In January, Daikin McQuay hosted a technical seminar at Dubai Municipality’s City Hall auditorium, titled ‘VRV Systems & Dubai Green Regulations’. The presenters included Michel Farah, Business Development Manager (MEA), Daikin McQuay, Brij Sharma, Consulting Civil Engineer, Daikin McQuay, Firas Kneifati, VRV Product Manager, Daikin McQuay and Kuniyoshi Minato, Consulting Sales, Daikin McQuay. By Valeria Camerino (Inputs from B Surendar)
Farah claimed that the current UAE strategy for green developments aimed at promoting renewable energy, dealing with climate change through the reduction of carbon emissions, and focusing on carbon capturing and storage technologies, generating energy from waste, is in line with the company’s philosophy.
He explained that the building sector has the highest impact on natural resources, followed by transportation and industry.
Indeed, in the US alone, buildings account for 40% of primary energy use, 72% of electricity consumption, 39% of CO2 emissions and 13.6% of potable water consumption.
However, he pointed out, green buildings can reduce energy use by 24-50%, CO2 emissions by 33-39%, water use by 40% and solid waste by 70%.
“Generally speaking, reducing energy usage in buildings starts with architects and the building envelope, while the HVAC engineer will complement the architects’ efforts,” he said adding, “If the best systems in the world are not maintained properly, then they won’t give the performance they have been designed to achieve.”
Farah reiterated that Daikin’s position on sustainability is similar to that held by Dubai Municipality.
The company is keen on embracing the green economy, although in the past, it has been held back by cost barriers, which have been gradually breaking.
On the refrigerants side, the HVACR manufacturer is researching a new refrigerant for high-ambient temperature conditions and low global warming.
Daikin’s eco-friendly innovations include VRV, the first inverter-driven multi system for large commercial applications, Farah claimed.
In the Gulf region, he observed, air conditioning systems are designed for 46°C. The air conditioning is selected for maximum load but it operates under fluctuating part load for most of the time.
Therefore, quickly adjusting refrigerant flow is critical.
In schools for example, Farah explained, high occupancy time is during daytime, whereas the air conditioning does not run at night. Variable needs are also found in residential households.
That’s why seasonality and diversity are two key parameters that need to be considered while designing air conditioning systems.
The air handling unit should, therefore, be selected based on two key criteria: a quick capacity adjustment by changing the load, as well as quick and accurate refrigerant flow control, which can be obtained through an inverter-driven compressor.
As Farah claimed, VRV’s key technology includes:
- Inverter-driven compressor (outdoor unit)
- Motorised expansion valve (indoor unit)
- CPU: Integrated control system
“All three allow quick and flexible capacity control, leading to energy savings and comfort conditions,” he said.
“In some apartments, air conditioning systems are oversized and they stop when the set-point is achieved. But then, the humidity rises, which leads to a feeling of wetness for the room occupants. With VRV, [refrigerant flow] is adjusting in real time.”
Brij Sharma added that VRV can be used for diverse applications, from a one-bedroom apartment to a 100-storey facility, unlike multisplits, which are usually used for residential applications, and chillers for large facilities.
Splits and multisplits account for high power consumption, Sharma claimed. Furthermore, there is no centralised control available.
In addition, they have non-modulating capacity control, because they work on thermostat control.
There are also pipe length limitations, no diversification of loads and low comfort levels.
That results in damp, non-air-conditioned air, once the set point is achieved. Also, they are low on reliability, have high sound levels and high space requirements.
Sharma went on to illustrate chilled water systems’ disadvantages.
In his view, chilled water systems have large system sizes, low part load efficiencies and shared electricity billing, which results in a lower incentive to save.
They also require design expertise, as well as a specialised maintenance team.
Furthermore, the installation time is very long and they are not scalable, which means that adding capacity is a complicated process. “Upgrading systems in the case of existing buildings is complicated,” Sharma said.
He claimed that VRV technology can overcome these challenges, as the systems comes in up to 58 different types and capacity indoor units. A VRV outdoor unit also has inverter-driven scroll compressors and standard scroll compressors.
On the onset of load, the inverter compressor starts first. Once the unit realises there is a minimum of 50% load coming from all indoor units, the standard compressor takes over and beyond 50%, the inverter compressor takes over again. When the unit is started for the first time, it runs at 2 Hz per second and then it goes up to 210 hz per second.
Sharma claimed that VRV systems have excellent performance at part load owing to inverter compressor technology.
Kneifati delivered a presentation on how it was possible to comply with DM green building regulations by using VRV systems with particular regard to the following sections:
- Section 4, Chapter 1.08: Inspection and cleaning of HVAC systems
- Section 4, Chapter 2.01: Thermal comfort
- Section 5, Chapter 2.01: Energy efficiency
Section 4, which concerns building vitality, stresses that the cleanness of HVAC equipment and systems must be maintained.
Kneifati said that, in the case of other equipment, maintenance will need to be provided by an MEP company, whereas, VRV 3 includes a self-cleaning mechanism.
A rotating brush in the cassette will clean the filter every night and store all the dust in a box; and every six months, the dust can be vacuumed away.
This, he claimed, also allows to save power and increase energy efficiency, as it has been proven that on average, energy consumption is 10% higher when the filter is cleaned only once a year.
With regard to thermal comfort regulations, the air conditioning system should be able to maintain comfortable indoor conditions 95% of the time. That is, the temperature should be between 22.5°C and 25.5°C.
With VRV 3, the room temperature can be precisely controlled based on return air temperature (and/or) remote controller temperature sensor, Kneifati pointed out.
Also, the inverter ducted unit feature makes it possible for automatic adjustment of the fan static pressure.
With regard to acoustical comfort, Chapter 403.1 of Section 4 states that low noise levels should be maintained in all different types of buildings.
Kneifati claimed that by using VRV 3 in the Dar El Hadi Hotel in Makkah, indoor unit sound was down to 25 dB, while outdoor unit sound was reduced to 45 dB. The noise level of the extract fan was higher than the noise level of VRV outdoor unit.
Section 5, Chapter 2 of DM green building regulations addresses resource effectiveness.
According to 502.01, energy conservation and efficient building systems, EER for air conditioner greater than or equal to 65,000 Btu/hour at 35°C should be greater than or equal to 9.5.
Kneifati explained that VRV 3 can achieve 14.63 EER at full load (8 HP 100%), compared to 9.5 required by Dubai Municipality, and at part-load (8HP 60%), it can achieve 18.66 EER.
As per Section 5, Chapter 2.01 on energy efficiency, EER for air conditioner greater than or equal to 65,000 Btu/hour at 46°C should be greater than or equal to 6.5.
VRV 3 at full load can achieve an EER of 10.78 and an EER of 13.40 at partial load, he claimed.
As per Section 5, Chapter 2.08 on control systems for HV&AC systems, separate thermostat control should be provided for each cooling zone.
VRV, Kneifati said, has its own individual thermostat, but it can also be connected to infra-red remote control.
Chapter 502.09 sets rules for control systems for hotel rooms. As per this, hotel room air conditioning should be controlled automatically, based on occupancy and window opening. This is possible with VRV 3, he claimed.
With regard to Chapter 503.04 on air conditioning metering, Kneifati pointed out that in district cooling, there are several cases of bill disputes.
He explained that, instead of installing energy meters for each FCU and asking someone to read the meters, with VRV 3, a centralised controller can be used. A digital watt meter will ascertain how much the outdoor unit is consuming.
Furthermore, an Excel sheet will detail out the following information:
- Tenant A: X kWh
- Tenant B: Y kWh
- Tenant C: Z kWh
The expansion valve controls the refrigerant flow for each indoor unit. This provides information on how much refrigerant flow for each indoor unit is going to the outdoor unit and, from there, to the Daikin centralised controller.
Therefore, there is no need to hire someone to read the meter.
Finally, Section 7, Chapter 1.05 of DM green building code states that all refrigerants should be ozone-friendly, with their ODP equalling zero. VRV uses R410A, which is zero ODP. “We therefore comply with the new regulations,” Kneifati said.
|Energy efficiency standards across the GCC
Dubai is not the only area in the Gulf, which has shown significant commitment to reducing energy waste. Other Gulf countries are also paying more attention to this trend. Estidama’s Pearl Rating system, which was launched in Abu Dhabi in April 2010, is also aimed at reducing the negative impact that buildings exert on the environment. Within this context, Qatar has established the Qatar Green Building Council, as well as the Qatar Sustainability Assessment System (QSAS), while the Saudi Authority Standards Organisation is also now actively working towards introducing an energy efficiency labelling system for residential air-conditioners.