ENERGY SAVING EQUIPMENT
Energy efficiency, good for your pockets as well as the environment
By Neil Roberts, senior technical sales manager at Climalife. T
his time last year, energy efficiency was seen as more of an emissions mitigation strategy, with benefits, to help to stave off the impacts of global climate change. Fast forward a year and now energy efficiency is a critical tool to keep down operating costs. It has always been known that refrigeration and air conditioning are large consumers of energy so even modest gains in energy efficiency can deliver significant savings over the lifetime of the equipment. System design and refrigerant choice are major considerations, but there are other actions that can be taken to maintain or improve energy efficiency, reduce total emissions and in most cases, they will even pay for themselves over the lifetime of the equipment.
Maintenance and correct control settings This is probably the easiest strategy to employ but often end users do not see the benefits of spending money on a system that appears to have nothing wrong with it. Simply cleaning the heat exchangers, using reliable gas detection methods, ensuring fans are operating correctly and optimising the system operating parameters can have a significant impact on system emissions. Even moderate fouling of a condenser will lead to an increase in condensing
temperature of the system. Equally if the system has a high/condenser pressure controller, checking the setting is not causing the system to operate at excessively high conditions or is set correctly for the refrigerant used (for example after a retrofit) can have a big impact. Figure 1 shows the impact of increasing condensing temperatures with R-449A at low and medium temperature conditions. Even a very small increase in the condensing temperature can lead to significant decreases in energy efficiency, for example, an increase from 25°C to 27°C condensing temperature can lead to a 5-8% loss of compressor energy efficiency. Pressure increase caused by condenser fouling is easily prevented by regular use of cleaning products such as Frionett® condenser coil cleaner which will prevent build-up of debris that can block the air flow through the coils, maintaining the optimum energy efficiency. In situations where condenser fans have either failed or are malfunctioning, energy efficiencies could easily drop by 25% or more. Systems
which have been
retrofitted and have high pressure controllers can often lose some of the energy efficiency benefits available if the controllers are not correctly adjusted. For example, if a R 404A system is retrofitted to a lower GWP alternative, it is very likely the alternative product has a lower pressure temperature relationship (Table 1). If the pressure controller is not lowered to match the new refrigerant, then the energy efficiency of the system could be 5-10% lower than for the optimum setting.
Refrigerant choice Different refrigerants do have different energy efficiencies when used in the same equipment. In practice there are many potential variables that can affect this, but if it’s thermodynamically proven then it should be possible to achieve improved energy efficiency if the system is set up correctly. Equally using the same refrigerant in both medium temperature and low temperature applications, whilst convenient, may not
22 January 2023 •
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