Detecting industrial energy waste

Then there is strategy. And this is where the shoe can sometimes wriggle.

In a manufacturing environment, a strategy can only work if there is enough knowledge and experience to support the vision, but sufficient ROI must also be realised to ensure that everything is worthwhile. But as for Industrial Energy Wastage, there is no research institute anywhere where an industrial plant manager can go to determine what is “reasonable” energy consumption in a production facility. So how can one then assess what part of the current energy consumption is reasonable and what part is wasteful, or what part of that wasteful part provides enough efficiency to justify intervention?

The return we are talking about here includes the cost per kWh charged by the power company. The rates of these vary, depending on the time of day and time of year. Reducing these costs also leads to immediate cost savings. The investment consists of the material and labour required to change the energy consumption. The return is the period of time that must pass before the lower energy bill leads to the creation of returns. What remains after the costs have been paid is then the icing on the cake.

If we then look again at the strategy, how can we estimate how much return these interventions are going to generate if there is no industry standard for reasonable energy consumption against which to measure it?

Profiling Industrial Energy Waste

Energy consumption in the industry varies and this is due to several factors:

• the age of the factory
• the type of load and its format
• operating schedule, both hours per week and intensity of load
• the number of employees
• climate
• the maintenance philosophy.

The answer to this question is: don't try every kW to manage consumed by your facility. These are the ‘knowledge and experience’ in the equation. Divide the facility by electrical infrastructure and then by key systems.

Energy conservation starts with two basic tactics: (1) general inspection of key systems and (2) targeted data collection, including logging energy consumption at main service inputs and at key load points.

Establish what the specified consumption of a system is and how much the system currently consumes. In addition, establish how much waste is occurring (either in terms of hours and type of use of the system or in terms of equipment and the system itself). To realise the savings, this waste needs to be addressed in the facility, through changes in procedures, maintenance or equipment and controls.

Energy components

Before we start looking at how to be able to track energy consumption, we will take another look at how we define and measure energy.

Energy can be expressed in terms of real, reactive and apparent power (Figure 1).

The flow of energy is described as:

• actual (P) or active power in watts (W)
• reactive power (Q) in volt-amps reactive (VAr)
• complex power (S) in volt-amps (VA)
• apparent power, the size of complex power (VA)

The mathematical relationship between real, reactive and apparent power can be represented by vectors or can be expressed by complex numbers, S = P + jQ (where j is the imaginary unit).

Reactive power does not transfer energy - it does not produce labour - and is thus represented as the imaginary axis of the vector diagram. Real power moves energy, so this is the real axis.

The speed of energy flow in a system depends on the load - is it resistive, reactive or both?

With a purely resistive load, voltage and reverse polarity of current simultaneously, the product of voltage and current is positive at all times and only real power is transferred: labour is produced.

If the load is purely reactive, the voltage and current are out of phase and the product of voltage and current can be positive or negative. This indicates that part of the energy is transferred to the load and part of it flows back. The net transfer of energy to the load is zero: no work is produced.

In reality, all loads include a combination of resistance, inductance and capacitance, creating both real and reactive power in a system. Therefore, electrical systems are designed to tolerate a certain amount of reactive power. Problems arise when too much reactive power is generated. Not only is there not enough real power to produce the required labour, but even the system's overall capacity to generate labour is compromised. This is also why utilities fine their customers if their loads produce too much reactive power: it is wasted power because it costs money to generate it, but it cannot be used. Most utility bills count VAr (reactive power) and on many they also calculate the power factor, where the power factor is an indication of how much a system has dropped relative to 100 per cent actual power. Most utilities require their customers to stay above the 0.95 PF (Power Factor) limit.

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Monitoring energy consumption

By understanding the basic components of energy, an electrician can equipment for logging energy consumption set to measure the overall level and quality of consumption and then track when energy is consumed and by what.

Log power at main and secondary panels and at large loads. Record kW, kWh and power factor over a representative time period.

This gives you a very accurate picture of the actual energy consumption for three-phase circuits and loads.

You can achieve the biggest energy savings by determining at what times power consumption peaks, evaluating power factor and total power consumption against utility bills, and rebalancing loads if necessary. Even a peak consumption of just a few minutes can increase the utility's tariff for several hours, days or even weeks.

By scheduling the use of taxes differently, a company can take advantage of times when energy is cheaper. See how far below ‘1’ the power factor is and check the power company's bills to see if there are deductions for a bad power factor. If so, the Power Logger can help trace the sources. After making changes in the necessary power areas, reconnect the logger to check that you are indeed benefiting from these efficiency improvements.

Knowing where energy waste occurs

Every system and process can be a source of waste and this needs to be contained or eliminated. You can already start by scrutinising electrical subsystems, compressed air or steam systems and specific electromechanical systems, but actually every process has potential waste points that need to be measured.

The aim is to map the energy use of specific equipment and processes, to see where energy is wasted so that waste can be quantified. This allows you to prioritise improvements or replacements based on the life of the equipment and see which modifications yield the most return on investment.

Mapping consumption also provides a starting point from which the effectiveness of energy-saving projects can be measured to justify costs.

Common sources of waste in electrical subsystems:

• Taxes sometimes remain switched on outside working hours or are unnecessarily in operation at the most expensive time of the day.
• If no regulation is set on the motor, it may mean that more power is generated than needed.
• Processes with excessive voltage/current cause excessive power consumption to compensate.
• Phase imbalance causes power to be consumed at load without being able to deploy it.

Identify and quantify:

• Make a thermal scan of the electrical panel and mechanical load to check for overheating.
• Log energy consumption over a longer period: how much energy is consumed, at what time and how much waste is involved?

Common waste and inspection points in electromechanical systems:

• Excessive friction due to misalignment, bearings, imbalance and looseness forces the engine to work too hard, consuming too much power.
• Uncontrolled loads sometimes remain switched on outside working hours, operate at peak times, generate more power than needed or suffer from overvoltage/current conditions and phase unbalance.
• Ageing mechanical equipment can use so much more energy than new high-efficiency models that early replacement may be justified by the lower kWh consumption alone.

Identify and quantify:

• Make a thermal scan of the drive panel and mechanical load to check for overheating. Overheating may indicate electrical inefficiency.
• Log energy consumption over a longer period: check for total kWh, power factor, peak demand, imbalance and harmonics.
• Test vibration levels against standards and identify the most appropriate maintenance solutions, such as rebalancing.
• Perform a thermal scan of couplings/shafts/belts, bearings and fans.
• Check current and voltage levels.
• Perform a thermal scan of the termination/connection box and windings and perform an insulation resistance test.

Common waste and inspection points in compressed air systems:

• Excessive leakage in compressed air lines leads to excessive operation to maintain supply.
• Compressors that remain switched on outside working hours waste energy.

Identify and quantify:

• Log energy consumption at the compressor and compare it with base consumption.
• Measure the pressure at the compressor and at the point of use to determine the pressure drop.
• Scan pipes with ultrasound to identify leaks.

Common waste and inspection points in steam systems:

• Defective steam traps and inadequate insulation lead to wasted steam, producing unnecessary steam to maintain the necessary supply.

Identify and quantify:

• Log energy consumption at the boiler and compare it with base consumption.
• Perform a thermal scan of pipes and steam traps to identify missing insulation and blockages.

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Making returns transparent

Considering the aforementioned lack of industry standards, how do we really know which systems have the most potential energy yield? Our best source of information at the moment is provided by the examples of common situations. Here are some examples of common industrial systems.

Electromechanical system inspection

Type of facility: Steel recycling plant in Germany
Type of equipment: fan with belt drive, for process cooling
Measurements conducted: vibration measurements
Problems identified: slight imbalance was detected, in addition to misalignment and bearing wear.
Savings realised: Rebalancing was necessary. A 350-kW engine was running at 80 per cent of its rated power; the measured power was about 280 kW. After rebalancing, 3 per cent less energy was consumed. At a tariff of 0.11 euros/kWh, this results in annual savings of 8,094 euros.

Compressed air system inspection

Type of facility: production
Type of equipment: compressed air system
Measurements conducted: test of compressed air system with ultrasound (recommended full compressor data logging)
Problems identified: the amount of compressed air produced compared to actual demand.
Savings realised: Multiple savings opportunities were found. Total annual savings of €50,600. The compressor is switched off on weekends: annual savings of €32,700. Solenoids are installed to turn off the air supply when machines are switched off: annual savings of €7,100. Repair of 36 leaks: annual savings of €4,800. Filters installed in the system at a one-off cost of €6,000; annual savings as a result of these filters: €6,000.

Inspection of steam trap

Type of facility: production
Type of equipment: boilers and steam pipes
Measurements conducted: thermal scanning of steam pipes
Problems identified: six malfunctioning steam traps; steam leakage from coils of a electroplating tank; steam leakage from electroplating pipes: opportunities for condensate recovery
Savings realised: Six malfunctioning steam traps were replaced at a cost of €500 each. Savings realised: €3,200 per steam trap based on known costs, for generating calculations of steam and heat loss. Total savings: €16,200.
Next step: Log energy consumption on the boiler's supply panel before and after addressing leaks and condensate problems.

Higher productivity or lower overhead?

The next question is a fun one to answer: once you have decided which route to take to reduce energy consumption, can you use those savings to increase plant output (produce higher volumes at the same kWh consumption) or for other business strategies (profit margins, price realisation)?

Reducing energy consumption is simply good for business. By logging the consumption of each major system and mapping these costs against energy bills to determine where and when consumption is occurring, companies can often realise savings through simple adjustments to their processes and work schedules. Companies can easily identify which equipment is inefficient and outdated and justify and prioritise replacement. And by reducing overall energy consumption, companies reduce operating costs and improve their market competitiveness.

Tips for cost savings

Adapt business processes to take advantage of:

• lower energy costs at certain times of the day
• times when machines can be switched off
• sensors and controls that allow systems to be switched off when they do not need to be in operation

Set schedules for start-up/shutdown of infrastructure equipment for working hours and for out-of-working hours.

Start appliances with high energy consumption staggered and at least 15 minutes apart to avoid costs due to peak consumption.

Fit variable frequency drives (VFDs) to large motors and replace bad motors with high-efficiency models.

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