Solar Energy Conversion Methods

by Adeel Ali

Links for Reference
This website contains information on investigating the most efficient and cost-effective methods for converting solar energy into energy directly consumable by house appliances. Below are some links and summaries of what I found most useful in my research.

The Physics of Solar Panels (An Introduction)

Research on Enphase M215 microinverters
àThe publication talks about the thermal performance of Enphase M215, telling us inductor is the biggest heat source for microinverter, CEC efficiency is ~96%, and to increase lifespan of microinverters we need to improve power handling capacity of solar module and microinverter.
Key Quotes:
“Our work strongly suggests that the lifetime of microinverter can be enhanced by matching power handling capability of PV module and microinverter to avoid the power saturation state of microinverter.”
“The typical DC to AC power conversion efficiency of microinverter is approximately 96% [23], and the remaining 4% lost energy is converted into heat among the components.”
“Typically inductors are the hottest component in an inverter [16].”
Comparing Enphase M215 to M250
àA direct comparison between M215 and M250. M215 seems to be better for handling modules producing less than 250W of power, while M250 is better for handling power greater than 270W. If power is in between 250 and 270W, it is up to the user though M250 seems to be better.
Key Quotes:
“For higher power 60-cell modules, the M250 is the logical choice. For lower rated modules, select the M215. However, for modules with STC output ratings between 250W and 270W, there are several factors to weigh when deciding which microinverter to select for the application.”
An Opposition to consider about Enphase M250
àAnapode claims M250 will not work for solar panels with 72 cells producing 280-305 W and that the M250 only works for rarer 60 cell panels producing 280-305 W.
Key Quotes:
“While there are a lot of new 280-305w panels out there they don’t work with it because Enphase designed the M250 for the voltages produced by a 60 cell panel. All the existing 280-305 panels use 72 cells to generate that many watts and they will not work with the M250. Enphase expected cell efficiencies to improve by the time this product came to market, they have not.”
A possible solution to convert 400 W from module
àENECSYS SMI-240-72 is a microinverter intended to deal with up to 400 W of power from 72 cell solar panels. It’s 95% efficient. It is a new technology and possibly unreliable though.
Power Point on Micro Inverters
By Francine V. Notte. NABCEP Certified PV Installer. ISPQ Certified PV Instructor
Key Quotes:
“Micro-inverters are installed on the roof under or next to a module and usually serve one single module at a time. Some serve two modules but the double ones have not been as successful as the micro-inverters attached to a single module.”
A New Solution for DC to AC Conversion: Power Optimizers
àSolarEdge is a big-name, trustworthy company that manufactures power optimizers that are able to convert solar energy to maximized DC energy. It has a model P405 that can handle module power that is greater than or equal to 405 W, just enough for the solar panels we are using. It has a weighted efficiency of 98.8%!!!
Key Quotes:
Superior efficiency (99.5% peak efficiency, up to 98.8% weighted efficiency) “

Power Optimizer P Model Module Power Module Voc Current
P405 ≤405W < 125V 10.1A

A challenge of Power Optimizers
Key Quotes:
“When the SolarEdge power optimizers are not connected to an operating SolarEdge inverter, they each limit their output level to a safe voltage of 1V.”

Solar Battery Chargers
These solar battery chargers were sent to the students travelling to Uganda to help them charge the batteries in smoke detectors. They are capable of charging 3, 6, 9, or 12 V batteries as needed. 9 V were applicable in this case.



Solar Panel Specifications
–> This site was used to reference the specifications of the solar panels we are currently using. An off-grid inverter would be chosen accordingly.

Off-Grid Inverter Candidates
Below are inverters only available for companies. Perhaps the prices can be negotiated, however.

PBSP 740 Series

ME4520 Inverter

NGL Series

Below are inverters that are approved and compatible to SunPower E20 435 Watt panels

Fronius Inverters
–> This one is commercially available

Powerone Inverters

SMA Inverters

Adeel Ali is a junior Physics major at Cal Poly San Luis Obispo who aspires to pursue a life of an academic. In the future, he sees himself as a Physics professor teaching undergraduate students at an accredited university.