| There is so much hype around living "green" or | | | | can also equate to 5A per hour for 20 hours. |
| eco-friendly, but the one thing that puts people off are | | | | Power Inverters |
| the cost involved in going green. I know, because that | | | | Now that we've got the power stored in the batteries, |
| is the first thing that comes to my mind when I think of | | | | we need a way to use it in our every day lives. |
| going green. | | | | Batteries can provide stored electricity as Direct |
| I put some effort into researching various alternative | | | | Current (DC). Our every day appliances in the house |
| green energy sources and have come to the | | | | make use of Alternating Current (AC). Thus we need |
| conclusion it might not be as expensive as we first | | | | a way to convert it from DC to AC so that we can |
| think. | | | | use it. |
| From the various options, solar panels seemed to be | | | | That is where Inverters come into play. The one that is |
| our best option. It might not be for you though. | | | | recommended is the True Sine Wave Inverter, which |
| Reasons I prefer a solar panel system: | | | | provides AC power that is basically identical to the |
| - Not as noisy as wind turbines | | | | power we receive from Eskom. |
| - Easily expendable | | | | Inverters are rated by the amount of AC power they |
| - Easily movable which is a bonus if you're on a farm | | | | can supply continuously. |
| - Our climate is perfect for it | | | | Now that I've explained all the above, you might have |
| A few downsides: | | | | a better understanding of what a solar power system |
| - The initial outlay of costs | | | | is. Let's have a look at how you would go about sizing |
| - The space it will occupy (mainly the batteries) | | | | your installation requirements. |
| First of all, let's look what a solar panel system | | | | Appliances and Power Usage |
| consists off. | | | | The first thing you need to do, is also is most |
| It can basically be split into 4 parts, namely: | | | | cumbersome. You need to determine how much |
| 1) the solar panels | | | | electricity you will be using and for how long. This is |
| 2) solar regulators | | | | easy, you write down how much Watts (W) an |
| 3) batteries - storage | | | | appliance uses, and how many hours per day on |
| 4) inverter - DC to AC | | | | average you run it. That will give you a certain amount |
| Solar Panels | | | | of W per day. |
| Simply put, these are the panels that will take the | | | | Let's look at an example: |
| sunlight and convert it into power. They are rated in | | | | 5x 60W globes = 300W working 8 hours a day every |
| output in Watts, which means the amount of power | | | | day = 2400 Wh |
| the solar panel is expected to produce at a sunlight | | | | 1x 300W TV = 300W working 2 hours a day every |
| intensity of 1000w/meter at 25 degrees centigrade. | | | | day = 600 Wh |
| You might be asking, "What?!" at this stage. | | | | 1x 250W Fridge = 250W working 24 hours a day |
| Throughout the different areas of South Africa, the | | | | every day = 6000 Wh |
| average amount of sun per day varies. The average | | | | 1x 800W Washing Machine = 800W working once a |
| in South Africa is 8.5 hours per day. (Interesting side | | | | week for 2 hours = 228 Wh |
| fact, in London it's 3.8, Rome it's 6.4 and New York it's | | | | That means we use a total of 9228 Wh a day |
| 6.9). South Africa has the of the highest average | | | | Power Inverter Size |
| amount of sunshine per day in the world. This makes it | | | | To determine the size of the inverter you are going to |
| perfect for solar panel usage. | | | | require you'll need to determine the total Wattage (W) |
| If you take a 80 Watt panel, it means it will generate | | | | of the appliances. |
| an average 680 Watt Hours (Wh) per day throughout | | | | From the above example it will just be: |
| the year. | | | | Light Globes - 5x 60W = 300W |
| Solar panels can be wired to increase voltage or | | | | TV = 300W |
| current. A normal panel's terminal voltage is rated | | | | Fridge = 250W |
| between 17 and 22 Volts, but making use of a | | | | Washing Machine = 800W |
| regulator regulates it to 13 Volts. The reason for this is | | | | Total power draw require = 1650W. This means that |
| that the safe voltage for charging a battery is | | | | when all those appliances are on at the same time, it |
| between 13 and 14 Volts. | | | | will draw 1650W. You will also add in about a 50% |
| Solar Regulators | | | | buffer. That way if you ever run your hair dryer at the |
| As mentioned, the solar panels can produce between | | | | same time the system will have power in reserve to |
| 17 and 22 Volts. This is however a lot more than the | | | | run it. So a 2500W inverter will be perfect for this and |
| safe range of between 13 and 14 Volts that you can | | | | will leave you with ample buffer. Remember this |
| charge a battery. To regulate this we make use of a | | | | calculation is about appliances that will run at the same |
| solar regulators which drops the current causing a | | | | time. By planning right (i.e. use either the kettle, hair |
| stable voltage. | | | | dryer or iron at a time, but not all at once) you can |
| The batteries you'll be using are sensitive to over | | | | bring down the amount of power you require, thus |
| charging and dropping below a certain voltage. The | | | | bringing down the cost of this solar panel system. |
| regulators helps to not over charge the battery or | | | | The number of Solar Panels and their ratings |
| have the batter run too flat. | | | | The total power usage daily is 9228 Wh. Now you will |
| Solar regulators are rated by the amount of current | | | | need to know on average how many sunlight hours |
| they can receive from the solar panels. | | | | your region has. I've found many websites that detail |
| The regulator must be able to handle the maximum | | | | this, so that shouldn't be a problem. Let's work on |
| current that a solar panel may produce. This can be as | | | | about 7 hours. That means 9228Wh / 7h = 1318.30W. |
| much as 25% more than the rated output current of | | | | Add about 20% for a buffer and for any inefficiencies |
| the panel. So if you have a 100W solar panel with 5.8 | | | | with the panels, and you'll end up with a requirement to |
| A current rating you'd want to use a 7.54 A regulator. | | | | generate 1576W of power per day. |
| I'm using 30% to be on the safe side. | | | | You'll need to get enough panels to have all their outing |
| Batteries | | | | ratings add to 1576W. So if you wanted to get 140W |
| Once the sun light has been converted to electrical | | | | panels, you'll get 12 of them, because 12 x 140W = |
| power, we need to store it somehow. For this purpose | | | | 1680W or 24 x 70W = 1680W. |
| we'll be using deep cycle batteries. These are the | | | | How many Batteries? |
| same as normal car batteries, but with a few | | | | This depends on the panels that you use. The 140W |
| differences. They are designed to be discharged over | | | | panels produce a current of 7.7A. So if you have 12 of |
| a long period of time and can be recharged over and | | | | them, the total current would be 92.4 A. The current |
| over and over and over. Car batteries are designed to | | | | also also be there for about 7 hours a day (the |
| provide a large amount of current in a short amount of | | | | amount of sunlight per day). That means there will be |
| time. | | | | 646.8 Ah per day that needs to be stored. |
| In order to get the most out of your deep cycle | | | | If we look at the 102Ah batteries, they shouldn't be |
| battery, you must not let it discharge to below 50% of | | | | allowed to discharge more than 50%. That leaves us |
| it's capacity. By letting it go below 50% it reduces the | | | | with about 50Ah. Therefore, to make up 646.8 Ah per |
| life span of the battery. | | | | day we'll need at least 13 batteries. |
| These batteries are rated in Ampere Hours (Ah) and it | | | | What size regulator? |
| includes a discharge rate in Hours. This is the amount | | | | The last thing to consider is the solar regulator. A |
| of current that it can provide over a certain number of | | | | 140W panel produces 7.7A of current. There will be a |
| hours. | | | | total of 92.4 A of current. That means at least 4x 30A |
| A 100 Ah batter with a 100 hour rate will supply 100 Ah | | | | regulators. |
| over 100 hours. This is 1A per hour for 100 hours. This | | | | |