Southern California Edison (SCE) announced the launch of a project to place 250 megawatts of solar panel capacity on company buildings in Riverside and San Bernardino counties.  The project hopes to add 1 megawatts of capacity each week of the 5 year project. The project is expected to cost nearly $900 million dollars, based on current estimates.  SCE points out that by scattering the installations throughout their service area and connecting directly to local sub stations, this project will reduce transmission related power loss and reduce stress on the regional grid. 

“Not only does this project bring carbon free energy, it also is likely to generate several million dollars a year in CO2 offset credits for SCE”, 4Offsets CEO Fred Weiss noted when interviewed on this news.  Assuming that these panels generate full power for 10 hours a day 300 days a year, which is likely in this desert location, the project will generate approximately 300,000 tons of offsets each year.  “When you add it up, it’s about $2 million worth of US voluntary credits or $12 million if credits are sold in Europe. This is a great example of how offsets can cause real change by providing investors with a better return”, Mr. Weiss added.

In 1970 at Odeillo, France, a solar furnace was built. Focusing the sun’s light, thousands of mirrors combine to produce temperatures up to 5,400 F. The furnace has applications in scientific research, can fire ceramics, and could even generate hydrogen. It was also in France, much earlier in 1949, that the first known modern solar furnace was built by Professor Felix Trombe. It was also built in the Pyrenees due to the almost 300 days of sunshine. Over fifty years old, it is back online and attracts 30,000 visitors annually. It is a dual reflection solar furnace with an array of 1,420 mirrors.Solar furnaces produce extremely high temperatures by using mirrors to parabolically reflect light onto a relatively small area of focus. This effect is similar, only on a larger scale, to the effect of focusing the sun’s rays through a magnifying glass to set fire to a piece of paper. (It’s also reputed to be the method that Archimedes used to burn Roman ships at the Siege of Syracuse.  (source: MIT)
While the heat of a solar furnace can melt steel, whether or not Archimedes’s Death Ray actually worked is unknown.

While some solar furnaces are used to refine metals, coat building materials, incinerate hazardous waste and fire ceramics, others are used for power generation. A type of solar furnace that generates electricity transfers the collected or focused energy of the sun and stores it in a substance for later use. Although water was originally used for a storage medium, liquid sodium is now used due to its higher capacity for heat retention. The stored energy can be used to boil water into steam to power turbines that generate electricity and can also be accessed even during darkness or cloudy days. Spain’s 15 MW Solar Tres Power Tower and 11 MW PS10 Solar Power Tower are based on this design. Other countries, including South Africa, have solar furnace based Solar Power Towers in the planning stages.

The PS10 tower is 40 stories high and is surrounded by an array of 600 heliostats or mirrors which are focused on water-filled plastic tubing at the top of the tower. Because of the reflected light, dust and water vapor in the air are illuminated into a pale fog which surrounds the tower. The tower is projected one day to provide enough power for the 600,000 inhabitants of the city of Seville, but is currently not up to that capacity at 11 Megawatts. Heliostats are being added and as they come online, capacity will increase. Abengoa, the company which owns the tower facility, and Solucar, the operator, report that the cost of generation is three times the cost of conventional power generation, but the tower produces no greenhouse gases, a fact that must be figured into the cost/benefit ratio. And as gas and oil prices rise and more solar furnace technology is adopted, construction and generating costs will no-doubt come more into line with conventional power plant costs. The subject of intense interest, PS10 is Europe’s first commercial Solar Power Tower operation. (http://news.bbc.co.uk/2/hi/science/nature/6616651.stm)

In the US, two Solar Power Tower projects were funded by the Department of Energy. Solar One and Solar Two, sited in the Mojave Desert in the Southwestern US, were limited successes and resulted in research which proved that liquid sodium is a much better medium for heat storage than water and that the Power Tower design was feasible. Spain’s Solar Tres was based on these projects and used Solar Two as a partial model for its tower design.