MTN installs huge solar plant

The mobile operator has installed a large concentrating solar cooling plant at its head office to cool its data centre facilities.


MTN has launched a concentrating solar cooling plant at its head office in Roodepoort, west of Johannesburg. The plant will be used to cool the company’s data centres. The facility generates enough electricity to power 350 average-sized homes.

The plant uses a technology called Linear Fresnel Concentrating Solar Power, which uses heat generated from the sun and has a peak cooling capacity of 330kW. A spokesman for MTN says the system will prevent 218 tons of carbon dioxide being emitted annually. It will also save R1m/year in costs, MTN said, though the mobile operator has not disclosed how much it has invested in the facility.

The project forms part of the worldwide “dena Solar Roofs Programme” coordinated by the German Energy Agency and supported by the German federal ministry for economic affairs and energy.

The system is made up of 242 solar mirrors covering an area of 484sq m. These mirrors track the sun to generate pressurised hot water at 180 deg C. The hot water in turn powers an “absorption chiller” that produces chilled water circulated into the data centre for cooling IT equipment.

The mirrors follow the movement of the sun, based on GPS location, orientation and the date and time. This information guides the system to track the sun to concentrate on the central absorber tube where heat is generated.

The absorption chillers employ a lithium bromide water solution, which uses water as the refrigerant.

When it rains, the mirrors move into a self-cleaning position and on cloudy days, the mirrors turn down into a protective stow position.  — © 2014 NewsCentral Media

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  • Skerminkel

    Three questions, from a non-HVAC engineer:
    1. If the equipment generates sufficient heat to require 330kW of energy for cooling, why can the original heat itself not be used to power the system?
    2. What is the GPS technology for? It the mirrors and collector are not moving anywhere.
    3. Why does the system “turn down into a protective stow position” on cloudy days? Surely it can work at lower efficiency then.

  • Frank

    1) Power what system? If you’re going to use the energy to cool things anyway, why bother converting to electricity?
    2) The article says GPS location, not technology.
    3) In case it hails perhaps? I’m sure it can, and does.

  • Skerminkel

    1. “The plant uses a technology …, which uses heat generated from the sun and has a peak cooling
    capacity of 330kW.” This means they generate electricity from the sun’s heat to power aircon to cool servers. Therefore my question.
    2. Semantics. Once the plant is installed, the components do not move. There is no such thing as GPS location. A GPS can be used to determine a location.
    3. Clouds are not sufficient indication of a risk of hail. If they shut it down every time there is cloud cover, they will lose (guessing) 50 days a year, when it hails only 2-3 (another guestimate)

  • Frank

    1) No, they simply use the cool water to cool the servers
    2) Google “GPS Location”. I assure you there is such a thing. How would you determine the location of the fixed plant? Using a GPS of-course.
    3) The point is that the system is cloud / weather aware. It can turn to protect or clean itself. Don’t get hung up on the details.

  • Joe Black

    Although it is undoubtedly positive news I would not have used the term “huge”

  • Skerminkel

    1. There is no cool water until it is cooled with the energy (heat!) from the sun.
    2. There is a difference between using a GPS to install the plant and using it in operation. Location is location, no matter if you use a GPS, tape measure, theodolite, sextant or arm length to determine it.
    3. Big difference in effectiveness, especially if they claim 330 kW! I assume the designers considered peak vs. average delivery, but nothing is reported. If they lose a week’s generation due to the cloud cover, the CO2 emission claims can be BS.

    I will get “hung up” on detail, as this is a technology news site, reporting about a technology company employing what they claim to be new technology. If I want mass consumption news, I would go to News24.

  • Skerminkel

    There story is now over on MyBB as well. They are (slighlty) clearer on the GPS matter. I will copy my questions there.

  • Frank

    1) Don’t get hung up on the un-important details. The ones like the chemical process eluded to in the end are worth reading though. In other words, hot water is turned to cold using a chemical process.
    2) Really, I don’t recall anyone ever marking a location using Centimeters, have you? I have seen GPS coordinates being used though.
    3) You’re right, they’re lying, it’s a conspiracy.

  • Frank

    Meet you there.

  • Greg Mahlknecht

    I’m not an HVAC engineer either, but here are my educated guesses:

    1. The solar power is intended to reduce the datacenter’s draw on the grid. Its output unpredictable and relatively unstable. A good datacentre requires two super-reliable power feeds from different grids, and these are already in place. I assume it’s much easier to retrofit the more robust cooling equipment with the solar power input than the more complex and sensitive power feeds to the server racks.

    2. MyBB has exactly the same sentence, word for word so it’s probably cut and pasted from the MTN press release. Maybe the HVAC engineer who wrote the blurb isn’t an expert in cartographic nomenclature :) I work with a lot of geospatial stuff and have seen “GPS Location” used instead of “Coordinates”, but usually by laymen.

    3. Quick google shows it’s common that on very cloudy days when efficiency is extremely low, it’s safer to protect the panels – if there are huge black clouds blocking the light, it might not be worth the risk trying to harvest a tiny bit of energy when there’s a real threat of very bad weather.

  • baasted_123

    3) Prevent hail damage I suspect.

  • Skerminkel

    Don’t be rude. You have not added any more information about heating/cooling/solar to what I wrote.

  • Skerminkel

    Thanks Greg.
    1. The original question was why not use the data center’s own heat? I suspect it is due to the difficulty in collecting it. I was
    looking for a more informed answer from someone with knowledge on HVAC, but this is probably not the right forum to ask! The piece specifically states that the solar system is used for cooling, not for the general demand of the center.
    2. You are probably right. Since GPS’ came on the market, people seems to have forgotten that coordinates have existed for centuries. Only the tools to determine them for a given location have changed.
    3. Noted.

  • Greg Mahlknecht

    1. Ah okay – yes, I don’t think there’s an efficient way of harvesting enough energy from hot air to make It a viable energy source. It’s the kind of thing we’d have read about on the tech sites and seen in a million political cartoons by now.

  • Colin

    Watts are a unit of power, not electricity.

  • Duncan McLeod

    We’d finally have a use for parliament… ;)

  • Skerminkel

    Makes no difference if you use electrical power, apart from the loss during conversion, which you can also measure in Watt.

  • Frank
  • Bongani

    Alora; “Watt” measures energy per second. “Skerminkels” measures energy of “blogging”.
    btw same “cool” technology as the old school caravan fridges or the parafien-kontrapsies we knew as kids on the farms

  • ComSpec Inspect (Roald)

    1. It is cost effective and economical to send chilled water a few floors down, our buildings are normally poorly insulated with an inner core temp around 2° to 9° in winter and 5° to 12° in summer without costly insulation. I would argue the end product cooled water, the area on the roof available space that directly determines the amount of power generated determined the final combination.
    2. The GPS tech with a few more gadgets and a few servo position motors focuses the mirrors to have maximum reflection of sunlight onto the focal point or collector, (a special oil is heated up to 400° to generate superheated steam for turbines in the US),
    3. the heat exchanger using the solar power to generate the heated water is designed for optimal transfer of energy at a certain value of solar energy, the absorption chiller again designed for optimal efficiency at a set temperature obviously with some tolerance and when the solar supply decreases below a certain preset value the mirrors turn downward, and the backup cooling system kicks in to maintain the correct cooling temperature for the IT locations.
    -That is my logic behind your question

  • Jans

    1) Water is the only way to efficiently cool in a feedback loop, but they probably don’t want to take the risk and will use air instead
    2) There are multiple GPS satellites which are affected by weather conditions. This is more of a monitoring function to work out how to best position the solar cores for the location.
    3) Moisture can form and collect which will cause glass to crack when it is piping hot

  • Andrew MacRitchie

    Let’s have a look at the numbers:

    1. MTN says that the solar unit produces 330 kW at peak from 484 m2 of mirrors. Really? This is a bit of a tall story when one calculates that this is 680 watts per square metre and such a peak would be highly optimistic even if the unit were located nearer the equator (we are nearer 30 degrees south). Because of absorption and refectance in the atmosphere, the actual average W/m2 would be well below the peak MTN hopes for. As example, the average watts per square metre in north eastern USA is 120 W/m2. We are somewhat warmer here and let’s be generous and say 400 W/m2 for sunny SA – enough for a few light bulbs per square metre.

    2. MTN hopes to save R1 million per year from from the solar power unit. Let us try a rough calculation – assuming, for convenience, that MTN pays R1.00 per kWh, then the number of kWh used/saved over a year would be 1 million kWh. Divide this by the number of hours in a year, and the result is that the unit will produce in reality an average of about 120 kW/m2 (or one domestic light bulb).

    3. I looked up “dena Solar Roofs Programme” through both Google and Bing and found little useful in the way of technical detail. On the other hand, I did find out that Dena is a consortium of German bureacracy and banks – just the sort of people you could trust to deliver honest and economic technology.

    Maybe MTN is getting some sort of kick-backs from the German government and/or Eskom to compensate for this poor economic investment. If not, they could turn on their cellphone customers for recompense.

  • ComSpec Inspect (Roald)

    This site has some interesting factual reading
    A snipit from this site;
    “Bottom line: Just because you can produce steam/hot water to fire an absorption chiller doesn’t mean that you should! Your thermal energy needs to be very, very cheap before an absorption chiller can compete with an electric unit on an input energy cost basis. Before deciding to go with one type of chiller or the other, make sure you know what each type of chiller will cost you to purchase, maintain, and operate at a range of fuel and electricity costs. In the case of absorption chilling, it pays to be a little skeptical.”

    1. One fact one can’t overlook excluding the maintenance or operating cost, the thermal source is God given and free.
    2.Concentrating Solar Power (CSP) technology exist, and is most effective in the sun belt countries as referred too, this belt where effective solar energy can be harvested is between the 35°Deg North and 35°Deg South, the entire South Africa is inside this belt.

    CSP is a economical and effective source of energy one only need to look at the following 2 sites to realise that

    Personally I never used MTN got a 1 gig data card 2 days back and its already missing, kick or not at least they are doing something.

  • Bulldog007

    They have the money to do this from their fees/charges or whatever

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