Energy Equivalents Guide

A uniform method for calculating the energy requirements for a process. The accounting procedure is based on the KJ of energy usage. This requires a consistent basis for evaluating the energy of all utilities and raw materials consumed.

The equivalent energy is the factor to be used to put all energy requirement estimates on a common basis. For this purpose, an equivalent energy is defined as the KJ of fuel or energy that is consumed in generating a given utility.

Fuels

For fuel energy consumption, the definition is the energy equivalent is defined as the heat of combustion.

Electrical Power

For purchased electrical power from a public utility, the accounting for KJ is more involved. While one KWH of electrical energy is capable of producing 3600 KJ of heat, this is not the number to use.

Rather, the amount of energy required to produce the KWH of electrical energy should be used. Typical delivered public utility generation efficiencies (including line losses) are less than 35 percent. Therefore, if the local utility has an efficiency of say 30 percent, the equivalent energy usage per KWH is nominally 12,000 KJ.

Steam

The fuel used in generating steam is what should be used as the energy equivalent. This means that the energy equivalents are based on the boiler efficiencies.

Condensate

Collecting condensate and returning it to the boilers, reduces the boiler make-up water requirement and save both the heat content difference between the hot condensate and fresh water as well as reduce the pre-treatment energy requirements. This depends on the quality of the returned condensate as well as the temperatures of the condensate and fresh makeup water. 

Other Utilities

For other utilities such as water and compressed air, the equivalent energy requirements are the energy equivalents used for