Solar Heating Pools in the NW High Desert

Solar heating a swimming pool in the high deserts of Oregon, Washington, & Idaho is a unique situation.  This region certainly offers a plentiful solar resource and so choosing the sun as a heat source is certainly worthwhile.  However, along with frequent warm, sunny days come very cool, often freezing, nights.  This is especially the case during the late spring and early fall months into which the pool owner would like to extend their swimming season.   It is important to understand and properly address these climatic conditions in order to maximize the solar heating potential and durability of any solar system used.

Above Ground Pools (AGPs)

AGPs are a more prone to issues related to the above situation than are in-ground pools for several reasons:

• Simply stated, AGPs are above ground and thus subject to more convection cooling from wind as well as the cooler ambient air temperatures at night due to their lower volume vs. surface exposure ratio.  What you can do:

  • Metal-sided AG pools can be pre-insulated when first installed or whenever the liner needs replacing which helps somewhat

  • Soft-sided AG pools cannot affectively be insulated

  • Block consistent winds with vegetation or a fence

• The 2x20 or 4x20’ solar panels specifically designed for AGPs might not be the best choice in this region.  Why?

  • Due to their 20’ length, these panels are usually mounted with the tubes running horizontal

  • They may not thoroughly drain and could freeze splitting the tubes

  • Freeze damage is NOT covered by any factory warranty

  • Should not be permanently mounted

    • Must be removed in the fall and reinstalled every spring

  • Do NOT qualify for OR solar tax credits

  • Multiple panel systems (>2) difficult to properly plumb together

• It is recommended to use panels that can drain (see IGP systems below)

 In-ground Pools (IGPs)

• Standard 4x8, 4x10, and 4x12’ IGP panels are available to mount onto a roof or rack so the panels will drain. 

  • Panel tubes follow slope of roof or rack (minimum 6^o slope required to drain)

  • Panels can be permanently mounted

  • Panels qualify for OR solar tax credits

  •  More expensive initially but similar in cost to AGP panels when OR tax credits taken into account (50% up to $1500)

  •  Longer 12-year FULL warranty (parts & labor)

  • Multiple panel system OK.  (parallel flow by design)

  • Designed for larger pool applications

Both AGPs and IGPs

• Solar panel surface area should be 50-60% of pool surface area to maximize solar gain potential and extend season as much as possible

  • Smaller systems OK when only heating from Memorial Day to Labor Day

  • 40% minimum required for OR solar tax credit

    • Plus blanket must be used 12 hours minimum

• Of course, use a pool blanket, liquid cover, or both to minimize evaporation and surface convection cooling. 

  • Definitely use at night

  • Best to use whenever pool is not in use

•  If possible, don’t circulate the pool at night

  •  Circulation increases heat loss through the pipes, pool equipment, off the pool’s surface, and out the sides of the pool on AGPs.

•  Panels and solar loop piping should be drained at night to avoid potential freeze damage not covered under warranty.

  • Either manually or automatically

    • Pump must be OFF to drain automatically

    • Put timer on pump or manually shut-off

    • If pump runs at night, solar loop must be isolated and drained manually whenever freezing is possible

  • If solar loop piping goes over roof to panels, they must either:

    • Be drained manually with a ½” drain line at lowest panel header

    • A ½ “ line from lowest panel header can be ran back to the solar feed line at the pool equipment

•  Recommend using a solar control to maximize solar efficiency

  • Solar panels can cool a pool if operated whenever ambient temperatures lower than pool or when sun is unavailable

  • Sensors monitor pool and solar temperatures

  • Offer high limit protection so pool won’t overheat