Pump­ing wa­ter for free

Home - Santa Fe Real Estate Guide - - WATERENERGYNEXUS - DOUG PUSHARD

Pump­ing wa­ter up­hill can be “al­most free” when you use pho­to­voltaic (PV) pan­els and a DC pump. This can be a great con­ve­nience if you hap­pen to live on a hilly lot where it might be cost-pro­hib­i­tive to run elec­tric­ity to a tank, or you re­ally want to re­duce your re­liance on the grid. Let grav­ity do the work.

DC pumps are a lit­tle more ex­pen­sive than the stan­dard AC, but they can run di­rectly off your PV ar­ray so re­quire no grid-tied elec­tric­ity. With the dra­matic de­crease in the cost of pho­to­voltaic pan­els, the in­creased in­ter­est in re­duc­ing one’s car­bon foot­print, and/or the de­sire to be­come more self-suf­fi­cient, these sys­tems are now be­ing in­stalled in ar­eas where the power grid is read­ily avail­able.

I re­cently worked on this type of sys­tem in the foothills south of Santa Fe. The client has a rain­wa­ter stor­age tank next to the house at the bot­tom of a slop­ing lot. The gar­den is about 200 feet away and up about 25 feet in el­e­va­tion. It would have been very costly to trench an elec­tri­cal line. The cost of run­ning the pump ev­ery day to getwater to the gar­den seemed coun­ter­pro­duc­tive to the goal of in­creas­ing sus­tain­abil­ity with a large gar­den.

The sim­ple so­lu­tion was to in­stall a DC pump with the rain­wa­ter tank next to the house con­nected di­rectly to a prop­erly sized so­lar panel as a power source. An ad­di­tional tank was in­stalled slightly up­hill of the gar­den. On ev­ery sunny day, wa­ter is pumped up to this tank to keep it full, and it pro­vides wa­ter to the gar­den via grav­ity. A float in the up­per tank sig­nals the DC pump when to pump wa­ter and when to stop.

Ace­quia Madre Ele­men­tary School has a DC-based rain­wa­ter sys­tem equipped with a bat­tery. In this case, the PV panel keeps the bat­tery fully charged so that on cloudy days, wa­ter is fully ac­ces­si­ble.

The tech­nol­ogy to do this has been around for decades, but what has changed is the price. Both PV pan­els andDC pumps have dropped dra­mat­i­cally in price. Ad­di­tion­ally, to­day there are many more sizes of pumps and pan­els, so match­ing up these two com­po­nents is­much eas­ier. The com­po­nents must match! Not just any PV pan­el­will power any DC pump. Al­most all 120-volt AC pumps can use a stan­dard wall out­let. The out­put pro­vided by a pho­to­voltaic panel must match the power re­quire­ments of the DC pump.

Now for a one-time fee of a fe­whun­dred dol­lars for a sin­gle, small PV panel and a DC pump, you can pump wa­ter with­out hav­ing to pay an elec­tric bill. This same setup would have been thou­sands of dol­lars not too long ago. In an area with lots of sun, this is a per­fect low-cost, longtermso­lu­tion. It’s an ex­am­ple of newer tech­nolo­gies and lower prices en­abling so­lu­tions not fea­si­ble just a short while ago: a small change that can pro­vide years ofwa­ter de­liv­ery for free.

Doug Pushard, founder of the web­site www.Har­vestH2o.com, has de­signed and in­stalled residential rain­wa­ter sys­tems for over a decade. He is a mem­ber of the Santa FeWater Con­ser­va­tion Com­mit­tee, a life­time mem­ber of the Amer­i­can Rain­wa­ter Catch­ment Sys­tems As­so­ci­a­tion, and an EPAWaterSense Part­ner. He can be reached at doug@Har­vestH2o.com.

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