Solar Power for Dummies Part 3: The panels

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Now that we have calculated our power needs and know exactly the Wattage rating of the Solar system we need it is time to build it; or if you decide to chicken out, find someone to do it for you.

Those still struggling with the budget should know that most electrical devices come with a tag (usually at the back) which has the power details, if there isn’t one you might want to try the device manual.

The first component of any Solar system is the Panels, it is the panels that put the word Solar in the whole project. As we have already said Solar Panels generate electricity when they are exposed to light.

A solar panel is usually made up of cells that are joined together to form the entire unit. Most solar systems operate in the 12 volt rating although 24 volt configurations are not uncommon. For the purposes of this guide, we will be creating a 12V system so make sure that your panel is made for this rating.

Most panels come with a package that says “for use with 12V batteries”. This does not mean that they output 12V, for example, 180W panels typically have a voltage of  45V.

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Types of Solar Panels

Like with hard drives, not all panels are the same. There are three basic types of solar panels.

Monocrystalline panels which cost a fortune, are the most efficient in converting light to electricity or so they say and last longer, Polycrystalline panels these are the most common and affordable panels that you see selling at the Gulf Complex. We will assume that you are using these. The average cost per Watt for these is $1-$0.75. Below is a cost at typical retail prices for Polycrystalline Solar Panels for use with 12V in the capital.

WattsPrice
100$100
150$110
180$140
250$200
400$350
800$600

For the best prices when buying at the Gulf Complex just ask to be directed to “The Suppliers.” These are usually cheaper than the ordinary vendors who sell inside.

The third type of panels is called Amorphous panels I don’t know anything about these.

Mounting

Solar panels are typically mounted on the roof depending on where you live. Where I come from, Epworth, they would be gone (stolen) long before you climb down the ladder as you come from mounting them. You might want to solicit the services of a roofer when mounting these.

Generally since Zimbabwe is in the Southern Hemisphere you panels should face the North. (equator from whence the sun comes) There is some math involved in determining the tilt angle of the panels but if there are facing North and not under some shadow or shade for most of the day you should be fine. The panels will charge, to varying degrees depending

The panels will charge, to varying degrees depending on the angle of the sun, from sunrise to sunset. You can always find the exact times for sunset and sunrise using Google e.g sunrise Harare will tell you when the sun will rise and sunset Harare when the sun will set in Harare on any given day.

It is always preferable, however, to mount your panels to a movable ground rack which you can easily adjust to follow the sun and obtain the maximum charge as pictured below. You can also take the panel in at night for security. This is my preferred method.

 

A movable rack with a Poly-crystalline panel.

Image via EnergyMatters.

Solar radiation

Much of the energy (Hello Einstein) on earth is obtained from the sun. The amount of sunshine affects the amount of energy that your system is going to get with the maximum charge obtained at summer noons when there are clear skies and zero charge during the night.

There are other things like cloudy weather and the inherent inefficiencies within the panels themselves that will affect the efficiency of your system. You should know that the amount of Kilowatt hours that your system receives is limited by sunshine ( Solar Radiation) which is the amount of Kilowatts per square metre in any given area.

In the previous installment, we created a budget which showed precisely the amount of Kilowatt hours you will need keep this handy we will use the Kilowatt unit more in the coming installments.

Buying the panels

As already said, you will be best advised to treble the amount of watts you need in order to deal with such things as cloudy weather, nights and unexpected demand. Using our example, you will have to purchase panels with a total rating of 750 watts panels. You will have to make the personal decision of whether to buy a single 750 watts panel or a number of panels whose total wattage is 750 watts.

I would recommend buying 3X250 watt panels as they are easier to handle with our adjustable mount and if you break one of them your whole system would be ruined.

NB If you decided to go for the adjustable mount, just consult a local welder with a picture of the design above and they should be able to make one for you without burning a hole in your pocket. Overall if you are building a 750 watt system you should expect to spend about $600-$700 on the panels and the mount.

19 Comments

  1. kuda says:

    why are you writing and publishing this half baked article research on the Amorphous panels and write another article please

  2. Garikai Dzoma says:

    Kkkkkk! I make it a point never to tell a lie Kuda 😉 I dont know a thing about these type of Panels and if you recall from part 1 of the series I expressly said I was not going to bore people to death with Science. I have never seen these types of panels or used them so I cannot in good conscience write about them. If you know about them please feel free to make a long comment with the necessary info. I would appriciate that. From the little I could Google. you dont want to know about these Amorphous panels.

    1. Jonah says:

      Amorphous panels are great for high temperature climates like Zimbabwe because their open circuit voltage does not change with temperature as much as poly- and mono- silicon panels do. In technical terms, amorphous panels have a lower open circuit voltage temperature coefficients. When the ambient temperature is high, the voltage across your panel terminals decreases in an approximately linear fashion. That is often counter-intuitive to most people, but that is the reality. High temperatures are not good for PV electronics (including inverters, combiner boxes, etc). Your system performs best when it is sunny and cool !

      In addition, manufacturing amorphous panels is cheaper than manufacturing poly- and mono-crystalline silicon. I have some Indian solar engineering colleagues who sing praises of amorphous panels in their hot regions. I would love to write an article about amorphous panels if people are interested.

      Garikai, I have been following your solar articles closely; I am fascinated by the fact that many people are showing interests. Myself, I have been in the solar industry (outside Zim) for a few years now.

      Learning the science of solar PV is probably the easier part, safety and good workmanship significantly contribute to the success of a solar PV project. Not all local solar PV installers/electricians have those two. I recommend everyone who tries to install their own system to exercise caution and good judgement. Poorly installed rooftop (or any other installation) solar PV can result in electrical fires, electrocutions, damage of other electrical components, loss of efficiency and money. Consider referring to recognized safety standards such as the American National Electric Code, IEC , or local safety standards.

      1. Garikai Dzoma says:

        Thanx for the information mate.

  3. joey k says:

    Garikai what is the general efficiency rating of ‘gulf’ panels. what are the brand names of these panels. I fear in Zimbabwe cross border traders with interest in a quick buck and not quality may take advantage and dump poor quality panels in Zimbabwe.

    1. Jonah says:

      Most commercially available panels are 15% efficient on average. Amorphous are less than 15% but more than 10%. Low efficiency just means you need a larger area to generate the same amount of power, if you have plenty of area or roofspace, then you ought not to worry too much about efficiency.

      Besides, the higher the efficiency, the more expensive panels get. No need to get high efficiency panels unless you are constrained on space.

    2. Garikai Dzoma says:

      I always make it a point to buy SA made or Ecco branded panels.

    3. Itai SolarSky says:

      As I commented in one of Garikai’s articles it is easy to be fooled at the solar marketplace. The sticker rating on the panel is usually higher than the actual size. This is done by vendors as well as the manufacturers to make the panel appear cheaper.

      My advice: Buy from a proper shop and get a warranty, no regrets.

  4. Maki says:

    “Overall if you are building a 750 watt system you should expect to spend about $600-$700 on the panels and the mount. ”
    And this investment will last for how long before a replacement of a component or what not is required?
    Just need to know so as to compare with ZESA. Sorry i did not read the other articles.

    1. Jonah says:

      I agree with Garikai. Anywhere from 10 years; 25 years is expected lifetime of good solar panels. You are most likely to replace your inverter after about 10 – 15 years. You should make sure you choose tested and proven solar panels: California Energy Initiative certifies solar modules for use in California and compiles an extensive database of modules that meet minimum quality standards : http://www.gosolarcalifornia.org/equipment/pv_modules.php.

      They do the same for inverters, but the inverters are designed for different voltages and frequencies from what we use in Zimbabwe. Good inverters should be at least tested to international standards such as IEEE 1547, IEC 62109, EN 50530, or any other credible standard. Good charge controllers can be tested to IEC 62509, or any other credible standard. Modules to UL 1703, IEC 61646, IEC 61215 or any other credible standard. Stickers on the solar product should have such information. If you don’t see any testing/certification info on the solar products downtown, you may want to reconsider buying them.

    2. Gweja says:

      In 1996 my father installed a solar system at our rural home. Its still working to this date, with many many batteries later! The panels are still going strong.

    3. Itai SolarSky says:

      I will have to disagree with the price part.

      That budget is for a 150W system. A battery based solar power system should cost you at least $5 per watt. The smaller it is the more it will cost per watt.

  5. Garikai Dzoma says:

    Panels have a nominal lifespan of 10 years. This depends on how careful you use them, the brand etc.

    1. Joey.K says:

      Garikai- Did you guys manage to attend the recent laucnh of a new Solar battery range by (Chloride Exide)ART Corpotation? I wanted to know the specs of the new battery range.

    2. Danie says:

      I tend to disagree Garikai, I have a Solarcomm 35W photovoltaic module that was bought way back in 1994, it is still working it’s able to deliever it’s rated 2.35A short circuit current though the open circuit voltage dropped slightly from 21.5 to 20V. Btw it’s a polycrystalline module. Anybody looking for a good panel should desist from buying those Gulf Complex junkies,

    3. Danie says:

      Oh I think I missed the word “nominal” lol, you’re right Garikai, but that depends on the model n quality,

    4. Danie says:

      How easy it is to embarass….

  6. Joey.K says:

    Interesting story in the Herald today about Gvt wanting to regulate solar product imports in conjunction with Standards Association of Zimbabwe. Long overdue- I have noticed over the years many people have lost faith in Solar due to poor products on sale downtown (batteries/panels/Inverters/ charge controllers). Mostly lack of knowledge- how to “size systems and battery packs correctly” and very very poor “Deep Cycle Batteries” with questionable depths of discharge causing expedited degradation of electrodes . Hopefully people will now have accesss to dependable solar products and some basic education of using the systems.

  7. Danie says:

    Oh I think I missed the word “nominal” lol, you’re right Garikai, but that depends on the model n quality,

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