"From a techno-economic point of view, an alternating current overhead line is the most beneficial way of meeting the need for enhanced power transfer capability between the Republic of Ireland and Northern Ireland," a new report by experts from the UK, Belgium and Sweden has concluded. This is in spite of opposition from numerous landowners along EirGrid's proposed interconnector in counties Meath, Cavan and Monaghan.

Opponents to overhead lines lost a legal challenge to the project's planning permission in August. The Northern Ireland portion of the line has secured planning permission too.

Pylons

The international expert commission has found that better-looking pylons than the traditional steel lattice ones could be used at a slightly higher cost.

"Other alternatives exist, any of which would significantly delay enhancement of the network and add to the cost," it said.

Placing portions of alternating current cables underground similar to those in the rest of the network would be technically feasible only for short stretches of up to 10km, according to a report published by the Government this Tuesday.

'Experience does exist'

The "most credible" fully underground alternative would be a high-voltage direct current cable. While the technology is not yet common, "operational experience does exist and, within a few years, there will be at least four examples in Europe of comparable size," the experts said.

However, its use would at least treble the €120m investment in overhead lines to between €390m and €570m. "This would add significantly to the cost while providing only one notable benefit: that of hiding the line itself entirely from view," the report concluded.

Another difficulty it identified is that direct current requires converter stations at each end of the interconnector

The international expert commission noted that "more than 40 years of research has not led to a formal proof that electric and magnetic fields at extremely low frequencies may cause health risks", but could not rule them out either. In any case, underground cables still generate such fields, the report added.

Another difficulty it identified is that direct current requires converter stations at each end of the interconnector. This would make it difficult and expensive to use the interconnector to bring power-hungry industrial developments such as data centres to the border region as hoped, the experts warned.

Compensation

A separate report, also released by the Department of Communications, Climate Action and the Environment this Tuesday, examined compensation for landowners along the route of power lines.

Independent experts KHSK Economic Consultants compared the choice of payments available in Ireland through the ESB/IFA code of practice from 1985 or statutory instruments and practices in more than 20 other jurisdictions.

The report found so much variation in the approaches and levels of compensation paid that "it would not be meaningful to try to summarise the information given the extent of the differences".

However, the experts concluded that "there is no scientific basis for a claim that transmission lines cause health problems" and "limited evidence from numerous analyses of sales prices that transmission lines depress the value of the land over which they pass".

However, many countries have details laws to guide valuations for the loss of land and compensate disruption to farms during construction works.

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