Feature
answer is because no matter if you are looking at a new building , a retrofit , or a refurbishment , the fact remains that according to various global studies , commercial and industrial operations require the greatest proportion of energy a country produces ( in some countries this is up to 80 % of overall production ), and of this , up to half of that demand can be allocated to HVACR needs .
In a commercial building setting or a production facility , the HVACR systems have always been designed and set up to manage the ‘ worst case scenario ’ or peak heating and cooling demand – this is the maximum output the system would need to provide when , for example , an office is fully occupied with all of the electronics in operation and at the hottest time of the day .
However peak demand is almost never a lengthy continuous occurrence . This then generally means that systems are designed to manage that demand for only a few hours a day – if even that long . However , during peak demand periods , stress mounts on the electricity supply grid and service providers as everyone needs energy at the same time , and also peak periods carry a premium in terms of costs per kW / hr to customers .
“ The demand charge model is commonly found throughout the world and is essentially a mechanism for service providers to also manage their energy production capabilities . By charging more during these peak demand periods the idea is simply to try and balance the energy grid and incentivise users to either be more efficient , or transfer their peak demands to other times of the day . In some countries , off peak energy rates are five times cheaper than peak demand rates ,” says Chris Elston – Calmac thermal storage engineer at KMS Engineering .
In South Africa , the consumer of the energy , no matter in what application , is charged a rate according to their peak demand . This is the highest averaged demand measured in kVA during any 30-minute period and within a designated billing cycle . This peak demand charge is an additional charge to consumption and supply costs .
So , for example if energy demand for nine hours of a ten-hour day ( non-peak times ) is 1kW ( 1.25kVA ), but for the other hour the AC systems are on and now the demand increases to 7kW ( 8.75kVA ), the peak demand charge will be based on the higher value – which is significantly more than 1kW for 90 % of the time .
This scenario has created a multitude of innovations over the years because in all reality , efficiency can only take engineered systems so far , and because energy tariffs continue to rise while global warming persists , energy security continues to be a particular challenge here . Adaption and enhancement of existing technology is being sought out now more than ever .
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RACA Journal I April 2021 www . hvacronline . co . za