PSAA Curriculum Unit Physical Science Systems

Problem Area Energy and Power Systems

Machine Performance Efficiencies Lesson

What factors have to be considered in order to determine if a machine is performing efficiently or not performing its tasks efficiently? ► What is the concept of efficiency? ► What is the concept of mechanical efficiency? ► What is the concept of performance efficiency? ► What is the concept of field capacity? Theoretical field capacity? Effective field capacity?

Why is machine efficiency so important in today’s agricultural industry?

Learning Objectives ► Define efficiency, performance efficiency, mechanical efficiency, and field efficiency. ► Identify theoretical field capacity and effective field capacity and the relationship between them. ► Identify how efficiencies are determined and how efficiencies are used to size and select machinery and equipment.

Terms ► Effective field capacity (EFC) ► Efficiency ► Field capacity ► Field efficiency ► Input ► Mechanical efficiency ► Output ► Performance ► Performance efficiency ► Theoretical field capacity (TFC)

What is the difference between efficiency, mechanical efficiency, performance efficiency, and field efficiency? ► ► Efficiency is the ratio of a machine’s output over its input. ► ► Efficiency is calculated by dividing the output by the input. ► ► Output and input have the same units, so it is common to express efficiency as a percentage. ► ► Performance of agricultural machines is measured by the rate an operation can be completed, and/or the quality of an operation.

Performance Efficiency ► ► Performance efficiency describes the quality of work done by a machine. ► ► An example of performance efficiency would be harvesting efficiency such as the amount of crop left in the field due to poor machine performance.

Combine Harvesting Efficiency

Mechanical Efficiency ► ► Mechanical efficiency evaluates energy conversion and energy converters. ► ► Mechanical efficiency answers the question, how well does the machine convert energy from one form to another? ► ► Examples include the conversion of chemical energy to heat energy to mechanical energy in an internal combustion engine and the conversion of electrical energy by an electric motor to mechanical energy.

Field Efficiency ► ► Field efficiency is the comparison of the time a machine actually spends doing what it was designed to do compared to the total time the machine was in operation.

Farm Implements are Capable of Working Many Acres per Hour

What is meant by theoretical field capacity and effective field capacity? ► ► Theoretical field capacity (TFC) is the acres per hour a machine covers when operating at a given speed through its effective width. ► ► Effective field capacity (EFC) is the actual rate of acres per hour a machine can cover.

Theoretical Field Capacity ► ► Theoretical field capacity (TFC) is the acres per hour a machine covers when operating at a given speed through its effective width. ► ► Theoretical field capacity for a machine is calculated using the Unit Factor Method. TFC (Acres) Hour = Speed (Miles) Hour xWidth (Feet)x 5,280 Feet 1 Mile x 1 Acre 43,560 sq.ft.

Effective Field Capacity ► ► Effective field capacity (EFC) is the actual rate of acres per hour a machine can cover. ► ► Simply observe the machine in operation doing what it was designed to do for one hour or fraction of an hour.

Effective Field Capacity ► ► Determine the acreage that the machine actually covered. ► ► This represents the effective field capacity. ► ► The percentage field efficiency is calculated by dividing effective field capacity by the theoretical field capacity and multiplying by 100.

What are machine efficiencies and how are they used to size and select machinery and equipment? ► ► Efficiencies provide a measure of machine performance. ► ► Power sources rate the mechanical efficiency of the energy conversion process. ► ► Field machines are evaluated by their field capacity and field efficiency. ► ► Performance efficiency measures how well machines do their job.

Machine Efficiencies ► ► Efficiency is the ratio of the output over the input for a machine. ► Inputs are often difficult to measure. ► Therefore, output plus losses by the machine may be used as an estimate of input.

Machine Efficiencies ► ► It may be difficult to measure exactly how much corn enters a combine (input), but we can easily measure the actual corn harvested (output). ► ► We can also measure the corn lost in harvest by the machine (harvest loss), due to the dropped ears and downed stocks (preharvest loss).

Machine Efficiencies ► ► Recognizing that the difference between input and output is the loss, the expression is: input – output = losses. ► ► Solving for input sets up the equation as: input = output + losses.

Machine Efficiencies ► ► Efficiency is an important consideration in the evaluation of power losses, the selection of agricultural machinery and equipment, and machine operations. ► ► The equation allows us to determine efficiency even when inputs cannot be measured accurately.

Proper Sizing and Selection of Machinery and Equipment

Machine Efficiencies ► ► Substituting the output + losses for inputs means the equation will read as: % efficiency= output output + losses × 100

Machine Efficiencies ► ► The expression describes performance efficiency where outputs and losses can be measured and inputs cannot be measured directly. ► ► The rate at which a field machine does work is expressed as a unit area per unit time, and labeled as field capacity.

Field Capacity ► ► Field capacity is a function of speed, effective machine width, and unproductive time. ► ► Careful layout of fields and thoughtful patterns of machine operation can improve the effective field capacity and also the field efficiency.

Machine Efficiencies ► ► Non-productive time (losses) such as non- working turns and idle travel across field ends and the interior of the field should be minimized. ► ► Measurements or estimates of machine capacities are used to schedule field operations, power units, and labor, and to estimate machine operating costs.

Review/Summary ► What is the difference between efficiency, mechanical efficiency, performance efficiency, and field efficiency? ► What is meant by theoretical field capacity and effective field capacity? ► What are machine efficiencies and how are they used to size and select machinery and equipment?