Newsletter Archive

UPS Power

‘UPS’ stands for ‘uninterruptible power supply’. There are a lot of sizes and varieties of these ‘UPSs’. The economy range are usually an imported product, often designed to provide 15-30 minutes of power if the grid fails. The rationale is that this gives the small office time to shut down their computers. There was also the feeling that the grid would rarely fail and that any such interruptions would be short lived. The inverters used in these ‘economy’ UPSs are often a modified square wave with efficiencies of only 50-70%.

However, some applications need more than 15 minutes back-up. Examples might be medical equipment, communications equipment, computers used as servers or for important functions. In such applications it may be desirable to have several hours or more of back-up power. In this scenario, the size and cost of the battery bank will vary substantially with the efficiency of the inverter.

Inverters used on solar systems are typically around 85% efficient and perhaps as high as 90%. In most UPSs the load still runs off the grid and is switched over in a fraction of a second to the inverter/UPS if the grid fails. With a high quality and high efficiency inverter there are advantages to running the load direct off the inverter. High quality inverters can give better quality power than many grids, as they are less prone to spikes, surges and brownouts.

This type of inverter UPS does of course rely on an efficient automatic battery charger to keep the batteries charged up. The client then has the option of generating some or all of the power from renewable sources such as solar modules or wind generators.

Kerosene Lighting

For those interested in overseas issues, and the health and financial costs of using kerosene lighting, have a look at our FAQ – Developing Country section. ‘Fuel-Based Lighting’ is contributed by an amazing organisation called ‘Light Up The World Foundation’.