19 May 2014
By Jeff Frank
Medomak Family Camp in Washington, Maine was first founded in 1904, and purchased in 1994 by Holly and George Stone. With a focus on sustainability, the camp is now a much sought-after retreat for families, priding itself on memorable getaways and on leaving as small a carbon footprint as possible.
Set among 250 acres, Medomak provides a unique venue that’s rich in nature, where people converge together and operate for a time as a small community. The camp grows much of its own produce, and features a small dairy herd that supplies milk for the visitors. As an environmentally friendly retreat, it seemed only natural for the camp owners to look for innovative ways to incorporate renewable energy into their operations.
With little hesitation, ongoing measures have been taken over the years to take advantage of the sun’s rays. Measures have included installing solar hot water systems for the camp’s retreat center and for the cabins at the family camp areas. Photovoltaic (PV) systems have also been placed on top the roofs of the barn and other buildings, which have served to offset about 60% to 70% of the camp’s electricity requirements each year.
But that’s not all. Even some 17 years ago, George Stone decided to put in a well that was intended to provide fresh water to the camp, and that was powered by solar energy. Seems simple enough. But it was a project that proved more challenging than anticipated.
A solar-powered well
Utilizing the best technology available at the time, the well the Stones hoped would produce much of the water needed to meet the camp’s demands, was drilled to 110 feet. Unfortunately, after a month of operation, the project proved inefficient. The well and the solar pump equipment just weren’t up to the task or capable of producing the amount of water required at the camp.
To work properly and to offer enough water output, the well would need to be drilled much deeper. Determined to see the project through, the Stones did just that, ensuing the well was deepened to 350 feet. Although this depth allowed for sufficient water flow, the solar pumping equipment and the solar array supplying the electrical power were no longer adequate to drive the camp’s water system. To bring the system back online, electric lines had to be used to run a conventional AC-powered submersible well pump.
The PV pumping systems
Typical of early PV-powered pumping systems, the one used by the camp had limited capacity, and was never designed or intended to serve a pressurized system. Therefore, Medomak Camp had to rely on the water from an uphill holding tank, which was gravity-fed down to the camp below.
When solar pump systems were originally designed, most of the applications they served required very low system pressures. With a typical output of about one-half to five gallons per minute (GPM), these systems were only expected to supply a small amount of water per day. As a result, most common solar pump application became used for remote livestock watering. And, even though the power output from earlier generation solar panels was much lower than from today’s panels, the system price was significantly higher than today.
But times have changed. Now, as the cost of installing solar arrays approaches $1.00 per watt, it’s becoming much closer to parity with the cost of connecting to the utility grid. And, technology has improved. The increasing efficiency of solar arrays has provided an advantage to the pumping systems—meaning the PV panels of today are powerful enough, for the most part, to run with whatever pumping system is available to do the job.
Over time, technology has grown, and so has Camp Medomak. With it, the Stones wanted a permanent solution to their solar-powered well—one that finally promised a robust, off-the-grid result. But, this time, they decided to turn to a local pump expert for advice.
Pump expert Marc Stevens had seen information about a solar-powered controller, though he hadn’t personally implemented any solar pump systems in the past. Nevertheless, his research confirmed that a solar-powered controller could be made to work with the same four-inch submersible pump design that he commonly uses in AC-powered installations.
“I hadn’t installed solar [pumps] before because of the reputation of other products,” shared Stevens. “The flow was weak, so they could only go so deep.”
Camp Medomak proved differently. At the heart of the pump system that Stevens installed is a variable frequency drive (VFD) that runs the pump at varying speeds to maximize the system’s overall runtime, based on the instantaneous power available from the solar arrays. The benefit of doing so means this system often runs from sun-up to sundown with very few interruptions.
“With the VFD-based pump controller, I was pleasantly surprised that even though it was raining when we installed the system, we still had some voltage provided by the solar panels,” said Stevens.
The drive unit was wired in almost the same way as standard pumping system control panels, making the connections to solar power in and pump power out. Other features that were incorporated into Camp Medomak’s system was a connection to a 230-volt, single-phase, AC power input, which was added to serve as a backup power source for whenever the solar DC power proves insufficient to run the pump. The system has also been designed to protect itself from many common water system failure modes, ensuring reliable operation for years to come.
Because of the use of standard well pump equipment, the ability to run the system on pressure (having built-in protection and back-up power inputs), the pump system was easily able to serve the demands of Camp Medomak. And, since the pump was building enough pressure to meet the required demand, it became possible to eliminate the hilltop reservoir tank.
George and Holly Stone have just celebrated their 20th year at Camp Medomak. When asked how the new solar pumping system has operated since commissioning, George Stone replied: “It has been flawless…and it feels like I am making a difference because it aligns itself with our core philosophy of sustainability.”
Author Jeff Frank works for Franklin Electric.
Hatch Well Drillers