Convection currents (wind and ocean waves), W Evaporation of water, heating of water & ice W Photosynthesis on land and sea, W Direct conversion to heat, W Long wave radiation to space W Tidal energy (moon and sun), W Geothermal energy, W Incoming solar energy, W Reflected short wave radiation, W Formation of fossil fuels, W Surface of the earth Atmospheric boundary Energy from the sun

FOSSIL FUELS NUCLEAR POWER INDUSTRY BUILT ENVIRONMENT TRANSPORT RENEWABLE ENERGY SOURCES ELECTRICITY

Hydro power systems

H Power from water If a mass M of water falls through a distance H, its loss of potential energy is MgH As it falls, the water could be made to do work, and in theory this work would also equal MgH In a hydro power plant, the water flows continuously, and the rate of doing work is is the mass flowrate

Hydro-electric power plant Water collects in the upper reservoir, flows through the turbine and is then discharged at low level. The rate of power production is ideally, and in practice, where η is the efficiency of the process. In a real system, energy will be dissipated as heat in the generator, the turbine and in the connecting pipelines Generator Turbine

Loch Sloy dam: 290 m head, 130 MW rated output

Augst-Whylen power station, River Rhine: 13 Kaplan turbines

Kaplan turbine runner, 8.4 m diameter, 20.5 MW

Pelton Wheel rated at 117 MW under a head of 686 m

Large Francis runner: hand finishing prior to delivery

Sectional drawing of modern Francis turbine installation showing the inlet valve and spiral casing, guide vanes, runner and draft tube. Direct shaft drive to the generator mounted above.

Underground power station: Ceannacroc, near Fort Augustus. 90 m head, 20 MW total power output from two turbines

Exposed pipework for hydro plant, Peru, S. America

Construction of Longyang dam, China. 178 m high, it will incorporate 3 turbines each rated at 320 MW

Hydraulic pumped storage In its generating mode, the plant operates as a conventional hydro power plant. But the generator can function as a motor, and the turbine as a pump. When demand for electricity is low, power may be taken from the grid to pump water into the upper reservoir, to act as an energy store for future use when demand for electricity is high. Generator Turbine Motor Pump

Cruachan pumped storage scheme, Argyll: 365 m head, 400 MW rated output; 4 Francis pump/turbine units

Aerial view of Cruachan site showing upper reservoir and dam. Administration and visitor centre is on the shore of Loch Awe below; power station is underground, some 400 m from the loch-side

Gravity and the tides Earth Moon Lunar cycle has a period of about 12h 25min Tidal range would be very small (about 0.5 m) if the earth were covered in water. But the land masses interfere, and create very large ranges in some parts of the world.

Global tidal resource, exploitable ‘at reasonable cost’, measured in GW

Single-effect barrage system with sluice gates (S) and turbines (T) SeaBasin T S DATUM SeaBasin z 1 Zz2z2 Mean level

Operation of a single-effect tidal barrage

La Rance tidal barrage system: rated power 240 MW

Proposed location for Severn barrage Length of barrage 16 km Peak tidal range exceeds 10 m Rated power output MW