Solar panels energy density


In this report:

Smil writes:

Energy density is not difficult – power density is complicated.

One view power densities of typical fuels is sufficient to comprehend while we favor coal over wood and oil over coal: air-dried wood is, at the best, 17 MJ/kg, good-quality bituminous coal is 22-25 MJ/kg, and refined oil items are around 42 MJ/kg. And an evaluation of volumetric power densities helps it be obvious the reason why shipping non-compressed, non-liquefied gas could not work while shipping crude oil is low priced: gas rates around 35 MJ/m3, crude oil has around 35 GJ/m3 and hence its volumetric power density is a lot of times (three orders of magnitude) higher. A clear effect: without liquefied (or about compressed) propane there may be no intercontinental deliveries of that clean gas.

Energy density is a much more complicated adjustable. Engineers have used power densities as revealing measures of performance for decades – but several specialties have defined them in their own particular ways.

For previous 25 years I have favored yet another, and a lot broader, way of measuring energy density as probably the most universal measure of energy flux: W/m2 of horizontal section of land or liquid area as opposed to per product of working surface of a converter.

Below are a few of Vaclav Smil’s results:

  • Most large modern-day coal-fired power flowers produce electrical energy with power densities including 100 to 1, 000 W/m2, like the part of the my own, the power plant, etcetera.
  • Hardly any other mode of large-scale electrical energy generation occupies only a small amount room as fuel turbines: besides their compactness they don't need fly ash disposal or flue gasoline desulfurization. Cellphone fuel turbines produce electricity with power densities more than 15, 000 W/m2 and enormous (>100 MW) stationary set-ups can easily provide 4, 000-5, 000 W/m2. (What about the mining?)
  • The vitality density of dried out wood (18-21 GJ/ton) is near that sub-bituminous coal. However, if we were to provide a substantial share of a nation’s electrical energy from lumber we might need certainly to establish substantial tree plantations. We're able to not expect harvests surpassing 20 tons/hectare, with 10 tons/hectare becoming much more typical. Picking all above-ground tree size and feeding it into chippers allows for 95per cent data recovery of complete field production, but whether or not the fuel’s average energy thickness were 19 GJ/ton, the plantation would produce only 190 GJ/hectare, leading to harvest power density of 0.6 W/m2.
  • Photovoltaic panels are fixed in an ideal tilted south-facing position thus get more radiation than a product of horizontal area, but the normal power densities of solar areas are reasonable. Additional land is necessary for spacing the panels for servicing, accessibility roadways, inverter and transformer facilities and solution structures — and just 85percent of a panel’s DC score is sent through the playground into the grid as AC energy. All informed, they deliver 4-9 W/m2.
  • Focusing solar energy (CSP) projects utilize monitoring parabolic mirrors so that you can reflect and focus solar power radiation on a main receiver placed in a top tower, the functions of running a steam engine. All services included, these deliver for the most part 10 W/m2.
  • Wind turbines have fairly high-power densities as soon as the price measures the flux of wind’s kinetic energy moving through work surface: the region swept by blades. This energy thickness is usually above 400 W/m2 – but power density expressed as electricity created per land area is significantly less! At the best we can expect a peak energy of 6.6 W/m2 as well as a comparatively large typical capability factor of 30% would deliver that down to only about 2 W/m2.

For comparison, incoming Solar radiation achieving the Earth’s area features a worldwide average power density of 156 W/m2 of which 55 W/m2 is radiated back to the atmosphere as long trend energy.

Obviously, energy density is of limited worth for making choices regarding power generation, because:

  1. The cost of a square meter of land or liquid varies vastly based on its area.
  2. Making use of land for example purpose cannot constantly avoid its usage for other individuals: e.g. solar power panels on roofs, plants or solar power panels between wind turbines.
Nevertheless, Smil’s fundamental point, that most forms of green types of energy will require us to devote bigger aspects of our planet to energy production, appears robust. (a possible exception is breeder reactors). This point can also be created by Saul Griffith in his discussion of ‘Renewistan’. Stewart Brand had written:

The whole world currently runs on about 16 terawatts (trillion watts) of power, most of it burning fossil fuels. To level-off at 450 ppm of co2, we will have to decrease the fossil gasoline burning to 3 terawatts and create all the sleep with green energy, so we want to do it in 25 many years or it is far too late. Presently about 50 % a terrawatt originates from clean hydropower and something terrawatt from clean nuclear. That actually leaves 11.5 terawatts to generate from new clean sources.

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