Developments in HVAC systems are occurring at many levels. This article examines a number of new developments contributing to a higher standard of air quality.
Air cleanliness will become increasingly important, with more emphasis on controlling dust, bacteria, odours and toxic gases. This is combined with a greater focus on energy efficiency.
For example, there are multiple component innovations packaged into advanced rooftop air conditioners which deliver energy savings of about 17 per cent.
But while they may deliver good efficiency at full load, there is poor efficiency at part load where they most often operate.
Increasingly, rooftop packaged air conditioners incorporate advanced features that improve part load efficiency including better variable speed fans, inverter controls to vary output, evaporative pre-cooling of the condenser unit and diagnostics using
advanced sensors.
Thermal energy storage technologies store heat or cold for use during later applications.
Active solar thermal systems use free solar radiation (available in Australia for a large portion of the year) to reduce peak demand.
Active solar thermal systems store solar radiation by heating a fluid in a collector.
In space heating and cooling applications, the heat is transferred indirectly via a heat exchanger. In other applications, the hot fluid may be used directly.
Active solar thermal systems do not require any energy infrastructure, and generate low or no carbon emissions.
Computer technologies will continue to enhance HVAC system efficiency, reliability and intelligent control, as well as assisting with integration into other building services.
Intelligent controls enable post-failure diagnostics and can pinpoint predictive diagnostics and maintenance advice regarding sensor and calibration errors, fouling of sensors, faulty or poor wiring, and misaligned actuators and valves.
Many advances in commercial building automation and HVAC control will come from clean room controls.
UV treatment
Emerging research is indicating that UV treatment of return air can deliver a high standard of air quality while reducing the dependence on outdoor air supply.
This technology also reduces fouling of fans and heat exchangers, improving their efficiency.
Other emerging developments include modulating HVAC compressors.
Modulating (inverter drive) compressors vary their output to better match the load preventing frequent cycling while increasing part-load efficiency.
They can reduce energy consumption by about 20 per cent and help to deliver better humidity control due to regular air flow, especially when variable speed air handlers are also used.
The Cromer cycle is a combination of a desiccant wheel and a vapour compression air conditioner.
In humid climates, Cromer cycle HVAC units can better match cooling loads, especially part loads, and reduce the need for reheating. They can reduce energy consumption by up to 30 per cent and allow smaller capacity cooling equipment to be used.
Substantial amounts of energy are required to treat very hot, humid or cold outdoor air.
Energy recovery ventilation systems, most commonly heat and energy recovery wheels, exchange heat between the exhaust air and the supply outdoor air.
They can lower energy consumption by about 10 per cent and reduce the required unit capacity.
Although this energy saving is modest compared to other technologies, energy recovery ventilation reduces peak loads. Some systems now evaporatively cool the exhaust air from the building and use this cooled air in the heat exchanger.
Air conditioners mix outdoor air with recirculated indoor air. Economy cooling uses more outdoor air when cooling is required and the outside air is cooler than the return air. The systems can reduce energy consumption by about 16 per cent.
This system can be used at night to blow cool air through a building to charge the thermal mass in a process called mechanical night purge.
Source: Energy Efficiency Exchange www.eex.gov.au, a joint initiative of federal, state and territory governments.