Demystifying Going Green

Many times I have friends and associates come to me and express the wish to go green. Going green in my country, Nigeria is hardly a choice people make because they want to save the environment or save the cost of paying the electric bill.

It is something done because most have stayed without power for days, weeks and sometimes months. Indeed I had once stayed six months without electricity from the public supply. The story behind it will make a book. But that will be for another day.

There are options for the enthusiast and would-be alternative energy person who is tired of the use of fossil fuel.

You can decide to harness the energy of the wind, the water (hydroelectric), biomass, geothermal, hydrogen, nuclear energy, biofuel, and the sun (solar energy).

If you reside in the tropics, especially for people in Nigeria which is near the equator, at your disposal is the most significant amount of sunshine.

This is evident when you take a look at the map of the world showing the solar irradiance or solar exposure. It shows the quantity of solar power which falls over a specified unit area.

Looking at the map, you will see the Global Horizontal Irradiance (GHI) or the amount of sun which hits a horizontal surface, which is of particular interest for solar panel installation, is high in Africa.

The value of the GHI in Nigeria ranges between 3.5 kWh/m² (146 W/m²) to 7.5 kWh/m² (312 W/m²) between the coastal and semi-arid regions. Of course, the semi-arid region of Nigeria (Northern part) has more insolation.

On the average, Nigeria experience an average of 5.5kWh/m² daily (229 W/m² per day) of solar radiation with a mean estimated sunlight hours of six hours per day.

The land area of Nigeria is 923,768 km², assuming we have a 1% coverage of the area with solar panels, we will be able to harvest as much as 1854.46 x 10³ Giga-watt hour (GWh).

The average generation per day for the last quarter of the year 2017 in Nigeria was 94,627 MWh or 94.63 GWh. This value of production at best translates to 34,538 GWh or 34.538 x 10 ³ Gwh.

This result invariably implies that if 1% of the total area of Nigeria has solar modules, it will yield more than 50 times or 5000% the current electricity production.

Some may already know this, and that makes solar energy a very viable source of alternative power generation.

The question now is what to do.

Many that are new or want to try the alternative energy most of the time start off on the wrong foot; they want to power things that will make for a costly system.

Let me quickly make a recap of what a solar energy system usually require.

1. The Solar Modules/Arrays/ Panels: These are the photovoltaic cells that transform the energy from the Sun to direct current electricity. This direct current is either used to power equipment directly or first converted to alternating current.

2. The Deep Cycle Batteries: Most times the energy produced from the sun is not used directly/ immediately. There is the need for a place where it can be stored. To store that energy, a special type of battery, which is different from the conventional lead-acid starter batteries used in our vehicles and motorcycles, is required. They are designed to be deeply discharged and can supply energy for a longer duration.

3. The Inverter System: The inverter job is to convert the direct current from the photovoltaic panel or batteries to alternating current. The output of the inverter feeds the house or whatever needs the alternating electric current.
   There are many types of inverters which I won't delve into as it is outside the scope of the article.

4. The Solar Charge Controller: The energy from the Sun fluctuates. Just as the name implies, the device controls the DC charge current from the DC to the batteries. It ensures there is no energy is lost due to feedback to the solar modules at night. It regulates the charge current ensuring batteries are charged at the optimum rate to avoid overcharging and insufficient charge from being delivered to the battery.

Now let us jump in into the best part of the article. You have made up your mind that you want to give the renewable energy a try. First, you will have to consider what you want to power.

Whenever I ask people what they will like to the solar energy pack to power I often hear electric heaters, cookers, six air conditioners, eight freezers and ten televisions. It's not bad that you want to power that. It can be powered by the solar energy but at a tremendous cost!

The rule of the game is to power only the very low watt or energy consuming devices. Unless of course, you have a bottomless pocket or you are a Bill Gate or Warren Buffett.

It is always better to strive to acquire low energy device than to try to get a system that supports an energy guzzler.

For instance, a one horsepower air conditioner is approximately 750W.

Let us take a look at the cost of the batteries (I will ignore the cost of the inverter, solar panels and charge controller in this assumption) needed in the solar energy system that will handle that.

Let us assume you bought a 12v 200AH deep cycle battery at the cost of ₦80,000 ($220) each. Four of it will come to ₦320,000 ($880).

To calculate the number of hours that it will stay when powering one horsepower air-condition we will use this formula below.

Backup Time = (Battery capacity x 12V x N x Efficiency of the battery) / Load (watts)

12V= voltage of the battery
N= number of batteries in the system
Efficiency= 70% ( I usually assume a lesser value of efficiency for a more accurate estimate, but I will use 70% or 0.7 for this calculation)

Backup Time = (200 x 12 x 4 x 0.7)/ 750

= 8.96 hours or 8 hours 57 minutes ≈ 9 hours

That is just to power one horsepower (HP) air conditioner. If you make it two, the backup hours is supposed to, theoretically be halved, but in actual sense, the backup hours you will experience will be less than half. The exponential reduction is as a result of Peukert's law. The law proposed by a German scientist Wilhelm Peukert which looks at the phenomenon where a battery's capacity decreases with increase in the battery's discharge rate.

In the above scenario, imagine instead of powering a 1 HP airconditioner that you replaced it with three 40W low energy rechargeable fans. The backup hours will drastically increase as shown below.

Backup Time = (200 x 12 x 4 x 0.7)/ 120= 56 hours = 2 days and 8 hours.

It is crucial that we rule out most, if not all, heavy duty loads such as a cooker or air conditioners when looking at alternative energy. But if you've got the deep pocket to buy enough batteries to handle it, as I said earlier that ain't a cheap option, then, by all means, go for it.

Your best bet as a renewable energy enthusiast is to buy a cheap watt meter in either ebay, or at jumia if you are in Nigeria and check the real wattage of the things you plan to power.

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The two bulbs my friend measured above have almost equal luminosity, but one consumes 200% more electric power.

Please feel free to drop your questions or suggestions below. Thank you.

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^REFERENCES

• ^{Solar Energy}

• ^{Battery Backup Time Calculation}

• ^{Peukert Law}

• ^{Solar Irradiance}

• ^{Solar Energy Data}

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