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THE ENERGY GEEK

WORKING TOWARDS SUSTAINABLE COMMUNITIES

Energy Efficiency in Perspective

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Energy is the third-largest expense after building and people for any organization!!

The world today is facing a serious energy challenge with demand for electricity growing every day, there is, therefore, pressure to reduce energy consumption and lower greenhouse gases (GHG) emissions. The simplest way to address this challenge is to seize opportunity for energy reduction and using energy more efficiently!

Energy efficiency simply means using less energy to perform the same task hence eliminating energy waste. Energy efficiency brings a variety of benefits: reducing greenhouse gas emissions, reducing demand for energy imports, and lowering our costs on a household and economy-wide level.

This article hopes to outline some basics small ways on how we would be more energy efficient in our homes and even in Industrial plants.

Energy consumption, always calculated in kWh is a product of the Power rating(Watts)  and running time of a given electrical appliances, therefore the most basic way to lower energy consumption is to find out a way of using an electrical appliance with a lower power rating to achieve the same purpose or reduce its  running hours.

Possible areas of energy saving:-

  1. Lighting

. Residential sector electricity consumption for lighting was about 62 billion kWh or about 4% of total residential sector electricity consumption and about 2% of total U.S. electricity consumption in 2020 according to U.S Energy Information Administration.

They are numerous different lights or lamps that will be found in an electrical lighting system. They include Incandescent lamps Compact fluorescent lamps, Halogen lamps, Metal Halide Lamps, Light Emitting Diode (LEDs), Fluorescent tube, Neon lamps, High-intensity discharge lamps, and Low-pressure sodium lamps. Incandescent lamps are the oldest and the most inefficient type of lighting which how now been replaced by more efficient LED lighting. To be more energy efficient in our residential homes or even in Industrial plants a retrofit of the lighting system with new technology LEDs lights. LEDs produce more light than incandescent lamps and help save energy in energy-conserving devices.

Consider creating awareness and switching off lights when the rooms are unoccupied

LED Bulbs Source: energy.gov

  1. Air Conditioning Unit.

In the typical home, air conditioning will be the biggest consumer of electricity translating to about 16% of the total electricity used. In warmer regions, AC can be 60-70% of your electric bill during summer, according to Austin Energy – a publicly owned utility providing electrical power to the city of Austin, Texas, and surrounding areas.

The higher the AC temperature, the lesser the electricity consumption, however, for comfort 25 degrees Celsius is optimum and most ideal.

Take, for instance, a given day when the outside temperature is say 35 degree Celsius, by increasing your air conditioner temperature from 20 to 25 degree Celsius will result in a   33% energy saving.

Considering the formulae for % energy saving as:

= (New temperature-Old temperature)/ (Outside Temperature-Old Temperature)* 100%

= (25-20)/ (35-20)* 100% = 33%

Assuming that the initial room temperature is the same as outside temperature.

The placement of the outdoor unit for the AC will also impact the electricity consumption. The installation should be at a place free from air restriction. Regular maintenance to unblock the filters from leaves, dust particles, and other foreign materials should be carried out. Don’t miss your annual maintenance contract as well! The rooms where Air conditioning unit is installed should be properly insulated since AC Units are meant to cool enclosed spaces, consider painting the interior white and ensure that the doors and windows are airtight whenever possible. 

  1. Procuring Electrical appliance highest energy efficiency label.

The energy-efficient label, for instance, the ENERGY STAR logo will be on all qualified products that meet specific standards for energy efficiency. The label will show you how much energy an appliance uses compared with similar models, including the estimated yearly energy consumption.

Energy star logo Source: Wikipedia

  1. Electric Motors.

Over 40% of the energy generated worldwide is used in Industrial plants (Factories) with more than two-thirds of it being used to run electric motors! Motor efficiency is defined as the ratio of Mechanical Power output to electric power input.

To put in perspective why the use of high-efficiency motors is of utmost important, It is worth noting that when calculating the total cost of ownership of an electric motor, the capital cost of purchasing a motor accounts only for about 3%, with running cost being between 70-95%(Based on energy cost and annual running hours for 20 years life span) and cost of not running (Based on one unplanned motor failure per year for the 20 years) accounting for about 2-30%.

To illustrate this consider a 300kW rated electric motor of 90% efficiency according to its nameplate. This means that at any given time the motor draws 333Kw of electric power.

That is           (100/90)*300 = 333kW

Taking average energy cost as 0.1$ per kWh and the motor running 8400 hours annually for 20 years life span(about 24hrs every day).

The total running cost for the Motor is 333*0.1*8400*20= $5,594,400.

Suppose this was replaced with a super-premium energy efficiency motor of 97% efficiency.

(100/97)*300 = 309kW

Total running cost for the retrofit 309*0.1*8400*20 = $5,191,200 which translates to a saving of $403,200 over the twenty years life span. This could be understood as a saving of $20,160 annually!

Industrial plant maintenance personal should therefore consider replacing conventional electric motors with Super premium efficiency motors when the motors reach their end life or at most after a maximum of five rewinding cycles. Studies show that Motor efficiency drop by 1% in each rewinding!

Adopting energy-efficient motors would reduce global energy consumption to up to 28% according to ABB-A world leader in manufacturing reliable and high-efficiency motors.

Motor nameplate Source: www.electricportal.info

  1. Installation of Variable Speed Drives for variable Loads.

Source: https://electrical-engineering-portal.com

Variable speed drives (VSDs),variable-frequency drive (VFD) or adjustable-frequency drive (AFD), variable-voltage/variable-frequency (VVVF) drive, variable speed drive (VSD), AC drive, micro drive or inverter drive, also called adjustable speed drives (ASDs), are devices that can vary the speed of a normally fixed speed motor. VSDs will vary the speed of Induction Motors (The most popular type of Motors in Industrial Plants) by varying the input frequency and voltage. Motor motors are oversized to deal with worst case scenario that is, you peak load, ideally what a VDS does is to match amount of energy you need to work that needs to be done. The basic concept with saving for VSD is that the speed with be proportional to energy consumed cubed, that is to say when motor is running at full speed (50Hertz frequency) there is no saving. However, when the speed reduces let say by 10% thus running speed is 90 % (45Hertz = 110/90*50) there will be a 27% saving in cost/ energy consumed!

Why is that so?

A 10% reduction in speed means the Motor will be running at 90% and since speed is proportional with energy consumed cubed.

= 0.9*0.9*0.9 = 0.729 which is 72.9% of energy consumed.

(100-72.9)= 27% saving!

However, it is worth noting that this will give you savings up to 50% speed reduction after which there is no significant energy savings.

The variable speed drives are also beneficial because of there in built soft start capability- this is to mean that they are able to control and reduce the high in-rush current when a Motor is starting, before it attains full speed.

  1. Compressed Air System.

Compressed air is typically one of the most expensive utilities in an industrial facility!

A Compressor is a motor-driven mechanical device used to pressurize the air. The motor can be variable speed or shut on and off. The compressed air then passes through a dryer to reduce humidity and is distributed through pipes out to the plant. The higher the pressure used in a compressed air system or application equipment, the more cost goes into producing this pressure.

The most basic way to reduce wastage thus energy conservation is periodically monitored and repair air leaks along with your compressed air system. Studies have shown that an average of 25% of all compressed air produced is lost because of system leakage and in worst-case scenarios, it can get up to 80%.

Let’s do the maths!

According to https://www.air-compressor-guide.com/compressed-air-systems/rules-of-thumb/  for every Kilowatt, a compressor delivers 4-5 cfm, at 100 psi pressure.

Therefore, a loaded air compressor running about 100 psi (7 bars) consumes about 20 kW per 100CFM. At 10 cents per kWh (0.1$ per kWh), this would mean the cost of the compressed air would be about $2 per hour of operation for every 100 cfm of constant flow.

(20kW*0.1$ per kWh) = $2 per hour.

If the compressor is running nonstop 8,760 hours per year, this 100 cfm flow, it would cost about $17,520 on energy consumption.

($2*8760)= $ 17,520

Suppose your compressed air system has a 30% leakage level that will mean you need to produce 130cfm of compressed air to account for the losses.

(130/100*17,520) = $ 22,776       

Therefore, the electrical cost of producing the air will be about $ 22,776, translating to an additional $ 5,256 annually!

How do you detect air leaks?

The best way to detect leaks is to use an ultrasonic acoustic detector, which can recognize the high-frequency hissing sounds associated with air leaks. There are portable units consist of directional microphones, amplifiers, and audio filters, and usually have either visual indicators or earphones to detect leaks.

  1. Solar water heating and Solar PV Installation.

Solar water heater Solar PV on a roof top

According to a world bank publication on Solar   Power potential 93% of the global population lives in countries that have an average daily solar PV potential between 3.0 and 5.0 kWh/kWp and around 70 countries boast excellent conditions for solar PV, where average daily output exceeding 4.5 kilowatt-hours per installed a kilowatt of capacity (kWh/kWp) – enough to boil around 25 liters of water.

Whereas, installation of solar water heating or use of Solar PV system as an alternative source of power doesn’t improve the energy performance of a facility, it will result in massive savings in cost incurred from utility electricity bills. A solar PV installation for domestic use will have an average simple payback period f about 6-10 years while that of a solar water heater will be between 2-3 years.

 

The use of energy more efficiently will translate to saving energy thus cost. Let us embrace savings and save our planet!!

WORK CITED:

www.air-compressor-guide.com

www.eia.gov

www.energy.gov

https://electrical-engineering-portal.com

www.electricportal.info

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