Energy-efficient heating, ventilation and air conditioning (HVAC)

Principle

You have probably observed that heating and air conditioning are the two biggest consumers of energy in your hotel. What you probably do not know is that the motors for the fans, compressors and pumps in your HVAC equipment are responsible for much of your electricity consumption, because they always operate at full capacity.
But these motors do not need to operate at full capacity at all times. Energy efficiency solutions such as variable frequency drives are available, to adapt motor speed to actual needs at your hotel, which will help lower electricity consumption for your HVAC equipment.
Regulating motor speed is an effective way to economise electricity.

Explanations

• Most flow systems (such as pumps, fans and compressors) operate without motor speed controls. In most cases the flow is regulated by valves or air dampers that modify the system's output. The problem with this type of regulation is that the motors continue to run at full speed, while HVAC equipment rarely needs to operate with maximum flow; this leads to electricity being wasted.
• Electronic systems to adjust motor speed can save up to 70% on electricity use, compared to equipment that operates at full capacity at all times. In fact, electricity consumption is proportional to the cube of motor speed!

What sort of equipment is involved?
• This solution can be applied to most HVAC equipment (heating, ventilation and air conditioning). For example, water circulation pumps in hot water heaters can be equipped with a variable speed motor.

Variable speed drives are used to adjust motor speed
• Most electric motors used in air conditioning and hydraulic applications are asynchronous motors. To regulate the speed of these motors the frequency of the alternating current power supply must be modified. Variable frequency drives are electronic devices that can progressively adjust the speed of these motors.
Other advantages of variable speed drives
• Variable frequency drives are generally equipped with regulation devices, which will contribute to overall system regulation. In addition, they can help protect other system components.
• Mechanical overload and pressure spikes that occur with non-regulated motors are avoided, prolonging system life.

General observations:
• Before deciding to install a variable frequency drive, it is best to ask a HVAC equipment manufacturer to evaluate the energy savings that might be achieved with a variable frequency drive in your system, as the savings vary from one installation to another.
• More broadly, the possibilities for installing variable frequency drives on motors in your HVAC equipment will depend on the configuration of your system. Given the complexity of this evaluation, we recommend that you consult an equipment manufacturer or a qualified HVAC installer.
Can all existing equipment operate with variable frequency drives?
• Some equipment may not run with a variable frequency drive, or only after changing the motor. For this reason we recommend that you consult an equipment manufacturer or qualified HVAC installer before making a decision.

Implementation

0

Costs

Approximate cost:
• Varies according to equipment to be modified.
Approximate payback time:
• 1 to 4 years.
It should be noted that costs and payback times are highly dependent on the local setting and the initial situation of the hotel.

Examples

0

Benefits

Cost reduction
Adjusting motor speed can save up to 70% on electricity use, compared to equipment that is not regulated.
The energy savings achieved will considerably prolong the life of a pump or fan.
• Considering the life cycle of a pump or fan, it can be remarked that the purchase price represents: about 5% of overall life cycle cost, maintenance about 5%, and energy consumption about 90% !
Energy savings will also greatly reduce overall life cycle cost for a pump or fan.

Reduced CO2 emissions
• For a hotel of 1,000 m² that uses 15 kWh/m² of electricity for HVAC equipment motors annually, and applying emission factors for France, a 50% savings in energy consumption represents:
0.63 t CO2 eq of avoided emissions each year
Emission factors for electricity in France: 84.3 g CO2 / kWh.
Emission factors for natural gas in France: 331 g CO2 / kWh (Source: ADEME).

Constraints

Implementation:
• Ease of implementation: Moderate (**).
• Best time for implementation: when air conditioning equipment is renewed, or when motors are replaced.
• Relevant initial situation: the motors that drive fans, pumps and air conditioning systems run at full capacity at all times, and are not regulated according to demand.