Let's take another shot at our solar system, which aims to enhance the rather disappointing performance of the installed panels. Despite having 6kW of panels, we're only able to generate a maximum of about 1.5kW of power, due to factors like shading, geographic location, and the time of the year. Admittedly, we might be a bit ambitious, but we're convinced that we can do better.
Improving the efficiency of these panels means replacing them, which we probably will do at some point. So, the next angle of attack was to link them differently, as discussed in an earlier Blog (HERE). Our remaining option was to understand better how they could be optimized to maximize power production throughout the day. Aiding this understanding is the rather good VRM Portal app from Victron, which gives great insight into what's happening with their equipment. Our solar panels turn off when batteries are at 100% (as one might expect), but the system is set up to maintain that 100% charge state from whatever available power source. The upshot is that Solar is mostly turned off without manual intervention when connected to three-phase shore power!
So, off we set to make some changes!
When first configured, the Victron Multiplus Inverters maintained house battery charge at 100% using either shore power or drawing from the large Praxis hybrid power batteries. The Victron MPPT Solar controllers charge the batteries from Solar between charge levels of 0% and 100%. Once batteries are >95% charged, the charge current ramps down until 100% charged, and then they effectively go open-circuit and turn off. They provide Solar power only once the battery charge falls below 100%. So if the system keeps house batteries at 100%, no solar energy is made.
Our journey was made smoother with the help of some excellent subcontractors in Palma, particularly the invaluable assistance of Magda from AkuPalma. She programmed and installed a program (Node-RED) onto the Victron Cerbo controller via their remote communication platform. Once installed and enabled, Node-RED allows us to configure the Victron Cerbo controller so that, in this instance, we can trigger systems to start/stop charging at different battery charge levels.
Using Node-RED, we reconfigured the Multiplus inverters to start charging batteries at 80% and stop charging when 100% full. Batteries then discharge from 100% to 80% before the cycle repeats. See the figure below. 80% is a random selection and can be varied through experience.
The advantage of this is that as the batteries begin to drain, the MPPT controllers are triggered, and we maximize solar power as the batteries drain to 80% and recharge back to 100%. Batteries now spend only a few minutes at 100% charge before the cycle repeats.
We do not produce more power from solar panels per se, and the panels are no more efficient, but we maximize solar energy production for a far greater duration each day. This was achieved by preventing the MPPT from shutting down with a 100% charged battery.
Have a look at the figures above. The maximum we achieved was Turkey in May at 163 kW.H for the month when we were experimenting with the house battery charge.
Spain is at a similar latitude, and October typically produces 30% less Solar than May/June. We have operated the new Node-RED software app for 18 days, generating 120kW.H of solar power.
Projecting forward from 18 days to a 30 day month and referencing "May," we generate around 120/0.7x30/18 = 285 kW.H.
Heck, an improvement of 75% or an additional 122 kW.H of power from the same system.
