failed to work under various real-world conditions.

 

[rossw]

The most bright light may not produce the most power.  Smartest tracker will also need to consider output current and air temperature.  When sun is really hot, let panel reflect some the heat away may produce more electricity than absorbing all the heat.  In addition, to protect tracker against wind is also important, be able to automatically position panel flat during windy days is a big plus.  You can consider add wind sensor to WebControl frequency input or counter input, or analog input, depend on the wind sensor.  Getting weather data from weather.com is also a good way to predict against windy condition.

 
My current WebControl-based tracker has high-wind inputs that park the array exactly as you say - in the "lowest wind-loading" position, for a period of time from the last gust. Once things calm down, it repositions to the correct place and resumes tracking. I've also added features like an input for "washing" the arrays, that puts them in a position for cleaning, and alarm that can sound briefly BEFORE the arrays move.

 

[CAI_Support]

My current WebControl-based tracker has high-wind inputs that park the array exactly as you say - in the "lowest wind-loading" position, for a period of time from the last gust. Once things calm down, it repositions to the correct place and resumes tracking. I've also added features like an input for "washing" the arrays, that puts them in a position for cleaning, and alarm that can sound briefly BEFORE the arrays move.

Yours is commercialized product.  I think with limited time, that is hard to achieve for people having day job.  What do you think about two months time frame?

 

[rossw]

Yours is commercialized product.  I think with limited time, that is hard to achieve for people having day job.  What do you think about two months time frame?

 
I made it purely for my own application, however several of my renewable-energy and off-grid friends in IRC requested similar setups.
Not sure that makes it a "commercial" product, but it may be of "commercial quality". Mine has had probably 10 hours of thinking, flowcharting, coding, debugging and subsequent tweeking... but spread over a month

 

[CAI_Support]

You are off grid, are you using super capacitor to store electricity or using regular wet batteries?

 

[rossw]

You are off grid, are you using super capacitor to store electricity or using regular wet batteries?

 
No supercap made to date will store the 10+ kWh I need overnight!
I use VRLA AGM cells, 2V/500AH per cell, 24 cells per bank, 3 banks.
 

 

[todster]

At 50 amp constant draw, under perfect conditions you get 30 hours?  With an overcast day and only a little wind, how long does it take to recharge the entire system? At only $0.04 per kw, I'm still a ways from going off grid.
Of course the way the US is trending, we might be forced to after we go bankrupt. I'd love to be the one that gets to tell a politician that we're laying him off permanently cuz things are little slow right now.

 

[rossw]

At 50 amp constant draw, under perfect conditions you get 30 hours?  With an overcast day and only a little wind, how long does it take to recharge the entire system? At only $0.04 per kw, I'm still a ways from going off grid.
Of course the way the US is trending, we might be forced to after we go bankrupt. I'd love to be the one that gets to tell a politician that we're laying him off permanently cuz things are little slow right now.

 
Peukert has some things to say about discharge rate and capacity. But in theory, yes, I could drag 50A for 30 hours, and it would then take about 15% longer to recharge them at the same rate.
 
In reality, discharging lead-acid batteries more than about 20% of their capacity severely reduces their life, so I wouldn't ever discharge them that deeply.

 

[CAI_Support]

HI Todster,
 
Depends on which part of US, in California, the electricity is close to $0.40 per kwh for tire 4.  Even tier 1 is way above your rate.  Are you sure you only pay 4 cents per kwH there?

 

[todster]

I've been paying it for 30 years so yes I'm sure about the rate. My town has it's own power company and purchases power under contract at a very low price. If the town miscalculates usage and we use less or more than we contracted for the period, there is an additional charge, but that is rarely more than an additional $0.04.
We have about 200 deep cycle batteries that are used in lifts with the largest weighing in at about 4500 pounds and 48 volts-1000 amp hour.  We have the lifts set to discharge down to 20% of capacity. The capacity is based on voltage. Our battery supplier claims this is the optimum for performance and longevity for the type of batteries we have. At only a 20% discharge, we would have lifts changing batteries every 20 minutes. We figure the productivity ($$$) offsets the shorter life span. The facility I'm at was built in 2006. All the batteries were new then. 90% of the originals are still in use although the capacity has diminished a lot. We are removing cells from 1 battery and using them to refurb others and then scrapping them once all the cells are no good. In theory I think I read somewhere, the higher the discharge rate, the lower the amp hours, exponentially. Not sure what the curve was for that.
Does your system need to equalize the cells on occasion?
I've been thinking of building a battery desulfator to try on a battery and see if it really does anything for it. Right now I'm trying to get the company to let me purchase a truck load of W/C boards and use them to control the warehouse lighting. I asked for $15K for the boards, triacs, wiring, etc. We'll see if they go for it. If they go for it, the savings in electric will offset the cost in no time.
Now all we need is solar panels to recharge the batteries. With a million square feet of roof we could generate a lot of power. I'm kind of interested in seeing where this contest goes. My capital expenditure request next year could be for solar cells.
 
The lower line is the adjusment penalty. Winters are tough and with the cost of fuel, a lot of people are using electric heaters which is not part of the prediction.