Energy together with personnel accounts for the biggest operational budget of wineries. In order to be cost and therefore price competitive, it is essential for wineries to ensure effective and optimal functioning and utilisation of refrigeration facilities.
Daily checking to ensure that a refrigeration system is used optimally may ensure that contractors are not called out unnecessarily to solve what might be a simple problem, but if the necessary expertise does not exist, it is better for the cellar to prevent possible problems well in advance, rather than wait for the problem to manifest itself.
Estimates show than 50% of Australian wineries’ electricity bill is allocated to refrigeration. By minimising cooling requirements and optimising the effectiveness of the refrigeration system, this percentage may be reduced. There are different ways of achieving this.
Most wineries use cooling in the settling process of grape juice for pre-fermentation clarification. Good sanitation practices, effective pH and sulphur dioxide management, timeous racking after settling and the possible use of centrifugation, flotation or cross flow filtration may reduce refrigeration cost for the process. It goes without saying that the purchase of equipment has to be acceptable from a quality and cost point of view.
It is generally accepted that low temperatures during the vinification process limit spoilage and improve the retention of desirable wine flavours. The question arises, however, whether the chilling temperatures might not be excessive. Excessive chilling may be caused, inter alia, by inadequate temperature settings, incorrectly calibrated temperature sensors or dirt in automatically controlled solenoid valves.
Although cooling is commonly used for tartaric stabilisation of wines, it may be applied much more effectively by using it in conjunction with agitators, heat exchangers and tartaric acid dosage.
The adaptation or design of cooling systems in existing or new cellars should always be undertaken by an experienced refrigeration engineer. The planning process should include a variety of decisions for which the necessary expertise is a prerequisite. Refrigeration is a specialist field that covers various disciplines from design to maintenance of refrigeration equipment.
Apart from the design and extent of refrigeration, the effective application thereof may be determined by various factors. Sufficient isolation of the specific equipment is essential and should focus not only on the macro components such as tanks and pipelines, without paying the necessary attention to bolts, clamps and valves. The design of the cooling jackets influences the thermal currents inside the jackets and this, combined with stirring the contents of the tank, may result in improved heat exchange. In a similar way the distance between the cooling plant and the tank stores, the tank store design, exposure to sun and wind, tank colour and the placement of the store vis – vis exposure to sunlight may have a big influence of the effective utilisation of the available cooling. The cross flow of pre-chilled media or products compared to that which still has to be chilled by means of heat exchangers may also result in considerable savings.
A guide to energy efficiency is available from www.industry.gov.au/energybestpractice (Day, 2005).
Each winery has a unique set of cooling facilities as a result of the different winery requirements and winemakers should not adapt or change the refrigeration systems of their cellars without the input of experienced refrigeration engineers or contractors.
There is, however, a check list to ensure the effective operation of winery cooling facilities and considerable savings may be achieved if the check list is consulted regularly.
As the cost of electricity is usually cheaper outside peak periods, this may be exploited with careful planning. For white wine fermentation, for example, the switching on or off temperatures of the cooling system may be different for peak and off-peak periods, without reducing the effect of the cooling (Semmler, 2005).
Day, C. 2005. The contribution of refrigeration processes to winery sustainability. Wine Industry Journal 20 (4): 63 – 65. Semmler, B. 2005. Improving winery refrigeration efficiency for small to medium wineries. Wine Industry Journal 20 (4): 57 – 58.