Presentation on theme: "Energy Blowing in the Wind N. Keith Tovey, M.A., Phd. CEng, MICE Acknowledgement: Dr Jean Palutikof for use of some of her slides."— Presentation transcript:
Energy Blowing in the Wind N. Keith Tovey, M.A., Phd. CEng, MICE Acknowledgement: Dr Jean Palutikof for use of some of her slides
Renewables Target 10% by 2010 for Electricity Generation 20% by 2020 The European Commission directive 2001: Member States are required to adopt national targets for renewables that are consistent with reaching the Commissions overall target of 12.1 per cent electricity from renewables by 2010. UKs indicative target is 10 per cent electricity. The Energy Review 2002
Early Wind Power Devices C 700 AD in Persia used for grinding corn pumping water evidence suggests that dry valleys were Dammed to harvest wind
Traditional Windmills American Homestead Windmill for pumping water Traditional English Windmill Spanish Windmills Note 7 in a cluster of 11
Development of Modern Turbines 1.25 MW Turbine in Vermont (1941) Gedser Wind Turbine, Denmark (1957)
Vertical Axis Machines Musgrove Rotor Carmarthen Bay 1985 - 1994 Darrieus Rotor - machines up to 4 MW have been built.
Other Wind Machines Savonius Rotors - good for pumping water - 3rd World applications Modern Multi-bladed water pumping HAWT.
Whats a modern wind turbine look like? Based on slide by Dr J. Palutikof The Ecotech Turbine avoids having a high speed gear box in the nacelle
Ecotech wind turbine Electricity per annum 3.9 GWh Annual homes equivalent 938 Displacement pa: CO 2 3000 tonnes SO 2 39 tonnes NO x 3 tonnes 67m 66m Dr J. Palutikof
We could make CO 2 targets with all new electricity generation from gas, but then 75% of our electricity will depend on supplies of gas from Russia, Middle East, or North Africa These figures assume we achieve 20% renewable generation by 2022 Energy Scenarios for UK and implications on CO 2 emissions.
Options for Electricity Generation in 2020 - Non-Renewable Methods
Options for Electricity Generation in 2020 - Renewable
Renewable Energy comparisons In the home - on average 25 - 40 sq m of PhotoVoltaic Cells would provide the equivalent of the electricity requirements of the house
The UK target for New Renewables set in 1993, was the building of 1500MW of new renewable capacity by 2000. How did we do?
Wind Energy in UK (end of 2001) Million Tonnes Carbon Dioxide Sulphur Dioxide Oxides of Nitrogen
Increase in Renewable Component for Electricity Generation to meet Government Target of 10% by 2010 Note: If we meet this target, it will hardly change the non-renewable component - i.e. the renewable deployment will just keep pace with increase in demand. Even if we do meet target (which is far from certain), our CO 2 emissions will rise following from closure of nuclear plant.
National Demand for Electricity also changes rapidly Prices paid by Suppliers vary dramatically over the day The introduction of NETA on 27th March 2001 had an adverse effect on economics of Renewable Energy and CHP
How are we going to meet these demands for electricity in the future? The Energy Review indicates 10% by renewables by 2010 and 20% by 2020. In order to get more than 10% of electricity from renewables by 2010 and 20% by 2020, build rates for the leading options would need to be at levels never before seen in the UK. Onshore and offshore wind would need to be installed at a rate of between 1-2 GW per year (i.e. 1000 - 1500 turbines the size of Swaffham every year). However, 1.5 GW and 1.6 GW of onshore wind was built in Germany in 1999 and 2000 respectively, and a further 1.2 GW was installed in the first eight months of this year (2001). Build rates of 1 GW per year were also seen Spain in 2000, and 600MW in Denmark in the same year.
Wind Energy in Europe Currently 13,000 MW from wind energy Overall EU target of 12% of energy (22% electricity) from renewables by 2010 - UK 10%
Wind Map of Western Europe: wind resource at 50m above surface Sheltered Open Coast Open sea Hills Dr J. Palutikof
Wind map of UK The detailed picture is much more complex: –Topography –Distance from sea –Roughness –Obstacles Dr J. Palutikof
Power in the wind Kinetic Energy in Wind = where = air density R = blade radius V = Wind Velocity. Because wind cannot come to standstill, only 59.26% is actually available - The Betz Efficiency Cut in speeds Cut out speeds Rated Output
Annual output depends of wind speed distribution Using a typical Wind Speed distribution gives a load factor of around 30% ~ 70 - 80% for fossil fuel stations and nuclear. Actual load factor does depend on Wind Speed Distribution Curve Turbine Rating Curve Prevailing Wind direction can vary significantly as shown by the two rosette plots from stations 150 km apart.
Effect of a forest of trees 20 m tall on output from turbine. At a hub height of 2.5 times trees and 15 tree heights downwind, 16% of energy is lost. Obstructions can affect output for significant distances downwind. Image obtained from www.windpower.org
Wind Speed variation with elevation above ground Swaffham Proposed Shipdam Depends on roughness of terrain Increasing hub height increases power by 10%. The wind speed increases logarithmically with elevation.
Spacing of Wind Turbines Interference between adjacent turbines occurs if spacing is less than 7 - 10 blade diameters - The Park Effect. With large arrays, 10 - 20% reduction in output will occur with a spacings of ~ 5 blade diameters. Because of square law of swept area, and larger turbines requiring greater spacing, the effective harvest of the wind is approximately the same irrespective of turbine size. However, costs will come down with fewer larger machines.
Distraction to drivers Danger to birds Radio/Television/Radar Interference Noise - mechanical, aerodynamic, …..infra-sound? Flickering - only relevant within buildings and then only in a precise orientation at selected times of the year. Danger of ice throw - not really a problem as other constraints will mean that a sufficient exclusion zone is present anyway Blade failure Aesthetics - one blade, two blades, three blades, Darrieus, Musgrove? Key Environmental Issues - some of main issues against
Ice can form but if this occurs when stationary, the machine will not start if it forms in operation, then the out of balance on blades is detected and the machine will stop in a few revolutions. Worse case scenario would cause ice to be thrown distances much less than the exclusion zone for noise.
In Denmark, a noise limit of 45 dB is set for isolated houses or 40 dB where several houses are affected. Two turbines close together would increase noise by about 3dB, while increase for 10 would be 10 dB Noise issues
Rule of thumb for noise Europe Distance to houses should be > 7 rotor diameters or ~300 m = 1000 ft. USA Dr J. Palutikof
Noise issues: Mechanical Aerodynamic Infra-sound Problem with high-speed gearboxes in fixed velocity machines. Not an issue with Swaffham/ proposed turbines at Shipdham. Maximum rotation speeds of gearboxless turbines are at a maximum 70% of normal wind turbines, and often much less - hence much less swish noise. This is a subject which is not fully understood - it is at a frequency which would NOT be detected by normal ground vibration. Noise Contours for a cluster of three turbines at Shipdham > 30 dB > 40 dB > 50 dB
Visual intrusion Some designs look better than others
.. and some arrays look better than others Dr J. Palutikof
Managing Environmental Issues Safety Issues Visual Issues Noise Issues Bird Strikes TV/Radio Interference First three can be managed using GIS procedures. Exclusion zones can be drawn for each feature type.
Digital Map of part of Norfolk Norwich is in bottom left hand corner Area: 105 sq kms A Strategic assessment of Wind Energy / Biomass Potential
Number of Turbines 65 Mean output 24.4 MW Area for Turbines 20.7 sq km Minimum exclusion zone (400m) around houses/towns. We could add other Planning exclusions etc - areas of particular landscape value etc.
Number of Turbines 33 Mean output 12.4 MW Area for Turbines 10.2 sq km Large exclusion zone (800m) around houses/towns.
Offsets the use of fossil fuels and consequential gaseous emissions of CO 2, SO 2, NOx, CO, NMHC etc. Arguements that fossil fuel power stations have to be kept ready in case wind drops are completely INVALID. Power stations running under lower load use less fuel and it is this which causes the emissions. Improves diversity of supply of electricity will become of increasing importance in future Is becoming technically mature unlike most other renewable technologies (other than energy from waste incineration and hydro) Is the most cost effective Renewable Option currently available, and will remain so for next decade + As electricity will used locally, reduces transmission losses. Key Environmental Issues of Wind Energy - positive aspects
Offshore wind energy - A solution? BUT Wind speeds are high Resource is enormous Visual intrusion is less than for onshore Its expensive Maintenance is problematic
Test location for offshore Wind Turbines in Denmark
Existing European offshore wind farms Dr J. Palutikof
Wind Energy has matured in the last decade. Significant developments are Wind Energy are likely in next decade both onshore and offshore if UK is to meet its targets. However, planning issues may continue to hinder development. In decade to 2000, 1100 MW were proposed, but less than 200 MW were built. We need to manage it to our benefit. Conclusions When questioned, typically 70 - 80+% of the public are in favour of Wind Energy, but the opponents are very vociferous.