Clean Power

Published on August 5th, 2011 | by Breath on the Wind


That “Other” Solar Tower Technology

August 5th, 2011 by  

Several days ago I wrote of the Giant Arizona Solar Tower (and confusing names) that is trying to find funding. Brightsource is the company that is presently building Solar Towers with an entirely different technology.

Brightsource Solar Tower Project

The History started perhaps with Egyptians using mirrors to illuminate the interiors of tombs. They needed nothing more than a polished metal mirror and a slave who hopefully had a hat. The mirror would have to move in two ways to follow the sun through the sky. In those times, the main energy source was human power. From that time, various mechanical mechanisms have been substituted to track the sun. The name Heliostat itself is over 250 years old. Today electricity is king. Modern heliostats are moved by motors which, in turn, allow the sun to provide electricity.

The technology of Solar Power Towers is dependent upon heliostats. Fields of them, all reflecting the sun’s light to a central tower. There, the highly concentrated sunlight produces equally high temperatures. The heat is then used in an otherwise conventional Rakine Cycle thermal power plant to generate steam that runs a turbine to generate electricity. The first of these systems were built in the early 80’s in Russia, Europe Japan and slightly later in the US. Salts with higher melting temperatures can contain more sensible heat storage and were being used for their efficiency advantage over simply heating water.

Heliostats for Solar Tower

Refinements: Brightsource has announced that the theory is now ready for the next construction project and calls the technology “LPT solar thermal energy system.” They have also added two refinements. Thermal (Rankine cycle) power plants need cooling. Because the technology is often used in deserts where water is scarce they have added air cooling. Hours of sunshine would normally limit the supplied power but thermal heat storage allows plant operation into the night.

duel tank heat storage

The storage system used is a two-tank molten salt storage system. In two tank systems, heat is stored in the tanks at two temperatures. A heat exchanger between them is used to heat up or cool down another medium like water or oil. By adding such a storage system, the hours of operation are increased.

The capacity factor of a power plant is the actual plant energy production compared to the energy a plant could produce running 24/7 at maximum power. This is significant to the overall energy expected from a power plant. A 100-MW geothermal plant with a 90% capacity factor would have an advantage over a 100-MW coal plant with only a 75% capacity factor if the cost of both were equal.

Photovoltaics are around 19% in Arizona. Wind and solar towers without energy storage have capacity factors around 25%. Energy storage can increase the capacity factor of Concentrated Solar Power (CSP) plants like the solar power tower to over 60%.

Advantages: CSP technologies have an advantage over photovoltaics as they are already producing heat which suggests a technologically simple method of energy storage. The other CSP technology being built around the world is the solar trough collector. The Brightsource LPT solar thermal power-generating technology can reach higher operating pressure and temperature levels. This adds to increased efficiency and economic value.

Future refinements in such technologies will certainly be heavily dependent upon new developments in thermal storage. Eventually, we may see more use of chemical heat storage for extremely long, even seasonal, storage systems.

Source: Brightsource

Photo Credits:

  1. Brightsource solar tower projectby Flickr user pgegreenenergy
  2. Heloistats for solar tower by Flickr user langalex
  3. Other photos: Brightsource

Check out our new 93-page EV report, based on over 2,000 surveys collected from EV drivers in 49 of 50 US states, 26 European countries, and 9 Canadian provinces.

Tags: , , , , , , , , ,

About the Author

We share this World; its past, present resources and our combined future. With every aspiration, the very molecules we use for life are passed to others through time and space so that each of us may be considered a Breath on the Wind. This part of the world's consciousness lives in NYC; has worked in law, research, construction, engineering; has traveled, often drawn to Asia; writes on Energy and Electric Vehicle issues and looks forward to all your comments.   "If you would persuade, you must appeal to interest rather than intellect." -- Benjamin Franklin

  • Pingback: BrightSource Going Big on Energy Storage | CleanTechnica()

  • Pingback: Geologically Active Japan as an Energy Resource | CleanTechnica()

  • Breath on the Wind

    The article makes little mention of the many examples of this technology in prototype or under full scale construction. Thanks for the link.

  • Pr_coms

    How innovative is this technology if they can’t differentiate its so called name from the Solar Tower technology that precedes it?!

    • Breath on the Wind

      The confusion may have been created by the driving force behind the “previous” solar tower technology. Mr Davey from Australia. See the comments in that article at:

      “innovation” has to involve technology. Naming the technology involves media and sometimes hype. The relationship is not a logical one and so there may not even be aclose coorelation.

  • Pingback: BrightSource Planning 2nd Huge Solar Power Plant in California, Bigger One (+ Top Solar Power Stories) | CleanTechnica()

  • Steven Gould

    If they call it Helios One, I’m going to start building an underground bunker asap

  • Anumakonda Jagadeesh

    Excellent post on history of ‘Solar Tower” Technology.

    Dr.A.Jagadeesh Nellore(AP),India
    Wind Energy Exp[ert

    • Breath on the Wind

      Thanks for your ever generous comments

  • Yes, there’s plenty that could prevent the 2600-foot tall solar tower from being built in Arizona. The “project” at this stage is really just a concept — EnviroMission needs to secure financing for the $750 million construction, conduct environmental impact and engineering feasibility studies, acquire the land, and get approval from the Arizona Corporation Commission.

    But the concept is both compelling and mind-boggling — the capacity factor is much higher than with other renewables, water use and operating costs are minimal, and it works in any weather and at night. I’ve long said that we are desperate for more innovative ideas; this is certainly one.

    • Breath on the Wind

      You can read about the confusion of names between these two solar tower technologies, the Enviromission Solar updraft tower project, the pros and cons of the updraft tower technology and alternative options here:

      • Pr_coms

        EnviroMission is developing Solar Tower technology in La Paz Arizona – it is solar thermal updraft technology – air heated by solar radiation will drive turbines to generate clean electricity more importantly the technology does not use water in the electricity generation method. More examination of all resources involved in electricity generation should be mandatory to disclose the REAL cost of energy. EnviroMission was first to market to identify the technology as Solar Tower – this is self evident in the most basic fact check. Power on!

Back to Top ↑