Podcast: Where to put your wind turbine

Wind turbine generator on house roof

Wind turbine generator on house roof

14 May 2013 by Sue Nelson

This week in the Planet Earth podcast, Alison Tomlin and Joel Millward-Hopkins of the University of Leeds describe a wind map they've developed to help UK homeowners and businesses decide whether or not to install a wind turbine.

To assist those who find text-based content more accessible than audio, a transcript of this recording is available below.

Sue Nelson: This time in the Planet Earth podcast, the untapped energy in big cities and how a new map can reveal its potential.

I'm Sue Nelson and I'm in Leeds on a bright and cloudy day with a hint of grey revealing the showers that may well appear later. In fact it is fair to say that Britain is well known for its weather - it can be sunny, wet and windy within the space of an hour, sometimes, and discussing the weather has almost become a national pastime, but researchers here are more interested in how windy it is because they've created a wind map of cities, including Leeds, that could help predict the best place to site a wind turbine. The wind map was produced by a team including Professor Alison Tomlin and PhD student, Joel Millward-Hopkins from the University of Leeds and they're with me now among some of the buildings that make up this city centre. Alison, how windy does it typically get in Leeds considering we are pretty much landlocked and not near the coast?

Alison Tomlin: Well it's quite difficult to provide a simple answer to that question because the wind across the city depends on various things. Leeds is quite a hilly area and has hills surrounding it and so that has an influence on the wind flows which come into the city, so at the moment we're at the top of a slight hill in Leeds and that gives us a slightly higher background wind. But the buildings within the city will have quite a large influence on the flows and so how windy is it in Leeds, it depends really where you are and influences of local buildings surrounding the area.

Sue Nelson: Will taller buildings produce more of a wind flow if you're, say, standing at the base of a tower block?

Alison Tomlin: Yes. I mean there has actually, unfortunately, been some incidents in Leeds where a very tall building led to extremely high gusts of wind around the building which actually has caused accidents and there has had to have been some re-engineering around that building to prevent gusty winds from putting pedestrians at risk, actually, as well.

Sue Nelson: OK then, Joel, how do you make a wind map then? Is it a question of putting... what instantly came to my mind was a device, an anemometer with lots of wind cups on to measure the wind speed or is it a little bit more complex than that? It is quite windy now actually isn't it?

Joel Millward-Hopkins: Yeah, that is a part of the process. Most of what we've been doing involves computer modelling, so we use information which tells you roughly what the wind speed is over a large area but this information doesn't take into account what's on the ground, it doesn't take into account the fact that the city is there. So what we then have to do is use lots of data which describes the shape of the city, so it's the height and the shape of every building, and from that we can work out the exact effects of these buildings on the flow. So then using some data from the British Atmospheric Data Centre and also the Met Office we can modify their data sources by considering what the city will actually do to the wind.

Sue Nelson: So what does this map actually physically look like then?

Joel Millward-Hopkins: It is quite boring to look at. It is a 3D matrix.

Sue Nelson: That doesn't sound boring, a 3D matrix, it sounds quite cool.

Joel Millward-Hopkins: OK, fair enough. Well we can make it look however we want really. So we have this 3D matrix which tells us where the wind speed is in every neighbourhood of the city, is what we call it, so that means a 250 metre by 250 metre square area, and then within that square we can calculate the wind speed at whatever height we want. So that is obviously a wealth of information and we can plot that in a 2D map if we wanted and so we could say well what's the wind speed at the highest building in each part of the city and then we can look at that and get a simple idea of... well at least an initial idea of how much wind potential is there in that city.

Sue Nelson: So when you looked at your results what did you find?

Joel Millward-Hopkins: Well, we found that there are sites suitable for wind turbines dotted, really, all over the city but you have to be very careful about making sure that your site is appropriate. So, in the city centre, for example, we have very disruptive wind speed because of all the tall buildings, but at the same time these tall building mean we have locations where the wind speeds are very high. If you have a building that is 100 metres high you have a big turbine mast, effectively, built for you. Then in residential areas where there has been a lot of turbines poorly sited in the past, we have found there are still locations suitable for turbines but you have to be careful really to pick a building that is a bit higher than the surrounding buildings otherwise you're going to get very significant sheltering of your turbine.

Sue Nelson: Alison, that's slightly counter intuitive isn't it because most people when you think about siting wind turbines you think of seeing the large scale ones in big open spaces, not in the middle of cities.

Alison Tomlin: That is true and in terms of the overall power generation, obviously, that is still a way forward but cities though are where many people live, they are very highly populated, there's a large amount of energy used in cities and most cities are trying to formulate plans to generate their own energy and to lower the carbon footprint of the urban area. So what we're saying is that actually micro generation, wind energy and solar energy are potential ways to do this and we're trying to help them out by saying, OK, this is the optimal way in which to use these strategies within your city. So, there is potential for cities to actually not import as much energy but to generate some for themselves.

Sue Nelson: You did several wind maps of several cities and not just Leeds.

Alison Tomlin: Yes, that's right. Initially we actually did several cities because there were so few data points to validate the model that we have to do as many cities as we could, so anywhere where we found anemometer data we used that to see if the model was actually working correctly. So we've looked at Leeds, we've looked at Nottingham, Edinburgh and recently we've actually we've done a map for London, literally this week.

Sue Nelson: So what are you going to do with all that information, Joel?

Joel Millward-Hopkins: Well, hopefully, we're going to make it available to anyone that can make use of it, so if you're a home owner or if you're a business or if you're a turbine company we would like there to be a way for these people to access the information and that will help this technology reach its potential, so the more people that can find out whether their house is suitable for the turbine the more likely there are for people to install these technologies.

Sue Nelson: So, potentially, in the same way that you have flood maps and you can put in your postcode and find out whether your house or land is at risk of flooding, you could in the future from the work that you have done put in your post code and see whether it it's a good place or not to have a wind turbine?

Joel Millward-Hopkins: Yeah, that's exactly right and hopefully you will be able to get some more information on the financial viability of that site, so is it going to be worthwhile from a financial point of view if you're installing a turbine there or are you going to back some money from them and if so, how much. So all these sorts of things, hopefully, in the long term will be able to implement into a simple tool.

Alison Tomlin: I mean there's two aspects to the feasibility of sites really for micro generation, one is I'm investing, I don't know, it could be £20,000 in a turbine, will I make enough energy to actually make back my capital investment, but also in making the turbine a lot of energy is used and materials are used which has a carbon footprint itself, so what you want to know is how many times we will actually pay back this carbon footprint? Is this a low carbon technology? And you find that actually, in the right places wind can be a very low carbon technology, so environmentally it is very positive.

Sue Nelson: Alison Tomlin and Joel Millward-Hopkins from the University of Leeds, thank you both very much. I'm Sue Nelson and you've been listening to the Planet Earth podcast from the Natural Environment Research Council.