This power figure sounds so absurd because both wind and solar projects deceptively advertise their maximum possible capacity - NOT their averaged output.
Meaning this array is designed to produce a maximum output that can satisfy these needs, but actually will produce around 20% of that figure. Wind comes out to about 18% of maximum capacity and you must also subtract maintenance and downtime.

LOL - lets pick a spot on the planet most likely to be covered in clouds, raining, smoggy, or other wise dark - and put solar panels there :-)

While I am not a fan of photovoltaic, The rain will keep the panels relatively clean. I think setting up some floating water wheels would be a more practical way of generating electricity.

Doing the maths on the power figure: 900,000kWh 1457.4 average sunshine hours in London / year (http://en.wikipedia.org/wiki/Climate_of_the_United_Kingdom) = 617.5 kW/h 4,400 panels = approx 140 watts / panel
Doing a quick google search for HIT solar panels shows that Sanyo\'s current model is 210 watts / panel Using that figure we can see the above equation would mean a 66% assumed efficiency based on average sunshine hours / year in London. Max output would be: 1,346,637 kWh, assuming average sunshine hours. If by max output (for the 20% comment above) you mean they calculate not on average sunshine, but on all daylight hours then it would seem reasonable that 4,400 solar panels rated at 210watts / panel could produce 900,000 kWh / year. OR Maybe they should put a nuclear reactor on the roof?

Good point, Todd. Let's not bother. Better to just burn more coal and rearrange the deck chairs as out Titanic sinks.

as they are sitting on top of a river, it makes sense to get power from that too...why isn\'t that in the plan, I wonder?

The size of the system is 1.1MW. In the UK the average generation per kW is 850kWh - often considerably higher. So, the expected generation is 900,000 kWh of electricity per year. This yield average is verified by The Department of Energy and Climate Change, and is based on extensive monitoring and field trials in the UK.

re; Mark-Toxic Pettit
While I agree with you. The River Thames in London is a tidal estuary with reversing flows and salt water. Part of the reason I like waterwheels over turbines for the job.
re; Kingsfield58
AGW is nonsense not a crisis. Check out a little historical perspective. http://neoconexpress.blogspot.com/2010/12/time-like-newsweek-predicted-coming-ice.html http://boldrepublic.com/climate_change.html http://www.sodahead.com/living/the-april-8th-1977-issue-of-time-magazine-entitled-how-to-survive-the-coming-ice-age-is/question-188977/?link=ibaf&q=times%2Bmagazine%2Bcover%2Bice%2Bage&imgurl=http://images.sodahead.com/polls/000188977/polls_untitled1_3317_661370_poll_xlarge.jpeg

Todd:
You evidently did not read the article carefully. THe power figure was expressed as kWh per year, which IS an average figure, not as kW.
Regarding hte other comments, I agree that it does make more sense to put water wheels of some kind in the river than to use soalr panels. Of course, they are not mutually exclusive. Why not do both?

re; Why not do both? comment David Charles Leithauser
Because the cost effectiveness of solar is really low.