The solar PV session at the Renewables Roadshow gave an overview of solar PV technologies, available grants and where to start in getting solar on your farm.
Central to this session were real-life case studies showing how solar works on farms.
The data for the case studies was supplied by the IFA and Bord Gáis Energy and are from real farms, although the names, locations and farmer images have been changed for data protection. These case studies are site-specific, and may differ from how solar PV will work on your farm. Nonetheless, they served as a useful example of how the theory of solar PV can work in practice. This article will run through the case studies presented on the night.
The first case study was of a dairy farmer from Cork who milks 200 cows. For the purposes of the case study, we’ll call the farmer ‘Tom’. Tom milks his spring-calving herd at 6.45am and 3.45pm. He produced 5,000l per cow per year across his 170ac block. Tom uses a 20-unit herringbone parlour and has a 18,000l bulk tank.
Tom’s electricity use
Tom uses 53,345kWh of electricity per year. Like most dairy farms, the bulk of the electricity is used for heating and cooling.
Cooling milk accounts for 55% of the total electricity use, while heating water accounts for 25%.
The parlour only uses 15%, while lighting and a scraper use 3% and 2%, respectively.
About the farm
The important thing to note in this case study is that the farm has a standalone ESB meter. That means the farmhouse is metered separately, and its electricity use cannot be included in the farm’s total electricity use calculation when applying for TAMS. Tom built a cubicle shed in 2018 and has 320m2 of suitable roof space available, facing either east or west.
His farm has a single-phase ESB connection with a smart meter installed. The farm’s maximum import capacity is 17kVA, which impacts the size of the solar PV system he can install. His annual electricity bill last year came to €13,067.22 plus VAT.
Tom’s solar PV system
After a farm energy consultation, which included supplying 12 months of electricity bills and conducting a site visit, it was decided that the optimal size of solar PV system for Tom was a 26.4 kilowatt peak (kWp) solar PV system.
This would consist of 60 440 watt glass-glass panels, requiring a roof area of 117m2.
Tom wants to use as much of the electricity he produces on his farm, so he is opting for a 15kWh battery system and will also need a 15kW inverter.
He wants to avoid an afternoon generation peak, and spread solar PV generation out as evenly as he can, so he will install half of his panels facing east, to coincide with morning milking, and the other half facing west, to coincide with evening milking.
Costs
Pre-grant, the solar PV system costs around €38,100 installed, along with €9,000 for the batteries and €795 plus VAT for an ESB NC7 application.
Tom applied for a TAMS III grant on the solar PV and battery system, which brought the total cost down to €18,000.
Returns
Tom’s solar PV system will generate 22,038kWh of electricity per year, the equivalent of 43% of the farm’s electricity use.
However, around 79% of that is used on the farm, with the remaining exported to the grid.
Around 4,628kWh is exported and he receives €0.185/kWh for this, resulting in an annual payment of €856 in the form of an energy credit.
This, combined with the displaced imported electricity, results in an annual saving of around €5,763 meaning the system would be paid off in three years and three months.
Emission savings
Once up and running, the solar PV system will save around eight tonnes of CO2 per year.
According to OpenSolar, over the 30-year lifetime of the panels, they would displace an estimated 237,542km worth of car emissions, 170 longhaul flights or be he equivalent to planting 1,527 trees.
The second case study is on a drystock and tillage farm in Offaly, with low electricity use. For the purposes of the case study, we’ll call the farmer ‘John’.
John finishes 60 Angus cattle. He also grows 110 acres of feed barley, beans and oats, which he uses for feed.
John stores 200t of green grain annually, which is treated and aerated with fans. While the electricity use on the farm is low, his house is connected to the same ESB meter, meaning that the solar PV system can be sized to cover both.
John’s electricity use
John uses 10,389kWh of electricity per year. Around 69% of that is from his farmhouse. Lighting accounts for 13%, while grain fans and treatment augers account for 11% and 7%, respectively.
About the farm
John has 550m2 of suitable roof space for solar PV, on top of a grain and machinery store built in 2012.
This store is located at the far side of the yard, however, and took some extra cabling when compared to Tom’s example.
John is also on a single-phase connection, but only has a maximum import capacity of 8kVA, which restricted his solar PV system size.
John also has a smart meter and, last year, his annual electricity bill came to €3,220 plus VAT.
John’s solar PV system
After the energy consultation, electricity bills supplied and site visit conducted, it was determined that the optimal solar PV system size for John was a 7.92kWp system.
This would require 18 x 440 watt glass-glass panels across a modest roof area of 35m2.
He has also opted for a 5kWh battery, although the grant doesn’t fully cover all of this due to the TAMS size restriction (limited to half of the size of the solar PV system). The system also includes a 5kW inverter and controller. He is facing all of the panels south, as he wants to maximise his total generation.
Costs
Pre-grant, the solar PV system and battery costs around €20,000 installed. As the system is below 10 kWh, he doesn’t have to apply for an NC7 connection but, rather, a free NC6 connection.
John secured a TAMS III grant on the solar PV and battery system, which brought the total cost down to €8,616.
Returns
John’s solar PV system will generate 6,188kWh of electricity per year, equivalent to 60% of the farm’s electricity use. However, around 72% of that is used on the farm, with the remaining exported to the grid.
Approximately 1,732kWh is exported and he receives €0.185/kWh for this, resulting in a payment of €320 in the form of an energy credit.
This, combined with the displaced imported electricity, results in an annual saving of around €1,836 meaning the system would be paid off in four years and seven months.
Emission savings
When up and running, the solar PV system will save around two tonnes of CO2 per year and displace an estimated 64,393km worth of car emissions, 46 long-haul flights, or be the equivalent to planting 414 trees.
