Hybrid Solar Part 2: How To Future Proof Your Solar System

Hybrid Solar Too?

Please note: this post was written in 2012 and is way out of date.

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In my previous blog post on hybrid solar systems (aka grid connect with battery backup) I promised to follow up with a post that went into more detail on the costs and give examples of inverter hardware that can be used to make such a beast.

I’ve realised that if I go into the costs and paybacks then this blog post may be longer than War and Peace. So in this post I’ll cover the hardware and I’ll save the financials for next time.

As I said in the previous post, your motivation for spending more on a hybrid solar system will likely be either:

1) You want backup power when the grid goes down.

2) You want to minimise your electricity exports due to a painfully low or non-existent Feed In Tariff in your state.

3) You may want to maximise your electricity exports due to a very generous FIT in your state (Hello Queenslanders!)

4) You may want to “shift” the peaks in your grid electricity usage due to a Time-Of-Use electricity tariff. This would involve charging your batteries at a low tariff and using your battery power + solar at peak times to avoid paying the peak electricity rate.

(And even if number 4 is not relevant to you know, I’d bet my mountain-bike that sooner or later everyone will be forced onto a time-of-use tariff.)

Now, I could go through every possible combination of hardware for every possible combination of the 4 requirements above. But the post would be so long and repetitive that even the hardiest solar geek would probably tune out.

So instead I’ll present for your delectation a system that can be configured to do all the above. Which I would argue is the most future proof solution anyway. Because recent history in NSW has shown us that we can’t trust the State governments to keep their word on Feed In Tariffs and it seems obvious that time-of-use electricity charging (you pay more for your electricity at peak times of the day) will become the norm very soon.

Hardware Required for a future proof, super-duper mega, mega configurable  Hybrid Solar System:

First let’s look at what goes into a standard grid connect system:

1) Solar Panels

2) Inverter

3) Everything else: Wires, Racking, Disconnect Switches, fuses etc.

A Hybrid Solar System needs all the above and more. The extra hardware needed is:

Power management unit (box of electronics)

Inverter that can talk to the power management unit (or is integrated into it)

Bank of Batteries

An example of a “power management unit” that will do the job and has all the configuration options you’ll probably ever need is the 5kW Rich Electric SuperCombi.

Makes the coffee too?

This sucker can be configured to:

• Allow you to disconnect fro the grid and still have power.
• Charge the batteries only when electricity is cheap.
• Minimise grid power usage when electricity is expensive.
• Discharge the batteries when electricity is expensive.

And the joy of having such a configurable system is that if, in the future, the government changes the rules you can re-jig your system for maximum profit!

If, for example, the government came to its senses and introduced a “time of use feed in tariff” where you get paid more for exporting energy at peak times, you could configure the SuperCombi to buy the electricity when it is cheap, push it into the batteries and sell the same electricity when it is expensive (ideally along with all your solar power).

To connect the whole caboodle to the grid you would have to combine the SuperCombi with a Grid Tie Inverter from the same manufacturer (e.g. Rich Electric’s SolarWorx GTI). The reason you need to use this particular inverter is that it can talk the same language as the Supercombi so that they can work together and do all the smart stuff listed above.

And don’t forget that you will need at least 200Ah of 48V batteries which will give you 9.6kWh of electricty storage to play with.

Here is how all the bits connect together (at a very high level):

The SuperCombi is the brains of the system and can probably feed the cat too.

As you can see, everything goes through the SuperCombi.  To cut a long story very short, this box of electronics has the ability to be programmed to follow any kind of logical rules based on the state of the batteries, solar panels, grid connection, or time of day. It uses this logic to route either the:

• Solar Power
• Battery Power
• or Grid Power

or any combination of the three to either charge the batteries, power the home or export to the grid.

It can also be configured to only power the “essential circuits” in the house if the grid goes down – to extend the time you can run on the battery bank.

Essentially your solar system has been transformed from a rather simple electrical system, to a sophisticated computer controlled power management and battery backup system. This means that if you are looking to install Hybrid Solar, it is essential that your installer/designer has both the “Off Grid” Clean Energy Council Accreditation (so he knows how to handle the batteries), and also has good experience of the hardware being used, as it gets pretty technical pretty quickly, even for a Chartered Electrical Engineer like yours truly.

Next: I’ll add up the costs of the solar hybrid system compared to Grid Connect and also crunch some numbers to see what the payback is for the extra expense incurred