While many businesses, homeowners and public establishments look to save electricity usage and increase their security of power supply, it is critical that they consider their unique needs before deciding on new elements of power supply.
This is according to Nick Oosthuizen, MD of Inframid and a consultant in energy efficiency, who highlights the importance of understanding your electrical load before investing in new power supply systems.
“Schools are a clear example of why you cannot take a one-size-fits-all approach in efforts to secure your power and save energy. School loads are not only seasonal but also vary throughout the weeks and days,” says Oosthuizen.
He recommends that you undertake an in-depth financial feasibility study that weighs up all elements of power supply in relation to the prevention of downtime and assuring return on investment.
“The first step is to conduct an ‘electrical audit’ and understand your current electrical load, which will help to identify the real needs for special supply systems and avoid fruitless expenditure. It is thus important to know your electrical demand, load content, and electrical distribution architecture.”
To assist in understanding your electrical load needs, Oosthuizen explains that there are at least five different segments to consider: essential loads, critical no-break loads, non-essential loads, energy inefficient loads, and your total load profile over time.
It is fundamental to determine these different load categories you are dealing with, firstly so that the different types of power supply systems can be applied appropriately, secondly to avoid over-sized and therefore over-priced systems, and thirdly so that the potential for load reduction and renewable energy can be considered all with the view to achieve acceptable return on investment (ROI).
Essential loads
The essential load is made up of electrical systems that are fundamental to help the school remain operational, and to keep safety and security systems going.
These essential loads require reliable backup power supply sources in order to maintain the electricity supply under mains fail conditions for as long as needed.
For schools, these normally include classroom lighting, educational sports facilities, power points for educational systems, offices, learning and admin computer systems, printers, projectors, essential water pumps, etcetera.
Critical no-break loads
No-break loads are those elements of the essential load that need seamless power transfer and cannot tolerate even a split-second unplanned break in power supply when switching from utility supply to backup power. In a school, seamless transfer is needed in areas such as administration and classroom computing systems where valuable information will be lost if power supply is interrupted.
“These no-break loads require uninterrupted power supply, UPS, systems when the main power supply fails,” says Oosthuizen. As these UPS systems are normally battery and sometimes solar supported and very costly, it is important to know exactly what size the no-break loads are and how long they will need to be supplied by the UPS systems.
Non-essential loads
“Non-essential loads include those systems for which you don’t need backup in any form. It is the part of your load that the school can do without while remaining operational during mains fail conditions. An example of this might be geysers, heaters, air-conditioners, pool heating, and pool pumps, which are not essential for running a school.”
However, if you lose your utility supply for long periods, the situation might change, as will the definitions of the non-essential loads.
Inefficient energy loads
According to Oosthuizen, inefficient energy loads include electrical elements which can be replaced by energy-efficient alternatives to make the load less bearing. “This lends itself to energy saving in day-to-day operations. For example, all new geysers must comply with the new minimum standard as set by the Department of Energy, namely Class B, as specified in SANS 151, to ensure less pressure on your electrical load,” he explains.
In schools, the replacement of air conditioners and electric heaters with the latest state-of-the-art low energy and unity power factor technology will have quite an impact on energy consumption. Changing older light fittings to the newest technology LED fittings will also have a significant impact on energy usage. Water and sewage pumps are other considerations. In general, pumps have a very low power factor, which means they draw higher current than necessary.
“Where schools have many pumping systems, it is worth considering power factor correction to these loads to increase the power factor, which will decrease the reactive power with various cost benefits, such as lower demand charges, avoiding reactive power penalties and freeing up distribution system capacity” advises Oosthuizen.
Load Profile
“When determining your school’s power supply needs, some forethought can go a long way in ensuring appropriate systems,” says Oosthuizen. “You should determine your total load profile for at least a year, bearing in mind that school loads are seasonal and are changing from day to day. When determining your load, don’t only use utility account information – this normally only provides monthly maximum demand where applicable and energy usage.
Additionally, it is important to understand which parts of your load can be moved to non-operational times, such as after 15h00, when total consumption is less. There are many timer and automation technologies on the market that can help with load shifting in order to spread the usage curve,” says Oosthuizen.
“Investing in an alternative power supply system for your school is a good idea, but for it to be a feasible investment you must clearly understand your load requirements before making any decisions. Knowing what you have is the critical first step to knowing what you need next. Analysing this resultant need for alternative power supply solutions against your potential loss of business, loss of information and energy savings forms the essence of your business case for investment” concludes Oosthuizen.