"The arms that you wield now are not such as your forefathers wielded; but they are infinitely more effective, and infinitely more irresistable" ~ Cymru Fydd leaflet, 1890

Sunday 24 May 2015

Kites v Screws

Not long after the announcement of the Holyhead 'kites' there was another renewables scheme hitting the news, this time in Radyr which is a few miles away from the centre of Cardiff.

Unlike the 'kites', the design for Radyr is one that doesn't make Wales a guinea pig for new and unproven technology. The design for Radyr features an Archimedes screw, except instead of needing power to lift water from a lower level to a higher level the water will drive the screw as it descends to a lower level.

Archimedes screws have been used for thousands of years, consequently this makes it far cheaper to implement which should mean a far cheaper price strike in order to pay back investors.

The EBC tells us that the screws will cost £2.6m which is just under ten times cheaper than the £25m the kites off Holyhead will cost. They also tell us that it will power 550 homes, the company behind it tell us that it has the potential for 391kW (compared with the initial 1500kW for the kites).

If these numbers stack up then it means the screws are a far more efficient and cost effective method of generating power than the kites.

Here's the first graph with the figures we know about. It's tricky to get the scale to look right with numbers this far apart so I used kilowatts (1 MW = 1000 kW) and the cost is in the thousands (£1m = £1000 * 1000).

Here's the graph again without the costs in order to clearly show the difference between the initial capacity and the number of houses powered. I should point out that 'number of houses powered' is one of those numbers people like to use in order to make it easier to imagine.

Since the cost of the kites scheme is around ten times the cost of the screws scheme then surely it would be better to fund ten projects using the screw principle rather than just one using the kites principle. Let's not get bogged down in who is funding what, let's just focus on what is better value for money.

Ten similar projects around Wales wouldn't all necessarily cost the same amount, they wouldn't necessarily all generate the same amount of power either. For all we know it might even be cheaper with a better return but given that it is far cheaper and far more efficient I know which route I would take.

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The recently announced plans to generate power at Radyr Weir using an Archimedes screw design are precisely the kind of...
Posted by Welsh not British on Sunday, 24 May 2015

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