Why A Solar Economy?
Solar and Geothermal Energy are the most direct forms of renewable energy. Other forms, such as biomass, wind or wave energy are ultimately powered by the sun. Since energy flows from the Earth’s interior are just 0.03% of incoming solar radiation, solar energy potential dwarfs all other forms. Studies indicate the total harvestable energy potential of wind is 5 times global energy demand. Solar’s potential is far higher. Indeed, more solar energy is incident on the earth in an hour than humanity consumes in a year.
Another reason to favour solar over wind is its lack of moving parts. Consequently, solar panels last longer than expected (up to 40 years) while wind turbines wear out sooner than expected ( full report here ). While wind turbines are getting bigger and bigger, solar panels remain compact as they get cheaper, more durable and more efficient.
These are sound reasons to believe the future belongs to a solar economy and not wind.
The main aim of renewable energy is to minimize cumulative atmospheric CO2 levels in 30-70 years time. CO2 levels next year, or even in 5 years, are unimportant. Only cumulative CO2 emissions over the next 30 to 70 years matter. If wind power is a dead end technology, we should concentrate economic resources on pushing solar down the learning curve as rapidly as possible. Indeed, even today, some solar projects are producing some of the cheapest energy in the world.
The argument “we need an energy mix” is a false one designed to humour obstinate people obsessed with pet dead-end technologies. We don’t need an energy mix. We just need a solar economy. This is the problems with a blind carbon price. In the long run, solar energy will clearly become the cheapest renewable, but, in order “to be fair”, we pay the same price for all carbon free energy. The result of a blind carbon price, compared to focusing funding on scaling up the solar economy as rapidly as possible, will likely cost hundreds of billions, if not trillions more to reach the exact same cumulative CO2 emissions in 30 years time.
A Solar Economy with Gas: A Winning Combination
Methane can be manufactured from electricity, water and carbon dioxide through the Sabatier reaction. The concept of using gas to store energy generated by renewables is known as Power To Gas. While the cycling efficiency of power to gas (Electricity -> gas -> Electricity) is only about 38%, existing gas infrastructure, like pipelines and LNG shipping, could transmit solar energy across the globe. The factor 2 difference in irradiance between countries with high and low solar energy potential also compensates for the 40% cycling efficiency of power to gas.
We don’t need a giant global HVDC grid. Power to gas enables the existing gas infrastructure to store and transmit solar electricity across the world. HVDC grids can’t store energy. Existing gas networks can store months of gas reserves. Pumped storage, hydroelectric dams and battery banks with cycling efficiencies of 90%+ could complement P2G for short term troughs in solar output – although high cycling efficiency storage is too expensive to store more than a few days worth of consumption.
An inventory of batteries kept in swapping stations for electric cars could serve a dual purpose of absorbing surplus renewable production as well as rapid EV charging.
Electric vehicles may not necessarily require more energy to be transmitted through the grid to cover transportation, as well as household, energy needs. If batteries banks located next to gas plants and solar panel field are charged up there and then physically transported to swapping stations, it might be possible to power a fleet of electric vehicles without upgrading the grid.
Importance of CO2 Sequestration
The Sabatier reaction requires high CO2 concentrations. It is, thus, important to sequester the carbon dioxide produced from burning gas, both to produce methane with solar power and to prevent climate change. If the solar energy is produced in a different location from where the gas is burnt, the CO2 will have to be piped back to the sunny region to be reconverted into methane. Existing gas infrastructure, that already transports large quantities of natural gas around the world, can also transport CO2. In other words, we will need CO2 pipelines as well as methane pipelines.
A solar economy with power to gas storage, will have a much lower CO2 inventory than a scenario without solar. Instead of storing decades, perhaps centuries of CO2 emissions, we need only store months of CO2 emissions, so there is less to fear from a leak in the system, as only a relatively small quantity of CO2 would escape.
Furthermore, concentrated CO2 will have a fundamental economic value to solar power plant operators. This will enable carbon sequestration companies to be profitable irrespective of carbon prices or government policy.
Space Heating
Combined heat and power, is a very favourable option for a solar powered economy with power to gas storage. Especially if burnt CO2 must be compressed and sequestered. During winter months when there is less sun, gas would be imported from warmer climes and burnt for electricity. Heating requirements will tend to be highest when sunshine is lowest.
Heat pumps could supply any further heating requirements. Electricity’s 18% share of total worldwide energy use is intimidating, given renewables currently only produce a fraction of the world’s electricity. However, for space heating at least, we can take solace in knowing that a little electricity goes a long way. A heat pump can transport about 4 joules of ground heat with just 1 joule of electricity. The number of joules of heat 1 joule of electricity can transport is its coefficient of performance. This is typically 3 or 4 for modest temperature differentials between the inside and outside.
Manufacturing
The gas, which power to gas produces, can be used in manufacturing directly. Additionally, the high temperatures produced by concentrated solar power have applications in a wide variety of manufacturing processes.
James May featured a group of scientists using CSP to manufacture gasoline out of water and CO2.
Shipping
The most credible alternative to fossil fuels for shipping are nuclear reactors. Aircraft carriers already use nuclear reactors so this is clearly feasible. Indeed, a nuclear powered merchant ship, the NS Savanah was built back in 1959 and, in 1969, became the first nuclear powered ship to dock in New York City for the festival “Nuclear Week In New York”
Maritime shipping accounts for 2.2% of CO2 emissions. Nuclear energy currently produce 6% of global energy and existing uranium reserves are sufficient for 135 years at our current rate of use. This implies that nuclear energy could power all maritime shipping for 405 years. Plenty of time to develop breeder reactors or beam driven fusion systems (which are more compact and cheaper than fusion systems designed to produce energy) to breed nuclear fuel from fertile materials as well as process long lived waste.
The only other fossil fuel free alternative is biomass but this is land intensive.
Either that or we go back to sailing boats which would require a significant reduction in ship size and speed with correspondingly lower cargo volumes and longer journey times.
Aircraft
The aviation industry is also responsible for 2% of CO2 emissions.
There are five possibilities for reducing aircraft emissions:
- Biofuels
- Replace with Maglev
- Metal Powder
- Radioisotopes
- Beam Powered Propulsion
As with shipping, aircraft cannot sequester CO2. But while biofuels emit CO2, the growth of biofuels absorbs atmospheric CO2. Biofuels, however, do take up a lot of land and there are even some claims that biofuels are not carbon neutral due to their effect on land use.
Alternatively, high speed trains could replace air travel. Maglev trains have reached record speeds of 375mph, two thirds of the cruising speed of an aircraft. Air travel would still be needed over the oceans, but Maglev trains could reduce aircraft biofuel requirements.
Metal powder combustion is another interesting candidate. The energy density of iron powder combustion exceeds that of gasoline so it maybe a credible power source for aircraft. Furthermore, iron oxide is a solid and so is much easier for a compact system like an airplane or a ship to sequester.
Nuclear reactors are not feasible for aircraft as the required neutron shielding is too heavy. However, many radioisotopes decay by emitting alpha or beta particles. This radiation is easily shielded yet very energy dense. Indeed, one intended use of radioisotope is to power pacemakers. One could envisage hot pellets with a radioisotope in the centre and shielding material around the outside. These hot pellets could heat air entering the jet engine to provide CO2-free thrust. However, radioisotopes can’t be turned off and would require constant cooling. One option is to only load hot pellets onto the aircraft just prior to launch and transfer them from the aircraft into a cooling facility immediately after landing. Getting this system to operate reliably to ensure public safety could be quite challenging. A small, beam-background powered fusion reactor could generate the radioisotopes used to manufacture the hot pellets. Fusion reactors could be relatively cheap to construct so long as they don’t need to generate net energy. Solar energy would ultimately power the atoms beams for these fusion systems.
Alternatively, the aircraft could be remotely powered by an energy beam of microwaves or a laser. The main challenge with powering aircrafts is storing the large quantities of energy required to propel them at high speeds without adding too much weight. Remotely beaming energy to the aircraft from a beam generator on the ground would bypass this problem entirely. This would require very high accuracy. Leik Myrabo is currently experimenting with laser power to propel a prototype lightcraft.
Summary
With appropriate infrastructure to store and transmit it, solar power could power our entire industrial economy. Although it currently only provides a miniscule portion of our total energy, solar capacity has exploded since 2010 going up 20 fold in some places. If the 27% annual compound growth can be maintained, solar could power our entire economy in the next 20 or 30 years. Maintaining that ~30% exponential growth will, however, require a strong political will, not just to install solar, but ensure a that suitable infrastructure of power to gas will exist to store the surplus energy.
John
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Whilst I agree with the top level messages, there’s a lot that I disagree with here, but to actually make the case, I’d need to do a lot more work and I’m not bothered to do that right now. I don’t expect to persuade you without doing a lot more work (which I’ll do some other time). But for the record:
Agree:
Solar is the main energy source.
Power to gas is helpful and important
Nuclear tankers are interesting.
Disagree:
We don’t need an HDVC grid. (Au contraire, I would see wires as more efficient as tankers of LNG for many reasons).
Learning effects mean we should focus on solar. In fact the *shape* of the learning curve means the opposite is true. (You get more learning benefit by spreading out actually). Still, this doesn’t on its own justify spreading out.
Power to gas should be the means of doing a lot of things like heating people’s homes.
A carbon tax will be socially sub-optimal because it will encourage people to do things other than solar. (I’d characterise the situation is that solar is already cheap enough). But I’m not sure about this point. I myself push something slightly different than a carbon tax – eFeebates – but it uses the mechanism of a carbon tax..
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Perhaps Hydrogen /inside/ natural gas tanks is promising. The pressure of the methane keeps the hydrogen in, and a bit of hydrogen leaking into natural gas is not such a bad thing.
Overall there’s a lack of policy instruments to achieve the goal. Is this a planned or unplanned future.
And there’s little looking at the grid and storage beyond a general power-to-gas advocacy (which is a good thing, but creates a lower-carbon future rather than a zero carbon future.
Note i said hydrogen inside natural gas infrastructure. The positive pressure keeps it in. But yeah even a bit might cause brittleness. We’d need to investigate
The key thing is it’s hard to collect all that CO2 from all around the place. If you think that could be done, well that’s a different matter. How do you collect CO2 from people’s boilers?
In short, learning is logarithmic. So you get f-all benefit for an extra 100 GW if you’ve already installed 2000GW. Whereas that benefits another tech much more. This is a really minor point perhaps. Worth going through all the scenarios however – grid stability, storage reqirement, assumptions about CCS etc etc.
Q: How do you collect CO2 from people’s boilers?
A: You don’t. You use gas for:
1) Grid Electricity Generation
2) Municipal Heating systems where heat is produced centrally at Combined Heat and Power (CHP) plants
3) Large manufacturing systems that use methane as an input (which many do)
I think you’ll find that these are the only uses proposed in my article for the gas generated by renewables.
Re: logarithmic learning
It’s important to remember there is not just one kind of technology that produces energy from the sun. There are many. So if we want to take solar power down the learning curve more rapidly, it’s worth looking at new solar energy systems that are currently being tested at a small scale and show a lot of promise for radically reducing solar energy costs.
I’m also happy to fund research for breeder reactors or beam-background fusion systems.
In my view, wind energy’s a dead end. It’s even more intermittent than solar, it wears out sooner, and you can only make it cheaper by making it bigger.
It’s only a matter of time before solar undercuts wind everywhere.
I’m not convinced that after the electricity is converted into gas, there is much to be gained by transporting it using a HVDC supergrid as opposed to an existing gas pipeline. Gas and oil pipelines are very efficient ways of transporting immense quantities of energy over long distances (if they were not, then we wouldn’t have a global fossil fuel economy).
There is certainly a case for saying that if you could avoid converting electricity generated by renewable energy to gas and instead transport it to a different part of the world for immediate consumption, that the efficiency of doing so could be increased 2 or 3 fold or so compared to the round trip of electricity -> gas -> electricity. But it’s unlikely that anything short of a truly global HVDC super grid that crossed vast oceans and spanned both hemisphere’s could vastly reduce the need for energy storage, as seasonal variations in energy demand and weather correlate over vast land areas.
A continental HVDC supergrid could do a lot to smooth the energy demand that relates to daily variations, but then, run-of-the mill batteries with cycling efficiencies of 85%-95% along with pumped storage systems and hydroelectric demand would also have enough storage capacity to efficiently smooth over daily variations in demand.
My conclusion is:
A HVDC super grid would have a marginally positive effect that might be enough to justify it’s cost, but it would be highly unlikely to eliminate the need for extensive energy storage (though it might slightly reduce storage requirements) and thus it is not desperately needed (although I grant you it might still be worth while developing).
Re: Shape of learning curve
Don’t know what you mean. Are you saying that expensive new products go down faster than products that are already manufactured in large quantities?
I agree this is the case, but there are many different kinds of solar technology, standard photovoltaic, thin film, CSP, etc., etc., so, given that the solar resource dwarfs all other energy resources, I think it makes sense to focus the scarce talent of scientists and engineers on tapping a plentiful resource that can truly be scaled rather than wasting it on small pet projects like wave energy.
I’m not arguing that we should focus all effort on the leading form of solar technology (such as standard PV). I’m saying we should focus our efforts on different ways of tapping solar energy that have promising economic potential rather than wasting effort on wave energy or geothermal, for example.
Re: Power to Gas should be used for many different things
Why do you disagree with this? A huge amount of industrial processes currently use natural gas. If gas synthesized from solar energy could be feed into these manufacturing processed and combined with carbon capture and storage at the output end, then a wide array of manufacturing processes, that would otherwise be very difficult to decarbonize, could be decarbonized.
With respect to heating people’s homes. I proposed using combined heat and power plants, which burning synthesized gas, to do this. If you’re going to burn gas anyway, you may as well use the heat output for home heating and the like. This is even more the case when the CO2 is captured and compressed (which increases the ratio of waste heat to electricity)
If you read my article, you’ll see that I also advocated using heat pumps to supply any surplus heating requirement over an above the heat that CHP gas plants output as a side effect of producing electricity during extended down times for renewable energy.
I agree that heat pumps are a more efficient way to convert electricity to heat compared to burning gas – and the article says as much
Re: Carbon tax being socially suboptimal
I’ve been thinking about your point as I write this and I’m willing to concede to you a little bit here. You are probably right that a carbon tax is the best way to reduce DEMAND for fossil fuels – so it does have an important role to play in decarbonization. I’m still inclined to think that a carbon tax is sub-optimal and problematic when it comes to decarbonizing the energy SUPPLY. As it only takes present prices into account and does not take the long term price trajectory of different carbon free energy candidates into account as they scale over time.
I’m particularly concerned about wind energy over shadowing solar power – especially in europe. And I think it is fair to say that, in many places in Europe, even in the presence of carbon prices, wind economically blocks out solar. Even though in the long term solar, or a combination of solar in a sunny place (like Greece, Spain or North Africa) in combination with a HVDC cable linking it to a northern region would almost certainly outcompete wind in the long run.
I’m inclined to yield to your belief that carbon pricing is a positive and important policy.
But I still disagree with the view, “Put a price on carbon, walk away and let the market sort it out.”
If we advocate carbon prices, we need to be clear about how they will be useful as well as what their limitations might be and develop accompanying policy tools to compensate for the shortcomings and limitations of carbon pricing.
Final remarks:
In my view, hydrogen may well be the long term future of energy storage as opposed to power to gas (carbon capture and storage in addition to transportation will be a pain). However, we currently have a large amount of existing infrastructure that is already capable of cheaply storing and transporting huge amounts of gas all over the world.
It has taken us decades to build this gas infrastructure.
In future we could upgrade or replace our existing gas infrastructure to store and transport huge amounts of hydrogen instead and eliminate the need for CCS, but such a project would take decades – or more – to complete and would likely require a lot of R & D and testing.
Pipes that handle methane, can become brittle if used to transport hydrogen. So a lot of additional redesign and testing would be required to build a hydrogen infrastructure – although I completely agree with you that it could be done eventually.
Furthermore, alot of existing manufacturing processes make use of gas. These would need to be completely redesigned to degasify them. Synthetic gas plus CCS is probably the simplest way to decarbonize many manufacturing processes.
On your final point, power to gas, plus carbon capture and storage would emit zero CO2.
For clarity, I personally see Carbon taxes most important role as a supply side instrument for electricity. Although in that case, I don’t recommend a carbon tax — I think we need eFeebates that just take care of the supply side part and avoid any unnecessary demand side part action (because we want to go to electricity not away from it). Then for other fuels – once you have alternatives – you could use Carbon taxes to push people into electricity. Of course, electricity sector also needs to be planned. But carbon taxes can make it economical too even in market based systems. I’ll respond more some other time. Just wanted to make sure I was clear on that point.
“Put a price on carbon, walk away and let the market sort it out.”
I also disagree with this. It’s more a part of the solution but planning and forward looking regulation are just as important.