Tools for better energy efficiency

You can find hidden ‘tools’ on your electricity bill to help keep the cost of consumption down.

When the monthly bad news in the form of the utility account arrives, most of us check that it is indeed our bill and then pay the amount due, without giving consideration to the rest of the information captured on the invoice.

Tools such as a smart meter can help you manage your energy expenditure better, and identify areas of waste or inefficiencies. If you don’t have a smart meter, there is valuable information on your bill that will help you save money and give you a better understanding of how energy is used on your farm.

Monitoring Ratios
For connections exceeding 100 amperes (A), an electrical meter using current transformers is used. A current transformer transforms your supply to a 5A ampere signal. The ratio at which the supply is transformed is referred to as the rx-factor, billing multiplier, or constant. For example, a 150A connection is billed using an rx-factor of 30 (150 ÷ 5). Similarly, a 1 000A electrical connection is billed using an rx of 200 (1 000 ÷ 5).

The consumption measured by a current transformer-type meter is then multiplied by the rx-factor for billing purposes. You should therefore check that the correct constant (or multiplier) is used on your bill. If the rx-factor is not noted on the meter, your local electrician may be able to assist.

Power Factor
Typical power factors for commonly used equipment are as follows:

  • Air compressor and pumps (external motors) – 75 to 80;
  • Hermetic motors (compressors) – 50 to 80;
  • Arc welding – 35 to 60;
  • Fluorescent lighting – 95;
  • Electrical heating – 100.

The power factor will give you an indication of how most of the energy is consumed. If you have a smart meter installed, the power factor can be calculated for shorter periods to achieve a more detailed analysis.

If you are liable for demand charges, it is recommended that you investigate the installation of a power factor correction system, as an uncorrected power factor may have a significant impact on your demand charges. Power correction will also allow you to increase the load on your transformer without having to upgrade it during any expansion of your operation.

If you are on a demand scale-type tariff, you will pay a basic charge based on your maximum demand. As power factor correction will most likely lower your maximum demand, you may fall into a lower basic charge bracket.

Load Factor
The load factor is an indication of how energy is managed on your farm. A low load factor (less than 0,4) means that machinery or equipment that use large amounts of energy are being switched off at night, or that the maximum energy demand is very high.

The load factor therefore indicates the percentage of time your operation is running at maximum demand. Simply put, if you leave a pump running 24/7, the load factor will be 1. If it runs for 12 hours per day, the load factor will be 0,5. If the load factor is not displayed on your monthly bill.

A high load factor means that most electrical equipment is left running around the clock, or that the maximum demand is very low.

Your load factor should be more or less the same every month, and a significant change in load factor can point to a significant change in day-to-day operations, for example during harvesting. Changes in the load factor can also be the result of a faulty meter or a faulty reading.

Management Tool
The load factor is therefore a convenient management tool and can be employed to monitor your staff’s energy usage. It may also prove a boon if you need to investigate the reasons for a higher-than-normal energy bill.

A high load factor combined with a low power factor indicates high usage of electrical motors or compressors. While this is expected in periods of high activity, there may be times during the year when the equipment can be switched off without affecting day-to-day operations.

Of course, with a smart meter, these investigations can pinpoint specific areas of the operations at certain times of the day, if required.