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60 The Kentish Flats wind farm in the Thames Estuary...

See Its 30 Vestas V90 wind turbines have a total peak output of 90 MW, and the predicted average output was 32 MW (assuming a load factor of 36%). The mean wind speed at the hub height is 8.7m/s. The turbines stand in 5m-deep water, are spaced 700m apart, and occupy an area of 10 km2. The power density of this offshore wind farm was thus predicted to be 3.2 W/m2. In fact, the average output was 26 MW, so the average load factor in 2006 was 29% [wbd8o]. This works out to a power density of 2.6 W/m2. The North Hoyle wind farm off Prestatyn, North Wales, had a higher load factor of 36% in 2006. Its thirty 2 MW turbines occupy 8.4 km2. They thus had an average power density of 2.6 W/m2.

- ... shallow offshore wind, while roughly twice as costly as onshore wind, is economically feasible, given modest subsidy. Source: Danish wind association windpower. org.

- ... deep offshore wind is at present not economically feasible.

Source: British Wind Energy Association briefing document, September 2005, Nevertheless, a deep offshore demonstration project in 2007 put two turbines adjacent to the Beatrice oil field, 22 km off the east coast of Scotland (figure 10.8). Each turbine has a "capacity" of 5MW and sits in a water depth of 45 m. Hub height: 107 m; diameter 126 m. All the electricity generated will be used by the oil platforms. Isn't that special! The 10 MW project cost £30 million - this price-tag of £3 per watt (peak) can be

Region depth 5 to 30 metres depth 30 to 50 metres area potential resource area potential resource

North West



2 000


Greater Wash





Thames Estuary











Table 10.7. Potential offshore wind generation resource in proposed strategic regions, if these regions were entirely filled with wind turbines. From Dept. of Trade and Industry (2002b).

compared with that of Kentish Flats, £1.2 per watt (£105 million for 90 MW).

It's possible that floating wind turbines may change the economics of deep offshore wind.

60 The area available for offshore wind.

The Department of Trade and Industry's (2002) document "Future Offshore" gives a detailed breakdown of areas that are useful for offshore wind power. Table 10.7 shows the estimated resource in 76000 km2 of shallow and deep water. The DTI's estimated power contribution, if these areas were entirely filled with windmills, is 146kWh/d per person (consisting of 52 kWh/d/p from the shallow and 94 kWh/d/p from the deep). But the DTI's estimate of the potential offshore wind generation resource is just 4.6 kWh per day per person. It might be interesting to describe how they get down from this potential resource of 146kWh/d per person to 4.6kWh/d per person. Why a final figure so much lower than ours? First, they imposed these limits: the water must be within 30 km of the shore and less than 40 m deep; the sea bed must not have gradient greater than 5°; shipping lanes, military zones, pipelines, fishing grounds, and wildlife reserves are excluded. Second, they assumed that only 5% of potential sites will be developed (as a result of seabed composition or planning constraints); they reduced the capacity by 50% for all sites less than 10 miles from shore, for reasons of public acceptability; they further reduced the capacity of sites with wind speed over 9 m/s by 95% to account for "development barriers presented by the hostile environment;" and other sites with average wind speed 8-9 m/s had their capacities reduced by 5%.

61 .. .if we take the total coastline of Britain (length: 3000 km), and put a strip of turbines 4 km wide all the way round... Pedants will say that "the coastline of Britain is not a well-defined length, because the coast is a fractal." Yes, yes, it's a fractal. But, dear pedant, please take a map and put a strip of turbines 4 km wide around mainland Britain, and see if it's not the case that your strip is indeed about 3000 km long.

- Horns Reef (Horns Rev). The difficulties with this "160 MW" Danish wind farm off Jutland [] are described by Halkema (2006).

When it is in working order, Horns Reef's load factor is 0.43 and its average power per unit area is 2.6 W/m2.

62 Liberty ships -

- ... fossil fuel installations in the North Sea contained 8 million tons of steel and concrete - Rice and Owen (1999).

- The UK government announced on 10th December 2007 that it would permit the creation of 33 GW of offshore capacity... [25e59w].

- ... "pie in the sky". Source: Guardian [2t2vjq].

63 What would "33 GW" ofoffshore wind cost? According to the DTI in November 2002, electricity from offshore wind farms costs about £50 per MWh (5p per kWh) (Dept. of Trade and Industry, 2002b, p21). Economic facts vary, however, and in April 2007 the estimated cost of offshore was up to £92 per MWh (Dept. of Trade and Industry, 2007, p7). By April 2008, the price of offshore wind evidently went even higher: Shell pulled out of their commitment to build the London Array. It's because offshore wind is so expensive that the Government is having to increase the number of ROCs (renewable obligation certificates) per unit of offshore wind energy. The ROC is the unit of subsidy given out to certain forms of renewable electricity generation. The standard value of a ROC is £45, with 1 ROC per MWh; so with a wholesale price of roughly £40/MWh, renewable generators are getting paid £85 per MWh. So 1 ROC per MWh is not enough subsidy to cover the cost of £92 per MWh. In the same document, estimates for other renewables (medium lev-elized costs in 2010) are as follows. Onshore wind: £65-89/MWh; co-firing of biomass: £53/MWh; large-scale hydro: £63/MWh; sewage gas: £38/MWh; solar PV: £571/MWh; wave: £196/MWh; tide: £177/MWh.

"Dale Vince, chief executive of green energy provider Ecotricity, which is engaged in building onshore wind farms, said that he supported the Government's [offshore wind] plans, but only if they are not to the detriment of onshore wind. 'It's dangerous to overlook the fantastic resource we have in this country. . . By our estimates, it will cost somewhere in the region of £40bn to build the 33 GW of offshore power Hutton is proposing. We could do the same job onshore for £20bn'." [57984r]

- In a typical urban location in England, microturbines deliver 0.2kWh per day. Source: Third Interim Report, Among the best results in the Warwick Wind Trials study is a Windsave WS1000 (a 1-kW machine) in Daventry mounted at a height of 15 m above the ground, generating 0.6 kWh/d on average. But some microturbines deliver only 0.05 kWh per day - Source: Donnachadh McCarthy: "My carbonfree year," The Independent, December 2007 [6oc3ja]. The Windsave WS1000 wind turbine, sold across England in B&Q's shops, won an Eco-Bollocks award from Housebuilder's Bible author Mark Brinkley: "Come on, it's time to admit that the roof-mounted wind turbine industry is a complete fiasco. Good money is being thrown at an invention that doesn't work. This is the Sinclair C5 of the Noughties." [5soql2]. The Met Office and Carbon Trust published a report in July 2008 [6g2jm5], which estimates that, if small-scale

Figure 10.8. Construction of the Beatrice demonstrator deep offshore windfarm. Photos kindly provided by Talisman Energy (UK) Limited.

Figure 10.9. Kentish Flats. Photos © Elsam (elsam. com). Used with permission.

turbines were installed at all houses where economical in the UK, they would generate in total roughly 0.7kWh/d/p. They advise that roof-mounted turbines in towns are usually worse than useless: "in many urban situations, roof-mounted turbines may not pay back the carbon emitted during their production, installation and operation."

63 Jack-up barges cost £60 million each.

Source: I estimated that we would need roughly 50 of them by assuming that there would be 60 work-friendly days each year, and that erecting a turbine would take 3 days.

Figure 10.9. Kentish Flats. Photos © Elsam (elsam. com). Used with permission.

Further reading: UK wind energy database [www.bwea. com/ukwed/].

11 Gadgets

One of the greatest dangers to society is the phone charger. The BBC News has been warning us of this since 2005:

"The nuclear power stations will all be switched off in a few years. How can we keep Britain's lights on? ... unplug your mobile-phone charger when it's not in use."

Sadly, a year later, Britain hadn't got the message, and the BBC was forced to report:

"Britain tops energy waste league."

And how did this come about? The BBC rams the message home:

"65% of UK consumers leave chargers on."

From the way reporters talk about these planet-destroying black objects, it's clear that they are roughly as evil as Darth Vader. But how evil, exactly?

In this chapter we'll find out the truth about chargers. We'll also investigate their cousins in the gadget parade: computers, phones, and TVs. Digital set-top boxes. Cable modems. In this chapter we'll estimate the power used in running them and charging them, but not in manufacturing the toys in the first place - we'll address that in the later chapter on "stuff."

The truth about chargers

Modern phone chargers, when left plugged in with no phone attached, use about half a watt. In our preferred units, this is a power consumption of about 0.01 kWh per day. For anyone whose consumption stack is over 100 kWh per day, the BBC's advice, always unplug the phone charger, could potentially reduce their energy consumption by one hundredth of one percent (if only they would do it).

Every little helps!

I don't think so. Obsessively switching off the phone-charger is like bailing the Titanic with a teaspoon. Do switch it off, but please be aware how tiny a gesture it is. Let me put it this way:

All the energy saved in switching off your charger for one day is used up in one second of car-driving.

The energy saved in switching off the charger for one year is equal to the energy in a single hot bath.


Figure 11.1. Planet destroyers. Spot the difference.



Figure 11.1. Planet destroyers. Spot the difference.

Figure 11.2. These five chargers -three for mobile phones, one for a pocket PC, and one for a laptop -registered less than one watt on my power meter.

Admittedly, some older chargers use more than half a watt - if it's warm to the touch, it's probably using one watt or even three (figure 11.3). A three-watt-guzzling charger uses 0.07 kWh per day. I think that it's a good idea to switch off such a charger - it will save you three pounds per year. But don't kid yourself that you've "done your bit" by so doing. 3 W is only a tiny fraction of total energy consumption.

OK, that's enough bailing the Titanic with a teaspoon. Let's find out where the electricity is really being used.

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Renewable Energy Eco Friendly

Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

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