Heating and cooling your wine

The past two weeks have seen rather low temps at night, which have slowed my ML fermentations down quite a bit.

Harvest is when my energy usage is at its peak, most of it going into cooling during the early part of harvest, which then turns to a need for heating at the end of harvest. A winery’s heating and cooling is generally the lion’s share of the total energy usage of any winery.

Because of the amounts of CO₂ that are generated by fermentation, remote operated fans are constantly flipping on and off drawing out the invisible gas and replacing it with breathable air from outside the winery. At the start of harvest, that outside air is usually pretty warm due to our Indian summers, and that has a tendency to cause the ferments to spike temps upwards…which of course, speeds up the fermentation, releasing more CO₂, thereby needing more exhaust, etc…

It’s a vicious circle: on the hottest days, you pump out your coolest air (replacing it with hot air from outside) to make the cellar a safe place to work while simultaneously causing the ferments to pump more CO₂ into the cellar. Nighttime temps are still relatively warm at the start of harvest, but cool enough to moderate the ferment speeds, so much of the cooling is attempted by drawing in air at night – a great strategy in cool coastal areas, or an area where fog is common.

In the cooler harvests, we see the opposite with exhaust fans drawing in a large amount of cooler air and retarding the ferment speeds, and that might keep us from extracting as much flavor and color from our red fruit as possible. Warming is our task here, and the need for exhausting gasses puts all our warmed air out into the environment instead of keeping our ferments going strong. But higher spikes can cause problems for both yeasts and bacteria and may cause “off” flavors to be formed in your wine. Usually, we’re looking for our white ferments to stay in the mid 60’s (°F) and our reds to be mid 80’s - the higher temps for red are needed to extract the cooler and tannins properly. The Primary ferment (the conversion of sugar to CO₂ and alcohol) causes much more heat to be released than the Secondary (ML) fermentation does, and that’s reversed from our needs for heating, as the Primary happens when its warmer, and the secondary when the weather has cooled quite a bit.

Most times we need the wines to finish with the ML ferment before we can add SO₂ and stabilize the wines…and that is sometimes delayed due to the ML bacteria needing higher temps to work to completion. Since this fermentation happens when the nighttime air we draw in is quite a bit cooler, we generally need to heat at this point.

Ways to create wineries which are more energy efficient are well known, and include the above mentioned passive cooling of night air, insulation for any tanks which are outside – as well as the buildings, and possibly using a cave to keep the wines cool.

Many more wineries are exploring solar panels to help them offset the energy needed for production, and that is buoyed by the wineries which have already installed them and have good results. It’s a good time for creating a new winery since technology has progressed, and even for retro-fitting an older winery to make them more efficient. And the press for "greening up" your operation has never been better...

A true win-win situation for all.