Energy Matters Forums

[Tracker]

..
and wondering what the 2017 answer is to "ZERO Export"

Is there a commercial Export Preventer, that will divert power to a HWS (eg.)

Thanks

[Warpspeed]

If you want total export prevention, simplest way is to combine a grid powered dc rectifier (for power at night) with solar during the day to drive an inverter. This is most efficiently done at a higher dc voltage.

Solar takes priority and will contribute everything it can, and the grid supplements any extra loading beyond what solar can provide. Grid power becomes essentially zero during daylight hours.
At sunrise and sunset the gradual changeover is seamless.

Grid tie was fine when they only charged us for net usage.
That is now just a memory.
Do it yourself by drawing only what you need from the grid and feed nothing back.

If the grid goes down, you still have power during daylight hours.
All this assumes a simple minimalist low cost system without a battery.

[Gordon-Loomberah]

If the grid goes down, you still have power during daylight hours.
All this assumes a simple minimalist low cost system without a battery.

What sort of off-grid inverter will run directly from PV with no battery? What happens when load exceeds supply, say if a cloud covers the sun?

[Tracker]

..
Yes, KISS is good, but I am thinking that I want more..

I'm looking at the EverGen system, but I am starting to wonder how it actually works..
I'm starting to think it is not as great as it seems, and is more of a power-time-shifting device, and not a genuine "UPS" system..
they are not all that clear on how it works..
..

[Warpspeed]

What sort of off-grid inverter will run directly from PV with no battery? What happens when load exceeds supply, say if a cloud covers the sun?

Just about any solar controller should work without a battery. It just "thinks" there is a battery there, but its fully charged and so limits the output voltage to the maximum charging voltage.

Assume a 48v volt lead acid solar controller set to charge up to around 56 volts maximum. That is what it might go up to without a battery connected and no load.

Now assume you have a dc rectifier connected up that outputs a solid 48 volts dc (or something) maybe a fork lift battery charger set to its minimum adjustable output voltage.

Connect both up together through diodes to drive an inverter.

During the day there might be up to 56 solar volts, or something a bit less less if its cloudy or the inverter load is heavy.
If the voltage falls far enough, the rectifier kicks in to prevent the inverter input voltage falling below 48 volts (or whatever).

So you always draw power from solar first, until there is just no more there to get, then anything beyond that comes off grid.
During extreme cloud, the system may struggle and intermittently draw grid power.
At night it obviously all comes from the grid.
On sunny days, nothing from the grid.
Its up and down and constantly varying.

You just need an inverter that has a wide enough safe input voltage range to cover max peak solar voltage to minimum grid rectifier supply voltage.
It may also benefit from a large capacitor bank to absorb very sudden load changes, or excessive ripple voltage coming from the rectifier, or that may not be necessary.

Its not complicated, but it does require some careful thought, and choice of suitable equipment that will work together.
If properly set up this definitely works.

*Hint* one of those salvaged grid tie toroids suitably rewound for the voltage of your choice might make the basis of a nice dc rectifier. (Rather like an Oz inverter in reverse)
Its just a case of thinking the whole thing through very carefully and making everything compatible.

[Tracker]

What sort of off-grid inverter will run directly from PV with no battery? What happens when load exceeds supply, say if a cloud covers the sun?

I let that go to the keeper..! Not interested in the complexities of it all as not what I'm looking for..

The only way it could be considered possible is if the GRID provided the DC to supplement the PV DC power..
which would mean there would be some inefficiencies there..
DC Coupling rather than AC Coupling
I would imagine that the idea would be to have something like PV-DC of say 250V and GRID DC of 230V..
but I suspect you would need an ISOLATION transformer as the Grid-DC (device) might upset the "Grid Impedance" for the inverter..

Should work in theory, but I would use a time switch or a LIGHT Switch, and go to pure GRID at night
but - I can't really see how it's any better that pure AC Coupling..



Have you looked at the CSIRO EverGen..??
..

[Warpspeed]

It not only works in theory I have been using such a system for over a year.

As you are not interested I will not comment further.

[Gordon-Loomberah]

Evergen looks interesting, but what does it cost?

Some inverters are able to be configured directly, or with an additional bit of gadgetry to prevent exports. I think zero export is compulsory in some areas.

Why do you want zero exports anyway, surely it is better to get a few cents per kWh for anything you cant use. There's only so much energy you can put into a HWS before the water boils.

[Tracker]

Evergen looks interesting, but what does it cost? .

Thank you for requesting further information on our battery and storage system.
 
The biggest difference with our system, is the Intelligent Control developed by CSIRO. The Intelligent Control learns your energy usage habits and takes into account local weather data to predict your energy requirements - and ensures your system is charged accordingly. With this technology, we can optimise the charge of the battery to not only meet your needs but also extend the life of the battery (all while reducing your power bill).
 
The status of your system can be visualised by downloading our mobile app and unlike the Tesla (for example), our Intelligent Control allows you to utilise your battery multiple cycles per day - further improving your return on investment.
 
Through the research conducted by CSIRO, Evergen has selected the batteries to ensure the maximum quality possible from your system. Currently the systems have a 5 year product warranty on the full system and a 7 year performance warranty on the battery modules. The Evergen Intelligent Control is also designed to help maximise the life of the batteries.
 
The battery needs to be housed indoors in a dry location in an area that is not normally used as a living space. Garages or similar storage spaces are ideal. The dimensions of the unit are (W x D x H) 610 x 650 x 1630mm. As it is an all in one unit this includes all components.
 
The retrofit option is modularised so increasing the capacity of the battery simply involves purchasing additional battery modules to slot into the system. Each module is 4.8kWh, and the system can hold a maximum of three modules (4.8, 9.6 or 14.4 installed capacity), with the first module included in the purchase of the system. If you wish to purchase additional modules to increase the capacity these are an additional $2800 each. Upsizing your battery capacity at the time of the initial install is the cheapest option, however upsizing at a later date is also possible but will incur additional freight and install fees.
 
Our system interfaces with your current system via a meter on the AC side of your current inverter which feeds data into our Intelligent Control. We will not need to do anything to your current PV system and your current PV will continue to run on your current inverter. This means any warranties on your current system will not be affected.
 
The pricing for our batteries, which again includes the control and also standard installation charges, is:
 
4.8kWh            -           $9490 
9.6kWh            -           $11400
14.4kWh          -           $14000

[australsolarier]

yes there is a device that can be used to divert excess into a hot water system. can't remember the name, but it was mentioned on this forum before. and it is reasonable pricewise also, something under 400$ if i remember correctly. googled: immersun and solar mate.
https://www.solarquotes.com.au/blog/div ... -cylinder/