Green Energy

Even those who are skeptical of extreme climate change would mostly agree that we can’t indefinitely keep pumping CO2 into the atmosphere. The conclusion is that we need to move to alternative sources of energy which do not use carbon fuel.

The cleanest are solar and wind, ignoring pollution due to fabrication and installation, which can be amortized. It seems clear that the developed world is moving to these at a really surprising and significant pace, especially considering the complexity and interdependency of any energy infrastructure.

The pace doesn’t seem satisfactory to those who are convinced of impending doom. However, intermittency is a huge problem. Energy from solar and wind is by its nature highly intermittent. Our ancestors for most of human history had to deal with the intermittency of sun and wind, but it would be a major adjustment for the modern economy.

If you can’t tolerate intermittency, the math is pretty simple. You either have a duplicate energy infrastructure capable of supplying full power when intermittent sources are not functional, or you must double the capacity of the infrastructure so as to top up batteries or other energy storage devices for use in the off hours. Either way, you need to build and maintain infrastructure capable of double the current power, which is economically problematic, because you are still supplying the same end amount of power, and therefore only using half capacity.

If you want to maintain a backup infrastructure which is not solar/wind, it will have to be turned off whenever solar/wind are producing. That will make it impossible to amortize. The renewables will seriously reduce any chance of running the backup during peak hours. The only economic alternative is to double the price charged the consumer.

It is sometimes suggested that a new national power transmission line infrastructure could be used to balance supply over hundreds of miles. However, there is NIMBY resistance to power lines, which seems more defensible after the recent disastrous California fires. Also, there is only a 3-hour time zone difference between the US coasts, so it hard to see how solar balancing would make enough of a difference.

The US uses about 400,000 MWh of electricity per night hour, so 12 hours of backup storage would be just under 5,000 GWh of storage. For comparison, the state of California currently has about 150,000 MWh of energy storage, mostly pumped hydro (see Appendix). That is only about 3% of the storage required nationally, and the true backup requirement is much larger, since I am talking here about only solar; if some of the renewable source is wind, and the wind doesn’t blow, demand will have to be served from backup even during peak daylight hours.

As noted before, generation capacity must be great enough to both supply daytime use and to top up storage; in other words, renewable generation capacity must be about double the instantaneous capacity required by a source that is available around the clock. Worst case, it must cover winter nights at high latitudes, which means up to 16 hours at the latitude of Seattle. There you would need triple the current instantaneous generation capacity.

Battery cost projections are enormous, even though great progress is being made in reducing those costs. Today, a Tesla PowerWall stores 14 kWh and costs around $10k installed. At that price, the current California storage capacity of 150,000 MWh would cost over $100 billion, and as we saw that is only 3% of the total needed nationally, so the total would exceed $3 trillion. Worse, batteries degrade over time and a useful lifetime of 10 years is considered quite good for lithium-ion technology.

According to Bloomberg, battery prices are projected to read $58 per kilowatt-hour in 2030 and $44 in 2035. At that latter price, the California storage capacity of 150 GWh would cost “only” $6.6b, and the national total only $220b.

Of course the US defense budget is about $690b, so some funding could be freed up if we truly believe it is a crisis, and that renewables plus batteries are the only answer. Having to replace those batteries every few years remains a problem, not to mention pollution and toxic waste from production and disposal.

The other problem with intermittency is that when sun and wind are producing, they may well be producing too much. In the absence of adequate battery backup to absorb that power, you have to either shut down or dump energy. So now you are paying for expensive generation facilities, plus backup, with double or even triple the output capacity of the existing infrastructure, and then you are sometimes shutting it down! Insane.

If you really think doom is impending, there are only two alternatives. One is to go immediately and completely to sun and wind, regardless of energy storage capacity. This implies intermittent supply, with a radical impact on modern life and business; essentially, going back to the way of life prior to fossil fuels, when the rhythm of life and commerce was driven by the capricious availability of sun and wind.

Worse, given such intermittency, many households and business will be incentivized to generate their own backup power using fossil-fuel generators. For instance, many owners of electric vehicles plug them in to recharge overnight – what are they to do? Are we going to use governmental force against them?

The other option is nuclear. It is the only non-fossil energy source that can handle the full energy needs of the economy without intermittency. If the alternative is doom, even toxic disposal and meltdown risks have to be considered tolerable.

If someone says to me that AGW is now a crisis, I expect them to also step up to one of these alternatives. Intermittency or nuclear. Anything less says to me they either don’t really think it’s a crisis, or they can’t do math.

A Good Word for Wind and Sun

Let me add a proviso. My argument so far has been focused on replacement of existing infrastructure in countries like the US, where virtually the entire population has its foreseeable energy needs met already, and where intermittency would be loudly resisted. However, the US only accounts for about 14% of global energy usage, and much of mankind still lives in places where intermittent energy is an accepted fact of life, and additional usable energy, from whatever source and however unreliable, would be welcome.

Much of the increase in pollution in coming years is projected to occur due to energy development in such countries. Therefore, for such countries, the economic argument is not the same as it is for the US and other developed nations. There is a ample reason for them to concentrate on renewables, and the benefits could be big.

Other Energy Storage Options

Although the electrochemical battery is currently by far the most researched and developed energy storage option, it is not the only one. Energy can be stored in mechanical devices, gravitational fields and fluids under pressure. However, there are serious practical drawbacks and scaling issues associated with all these options too.

The most basic issue is physics. The electromagnetic force is far more powerful than gravity, and is also utilized far more efficiently by chemical battery action than any other known process.

For example, if you want to use gravity by pumping water uphill, then releasing it to drive a turbine generator, you will quickly realize that an immense amount of water needs to be stored at the higher gravitational potential in order to match quite modest electrochemical battery energy storage capacity.

Several attempts have been made to commercialize energy storage in high speed flywheels. Unfortunately, as cool as they may look, these devices suffer from friction and fragility. Unless mounted on superconducting bearing designs, they lose energy rapidly, and a device spinning at high rpm requires substantial safety measures to guard against damage or injury from disintegration.

Carbon Capture

For the developed world, there might actually be a third alternative (instead of nuclear or intermittency): continue using fossil fuel power generation, but with carbon capture and sequestration (CCS) or reuse. This technology is very much in the early stages, but if you are absolutely against nuclear, and can’t tolerate intermittency, it may be the only game left.

One problem with CCS is the 2nd Law of Thermodynamics. Captured carbon is in a relatively low entropy state compared to free atmospheric molecules. This implies that carbon capture can’t be achieved without a concomitant increase in global entropy, for example, by generating energy to power the capture process. And that raises the question of where that energy comes from, and how much pollution is released as a side effect of generation. Things need to be measured very carefully to be sure that there is a net reduction.

Natural Gas

If natural gas is burned, it produces CO2, but if it is released without burning, methane is a far worse greenhouse gas than CO2 (greater cross section for infrared absorption). There are several major problem areas:

  1. Free methane release due to agriculture and landfills: there are some promising approaches to using so-called trash gas, primarily by collecting it, cleaning it, and injecting it into existing pipelines.
  2. Methane leakage: there is substantial leakage from existing pipelines and last mile delivery systems. The current approach seems to be to identify and cap all leaks. That is kind of like Whack-a-Mole.
  3. Flaring of gas from oil wells: all oil wells produce some gas, and often in quantities which are uneconomic i.e. not worth the expense of connecting to a pipeline. Commonly such gas is flared off – just burned. This is better than releasing free methane but still undesirable, as it puts CO2 into the atmosphere.

Wellhead Processing

A better approach might be to generate electrical power at the wellhead, so there is by definition no chance of a downstream leak. To scale this solution would require amendment of PURPA (the Public Utility Regulatory Policies Act of 1978) which disallows small local generators unless they use renewables.

If that restriction can be overcome, such local electrical generation would also allow the possibility of pumping the CO2 combustion product right back into the ground, resulting in a dramatic reduction in carbon emissions.

Other possibilities exist:

  • Natural gas might be used to charge NG fuel cells at the wellhead; this obviates the risk of downstream leakage.
  • Hydrogen might be produced by reforming of natural gas at the wellhead. There are technical problems with feeding hydrogen to existing pipelines, because the corrosion and leakage risks are greater, although hydrogen is not a greenhouse gas. However, such hydrogen could be used to charge hydrogen fuel cells directly at the wellhead.

Electric Vehicles

Consider further the effect of the accelerating transition to all-electric vehicles i.e. purely battery powered, as opposed to hybrids. Human beings will likely continue to be diurnal creatures, so the night-time demand for electricity, to recharge these vehicles, will do nothing but increase. Intermittency, with mostly nocturnal power outages, will not be an option.

Personal vehicles could be recharged opportunistically during daytime hours, as they are not typically in continual use. This is not so for long-haul truck and rail transport. Air transport is also concentrated in daytime, for many reasons, including safety; not to mention that non-fossil-fuel long-haul air would require truly revolutionary advances in battery technology.

There is fundamental problem here. Absent nuclear power, fossil fuel power generation will continue to be a major source, and the transition to electric vehicles may paradoxically increase demand for it. At least, centralized power generation may be more amenable to carbon capture. Another advantage is that electric motors are more efficient than internal combustion motors, so, even with carbon-burning electrical power generation, there still may be a net reduction in pollution.

New Designs for Nuclear Power

There are promising developments in this area. The rap on nuclear among Green advocates has gone from safety concerns to expense. Perhaps it became clear that nuclear accidents are very rare and very much over-reported. Far more people have died from the effects of air pollution caused by fossil fuels than have died in nuclear accidents; fear of nuclear power is a great example of the effect of “fake news”.

So the argument has now become that nuclear power doesn’t pencil out economically (even Rocky Mountain Institute, which I generally support, takes this tack). In the US, there is some truth to this, much of it due to lack of design standardization, and to a contentious licensing process. Before discussing a couple of new solutions, I might refer back to the previous calculation showing the immense cost of moving to dependence on renewables; if climate change must be abated at any cost, this is the alternative, and nuclear power is hardly more costly.

NuScale is a company in Portland OR which has developed (originally with funding from the US DOE) a modular, compact design – the Small Modular Reactor, or SMR. The SMR is built in a factory, rather than on-site, allowing for savings from production efficiency. If you want more power, you chain together multiple modules, making it scalable and again saving on production cost. A 12-module plant developing a net 683 MW has initial costs under $3 billion, and cost would likely go down with mass production. 400,000 MW, the target figure for the entire US, would then cost a maximum $1.75 trillion, compared to $2.5 trillion for a battery storage system alone – and the battery system still needs generation capacity to top it up.

The SMR also incorporates new safety features: for instance, if the power grid completely fails, the control rods drop by gravity into the core, shutting it down.

TerraPower, funded by Bill Gates, has developed a design for what is called the Traveling Wave Reactor (TWR). This reactor design uses a small core of fissile material to seed a reaction in depleted uranium, enriching U238 into Pu239 in-situ. The depleted uranium is currently waste material which presents a long-term storage problem, so the TWR solves that. It also solves the problem of enriching uranium in a prior process, which presents security and non-proliferation issues.

Unlike NuScale, TerraPower is still in the R&D phase. Cost estimates are not available, though it is promising that its primary fuel is material currently viewed as only waste.

Appendix: California Dreaming

by James Temple, MIT Technology Review July 27, 2018

There are issues California can’t afford to ignore for long. The state is already on track to get 50 percent of its electricity from clean sources by 2020, and in August 2018 the legislature passed a bill that would require it to reach 100 percent by 2045. To complicate things, regulators also voted in January of that year to close the state’s last nuclear plant, a carbon-free source that provides 24 percent of PG&E’s energy [note: according to another source, that is 9% of the total California energy mix]. That will leave California heavily reliant on renewable sources to meet its goals.

The Clean Air Task Force, a Boston-based energy policy think tank, found that reaching the 80 percent mark for renewables in California would mean massive amounts of surplus generation during the summer months, requiring 9.6 million megawatt-hours of energy storage. Achieving 100 percent would require 36.3 million.

The state currently has 150,000 megawatt-hours of energy storage in total. (That’s mainly pumped hydroelectric storage, with a small share of batteries.)

Building the level of renewable generation and storage necessary to reach the state’s goals would drive up costs exponentially, from $49 per megawatt-hour of generation at 50 percent to $1,612 at 100 percent.

And that’s assuming lithium-ion batteries will cost roughly a third what they do now.

Similarly, a 2018 study in Energy & Environmental Science found that meeting 80 percent of US electricity demand with wind and solar would require either a nationwide high-speed transmission system, which can balance renewable generation over hundreds of miles, or 12 hours of electricity storage for the whole system (see “Relying on renewables alone significantly inflates the cost of overhauling energy”).

At current prices, a battery storage system of that size would cost more than $2.5 trillion.

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