How much electricity does a bakery save with a mixer timer or by making a slurry before mixing?

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Accepted Answer

The profile by The Energy and Resources Institute (TERI) on Coimbatore bakeries says mixers run 15 to 20 minutes a batch and often longer, and that a slurry of everything but flour cuts about 10 minutes a batch. On a 5 horsepower mixer, 10 minutes is about 0.7 kilowatt hours (kWh) a batch on the rating, our upper estimate. Baking is the major energy use in a bakery. The other area is the mixers, which use electricity, on motors generally of 3 or 5 horsepower. Some mixers come with timer settings. Timer switch: mixing takes 15 to 20 minutes depending on the product, but mostly runs over because nobody switches the motor off at the end of the batch, the profile says, and the motor keeps running past the batch. A timer switches the motor off after the set time. Slurry: all ingredients are mixed together and the mix is kept for 15 to 30 minutes. The profile suggests a slurry of every ingredient except flour, made ready beforehand and poured in with the flour. That cuts mixing time by around 10 minutes a batch, which it calls significant, and improves bread and bun quality. The profile's two passages differ on mixing time, 15 to 20 minutes in one and 15 to 30 in the other. It gives no kWh saving or cost for either. Our arithmetic. A horsepower rating is the motor's shaft output, and the motor draws more than that from the supply, by its efficiency. A mixer under load usually draws less than its rating, but a motor can also run above it, so this is a rough upper estimate, not a hard ceiling. 5 horsepower is 3.73 kilowatts (kW), since 1 horsepower is 0.746 kW. At an example motor efficiency of 0.9 that draws 3.73 / 0.9 = 4.14 kW, so 10 minutes saved is about 4.14 x 10 / 60 = 0.69 kWh a batch. At an example 6 batches a day over 300 days, that is 1,800 batches and about 1,243 kWh a year, or 839 kg of carbon dioxide at 0.675. The profile's cluster totals give an average bakery 10,000 kWh if spread over 700 bakeries, or 19,300 kWh over about 360. So 1,243 kWh is roughly 6% to 12% of an average bakery's electricity, and less in practice. If a mixer overruns by 5 minutes on each of 6 batches a day, that is 30 minutes a day, about 2.07 kWh, or about 622 kWh over 300 days. The profile does not say how long mixers overrun. Time a few batches with a stopwatch. Read the motor's kilowatts off the rating plate. Stopwatch five batches of each product and note the minutes the motor really runs. Kilowatts x hours, divided by the motor's efficiency, is the upper estimate. Compare with your month's total on the bill to see its share. If it is small, put your effort into the oven, which the profile says takes the major share.

How much electricity does a bakery save with a mixer timer or by making a slurry before mixing?

What the profile says

How big can it be? An upper estimate

The timer part

How to check it on your own bakery

A 5 horsepower mixer (example batches)

What Senseible does here