Will Solar Power Meet World Electricity Demands?

Proponents have looked to solar power as a potential panacea to the world’s current and future energy needs, while critics note that solar power still provides less than 1% of the world’s electricity. While wind power has grown to scale much faster, conventional wind technology has much less capacity to scale than solar power, and the theoretical limits on solar power are significantly higher [1]. When might solar power fulfill the hype and generate much of our electricity? Solar energy has grown at a rapid clip since its infancy in the 1970’s, from 0 to 20GW (nameplate capacity) in 2009. How much of worldwide electricity demand will solar be able to fulfill if it maintains this growth rate?

Total solar power capacity continues to grow at 20-25% per year, a rate of growth it has maintained for decades. It’s not surprising that solar photovoltaic technology is advancing rapidly, as it is a cousin of traditional semiconductor technology. For almost four decades semiconductor technology advanced according to Moore’s Law, with chips roughly doubling in transistor density (and speed) every 18 months. At a 20% annual rate of growth, installed solar capacity would rise from 21 GW in 2009 to almost 6000 GW by 2040. This install base could generate 12 trillion kilowatt-hours of electricity per year, or two-thirds of today’s worldwide electricity consumption [2]. However, the EIA estimates that by 2040 worldwide electricity demand will hit 35 trillion kilowatt-hours!

Even assuming that solar energy installations grow at a 20% clip for three decades, the total install base will not be sufficient to meet world energy demands. Despite the industry’s rapid growth, replacing a hundred years of fossil-fuel based generation capacity by mid-century may be close to impossible. Nonetheless, if solar energy manages to scale on this trajectory, its contribution would still be enormous, and would likely bring total renewable generation to over 50% of all electricity.

Can it be done? Did anyone in the 1960’s believe that a 2010 phone would have more processing capacity than all the world’s computers combined?

[1] From Without The Hot Air – all wind power resources worldwide could supply a significant fraction of total power needs, while solar energy in the Sahara alone could theoretically supply all world energy needs.

[2] The EIA International Energy Outlook shows current worldwide electrical demand of roughly 18 trillion kilowatt-hours, with this figure growing to 35 trillion kWh by 2035 by www.usbgeeks.net.


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  2. TheTracker said

    “Despite the industry‚Äôs rapid growth, replacing a hundred years of fossil-fuel based generation capacity by mid-century may be close to impossible.”

    Not impossible; just requiring a wedge approach, rather than a silver bullet.

    Solar, nuclear, and wind power can all take some of the load, as can efficiency. The Japanese get about two and a half times the productive capacity from a ton of CO2 emissions as compared to Americans. The most underappreciated zero-emissions “energy source” is actually efficiency gains.

    • Tracker, have a look at this post:

      http://truecostblog.com/2009/02/19/how-much-energy-do-we-need/

      I calculate total capital investment required to go to solar (or any renewable) based on a cost of 50c per watt of installed PV (roughly equivalent to 1c/kWh over a solar panel’s lifetime).

      Even with this incredibly low cost (which I’m optimistic we’ll achieve in the next decade or two), it would still cost $60 Trillion to build out the required renewable infrastructure.

      I actually think my post above is optimistic – almost impossible leaves some hope out there. When push comes to shove, I think it will get done. $60 Trillion sounds like a lot – but it’s less than current world GDP, and spaced out over two decades, starting in say 2020 – that’s 5% of GDP per year or so. So call me cautiously optimistic.

      • TheTracker said

        The key point seems to be:

        The graph above shows that the US could cut per capita energy consumption by 70% without a significant drop in quality of life.”

        Which is in line with what I said. Here’s where I lose you:

        “An investment of $150 Trillion would provide enough solar energy to power the world at these standards, a number over double current world GDP.”

        That’s an apple-to-oranges comparison. The world will only consume that amount of energy when they are developed and consuming at first world levels themselves. For that to happen, the world’s GDP will have to grow tremendously. Current GDP is a meaningless number in this context.

        More reasoonably, you could look at a future where people come to earn like Europe as they come to consume energy similarly. So roughly $40,000 * (9*10^9) = $360 trillion in yearly GDP.

        Their capital investment in solar power would be about 40% of annual GDP. If your capital stock lasts for 40 years, you’re investing about 1% of GDP per year to stay there. Reasonable?

        I don’t think we need to resign ourselves to an energy-constrained future, just that we should work towards a future in which a mix of sources is used, including the important option of not wasting energy.

      • Tracker,

        I think the truth is somewhere in-between. I was comparing to today’s GDP because many of the investments in renewable energy capacity need to be started today, or soon, when World GDP is roughly at today’s levels. But you make a good point, which is that the build-out will occur over time, and GDP should be growing throughout the period. If we just straight-line it, then the investment of $150T compares to an average GDP in the $200T range. Doing it at roughly $4T per year, that’s 2% of GDP. Still quite doable, but this assumes that we get solar (or any renewable) cost down extremely quickly. If we were to use current costs, the numbers just wouldn’t add up. Let’s keep bending that cost curve down…

  3. K Gibson said

    Praveen,

    I think you are a pessimist. First, the objective is not to replace the electricity supply with solar PV power. The real objective is to replace all energy use with “renewable” energy that does not add to the GHG problem or the nuclear problem. You should be an optimist and consider this problem.

    Relying on EIA midrange estimates (as a starting point) in 2015 the world will want to consume 160 terawatt hours of “marketable energy.” Taking the first optimistic step, assume that number is the line that will not be crossed.

    Now, forget about the absolute capital cost of things! How much longer can now 40 year old coal-fired, diesel powered and nuclear power plants continue to run? These fully amortized assets have to be replaced eventually. What about the now 15 to 20 year old cars, trucks and buses? All are looking forward to retirement. If a new technology can come in below fully-costed old technology replacements the “cost” to build is not a problem.

    To be clear, your application of Moore’s Law to solar PV is false. The technology is quite different. The “diodes” are locked in already to the polysilicon material. It is not a matter of scripting finer masks onto a substrate at reduced levels of power. (On the contrary, higher levels of power are the objective.) I don’t think we should accept life in a world where use of solar PV depends on cost much lower that the currently prevailing $2 to $3 per watt (depending on scale and siting). At these prices for small utility scale, independent generator applications, solar PV is competitive with new plants that meet EPA requirements (rule out coal), insurable risk requirements (rule out nuclear).

    As you have discussed previously, electric vehicles are cheaper to own and operate than gasoline/diesel vehicles.

    The only important, constraining “fixed” cost variable in my view is land. Solar PV, CSP and Wind technologies all “consume” a lot of land. Obviously, roof-top solar PV or CPV should be standard in all new-building code. Building complexes and subdivisions should be designed with utilization of insolation and photovoltaics a core principle. Obviously, a parking structure should be topped with solar panels. Don’t even mention parking lots!

    Beyond the borders of cities and towns, however, we need to consider the least obtrusive ways to deploy dual-axis-tracking, concentrated photovoltaic gallium arsenide semiconductor, or similar technology that may actually benefit from Moore’s Law. My optimistic vision calls for platforms elevated high above the heads of grazing animals, tracking the sun with receptive CPV devices. The efficiency of these devices is drastically affected by clouds.

    So wind power is likely to play an equal or greater role. I’d like to spend a week or two living downwind from a 2 to 3 MW wind turbine generator towering 130 meters into the sky. Perhaps I’d camp each night at a different distance and perhaps each night the wind would billow up from 6 mph to 15, or 30. Each morning I’d check for bats and birds. There are real costs, but I don’t think you can make a market in them. Are they tolerable? We need to find out at a gut level.

    Well, I took my ready for prime time technologies. In my first cut, last night, I came up with a total of only 68 terawatt hours. I need your help.

    • Kenneth,

      Thanks for the comment. It doesn’t really matter to me what sort of renewable technology is used to replace existing generation – think of this as a thought experiment. What is the capital cost of replacing the current fleet of power generation with a cheap renewable source that costs 50c or $1 per Watt? The answer to that question is very important to me – it gives us a sense of the scale of the problem.

      The reference to Moore’s law was not to apply that it holds exactly for PV – but PV costs are declining steadily, and I think we will soon get to a point where PV is cost-competitive with the existing grid across most of the US.

      The sudden glut of nat gas in the US may slow renewables adoption however, as we now have a reasonably clean energy source that works well with existing infrastructure.

      The real energy problems are to do with transport fuel and peak oil – but that’s another post entirely! I do plan on updating my List of Countries Past Peak Oil based on 2011 data, since it’s available now.

      • TheTracker said

        Natural gas is unfortunately not “reasonably clean” if you look at it from extraction to use:

        “Switching from Coal to Natural Gas Would Do Little for Global Climate, Study Indicates”

        http://www.sciencedaily.com/releases/2011/09/110908124505.htm

        Many sources besides wind and solar power are available, including nuclear, hydro, geothermal and tidal. But until/unless CCS becomes incorporated on a large scale, fossil fuel burning in all its forms is dirty, dangerous energy.

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  7. You Don't Want to Know said

    Don’t ignore transmission. The electrical grid is like a living being. It needs electricity running through it or it fails, causing blackouts. That means it needs reliable sources of electricity generation day and night, when the wind is blowing and when it isn’t. When the grid is relying on wind for, say, 20% of capacity and the wind dies down unexpectedly, the grid goes down. Happened in Texas in 2007 or 8. If you’re relying on solar for 100% of capacity (or 50, 40, 30) how do you keep the grid up at night? What about when it is cloudy for a week?

    Thought problems like this one are fun, but the world can’t run on hypothetical electricity, it needs the real stuff. Demand continues to grow and promises to keep growing with world population and the needs of modern machinery, nearly all of which runs on electricity. You’ll never meet demand with only wind and solar.

    • Solar power generation is quite often highest during peak load (hot sunny summer days), so that is a positive in the grid load context.

      Solar power will also only attain huge market share if solar panel costs fall precipitously from current levels. The multi-decade trend indicates that they will keep dropping price, so that eventually $1/Watt installed becomes possible. At that price, I would expect solar panels to become a standard part of all new building roofs – which actually lowers grid load, since most of that electricity never enters the grid.

      Make no mistake, there will always be some other form of baseload generation – but I wouldn’t be surprised if we eventually get to a point of majority renewables.

      • You Don't Want to Know said

        I think you’re missing my point about the grid. We often see brownouts during periods of peak demand because that demand cannot be met, but we also see brownouts during periods of normal or even low demand because of transmission or generation failure. Solar panels on rooftops can ease the demand during peak periods, but keeping the grid up will continue to be difficult because solar generation is inherently unreliable.

  8. Mike Broad said

    Dont forget to take into account that the efficiency of solar panels is headed to 40% plus in the next 5 to 10 years. Also, the cost of P.V. is trending down exponentially – 5 years ago Chinese solar panel manufactureres were quoting US$4.00/watt , now the price can be as low as $0.60/watt

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