MECHON Concepts - Ideas for Workplace Improvements - Edition 05/08

MECHON Concepts - Ideas for Workplace Improvements - Edition 05/08 from Mechon Limited

By: Mechon Limited  07/08/2009
Keywords: heating, environment, Recycling

Recover Energy Losses from LEV Systems - Our latest publication providing useful ideas to improve employee protection and create efficiencies within the workplace

We are all to aware of the mounting pressure on manufacturers to improve production efficiencies , not only to reduce our carbon footprint, but to also benefit from lower energy bills.

At the same time as trying to improve energy efficiencies, employers are also obliged to ensure that employees are fully protected from inhaling harmful dusts and fumes though the use of local exhaust ventilation (LEV) systems. The use of these LEV systems do however have a significant impact on our energy usage.

How Do LEV Systems Reduce Energy Efficiencies?

The obvious cause of energy loss is due the motor power required to extract the contaminated air from the process and discharge it to atmosphere (sometimes after filtration). These losses can however be minimal when compared to the energy lost in the heated or chilled air when it is discharged to atmosphere.

When LEV systems extract air from the production facility, that air needs to be replaced with outside air, usually drawn in through open doors, windows, louvres, or through general building leakage. This incoming air is then heated or cooled to maintain a comfortable working environment, before being extracted by the LEV system and discharged back to atmosphere.

Are These Losses Really That Significant?

These losses can be significant and are better explained by means of calculation.

Let’s consider a medium sized fume extraction system with an extraction rate of 4 m/s.

In peak winter periods the external air could be as low as 0C and the internal environment kept at a constant 21C.

The LEV system draws in the 0C air from the outside. The heating system then warms this air to 21C to maintain a comfortable room temperature, after which the warm air is extracted by the fume system and wasted to atmosphere.

Based on the above figures, the energy lost to re-heating the air will be approximately 100kW.

Assuming the extraction system is in operation for twelve hours a day, five days a week, and over the entire winter period (say 6 months), the energy lost to atmosphere could be as high as 156,000 kWh per year.

The total cost to the company would thus be £4,700 per year.

This cost will rise even further if heating if achieved by electricity (as opposed to gas ).

So How Can You Reduce the Energy Losses Caused by LEV Systems?

There are a number of ways in which to reduce the energy loss, the most common being:

-   By installing heat exchangers in the contaminated airstream and preheating incoming air or water

-   Recirculating filtered air back into the building

-   Limiting the operation of the LEV system to when it is only required (through remote stations or detections systems)

-   Only extracting from hoods in use (by manually or automatically shutting down unused hoods)

How Can We Help You?

MECHON are able to provide a free-of-charge service to evaluate your LEV systems and their associated losses. We are then able to estimate any future cost savings and the cost of rectifications required. Contact our sales team by phone or email for further details.

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