Friday, 14 March 2014

John Guthrie, Energy Efficiency Manager, ABB writes: The use of pumps in many industries are the heart of the production process, moving liquids from one place to another, be that moving beer through the production process or moving wastewater through a treatment works.

It is no surprise then that in industries like water and wastewater treatment we see a lot of pumps installed to help manage the flow of water through their facilities; it is a necessary process which have to be reliable and efficient.

This theory that pumps have to be reliable and efficient, while ringing true, is one that is traditionally put into practice by electrical engineers and plant management by specifying large pumps to take into account occasional peaks in demand.

This is often done when specifying a pump and motor combination based on peak demand requirements, then the addition of a 10 percent up-size to satisfy the electrical engineers own safety margins and then another 10 percent up-size to satisfy the plant managers’ demand safety margins.  This leads to a 20 percent over-sized pump that is running constantly with damper and vane control used to regulate demand.

While this over-sizing approach may seem a perfectly logical one to safeguard the capacity of the plant, it is slightly flawed when you consider that the full capacity of the pump is only required for short periods of time.

This therefore means that the pumps running capacity is being wasted and is operating the motor and pump combination too frequently and using vast amounts of electricity to do so. If you then consider that this is only one pump application, and there are potentially tens of other pumps running in exactly the same way, the energy being lost starts to really add-up.

Fitting a variable-speed drive to such an over-sized pump can have extremely dramatic effects on both the running time of the pump and the electricity it consumes; with the frequency inverter setup slowing the pump to match normal demand and speeding it up to full capacity when required capable of delivering a 40 percent saving in electricity consumed.

This variable-speed control solution still gives you the flexibility you need to meet demand surges and does not reduce the capacity of the plant to cope with this; it simply uses the pump more intelligently to run more slowly and consume less energy when demand drops.

Putting this into context across industry, 10 percent of the electricity consumed by industry is by pumps, consuming 1.850 TW/h of electricity, and when you consider that reducing pump speed by just 20 percent can reduce the power by up to half, then pumps are the biggest area for energy savings.

A pump consuming 50kW and running for 48 weeks a year consumes over 400,000 kWh, but if this same pump was controlled with a variable speed drive and the speed reduced by just 10 percent then it would consume around 100,000 kWh less, which is a saving of around 25 percent.

If all pumps in the world were controlled in this way, then the savings potential is 740 billion kWh or the same amount of energy from 176 coal-fired power plants.

This is only by looking at pumps alone, there is further potential when looking at fans, and compressors too.

Contact ABB or an authorised value provider to assess the scale of savings potential for your plant.


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