1 NBS-M016 Contemporary Issues in Climate Change and Energy Renewable Energy 23. Solar Energy 24. Wind Energy N.K. Tovey ( 杜伟贤 ) M.A, PhD, CEng, MICE, CEnv Н.К.Тови М.А., д-р технических наук Energy Science Director CRed Project HSBC Director of Low Carbon Innovation N.K. Tovey ( 杜伟贤 ) M.A, PhD, CEng, MICE, CEnv Н.К.Тови М.А., д-р технических наук Energy Science Director CRed Project HSBC Director of Low Carbon Innovation Lecture 1 Wind Energy Supplementary Solar

2 22. Renewable Energy Renewable energy sources may be divided into three categories 1) Solar - a) direct b) indirect - e.g. wind, waves., biomass 2) Lunar - tidal 3) Geothermal Together direct and indirect solar sources are ~ times the geothermal resource, and _~ times the lunar source. See section 4 of the notes for the magnitudes of the different sources. Energy from Waste often included as Renewable Energy. Sometimes such energy is linked with biomass. ?? an alternative Energy Source. PET COKE is often used in the Cement industry and also Iron and Steel as an alternative fuel. BUT it has a higher CARBON FACTOR than even coal!!!

3 23. Solar Energy (1) Solar Radiation Deliberate CollectionIncidental Collection Unfocussed Focussed Greenhouses/ crop drying Flat Plate Collectors PV generators Water heating Solar Ponds Hot Water / Electricity Generation Parabolic or tracking Collectors with or without extra lenses/mirrors High Temperature Steam Generation Central Solar Power Stations Passive Heating / Cooling Architectural Design Biomass

4 Passive Heating - Trombe Wall 23. Solar Energy (2) E C B A D E C B A D Winter Operation A, C and D open, B and E closed Summer Operation A, E and D open, B and C closed Which flaps should be open/closed and when?

5 Passive Cooling 23. Solar Energy (3) Damp Cloths Cooling by evaporation – also Swamp Box Air conditioner

6 23. Solar Energy (4) indirect solar cylinder Dual circuit solar cylinder

7 23. Solar Energy (5) Normal hot water circuit Solar Circuit Dual circuit solar cylinder Solar Pump

8 23. Solar Energy (6) 8 Annual Solar Gain 910 kWh Solar Collectors installed 27th January 2004

9 23. Solar Energy (7) Output from a 2 panel Solar Thermal Collector

Solar Energy (8) Tubular Collectors Higher Reflectivity Lower Reflectivity

Solar Energy (9) Centralised Solar Power Incoming Radiation Steam generation

Solar Energy (10) Centralised Solar Power Solar 2 developed from Solar 1 at Bairstow California 10 MW Capacity

Solar Energy (11) Centralised Solar Power PS10 Solar Tower Seville, Spain 11 MW Capacity

Solar Energy (12) Centralised Solar Power Andasol Solar Power Station – Grenada Spain 50 MW World’s first commercial station – commissioned in November 2008

Solar Energy (13) Photovoltaics P type N type Electrical Load Incoming Solar Radiation N type layer is doped with a valence 5 element – e.g. arsenic P type layer is doped with a valence 3 element – e.g. gallium

Solar Energy (14) Photovoltaics Mono - crystalline ~ 80 – 100 kWh / sqm / annum Thin film ~ 60 – 70 kWh / sqm / annum Poly - crystalline ~ 60 – 80 kWh / sqm / annum Typical test bed efficiencies 15 – 16% for mono-crystalline - theoretically up to 30%, but practical efficiencies after inversion in real situations ~ 10 – 12%

Solar Energy (15) Photovoltaics Solar Sundial for a location in southern UK Takes account of solar availability

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19 Mono-crystalline PV on roof ~ 27 kW in 10 arrays Poly- crystalline on façade ~ 6.7 kW in 3 arrays ZICER Building Photo shows only part of top Floor 19

20 Load factors Façade: 2% in winter ~8% in summer Roof 2% in winter 15% in summer Output per unit area Little difference between orientations in winter months Performance of PV cells on ZICER 20

21 All arrays of cells on roof have similar performance respond to actual solar radiation The three arrays on the façade respond differently Performance of PV cells on ZICER 21

Orientation relative to True North 22

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24 Arrangement of Cells on Facade Individual cells are connected horizontally As shadow covers one column all cells are inactive If individual cells are connected vertically, only those cells actually in shadow are affected. Cells active Cells inactive even though not covered by shadow 24

25 Ways to Respond to the Challenge: Technical Solutions: Solar Photovoltaic Photovoltaic cells are still expensive, but integration of ideas is needed. Output depends on type but varies from ~70kWh to ~100kWh per square meter per year. Average house in Norwich consumes ~ 3535 kWh per year

Average Domestic Consumption of Electricity UK average is 4478 kWh per year at a cost of around £530 Norwich average is 3535 kWh and is 6 th best out of 408 Councils Uttlesford average is 5884 kWh and is 396 th out of 408 NK Tovey’s average in a four bedroomed detached house is < 2250 kWh per year to 31 st March 2010 [50% of National Average] a reduction of 25% compared to on 18 months ago. On average Norwich – consumers will be paying 79% of National average Uttlesford – consumers will be paying 131% of National average

Average Domestic Consumption of Electricity kWh% costRank kWh% costRank Norwich3,53579%6Breckland5,028112%312 Cambridge4,05090%80 East Cambridgeshire 5,118114%326 Peterborough4,22294%116Forest Heath5,174116%336 Ipswich4,34997%159Babergh5,252117%343 Waveney4,41799%181South Norfolk5,347119%358 Broadland4,618103%231Suffolk Coastal5,371120%360 North Hertfordshire 4,645104%240 South Cambridgeshire 5,498123%374 Huntingdon4,655104%243North Norfolk5,641126%385 Great Yarmouth4,699105%252Mid Suffolk5,723128%390 St Edmundsbury4,869109%280 King's Lynn and West Norfolk 5,731128%393 Fenland4,899109%287Uttlesford5,884131%396 Consumption of Local Authority Districts in 1080, % cost compared to National Average Rank position in UK out of 408 Local Authorities In Norwich average household emits 1.9 tonnes of CO 2 In Uttlesford 3.1tonnes of CO 2

Supplementary Solar Slides from presentation given by N.K. Tovey on 5 th February in Newmarket

Technical Solutions: Solar Thermal Energy Up to 15 installations were monitored at 5 miute intervals for periods up to 15 months Mean Monthly Solar gain for 11 systems Some 2 panel systems captured twice the energy in summer months as other 2 panel systems.. 3 panel systems 29

The Broadsol Project Three panel systems captured only 13% more energy compared to two panel systems Effective use is not being made of surplus in summer 30

Measured Overall System Efficiencies System Efficiency of 2 panel systems is generally higher than 3 panel systems 2 panel 3 panel 31

32 Tilt Angle variations are not significant in region 0 – 45 o Optimum orientation in East Anglia is SSW South West is as almost as good as South 32

More Solar Energy is Collected when Hot Water use is greater. Sky became hazy at ~ 11:00 Substantial hot water demand at 13:30 Normal heat loss from tank if there had been no demand shown in black kWh extra heat collected. Note: further demand at 18:30 leading to further solar collection. Even more solar collection would have been possible had collector been orientated SW rather than S BS27: 15/05/ kWh 0.911kWh 1.157kWh0.083kWh 33

Technical Issues requiring awareness raising: Solar Thermal Energy captured when combined with central heating Tank with small residual hot water at top of tank in early morning If Central Heating boiler heats up water – less opportunity for solar heating. Zone heated by solar energy 34

Technical Issues requiring awareness raising: Solar Thermal Energy Tank with small residual hot water at top of tank in early morning No hot water provided by central heating boiler. Gain from solar energy is much higher. More solar energy can be gained if boiler operation is delayed. Boiler ON/OFF times should be adjusted between summer and winter for optimum performance 35

Peak Cell efficiency is ~ 9.5%. Average efficiency over year is 7.5% Mono-crystalline Cell Efficiency Poly-crystalline Cell Efficiency Efficiency of PV Cells Peak Cell efficiency is ~ 14% and close to standard test bed efficiency. Most projections of performance use this efficiency Average efficiency over year is 11.1% Inverter Efficiencies reduce overall system efficiencies to 10.1% and 6.73% respectively 36

Technical Solutions: Integrated use of PV generated energy Inverters are only 91% efficient Computers and other entertainment use DC. Power packs are inefficient LED lighting can use DC Need an integrated approach – houses with both AC and DC with heat recovery from central inverter/rectifier? 37

38 Benefits from Feed In Tariffs: From 1 st April 2010 Technolog y Scale installations 01/04/10 – 31/03/11 (p/kWh) **** installations 01/04/11 – 31/03/12 (p/kWh) **** installations 01/04/12 – 31/03/13 (p/kWh) **** PV <4kW (new build) PV<4kW (retrofit) PV4-10kW PV10–100kW PV100kW– 5MW PV Stand alone systems Tariffs for Generation In addition it is proposed that electricity exported will benefit from an export tariff which is currently proposed at 3p*** per kWh Revised Tariffs as published by DECC on 1 st February 2010

Solar worked example A solar system is designed to make a house self sufficient in space heating requirements throughout the summer from March onwards. Graph shows the profile of solar radiation throughout the day. The collector is 40% efficient. The mean external temperature is 6.9 o C and the heat loss rate is 300 W o C -1. If the thermostat setting is 20 o C and incidental gains amount to 1.5 kW, what area of collector is required? What volume of heat store is required if water is used operating over a range of 25 o C? Daily solar energy provision = 2 x ( ) * 3600 * 0.4 = MJ / sqm / day

Daily solar energy provision = MJ / sqm / day Balance (base) temperature = 20 – 1500 / 300 = 15 o C Heat Requirement = 300 * (15 – 6.9) = 2430 Watts Over a day 2430 * = MJ are required. Area of collector = / = 45 sq m To find the storage volume required it is necessary to replot the graph to indicate the total actual amount of solar energy available each hour – i.e. multiply values by 45 and 0.4 Incidental gains Solar worked example – part 2 Collector area efficiency

Between midnight and 06:00 and 18: :00, no solar energy. Heat withdrawn from the store to make up for the heat loss of 2430 watts. = 2430 * 12 * 3600 / = MJ In addition, partial withdrawal: –(2430 – 180) = 2250 Watts between 06: :00 and 17:00 -18:00 –(2430 – 900) = 1530 watts between 07:00 – 08:00 and 16:00-17:00. –i.e. a total of 2* ( ) * 3600/ = MJ Total Store = = MJ/day 1 cu metre water weighs 1000 kg so operating over 25 o C 1 cu metre stores * 25 = MJ Total volume of water required = / = 1.26 cum.

42 NBS-M016 Contemporary Issues in Climate Change and Energy Wind Energy 23. Tidal Energy N.K. Tovey ( 杜伟贤 ) M.A, PhD, CEng, MICE, CEnv Н.К.Тови М.А., д-р технических наук Energy Science Director CRed Project HSBC Director of Low Carbon Innovation N.K. Tovey ( 杜伟贤 ) M.A, PhD, CEng, MICE, CEnv Н.К.Тови М.А., д-р технических наук Energy Science Director CRed Project HSBC Director of Low Carbon Innovation Lecture 1Lecture 3 Lecture 2

43 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

44 First wind turbine built in 1887/8 by Charles Brush see article about this wind turbine: Early Wind Turbines Charles Brush 1.25 MW Turbine in Vermont (1941) Gedser Wind Turbine, Denmark (1957) 12 kW Wind Turbine in Cleveland, Ohio (1888)

45 Wind Map of Western Europe: wind resource at 50m above surface Sheltered Open Coast Open sea Hills Dr J. Palutikof

46 Wind map of UK The detailed picture is much more complex: – Topography – Distance from sea – Roughness – Obstacles

47 Wind Energy: Fundamentals (1) Energy from wind is obtained by extracting KINETIC ENERGY of wind. Kinetic Energy = 0.5 mV 2 where V is velocity of wind (m s- 1 ), m (kg) is the mass of air flowing through an area each second = density x area x distance travelled in 1 sec =  A V where  is the density of air, and A is the cross sectional area of air flowing through This represents the theoretical energy available in the wind. A V

48 Theoretically it is only possible to extract 59.26% of the Kinetic energy in the wind – This is known as the BETZ EFFICIENCY. A V Modern Wind Turbines can achieve a practical efficiency of around 75% which means that a maximum overall efficiency of around 40 – 42% can be achieved. Cut in speeds are around 4 – 5.5 ms -1 Rated output is achieved at around 12 ms -1 Cut out speed ~ 22 – 25 ms -1 Wind Energy: Fundamentals (2) Rated Output Cut in speeds Cut out speeds

49 Optimum Efficiency is obtained with a Tip Speed Ratio i.e. the velocity of the blade tip is several times that of the wind. Typically TSR is around 6 but it does depend on number of blades. It is approximately given by where n is number of blades This means that smaller machines will need to turn faster that large machines to achieve the optimum TSR For further details: See ms/Optimal%20Rotor%20Tip%20Speed%20Ratio.pdf ms/Optimal%20Rotor%20Tip%20Speed%20Ratio.pdf Wind Energy: Fundamentals (3)

50 The Park Effect The efficiency will be reduced if there is turbulence and if turbines are placed too close to each other a significant reduction in output can occur - e.g. Wind Farms in California in 1980s Wind Energy: Fundamentals (4) Spacing (blade diameters) Array Size5D7D9D 2 x x x x x

51 So output is proportional to cube of velocity – i.e. doubling velocity > output power – 8 times square of Blade Diameter blade diameter (m) output (kW) blade diameter (m) output (kW) Table shows output for different turbine sizes for a typical rated wind speed of 13 m s -1 Wind Energy: Fundamentals (5)

52 Wind Speed variation with elevation above ground Swaffham 1 Swaffham 2 Depends on roughness of terrain Increasing hub height increases power by 10%. The wind speed increases logarithmically with elevation. Wind Energy: Fundamentals (6)

53 May be categorised 1) by type of energy provided. a) electrical output b) mechanical output - pumping water etc. c) heat output - as a wind furnace - mechanical power is fed to turn a paddle in bath of oil or water which then heats up e.g. device near Southampton. ii) by orientation of axis of machine a) horizontal axis - HAWT b) vertical axis - VAWT iii) by type of force used to turn device a) lift force machines b) drag force machines Wind Energy: Types of Wind Energy Converter

54 Low-solidity devices: Wind turbines with small numbers of narrow blades, such as modern electricity generating wind turbines with one, two or three blades. These operate as LIFT MACHINES Wind Energy: Types of Wind Energy Converter (2) High-solidity devices: Wind turbines with large numbers of blades have highly solid surface areas, e.g. the water pumping devices on farms These operate as DRAG MACHINES

55 Plane of Rotation Blade Motion +u Tip Speed Ratio = u / V Blade Angle Lift Drag Relative Wind Angle of Attack Wind blows in this direction Wind speed = V Chord Line Air mass on top of blade has to move faster causing a reduced pressure and creating lift Principles of Lift and Drag View looking vertically downwards from above onto tower

56 Traditional Windmills operate as Drag Machines American Homestead Windmill for pumping water Traditional English Windmill Spanish Windmills Note 7 in a cluster of 11

57 Other Drag Wind Machines Savonius Rotors - good for pumping water - 3rd World applications Modern Multi-bladed water pumping HAWT.

58 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

59 Ecotech wind turbine – Swaffham 1 Electricity per annum 3.3 GWh Annual homes equivalent ~ Displacement pa: CO tonnes Based on load factor of 25%. Swaffham 2 ~ 4.2 GWH generated ~ 1050 homes ~ 2300 tonnes of CO 2 displaced | Based on load factor of 27%. 67m 66m

60 Vertical Axis Machines Musgrove Rotor Carmarthen Bay Darrieus Rotor - machines up to 4 MW have been built.

Basic - very approximate method Annual output = capacity * load factor * 8760 Load factor in UK varies from around 15 – 16% - e.g. Blood Hill to 40%+ in Orkney with an average of around 27% More accurate method requires knowledge of wind speed distribution and turbine characteristics 61 Predicting Output from Wind Turbines Range of Wind Speeddays - < >232

62 Annual output depends of wind speed distribution Using a typical Wind Speed distribution gives a load factor of around 30% ~ % 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. Predicting Output from Wind Turbines – Other issues

Range of Wind Speed (m/s) daysmean wind speed (m/s) output (kW) - < > Predicting Output from Wind Turbines – Worked Example – part 1 Step 1: Work out mean wind speed Read of Graph for output at each mean wind speed

64 Predicting Output from Wind Turbines – Worked Example – part 2 Range of Wind Speed (m/s) daysmean wind speed (m/s) Output (kW) Generated in period (MWh) (1)(2)(3)(4) from graph (5) = (2)*(4)*24/ < > Total Output = MWh per annum – Maximum Possible = 1500 * 8760 So Load Factor = / = 30.0% If carbon factor = 0.52, saving in CO 2 = * 0.52 = 2050 tonnes

Range of Wind Speed (m/s) daysOutput (kW) Frequency * output (1) (2)(3) from graph (5) = (2)*(4) - <1 2.19% % % % % % % % % % % % >230.55%0 0 Summation Predicting Output– Worked Example – using frequency information the same example! Note: If frequency is given, then it is not necessary to work out the MWh for each wind speed separately. To work out output = * 24 *365/1000 = MWh as before Load Factor = /1500 = 30%

Simple Financial Analysis Cost of Onshore wind installations £800 - £1200 per installed MW So a 1500 kW machine would cost around £ Under new Feed In Tariff, prices of generation will be around 9.7p per kWh So annual income from turbine would be * *1000 = £ Simple payback would be achieved after / = 3.92 years

67 Effect of a forest of trees 20 m tall on output from turbine. At a hub height of 2.5 times height of tree and 15 tree heights downwind, 16% of energy is lost. Obstructions can affect output for significant distances downwind. Image obtained from Factors affecting Wind Energy Output

68 Distraction to drivers In past was often cited in early days, but with wind turbines more common, this is of little problem. Swaffham Wind turbine is adjacent to A47. Danger to birds Does depend on location, but RSPB reserve is next to oldest wind farm in UK at Burgar Hill, Orkney. In worst cases up to 3 birds may be killed per installed MW per year – or around in total in UK. This compares with killed on the roads. Radio/Television/Radar Interference May be a problem, but siting of key radio installations may need to be modified. Key Environmental Issues - some of main issues against (1)

69 Noise - mechanical, aerodynamic Most mechanical noise arises from gearbox. In some installations there is no gearbox. Noise at nacelle can be 100 – 103 dB, but falls of very rapidly Key Environmental Issues - some of main issues against (2) 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

70 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 Key Environmental Issues - some of main issues against (2) Ice can form 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. See following link for incident which occurred in December Ice from blades – December 2008

71 Blade failure – rare these days Did occur with 1.25 MW Vermont Machine in 1941 – blade flew several hundred metres Many early California Wind Turbines had significant blade failures/ damage (~85) at some site, but this was much and effect of Park Effect. Musgrove Rotor in Carmarthen Bay was damage by a blade failure Aesthetics - one blade, two blades, three blades, Darrieus, Musgrove? Key Environmental Issues - some of main issues against (1) Blade Failure – February Click here to see video of blade failure in Denmark

72 How many Blades? See for advantages / disadvantages of different number of bladeshttp:// ThreeTwo one

73 More pictures of 2 and 1 – bladed machines

74 Examples of Offshore Wind Middelgrunden, Copenhagen Scroby Sands, Norfolk Offshore Wind

75 Current UK Wind Energy Capacity On April 12 th 2010 the total installed capacity was 4138 MW There were a further 2045 MW under construction 7466 MW consented, but experience suggests that only 75% will actually be built 9706MW in planning of which ~50% might be built A further MW would be needed to meet target of 33 GW by 2020

Projected Wind Energy Generation from current projects Some projects approved in 1998 have not been built and other have been dropped – Scenario assumes 75% of those approved are actually built and 50% of those in planning. An average 27.5% Load Factor is assumed

77 See for information on new developments in windhttp://wwww.bwea.com/pdf/offshore/movingup.pdf