BACKUP POWER

CHOOSING A BACKUP POWER SYSTEM FOR USE DURING POWER OUTAGES

There are several options when choosing a backup power system ranging from power generators (petrol or diesel), typical U.P.S (Uninterruptible Power Supplies), alternative energy equipment (e.g. wind and/or solar power) and inverter/charger/battery combination systems similar to a UPS but with extended backup time and faster chargers. Each of these has its pros and cons and your specific application and needs shall determine the type of system that you will be using.  

Before purchasing a backup system you should consider the following facts. Backup systems and batteries are expensive and every appliance that you choose to run on the backup system which is not absolutely necessary can increase the cost of the backup system drastically.

We therefore recommend that you carefully consider which appliances should run on the backup system after a power failure. For example: A normal household fridge that is without power for 2 to 3 hours will have no negative effect whilst the temperature for a vaccine freezer could be critical. A roof fan not running could be uncomfortable whilst an oxygen generator failing could be a matter of life and death. A water feature not working will have much less impact than a security fence not working.

 For a power backup application we suggest a battery bank together with a combination inverter/charger/changeover unit: When mains power is available the unit acts as a charger thus charging the battery bank. During a power outage the unit acts as an inverter converting the stored battery power to normal 230 Volt AC power. In cases of extended power failures this system can be further backed up with a generator.

HOW TO COPE WITH ESKOM LOAD SHEDDING IN SOUTH AFRICA

It seems that load shedding has become the rule rather than the exception in South Africa since the end of 2007 for reasons we will not mention here. Let's rather look beyond the causes and discuss the solutions. It seems that the load shedding program (at least) tries to limit load shedding to periods between 2 and 3 hours and in the worst cases 4 hours at a time although changes of schedule surprise you ever so often.

GENERATOR OR INVERTER/UPS BACKUP FOR YOUR HOME?

The first question is normally whether one should go for a generator or a battery powered inverter/UPS backup system.  We are of the opinion that a battery backup system is the most appropriate system for short period power cuts (load shedding) and generator assistance in addition to the battery backup for extended power cuts for the following reasons:

A battery backup (inverter) system does not need any human intervention when a power cut occurs. The system will automatically start to operate within a split second whereas with a small power generator there will be human intervention needed to start the generator and operate a changeover switch (unless the generator is equipped with electric start and an automatic mains failure panel which is fairly costly). Nobody likes the noise and fumes from a power generator and nobody wants to go outside at night to go and start a small power generator.

P.S. Commercial and industrial needs will be discussed in separate leaflets:  

DETERMINING THE SIZE OF A BACKUP POWER SUPPLY

To size a system we would need to know how much backup time is needed, and the average and peak power consumption requirements during this time.

The typical middle-class home could need uninterrupted power for the following:

LIGHTING: a Few lights (preferably low energy compact fluorescents or LED lights)

SECURITY Intercom, gate or garage door motors and security system (otherwise you could be stranded outside your premises and unless you have a UPS or an automatic start mains failure backup generator).

ENTERTAINMENT: Entertainment e.g. TV or radio

COMMUNICATION: Power for PC and telephones

REFRIGERATION: Probably only needed for critical applications or when extended power failures occur. Most refrigerators and freezers keep cold enough for several hours.

COOKING, HEATING: This should preferably be done on LP Gas or from a backup power generator as a battery system for such heavy loads will be very costly.

For such a basic power backup application we suggest a battery bank together with an inverter/charger/changeover unit: When mains power is available the unit acts as a charger thus charging the battery bank. During a power outage the unit acts as an inverter converting the stored battery power to normal 230 Volt AC power.

The generator however also has a place in cases of extended power failures (lasting for days) as a generator can backup this system further and also supply power to fridges, and other appliances. If the power supply situation in SA collapses completely a backup power generator will indeed be needed to supply continuous power. The main advantage of also having a UPS is that you will not have to run the generator 24 hours a day.

SOLAR and/or WIND POWER AS A BACKUP SOURCE OF ELECTRICITY.....?

Using solar power as a back-up source for grid electricity outages is questionable - generally it would be poor use of a relatively costly investment. Depending on the frequency of power failures, the solar power generator would mostly idle in the sun, waiting for a power failure before it kicks in. If money and commercial payback is not important you are free to do it and it will decrease your carbon footprint.

Do you want to “GET RID OF THE GRID”?

There are indeed people doing this, but in most cases they are doing it for environmental reasons which are indeed commendable. The cost of electricity in South Africa is relatively very low compared to world standards and as a result we have not been very energy conscious when selecting appliances and lights and in general we are not very conscious about switching off lights or using power carefully.

Unfortunately solar electricity is not subsidized in South Africa as yet. If you have the money and you "want to get rid of the grid" there are several things to consider.

Firstly you will have to make a careful analysis of your current power consumption determining the main loads, critical loads and areas where you can certainly save on consumption. You will have to be prepared to go into an energy efficiency exercise and adapt your lifestyle accordingly. Please take the time to read the section about off-grid living on our website.

The main power consuming appliances in any household is normally the ones generating heat with specific reference to hot water geysers, stoves and tumble dryers. Here one should definitely consider solar water heating, LP Gas stoves and either natural drying or making use of LP Gas tumble dryers to save on consumption.

Whatever you do, please make your own contribution to minimize your impact on the lovely planet that we inhabit (but which we are at the same time making uninhabitable). Get into the habit of saving electricity and all other natural resources – start now – change your light bulbs to energy saving ones or LED lights, fit a solar water geyser, install a hot water geyser timer, make use of passive lighting, heating and cooling, switch off unnecessary appliances.

Summary: (How to handle load shedding in SA)

Determine your needs, make a decision, get a suitable battery inverter/UPS back up system, get a LP gas stove, use power wisely, adapt, get on with your life, work hard and help to save our country from an economic disaster. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Copyright 2007 OMNISOLAR | info@omnisolar.co.za