Solar photovoltaic power (PV) has been installed on a wide range of farm businesses in the last four years. This is now a proven technology with the ability to reduce energy bills and cut the carbon footprint of food production. It is a particular advantage where the majority of the electricity can be used in the business.

Changes in support levels for small scale PV

As part of the government policy to encourage the production of renewable energy, payments are made for each kWh of electricity produced from a renewable technology.  These payments are called Renewable Obligation Certificates (ROCs).  In the case of solar PV systems up to 50 kW size the payments were reduced from 1 October 2015 to 3 ROCs for each kWh of electricity produced.  Payments were further reduced from 1 October 2016 to 2 ROCs, a payment of around 7.8 pence/kWh of electricity produced by the system.  This reduction will have the effect of reducing the payback time for an investment in PV.

CAFRE’s experience of PV

In 2012 there was growing interest in PV, yet there was a degree of caution among potential installers about the claims made for the output of systems.  The College approached several farmers who had installed PV in 2012 and 2013 and obtained agreement from them to monitor the output of electricity from their systems.  The results from the monitoring showed that the systems performed better than the prediction given by the official Standard Assessment Procedure calculation.  This gave confidence in the technology for other potential installers.

 A 50 kW PV system has been installed on the roof of the new Food Incubation Centre on Loughry Campus.  The electricity generated is used for a range of food processing activities.  This use of PV electricity gives a sustainable system, as all the energy generated can be used in food processing during the working day.  The output data from this system will be recorded and used along with that from the Monitor Farms to evaluate the profitability of PV systems.

Economics of PV

The output of a system is usually calculated by the Standard Assessment Procedure (SAP), a government approved system.  This estimates the output of electricity depending on the southwards orientation, angle to the horizontal and other factors.  The table below gives a few examples of the SAP output figures in kWh per year for each kW of installed capacity.

Tilt of collector South SE / SW North
30º 858 822 584
60º 791 742 400
Vertical 597 564 297

For each kW of installed capacity at 30º to the horizontal and either SE or SW the electrical output is estimated to be 822 kWh.  Allowing for a decline of 0.7% each year over 20 years this gives an average output over the lifetime of the system of 764.5 kWh. 

If daytime farm electricity costs 13.5 pence per kWh, ROCs are worth 7.8 pence per kWh and electricity sold to the grid is worth 4.01 pence per kWh.

For one kW of panels:

Using 100% on the farm each unit is worth (13.5 + 7.8) pence totalling £163

Selling 100 % each unit is worth (4.011 + 7.8) pence totalling £90

A typical farm 12 kW capacity system will cost £12,000, or £1,000 per kW.  With the annual output range from £90 to £163 the simple payback times will range from 6.1 to 11 years.  Typically an intensive enterprise such as a pig unit will use most if not all of the electricity produced on the farm and have a short payback time.

Carbon footprints

With the ongoing concern about climate change and global warming it is important for the agri-food industry to reduce the amount of greenhouse gases produced through the chain from production to consumption.  PV is one of the renewable energy technologies that will reduce the carbon footprint of our food.  For each kWh of electricity generated by conventional power stations using fossil fuels there is on average 0.52 kg of carbon dioxide released to the atmosphere.  This additional gas contributes to global warming and climate change.

A typical farm 12 kW PV system will generate around 9,600 kWh each year, saving 5 tonnes of emissions to the atmosphere.

Farm scale PV

A number of companies are currently involved in developing solar farms in Northern Ireland.  These farms will cover several hectares in area with a typical size being a 5 MW farm based on around 12 ha of land.  The rows of panels cover around one third of the land area with vegetation able to grow in between the rows.  These solar farms have a positive impact on biodiversity, providing habits for a wide range of insect, bird and mammal life.

They represent an opportunity for land owners to obtain a dependable income for their land over a twenty year period or more.  It involves committing the area of land to energy production and having it fenced off for security purposes. 

While the economics could be attractive there are various issues that need to be considered.  The land will not be eligible for Basic Farm Payments or other support measures as it is deemed not to be in agricultural production.  In addition there may be issues in the future should the land change ownership.  If it is not being used for agricultural purposes then it may not qualify for tax benefits when it is sold or transferred.

For further information contact: David Trimble, Renewable Energy Technologist, CAFRE at

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