How efficient is your oven? – Oven performance

Data from several oven installations shows that the energy usage varies from 0.404 kWh/kg of baked biscuits to 0.492 kWh/kg of baked biscuits. The energy requirement for baking varies with the product. The energy loss depends on the quality of design and construction of the oven.

The energy used by the oven is predominantly from gas or oil fuel. Electricity is rarely used for baking now, due to its high cost. In a gas/oil fired oven the fuel represents around 95-96% of the total energy usage and electricity (for powering the drive, fans and other electrical systems) about 4-5%.

The energy input to the oven is used primarily to bake the biscuit, to achieve the structure, reduce the moisture content by evaporation and to colour the biscuit. Each type of biscuit requires a certain amount of energy to achieve a good quality result.

Energy usage diag

In addition to the energy required to bake a good product, energy is lost in several ways:

  • By extraction of moist air from each oven zone
  • By heat loss through the insulation and outer covers of the oven
  • By the return circuit of the oven band
  • By heat loss from the flues from a heater module or heat exchanger in an Indirect Fired oven
  • By hot air escaping from the oven delivery end

The following is a calculation of heat loss from an actual oven installation (Indirect Radiant oven baking a rotary moulded biscuits at 2000):

 Energy usage

For product                                                      678.4 kWh       56 %

Heat loss from extraction                               220.0               18 %

Heat loss from burner flues                            93.1                 7 %

Heat loss from return band                             87.8                7 %

Est. heat loss of air from oven end                 71.0                 6 %

Est. loss from thro’ metal, fans etc.                30.0                 3%

Heat loss through insulation                           20.1                 2 %

Heat loss from radiation at oven end            17.0                 1 %

Total                                                               1217 kWh       100.0%

 

 Energy usage 2

 

 

 

 

 

 

 

 

The overall oven efficiency is approximately 56%

Of the heat loss through the burner flues, up to 50% can be recovered and used for baking in a Heat Recovery System

HRS oven 2

 

 

 

 

 

 

In this Baker Pacific oven installation the Heat Recovery System reduced the energy requirement by 15%

Read more in the “Baking Process and Engineering” manual at our Training Page

 

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How efficient is your oven? – The products

Each product takes an amount of energy for baking for achieve the correct structure, moisture content and colour. The energy required varies with each type of biscuit, crackers, short dough biscuits and cookies. Each individual biscuit also varies depending on the formulation and quality of the ingredients and the final structure, moisture content and colour required.

Biscuits

Energy is required to bake biscuits as follows:

  1. The dry ingredients must be raised in temperature from ambient to baking temperature
  2. The water in the dough must be raised in temperature from ambient to 100oC
  3. Energy must be provided for the latent heat of evaporation
  4. The water vapour must be raised from 100oC to the baking temperature

The following is a guide to the approximate energy required for different categories of biscuits.

Rotary moulded biscuits:        0.17 – 0.20 kWh/kg of baked biscuits

Hard sweet biscuits:                0.25 – 0.27 kWh/kg of baked biscuits

Crackers:                                 0.30 – 0.33 kWh/kg of baked biscuits

Note: These are theoretical calculations and this is an approximate guide only. Calculations should be made for each formulation and baking profile.

 Read more with “Baking Process and Engineering” manual.