SolarBee uses sunshine on the water to scrub
reservoirs clean
Running water is an energy source, but still
water can be an energy drain. As much as 3 percent of the country’s
energy consumption goes to treating water in reservoirs and
wastewater lagoons, according to Pump
Systems, Inc., manufacturers of a floating water circulator
that runs on renewable energy.
The photovoltaic-powered SolarBee
aerates closed water bodies, mixing warm, oxygen-rich water
from the pond’s surface with cooler, oxygen-depleted water
at the bottom. Currents do this same job in open watercourses
like rivers and springs, balancing the aquatic ecosystem. Without
aeration, nuisance plants and harmful
algae build up, killing fish in freshwater ponds, aggravating
environmental concerns in wastewater lagoons, and giving off
unpleasant odors.
Until recently, municipalities and industries
had only two options for aerating ponds and reservoirs: a never-ending
cycle of chemical treatments or mechanical circulators powered
by electric motors. That didn’t strike PSI president and
founder Joel Bleth as
enough of a choice. “Both ways are expensive and neither
is very efficient,” observed Bleth. “You’re
either introducing more chemicals into the environment or running
a big electric motor during peak hours.”
PSI developed, manufactured and installed
its first solar-powered circulators in 1998. Operating from
sunup to sundown 365 days per year, two SolarBees can replace
a 100-horsepower circulator running for five hours a day at
peak load. A shore power option allows the unit to run around
the clock for about $10 in monthly electric charges.
SolarBee helps reclaim lake
for summer fun
Aeration is a practical—and affordable—answer to
odor control for small communities. Residents around Gaynor
Lake in Boulder County, Colo., used the 66-acre, freshwater
pond for water skiing and swimming. However, when the weather
warmed up, algae blooms and fish kill turned the water murky
and smelly.
The Gaynor Lake Homeowners’ Association
consulted an engineer and a limnologist—an expert on freshwater
conditions. The limnologist’s research indicated that
drawing oxygenated water across the oxygen-free (anoxic) water
layer on the lake bottom would clear up the water and eventually
replace the black, plant-free silt with clean sand. “He
suggested a $30,000 SolarBee circulator as an alternative to
draining the lake, which could easily turn into a million-dollar
project,” said association member Jeff Swanson. “The
price was right, so it seemed worth a try.”
Although the SB10000 was installed in June 2003,
too late in the year to completely aerate the pond, residents
noticed that the smell had diminished by September. “When
the wind blew over the lake, it actually smelled like water,”
noted Swanson. “The long, gooey strings of algae on rock
walls and piers were gone, too.”
Working over an entire season from spring thaw
through the summer, the SolarBee is expected to produce a two
to three foot cap of clear water and eliminate the odor and
algae problem without dredging. The association is now considering
the addition of a solar battery pack so the unit can store clean
energy to clean water after the sun goes down.
Reduced need for chemical additives pays
back equipment investment
What one SolarBee is doing for Gaynor Lake, several SolarBees
are doing for a large reservoir in California. Lake Palmdale
supplies the city of Palmdale,
Calif., Water Treatment Plant and supports boating, fishing,
hunting and airplane landings. Aqueduct water containing nutrients
from farms and residential lawns feed the 312-acre lake, creating
favorable conditions for intense blue green algae blooms.
In 2002, the city applied 2,000 pounds
of copper sulfate weekly to the raw water reservoir to control
taste and odor problems. Even with the treatment, the lake was
designated a “no contact” body of water and the
city was able to draw only 25 percent of its 30 million-gallon
daily needs from the reservoir.
The city installed six of SolarBee’s
new SB10000 units on the reservoir in November 2002 and added
a seventh in June 2003. The units were equipped with intake
hoses that distributed oxygen to average depths of 20 feet.
The improved aeration allowed the city to apply copper sulfate
only once that year, saving $65,000 on the chemical compared
with 2002. “The SolarBees cost a total of $210,000 and
the maintenance and operation costs are very low, making the
payback period a little over three years,” said Bleth.
Another benefit was that Palmdale could
draw 60 percent of its water needs from the lake, taking some
pressure off the city’s well fields with their conventionally
powered pumps. Also, the water treatment plant operated much
more efficiently. “Algae can clog treatment systems, and
as long as we keep pouring nutrients into the soil, the algae
problems are going to keep on growing,” Bleth stated.
“Towns can either spend millions of dollars continually
upgrading their treatment plants or they can beat the problem
in the lake using renewable energy.”