VSDs in energy saving applications
How can a VSD can save you money ?
Ashdale Engineering Ltd has a weatlh of experience in helping clients save energy by installation of correctly specificed VSD solutions on projects throughout Northern Ireland from our Belfast office. Here we look at the principals involved and how a varible speed drive works and why it will have savings if installed on pumps and fans.
Electric motors account for approximately 60% of the total energy used in the workplace and the majority of these motors are on fans and pumps. Most industrial applications simply switch on and off these motors without any thought to the energy used and are designed to allow these units to run at full speed. The only way to control the speed of an AC motor is to alter the frequency and this is achieved with the addition of a Variable Speed Drive. In almost all of these applications, the addition of a VSD will have two major effects.
Will allow better control of the process.
Will allow a reduction in motor speed, in turn consuming less energy which will reduce costs
VSD vs. DOL
Mitsubishi Electric VSD vs. DOL
A live demonstration of VSD energy saving
Matt Handley, Product Manager UK, Inverter Drive Systems & LVS, explains the simple, but practical energy saving live demonstration of variable speed drive verus direct online starting of pumps and fans with Mitsubishi Electric in this video.
Cube Law - how it saves you money
(And why you need a variable speed drive)
Cube law
As pump and fan applications work from a cube law, if the speed of the motor is reduced by 10%, the power will reduce by the cube of this. So a 10% reduction in speed equates to a 27.1% power saving. In real terms then, by reducing the speed of a fan from 50Hz to 45Hz (or 10%) it will achieve this saving.
Cube Law Explained
The relationship between the speed and power of a fan or a pump is called the Cube Law and can be built up step by step.
The flow is proportional to the speed: 10% slower = 90% flow.
The torque is proportional to the speed squared
The power is proportional to the speed cubed.
Since it is the power that costs the money the graph shows what it look like in practice.
By example the savings can be put into monetary terms by assuming the following parameters:-
Fan motor size = 30kW
Average cost of electricity = £0.13 per kilowatt hour
Hours run = 16 hrs per day and 300 days per year
Without speed control, it would cost £18,720.00 to run this fan each year. Fitting a VSD and reducing the fan speed by 10% it would cost £13,646.00 which equates to a saving of £5,074.00 per year on-going.
This is true of all pump and fan applications and the savings go up exponentially the further the speed can be reduced.
Pump and fan applications will give the best energy savings but fitting a VSD to any electric motor and reducing the speed will save money.
Frequency Inverters – VSDs
Frequency Inverters – FR‑F800
Designed for unparalleled energy saving, optimised speed control, simple start-up, and versatility, Mitsubishi Electric has developed a new generation of drive technology: the remarkable FR‑F800.
The FR‑F800 is mainly designed to be used with pumps, fans and compressors and HVAC applications. It features many innovative functions that allow for the best compromise between efficiency and accurate control.
From our Belfast offices in Northern Ireland, Ashdale is proud to sell and support Mitsubishi Electric VSDs and are proud to be their premier partner in NI for Variable Speed Drives in NI.
Energy Efficiency Capital Grants
Energy Efficiency Grants (EECG)
Frequency Inverters (VSD) when used in applications such as Heating and cooling equipment including high-efficiency boilers, intelligent heating controls, heat recovery projects, heating, ventilation and air conditioning (HVAC) equipment and refrigeration equipment. Replacement drives or motors including variable speed drives (VSD) and high-efficiency motors will qualify for carbon reduction grants which are frequently available through the UK government.
In Northern Ireland grants maybe available at https://www.nibusinessinfo.co.uk/content/covid-19-energy-efficiency-capital-grant
and Invest NI also offer help and support at https://www.investni.com/support-for-business/reduce-waste-and-save-energy
It’s worth checking in your region what grants are available and also through the carbon trust https://www.carbontrust.com/what-we-do/green-finance