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Selecting a solar energy conversion method

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HarrisMarcus
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re: Selecting a solar energy conversion method
HarrisMarcus   7/9/2012 8:40:28 PM
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Additional information. Optimizers can be used for batteries as well as AC grid systems. STMicroelectronics has an evaluation board with P/N STEVAL-ISV005V1 that uses the SPV1020 and SEA05 constant voltage constant current controller to charge a 240W lead acid battery.

selinz
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re: Selecting a solar energy conversion method
selinz   7/9/2012 8:46:44 PM
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Interestingly, a solar panel sales guy came by on the day that this article was published. I was astonished to find out that I could actually save money immediately. It turns out that we use double the "average" user and for anything beyond the norm, the 15 cents/kwh goes to about 30cents/kwh. Thank you PGE. This makes getting enough panels to knock our electricity useage in half has a quick payback period. (7-8 years). If you are a do it yourselfer, it can be even less. see http://www.wholesalesolar.com/enphase-solar-power-system.html for example pricing. And no, I am in no way affiliated with these folks. They popped out of a simple google search. YMMV.

HarrisMarcus
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re: Selecting a solar energy conversion method
HarrisMarcus   7/9/2012 9:45:05 PM
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We are looking at the same thing. The article compared a microinverter delivering 115VAC, not necessarily Enphase which delivers a higher voltage, to a higher voltage, lower current DC system. The SPV1020 has performance monitoring features available through its SPI bus that include input voltage, input current and duty cycle. Output voltage can be computed from input voltage and duty cycle.

HarrisMarcus
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re: Selecting a solar energy conversion method
HarrisMarcus   7/9/2012 9:46:08 PM
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The power output of a solar panel changes a slight amount with time and this is specified in the panel manufacturerís data sheet. This case the power optimizer can be used to very good advantage because as the Vmp and Imp points change with time, the SPV1020 dynamically tracks these changes and enables the maximum power available to be extracted from the panel.

HarrisMarcus
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re: Selecting a solar energy conversion method
HarrisMarcus   7/9/2012 9:46:57 PM
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Yes you are correct. I should not be thinking only in terms of the northern hemisphere.

HarrisMarcus
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re: Selecting a solar energy conversion method
HarrisMarcus   7/9/2012 9:47:41 PM
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Using a power optimizer is not complicated and system design is straightforward. For a low voltage lighting application, the power optimizer will allow the maximum amount of power available to be extracted from the panel.

dave_dne
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re: Selecting a solar energy conversion method
dave_dne   7/10/2012 4:33:03 PM
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Page 5 of this article says "Comparison is made with a typical Enphase M215, 215W micro-inverter".

GREAT-Terry
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re: Selecting a solar energy conversion method
GREAT-Terry   7/11/2012 3:33:00 PM
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Very interesting MPPT control method. I like the micro-inverter idea as it is the most efficient way to dump energy to the grid. Managing multiple 200-300W power is much easier than a huge 10kW stuff. Great article!

HarrisMarcus
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re: Selecting a solar energy conversion method
HarrisMarcus   7/12/2012 5:35:44 PM
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Actually the microinverter method is less efficient than power optimizers and a large central inverter because 1) the voltage is higher and current lower which reduces I square R losses and 2) due to economies of scale there is less overhead and fewer number of components along with control circuits. The efficiency of the SPV1020 power optimizer is 98% and the efficiency of one large central inverter will be more than multiple microinverters.

HarrisMarcus
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re: Selecting a solar energy conversion method
HarrisMarcus   7/12/2012 5:37:19 PM
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RL will normally be much greater than Rs. Interposing the SPV1020 boost converter between the panel and RL decreases the load resistance seen by the panel. The load resistance seen by the panel Rin = RL x (1-du)^2 where du is the duty cycle internally set by SPV1020. The duty cycle is set by the SPV1020 so that RL x (1-du)^2 = Rs, the source resistance of the panel.

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