Kat curd
  • Kat curd
  • Brisbane / Qld/ Australia
  • Australia

This conversation is closed.

Could solar power utilize the external walls and roof to collect the heat needed to generate the power for that building or cars?

Our cars get so hot particularly when parked in the sun all day surely this heat could be captured to power the vehicle. The same with our roofs and walls they all get full sun when ever the sun is out. It seems we spend a lot of time and money looking for the right substance to use when we have so many buildings and vehicles already in use that are that always hot including our pavements and roads. Could we use the heat that is already being absorbed to solve the solar power problem quicker.

  • Sep 12 2013: Kat one of the major problems is the devices used around the house are all 110 or 220 volt systems. Where as automobiles & boats for instance only use 12 volts for many of the same services. We could save a lot of energy by simply switching to 12 volt systems. If we built homes underground or with thicker walls and double pane windows with reflection on the outside that alone would cut huge costs of heating and a/c.
    The problem is the people who are making building decisions are subsidized and influenced by the corporations that are making money from energy so they work together to get more money from you. The deck is stacked against you all the way. Your best bet is community action with people like yourself who truly want to save energy. The problem is lots of people in communities work for the very corporations you are trying to fight and they will fight with and for the corporations. The good news is with the internet you can find and build coalitions of your own with like minded people. The information is there and the people are there, you just need to get together.
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    Sep 12 2013: Hi Kat,

    Do not be deceived by political simplification of this issue.

    Heat is only one form of radiative energy - it lies at the bottom of the entropy gradient and is hard to get useful energy from.
    A large part of radiation received from the sun is at a higher state than heat - it is this form of energy that drives photo-voltaic collectors.
    The surfaces of cars and houses can be use to collect useful energy (as electricity).
    Germany is doing very well doing just that - using rooves as the available collector-space.
    The issue of storage becomes less a problem when you use a "smart-grid" to move excess electricity to places where it is needed - but electrical storage is still a problem - a problem which many great minds are working on, and getting great advances.

    Some people say that nuclear is the way to go. But I saw a calculation somewhere, that shows current reactor-generators occupy enough land - that if you cover all that land with photo-cells, would generate the same amount of electricity.

    The best idea I have seen so far is to replace road surfaces with photo-voltaic collectors - that's a LOT more than roof-space, and the calculation shows that it could generate 10 times more energy than we need - and the road-collectors need only be 14% efficient .. that's not a lot.

    One thing that rarely gets said: The stuff covering our roads (asphalt) is a by-product of oil refineries. There are some guys who don't want to loose their secret payoff ;)
    Replacing asphalt with low-grade photo-collection is not a big engineering challenge.

    In the mean time - get solar photovoltaic on you roof - it will provide all your lighting needs and charge-up your electric car. As for other energy-intensive appliances - they are all badly designed and inefficient - there are heaps of ways around that.
    • Sep 12 2013: Nuclear energy taking up more land than solar? Seriously?
      Nuclear's got its share of problems just like everything else, but taking up an abundance of land isn't one of them.

      And who's to pay for all those photo-voltaic cells? They're quite expensive, and produce only minimal power. As opposed to nuclear and fossil fuel reactors, they don't provide it on demand either, and as I've already said, current energy storage technology is crap.

      Some appliances are also energy-guzzling by necessity. A car requires a certain amount of kinetic energy to get up to speed, heating elements are incredibly efficient, but the heat energy needs to come from somewhere, and so on.
      Its usually got more to do with physical limitations, not bad engineering.

      Asphalt being partially a byproduct of oil isn't much of a conspiracy either. Once the other, more useful parts of the oil have been refined and extracted, you've left with the stuff they make asphalt out of. Its just clever use of an existing waste product--I'm pretty sure no one would use it if a cheaper alternative came along.
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    Sep 12 2013: Average solar energy per square metre is about 160watts. Energy usage by a car is more like 20,000watts so for every hour you run your car you need about 125 square metre hours of sunlight. So if you can fit 6 square metres of panels to your car you could drive for an hour every 20 hour of sunlight. So don't plan any long trips.
  • Sep 12 2013: Short answer: There are cars, buildings, ships and planes that run on nothing but a combination of solar and batteries.
    Nadav has explained some of the problems you need to overcome.
  • Sep 11 2013: Its not quite that simple.
    Converting heat into useable power is far from trivial. Often times, the systems required to so are typically either too big, too expensive or too heavy to be practical for most applications if all you're utilizing is existing background heat (burning fuel is another matter, but not the issue at hand).

    The heat energy found in a car on a hot summer day is nothing compared to the energy required to run it. Throw in the inescapable inefficiency (thermodynamics and all that), and it only gets worse. Add on top of that added weight and expense of an on board system on the car to utilize the heat, and you may as well ditch practicality by the wayside and tell it to hitchhike home.

    Houses and other stationary buildings typically have more moderate power needs (except industrial buildings), but its impractical for many of the same reasons. Solar panels have some utility, but overall, its just less cost efficient than burning a fossil fuel or even utilizing a power plant's nuclear energy. What you save on fuel you loose out on maintenance, low power output, and having no control over the on/off switch.

    The one exception I can think of to this rule is heating water for baths, which the sun does quite well with a fairly simple system. Skipping the stage of turning solar output into electricity is key here (efficiency shoots straight up). Problem is, you need that energy as electricity for most modern applications.
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      Sep 12 2013: Thank you so much for your reply. I am amazed that the heat in a car is so limited in its capacity to create energy. I have so much to learn about this subject so thank you for filling me in. If there was a way to extract the heat from walls and pavements would that be enough energy? Interesting idea to skip the electricity stage perhaps there is some merit to that if we could find a way to enable the energy to go directly to its required tasks.
      • Sep 12 2013: Honestly, insisting on using the residual solar heat to power things using today's technology is like realizing you have a few spare tires in storage, and buying a car so they wouldn't go to waste. As an investment, it just doesn't make sense.

        If power storage technology was better, maybe we'd be getting somewhere. But as of today, that's just not the case.
        Having no control over the sun's on/off switch is a big drawback, as is the fact you have to store energy for a longer period than its in use (as the calculation above shows, around the order of 20 hours of solar energy into one hour of driving, for example, and that's with 100% efficiency, which solar panels are nowhere near).

        Advances in battery and/or capacitor technology can very easily be a game changer in this field and many others. When they're here, we'll see. Until then...