Facilities Management Middle East
VARIABLE FLOW TECHNOLOGY
The importance of Variable Flow Technology in HVAC systems
News of Europe’s increasingly alarming energy crisis, coupled with the prediction that the global demand for energy will increase by another 55% over the next 10 years, has triggered concern around energy security and its environmental impact, with the construction industry being heavily impacted.
As a result, we are witnessing a global shift towards the active reduction of energy consumption - not just for the economic benefits but also for the health of our planet. As sustainability becomes less of an after-thought, and more of a necessity, government entities and private organisations are increasingly implementing measures to support smarter energy consumption. The UAE, for example, has outlined a strategy to reduce their carbon footprint by 70% before 2050, and Saudi Arabia has even gone a step further, announcing plans to reach net-zero emissions by 2060.
In order to make meaningful progress towards these ambitious targets, we must start by addressing the largest contributors to energy demand and carbon emissions.
The most prominent of which is air conditioning, accounting for a staggering 70% of energy usage in cities across the GCC.
Interestingly, for HVAC systems, only 5% of the lifetime carbon footprint can be traced to the manufacturing of components. The remaining 95% stems from energy usage during the operating life of the equipment. Clearly then, improved operational efficiency of HVAC systems offer tremendous potential for reducing overall energy demand.
So the question remains, how can we lower energy demand without compromising on occupant comfort?
One solution is Variable Refrigerant Flow ( VRF) technology, which can be used to separate areas of a building into individually controlled zones, all operating on the same system. Each zone has a programmable thermostat allowing occupants to customise temperature settings based on their preference. The system then supplies the fan coils in the zone with the precise volume of refrigerant required to cool the room to its desired temperature. By varying the flow based on demand, VRF systems run less frequently and at a lower capacity, achieving up to 30% more efficiency than conventional ducted HVAC systems.
A strategic selection of fluids and materials used within the system can also help to lower energy usage. VRF
systems use R- 410A refrigerant as the heat-transfer fluid and working fluid in order to achieve an excellent Energy Efficiency Ratio of between 15 and 20. Additionally, copper is considered the preferred material of choice for pipework due to its characteristically high thermal conductivity and resistance to corrosion. Used to transport refrigerant throughout the VRF system, the pipes are subjected to constant pressure changes. While most untreated metals corrode quickly under such conditions, copper possesses anti- corrosion properties ensuring resistance to pipe cracks, leakages or other reliability issues. By extending the lifespan of HVAC systems, we are able to minimise the building’s carbon footprint and material waste.
In my experience with Conex Bänninger, the use of Pressure Independent Control Valves (PICVs) in hydronic cooling systems can also significantly improve the energy efficiency of HVAC systems. Compatible with variable flow systems where a variable speed pump is used, and constant flow systems where they work to limit the flow in partial load operation, PICVs help to protect against low delta T syndrome and other system failures.
A PICV combines a standard 2-way control valve and a balancing valve. Its two main functions are to control the delivery of chilled water, and to automatically adjust and compensate for pressure fluctuations in the system, maintaining stable and reliable control.
While a standard 2-way control valve can also be used for such applications, these valves are often oversized or undersized in specification, causing system overflows and underflows. This generates excess water to the pump to compensate for their inaccuracy, increasing the pumping cost and energy consumption. PICVs, on the other hand, use dynamic-balancing to alleviate the risk of the aforementioned overflows and underflows. By doing so, they’re able to drastically reduce temperature swings and achieve energy savings of up to 30%, improving occupant comfort and minimising operational costs.
As leaders in innovation, Conex Bänninger’s patented PICVs take things to the next level, described as ‘ three-in- one’ valves with a unique dual flow regulation scale. The regulation scale enables the valve to switch between a low setting for low flow rates, and a high setting for high flow rates at any time - even when the system is running. This additional feature makes it possible to select the required flow rate without needing to replace the valve. By limiting the range of controlled flow, the dual scale allows the valve to adjust the flow with greater precision.
The highly accurate performance of PICVs in partial load conditions ensures that the temperature difference between the supply and return water - the delta T - remains consistent. When the flow rate in the system is not controlled, low delta T syndrome (an inadequate temperature difference between the supply and return water) forces the system to work harder to achieve the desired ambient temperature. In doing so, the HVAC system costs more money and wastes more energy. By maintaining the pressure difference, the PICV stabilises the flow rate in accordance with the thermal load requirements.
If we are to meet carbon reduction targets within the timelines put forward by climate experts, the pace of progress must increase, requiring action from stakeholders in all industry sectors. Consultants must do more to put forward mechanical system designs that take into consideration ASHRAE 90.1 guidelines, and green building applications to promote a sustainable culture in the region.
VRF systems and PICVs are just two of many ways in which we can lower the energy demand of HVAC systems while simultaneously improving performance and occupant comfort. The result? Substantial operational savings for building owners and lower maintenance costs.