Practical Winery
65 Mitchell Blvd, San Rafael, CA 94903
phone: 415-453-9700 ext 102
email: Office@practicalwinery.com
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September/October 2008
WINEMAKING
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.
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