PV solar systems: Which option is best and why?

Farmers more than anyone know the importance that the quality of manufacture can have on the longevity and quality of a machine or tractor purchase.

The choices of technology to use when purchasing a PV solar system are even more critical to ensuring that you get decades of trouble-free electricity generation from your renewable investment.

A solar PV system comprises PV panels, inverters, roof mounting kit, battery storage, safety switches and possibly technology to divert surplus generation to heating water or to EV charging.

Market standard PV panels are nearly always manufactured in Asia, are 1m x1.7m in size and come with a 10-12-year product and 25-year performance warranty based on a maximum annual reduction in performance of 0.7%.

The solar cells are sandwiched between glass on the front and a foil laminate on the back. Panel wattages vary but this matters little. For example, to install a 6KwP system, it would take 20x300w or 18x 335w panels and space is seldom a limiting factor on farm roofs.

The alternative product is Solarwatt, the only PV panel on the Irish market manufactured in Germany.

Solarwatt comes with a 30-year product and a 30-year performance warranty based on a maximum annual reduction in performance of 0.34%.

The solar cells are sandwiched between two panes of self-clean hardened glass making the PV panels very robust and ensuring that neither a continuous humid/harsh farm environment or ammonia gasses/salt air can ever impact the solar cells.

They also come with a five-year all-risks independent insurance cover including loss of generation, theft, damage etc. Solarwatt warranties also cover parts and labour should a problem arise during their 30-year warranted life.

6kwp solar PV system on mixed farm in Cork

Inverters convert the solar DC energy generation into AC current ready for use on the farm business and/or home.

There are numerous inverters in the marketplace with most of the more common brands manufactured in Asia and offering a five-year limited warranty.

Quality designed systems come with a Fronius or SMA inverter which are European manufactured and generally cost nearly twice as much as their Asian equivalent. However, there are good reasons for this.

For example, Fronius is Austrian and comes with a seven-year warranty which they will extend to 20 years for a small additional premium. Fronius inverters are warranted to install up to 50% more solar PV which can significantly improve economics and capacity of the farm to use all of the energy generated.

Fronius inverters and Solarwatt battery install in Longford

A solar PV system is mounted on the roof in various ways depending on the roof type. For farm roofs, generally the system is connected to timber or steel purlins using stainless steel hanger bolts.

Aluminium railings are attached to the hanger bolts and the panels attached to the railings.

Quality roof mounting kits such as Schweitzer (Hilti-designed) provide at least 10-year manufacturer warranties and carry out an engineering design report for each installation to ensure the system is mounted correctly on the roof and takes account of wind loads etc.

Railings are attached to shed purlins using stainless steel roof mounting hooks

Battery storage choices are also critically important to the longevity and performance of any system purchased.

Many of the battery storage systems on the market are Asian manufactured and come with a five-year limited cycle warranty with 85-90% charge to discharge capacity and response times are slow often in multiple seconds.

Some battery systems can also charge DC and AC, but buyer beware as the efficiency losses can outweigh any possible benefits from charging on night rate electricity as well as solar PV.

An alternative option is to choose a German manufactured battery system such as Solarwatt which comes with a 10-year unlimited cycle warranty, 100% charge to discharge and the fastest response times and highest safety standards in the marketplace.

Another high-quality battery system is Sonnen which is also manufactured in Germany.

910kwh Solarwatt battery storage system installed in Kerry

Export Meter

There is little merit, in our opinion, in investing in an export meter at this time and anyone who suggests that it may be of benefit needs to explain why.

ESB networks are rolling out smart meters, 250,000 this year, to every home and business at no charge and this will manage import/export and any investment in an export meter is wasted as a smart meter will be needed to facilitate a payment system for export to the grid going forward.

A 50kwp solar PV install on poultry farm in Monaghan

Grant options

In relation to grants, there are several options and we are very appreciative of the positive engagement with the Department of Agriculture on amending the solar PV scheme under TAMS.

Hopefully, an announcement on these changes will be made very soon. Other options for getting grant support include a Better Energy Community or Horticultural grant.

The tax benefits are also very good. For example, a sole trader or company can get 100% accelerated capital allowances offset against income tax in the year of investment.

In summary, check out the various technologies available and insist on datasheets to prove that what the company salespeople are saying is accurate.

Check out the grant options and tax benefits for your business and get written financial assessment on payback from your supplier and finally make sure that your investment delivers on your expectations by choosing the right technology on day one.