Smart Energy Controller (Grid Tie Limiter)

Are you tired of waiting for Eskom and the council to come to the party with net metering?
Are you limited by a prepaid meter that either trips or bills you for exporting power?
We have been informed in an email direct from Cape City municipality that “net metering” for residential in Western Cape is going to amount to zero paid to you for power exported!
Do you want to give away energy and buy it back later at exorbitant costs?

It’s time to take control of your energy world.

The new Exsolar Smart Energy Controller is designed to control and limit the Fronius range of grid tie inverters. The controller will match your local load to the maximum power available from your system while providing detailed reporting at the same time.

Auxiliary relays also control other loads like pool or borehole pumps to put excess power to good use.

Our design with the rapid response time of world class Fronius grid tie inverters, provides a realtime solution that works. Detailed per second reporting is also provided as with the energy monitor but now we have added these features to 1 device.



As you may be aware, solar production in Europe has peaked in recent years and as a result, there are many high quality Grid Tie Inverters (GTI) available on the market at very reasonable prices.  (Grid Tie Inverters allow the independent PV solar systems to be connected to the grid).

The Fronius brand from Austria is one such inverter that, combined with the standard 5 year warranty (extendable to 20 years), offers a great investment opportunity in terms of a self-production solar powered system.  The problem however is that the South African government has not come to the party in terms of allowing the feed-in of unused solar energy back into the Eskom grid.  Eskom has however announced a feed-in tariff structure that is actually quite laughable – not forgetting the fact that you have to purchase a new 4-quaddrant meter AND pay a premium rate to have this facility available at your house.  These additional costs make it totally unfeasible to install a solar system and rely on Eskom rebates to finance the project.

In light of the above problem, in conjunction with our existing Smart Energy Monitor, we have developed an additional module that directly communicates with the Fronius Grid inverters and backs down (or limits) the power production to match your load.  That is, as the load in your house varies, the Energy Monitor will communicate with the Fronius GTI and prevent feedback of any excess energy via your pre-paid meter.

A screen-shot of one system without the grid tie limiting function. Notice that the excess energy is pushed back to Eskom (negative values).



This would be great if you were being credited for what was exported (negative values) but the reality is with a prepaid meter, you are charged for this as if you used it!!
Or event worse, the meter trips out and isolates your power with a tamper alarm.

Our solution is to control the grid tie inverter to prevent exporting.

Screen Shot 2014-03-10 at 6.43.36 PM


Detail of the above showing rapid response to load:

Screen Shot 2014-03-10 at 6.45.04 PM


Alternatively you can use our battery cycling feature and/or our geyser boost option to fully utilise available solar in self consumption mode.

Bellow, you will notice utility power is disconnected at a given time and then reconnected the next morning at another set time. The batteries do not charge until there is excess solar is available. This also means that when batteries are changing, they are doing so using the inverters regulated charge mechanism and the inverter is still connected to the grid. Other options use frequency shifting that can result in light flicker.

Screen Shot 2016-07-22 at 19.37.34

AC usage

Notice the DC voltage bellow has a smooth charge and discharge cycle. The State of charge (S.O.C) of the battery can be set to ensure the battery is not cycled bellow a value you prefer. The more aggressively you cycle batteries or at least the lower S.O.C value you choose, the less the battery lifespan will be. Using tubular plate battery technology and a S.O.C of 80% will typically give you 20 years on flooded lead batteries.

Screen Shot 2016-07-22 at 19.37.55

DC usage

Battery cycling can be combined with our Geyser Boost technology with dumps excess solar into hot water after the batteries are fully charged. Please see more detail about this here.

This is all designed to consume as much solar power as possible without needing to export power into the grid.

This product is developed for and marketed by Exsolar.