Thoughts on fan selection in new/remodeled facilities

As producers invest recent profits back into facilities (both new and remodeled), now is the time to give some thought to equipment operating costs. I’m referring here to ventilation fans and their CFM/watt ratings.

While US electric expense ($/kWh) is low by comparison with most other locations in the world where pigs are grown, it is still an ongoing operating expense. Up until last month, forecasts for the cost of electricity were almost 100% upward due to the increasing maintenance costs at our older hydro generation stations, rising costs of emission controls at coal fired generation stations, the higher operating costs of natural gas fired stations and the overall higher cost of alternative energy sources (generally wind and solar).

With the price of crude oil now hovering around $60/barrel versus $100 a few short months ago, the rise in electric generation costs is expected to slow and maybe even stabilize for a few years. However, long term the expectation is for higher electric rates.

The 2 biggest electric expenses in production facilities are the feed delivery motors and the ventilation fans. In terms of managing electric expenses, there aren’t a lot of opportunities in the feed delivery arena. The biggest operating cost savings come in the selection of fans for our facilities.

The BESS Lab at the Ag Engineering Department at the University of Illinois (www.bess.illinois.edu) has been rating agricultural fans for performance for many years. One of the numbers they record/report on every fan tested is the cfm/w – how much air does the fan move at a given pressure per watt of electricity.

Lately I’ve reviewed several facility proposals that included fans with a range of efficiencies. In the case of 24” fans these efficiencies have been at low at 8.7 cfm/w to over 15 cfm/w. While efficiency isn’t the only criteria that goes into fan selection, it should be on the list as fans are selected for a facility.

In many cases 24” fans are the fans on the minimum ventilation stage. As such, they operate 24/7. With the vast majority of controllers installed in production facilities, even when operated as a variable speed stage, the fan consumes 100% of its rated wattage so a difference in cfm/w can dramatically impact operating expense.

Let’s compare 2 fans based on their BESS Labs ratings at 0.05” static pressure. Fan A is rated at 6880 cfm with a 8.9 cfm/w rating (773 w motor usage). Fan B is rated at 7010 cfm/w with a 16.7 cfm/w rating (420 w motor usage). A kilowatt hour is 1000w of usage for 1 hour.

There are 8760 hours in a year. Operating continuously, fan A will consume 6771 kWh of electricity while fan B will consume 3679 kWh, a difference of 3092 kWh per year. If the electric expense is $0.10/kWh the difference in operating expense between the 2 fans is $309.20/yr/fan. For curtain sided facilities where the fan may only operate 70% of the year, the difference is still $216.40/fan/yr.

Many things go into the selection of a particular fan for a given installation – I’ve just demonstrated that efficiency of operation should be on the list of selection criteria as we make the selection, especially for those fans that operate a majority of the year.

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