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Power Technology

South Africans Revolutionize Concentrated Solar Power With Mini Heliostats 106

Taffykay writes: Concentrated Solar Power (CSP) offers significant benefits, but it's often prohibitively expensive. Paul Gauché from Stellenbosch University in South Africa hopes to change that with Helio 100, a series of 'plonkable' miniature heliostats that require no installation or concrete, and offer solar energy that's cheaper than diesel. The Guardian reports: "Helio100 is a pilot project with over 100 heliostats of 2.2 sq meters each, generating 150 Kilowatts (kW) of power in total – enough to power about 10 households. According to Gauché, the array is already cheaper than using diesel, the go-to fuel for most companies and businesses during regular power outages in the country.
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South Africans Revolutionize Concentrated Solar Power With Mini Heliostats

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  • by turkeydance ( 1266624 ) on Monday August 24, 2015 @07:33PM (#50384745)
    and i know, i know , i know....
  • ...

    So, what is Google's RE?

  • by Maxo-Texas ( 864189 ) on Monday August 24, 2015 @07:41PM (#50384791)

    Imagine if these cut diesel fuel usage in africa by 30% over the next 5 years.

    • by ihtoit ( 3393327 )

      I dunno, is the roof of a tractor trailer big enough to hold a thirty by seventy foot solar array? I can see it working for houses, ten joined terraces has got to be larger than that in roof area, even flat roofs (I'm going by my shoebox which is typically sized for a 1960s midterrace town house in England, at 70 feet deep and twelve wide including the garage - with that kind of efficiency you'd only need to cover 30% of existing roofs to meet the entire domestic power demand), but then you've got infrastru

      • That's gonna need the help of another South African, you know, the one who makes the batteries that can store the electricity so it can be used in and by moving objects? Model T coming up in 5... 4...
        • Of just use solar when it's day and not raining. Otherwise use diesel as normal. If you are wise, take a portion of the savings and funnel it into batteries.

      • In some places, more diesel is used for electricity than is used for vehicles.

        • by DarenN ( 411219 )

          Like, for instance, in South Africa, where electricity delivery is very unreliable and most businesses have diesel generators as backups. This also goes for large portions of the continent where power delivery is very unreliable for a host of reasons. (this was aimed at the GP, in case anyone's wondering.)

      • by dbIII ( 701233 )
        Less consumption makes supply easier.
        This is a situation where consumption is low so roof space is not an issue - plus the cost of covering the roof space is far more and issue than available space.
  • No details (Score:5, Informative)

    by Michael Woodhams ( 112247 ) on Monday August 24, 2015 @08:11PM (#50384907) Journal

    TFA is lacking in details about how this works, but if you follow the link you get to a Guardian [theguardian.com] article which is lacking in details, but links to the projects website [sun.ac.za] which excessively uses gratuitous Javascript and is lacking in details.

    They talk about "plonkability" - that the mirror structures can just be plonked on the ground and will 'just work'. This suggests to me that somewhere in their system is some intelligence or calibration which is able to notice where each mirror is relative to the target and adapt its pointing accordingly. Their photos show the target tower having two rectangular surfaces pointed towards the mirrors. I suspect the plane white surface is there to aid mirror pointing calibration in some way, but I don't know.

    • by tsotha ( 720379 )
      I've always wondered if this could be done with GPS. If you know where you are and where the tower is, you can figure out what angle the mirror should be to point at the tower. That would get you close enough for some kind of autocalibration if you put the right kind of sensors on the tower and had a link to the mirror controller.
      • You'd use differential GPS. Wikipedia says this has accuracy of 10cm in the best case. Whether that is good enough for this application I'm not sure. Given that affordability is a big part of their goal, if they were taking this approach they'd not attach a GPS to each mirror, but rather have two receivers that they used for a callibration stage and then wouldn't be needed again unless something shifted. You'd need to know orientation as well as location for the mirrors.

        I doubt this is what they're doing, b

        • by AmiMoJo ( 196126 )

          There are low cost passive systems for angling solar panels towards the sun. Perhaps this is a development of that. They rely on heat causing expansion for automatic alignment.

          • by tsotha ( 720379 )
            I don't see how you get from there to pointing at a specific spot. What angle the mirror needs to be relative to the sun is going to depend on exactly where it is relative to the tower.
    • by NakNak ( 1148087 )
      More detail at the (South African) Mail & Guardian [mg.co.za], published a couple of days before that Guardian piece, which confirms the intelligence is built into each unit.

      "The heliostats are effectively smart robots that 'know the angle between the sun and the tower, depending on the time of day, and know where the sun is with respect to the tower. They each know this independently'".
  • Bullshit (Score:4, Informative)

    by ChrisMaple ( 607946 ) on Monday August 24, 2015 @08:17PM (#50384915)
    100 units of 2.2 sq meter each has a total solar input of 220 kW peak, roughly. They're claiming 150 kW. That's 68% efficiency, which nobody has achieved.
    • Absolutely no data in the original article.

    • Who, other than NASA, cares about efficiency, when you can buy panels for $0.28/watt [sunelec.com]?
      • Efficiency is important in any place where land is limited.
    • They're claiming this enough to power 10 households, which would be 15 kW per house... Someone clearly dropped a decimal or doesn't understand units. 15.0kW or 150kWh/d is plausible. Math or GTFO:

      Google used ((862 heliostats) * (6 m**2 / heliostat)) to generate 890 kWe. Source [google.org]

      890kWe / 5172 m**2 =~ 172 watts per square meter.

      Helio100 is using ((100 heliostats) * (2.2 m**2 / heliostat)) == 220 m**2. Assuming it's really 15.0 kWe, that comes out to 68 watts per square meter. The difference can easily be

      • 15kW per house? This is Africa, not America - typical usage in Europe is 4kW per house. It is probably 40W per house in Africa. Only 0.001% of houses have A/C.

        And, as pointed out elsewhere, most electricity comes from Diesel in Africa (The rest mostly from Hydroelectric).

        • by Anonymous Coward

          Holy crap can you be any more wrong?

          Firstly *SOUTH AFRICA* - it is a small country on the tip of Africa that shares very little in common with most of the rest of Africa. Secondly no most of our electricity does not come from Diesel or Hydroelectric, the bulk of our power comes from coal. Third, no, the general household usage here is probably at least 1kW at a minimum if not more.

          Seriously please just refrain from commenting on stuff that you clearly know nothing about.

        • 15kW per house? This is Africa, not America - typical usage in Europe is 4kW per house. It is probably 40W per house in Africa. Only 0.001% of houses have A/C.

          And, as pointed out elsewhere, most electricity comes from Diesel in Africa (The rest mostly from Hydroelectric).

          I'm South African. You're wrong. Usage per house varies from between 1kW to 4kW. Running a house on 40W basically lights a room dimly for an hour. Also, we have AC everywhere - I certainly have AC at home, at work and in my Mercedes-Benz.

          Oh, wait! You thought Africa was a poor *country*... silly you.. *South Africa* is a country in *Africa*, and we're more first-world than third-world.

          Idiot.

          • If you're actually using around 2 kW on average (seems quite atrocious to me), it seems that you'd probably save a lot of money by running your AC from rooftop solar (unless there's some kind of glitch like red tape or extortionist pricing in the local market). Besides the power, you'd be shading the building somewhat.
            • I personally (my home) use around 1kW on average. The problem with using solar is that the payback period (in SA, anyway) from electric bill savings exceeds the expected lifetime of the panels and related kit needed to set it up.

              • In that case, you PV install prices must be truly atrocious if you can't amortize it even with modern equipment. It's either that, or your electricity is ridiculously cheap.
          • When did South Africa join NATO?

            http://www.nato.int/cps/en/nat... [nato.int]

            Oh, it didn't.

            http://www.nationsonline.org/o... [nationsonline.org]

            First world is NATO aligned countries, second world is Soviet aligned countries, and third world is non aligned countries. You don't rise into the first world by improving conditions in the country, you do it by joining alliances.

        • Typical usage in Europe is around 400 W per household on average. 4 kW? What are you smoking? That would make two days of my energy expenses almost larger than my monthly bill.
        • by bullok ( 155096 )
          No. Typical usage in Europe is MAYBE 4kWh/year. Notice the difference between kW and kWh, please. They are very different - kW is power, kWh is energy. See: http://www.energylens.com/arti... [energylens.com] for an explanation. You can find energy use for several countries at http://shrinkthatfootprint.com... [shrinkthatfootprint.com] Having said that, there is no way that 150kW powers only 10 houses. Louisiana uses more energy per household than any other state in the US (probably due to air conditioning): 15270 kWh per year (the average in t
      • You're all falling into the trap of average daily power usage. The heliostat needs to provide the peak power draw, not the average power draw of a house.

        I'm a South African and while my 3 person house averages 700W power consumption over a 24 hour period, my peak is close to 10kW if I've got the stove, water heater and kettle going at the same time. That happens regularly in the early evening or mornings. And yes, we have electric stoves and water heaters because we don't have a gas infrastructure like Eur

    • Re:Bullshit (Score:5, Informative)

      by tlhIngan ( 30335 ) <slashdot AT worf DOT net> on Tuesday August 25, 2015 @12:04AM (#50385689)

      That's 68% efficiency, which nobody has achieved.

      These are heliostats, not PV panels. Heliostats work by heating a salt to high temperatures then using the heat to power a turbine in a traditional heat engine. The latter tends to be highly efficient (over 90%), while the former is around 75% efficient or more.

      It is as the article says - it's converted to heat then heat is used to generate electricity, something a lot of power plants do (including nuclear, coal, natural gas, and others).

      If it was PV panels, you're correct, since the best PVs are only getting around 20%. But if you don't mind the extra space for the equipment, solar thermal is the way to go.

      • Powerplants benefit from economies of scale. They are talking about a system 2.2sqm in size. I'm sceptical.

      • Re:Bullshit (Score:4, Insightful)

        by superposed ( 308216 ) on Tuesday August 25, 2015 @02:56AM (#50386121)

        Heliostats work by heating a salt to high temperatures then using the heat to power a turbine in a traditional heat engine. The latter tends to be highly efficient (over 90%), while the former is around 75% efficient or more.

        I think you're trying to say that mirrors can heat salt with >75% efficiency and heat engines tend to be >90% efficient. The first claim seems vaguely plausible, but the second claim is certainly false. Typical single-cycle power plants have efficiencies around 35%, and combined cycle plants (combustion turbine plus heat-recovery steam generator) have efficiencies up to about 50%.

        With a heat engine operating at normal terrestrial temperatures (say 300 K on the cold side and 1000 K on the hot side), the maximum possible efficiency [wikipedia.org] is 70%. To achieve 90% efficiency, the high temperature side would have to be at least 3000 K (half as hot as the sun). I doubt this system is that hot.

      • by NakNak ( 1148087 )

        But if you don't mind the extra space for the equipment, solar thermal is the way to go.

        Apparently so. There's a reference here [mg.co.za] to KaXu Solar One, 1km square made up of 120 parabolic troughs "delivering up to 100MW". And it seems that storage after sunset is baked in, with the promise that rocks will do it cheaper than molten salt.

    • by Khyber ( 864651 )

      Learn to read moron, OVER 100.

      Oh, and back to fucking school, because concentrated solar is WAY more efficient than PV.

  • Ah, the smell of luvvies in the morning!

  • "Smokers" (Score:2, Interesting)

    One problem with industrial-scale central-focus concentrating solar systems is "smokers" - birds that were fried by the concentrated light.

    - The concentrated light isn't visible as a bright spot in the air from below and the sides. It IS visible from above, as is the small percentage reflected from the object at the focus.
    - This light attracts insects.
    - The insects attract birds wishing to eat them
    - The birds fly into the focus.
    - The large amount of focussed sunlight

    • Re:"Smokers" (Score:5, Interesting)

      by Socguy ( 933973 ) on Monday August 24, 2015 @09:37PM (#50385259)
      While what you talk about does happen, it's not a problem because of the relatively rare nature of the incidents. Skyscrapers in cities kill orders of magnitude more birds than power towers.

      Frankly, the birds would be far better off if we switched to CSP exclusively due to the wholesale destruction of habitat caused by fossil fuel development.
      • Well, they do, but largely because there's so many more of them.
        • by Anonymous Coward

          And you think the number of CSPs are ever going to get close to the numbers of buildings birds slam into? It'll never compare. Not to mention the pollution from a single coal power plant easily kills off more birds and other wildlife than the few that randomly fly through a "heat beam". We're talking a small number of birds compared to the already huge losses we take from the existing pollution producing coal power plants.

    • Re: (Score:2, Informative)

      by Anonymous Coward

      Bird deaths caused by wind and solar are minimal compared to [wikipedia.org]the bird deaths caused by traditional fossil fueled infrastructure. Much like the wind turbine issue, it is much ado about nothing. It is just more visible and makes a better news story than the slow poisonings or secondary displacement deaths caused by other power sources, but in scale is far less damaging.

      • Bird deaths caused by wind and solar are minimal compared to the bird deaths caused by traditional fossil fueled infrastructure.

        Thanks.

        I was already aware that wind power, despite the "bird kill" hype, was not all that large a problem. (I'd also thought it might be overestimated, too: Birds die where they live, and wind farms are good hunting sites for raptors and feeding sites for other birds.) It's good to have references to studies actually comparing it to other sources of power - and the comparison t

    • Re: (Score:1, Funny)

      by Anonymous Coward

      PERFECT, a solution to their chronic hunger problems in Africa...

    • Nature of bird injury mostly depends on how the bird is exposed - full on strike, or did he just get "winged?"

      Maybe with large migratory populations, the carnage will continue for a long time. The elevated track people mover in Miami didn't run for a year or so after the tracks were built - pigeons thought the tracks were just the greatest place ever made to hang out, nest, etc. The first months of operation (of the very quiet electric cars) were a nasty pigeon bloodbath, feathers and guts everywhere. Af

    • by dbIII ( 701233 )
      Yep - just like the bird that hit a window, pretty tough for the bird.
      It doesn't stop us having windows so as a stalking horse for a politically motivated objection it's very weak.

      That politically motivated objection is making some people in China very rich on US developed technology that kept on getting knocked back.
    • At 150 kW output (and substantially more input) it's not clear to me whether the birds would be instantly killed or merely blinded, badly burned, and left to suffer and die on the ground. But I bet even this village-scale heliostat system will suffer from this problem.

      Not sure about this installation, but one I read about in Australia was in the desert, where there are no birds.

      • Not sure about this installation, but one I read about in Australia was in the desert, where there are no birds.

        Huh?

        There are LOTS of birds in deserts.

    • Gives new meaning to "smoke and mirrors".
    • No problem: we'll scare the birds off with lizards, then use Chinese needle snakes to get rid of them, followed by snake-eating gorillas, and then we just need to make Africa have a winter.

  • The only places that use diesel are areas that can't be properly served by other power plants.

    Requires no concrete, well seeing as the article didn't mention how they dealt with the problems concrete solves.(stability, weather resistance) I'll just chalk that up to another example of agenda driven reporting. Looking at the image a good wind will turn these things into tumble weeds.

  • Likely this is true until the trackers built into the base go tits up. There were a number of these systems in the California desert in the 80s, don't hear about them any do we? To complicated and maintenance intensive to be practical and ultimately damages the reputation of solar. Simple high efficiency solar panels are most likely to disrupt the present power generation monopolies and allow us a bit more freedom from the handful of those that literally have the power in their hands. Consider this, whe
    • Living in the past? Are you traveling at relativistic speeds perhaps?

      Hey, Rip Van Winkle, it 2015, not 1980. Simple math. To make it fair, let's say 1990. 2015 minus 1990 equals 35 years.

      No change in electronics has happened since 1990, according to you. Are you posting here using your ASR-33 teletype or your DEC VT-100? Just wondering.

  • What where South African power needs in the distant past? Mining, always ready rapid air defence for its decades long military needs, city, towns, advanced industrial use (eg Secunda and other projects).
    The power grid was a huge cost to expand everywhere over decades.
    Advanced tracking tilt heliostats can offer grid isolated communities a way to escape the traditional costs of diesel use with a generator at a remote location, delivery costs and currency exchange rate pressure needed to pay for all that do
  • " offer solar energy that's cheaper than diesel."

    Diesel is an extremely expensive fuel. Comparing yourself to that, when conventional PV is 2 to 3 times cheaper already, seems very fishy indeed.

    http://www.lazard.com/media/1777/levelized_cost_of_energy_-_version_80.pdf

    • The South Africans have mismanaged their power supply system to the extent that they now have to operate open-cycle emergency/peaking sets on diesel, continuously. This is very expensive, as you say, and is contributing to the downward economic spiral. Hence the grasping at straws.

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