Wednesday, 30 March 2016


Carl Turbitt, ABB's UK HVAC Drives Team Leader writes: Have you ever tried watching a movie inside a cinema that’s either too hot or too cold? If you have then you’ll know that it can end up being an annoying distraction from your perusal of a good film.

As a cinema operator you want to be sure that your customers are comfortable for the duration of the film, and enjoy a pleasurable experience so that they will keep coming back again and again. It’s one thing for cinema-goers to complain about the quality of the script, or the action sequences – that’s largely beyond your control – but the last thing you want is people giving their viewing experience one star solely because they were too hot or too cold, especially when this can be very easily avoided.

Of course, no one ever notices when the temperature is just right, but when it comes to climate control and HVAC systems that’s exactly the way it should be.

In a large multiplex, the nature of film screenings means that over the course of a day an individual auditorium will often only be partially occupied for much of the time, if not empty. Most screens are typically occupied for around six to 12 hours a day, with higher occupancy for the more popular evening and matinee showings, or immediately following a major new release, such as the recent instalment of a certain space-themed movie set in a galaxy far, far away. This means that each screen can have long periods of downtime or partial occupancy, and if your HVAC system is still running flat out whether the auditorium is full or empty, you could be wasting heaps of energy and money.

Clearly HVAC requirements for when there are five people in the auditorium will differ to when there are 200 people in the auditorium, and can also depend on other factors such as the weather or time of year. The number of people makes more difference than you might think; a recent Russian study found that a screen of 200 people generated nearly 16 times the amount of heat as a screen of five people (89,900 kJ compared to 5,645 kJ), and 40 times the amount of moisture (8 kg/hour compared to 0.2 kg/hour), adding significantly to the room’s relative humidity.

It follows then that it’s therefore not necessary to run the heating, ventilation and/or air conditioning at full power all the time if it is not required. Normally in periods of low demand the HVAC motor’s output will be regulated using mechanical means such as valves and dampers.

But while these mechanical methods may reduce output, they don’t actually save any energy as the motor will still be running at full power irrespective of demand. Over the course of weeks, months and years, this can end up costing a lot of money.  Why not start saving now.

Variable-speed drives (VSDs) allow the motors that power the pumps, fans and compressors that make up HVAC systems to be run at lower loads, and are therefore ideal for cinemas, or indeed any venue where the number of visitors fluctuates, such as theatres, concert halls and sports arenas. A VSD regulates the motor’s output, so rather than running at full power and using mechanical means to regulate the air flow, a VSD ensures that the motor operates only at the speed required, using only as much energy as it needs to do so at any given time.

For applications like cinema HVAC systems, which can frequently be run at reduced loads, this can translate to substantial energy savings. VSDs obey the square-cube law, so a small reduction in motor speed equates to an even larger reduction in energy use. In practice this means that a motor running at 80 percent speed will consume just 50 percent of the energy that it would require if it were running at full power, potentially saving thousands of pounds over the course of a year.

Click here to find out more about how variable-speed drives can help to ensure comfort whilst saving energy and lowering your energy bills.

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