Post-pandemic, HVAC is empowering smart buildings and protecting occupants’ health
Since the outbreak of the novel coronavirus three years ago, pandemic control has gradually transitioned from the initial passive response to a more systematic and proactive approach. Governments, enterprises and individuals have also actively adopted a variety of new technologies and innovative methods to maintain people's health and allow life as we know it to continue. The most direct and effective method is to smartify buildings so that they can become "personal" health guards.
People most often associate smart buildings with functions for improving the comfort and efficiency of occupants and users, along with energy conservation and environmental protection. Ironically, one thing that is often overlooked is arguably the most basic and necessary – a healthy, safe and intelligent heating, ventilation and air conditioning (HVAC) system.
The Importance of HVAC systems
To date, many cases and studies have confirmed that viruses (including novel coronaviruses) may be transmitted through aerosols under certain conditions, such as in coronavirus patient wards or in densely populated places with high viral concentrations.
At the risk of sounding alarmist, here are some examples:
- Back in early 2020, in the early days of the outbreak, the cruise ship Diamond Princess, departing from Japan, suffered a large-scale infection of 700 people due to poor management and failure to turn off the old central air conditioner in time. A number of infection incidents on cruise ships followed. Although related to the confined living space and high density of passengers on cruise ships, the lack of smart HVAC systems was also a major factor in facilitating these outbreaks.
- In the early days of the outbreak, Chinese volunteers went to Hubei to support the fight against the pandemic. When the local hotel industry in Wuhan voluntarily provided free rest spots for medical staff, it also specifically emphasized that the hotel should not turn on its central air conditioning.
Although there is no conclusive scientific data to indicate that the novel coronavirus is transmitted through air-conditioning systems, hotels, offices, shopping malls, schools, health and beauty facilities have nonetheless been advised to take precautionary measures to optimize the design and building of HVAC systems in order to minimize the risk of facilitating outbreaks in the future.
Introduction to HVAC Systems
Obviously, the HVAC system is one of the key features of smart buildings that play a vital role in maintaining the health of residents and users. So, let’s see what exactly constitutes an HVAC system.
I. Basic components of the HVAC system
The main subsystems of the HVAC system are heating, ventilation, and air-conditioning systems.
The heating system consists mainly of hot water heating and steam heating. In buildings, the more popular method is hot water heating – that is, the use of hot water to exchange heat with the secondary heat exchanger to maintain a certain indoor temperature.
Ventilation refers to the process of bringing in fresh air to, and removing stale air from, an indoor space. The main purpose of ventilation is to ensure indoor air quality. Proper ventilation can also reduce the temperature of indoor spaces. Ventilation includes both natural ventilation and mechanical (forced) ventilation.
An air-conditioning system is a combination of various components, the purpose of which is to “condition” the air inside a building with the objective of achieving set conditions. Its basic function is to condition the air sent into the building to eliminate residual heat and humidity from the space, so that the temperature and humidity can be kept within a range acceptable to the human body.
II. Classification and description of HVAC systems
- Classification by purpose
Air conditioners for comfort require the ability to achieve a temperature conducive to a comfortable environment, and generally do not have exceedingly strict requirements on the adjustment accuracy for temperature and humidity settings. They are typically used in housing, offices, theaters, shopping malls, gymnasiums, automobiles, ships and airplanes.
Technical air conditioners, on the other hand, require adjustment accuracy for temperature and humidity settings, as well as higher requirements for air cleanliness. They are used in electronic device production workshops, precision instrument production workshops, computer rooms and biological laboratories.
- Classification by equipment type and location
Centralized (central) air conditioning concentrates the air processing equipment in a central air-conditioning room, from which treated air is sent through ventilation ducts to each room. It is suitable for use in buildings with large areas, concentrated rooms, and relatively close heat and humidity loads in each room, such as shopping malls, supermarkets, restaurants, ships and factories. Maintenance and management of the system is convenient, and noise and vibration isolation of the equipment is relatively easy to manage. The downside is that the energy consumption of fans and pumps in the transmission and distribution systems of central air-conditioning systems is relatively high.
Semi-centralized air conditioning describes an air-conditioning system that has both central air conditioning and air processing units at each terminal point. This system is more complicated than centralized air conditioning and can achieve greater accuracy in the adjustment of temperature and humidity settings. It is suitable for public buildings such as hotels and office buildings, with rooms that require separate adjustment. The energy consumption of the transmission and distribution systems of semi-centralized air conditioners is usually lower than that of centralized air-conditioning systems.
Local air conditioners feature air conditioning units in each room to process the air. Air-conditioning units can be installed directly in or adjacent to rooms to condition air locally. They are suitable for venues with small areas, scattered rooms, and large differences in heat and humidity loads, such as offices, computer rooms, and homes. The equipment can comprise a single independent air-conditioning unit or a system comprising fan coil units (FCU) that supply hot or cold water in a centralized fashion. Temperature can be adjusted for each room as required.
- Classification according to load-bearing medium
Full air systems deliver only hot and cold air to the conditioned area through ducting. In a typical full air system, fresh air and return air are mixed and processed through a refrigeration coil before being sent indoors to heat or cool the room.
In full water systems, the room load is borne by the centralized supply of cold and hot water. The chilled water produced by the central unit is sent to the coil (also called the terminal unit or fan coil) in the air processing unit, for indoor air conditioning.
In an air-water system, the load of the air-conditioned room is borne by the centrally processed air. Other loads enter the air-conditioned room via the medium of water, and the air is reprocessed.
Finally, in a direct evaporative unit system – also known as a refrigerant air conditioning system, the load of the air-conditioned room is directly borne by the refrigerant, and the evaporator (or condenser) of the refrigeration system directly absorbs (or releases) heat from the air-conditioned room to control the air and temperature of the room.
Development Trends in HVAC Systems
As the environment changes and technology advances, the HVAC industry is strengthening "connectivity" to become more energy-efficient and environmentally friendly, thus making buildings smarter.
- The more connected the smarter
Almost all new buildings today are extensively equipped with smart meters, thermostats and sensors. These smart connected devices allow people to easily control the temperature, humidity, and air quality in buildings while reducing energy costs. As technologies advance, HVAC will acquire sensors capable of "talking". These systems will be able to track outdoor conditions, such as temperature, humidity, brightness, and even the position of the sun, and based on those conditions, automatically adjust its setting to attain and maintain preset conditions indoors.
As it advances, HVAC software will be able to collect data and compile it in reports to identify usage trends, system status, and past performance. These reports can then be used to prescribe preventive maintenance and accurately pinpoint sources of failure to expedite repairs. Some modern software-backed HVAC systems can already self-diagnose, allowing HVAC technicians to fix problems quickly and minimize downtime.
- More environmentally friendly, more energy-saving, and greener
Energy-efficient HVAC systems and equipment are gaining traction as people become more environmentally conscious, embracing the use of solar panels and wind turbines to reduce energy costs. At the same time, the use of geothermal heating and cooling methods has also increased, with some buildings combining natural gas and solar energy to allow owners to seamlessly switch between the two to control electricity costs. The use of energy-efficient HVAC systems and equipment has effectively reduced demand for electricity, thereby making the HVAC system and the entire building not only smarter but greener.
