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Plumbing & Construction

Specialist in , Domestic, Commercial, Industrial
Plumbing & Maintenance

Solar radiation in South Africa

South Africa has one of the highest levels of solar radiation in the world

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Solar radiation is radiant energy emitted by the sun as a result of its nuclear fusion reaction. For the purpose of Solar Water Heaters .

We are only intrested in the solar radiation that falls on earths surface. South Africa has one of the highest levels of solar radiation in the world , the solar radiation of South Africa ranges from around 1450kwh/m2 to about 1950kwh/m2.

  • Harnessing energy from the sun to heat water is nothing new. Solar water heaters have been commercially available from the early 1800's. However, today's solar water heaters have a different appearance to those of the past, they are more effective and they are an environmentally sound way to reduce energy bills.
  • Solar energy can meet part all of a home's domestic hot water needs. 
  • Solar water heaters come in a variety of configurations. Each differs in design, cost, performance, and level of complexity. Most systems have back-up water heating such as electricity or gas. A solar water heating system consist of a hot water storage tank, a solar collector that absorbs solar energy, and a back-up energy source.
  • The heating up of a geyser accounts for a good chunk of a homes energy use, on average about 40% - 60% of your electricity account is contributed to your geyser.

Internal workings of
solar water geysers

Solar water geysers rely on warm water rising, better known as convection. This is how water circulates through the panels. Convection happens when the water stored in the panels heats up and rises into the water tank above, or in the ceiling – depending on where you decide to install it. The hot water in the tank then moves into the cylinder, usually located inside the house.

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Meanwhile, the cooler water in the tanks flows downwards into the absorber (collector). These actions create circulation. If the solar geyser is in the ceiling and at a lower level than the panels outside on the roof, then convection will not take place and a circulating pump is required to circulate the water between the tank and panels .

Types of solar power 
available

Solar Electric power which uses photovoltaic cells to convert solar radiation into electricity, the greater the intensity of the sunlight , the greater the flow of electricity.
Solar Thermal energy where the sun's energy is used to heat water. Solar thermal energy is a relatively simple process where water is pumped into solar panels, heated and then stored in a tank ready for use.

Pros of using a 
solar powered geyser

  • After intial installation cost, they provide a free source of energy.
  • They produce energy quietly.
  • Solar energy systems are long lasting and virtually maintenance free.
  • Can be installed on many rooftops.
  • Reduce the carbon footprint of fossil fuels by means of natural energy.

Cons of using a
solar powered geyser

  • Higher initial cost compared to non-renewable electric supply.
  • The efficiency of the system also relies on the location of the sun.

Economic Benefits of Solar Water Heating Systems


The first step is figuring out how much hot water you use.
Most of your hot water is probably used when showering or bathing in the morning.

1

Evaluation of Household hot water usage

Evaluation of the data showed that daily household hot water usage for a typical household of four persons was 239 liters, although with strong seasonal variation: 171 liters per day in summer against 249 liters in winter. 
239 Litres of water is the same as 239 kilograms of water.

2

Hot water is 70 degrees, and cold water is around 15 degrees – so whe want to heat it up by 55 degrees

3

The calculations goes: 239 x 55 x 4.2 = 55.209 Kilojoules of energy

4

We normally see energy in our electricity meter and bill as kilowatt hours, rather than kilojoules, so we have to divide by 3,600 (the number of seconds in an hour) to convert them — so 55.209 Kilojoules is 15.335 kilowatt-hours (55209 ÷ 3600 = 15.335).

5

So basically they wil use 15.335 electricity credits every day heating up water. But your geyser uses more energy than that, it has to keep the water hot for when you need it. That’s what we are going to work out next.

How much energy does my geyser use without me ?

If you have a 200L tank that is category E your geyser uses 3.0kWh per day, just keeping itself warm – regardless of whether they use ANY hot water. If you don’t have an energy rating on your geyser, it’s probably pretty low down.

Very old ones and ones stored outside will be much worse even than these figures – but to be on the safe side, just assume they are category G — e.g. so if you have an old 200L geyser, it probably uses a little more 4.1kwh/per day staying hot.

In our senario we wil use a category E (200 liter)-->3.0 kwh/per day.


Lets Combine the numbers

1

To work out how much your geyser uses you need to just add the two numbers
                                                       that we’ve worked out:

15.335 kwh/day for actual hot water + 3.0 kwh/day for keeping it hot = 18.335kwh/day

2

So looking at a month, we need to multiple by the number of days – 18.335 x 30 days = 550.05 kwh/month

3

And finally to convert that to Rand, we need to multiply by the cost per unit of electricity. At R1,425 per unit we multiply with our total Kwh/per month : R1,425x550.05kwh/ per month = R783.821 per month 

Save money and get your solar geyser today

Why Choose a solar geyser

1

Eskom and Loadshedding

When it comes to resources, we lack water and, if problems at Eskom worsen again, perhaps electricity. But one thing we’re not short of is sunshine, which is why solar energy is such a sustainable alternative to what Eskom provides.

2

Electricity is expensive , Sunlight is FREE.

Electricity is more expensive, but the reality is we need to be working far better with all resources.

3

why pay for electricity when  you can generate warm water for FREE

It makes absolutely no financial sense to keep paying for a resource like electricity that you can in fact generate for yourself with an asset that adds tremendous value to your property, hedges your costs for the next 20 to 25 years and will save you a massive amount of money over the cumulative lifespan of your solar investment

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