COOLNOMIX® takes advantage of the spare capacity designed into most air-conditioning installations. It uses two additional temperature sensors to determine when it can give the compressor a break, delivering savings in the 15-40% range.
Air-con Basic – Understanding The Vapour Compression Cycle
Commercial air-conditioning systems operate according to the vapour-compression cycle.
In a typical air conditioner, the outdoor unit consists of the compressor, the condenser (a radiator) and a fan, while the indoor unit consists of the evaporator (another radiator), the expansion valve and a fan (as illustrated).
The circulating refrigerant enters the compressor as a vapour, where it is compressed and thus heated. As this superheated vapour enters the outdoor condenser, heat is expelled with the assistance of a fan and the cooled vapour condenses into a liquid.
The liquid refrigerant then travels to the indoor unit, passing through the expansion valve before entering the evaporator.
By passing through the valve, the liquid refrigerant goes from a high-pressure to a low-pressure environment, causing flash evaporation and auto-cooling, resulting in a mixture of liquid and vapour. This mixture is then completely vaporised (boiled) in the evaporator by absorbing heat from the room air blown across the evaporator coil by a fan. The fully vaporised refrigerant then returns to the compressor completing the cycle.
Essentially, heat is absorbed indoors by the evaporator and expelled outdoors by the condenser. The compressor does the vast majority of the work and consequently utilises the vast majority of the energy (up to 95%).
The Problem Is The Crude Thermostat
Over the past few decades, advances in compressor technology (inverters, digital scrolls etc.) and refrigerants have significantly improved the efficiency of air-conditioning.
However, the control components of the system, the thermostat, has remained fairly static in its approach, applying a relatively crude control logic: if the temperature is more than 1°C above the set point go ON, if the temperature is more than 1°C below the set point go OFF.
This 1-2°C gap is necessary to avoid repetitive short-cycling of the compressor, which would otherwise cause damage.
The thermostat typically has a single sensor and may run the compressor for extended periods of time, with total disregard for what is happening inside the unit. It ignores, for example, whether spare refrigerant is available to boil in the evaporator. The compressor simply continues to run until the OFF temperature is reached.
The Savings Are Hiding In The Aircon’s Excess Capacity
A particular air conditioners’ capacity is designed to ensure it can cope satisfactorily on the hottest days, during which it may work continuously.
In these conditions, the refrigerant boils quickly in the evaporator, and the compressor just manages to keep up with demand.
In cooler times there is spare capacity, and the compressor supplies refrigerant at a faster rate than the evaporator can boil. It is during those times that COOLNOMIX® extracts savings.
How COOLNOMIX®’s ORS™ Extracts These Savings
COOLNOMIX®’s secret weapon is ORS™, which stands for Optimized Refrigerant Supply. It is an internationally patented advanced control methodology, where two additional temperature sensors and an algorithmic energy optimisation control system work together to monitor the thermodynamic (room temperature) and the hydraulic (refrigerant supply) performance of the air conditioning system to improve compressor efficiency.
In operation, ORS™ first evaluates the room temperature to ensure that the desired set-point has been achieved. It then ensures the room temperature remains within 0.5°C of that set-point. The second sensor connected to the supply air then allows ORS™ to determine whether sufficient liquid refrigerant is available, and to use this information to optimise the compressor run time.
It Optimises How The Compressor Runs
If you think of your bike pump, essentially a manual compressor, it is easier to pump when the tyre is almost flat, or in other terms, it is most efficient when working against an unpressurised vessel.
The same is true for an air-conditioning compressor, it is most efficient when working against an unpressurised condenser, and conversely least efficient when working against a highly pressurised condenser.
Additionally, refrigerant condenses more quickly the cooler the condenser, and conversely more slowly in a hot condenser.
When COOLNOMIX® stops the compressor, the pressure on both sides eventually equalises as the liquid refrigerant passes through to the evaporator and boils, and at the same time, the condenser coils have a chance to cool down. So when the compressor restarts, it works against less pressure and the condenser is cooler, making the whole process more efficient.
COOLNOMIX® exploits this spare capacity, effectively achieving the same thermodynamic work with less mechanical work, or the same cooling using less electricity.
COOLNOMIX®: The Third Generation
There are other “compressor optimisation” technologies on the market, some more successful than others.
First generation products saved energy by attempting, through timers or other means, to reduce the compressor ON time by arriving at an ‘Optimal’ mark-space ratio between compressor ON and OFF times. These devices have no concept of a temperature setpoint and only deliver savings under medium load and medium humidity conditions but hit problems with temperature stability under more demanding circumstances. First generation products include Sm—ool. Sm—ool, which has no temperature sensors intercepts the thermostat signal to the compressor and injects averaging delays that have built up over a period of time.
Second generation products attempted to satisfy set point objectives, but with limited timer based and/or single temperature sensor resources. Examples here include an upmarket version of Sm—ool and another product called Airco–ver which had temperature settings but was still restricted through use of a single temperature sensor.
COOLNOMIX is a third generation energy saving technology as it makes use a 2 temperature sensors and has algorithms that are optimized to each of the 16 temperature settings within.
+ But Is It Really Unique?
The obvious question that springs to mind is “why isn’t every air conditioner doing this already?”. There is a two part answer to that question.
The first part is market driven. Commercial air-conditioners must be able to interface with a range of third party controllers, BMS and/or thermostats, and generally do not integrate dynamic control features – they bring the muscle not the brain.
The second part of the answer is that it just isn’t that simple. COOLNOMIX® is a third generation product, and while others have tried to improve efficiency by using compressor cycling or PID controls, none before COOLNOMIX® have used a dynamic two sensor method.
COOLNOMIX®’s algorithmic energy optimisation control system delivers:
- Unrivalled energy-savings, resulting in significant financial and environmental benefits;
- Improved temperature stability and comfort assurance;
- Reduced dripping and no icing up of evaporator.