As more commercial developments are built and buildings are refurbished to modern standards, there is an increasing demand for energy hungry HVAC (heating, ventilation and air conditioning) systems.
As the UK government looks to future proof the nation’s energy/economic security and be environmentally sustainable, there is, in tandem with this infrastructural growth, an urgent responsibility to reduce the nation’s carbon footprint and energy costs. Decarbonisation and Sustainability is seen as integral to not only environmental care, but also managing the vast demands of energy that new infrastructure and technology requires, and the economic impact created by volatile fuel markets.
With those core goals at the forefront of the UK’s construction industry, how can companies in Mechanical and Electrical building services help? One obvious method is to move HVAC equipment’s power source from fossil energy-based systems to greener energy sources such as wind or solar. To do this requires significant innovation in creating more energy efficient national infrastructure, so that we aren’t demanding more energy than we can create using “cleaner” energy sources.
For a sustainable future, one of the most significant contributions our M&E services can make is to lessen the impact of global warming using new systems that significantly reduce the amount or type of refrigerant gases used in air conditioning and heat pump systems. But why and how?
Innovations in HVAC systems is playing an increasingly important part in reducing worldwide commercial and domestic energy consumption and carbon emissions. Mitsubishi is one company at the forefront of responding to these challenges. Mitsubishi are introducing new HVAC systems that can either reduce the use of refrigerant gases, or even change to a far more environmentally friendly type of refrigerant, such as Hydrofluoroolefin (HFO) type.
In the days before we discovered a hole in the Ozone layer and we realized we were having an effect on the planet our favourite gas was R12( CFC-12). We used it in everything from hairspray to expanding foam and in our air conditioning units. Eventually, we discovered the effect of mixing chlorofluorocarbons (CFC) and hydro chlorofluorocarbons (HCFC) with ozone, resulting in a chemical change breaking down this protective layer which prevented UV radiation from harming humans. This brought the damaging effects of Hydro-Carbons gases to the news headlines, as skin cancers started to be blamed on a depleting Ozone layer. The timeline below shows the speed at which the world responded to this unseen crisis.
1974
In the Journal ‘Nature’, American chemists identify CFC combined with solar radiation decompose in the stratosphere, releasing atoms of chlorine and chlorine monoxide that are individually able to destroy large numbers of ozone molecules.
1978
CFC-based aerosols were banned in the United States, Norway, Sweden, and Canada.
1985
A “hole” in the ozone layer over Antarctica is discovered by the British Antarctic Survey
1987
Montreal Protocol on ‘Substances That Deplete the Ozone Layer’ is introduced.
1987
Robocop first hits the box office (to give you a sense of how long ago this happened!)
1995
Nobel Prize for Chemistry goes to a Dutch chemist Paul Crutzen, plus the two American chemists Rowland and Molina for work on Ozone depletion.
1995
Toy story takes us to “Infinity and beyond”.
1995
COP 1 (Conference of the Parties), the first UN climate change conference is held in Berlin and introduces the banding of Chemicals by their global warming potential GWP.
1996
Scream is released, and has you hiding behind your fingers.
1996
CFCs, HBFCs, carbon tetrachloride, and methyl chloroform are finally phased out.
2066
The Ozone layer should recover and Scream 14 should also be hitting your cinema screen…
Eight years after the 1987 Montreal Protocol, we were all becoming aware of global warming and the effects the industrial age is having on the planet as we emit tons of carbon dioxide into the atmosphere. We learnt how these emissions increase the depth of the natural lay of carbon dioxide that keeps our planet warm from the cold of space (The Greenhouse Effect).
The use of refrigerants was thrust into the spotlight of the world’s media, explaining how very damaging refrigerant gases can be leaked, contributing to the greenhouse effect and climate change. The Australian national government website provides a stark reality:
One kilogram of refrigerant R410a [a commonly used refrigerant)] has the same greenhouse impact as 2 tonnes of carbon dioxide, which is the equivalent of running your car for 6 months.
In an attempt to rectify the climate situation, politicians and scientists held the first UN climate change conference in Berlin in March 1995 and from that changes have taken place, which included the way we measure the effect we use refrigerant gases. The baseline for global warming potential gases is carbon dioxide (CO2), which is said to have a GWP measure of 1. We are making progress as we consider R12 CFC gas has a GWP of 10,900 (the equivalent mass of CO2 with a GWP of 1) and the two most popular refrigerant gases used in air conditioning systems today: R410A, with a GWP of 2,088 and R32, with a GWP of 67.
It's helpful to understand how air conditioning works if to explain further why Mitsubishi’s, and other company’s innovations, are so clever and essential for our industry’s decarbonisation goals, which relies on the reduction of refrigerant gases that have high GWP.
So, how do you keep cool in summer? During the hot summer spells of 1853 there was a solution implemented at St George's Hall, Liverpool: to place a large block of Ice in the ductwork to cool the incoming air! You might wonder where the ice came from. If you’ve watched with your children the opening scene of the Disney movie Frozen (let it go!), you will see Norwegian ice cutters: that’s how and where our ice came from, our earliest air conditioning. But that’s not the answer to today’s needs!
In more recent times innovation has made the chilling process more effective and scalable, and today we use what is known as the Fridge Cycle to produce the cooling. Your refrigerator at home works off this principle and is also the system adopted by air conditioning. There are four main components of modern air cooling, which includes the use of refrigerant gas.
These refrigerant gas air cooling principles are applied to heating technology. Basically, a heat pump is the fridge cycle in reverse, which use refrigerant gases for heating: the advantage is that it takes the ambient air around the unit and converts it to heat. Depending on the outside conditions, the Air Source Heat Pump (ASHPs) can achieve a Coefficient of Performance COPs of 2 to 4, meaning they produce 2 to 4 units of heat for every unit of electricity consumed. The performance drops in extremely cold weather hence the variation in the performance.
You will be aware of the government's drive to push for the installation of heat pumps in domestic setting – the premise being their enhanced energy efficiency, thus reducing dependency on carbon source fossil fuels. These systems work on the principle of taking the heat cycle and warming up a water cylinder which acts like your gas boiler and circulates the hot water heat to the radiators. Part L of the building regulations states that in new houses the heating systems should be designed so it can be retrofitted with a heat pump. This means that the system can only have a maximum design water temperature of 55°C, which is the maximum current temperature of a heat pump. Note that a gas boiler installed 20 years ago would have been designed to operate at around 80°C.
In the system below the DX refrigerant gas temperatures are normally in the region of:
The Client’s dilemma
If we look at choices a client has when it comes to cooling and heating their building, fan coils are often the first option for commercial buildings.
The traditional method for a large building is a centralised plant, with four pipe fan coils serving office spaces. Each fan coil is fed via ‘flow and return’ pipework from a chiller plant and low-temperature hot water flow and return is generated by gas boilers (other fuels are available).
These have several variants, all using refrigerant gas and include:
The DX system installed today use either R410A and R32 gas.
As with most things, there are drawbacks, in particular, R32 gas has a GWP of 67 but is mildly inflammable. You would need to have perfect stoichiometric conditions for it to catch fire and a very badly installed system to start leaking, so some precautions need to be taken into account: Gas leak detection or simply ensure the pipework is in a ventilated space.
Variants of HFO gas has a GWP of between <1 and 2, but is also mildly flammable and therefore has similar inherent safety challenges.
However, one company has developed an innovative Hybrid system to reduce the amount of R32 used, therefore reducing the dangers and also the potential harm to the environment:
Mitsubishi Electrical has developed a system that reduces the amount of refrigerant gas that is used in a system by introducing a Hybrid operation. R32 in the outdoor units feed water-based indoor units. This new system uses 66% less GWP than R410A.
The outdoor unit uses refrigerant gas (R32) pipework to an indoor unit known as a controller and from the controller runs two pipes filled with ‘water’ to room units.
The controller can simultaneously provide heating and cooling to individual room units or Sub-controller to further expand the number of room units.
Ordinarily, a traditional Low-pressure hot water gas-fired heating system and outdoor chillers would supply chilled water to a four-pipe room unit with four pipes running around the building. Compare this to the Hybrid system controller which only uses two pipes for each unit, thus reducing the required volume of R32 refrigerant gas. In turn, Mitsubishi have created a more environmentally friendly system, and is more energy efficient when heating and cooling simultaneous operation occurs.
HFO-R1234yf and other variables have started to be used in Chiller and Heat Pump systems, and have a GWP between just 2 and -1. Until recently, the use of HFO in air conditioning and heat pumps has been limited due to safety concerns over its mildly flammable nature. Such risks are being mitigated by taking the flammable refrigerant outside, making them far safer and more usable in a commercial environment. It’s good news for the environment, for sustainability and our industry that new refrigerants and M&E systems are being developed for a future where damaging greenhouse emissions are being far more limited.
Here at DL M&E, our Mechanical Designers are always looking out for more effective ways to bring environmental sustainability, cost value, safety, and energy efficiency to our projects for our clients’ benefit. We are proud to be Diamond Partners with Mitsubishi, providing a high level of installation service and guarantee for their excellent systems.
DL M&E Building Services Ltd is accredited with REFCOM: Register of Companies Competent to Manage Refrigerants.
