A common question is why every rooftop cannot simply be covered with solar panels instead of using “good farmland” for solar farms. The answer is complex, but in short it comes down to economies of scale.

For example, 50MW solar farm built on 200ac of flat, well-drained land near the grid costs far less than installing panels across the hundreds, or even thousands, of rooftops needed to generate the same amount of power.

A less frequently asked question is why not build solar farms on bogs, specifically cutaway bogs. These are areas of bogland once used for peat harvesting. They are typically flat, drained, degraded, and often close to electricity infrastructure, since peat was historically used for power generation.

Opponents of placing solar panels on bogs highlight concerns such as landscape suitability, emissions during construction, biodiversity impacts, the need to re-wet peatlands and the risk of disturbing underlying peat.

Despite these concerns, Europe’s largest solar farm built on cutaway bogland, the Timahoe North Solar Farm, a joint venture between ESB Networks and Bord na Móna, has just been officially opened and is exporting power to the grid.

The project shows that solar farms can be built successfully without encroaching on farmland.

Timahoe North Solar Farm

Located in Kildare, the Timahoe North Solar Farm covers an area of around 700ac and is the first large-scale solar project that both Bord na Móna and ESB have developed.

The project is located to the northwest of Kildare, 3km from Johnstownbridge, in the 2,000ac Timahoe North Bog, which forms part of the Allen Bog.

Last week, ESB and Bord na Móna welcomed Darragh O'Brien TD, Minister for Climate, Environment and Energy, to the site to officially launch the solar farm.

The 108MWp solar farm will generate enough electricity to power around 25,000 homes and is supported under the government’s Renewable Electricity Support Scheme (RESS).

The site has been subject to extensive large-scale commercial peat harvesting, which ceased 20 years ago. The harvested peat was once used to feed the now-demolished Allenwood power station.

The Derryiron-Maynooth 110 kV electricity line crosses through the overall Timahoe Bog. The site is very flat, low-lying, extensively drained and has a strong electricity grid, making it an attractive site for a solar farm without taking an acre of farmland out of production.

Peat challenges

While the site has many positive characteristics, it also presents challenges. During the planning process, 570 peat probes were taken, revealing peat depths of between 0.3 m and 4.5 m.

Piled foundations need to be driven into the peat, deep enough to support the panels.

The cut bog also has biodiversity considerations, but the planning application states that the locations for the panels were chosen to avoid environmentally sensitive areas within the bog.

Extensive works are also required around the site. According to the planning application, the development involved the removal of 63,400 m³ of peat and the felling of 115ac of forestry.

The excavated peat/spoil will be stored in seven pits and used as required for reinstatement landscaping works, with residual material placed in peat repositories.

From reviewing the planning application, it was unclear how much carbon emissions would be generated from excavating the peat and how much emissions would be saved by the solar farm.

More to come

In 2017, Bord na Móna and ESB announced a co-development agreement to develop solar farms in four locations in Roscommon, Offaly and Kildare, which will provide 500 MW of renewable energy, enough to power 150,000 homes per annum.

They assessed Bord na Móna’s 198,000ac land bank in strategic locations across the Midlands which are suitable for large scale solar energy projects. Some of these solar farms are now in development.