NBSLM03E (2010) Low Carbon Technologies and Solutions: Sections 14 - 16 N.K. Tovey (杜伟贤) M.A, PhD, CEng, MICE, CEnv • Low Carbon Conversion and Nuclear Power • Energy Conservation and Management in Buildings • Renewable Energy
NBSLM03E (2010) Low Carbon Technologies and Solutions N.K. Tovey (杜伟贤) M.A, PhD, CEng, MICE, CEnv • Renewable Energy • Solar Energy • Wind Energy
Renewable Energy - Overview • 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 ~ 50000 times the geothermal resource, and _~ 500000 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!!!
Solar Energy - Overview Solar Radiation Deliberate Collection Incidental Collection Focussed Architectural Design Unfocussed Flat Plate Collectors Parabolic or tracking Collectors with or without extra lenses/mirrors Biomass Water heating PV generators Passive Heating / Cooling Solar Ponds Hot Water / Electricity Generation High Temperature Steam Generation Central Solar Power Stations Greenhouses/ crop drying
Passive Solar Energy B • Passive Heating - Trombe Wall C B C E E D D Which flaps should be open/closed and when? A A Summer Operation A, E and D open, B and C closed Winter Operation A, C and D open, B and E closed
Passive Solar Energy - Cooling 23. Solar Energy (3) • Passive Cooling Damp Cloths Cooling by evaporation – also Swamp Box Air conditioner
Solar Thermal Energy Dual circuit solar cylinder indirect solar cylinder
Solar Thermal Energy Solar Pump Normal hot water circuit Solar Circuit Dual circuit solar cylinder
Solar Thermal Energy Solar Collectors installed 27th January 2004 Annual Solar Gain 910 kWh
Performance of 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 3 panel systems Some 2 panel systems captured twice the energy in summer months as others.
Performance of Solar Thermal Energy: 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
Performance of Solar Thermal Energy: Overall Efficiencies 2 panel 3 panel System Efficiency of 2 panel systems is generally higher than 3 panel systems
Performance of Solar Thermal Energy: The BroadSol Project Tilt Angle variations are not significant in region 0 – 45o in summer In winter optimum angles are between 45o and 90o Optimum orientation in East Anglia is SSW South West is almost as good as South
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 1.157 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 More Solar Energy is Collected if hot demand is higher !!! 1.164kWh 0.911kWh 1.157kWh 0.083kWh BS27: 15/05/2004
Solar Thermal Energy: Technical Issues requiring education when combined with traditional 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 15
Solar Thermal Energy: Technical Issues requiring education when combined with traditional central heating. 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
The Broadsol Project: Performance of Solar Thermal Energy Day 1 Day 2 Education of how to get best out of solar HW systems is needed. Need to adjust timing of central heating boiler over late Spring, Summer and early autumn. • On day 1, if boiler supplied hot water before solar gain was sufficient, top of tank would be heated to 55o C and reduce the solar gain by 21%. • On day 2, the loss would be negligible as temperature at top was already over 55oC. • If the store temperature throughout was as low as 20oC having been drawn off for a bath late on previous evening the loss in solar energy can approach 40%.
Solar Thermal Energy Output from a 2 panel Solar Thermal Collector
Solar Thermal Energy – Tubular Collectors Higher Reflectivity Lower Reflectivity
Solar Thermal Energy – Centralised Power Plants (CSP) Steam generation Incoming Radiation
Solar Thermal Energy – Centralised Power Plants (CSP) Solar 2 developed from Solar 1 at Bairstow California 10 MW Capacity
Solar Thermal Energy – Centralised Power Plants (CSP) PS10 Solar Tower Seville, Spain 11 MW Capacity
Solar Thermal Energy – Centralised Power Plants (CSP) Andasol Solar Power Station – Grenada Spain 50 MW World’s first commercial station – commissioned in November 2008
Solar PhotoVoltaic Cells Incoming Solar Radiation N type layer is doped with a valence 5 element – e.g. arsenic N type P type layer is doped with a valence 3 element – e.g. gallium P type Electrical Load
Solar PhotoVoltaic Cells 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 PhotoVoltaic Cells Solar Sundial for a location in southern UK Takes account of solar availability
Solar PhotoVoltaic Cells Photo shows only part of top Floor ZICER Building - UEA • Mono-crystalline PV on roof ~ 27 kW in 10 arrays • Poly- crystalline on façade ~ 6.7 kW in 3 arrays
Performance of Solar PhotoVoltaic Cells on ZICER Output per unit area Little difference between orientations in winter months Load factors Façade: 2% in winter ~8% in summer Roof 2% in winter 15% in summer
Performance of Solar PhotoVoltaic Cells on ZICER All arrays of cells on roof have similar performance respond to actual solar radiation The three arrays on the façade respond differently
Performance of Solar PhotoVoltaic Cells on ZICER 120 150 180 210 240 Orientation relative to True North
Performance of Solar PhotoVoltaic Cells on ZICER Arrangement of Cells on Facade Individual cells are connected horizontally Cells active Cells inactive even though not covered by shadow Cells connected vertically, only those cells actually in shadow are affected. All cells are inactive if shadow covers any cell 33 33 33 33
Solar PhotoVoltaic Cells – Small Scale Applications 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 Electricity Consumption in different Local Authority Areas • UK average is 4478 kWh per year at a cost of around £530 • Norwich average is 3535 kWh and is 6th best out of 408 Councils • Uttlesford average is 5884 kWh and is 396th out of 408 • NK Tovey’s average in a four bedroomed detached house is • <2250 kWh per year to 31st 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
Electricity Consumption in different Local Authority Areas Average consumption in Norwich is 3535 kWh per annum Mono-crystalline cells in UK generate ~ 80 – 100 kWh/m2 per annum Area required to be a net exporter overall ~ 35 – 40 sqm Poly-crystalline cells ~ 70- 80 kWh/m2 per annum Area required to be a net exporter overall ~ 45 sqm Thin film / Amorphous ~ 60 – 80 kWh/m2 per annum Area required to be a net exporter overall ~ 55 sqm
Average Domestic Consumption of Electricity Electricity Consumption in different Local Authority Areas • Consumption of Local Authority Districts in East Anglia • % electricity bill compared to National Average & Rank position in UK ex 408 Local Authorities In Norwich average household emits 1.9 tonnes of CO2 In Uttlesford 3.1tonnes of CO2
NBSLM03E (2010) Low Carbon Technologies and Solutions N.K. Tovey (杜伟贤) M.A, PhD, CEng, MICE, CEnv • Renewable Energy • Solar Energy • 16. Wind Energy
Wind Energy – Early Wind Devices • C 700 AD in Persia • used for grinding corn • pumping water • evidence suggests that dry valleys were “Dammed” to harvest wind
Wind Energy – Early Wind Devices Early Wind Turbines Charles Brush 1.25 MW Turbine in Vermont (1941) Gedser Wind Turbine, Denmark (1957) • First wind turbine built in 1887/8 by Charles Brush • see article about this wind turbine: http://www.windpower.org/en/pictures/brush.htm 12 kW Wind Turbine in Cleveland, Ohio (1888)
Wind Map of Western Europe: wind resource at 50m above surface Sheltered Open Coast Open sea Hills Dr J. Palutikof
Wind Energy – UK Wind Energy Resource Wind map of UK • The detailed picture is much more complex: • Topography • Distance from sea • Roughness • Obstacles • Information on wind speeds is available at 1km squares at 10, 25, & 45 m
Wind Energy Fundamentals A V 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.
Wind Energy Fundamentals V A Rated Output Cut in speeds Cut out speeds 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 Theoretically it is only possible to extract 59.26% of the Kinetic energy in the wind – This is known as the BETZ EFFICIENCY.
Wind Energy Fundamentals 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: Seehttps://netfiles.uiuc.edu/mragheb/www/NPRE%20498WP%20Wind%20Power%20Systems/Optimal%20Rotor%20Tip%20Speed%20Ratio.pdf
Wind Energy Fundamentals 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 • So output is proportional to • cube of velocity – i.e. doubling velocity > output power – 8 times • square of Blade Diameter Table shows output for different turbine sizes for a typical rated wind speed of 13 m s-1
Wind Energy Fundamentals Swaffham 2 Swaffham 1 Wind Speed variation with elevation above ground The wind speed increases logarithmically with elevation. Depends on roughness of terrain Increasing hub height increases power by 10%.
Wind Energy: Types of Wind Energy Converter 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 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 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