Sharon Hindmarsh's List: science

• CSIRO claims game-changing solar discovery could end reliance on fossil fuels
• June 05, 2014
• THE CSIRO may have discovered a process that may end the reliance on fossil fuels for energy.
• The breakthrough was made at the CSIRO Energy Centre, Newcastle, where two solar thermal test plants featuring more than 600 mirrors are directed at two towers housing solar receivers and turbines.

• CSIRO energy director Dr Alex Wonhas said commercial solar thermal power plants around the world already use subcritical steam, operating at similar temperatures but at lower pressure.

  “If these plants were able to move to supercritical steam, it would increase the efficiency and help to lower the cost of solar electricity,’’ he said.

  “Supercritical steam is a breakthrough for solar energy and means that one day the sun could be used to drive the most advanced power stations in the world, currently only driven by coal or gas.

  “The supercritical solar steam would allow power stations of the future to use free, zero emission energy.

3 more annotations...

• Any type of low-grade heat source and also renewable energy sources, in the example that you have for a swimming pool today, essentially we are using solar energy as heat input,” he said. “But … you can use geothermal energy, biomass energy or waste heat going out of the stack of power plants and things like that.”

• Coal based power accounts for almost 41 % of the world’s electricity generation. Coal fired power plants operate on the modified Rankine thermodynamic cycle.The efficiency is dictated by the parameters of this thermodynamic cycle. The overall coal plant efficiency ranges from 32 % to 42 %. This is mainly dictated by the Superheat and Reheat steam temperatures and Superheat pressures. Most of the large power plants operate at steam pressures of 170 bar and 570 °C Superheat, and 570 ° C reheat temperatures. The efficiencies of these plants range from 35 % to 38 %. Super critical power plants operating at 220 bar and 600/600 °C can achieve efficiencies of 42 %. Ultra super critical pressure power plants at 300 bar and 600/600 °C can achieve efficiencies in the range of 45% to 48 % efficiency.
• Natural Gas fired (including LNG fired) power plants account for almost 20 % of the world’s electricity generation. These power plants use Gas Turbines or Gas Turbine based combined cycles. Gas turbines in the simple cycle mode, only Gas turbines running, have an efficiency of 32 % to 38 %. The most important parameter that dictates the efficiency is the maximum gas temperature possible. The latest Gas Turbines with technological advances in materials and aerodynamics has efficiencies upto 38 %. In the combined cycle mode, the new "H class" Gas turbines with a triple pressure HRSG and steam turbine can run at 60 % efficiency at ISO conditions. This is by far the highest efficiency in the thermal power field.
• The efficiency of nuclear plants is little different. On the steam turbine side they use the Rankine thermodynamic cycle with steam temperatures at saturated conditions. This gives a lower thermal cycle efficiency than the high temperature coal fired power plants. Thermal cycle efficiencies are in the range of 38 %.
• Diesel engines, large capacity industrial engines, deliver efficiencies in the range of 35 – 42 %.

2 more annotations...

• While Ultra-Supercritical power generation technology has been available as demonstration plant since the late 1990s it has only more recently become commercially available. There are no USC plants in Australia as yet. Most recent plants being built in China are USC and these plants deliver efficiencies around 42%. A number of ultra supercritical plants (ranging from 600-1,000 MW) have been built or are under construction in Europe, Asia and the USA.
• Advanced ultra-supercritical is the technology to improve the power generation efficiency by increasing the steam temperature and pressure of pulverised coal fired power generation. Japan is one country already leading the way in the use of Advanced Ultra-supercritical technology with several power stations deploying A-USC.