Understanding the benefits of solar power

July 31st, 2014, Published in Articles: EngineerIT

 

Using solar energy would be a logical route for us to follow in an effort to alleviate the energy shortage. But we don’t. There are several good reasons why South Africans are reticent, amongst them being the cost of installation, lack of a clear understanding about what is available and, the fact that feeding power back into the grid is not permitted by Eskom.

There are many myths around solar energy, as well as confusion between solar water heaters with solar panels which harness the sun to charge batteries or supply the house or office; and that all solar panel are the same.

There are three different type of solar panels on the market, each with its own characteristics :

  • Monocrystalline silicon solar cells, where four sides are cut from cylindrical silicon ingots to make silicon wafers
  • Polycrystalline silicon solar cells manufactured by melting raw silicon and pouring this into a square mould, which is cooled and cut into perfectly square wafers
  • Thin-film CIS (copper, indium and selenium) solar cells.  CIS panels are produced by depositing one or several thin layers of photovoltaic material onto a substrate.

Sinetech, a Randburg-based company of solar system engineers, recently built what is believed to be southern Africa’s first combined solar PV panel and  weather reference station. Three types of solar panel arrays have been  installed on the flat rooftop entertainment area of the company’s three-storey premises, each capable of delivering  3 kW. The arrays will be used to generate real-time, objective solar PV panel data, in combination with weather data, specific to South Africa but of benefit to global audiences.

Solar, the way to go to reduce the energy crisis. •Polycrystalline Silicon Solar  cells  and Monocrystalline Silicon Solar cells , panel on Sinetech's roof.

Solar, the way to go to reduce the energy crisis.  Polycrystalline silicon solar cells and monocrystalline silicon solar cells panel on Sinetech’s roof.

“I was determined to create a source of reliable solar panel  data,”  Sinetech GM Herbert Teubner told EngineerIT.  “However the benefits of the reference station go beyond just facts and figures – the centre will also be used to provide training on solar system setups to the trade and public and the practical limitations and uses of the products. It will also enable Sinetech to generate its own power for in-house use.

“We use sophisticated computer programs to calculate and design the most efficient and advanced solar systems. I believe that a solar system must be designed to perform for at least 25 years and that can only be realised if  high quality and products best  suited for each installation are installed,” said Teubner..

At Sinetech each array generates a total of 3 kW of power. The mono and poly arrays each use 12 x 250 W panels to achieve this output, while the CIS array requires 20 x 150 W units to achieve the same capacity.

“We no longer need to rely on manufacturers’ specifications; instead we can confirm panel performance first-hand at our own reference site. For instance, CIS panels claim an 8 -10% efficiency improvement over crystalline panels due to a ‘soaking’ effect. We will be able to put these claims to a real-time test.,” said Teubner.

“I hope the promised 8 – 10% energy increase  from the CIS panels will prove correct, as they are less expensive to manufacture and would provide a tempting cost-saving for those customers who have the space. Our first test results looking promising.”

Each array, the poly, mono and thin film, uses the same type of high-quality inverter and  max power point (MPP) tracker, providing clear and measurable performance indicators for those studying the data. The panels are held in place by mounting brackets that do not require roof penetration, thus eliminating the possibility of a leak due to solar mounts. The rooftop installation provides uninterrupted exposure to all elements at all hours of the day – the perfect environment for these types of comparisons.

The arrays are connected to a variety of diagnostic instruments and communications software that collect and display data in real time. A similar set-up exists for the weather station, where Sinetech is able to measure conditions such as ambient temperature, temperatures of the individual panels in each array, solar irradiance, humidity, wind speed and direction, and more.

Herbert Teubner pictured in the   Solar PV Panel and Weather Reference Station with research facility at Sinetech

Herbert Teubner in the solar PV panel and weather reference station at Sinetech.

“All this data will be able to be viewed on the premises -thanks to cutting edge diagnostics and instrumentation – as well as over the internet. The practical experience of constructing thee 3 kW systems and one smaller  solar PV array in one installation will prove to be an invaluable teaching tool for future students of the Sinetech Institute of Technology, due to open later this year, as well as those studying renewable energy at a tertiary level,” Teubner said.

When selecting which type of solar panel is best suited for an application, there are many other factors to consider in the decision to go solar. Some of the main ones include:

  • A standalone system to provide power in areas where no utility power is available either permanent or only on weekends such for instance  on a  game farm or holiday retreat
  • A back-up system to cover load shedding periods to take over the total load or just some essential systems.
  • Once Eskom will allow power to be fed back into the grid, there are several options to consider:
  • A solar system that feeds power back in the grid  to build up credits
  •  A solar system to run the entire operation off solar and feed back into the grid any access energy generated.

That a battery is a battery is another myth. Batteries are designed for specific purposes, both in terms of the technology used, the load to be connected and longevity.  A car battery typically lasts about two years (curiously, the guarantee is also only between one and two years.) Choosing the right battery for the job is essential. The initial outlay may be a little more but if calculated over the operational period it is always more economical.

The  other myth is that anyone who can put a plug onto a kettle cord  can plan and install a solar system. It requires more that an electrician’s licence. Having an electrician’s ticket is a good start but much more training (more specific)  is needed. And doing it yourself is not recommended.  Solar systems involve working with direct current (DC) which could start a fire and is more lethal if touched by accident than  AC.   Just a simple loose connection in the output from the array could start a fire.

Undoubtedly solar is the way to go, but use experienced people and plan for a system that will give service for many, many years with  a low maintenance cost.

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