Energy: Ways to take advantage of time-of-use billing

Thursday, June 10, 2010

By adjusting your milking times or using a timer on your aeration fans, you can save substantially on your electricity costs

by RON MACDONALD

In a column in the May issue, entitled: What decision should you make about time-of-use billing?, I discussed a new method of charging for electricity using an electric meter that all homes and farms will be living with in the near future. Essentially, every hour, the meter records how much energy you used. This will be matched against the rate pricing that is in force for that hour of use.

For many farmers, this will be an opportunity to save money on their power bill. And for some, it will mean an increase. To better understand the pros and cons of this, I will use some examples.

Example 1: A dairy farm is milking three times per day, at roughly eight hour intervals. Each milking takes three hours.

Since there are two rate periods, summer and winter (see Figure 1), the farm can consider the following options:

• Winter. By milking between 9 p.m. and midnight. (100 per cent off  peak) and between 5:00 a.m. and 8 a.m. (two hours off peak and one hour on peak), and from one p.m. to four p.m. (100 per cent shoulder season), they can for the most part avoid having their highest energy usage occur during the most costly billing times.

• Summer. Although the farm can adjust the times of the day it milks, there is not a lot of advantage as it will still end up with only one off-peak and two shoulder milkings.
Since the difference between shoulder and peak rates is only $0.01/kWh, the savings will be minimal.

The farm may also have other loads that can be operated at different times
of the day, such as feed mixing and unloading from tower silos, manure scraping and pumping.

Example 2. A farmer has aeration fans that need to be run periodically. By operating them at off-peak times only, substantial savings will occur. The easiest way to do this is to install a timer on the electrical circuit to the aeration fan so as to ensure it starts and shuts off at the desired time.

A good quality unit, designed for outdoor use, is required. Since these fans are 230-volt and draw high amps, the installed cost of such a device can easily be $500. Note that the savings can be substantial, including a reduced demand charge.

For farms with a 400-amp and larger electrical service, there is a monthly peak demand charge of about $14.40/kW; for example a 50-h.p. motor would have a demand of about 37 kW. If the fan was only run at night, when the other electrical loads are off, then demand savings per month can be $532.80/ month alone. Clearly, the management of this type of fan control is critical to ensure that moisture is not being added to the grain in the bin.

An energy audit is always a good place to start and there are a number of different ways to conduct an audit

1. Arm yourself with the knowledge required by reading all available material on energy and energy systems. The Ontario agriculture ministry has a number of fact sheets on the topic.

2. A basic audit can consist of a walk through by a competent auditor who understands the basics of the type of farm operation and the implications of adjusting anything on the farm. This person can identify opportunities that most farmers would miss and can review the possible savings and alternatives.

3. A more thorough audit would require more time and cost. It would include monitoring of the operation's electrical load and a compete analysis of the potential savings and technologies available. BF

Ron MacDonald, P.Eng., is an agricultural engineer with Agviro Inc. in Guelph.