Off-Grid PV - Time to Upgrade ?

Many early adopters of solar pv are now considering upgrading their systems. Given the huge reduction in price of solar pv panels over the past few years, this makes a lot of sense.

In the following article we take some time to consider the reasons for upgrading and discuss some of the pros and cons of the current solutions on offer.

More Solar ?

Alongside the price per watt reduction, modern solar panels offer very high efficiency levels. This is particularly relevant if the size of the pv array is restricted physically, as it means that you can potentially double the power output from the same collection area taken up by an early pv array.

In some instances, if it's a large upgrade, it's likely that the entire existing system would be replaced. The old solar pv panels can often be sold on for a reasonable price, helping to recoup some of the cost.

However, if it's just adding a few extra panels, this can be done without too much trouble. The new panels will need their own charge controller, as it's unlikely that the new solar panels operate at the same voltage as the older ones. Even if they do, the controller for the old panels probably doesn't have enough spare capacity for the new solar array.

Considerations regarding a solar pv upgrade :

• Modern pv arrays are often wired to a high voltage and use an MPPT controller to bring the voltage down to battery charging voltage. This increases efficiency and allows longer solar pv cable runs. In some cases, this means that the solar pv array can be relocated to a more optimal location.

• Modern panels can offer outstanding value for money - i.e. the Canadian Solar 380W module for £ 186 each (ex VAT). Comes with a 10yr manufacturing warranty and 25yr performance warranty.

• The most efficient panels on the market right now are probably the LG Bifacial panels, which can peak at over 500W on a single module. Alternatively, the LG NeonR 370W offers exceptional output from the same footprint as a 'standard' large panel, rated at perhaps 230W a few years ago.

• The new Jinko 'Maxim' pv panels are 'shade tolerant', thus if your site isn't ideal and gets regular shading, these panels are well worth some consideration. 

This timelapse video shows a test of Jinko's Maxim Integrated Modules and their dramatic 4x gain over standard modules when the array is being shaded by a tree (in the morning). With one shading event, the net gain across the day was 13%. If there were two or three 'events' during a day due to a sub-optimal location, the net gain would be substantial.

More Batteries ?

Off-grid batteries need occasional replacement - how often depends on the type of battery and how much work it has to do, how well it's kept charged, as well as the temperatures at which it operates. 

When replacing the battery bank it's an ideal time to consider some form of upgrade. Is the original battery bank of the correct size (capacity) for today's load levels ? It may be worth going for a larger bank than the original as it will generally last longer. 

Battery technology has come a long way over the past 20 years or so. We're particularly excited by the introduction of Lead Carbon batteries, which are ideal for off-grid power systems. Lead Carbon batteries offer outstanding cyclic performance without the high cost of Lithiums. See our blog article about Lead Carbon batteries here.

Further Considerations :

• Are you upgrading the solar pv array as well ? A larger pv array would mean less pressure on the battery bank, and thus it shouldn't have to work as hard.

• What voltage battery bank ? The higher the voltage, the lower the current flow for any given amount of power. For example, a 3kW load at 12V is 250A but at 24V is only 125A, which requires far smaller cables and fuses, and enables slightly longer cable runs. On larger system upgrades, the only way to deal with the increased currents is either by using huge cables / fuses / mcbs andamp; controllers.... or by increasing the voltage. This does mean that any existing inverters and control gear will probably be made redundant, however this equipment can be sold on.

• Battery Monitoring ? 'Knowledge is Power' has never a more appropriate saying. If planning a battery upgrade, we strongly suggest getting a decent monitoring system to go with it. A modern battery monitor will give the user highly detailed information about how they are using their system. It's now possible to check the status of your system any time you have access to the Internet. This information becomes more and more valuable as the system scales up - large batteries are a costly investment and understanding exactly what's going on with them helps to extend their life.
  
  

Inverter Upgrade ?

If the loads on your system are likely to increase, or you simply want more peak capacity, then it may be time to consider an inverter upgrade. If this is the case, it's important to ensure that the battery bank, cables andamp; fusing are all correctly sized for the increased loads.

Considerations :

• The cost of inverter-chargers has dropped significantly over the past few years, with many off-grid system owners using the highly regarded Victron Multiplus range. This provides the option to have a back-up generator automatically integrated into your off-grid system.

• Having a larger inverter and battery bank won't do much good if the solar pv array isn't big enough to charge it. We are happy to help re-configure systems, please contact our system design team.

Service The Existing System.

Upgrading or not, a regular service of the existing system is essential. This includes a careful check of all of the old cables and connections for corrosion or chaffing and ensure that fuses and/or MCBs are not corroded. Rodent presence is also a common issue - and lizards seem to like inverters !

Ideally there would be some sort of capacity test of the battery bank, to establish it's condition (this is much easier with a battery monitor). More essential is to check the condition andamp; torque of the battery connections - anything wrong here can create havoc with the power system.

The mounting arrangement of the old pv array also needs to be checked for signs of stress or corrosion.

Further Useful Information

Do you have a battery monitor on your system ? If so you need to read this excellent article : Making Your Battery Monitor More Accurate

Need Our Help ?

If you would like our help to upgrade your existing system, please don't hesitate to contact our system design engineers with details of your existing system and an idea of what the new system needs to power. Please see our system design enquiry form.