Testing The Mastervolt Soladin Grid-tie Inverter :

The Soladin actually comes equipped with an RJ45 jack which can be hooked up to a PC or laptop to check how well the system is performing. There is a separate piece of software called the "Soladin Wizard" which can show you the average output from the Soladin over a period of weeks. Some people around the world have configured further bespoke software to monitor and save the statistics from the inverter so that a long term log can be made.

The linking cable that is supplied by Mastervolt is expensive, at appx EUR60. A cheaper but equally good solution is available from another source, called the "sol-get" which functions in the same way. Here the link is EUR35 for the same technology, shown above, and I decided to purchase with a view to using this as a longer term monitoring exercise  for the Soladin. I did download the software and successfully connected the inverter using the "sol-get" add-on, and I was able to view the information on my application using my laptop. However, in the meantime, and in order to get some initial results, I plugged the Soladin into the energy monitor, and tested the output. On a recent day in June it showed 430 watts output, which means that it was operating on appx 70% efficiency. That's pretty reasonable - bear in mind that the you can usually only get up to 90% of the panel wattage in delivered watts, accounting for panel inefficiency, inverter effort and peak light. I have seen it jump to over 500watts on other brief occasions. So the 700watts of panels appear to be doing a reasonable job.  There is an automatic fan in the Soladin, this turns on to dissipate the heat from the inverter when working at high watts. 

Testing The G83 300W Grid-tie Inverter:

This is a much simpler inverter and does not have any recording function, therefore all we can do is to plug it into the energy monitor and confirm the wattage. The tests I did showed 59 watts being output to the grid. This is a bit lower than the overall efficiency of the Soladin string, so I need to monitor this more closely, especially in optimum sunshine, to see what the maximum return will be.

Testing The 500W Grid-Tie Turbine Inverter:

Again these inverters have no recording function - so we need to rely on our energy monitor. When I began the tests the wind was intermittent, so I could not tell if it was working or not. But when checking again on a gusty day, I could easily see the wattage increase in line with the gusts of wind outside. The inverter itself emits a buzzing noise which increases in intensity as more power is generated, and I did see upwards of 220 watts register on the monitor without any switching to the dump load. However I do need to see the dump load in operation to ensure that the turbine behaves appropriately when the diversion is enabled, so am looking forward to a suitably stormy day!  I expect to see the blades slowing down or maintaining their speed, but the blades should not speed up which would indicate a disconnect or some other fault.

Switching Components On/Off:

The switching of the solar PV is based on a single circuit so all I need to do is switch the MCB off and that disconnects the positive connections to the inverter. This is the case for both the Soladin and the 300w solar inverters. The turbine switching must be done more carefully, to control when the power is allowed to flow to the inverter. If I want to disconnect the turbine without any braking then that can be done by simply switching the 2nd 3 pole MCB off, which stops the power to the inverter. However, if I also need to apply a brake to the turbine then I can do so by turning off the 1st set of MCBs.  To turn on again we must first release the brake, i.e. turn on the 1st set of MCBs, before we allow the current to flow to the inverter again. So the order of MCB switching is 2-1-1-2 , i.e. turn off the second, turn off the first, turn on the first, turn on the second. That way we never allow a braked (shorted together) set of wires to run live to the inverter. There are some clever turbine stop switches that can be bought which apply a resistor current to slow the turbine and then disconnect it, but they are usually priced at over EUR140 and would only be of benefit when specifying a larger turbine system.

Long Term Monitoring:

As mentioned already the Soladin has the ability to record ongoing figures which can be logged into a PC for long term study, but there is no such logging available on other inverters. One possibility is to get a set of better energy monitors which log the power produced in the monitor itself... these may be quite limited, I suspect I need to check which of the plug-in energy monitors have the best data logging function.

System Set up Costs:

Similar to what I did for the off grid system, here's a breakdown of the costs so far in swapping from the off-grid to a grid-tie system:

It will be interesting to see how well the system performs in terms of payback! It looks like it would need to work for a long time before any kind of parity would be achieved. But that's wasn't the primary objective here - after all, if I don't experiment then I will never learn! Also, bear in mind that there is less maintenance involved with grid-tie systems over their lifetime, because there are no batteries involved. On the downside, there is no backup power available from grid-tie when there is a power cut.