Aaron Ardiri
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Internet of Things (IoT)

RIoT Secure AB


It is only natural in the land of the sun and great beaches that solar panels are a necessity.

As the popularity of installing solar panels increases - there is an ever increasing need to not only understand how your power bill is affected by them; but all us tinkers have an urge to get their systems online for real time monitoring. Of course; depending on the make and model - real time monitoring may only be walking by it on an hourly basis, the good news is that most new solar inverters have internet connectivity or an interface where you can integrate your own.

Lets do a quick Renewable Energy 101 recap - lets understand how it works.

There are a lot speculation around the question of whether the costs of installation of solar panels are actually worth it and will the amount of energy produced actually cover the cost. The simple answer is yes, depending on the size of the system and more importantly how you use power during a typical day. If you are expecting to get a cheque from the energy company - forget it.

Lets understand the cost structure - here is the reading of my own power meter over last day:

                   meter                     meter (export)
    14/Oct/2015:   2085                       1285
    15/Oct/2015:   2099 - 14 kW import        1301 - 16 kW export
         total number of kWh generated by solar panels: 20 kW

The solar setup I have is a 5kW Fronius Symo system connected to a western power U3300 meter - of course, you need to review the manuals of your own system to know how to extract the various values from both systems. At least; you can understand what the power meter guy gets up to.

So; what does all this mean?

As shown in the image above; there are two main curves typical each day - the blue curve shows the typical solar power that is generated and the orange curve shows the typical power usage over a day. There are three filled areas; orange, red and blue. The orange represents power that is imported (expensive), the blue is the power exported (refund) and the red is the best - free energy.

My power plan is a Home Plan (A1) - which is setup in such a way such that for every kW I import, the charge is 23.3663 cents - for every kW I export, they will credit my account 7.1350 cents. It doesn't sound exactly fair - why do we pay three times more for importing power? Thats something for the power companies to answer - but, it does have implications on when you should use power.

So what are the actual savings or benefits here?

    import: 14 kW @ 23.3663   =  $3.27
    export: 16 kW @  7.1350   = -$1.14  (credit)

At first glance; it doesn't look that impressive - for all of this effort your electricity bill only drops by whopping $1.14? In context of the whole bill this is a 34.86% reduction and it is going to take a very long time to recoup that $5000.00 originally spent to install the panels right?

A credit $1.14 per day would be a total credit of $416.10 per year. It would be over 12 years before you would get your $5000.00+ investment back - surely; you must be insane to install them right? That is right around the warranty time for the system - Let's not jump to that conclusion so quickly - we still have a little more to cover.

The secret is that there are those "free" kW of energy used during the day that you simply are no longer paying for - but you would if you didn't have solar panels. In the day example above; this was a total of 4 kW - which equates to $0.93 (at 23.3633 cents per kW). With that number in mind; the accumulative savings is a much better $2.07, or 63.3% reduction in costs.

In this case; the total savings would equate to $755.55 per year which would take just over six and a half years to recover the $5000.00 installation cost - this make more sense; as most solar inverters have a 10+ year warranty and solar panels have a warranty of 25 years.

The bottom line is that if you have solar panels - you simply need to use your power when the panels are generating power, typically during the day. This is how you get maximum return for your investment. To save; never run appliances before the sunrise or after the sun has gone down.

In the next segment; I will cover the process of getting my system online so I could get real time monitoring from anywhere in the world - the process will be similar regardless of the inverter; it is just a matter of knowing what you are doing. Stay tuned for the upcoming post on the topic.


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Bringing your Solar Inverter online (part 2)
Industrial integration (Modbus) using an Arduino

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