Costly Solar Mistakes And How to Avoid Them - II
Posted on June 08 2019
Continuing from our previous article where we discussed two of the most major solar mistakes that people often make - the misunderstanding between an off-grid and on-grid (grid-tied) solar energy system, and the incorrect perception of "solar is expensive". Give it a quick read here before you continue with this article. Costly Solar Mistakes And How to Avoid Them - I
Improper Solar Energy System Sizing
Contrary to popular belief, it is not as simple as taking your recent electricity bill, calculating your power usage, and then installing a solar panel system to cover that usage. This method eliminates many important factors, that includes the efficiency of the solar panels, the voltage settings on inverters, the climate of the vicinity, the battery size, whether you are considering a grid-tied or off-grid system.
An expert installing solar panels on a roof. via mysolargoods
To get the True output value from your solar panel system you need to consider the following major factors and then design the corresponding system according to your needs and feasibility. Here we are going to look into some of these factors and see how they affect a solar energy system.
a) Peak Sun-Hours
The first thing to consider is the amount of actual peak sun hours your region receives; remember this is not just the total day-light time, but it is the number of hours the sun is radiating enough energy to generate stable and sufficient energy from your panels. Most places on planet earth receive between 4 hours to 6 hours of peak sun-hours, but you should always check how much does your region receives as this will be a major factor controlling the amount of energy your solar energy system can generate.
Sun hours for Solar Panels in the USA. via wholsalesolar
The other thing to keep in mind is that the rated energy output for a solar panel is calculated under optimal conditions called the STC (Standard Testing Conditions). However, you don’t usually get the optimal conditions in the sky, and thus a good approximation would be to consider the true output of the solar energy system to be only about 80% of the rated power.
b) The Efficiency of Solar PV Cells
Solar panels, although have a lifetime of about 25 years, drop their output generation capacity by about 1% each year. This is not a big drop at all, but this slight efficiency drop accumulates for a greater number over the years.
Considering the long term ROI and your plans to be solar energy dependent for years (let's say 20 years) then a 15-20% efficiency drop can seriously impact the solar installation with time. Here you might think that later on, you can just add another solar panel, but hold your horses as the addition of a solar panel into an existing system is not as easy as you might have thought, details explained below.
c) Voltage, Inverters and Technical Issues
Adding another solar panel into can get tricky. As you know that solar panels generate DC current and we have to convert it into AC current before using it in our homes or supplying it to the grid. For this reason, you always need an electrical inverter with a solar system, of course until or unless you have a very stable DC generation and all your appliances in your home runs on DC power which is barely the case.
A solar energy system set-up. via energysage
Solar panels have a rated output voltage and so does the power inverters, therefore when selecting power inverters you already have to consider how many solar panels can it accommodate. Furthermore, especially on off-grid power, you need to supply just the right amount of current to your battery banks. Too much current and overcharging as well as undercharging and low current both have adverse effects on the battery banks.
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Therefore, power inverters, battery banks, and solar panels are interconnected and you cannot simply add a PV cell and expect more power output. Additional panels might need additional inverters and current adjustment to your batteries. Therefore, timely planning, precise power needs calculations, and future adjustments are always important when you are designing your solar panel system.
d) Battery Banks
If you are considering an off-grid power system, then you most certainly need an energy storage device in the form of battery banks. However, here is a stunning fact. Battery storage capacity is not equal to battery output-power capacity. You can simply not expect to store 100 watts of power and receive all the energy back.
Off Grid battery bank for solar energy system. via newindustry
Lithium-ion batteries, which are expensive and need larger investments to perform well, can give you up to 80% of the actual stored power. However, the cheaper alternative lead-acid batteries can only supply up to 50% of its stored power, that is a cut of a half and can greatly impact your calculations for power output.
Furthermore, lead-acid batteries require repeated and timely maintenance and you cannot add a lead acid battery into an old existing system as the new battery is adversely affected in this method, making the expansion of your solar system difficult. Lithium-ion battery systems easily adapt to the addition of new lithium-ion battery when expanding your solar system, but again it's a costly power storage option.