Battery-less, off-grid set-up?

[ragnarviking]

Please forgive a total newbie if I ask ask a question that has been answered in another post. I will be joining with others to provide chicken houses to third-world villages, primarily in tropical and subtropical regions. Our building design requires the use of a centrifugal type exhaust fan. I have found 12 vdc/17 amp (450 cfm) and 48 vdc/4 amp (400 cfm) examples for sale. My question is: Can the battery be left out of the loop? Are controllers available that can flip on when the voltage is sufficient and turn off when voltage is too low? Intermittent power is OK. Off at night is OK. It appears to me that removing the battery from the system solves the primary maintenance issue. Maintenance is key when most villages have no one with the necessary skills. I welcome any suggestion that would aid us with our design and our goal to provide 400 to 500 cfm of air movement when the sun shines.

[inetdog]

Please forgive a total newbie if I ask ask a question that has been answered in another post. I will be joining with others to provide chicken houses to third-world villages, primarily in tropical and subtropical regions. Our building design requires the use of a centrifugal type exhaust fan. I have found 12 vdc/17 amp (450 cfm) and 48 vdc/4 amp (400 cfm) examples for sale. My question is: Can the battery be left out of the loop? Are controllers available that can flip on when the voltage is sufficient and turn off when voltage is too low? Intermittent power is OK. Off at night is OK. It appears to me that removing the battery from the system solves the primary maintenance issue. Maintenance is key when most villages have no one with the necessary skills. I welcome any suggestion that would aid us with our design and our goal to provide 400 to 500 cfm of air movement when the sun shines.

The very best performance without a battery would be obtained from what is called a linear current booster. It allows the panel to run at its most efficient voltage while letting the motor voltage and current both vary with motor speed to match the total power available. The LCB is a pretty simple electronic package which should need no maintenance and a lifetime equivalent to that of a good charge controller, without the maintenance problems introduced by batteries.
LCBs are often used with solar pumps, but I do not see why they could not serve the same purpose with fans. The key is your willingness to accept varying output and no power at night or on cloudy days.

[SunEagle]

There are a number of different types of solar attic fans with DC motors that run directly off a solar panel. The package comes with one fan and usually one solar panel of a specific wattage. The panel wattage would depend on the CFM requirements for the fan.

The fan will speed up in bright sunlight or slow down to a stop in lower light so it will be variable during a day with clouds.

[Wy_White_Wolf]

Brushless permiment magnet motors work better than others when trying to run solar direct. Also try to find motors that can operate on a wide range of voltage. LCBs not only help with getting the motor running they also help the motors last.

Sizing your panels so the amperage is about 1.5 times what the motor requires seems to work about best. That allows for about 6 hours a day that the panels will put out enough to run the motors. If you need longer then having 2 arrays (1 pointing east and 1 pointing west of that size seems to work best.

WWW

[ragnarviking]

Thanks for all the replies. I'll study up on LCBs. thanks again.