Terawatt-Scale Photovoltaics

Here’s a cool paper which seems to be freely available:

• Nancy M. Haegel et al., Terawatt-scale photovoltaics: transform global energy, Science 364 (2019), 836–838.

Important topic! Here’s the abstract:

Solar energy has the potential to play a central role in the future global energy system because of the scale of the solar resource, its predictability, and its ubiquitous nature. Global installed solar photovoltaic (PV) capacity exceeded 500 GW at the end of 2018, and an estimated additional 500 GW of PV capacity is projected to be installed by 2022–2023, bringing us into the era of TW-scale PV. Given the speed of change in the PV industry, both in terms of continued dramatic cost decreases and manufacturing-scale increases, the growth toward TW-scale PV has caught many observers, including many of us (1), by surprise. Two years ago, we focused on the challenges of achieving 3 to 10 TW of PV by 2030. Here, we envision a future with ∼10 TW of PV by 2030 and 30 to 70 TW by 2050, providing a majority of global energy. PV would be not just a key contributor to electricity generation but also a central contributor to all segments of the global energy system. We discuss ramifications and challenges for complementary technologies (e.g., energy storage, power to gas/liquid fuels/chemicals, grid integration, and multiple sector electrification) and summarize what is needed in research in PV performance, reliability, manufacturing, and recycling.

Of course, increased energy storage is needed to take advantage of solar power. Let’s see what they say about that:

Energy storage

At high penetration, increased PV installation is synergistic with increased storage. Tesla recently installed a 100-MW battery in South Australia and in the first 6 months recovered 14% of the capital cost. California is also setting aggressive targets for storage. The price of lithium-ion batteries has decreased by more than 80% in the past 8 years, and improvements are expected to continue through a combination of technological advances and increased manufacturing capacity. To achieve the U.S. Department of Energy target price of U.S. $150/kWh for automotive batteries capable of charging within 15 minutes, research should explore materials with higher energy density to further reduce costs, focusing on nickel-rich, critical-materials–free cathodes and advanced anodes for lithium-ion systems. With further research and cost reduction, flow batteries and sodium-ion and multivalent-ion or conversion systems could also hold the promise of long-term competitors to lithium ion.

An additional approach to battery-based storage is pumped-storage hydropower (pumped hydro). Recent research indicates that there is a substantial technical potential for untapped off-river (closed-loop) pumped hydro and other forms of gravity storage in many parts of the world (9, 10). Pumped hydro has the advantage of being able to provide short-term responsiveness and diurnal-scale storage potentially at low cost.

The biggest challenge may be to meet energy requirements during the winter at high latitudes. However, wind power tends to be more abundant in many of these locations, whereas most of the world’s population lives closer to the equator. Economic development as well as population growth may be dominated by countries within 35° of the equator in the coming decades.

14 Responses to Terawatt-Scale Photovoltaics

  1. Toby Bartels says:

    the scale of the solar resource, its predictability, and its ubiquitous nature

    Is this how you say that the Sun is huge and visible from anywhere in the world at dates and times that can be easily calculated, in the abstract of an article in the Science?

  2. Steven Molnar says:

    It’s not sexy, but trains loaded with rocks work well for energy storage in some locations (those with a hill and an open space up the hill). Also, I’m always hoping domestic-scale flywheel technology will mature, but it has been just over the horizon for almost as long as practical fusion reactors have been 20 years away.

    • The basic problem of “pumping energy into a system in a way that we can get it back out later at reasonable efficiency” seems broad enough that there must be many possible solutions. So I’m pretty optimistic that if enough PV is installed so that “daytime power” becomes significantly cheaper than “nighttime power”, people will be able to come up with methods of turning one into the other, and the storage problem will be solved pretty quickly.

  3. ecoquant says:

    Noted. I mentioned the post in context here. It is an important paper. Even Professor Tony Seba thought so (personal communication).

  4. Great post as usual. People don’t realize how much of a problem electricity storage is when it comes to PV. The best analysis on the matter is given by a 5 year old asking “how solar devices work at night?” well, batteries of course!
    I believe that all electrochemists in the world should work on getting the best batteries possible in terms of charge cycles, charging times, voltage capacity, etc.

  5. G.J. Smeets says:

    What about the possible drawback: black swan probability of a giga volcanic eruption somewhere on the planet shutting off the solar resource for a week or so.

    • John Baez says:

      Maybe keep some fossil fuel plants around for emergencies like this? (Emergencies of sub-planetary scale are more likely.)

      • G.J. Smeets says:

        Agree. No use to burn every fossil bridge down. I guess the oil industry by now is figuring out how to change their business model from ‘delivery’ to ‘back-up’.

        • ecoquant says:

          @G. J. Smeets,

          Ironically probably the best fossil fuel generation for backup is not explosive methane, but, rather, something like coal or biomass. Gas requires a piping infrastructure which both needs to be maintained and is a source of leaks.

          Of course, the problem of emissions for flying will need to be solved. Even though tropospheric flight with electricity might be solved, long range will need something else. I haven’t examined it, but it seems to me that Hydrogen combustion might have specific impulse high enough. I suspect, though, based upon experience with Hydrogen for rockets, containment might be a problem, needing heavy tanks or heavy refrigeration.

          There is, of course, Sir David King’s proposal for long haul transport using robust dirigibles. One could imagine a luxury liner version of these.

          See https://www.youtube.com/watch?v=HNAzkAuXsJg

    • ecoquant says:

      You could also have a regional nuclear conflict that induces a “nuclear winter”. An additional coupling that isn’t much talked about is that another downside (of many) to using “solar radiation management” (Broecker, Keith, among others) to limit temperatures from high concentrations of CO2 is that it would similarly affect PV generation.

      I think that’s an argument against nuclear conflict and SRM and not an impediment to PV.

      I also estimate a truly planetary scale caldera-sized eruption (think Yellowstone from about 800 kya) would have consequences far more pervasive than energy loss, e.g., loss of food supply, and these would happen whether or not energy was from PV.

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