The electrodialysis system was
portable and mounted into a trailer
that was plugged into an electrical
outlet. Wine was pumped from the
fermentation tanks to the electrodialysis
trailer and processed through as
many loops as necessary to reach the
desired wine conductivity. The cold
stabilization system included a dedicated
chiller supplying glycol to cool
two 9,250-gallon tanks. The glycol
was chilled through a 40 horsepower
water-cooled reciprocating compressor
and pumped to the stabilization
tanks, which were located in a room
kept at approximately 50°F. This study
examined cold stabilization in its most
basic form, with no mixing, seeding,
or any processes that would otherwise
speed the rate of crystallization.
First study —
Cold stabilization hard pressed to
match efficiency of electrodialysis
Results indicated that electrodialysis
was significantly more energy
efficient than basic cold stabilization,
completing the clarification
process with just 7.9 Wh per gallon
of electricity versus 1,200 Wh for
cold stabilization. In addition, electrodialysis
resulted in demand savings
— energy saved during the
region's most energy-intense time
periods — of up to 79%. Further
benefits of electrodialysis included
an increase in the stabilization rate
and a significant reduction in stabilization
time.
The electrodialysis system required
two water lines. This water moved the
brine solution after dialysis occurred
and performed required system cleaning.
Based on manufacturer specifications,
the equipment can process wine
for around 12 hours before it requires a
1.5-hour cleaning. After adjustments,
the additional water used to stabilize
the electrodialysis test batch was
reported at 14% of the total volume of
processedwine, or 3,010 gallons.Wastewater
is released to winery industrial
drains as with cold stabilization.
Editor's Note
The STARS equipment manufacturer
requires that soft water (water containing
little or no dissolved salts of calcium
or magnesium) be used for the ED
process, thus reducing water consumption
from 14% measured in this study, to
7% to 8% on a normal basis.
In addition, WineSecrets operates a
new water conservation module in tandem
with the STARS unit, using reverse
osmosis (RO) to recycle water used by
STARS. The RO unit reduces water use
to approximately 3% of treated volume,
and the tartrate-rich stream is saved for
recovery and recycling.
|
| Table II: Study results: electrodialysis compared to cold stabilization |
|
Electrodialysis |
Cold stabilization baseline First test |
Cold stabalization Second test |
Observations |
| Wine Variety |
Pinot Grigio |
Pinot Grigio |
Chardonnay |
According to winery personnel, Chardonnay is easier to stabilize than Pinot Grigio. |
| Volume of stabilized wine |
21,500 gallons |
18,500 gallons |
24,000 gallons |
Electrodialysis reduces wine loss |
| Enhancement |
n/a |
None |
Seeding |
According to winery personnel, seeding reduces cold stabilization time by approximately one-third. |
| Increase in water consumption |
3,010 gallons |
0 gallons |
0 gallons |
Electrodialysis (14% of total wastewater must be wine volume) treated |
| Tank |
n/a |
Un-insulated tanks caused buildup of ice, which required additional refrigeration. |
3 inches of insulation |
Ice buildup required additional refrigeration/more energy; separate study shows that insulation saves significant energy |
| Wine temperature |
n/a |
Cooled to 28.5°F |
Cooled to 31.4°F |
Cooler temperature means more energy consumption |
| Average demand |
5 kW |
24 kW |
4.4kW |
|
| Stabilization time |
31 hours (1 day + 7 hours) |
1,108 hours (46 days + 4 hours) |
122 hours (5 days + 2 hours) |
|
| Energy intensity |
7.9 Wh per gallon |
1,200 Wh per gallon |
22 Wh per gallon |
|
|
There were two hiccups during the
test. The first was when the cold stabilization
refrigeration system had to be
shut down for repairs. Because of this
breakdown, the actual stability duration
was 63 days; however, to better
reflect a more realistic time lapse, the
net cold stabilization period was
recalculated at 46 days (1,108 hours).
The second glitch occurred when a
glycol leak was detected in the refrigeration
system. This was repaired and
the cold stabilization test results were
normalized to account for this short
interruption.
Second study —
Searching for more cold
stabilization savings
Armed with information from the
cold stabilization and electrodialysis
assessment, and in an effort to learn
how cold stabilization energy efficiency
could be improved, PG&E commissioned
BASE Energy to conduct
another study (August/September 2007),
which offers a comparison between the
un-enhanced, baseline stabilization in
uninsulated tanks at Fetzer with cold
stabilization using seeding in insulated
tanks
|
at a second site. In the second
test, seeded (or contact process) cold
stabilization was performed on 24,000
gallons of 2006 Chardonnay in insulated,
jacketed stainless steel tanks.
The second test showed that there is
a significant difference in energy consumption
in cold stabilization, depending
on a number of factors including
wine variety, enhancements such as
seeding or filtration,
tank insulation,
and desired wine temperature.
One observation is that insulated
tanks may significantly reduce energy
consumption, which confirms another
recent PG&E study. In addition, seeding
and a slightly higher cooling temperature
save energy also. In the end,
these cold stabilization enhancements
cut energy use from 1,200 to 22Wh per
gallon. A comparison of electrodialysis
and the two cold stabilization tests is
shown in Table II.
|
