Mattei

Energy Saving M.I.E.M.

Energy Costs

PROTECT THE ENVIRONMENT AND SAVE ENERGY WITH COMPRESSED AIR

Greenhouse effect, ozone layer and the planet's changing climate are just a few of the issues that have interested public opinion in recent years bringing environmental protection and energy saving to light. Companies who rationally produce and use compressed air can contribute to environmental protection through energy savings, as well as decreasing their operation costs. Many public agencies in Europe have established awareness campaigns aimed at compressed air users. Mattei, as a compressor manufacturer, is also fully aware and involved in environmental aspects and has based its research on the improvement of its compressors' efficiency in order to offer a greater saving on energy.

COMPRESSED AIR COST

The diagram refers to one 45 kW compressor installation, 5 year depreciation, 4000 hour/year, operating pressure 7 bar.

ENERGY COSTS ARE MORE RELEVANT THAN THE INITIAL INVESTMENT

The energy cost of a compressed air installation can reach 80% of total costs. All other costs such as ordinary and extraordinary maintenance or the buying cost are relevant but become secondary when compared to electric energy as illustrated in the diagram. The diagram underlies a clear truth: even a small percentage of saving in energy will produce important economic benefits.

EVALUATING EXACT NEEDS

It is thus extremely important to know the exact air needs of the user, together with the depreciation period and all other variables that will help to determine the alternative with the lowest energy consumption. To determine exact air demand Mattei's technical staff is at your disposal to analyse your compressed air needs. This analysis involves the recording of current energy consumption on a daily or weekly basis.

Typical User Profiles

Profile n. 1
This profile represents an application with an eight-hour shift at constant consumption for five days a week. Air demand tends to stay around 90% of maximum requirement.

Profile n. 2
This is represented by a unit running for 16 hours a day and 5 days a week. Air consumption varies from 70 to 100% of maximum air demand.

Profile n. 3
The unit runs 24 hours on 24 for 7 days a week with consumption variability between 70 and 100%.


Regulation System

A central aspect for the evaluation of a compressed air plant's economic operation is the concept of regulation

ON/OFF

This regulation maintains the line pressure within a range of minimum and maximum pressure set by the pressure switch and the compressor may stop and restart according to air demand.

When the pressure reaches the maximum value the compressor will run off load with the immediate closure of the intake valve and the start of the decompression phase.

The best compressors absorb 20-25% of full load power during off load operation. When the minimum pressure is reached the compressor operates full load with the immediate opening of the intake valve. In order to avoid frequent stops and starts, which can damage the asynchronous three phase electric motors, a receiver is normally installed.

CONTINUOUS/MODULATION

With this regulation air delivery is automatically adapted to the system demand through the intake valve. The compressor's regulation depends on the air distribution pressure and thus on air demand.

ROTATIONAL SPEED CONTROL

Recently some manufacturers have introduced compressors equipped with systems which electronically vary the motor rotation. The system tries to keep a maximum efficiency relationship between air demand and energy consumption.

Volumetric compressors are, however, designed to run at a set rotational speed at which they give maximum efficiency. At different speeds from the nominal speed, there is a substantial decrease in the specific energy of the system.


Absorbed Power

The true quality of an air compressor is given by its specific energy or efficiency, which identifies the energy needed to produce a given quantity of compressed air.

Specific energy is the result of the following formula: kW/(m³/min)

where kW stands for the absorbed power, that in a three-phase system is calculated as indicated below: