16 April 2018 ~ 4 Kommentare

Concentrated Solar Power

Geskryf deur Nigel Naylor

The South African government has now signed contracts for the next set of IPP’s (Independent Power Producers) for renewable energy. This is excellent news as it is another step in the right direction for getting off fossil fuels.

The latest “package” consisted mainly of solar using photovoltaic, and wind turbines. But one of the more interesting ones is “Concentrated Solar Power” or CSP for short. But what is CSP? How can this benefit Orania?

CSP is a very simple concept and in its original form consisted of using parabolic mirrors or troughs to focus the sun, very much like as magnifying glass, onto a point of line (i.e. a tube) to generate steam, which then drives a steam, engine which then drives a generator, and then you have it: electricity! You can store heat energy much more sim ply and cost effective as opposed to storing electricity in an array of batteries! Much cheaper and much simpler. There are some drawbacks, namely you are generally using steam which is not so “with it” as with batteries. There is also some maintenance involved in running a steam engine.

To make CSP work efficiently you need four things:

  1. Space to put the solar collectors (i.e. solar troughs)
  2. Lots of sunshine
  3. No shortage of water
  4. The skill set to build and run a CSP plant

And this is where Orania comes in: it more than meets these four criteria.

There are at least three generations of CSP technology

  1. First Generation: Either heat water directly or oil which then is used to generate steam
  2. Second Generation: Here molten salts are used which in turn generates steam (The largest plant in the world generates 400MW!)
  3. Third Generation: Heat air to about 940 degrees centigrade instead of generating steam.[1] This generation is waterless.

There are several CSP plants in SA that are either completed or under construction[2]

The “father” of CSP was an American engineer named Frank Shuman who put CSP on the map by building a large industrial sized CSP plant along the banks of the Nile river outside Cairo.[3] This plant pumped 6,000 gallons of water to a head of 30 feet to irrigate cotton fields. Admittedly the plant consisted of 5 solar troughs that were over 204 feet long. This generated 60 – 70 horse power of steam energy. And the year was 1913. Frank Shuman even addressed the German Reichstag in 1913 and the German government was keen to use CPS in their African colonies. The British were also keen.

But then two disastrous things happened for CSP: the start of World War I and the engineers went back to help their countries in the war; and the advent of cheap oil/petrol. This killed CSP for the next 60 years or more.

But this is where Orania comes in: What is needed now are small “Domestic CSP Packs” or “Home Energy Centres”. Small farmers are ideal candidates to buy such Domestic CSP Packs because their Eskom electricity bill of say R2,600 per month consists of R2,000 line charges and admin charges, and this is before you have consumed a single unit of electricity.

There are some people experimenting with Domestic CSP Packs in South Africa. At the 2017 Kragdag two inventors (a mechanical engineer and a chemical engineer) had on display a prototype of their “Domestic CSP Pack” which used the reverse of the refrigeration cycle to power a small gas turbine that can generate up to 6 KW. This is a very high-tech design. It does not use water and is highly compact and portable. At that stage they had not yet got their prototype to production. But maybe it is now commercially ready.

But why not go low tech? If you have abundant space, plenty of water, and do not need mobility, then Domestic CSP Packs can be built very low tech, along the original lines of what Frank Shuman did. Shuman’s design was very simple and required very little maintenance.

A simple system is described by Nice University[4], which can be modified to drive a small steam engine/generator. In this system parabolic troughs are used to heat oil which is them pumped through a “Thermal Storage Tank filled with glass bricks. Modify the design to accommodate a heat exchanger which then generates flash steam which then drives a small stream engine.

The solar troughs can be easily and cheaply built using polished stainless-steel sheets.[5] The sheets cost about R500 each. You do not even need to do precise sun tracking as you can orient the troughs East-West and every week ort two do a minor adjustment on each trough for the seasonal change in sun’s inclination. Efficiency is not a problem, as it is cheap enough to simply add more panels and storage tank capacity.

As of yet I have not found a suitable source for small steam engines that are produced in SA. You can get them from overseas but importing them is quite expensive. But steam engines are tried-and-tested technology, and can be manufactured locally in Orania, thereby creating jobs for fitters and turners. There a plenty of plans available for steams engines on the internet.

Putting this altogether is a wonderful project for someone which can be converted to a great needed little business, and in the same time creating jobs with real useful skills. Everything will be local: no need to import solar panels and inverters. You can even wind your own generators. This supports the concept of localism 100%. And it saves on foreign currency. It is truly a solution whose time has come.

Imagine this great label: “Made in Orania. 100% South African”. This is one way to create a light industrial manufacturing capacity in Orania.

[1] https://www.youtube.com/watch?v=qj7m-sZRiaA

[2] https://www.nrel.gov/csp/solarpaces/by_country_detail.cfm/country=ZA

[3] https://renewablebook.wordpress.com/chapter-excerpts/350-2/

 

[4] http://wims.unice.fr/xiao/solar/

[5] http://wims.unice.fr/xiao/solar/diy-en.pdf

Deel/Stuur

4 Reaksies op “Concentrated Solar Power”

  1. Willem Fourie 23 April 2018 at 17:43 Permalink

    “Made in Orania. 100% South African”
    Uitstekend !!

    Met goedkoop krag kan ons (nog) groot projekte aanpak soos kragopwekking (reeds genoem), veredeling, vervaardiging, waterstof, selfs die myn van bitcoins.

    Mooi loop

  2. Andries Maritz 24 April 2018 at 12:44 Permalink

    Good day,

    Jolly good & encouraging. If this is manufactured in Orania, it will be great.
    All the best & good luck.
    Andries.
    New Zealand

  3. L E(Loutjie) du Toit 8 Mei 2018 at 06:35 Permalink

    Die oorbeklemtoning van die lae koste van eie opwekking bekommer my.
    Dit is wel waar dat die loopkoste laag is omdat daar nie brandstof verbruik word nie maar die aanvanklike kapitale koste is hoog wat beteken dat die kapitaal gedelg moet word oor ‘n tydperk en dit beteken dat daar periodiek opgedok moet word.
    Dan ook moet die onderhoud se koste nie onderskat word nie.

    Moenie my verkeerd verstaan nie, ek is ‘n baie sterk ondersteuner van die gedagte van ekovriendelike kragopwekking en ‘n laer afhanklikheid van ESKOM maar moenie die lae koste oorbeklemtoon nie want dit is net nie realisties nie.

    Sterkte met enige projel wat aangepak word. Ek hou dit fyn dop.


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