The UK Government appears to be completely sold on the idea that offshore wind farms will solve our renewables woes, especially if they’re far enough out to sea, that’s not in anyone’s backyard.
They’ve set themselves long term renewables targets that they can’t hope to meet, but that’s not the fault of the underlying technology. So we’ve heard the positive spin for the dash for wind power, but what are the challenges to be faced?
Construction
Deep water offshore wind farm construction carries significant environmental and financial cost born of the location itself, and justifying this expense means building big, really big.
Modern offshore turbines will be larger than even their industrial sized onshore counterparts at well over 100m high, with a 120m rotor diameter and weighing in at 1000 tonnes. Add to this that they’ll be built in water 40 to 60m deep, and I’m sure you’ll agree that it’s a big structure.
Now imagine that you’re going to build 350 of them over 500 square kilometres of sea bed and you’ve got a working wind farm capable of generating about 1500 MW. That’s the same as a large conventional power station. Unfortunately, it only generates this much about half of the time it’s operating.
Life and Performance
The availability of sufficient wind is always an issue, it’s one of the reasons for favouring offshore applications where the wind is typically stronger and more consistent. Generally speaking, deeper water locations, up to 200km from the shore, produce better conditions than the current generation of farms. Out there weather conditions start becoming much harsher.
Salt spray, ferocious winds and a battering from high seas are conditions of which onshore facilities remain blissfully unaware. They reduce the life expectancy of equipment and maintenance teams alike. The technologies and practices required to overcome these problems are available in the Oil and Gas sector, but they all come at a price: offshore operation is neither a cheap nor easy option.
Electrical systems and salt water are not great bed fellows, and mechanical systems tend to react badly to these conditions too. You have to build robust structures where you can, and use expensive materials where you can’t. It’s a challenging environment for any engineering system and reliability will be a key to viability.
Assuming they’re working, we’ll have to collect the power from all 350 turbines and delivery it to the shore 200km distant before it can join the centralised grid where 10% of our power is wasted in transmission–a story for another day. These extra transmission losses over the kilometres of undersea cabling that’ll be required are going to dent performance. In my opinion this is one of the biggest problems for offshore generation, although transmission losses are something common to any centralised solution, most power stations aren’t so remote.
Support and Maintenance
We’ll need an extensive support infrastructure for deep water wind farms that’s akin to that in the Oil and Gas industries. That shouldn’t be a problem, we’ve been doing that for years, and as fossil fuels dwindle the jobs and some of the hardware currently employed in the North Sea could be transferred. But what about the transition, won’t new resources be required? We can’t wait until they become redundant; where will they come from?
Anyone with an offshore background will tell you how hard it is to keep deep water systems running. Bad weather takes it’s toll on both men and machinery, and there are times of year when you can just forget about any sort of maintenance. In all probability deep water wind farms will need support platforms with full time dedicated onsite maintenance teams, a significant additional cost and risk.
Is it possible that the environmental impact of such support activities may wreck the green credentials of the technology?
Economics
Whilst we’re comparing these two industries, I wonder how the value of oil extracted for $80 a barrel by a major rig compares to that of the power generated by one of these wind farms?
We should bear in mind that a large wind farm, like the ones proposed as part of the Crown Estates Round 3 licenses, is going to be an undertaking of similar proportion.
The fact is that I don’t have an answer for this, may be it’s something I should take a look at. If I ever do, I’ll make sure I post the results.