Of a budget Solar Inverter System - Solar Panels.

I started a blog series documenting a budget off-grid solar-inverter setup I am currently working on. The first post in the series focused on how to carry out an energy audit to help scope the power and energy requirements. This post will be focused on solar panels, how to determine the size, which to buy, why, and where.

The basic Setup of a solar inverter offered system is made up of 4 Core components.  The components and their relationship is illustrated in the diagram below

         +-------------+
         |    Solar    |
         |    Panel    |
         +-------------+
                |
                |
                V
         +-------------+
         |  Solar      |
         |  Charge     |
         |  Controller |
         |             |
         +-------------+
                |
                |
                V
         +-------------+
         |   Battery   |
         +-------------+
                |
                |
                V
         +-------------+
         |   Inverter  |
         +-------------+
                |
                |
                V
            AC Loads

Solar Panel:  Size, Type Model

Based on the energy audit calculation in my previous post,  the result of the audit would help in sizing of the solar panel that would be used for this project.  
3934Wh approximated to 4000Wh is the amount of energy to be used by all the essential appliances to be powered by the system.  The goal is a solar panel array that is able to generate this amount of electricity within an average day.

Losses and more Losses
Losses happen when we are dealing with electricity, a 100w solar panel would not produce 100w of electricity most of the time in fact 99% of the time it would produce less.  Heat, wiring, distances between the panels and the battery., and solar charge controller efficiency are just some of the things that can cause losses between what the solar panel generates and what goes into the system.

Designing around Losses.
A good system design tries to reduce losses to the barest minimum. The system is also best calibrated around the expected loss. How is it to do it?

Solar Panels only work when the sun is up, the brighter and less cloudy it is the more electricity is generated.  Best practice requires that a conservative sun hour is used when trying to determine the average number of electricity a solar panel can generate. How most places in Nigeria, 4 hours is a decent number to work with. - Places in the north have higher numbers -

For this project, I would be going with a 4 x 380w Solar Panel.  The assumption is a 70% power loss and 4 hours of sun hours.

380w x 4 = 1520w.  1520w is the power that the solar panel can produce at standard conditions (The sun is just at the right angle, with the right irradiance and temperature is just right) we assume a 70% loss i,e we would lose 30% of the potential of the Solar Panels to one form of loss or the other.

70% of 1520w = 1064w.  1064w is our expected power from solar panels.

The second assumption is 4 hours of sun. This again might seem too conservative but for an off-grid system, it is best to plan for rainy days - no pun intended. The goal is to have a system that would operate fine even when the sun has limited availability.

4 hours x 1064w  = 4,256 watt-hours
Based on our energy audit, the energy usage numbers for the house is 4000 watt-hours, from the above calculation. The expected energy to be generated from the solar panels are conservatively 4,200 watt-hours.

• Energy to be used 4000 watt-hours
• Energy to be generated 4256 watt-hours.

Type of Solar Panel
This is a budget solar off-grid build, however, 1 thing I would be splashing money on is the solar panels. they are the most important component since they generate the electricity to be used. I don't advise people to go cheap on panels.
Solar panels and in fact, solar components generally are rated in Tiers.

The solar panel I would be going for is Jinko 380w.  Jinko, Canadian Solar, JA Solar, Trina Solar, Longi, and Yingli are some of the other Tier 1 solar panels available in the Nigerian market. You can not go wrong with either of them.
The panel cost ₦112,000 ($150) x 4 excluding shipping which in my case is ₦30,000.  That's ₦475,000 on panels.  

Other brands which can be considered include Era a slightly cheaper tier 2 panel which delivers good value and Yingli - the latter is unfortunately always out of stock.

In conclusion

The Yingli 380w solar panels x 4 can generate close to 300w if installed properly with the right alignment.  -₦475,000.00 takes our ₦1,200,000.00 budget to ₦725,000.00.  In the next post, we would focus on the Battery and Solar Charge Controller.