Fashion Not Function

Posted on May 2, 2013 by Doug King

The ridiculous fashion for urban wind turbines is still showing no sign of abating with the erection of BSkyB’s new turbine at its West London studio complex. Perhaps the continuing political insistence for ineffective on-site renewable generation is to blame. It is not just successive national governments and fashion-following local planning regulations, but all too often we find that corporates are now playing to the populism of green. This collective disregard for engineering reality forces building owners and developers to pay for sub-optimal solutions and forces architects and engineers to try and justify the essentially unjustifiable in defence of what has been forced on them. AJ Footprint 25th April

If you ask a primary school class where we should build wind turbines, the answers usually range from “on top of hills” to “out at sea”, anywhere it is windy. By the time those children arrive at the final year of their architectural degrees the answer has often become “attached to my building as an icon”.

Unfortunately the very nature of buildings is to disrupt the smooth flow of wind which is essential for efficient energy generation. The increased friction due to surface roughness in urban areas reduces the potential power in the wind dramatically. At the height of BSkyB’s turbine, it is only half that of rural areas. In city centres the power available may be just 15% of the open country equivalent (full explanation here).

This location effect is generally accounted for by applying a capacity factor to the theoretical maximum generation of a turbine. The rule of thumb for UK wind power is to assume a capacity factor of 30%-35% for good onshore installations. The generation figures quoted for BSkyB indicate a capacity factor of just less than 15%. Thus the same turbine, at the same cost, could generate more than twice as much electricity if it was not shackled to a building. This doubling in output would more than offset the grid distribution losses (around 6%) to deliver the electricity back to BSkyB in West London.

Two identical Enercon E70 Turbines. The one on the left produces 3.5GWh whilst the one on the right produces 5.7GWh.

Two identical Enercon E70 Turbines. The one on the left produces 3.5GWh pa whilst the one on the right produces 5.7GWh pa. The difference is due to surface friction.

Apart from the very obvious branding potential, urban wind turbines have little going for them. It is time that politicians, national, local and corporate, stopped interfering and let engineers and architects make the best technical systems decisions for genuinely sustainable development.

Not enough wind for the Olympics

Posted on June 4, 2010 by Doug King

It is somewhat surprising to read the comment in The Times from Shaun McCarthy, Chair of the Commission for a Sustainable London 2012, that the Olympic Park wind turbine is to be scrapped because there is not enough wind on the site.

The Olympic wind turbine was announced in March 2008 in a blaze of glory. Since then has no-one bothered to check the Government’s Wind Energy Database now maintained by the Department of Energy and Climate Change? This clearly indicates that the location for the Olympic turbine is marginal for economic wind generation.

Generating electricity from the wind is critically dependent on the wind speed which is affected by location. Wind speed is dramatically reduced over cities due to friction with buildings dissipating much of the energy as turbulence. It would be unreasonable to expect the Stratford turbine to generate much more than about half that of an identical machine in open country.

Large wind turbines are a significant investment and if the generation potential of a site is poor then wind energy developers will look elsewhere. This may explain why the ODA has failed to find a new developer prepared to step into the breach after the preferred bidder for the turbine withdrew.

There are few other renewable technologies that can match wind power economically. One must hope therefore that the ODA rigorously enforces energy efficiency standards for the new buildings in order to reduce demand. This would be far preferable to wasting public money on expensive renewable technologies to offset 20% of unnecessarily high demand.

Don’t Mourn Windsave

Posted on March 21, 2010 by Doug King

Windsave, manufacturer of domestic wind turbine distributed through B&Q. went bust recently. Their Chief Exec blamed delays in implementing Government Policy, but I wonder…..

In their original marketing Windsave suggested their turbines would generate 1000kWh and provide “up to 30% of the electricity your household needs, based on average wind speeds and suitable locations”. For a £1,500 price tag this looked to a lot of people like a good deal, and many, including some reputable businesses were persuaded to part with cash.

Unfortunately the reality fell far short of the promises. A survey last year by the Energy Savings Trust found no instance of a micro wind turbine in an urban or suburban location which generated more than 200kWh per year. In some cases the control electronics consumed more mains electricity in the course of a year than was generated from the wind.

The failing was not Windsave’s alone; any rooftop turbine in an urban situation is in the boundary layer where airflow is turbulent and most of the energy has been dissipated through friction. It is simply not possible to generate any sensible amount of wind energy under these conditions.

Nevertheless Windsave seriously overstated the performance of their product. The public backlash started early, with numerous blogs by eco-enthusiasts describing woeful generation from their machines. Windsave were forced into serial retractions of their claims for performance and finally removed all performance information from their website.

If we mislead the public by overstating issues, when they discover the truth they will never afford us credibility again. It is crucial that we avoid doing this when it comes to debating renewables in the context of national energy policy.

Strata Tower

Posted on March 15, 2010 by Doug King

King_D_05-07-2010_010

The Strata Tower at Elephant & Castle featured heavily in the news last week. The developers are clearly very proud of their clever solution to addressing the London Plan’s requirement that 10% of a building’s energy be generated from on-site renewables. The building is to feature 3 turbines of 9m diameter for the princely cost of £1,300,000. However due to the small size and fixed direction these turbines are only expected to generate some 50MWh per year or just 8% of the building’s demand.

Let’s look at the alternatives:

King_D_22-06-2010_074

The well established Proven 15kW turbine has a rotor diameter of 9m and a single one of these costs about £50,000 to erect in a field. If sited in a suitably windy field you can expect to generate around 30MWh per year, but installations have been recorded that generate in excess of 50MWh. The same generation capacity as Strata for 4% of the cost!

On the other hand let’s consider Ecotricity’s turbine at the Ecotech centre in Norfolk.

King_D_07-06-2013_085

The first MW+ rated turbine in the UK this one weighs in at 1.5MW, and would cost about the same to install in today’s money as the Strata turbines. According to Ecotricity’s website this machine is generating 3,500MWh per year, 70 times as much as Strata is predicted to do!

This fad amongst local government to demand on-site renewable energy must stop; it’s eco-correctness gone mad! Rules like this force developers to waste money on eco-bling rather than investing in basic energy conservation and large scale renewables which can make a real difference.