Techniques to improve HVAC energy efficiency
The article offers a brief overview of a combination of air conditioning technologies that are currently available and may provide efficient answers for thermal comfort and energy conservation. Additionally, it analyses various techniques and technologies and illustrates how they might enhance HVAC system efficiency and cut down on energy use.
Researchers have been forced to concentrate on the problem of energy use in buildings while preserving essential thermal comfort due to rising standards of living combined with diminishing sources of fossil fuels. The HVAC systems are among the biggest energy consumers in buildings and are crucial to guaranteeing occupant comfort. Therefore, performance upgrades for conventional HVAC systems present an exciting chance for significant reductions in building energy use. The maintenance of indoor thermal comfort conditions in commercial buildings accounts for around 41% of the total energy demand for structures.In addition, since most people spend more than 80% of their time inside buildings, creating energy-efficient HVAC systems that don't rely on fossil fuels will be essential to cutting down on energy use. Figure 1 illustrates observable values from a closer examination of the energy consumption of HVAC equipment on a global scale.
Energy consumption has significantly increased as a result of the growing reliance on HVAC systems in residential, commercial, and industrial settings, especially during the summer when ambient conditions were extreme. It is crucial to create HVAC systems that are energy-efficient in order to safeguard consumers from rising power costs as well as the environment from the harmful effects of greenhouse gas emissions brought on by the use of electrical equipment that waste energy. There are a number of ways to produce energy-efficient HVAC systems today, which can demonstrate that they are more energy-efficient than traditional standard systems as illustrated in Figure 2.
However, a thorough comprehension of the comfort conditions in the structure is required in order to construct effective methods. Human happiness with their thermal environment is the foundation of thermal comfort. The ASHRAE standard 55-2004 should be followed when designing and calculating air conditioning systems to control the temperature environment while simultaneously achieving an acceptable level of indoor air quality. When 78% of the building's occupants are content, thermal comfort levels are considered to be adequate by this benchmark. An index known as an is used to forecast suitable thermal comfort conditions.
The predicted mean vote (PMV), which represents the average vote for a large group of people on a standard scale, is employed. Air temperature, air humidity, air velocity, mean radiant temperature, garment insulation, and human activity are the six thermal variables for an indoor environment that determine PMV.
HVAC energy-saving techniques
To increase the energy efficiency of HVAC systems and lessen their environmental impact, many strategies must be used. Various automatic control and optimization techniques have been applied in recent years to reduce the energy consumption rates of these systems.
HVAC installations that use little energy
By enhancing a building's heating, ventilation, and air conditioning (HVAC) system and updating it with energy-efficient technologies, significant energy savings can be made while enhancing building security. More than any other form of equipment, HVAC systems are misused in both the household and commercial sectors. HVACs have a significant role in the energy demand for the built environment within buildings due to inadequate maintenance, a lack of information about how to operate them effectively, excessive use, and the prevalence of obsolete and inefficient systems.
cooling duty
Reducing the cooling load is crucial for HVAC system energy savings. The cooling load—or how much heat the system must remove—determines how much power air conditioning systems utilise. The cooling burden can be reduced in numerous ways.
Make the cooled area insulated.
This entails putting in place a number of measures, including door sweeps, window glass, shades, and awnings. All of these factors will combine to produce a thermally effective shell that can significantly lessen the cooling burden on HVAC systems while preserving cosy interior temperatures. When HVAC systems are operating, keep windows and doors closed to reduce warm air filtering into the chilled interior.
Reduce your use of lighting and appliances.
All lights produce heat, therefore switching off any lights or equipment that is not in use should assist lower the cooling load. Heat load can be decreased by switching from normal boilers to condensing boilers, and heat output can be decreased by switching from standard motors to high-efficiency motors. Lower energy consumption and heat load are achieved by investing in variable speed drives (VSDs) for motors to match speed with output requirements.
Make sure that the HVAC is operating in accordance with demand and that controls are in place.
Throughout the day, a building's HVAC loads change at different times and in different locations. Systems should only be used when and when necessary during regular business hours, according to well-established time and occupancy constraints. Additionally, it's important to routinely verify settings because short-term alterations are sometimes forgotten and lead to many systems being configured wrongly. The HVAC system can be automatically controlled by installing a building energy management system (BEMS or BMS), which provides detailed control and monitoring of building services performance, including HVAC. By enabling system performance to be tracked and settings to be modified, BEMS can save energy expenditures.
HVAC fans and pumps have variable-speed drives.
As demonstrated in Figure 3, this enables motor-driven loads like fans and pumps to function in reaction to changing load requirements rather of only operating in on/off mode, which can save about 30% of annual energy. The VSD will also come with energy-saving soft start and soft stop algorithms that will ease component stress.
Fans save a lot more energy than other pieces of equipment. The energy needed for fan loads varies as the cube of the fan speed, therefore the slower the fan spins, the less energy is needed. A fan using 80% of its maximum power will use 50% less energy than one using 100%. More components than merely speed controls and variable speed drives can be found in modern fan controls.
Understanding the system's operating cycle in contrast to the actual heating and cooling needs is essential to assessing the energy savings potential of VSDs in HVAC systems. The majority of HVAC systems are built to keep a building warm on cold days and cool on hot days. Therefore, those days are the only ones when the HVAC system needs to run at maximum capacity. The HVAC system can run at a reduced capacity the remainder of the year. In order to match airflow to actual heating and cooling demands, a variable air volume system with variable speed drives, also known as variable frequency drives or VFDs, can be employed. When full flow is not necessary, the VSD can lower the motor speed, lowering the power.and the amount of electricity used.
adjustable air system volume
While the variable air volume system is superior to the constant air volume method, there are a number of issues with the basic design. In a system with variable air volume, the air temperature is maintained while the flow is changed to accommodate the demands of the heat load. A constant speed fan and a damper are used as the fundamental control mechanisms to manage airflow. Due of this, the fan motor operates at a consistent load regardless of the airflow rate. As seen in Figure 4, using a variable speed drive changes the load on the fan motor in response to changes in airspeed and results in energy savings.
Optimization of the central plant and energy-efficient operation
Complex arrangements of several components, all of which need to be monitored for proper operation, make up HVAC systems. Each system in a manually managed system is set to its ideal state, which may not be ideal for the system as a whole. Consider the air handling unit, for instance. The rate of airflow and the rate of water flow are the two flows that can be managed. The evaporator settings, which also affect the compressor and condenser settings, will determine the temperature of the water. To maximise efficiency, the optimization will include adjusting how each of these units operates.Every component of the HVAC system must be optimised in order to reduce energy consumption. It is possible to optimise the system's overall performance to make sure
even after the individual items have been configured for optimum economy, there will still be energy savings. After improvements to the machinery and motor drives, central plant optimization can yield even greater advantages. When compared to the current plant before equipment and VSD retrofits, savings of up to 60% are asserted. According to claims, savings of between 15 and 20 percent are feasible when compared to performance with renovations alone.
Any brand of machinery or plant that can communicate with building management protocols can be used with Comfort Point Open (CPO) systems. The majority of work is done using proven proprietary algorithms and techniques. When there are many chiller plants operating in larger buildings and different regions of the building's heat load follow diverse patterns that are unrelated to one another, CPO is crucial.
using an integrated hybrid cooling system with evaporative cooling
The proven integrated hybrid cooling system for evaporative cooling (EC) has low setup and operating expenses. Image 3. For the purpose of saving energy, a comparison between continuous drive and variable speed drive. Figure 4 shows how optidrive control reduces power usage. energy efficiency to considerably increase a building's ability to cool and ventilate while using the least amount of energy possible. One can avoid using ozone-depleting hydro-chlorofluorocarbons and chlorofluorocarbons by using water as the working fluid. Other advantages of this system include avoiding CO2 and other emissions as well as simple installation, maintenance, and operation.The lowest temperature that DEC systems can achieve is the outside air's wet-bulb temperature. Evaporative cooling integrated hybrid air conditioning systems can offer thermal comfort by converting sensible heat to latent heat (desiccant cooling system). As a result, the supply air's temperature after cooling would be just below comfortable and may increase by a few degrees as it travelled across space, pushing the temperature above comfortable levels. Therefore, the goal is to look at the potential for enhancing the evaporative cooling system's utilisation capacity by combining it with other components, as well as the potential for improving the performance of other HVAC systems when integrated with an evaporative cooling system.
Refrigerant Variable Units
In conventional systems, a single evaporator and condensing unit work together to supply conditioned air to a single section of a building. Zone controls and ductwork must be added if the system is to supply air to more than one location. Although this setup functions, it is not the most adaptable or energy-efficient, and building tenants frequently grumble about it.
VRF systems provide a different option. In these systems, pipes connect a solitary outside condensing unit to numerous inside fan coil units. A two-pipe or three-pipe system is used to circulate refrigerant throughout the system. All fan coil units or zones in two-pipe systems must be in the heating or cooling mode. Three-pipe systems have the capacity to heat some zones while cooling others at the same time. An inverter-driven motor is employed to power the compressor since the load on the system's compressor constantly changes depending on the total of the zone loads. The inverter lowers the frequency of power to the motor as zone loads drop, lowering the compressor's speed and refrigerant flow. As the compressor's speed decreases,The amount of energy used has significantly decreased. The system's refrigerant metering equipment is unique to each fan coil unit that is linked to it, and it is controlled by the fan coil's control system. The metering device controls the flow of refrigerant required to fulfil each specific load when the load in that space varies. There are more benefits to VRF systems than lower energy consumption. Better climate control is supplied to all areas thanks to the capability to provide individual zone temperature management as well as simultaneous heating and cooling. These systems require less installation area than regular continuous flow systems since they only need a single outdoor condensing unit.
using HVAC systems that are grounded
Technology for ground-coupled cooling or heating depends on the fact that the Earth's interior maintains a generally constant temperature that is colder in the summer and warmer in the winter. In this system's undercooling mode, operating heat is discharged to a ground loop, which acts as a heat sink with a temperature lower than the temperature of the surrounding air. Heat is taken from a source that is hotter than the outside air during winter heating operations. Different home and business scales have adopted this method.
Thermal storage systems are employed.
To avoid paying peak demand fees, thermal storage systems (TSS) transfer HVAC system energy use from on-peak to off-peak times. To save energy, TSS can also rate the difference between energy supply and demand. In this system, energy for cooling is often stored at low temperatures below 20 degrees Celsius, and energy for heating is typically stored at high temperatures above 20 degrees Celsius. TSS is a widely utilised technology that, when compared to conventional HVAC systems, offers a number of benefits for heating and cooling systems, including energy and capital cost savings, system operation improvements, system capacity extending, and equipment size reduction.
building behavior's impact
The performance and operational parameters of an HVAC system as well as the features of the heating and cooling demand as well as the thermodynamic behaviour of a building all affect how much energy the system uses. Due to building behaviour, the HVAC system's actual load is typically lower than that for which it was intended. Therefore, proper control of the heating and cooling demand is crucial for reducing HVAC energy usage in a particular building. Significant energy savings in a building's cooling plant can be achieved by controlling the cooling load of the structure as a whole, including solar radiation, illumination, and fresh air.Better design solutions that match a building's demand with its HVAC system capability are thought to be able to save about 70% of energy.
Conclusion
New configurations of conventional systems that make better use of already-existing components are crucial to the development of energy-efficient HVAC system designs. Designing HVAC system configurations that incorporate a variety of various conventional HVAC system components has proven to be an efficient strategy to achieve energy efficiency. A mix of currently available air conditioning technologies can provide efficient solutions for energy conservation and thermal comfort, according to recent research and development. Each HVAC discipline has unique design specifications and offers chances to save energy. But it's important to realise that alterations to one setup could increase or decrease savings in another.
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