A heap of off-grid solar power systems were installed in Saskatchewan, Alberta and especially in British Columbia decades ago. They used to be the only solar electric options available before net metering and micro-generation regulations took place. Some of these old systems still operate nowadays and there is a generation of off-grid installers who grew up building and maintaining these systems.
As solar system components become older, off-grid system owners start wondering if and when it would be worthwhile to upgrade the solar systems versus keeping and maintaining the older solar system. To help with this challenging decision process, we decided to share some of our thoughts in comparing the older off-grid solar designs and the new technologies.
If your off-grid solar system still works well and meets your electricity demand, you did a great job in maintaining it over the years and choosing a good solar installer in the first place. In this case you may just be curious what has a potential to break first?
The most frequent reason for a system upgrade is a battery failure. Loosing only one battery in a large battery bank is very unfortunate as replacing just one bad battery may be a very short-term bandage-type solution, while replacing the entire battery bank is very costly. Inverters and charge controllers have a much longer life, but they eventually fail too. Solar panels (PV modules) are degrading 0.5%-1% every year and PV technology evolve with higher-efficiency modules produced today compared say 10 years ago. Finally, electrical codes underwent substantial changes for solar power, including off-grid solar.
A new 300W 60-cell solar panel can replace a high efficiency 5-year old solar panel of 180W and it can be done at a significantly lower cost per Watt. This creates an opportunity to utilize the same racking, adding charge controller capacity while increasing the system DC size. Charge controllers without MPPT (maximum power point tracking) need to be replaced by new charge controllers to be compatible with voltages of new modules.
Affordability of new PV modules dictates new considerations for racking type and array locations. In the past it was the most economical to install solar panels at the optimal tilt by building rooftop structures and 2-axis trackers. Now it is often far cheaper to install extra PV modules on a vertical wall or on an awning racking, than investing in more expensive racking to optimize the tilt. Lower tilted roofs are not a good option for off-grid solar systems at all as the solar panels will become covered in snow when solar energy is needed most.
DC-coupled systems were the standard design in the past. The attributes of those designs are: short DC strings, combined efficiency losses at charge controllers – batteries – inverters, sophisticated logic for integration of additional DC sources. New AC Coupled systems provide much better efficiencies and more flexibility in integrating addition solar energy sources.
Batteries have evolved over the years with more choices available today. We would like to especially note two battery technologies with improved battery life that are well suited for off-grid solar PV systems: carbon-enhanced lead acid and lithium ion. Nowadays, the owner to have ability to choose battery technology depending on the application and willingness of the owner to maintain the battery.
Last, but certainly not least in solar innovation is a development of multiple energy monitoring, data logging equipment and systems automation. All major inverter manufactures have monitoring devices that can be connected to the internet and be accessed online. Data logging capabilities of off-grid solar systems significantly simplify the trouble-shooting and they help with the solar system preventive maintenance.