﻿Conditioned to performThe performance of today’s most advanced air-conditioning systems extends far beyond just comfort heating and cooling. John Durbin reviews the wider benefits of air conditioning and takes an in-depth look at the higher levels of comfort and air quality offered by the latest technological innovations.
Indoor-air-quality control entails a great deal more than merely heating and cooling, as traditionally provided by standard air-conditioning systems and heat pumps. To maintain the higher levels of air quality expected in today’s working and public environments, a certain level of humidification, filtration and ventilation is necessary. The bonus is that these capabilities can now be delivered by some heating and cooling systems as a by-product of other air-conditioning functions.
For example, in cooling mode, air-conditioning systems remove moisture from the air, making life more comfortable for a building’s occupants. It is important to get the right relationship between temperature and humidity because while a relative humidity of 50% at a temperature of 22°C will make a room feel warm, a relative humidity of 20% at 28°C could actually leave occupants feeling cold. The correct level of humidity not only improves room comfort but can also have a health impact, as overly dry air may make people more vulnerable to pollution in the air, including viruses and bacteria.
Ventilation is another important consideration for the comfort of building users. While today’s residences and buildings are better insulated than ever, this limits the exchange of outdoor air with indoor air. As a result, the air we breathe indoors can be even more polluted than outdoor air. Moreover, we commonly spend up to 90% of our time in indoor environments, so the impact of air quality within our living and working spaces should not be underestimated.
Heat-reclaim-ventilation (HRV) systems can help create a high quality environment by interlocking with the air-conditioning system. Recovering energy from the exhaust air reduces the cooling/heating load on the air conditioning system, while offering all the health benefits of clean, odour and pollutant free air. Heat reclamation, ventilation and filtration systems can also provide a certain amount of free-cooling in summer, when outside temperatures are below indoor requirements.
Take, for example the Daikin HRV system, which recovers energy lost through ventilation and minimises room-temperature changes caused by the ventilation, thereby maintaining an environment with clean air maintained at a comfortable temperature.
The HRV system interlocks with Daikin’s VRV system, Sky Air and other air-conditioning systems and automatically switches over to ventilation mode, further increasing the effects of energy conservation. For these air-conditioning systems, HRV operation has been centralised on the remote control, which provides a simple configuration offering total control over air conditioning and ventilation.
This is just one of many potential solutions for any building services engineer or manager to consider. A variety of heat-recovery-ventilation solutions are now available, which can optimise the balance between indoor and outdoor temperature and humidity, thus maximising efficiency for offices, hotels, stores and other commercial buildings. However, there are certain features that are well worth looking out for when selecting a system.
For example, models with a DX (direct-expansion) coil and/or humidifier can help to prevent the direct impact of cold airflow on individuals during the heating cycle. The use of the high-efficiency paper (HEP) element and the optimised design of the fan and airflow passages mean that a typical 28% reduction in the air conditioning load can be achieved compared with normal ventilation fans, while still offering a compact format which can fit easily into limited spaces such as ceiling voids.
On Daikin HRV systems, this average 28% reduction in air conditioning load is achieved by operating the system in total heat exchange mode, which achieves an initial 20% reduction in energy usage. A further 6% reduction is achieved by auto-ventilation mode changeover switching, and a further 2% in energy saving is delivered via pre-cool, pre-heat control (this reduces air-conditioning load by not running the air-conditioning system whilst the air is still clean, immediately after the air conditioner is switched on).
Night-time free-cooling operation is another energy conserving function available if connected to multi or VRV/VRF systems. It operates, as you would expect, at night when the air conditioning is switched off. By ventilating rooms containing heat-emitting office equipment, night purge reduces the cooling load when air conditioning is switched on again in the morning.
Given the ever greater pressure to not only increase energy efficiency, but also demonstrate a swift return on investment and deliver higher performance levels, the new breed of heat-recovery air-conditioning systems literally deliver ‘something for nothing’ — offering an elegant and effective solution to meet the multiple requirements for internal air quality control.
John Durbin is manager of Daikin UK’s engineering department