Apollo solar, electric models pump through Iowa winter: More methane, lower risks


The engineers initiated the test during December 2011. Linear-rod reciprocating-piston drive motors were identical, but each utilized a different power source: Direct electric power converting 220-volt AC to 24-volt DC in well GW-01, direct power from 12-volt DC batteries charged through a mounted solar panel in GW-02, and power from a solar panel alone in GW-05.

The pumping flow rates were a maximum of 2.25 gallons (8.5 liters) per minute. Pump intakes were set 1 to 3 feet above well bottom to avoid accumulated silt or debris. GW-02 began operating on Dec. 13, 2011, followed by the other two wells on Dec. 21.

Liquid levels were measured periodically through March 2012, and pressure transducers were installed March 6. The transducers recorded liquid elevations every 15 minutes. Percentages of methane and oxygen were measured periodically before and during pump operations.


Average 24-hour groundwater levels were satisfactorily reduced and consistently maintained at pump intake by all three power options, including the solar-only system. Depending upon the well, between 15.6 and 18.4 feet of additional screen was exposed -- between 75% and 93.6% -- equating to methane-flow increases of at least 15% at GW-01 and GW-02 and approximately 20% at GW-05.

Solar-only power at GW-05 produced minor fluctuating liquid levels corresponding with the on/off cycle during daylight/nighttime hours. Approximately 3 to 4 feet of liquid accumulated while the pump was not running. The pump switched on during daylight hours, removing the liquid and maintaining liquid level at intake. The degree of daily fluctuation in GW-05 was relatively minor compared with length of additional screen exposed (17.0 feet).

Operation of all pumps was consistent day to day and demonstrated positive correlation between additional screen exposed and increased methane flow.

Results confirmed that reducing and maintaining low liquid levels using low-flow pumps is feasible and that increased gas flows are obtained through exposure of additional screen. Results also indicated that all three power supplies, including cost-efficient solar alone, are capable of dewatering gas wells and freeing significant length of additional screen.

Pump Specifications

Apollo model 101 at ¼ horsepower

4-inch diameter well casings

Slip coupling and PVC well seal

¾-inch HDPE tubing

Optional solar panel and 12-volt DC solar batteries

Site specifics

30-acre landfill cell

Leachate and landfill methane impacting surrounding groundwater

Test dates: December 2011 – April 2012