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Sunday Train: Can Nuclear and Renewable Energy Be Friends?

BruceMcF's picture

There is an ongoing general discussion in the field of sustainable energy that does not carry the risk of the destruction of our current industrial society and economy about variable renewable energy.

Renewable energy includes a range of low or no carbon sources of energy - but not all renewable energy is sustainable, and not all is low or no carbon. And not all low or no carbon energy sources are from renewable energy resources.

Among the sustainable, no/low carbon renewable energy resources, the most abundant involve the harvest of variable renewable energy, with windpower and solar PV being the most notable. So one obvious strategy for a no-carbon-emitting energy system is to base it on collecting as much of these affordable variable renewables as practicable, and then use other no/low carbon sources to fill in the gaps.

However, in some quarters, this elicits a counter-argument. The most "successfully de-carbonized" economies of the world today are either those with a very high reliance on reservoir hydropower ... which while very useful in the United States offers nowhere near a large enough economic resource to meet any large fraction of our current consumption ... or those with a very high reliance on nuclear power.

Indeed, near the beginning of this month, Stephen Lacy briefly reported on a report from the Breakthrough Institute that raised an alarm that the new Clean Power Plan may in fact oversee a net increase in GHG emissions. The final plan does not include measures to avoid the decommissioning of substantial numbers of nuclear power plants. And the numbers are stark:

  • The 30 nuclear plants at risk by 2030 avoid over 100 MMT of CO2 emissions
  • New non-hydropower renewables are expected to avoid 60 MMT of CO2 emissions by 2030
  • New nuclear plants under construction are expected to avoid under 30 MMT of CO2 by 2030

So where retention of those 30 nuclear power plants would find us over 80 MMT of avoided CO2 ahead, and in a position to accelerate that in the following decade ... their closure could leave us over 10 MMT below where we are now.

 
Why I say "No/Low Carbon"

Independent of what is normally called Carbon Capture and Sequestration, the industrial scale process of trying to capture CO2 from large fixed sources and finding a way to push it under ground, there are also a wide range of actually feasible methods of capturing carbon and sequestering it.

"Wait, so why don't we do those, and just go ahead with what we are doing?"

The flip side of this is that the already feasible level of carbon capture and sequestration is quite dramatically overwhelmed by our current scale of CO2 emissions.

We can, for example, plant short rotation perennials in marginal land, convert them into charcoal, and bury the charcoal. If we worked really hard at it, we could sequester what would sound like a large number. But it wouldn't be anywhere near as large as the amounts we are presently emitting.

The scale of "realistic direct-from-atmosphere CCS" that we can actually achieve in not entirely clear, in part because political paralysis has prevented us from getting the start at it to learn more about the possibilities from experience.

But that is what I mean by "low/no carbon". Even if some carbon was emitted somewhere along the way ... eg, in the chemical reaction in producing the concrete for the cement foundation of a wind turbine ... if that intrinsic emission on a per KWh basis is some small percentage of the runaway CO2 emissions of a Natural Gas or Coal Powered generator, it is far more likely to be in the scale that can be mopped up by a feasible scale of "realistic direct-from-atmosphere CCS".

Quantities are important in this. People that treat CO2 emissions as a "sin", and divide the world in a dichotomy of sinners and saved, are at risk of lumping together emission levels when one is twenty, fifty or a hundred times the scale of the other.

And there is a further challenge that a life cycle analysis of the emissions of producing equipment to harvest renewable energy will be analyzing that in the context of an energy supply system that is based primarily on fossil fuels. However, the more equipment we install to harvest renewable energy, the lower the "production" CO2 cost there will be for the next one ... and for everything else that is made using that energy source.

How low we have to go is determined by the rate of "realistic direct-from-atmosphere CCS" we are able to achieve. But it would be absurd to wait to start reducing the CO2 cost of everything we reduce until we have an exact reading on where we need to end up. We already know the direction we need to go, which is "lower", and we know of a range of technologies which, if rolled out, will take us substantially lower.

 
The Simple Economics of Existing Nuclear Power Plants

The reason that the existing nuclear power plants are under threat of closure is, at heart, economic. We pretend that coal and natural gas are not using a scarce natural resource when they emit CO2. We do that by not charging for the use of the scarce natural resource ... the ability of the natural Carbon cycles of our global ecosystems to sequester carbon that we are adding to the atmosphere.

We are, in fact, not only allowing them to use that scarce natural resource: we are allowing them to use it up, and therefore CO2 concentrations in the atmosphere are increasing at what is a an unprecedented rate during our history as a species. And in the process, we are risking catastrophic climate changes that have the potential of destroying our nation as a society and an industrial economy.

If we charged an adequate price for the use of that scarce resource, given the CO2 concentrations we are already on track to have emitted by the time we could feasibly bring new emissions under control ... it would be a price to either prevent the combustion of mineral coal, natural gas and petroleum products in large scale, or else only allow their combustion in large scale if combined with a highly effective carbon capture and sequestration.

And if we charged that price, existing nuclear power plants would be providing quite extremely competitive electrical power, and given that we live in what has been a commercial Republic from its founding, it is very likely they would remain in operation through 2030.

Now, nuclear energy opponents will argue that this is incomplete economics. They will argue that nuclear energy has its own external costs, including for the United States, uninsurable risks of both proliferation of nuclear materials as well as active sabotage of nuclear power plants.

It seems that renewable energy advocates are often in coalition with opponents of nuclear energy. Measures that renewable energy advocates back because they promote renewable energy are often seized upon by nuclear enemy opponents as alternatives to nuclear power.

And in some cases, nuclear energy advocates are aggressive opponents to measures to encourage renewable energy. A core argument is that the most widely deployed new renewable energy sources, windpower and solar PhotoVoltaic (solar PV), are variable sources of energy which undermine the earnings of steady producers of power ~ like Nuclear power plants ~ and require readily dispatchable fossil fueled energy sources with relatively low capital costs ~ like Natural Gas powered plants ~ to operate during the time that the renewables aren't generating.

So we have two no/low carbon alternatives. 100% Renewable and 100% Nuclear.

I think this is confusing legacy technology for technological possibilities. What we have done clearly demonstrates an option, but it just as clearly does not demonstrate all feasible options.

We would have much more freedom of choice if some level of reliance on low/no carbon nuclear energy source was not just compatible with but complementary to som level of reliance on renewable energy.

Well, maybe that is a technological possibility. I am making no warranty of economic feasibility of the nuclear fuel cycle I discuss below, nor any warranty that the scenario I lay out is in the close neighborhood of a cost optimizing no/low carbon portfolio. As I explain, neither of these are actually knowable in advance of further research and development.

I am just exploring one type of scenario where a fleet of so-called "advanced nuclear power plants" acts as a natural complement to a portfolio of both variable and dispatchable renewable energy ... in the context of an electrical grid that is far more suited to the integration of variable renewables than the one we have today.

 
The Distinction between Renewable Energy and Sustainable Low/No Carbon Energy

The first point I want to touch on is that not all renewable energy is sustainable, no or low carbon energy. And it may be that not all sustainable, no or low carbon energy is renewable energy.

For example, lumber harvest for biocoal, whether from old growth forests or from matchstick pine tree plantations, is carbon emitting on a time frame of decades. If its cultivation is a modest carbon consumer then it may well be a low carbon energy source on a steady state basis. However, if it takes 40 to 100 years to growth the replacement biomass ... it takes 40 to 100 years to reach steady state, and it is a carbon emitter (though on a declining basis) for that whole period.

So to be a potentially no or low carbon source on the time scale we need, biomass energy has to be from more rapid growing cycle sources.

At the same time, if its cultivation is energy intensive, whether in fertilizer, the production of poisons (pesticides, herbicides and/or fungicides) that industrialized annual monoculture is heavily dependent upon, in harvest, or in some combination of the three, then it won't be no or low carbon, no matter how fast the growing cycle.

So the target for sustainable, no/low carbon involves a short-rotation perennial such as short rotation coppice or the Miscanthus perennial grass. Long rotation perennials or high-input annuals are, for distinctive reasons much less likely to qualify as sustainable as well as no/low net carbon emitting over the time scale that we require.

And it is not necessarily the case that all energy sources in an entirely sustainable, no/low energy energy portfolio will be renewable energy. While many anti-nuclear advocates argue for the limited sustainability of the current once-through Light Water Reactor fuel cycles, there are also those that make the case for advanced nuclear energy options such as molten salt thorium fuel cycle (warning: Wikipedia machine entry) reactors. This requires further research and development (which may involve crossing one or both of the two "R&D death valleys" unless there is actively supportive federal policy), but thorium is an energy source that is more abundant than uranium (though information on economically viable reserves is not as clear), and thorium fuel cycles can consume dangerous plutonium and breed uranium.

It is also possible to design a molten salt reactor so that it is passively safe against meltdown. For instance, one approach, for designs where the uranium

A principle challenge with the thorium fuel cycle is that in addition to breeding uranium 233, it also breeds uranium 232, which is a hard gamma emitter. This is, after all, one of the reasons why the US dropped development of the thorium fuel cycle: U232 damages electronics, which limits the usefulness of thorium-bred uranium in nuclear weapons - and at least according to the Wikipedia machine (but with a supporting link lost to link rot, when the US military tested a U233 bomb, it had a lower destructive yield than anticipated. U233 and U232 cannot be separated by chemical means, so fuel reprocessing for a semi-closed thorium fuel cycle that recycles U233 requires remote control, radiation hardened equipment. However, the presence of U232 also makes it easier to track the transport to and back from the fuel reprocessing plant, to guard against the nuclear proliferation risks of nuclear fuel diversion, and then if diverted requires isotope separation which is made more difficult by the similarity of atomic weight and chemical properties of U232 and U233.

So the potential of molten salt thorium fuel cycle reactors comes with several caveats, involving safe handling and transport of gamma emitting spent fuel for recycling of Uranium 233. And its development requires substantially more new research and development than "mature" Light Water Reactor fuel cycles. However, the "mature" LWR technology present inherent proliferation risks because the technology was selected to be complementary with nuclear weapons production.

It is plausible that there may be advanced nuclear fuel cycles that may be exploited as a sustainable and no/low carbon energy source, even though they consume an abundant but non-renewable resource. Further active research and, especially, development is required to verify that it qualifies ... in the same way that further field trials are required to determine both the opportunities and limitations of various potential short rotation perennial bioenergy crops.

 
But why do we care? Why not depend on wind and solar alone?

Now, why do we care about biomass energy, or nuclear energy, or any other potentially sustainable, no/low carbon energy sources along those lines? Why not power all of the economy with windpower, solar, and run-of-river hdyro?

As previously covered in the Sunday Train (eg, in Variable Renewables and Dispatchable Demand), these abundant renewable energy resources are variable. They are "use it or lose it" resources, which are harvested when available. Even though the sun is shining on some part of the US for much of the day, part of the time it is night across all of the continental US. Even though the wind is always blowing at useful speeds somewhere in the continental US., the total amount that can be harvested by wind turbines varies. Even though many run-of-river hydropower generators are essentially "always on" except when closed for maintenance, the amount of power they generates varies with the strength of the river current.

Now, electrons are "fungible": the electrical grid does not matter whether a particular electron is being pushed around due to harvest from the wind, or the sun, or from a flowing river. What matters to the electrical grid is the total amount of energy that is harvested. So while each individual piece of energy harvesting equipment is an "intermittent" supplier, which sometimes produces energy and sometimes does not, the total available renewable energy resource is not intermittent. There is always some energy available from a well-diversified portfolio of renewable energy harvesting equipment. However, it IS variable.

And with a portfolio of variable, renewable energy, the problem is as follows:

  • Suppose that a maximum of 80% of installed "nameplate" capacity is available at any given point in time
  • Suppose that an average of 40% of installed "nameplate" capacity is available at any given point in time
  • Take the ratio of the two ... in this case, 40%/80% = 0.5
  • When you have that variable renewables installed equal to that fraction of peak demand, then some of the time you are getting all of the energy that you ever require from renewable energy
  • But on average, you are only getting half of the energy that you need from that renewable energy

As discussed in more depth in a previous Sunday Train (Making An Energy Revolution, 7 July 2015), that gap can be made up in various ways, including:

  • Reservoir hydro, but the total resource is less than 10% of total energy demand.
  • Providing dispatchable demands, so that the daily, and possibly weekly, cycle of electricity demand can better match the
  • Providing flexible dispatchable no/low carbon energy other than reservoir hydro, including biomass ... and conceivably some form of nuclear energy, to the extent it can be operated in a flexible, load-following manner.
  • Overbuilding variable renewable capacity and spilling it. However, the cost is inversely proportional to the fraction of power used, so with each additional 1% spilled, the average cost of the renewable energy harvested and used increases at an increasing rate.
  • Overbuilding no/low carbon energy capacity and storing it for use at a later time.
    • Grid scale battery and pumped hydro storage would be used more than once a day on average (eg, "400+ cycles per year") for best cost-effectiveness, and then with rising cost per KWh, as each halving of cycles per year (200 per year, 100 per year, 50 per year) doubles the fixed cost component per KWh.
    • Electrofuels have far lower "round trip storage efficiency" than pumped hydro storage, and have capital costs in proportion to per hour production capacity, but once produced can have much lower storage cost per KWh stored.
    • Because of round-trip energy losses, it's silly to operate electrofuel production at the time that electrofuel is being used to generate electricity. This means electrofuels for energy storage (as opposed to energy transportability) should ideally be produced most of the time at a steady, and moderate rate, and consumed the balance of the time at a variable and relatively high rate.

So, for example, dispatchable demand that can time-shift 10% of demand to a time of immediately available supply, storage that can time-shift 10% of supply to a time of immediately available supply, and 5% additional variable renewable supply due to capacity that is frequently spilled would (if all three are feasible) allow 75% of supply to be provided from variable renewables, instead of 50%.

Then 15% of supply from flexible dispatchable renewables and 15% from partially load following advanced nuclear power, including 2-3% supply time-shifted through electrofuel production (with, as will be seen below, substantially more peak generating capacity), would be sufficient to close the remaining gap in total supply.

Why did I include that nuclear power share? See above ~ I am exploring the space in between "all renewable" and "all nuclear", so if I set it at 0%, that would be trouble.

These add up to more than 100%, of course, since if there is no reserve, where you are is on the knife edge of a "brown-out economy".

These are simply illustrative shares. The actual cost-effective shares depend upon the cost trade-offs ... how much does this wind turbine cost per KWh nameplate capacity, and what will its production profile be if placed in this location, and how will its output compare to both immediate and dispatchable demands, and how much of its energy is provided when the solar PV supply from that area is not supplying, and how much does this battery cost per KW capacity and how many cycles does it provide, and what is its efficiency, and etc. and etc.

As implied by discussion above (though from the other side of the argument), the principle weakness of conventional nuclear power for use as a complement to variable renewables is its relatively inflexibility. Current French designs can load-follow for half of their fuel cycle. The General Electric AP1000 Pressurized Water Reactor can load follow on a 100-50-100 daily cycle over 90% of its fuel cycle (pdf, sheet 10), so a fleet of two fueled for two years each, with refueling properly timed, could load follow by over 50% of output during peak seasonal net load.

The "mandatory minimum" with these reactors is a technological issue but its conceivable that new research and development will uncover engineering solutions for technological issues.

For one thing, it is conceivable that a molten salt thorium fuel cycle reactor could be made to be even more flexible. It would operate at prevailing pressure but high temperature, so that it could use another molten salt as the heat transfer medium to the generator, and also as thermal storage. This could effectively decouple the thermal output of the reactor from the power output of the generator, allowing the reactor module, with its relatively higher capital cost per KW capacity, to run relatively continuously, and the generator module, with its lower capital cost per KW capacity, to run in a pure load following manner.

Now, this is a close to ideal energy source for methane as an electrofuel, since part of the heat output of the reactor can be used to heat water used for high temperature steam electrolysis (HTE), increasing the hydrogen output per KWh ... and in a combined cycle process, the transfer medium could then be used as a heat source for the catalytic Sabatier process to convert CO2 and Hydrogen into methane and steam ... and then perhaps the steam can be recycled to provide some of the water for further electrolysis. According to the Wikipedia Machine, at 100°C HTE has a maximum efficiency of 41%, but at 850°C, HTE has a maximum efficiency of 64%.

And when generating in peak power mode, heat from the exhaust of the gas turbines can be recovered for a second cycle of thermal steam power or for thermal storage using existing capacities of the generation plant, so rather than the 35%-42% efficiency of a single cycle peaker, I will assume 50% efficiency in electrofuel consumption.

This is a scenario I am laying out, so let me lay out some parameters for the scenario. It may be that some are reasonable, it may be that others are not actually cost effective in practice ... but of course this is all based on a reactor technology that has not yet been developed, so this is rather a look at what might be rather than a prediction of what shall be. In this scenario:

  • HTE is in practice 60% efficient in generating electrofuel
  • The power generation from electrofuel is 50% efficient (though as discussed below, this can be raised substantially)
  • The reactor is in normal operating mode about 90% of the time
  • The reactor devotes two fifths of its output to electrofuel generation while it is in normal operating model
  • The generator module has 150% of the maximum steady state output of the reactor
  • There is sufficient thermal energy store to convert 60% of nuclear reactor capacity into 0%-150% of generator capacity

This means that the electrofuel plant is operating for about 90% of the hours of the year in normal, load following and electrofuel production mode, and 10% of the hours of the year (but not necessarily 10% of the hours of any given week), the facility is in peaker mode, the electrofuel capacity is shut down, and the methane peaker turbines are online and available to generate.

With the main generating plant at 150% of reactor capacity:

  • About 90% of the time, two fifths of the reactor heat generation is used to generate methane electrofuel
  • The same 90% of the time, the generator produces between 0% and 150% of reactor capacity, using three fifths of reactor heat generation
  • About 10% of the time, all of the reactor capacity is used to produce power, electrofuel is used to produce an additional 100% of reactor power generating capacity, and thermal stored power is used to produce up to 50% of reactor capacity, and

Now, after stepping through it, you may wonder why bother with the electrofuel. After all, that 100% of extra generating capacity cost the equivalent of 360% of reactor output. However:

  • In terms of capital cost per additional KWh storage, it is much cheaper to store energy in methane for a week or a month or a year than in batteries or in pump hydro storage. For inter-monthly or inter-seasonal balancing, natural gas may be stored in depleted gas formations as well as aquifers ... and, indeed, you will note 0% natural gas consumption for electricity in this scenario, so the legacy natural gas pipeline and storage system may be used for part of this ... so co-location with a long term methane storage facility is not required. During off-peak hours of peak demand periods, the natural gas may be transferred from long term storage into tank storage if necessary backed by salt caverns, for more rapid extraction during the actual turbine generation periods;
  • During a pedal-to-the-metal transition to low carbon power, the natural gas peaker plants already exist, and are the natural gas generating capacity with the greatest GHG emissions. Also, due to the inefficiency of single cycle turbines and their restricted number of hours used per year, even if Natural Gas industrial scale Carbon Capture and Storage turns out to be economically feasible (which the scenario does not rely upon happening), the peaker plants are by far the least economic for conversion to Natural Gas carbon capture and sequester.
  • And in terms of peak net-load, two and a half times total reactor capacity is a lot of energy, when the reactor capacity is 15% of average energy supply.

This last point is perhaps more confusing for experienced professionals than for novices. The novice says, "yes, two and a half times 15% is 37.5%, that does seem like a healthy slice of power." The professional says, "wait a minute, you are confusing average power output with peak load. Peak loads by definition must be substantially above average load, by definition. "Peak to Average" ratios, the ratio of peak demand to average demand, average between 1.7 and 1.8 in the Mid-Atlantic region of the "PJM" electricity interconnect, and in 2006 hit 1.82.

Except that is pointing to today's fossil-fuel powered grid, which does not have our (assumed) ability to time shift 10% of total energy demand, nor our (assumed) ability to time shift 10% of total energy supply. That is a grid that is able to level out the most commonly experienced daily peaks.

 
A Bridge Over Troubled Water

I've been loosely using the term "peak operation" for these hypothetical nuclear power plants, and in so doing I will have been confusing our hypothetical expert ... which is probably unavoidable ... but also likely confusing you, my dear readers.

For a dispatchable unit in our no/low carbon electricity generating portfolio, its peak operation is not necessarily about an underlying peak demand for electricity. After all, we have variable renewable generating capacity providing on average 75% of total energy consumed. And with our 2:1 ratio between maximum and average renewable energy harvest, during some periods, it might be generating 150% of average energy consumed.

And typical hour to hour swings in power demand during the day are the least expensive to cover with storage and demand shifting, because the annual capital costs are spread out over hundreds of annual uses.

Then there are the expected seasonal swings in both energy demand and variable renewables production. At a level of a feasible solution, these are also straightforward to cope with ... fire up a fleet of biomass powered generators.

Now, it is not guaranteed that this is a solution that we can pursue sustainably at a price that we wish to pay, nor that it is necessarily the cost optimizing solution, but it is a solution that is feasible at some cost that we could pay without crashing our entire economy.

Assuming we can expand reservoir hydro to 7% of capacity, the balance of that 15% dispatchable renewables may be assumed to be some form of biomass. And we can can observe some points about the long term economics of this seasonal back-up biopower.

  • Being sourced by biomass, we have to have a biomass crop production system. For the best prospects of being ecologically sustainable as well as a no/low carbon energy source, any biomass produced in excess of sustainably available wastes should be based on a short rotation perennial energy crop. And perennial crop production does not "turn on a dime".
  • The most thermodynamically efficient biomass seems likely to be biocoal ~ charcoal produced by some variety of flash carbonization under pressure in a sealed carbonization chamber, include treatment of exhaust for pollutants and using the exhaust for co-generation of distributed electrical power.
  • Whether generating power from legacy coal power plants or from direct carbon fuel cells, energy efficiency will be the greatest if run at steadily at the optimal rate, and given a relatively inflexible annual budget, energy efficiency is an important factor.
  • Being seasonal back up power, its capacity factor can be factored into the fraction of the year that it is put into use, and the capacity utilization when it is in use.
  • Roughly half the year, variable renewables will be producing more than average, and roughly half the year, less than average
  • Whatever the make-up of the back-up seasonal power, we will be wanting to start up the most efficient units first, and the least efficient units last.
  • If any are used about half of the time, and all are used some of the time, the average capacity utilization seems likely to be around 20%-30%, so for simplicity I will peg it to 25% in this scenario.

Now, 25% capacity utilization and 8% of total power supply implies a capacity of about 32% of average energy consumption. If average hydropower capacity utilization remains in the neighborhood of 40%, then 7% of total power supply from reservoir hydro implies a capacity of about 17% of average energy consumption.

Now, remember if we are looking at a national portfolio of renewable energy sources offering an average of 75% of annual energy consumption, there is always going to be some supply from somewhere, but it is by no means going to always be 75%. Suppose that the minimum yield is 40% of average yield. Then during the lowest yield period, renewable energy is yielding about 30% of average supply.

Lets add those together ... 32+17+30=79%. Even with emergency demand response measures, on top of regular daily-life dispatchable demands, what we have here is a brownout ... and, especially if average daily demand at this period is above the annual average, perhaps rolling black-outs.

What this portfolio needs is something that can:

  • Act as a load-following supply under normal circumstances
    • Smooth anticipated hour to hour swings in load net of variable renewables supply plus whatever seasonal back-up power is in operation;
    • Cover expected swings in daily demand that are not expected to last long enough to justify turning on or off biomass back-up power plants; and
    • Provide hour to hour reserve to cover for unexpected drawn-downs of reservoir, battery or PHS stored power.
  • And during both steep, unanticipated drops in variable renewables supply (which will happen), and during the steepest annual peaks in load net of variable renewables supply, act as a firming reserve.

And that is what our hypothetical molten salt reactor, coupled molten salt generator, and electrofuel production plant give us. With breathing room on top.

That breathing room on top is important, since if we get far enough ahead on biocoal supplies ... we can bury the biocoal, which is high concentration carbon in a much more stable form than CO2.

And on the other hand, if there is a renewable energy "drought" ... whether affecting hydro, the variable renewables, the biomass, or several in combination ... that breathing room is our margin for error as we ramp up biomass production ... which, for perennials, is a process that rolls out over several years.

 
But Wait, There's More

Now, if the round trip inefficiency of the electrofuel to store electrical energy gets you down ... there's a final point which I have left to one side.

That is Combined Heat and Power.

The thermodynamic efficiency of conventional heat engines is limited by the difference in temperature between the heat source and the heat sink. Natural Gas combined cycle generators get their efficiency increase by using the exhaust of the turbine to water for a steam generation phase, so that the combustion of natural gas in a turbine provides the original heat source and the coolant for the steam phase provides the final heat sink.

But now you have heated your final heat sink, and have to either replace it with a new source of coolant (so-called "once-through" cooling), or you have to cool it back down again. Because you have ... steam or very hot water. And what could you possibly do with a supply of steam or very hot water?

Well, you could run it through pipes built into a heat exchanger with pipes contained a cooler supply of water, and then run those pipes to buildings. During cold times of the year, those buildings could put some of that water through radiators that emit heat into cold rooms ... in the process cooling the water in the radiator. Some of that water could be run through another heat exchanger to help heat a supply of hot water. During hot and humid times of the year, some of that water could be run through a dessicant dehumidifier, to release humidity from the dessicant into an exhaust air stream so that humidity can be removed from the internal air supply, raising the threshold comfort level temperatures of the building and reducing energy demand for air conditioning. Given sufficient hot water in the pipes, and sufficient dessicant, outside air can be super-dehumidified, and then cooled with a swamp cooler, to further reduce (or in some climates, eliminate) the need for electrically powered air conditioning.

And of course, industrial and commercial processes that require heat can use the hot water in the pipes to either provide the required temperature, or else to pre-heat to reduce the energy cost of providing the required temperature.

The thing about CHP is ... all of those uses are doing the work of a conventional cooling tower. A cooling tower may still be needed ... there is no guarantee that demand for electricity and demand for heat through the water pipes will always be in synchronization. But to the extent that the CHP turns the "waste heat" of the second cycle into useful heat for those connected to the CHP steam pipes, then it replaces the alternative source of that heat ... and the round trip efficiency of the stored electrofuel got an appreciable kick. If the total efficiency of the consumption of electrofuel is increased to about 80%, then the round trip efficiency rises from about 30% to about 50%.

And that may not be as cool as a Bass-O-Matic, but its nothing to sneeze at.

 
A Spirited Defence of Nuclear Power

I leave this part to be filled in by advocates for Nuclear Power. I am not mode-advocating here, I am exploring technologies to move to a no/low carbon electricity supply. However, do be careful to be specific about what nuclear power technology you are advocating for. Just as advocating for a passenger HSR train between Houston and Dallas is a quite different animal from advocating for a steam train as commuter rail between San Diego and downtown LA, advocating for each of conventional pressurized LWR, so-called "modular" LWR, and various advanced nuclear reactors ought to, in reality, involve distinctive arguments. If the arguments cannot distinguish between which are more and which are less preferable, it may strike the undecided as simple cheerleading.

 
A Scathing Indictment of Nuclear Power

Again, to be filled in by opponents of Nuclear Power. I am not mode-advocating here, I am exploring technologies to move to a no/low carbon electricity supply. However, do be careful to be specific about what nuclear power technology you are advocating against. Just as opposition to a passenger HSR train between Houston and Dallas is a quite different animal from opposition to a steam train as a commuter between San Diego and downtown LA, opposition to each of conventional pressurized LWR, so-called "modular" LWR, and various advanced nuclear reactors ought to, in reality, involve distinctive arguments. If the arguments cannot distinguish between which is the lesser and which is the greater evil, it may strike the undecided as simple naysaying.

 
Conclusions and Conversations

I post this with great trepidation, since in energy discussions, there are often few troll parties like a renewable energy versus nuclear energy party.

But on the other hand, I have just spent two weeks with me 5 month old grandson, and I don't want him to grow up in an economy continuing to risk catastrophic climate change suicide.

As I have discussed in previous Sunday Trains, we are facing two renewable energy transitions. One of these is the one immediately ahead of us, in which we can roll-out the capacity to tap some 25% or more of our average energy supply from a range of renewable energy sources. That can be done in the context of the energy system we presently have. There will be headaches and difficulties along the way, there could be a wrong turn or two, but in broad outline, that energy transition has already started, and so long as we keep pressing against the defenders of the status quo, we are taking advantage of a downhill push.

However, once we complete that energy transition, we have another one. Armed in part with information presently at our disposal, but primarily with information we will learn along the way during the first transition, we will have to plot out the transition to a completely no/low energy economy. That includes transport energy, industrial energy, residential energy and commercial energy, and it includes the energy we presently consume as electricity and the energy we presently consume through the direct combustion of fossil fuels.

Some pathways that seem plausible today may turn out to be dead-ends. Some pathways that seem to be dead-ends today may turn out to be real pathways. But the more real, feasible options we have available to us at the time that we make that transition, the greater the prospects we have for actually navigating the second transition ... as opposed to allowing our nation and economy to collapse before the end of the current century.

So, what do you think?

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jo6pac's picture
Submitted by jo6pac on

Nukes period, I'm from the school they didn't work. We were to have nukes the back yard powering little middle class homes
Sorry all nuke plants need to be removed from the grid as soon ASAP. Then there the waste problem. I guess govt. Amerika can start a new program to spray the weeds along the road?.

There so many new things coming. How many work I have no idea I but it's cheaper than the endless run at war.

Thanks for writing but my feeling Nukes need to be dead.

If any one lives near by this might be fun
http://www.thebatteryshow.com/

Site interesting but they just moved and are having some problems
http://revolution-green.com/

Fun site and lots near and great green stuff
http://cleantechnica.com/

http://gizmodo.com/the-dutch-railway-could-run-solely-on-wind-power-by-2...
Cold Fusion?
http://www.e-catworld.com/
Covers a lot
http://egooutpeters.blogspot.ro/

BruceMcF's picture
Submitted by BruceMcF on

This goes back to the two dueling positions paragraph I wrote in preparation for this piece going up on Agent Orange next Sunday. It doesn't really make sense to talk about "nukes" as if they were one thing.

What we actually did was to pursue nuclear reactors using fuel cycles that were useful for weapons purposes, and ignored the issue of whether there were nuclear fuel cycles that might be useful for no/low carbon energy but not useful for nuclear weapons.

Part of what we have done with our Great Decade of Dithering on Climate Change is we have used up much of our wiggle room on GHG emissions, and we have now set ourselves in a Faustian bargain with nukes, where if we take out the nukes we have now, we will replaced them with coal and natural gas which will clearly cause much worse damage than the nukes will cause. So even if we aim to shut down all the existing nukes eventually, we have to wait until we are able to pick up the pace of the renewable roll-out.

This piece is more looking at 2030-2040, through, and whether or not its possible that some of the so-called "advanced nuclear reactors" might be complementary with a renewable roll-out rather than antagonistic to it. Indeed, on the waste issue, one thing about the thorium fuel cycle is that it can eat up plutonium, which is a way to eliminate some of the longest lived radioactive poisons in nuclear waste.

V. Arnold's picture
Submitted by V. Arnold on

I am aware there are different types of reactors, including non-breeder types.
As to Thorium? I've been reading about it for years; and frankly, I'm not convinced it's not a scam.
Do you have information, valid information, that a Thorium reactor is a viable science? I've not seen any...
And, if it's as good as claimed; where is it? What is the reason it (Thorium) isn't all the rage in an energy starved world?
Cheers

BruceMcF's picture
Submitted by BruceMcF on

The US does not have a coherent system for developing nuclear fuel cycle technologies anymore ... current reactor projects are recycling the nuclear fuel cycles we developed in the 1960's.

In the essay, I already addressed the reason that thorium reactors were dropped in the United States back when the US government was supporting nuclear R&D through to commercialization ... the fission bombs you can make from reprocessing the nuclear waste from once-through thorium reactors have low yield and require gamma-radiation hardened triggers, while the fission bombs you can make from reprocessing the nuclear waste from one-through Uranium PWR ... which create plutonium rather than consuming it ... have better yield and are easier to work with, for making the fission bomb components of a thermonuclear bomb. Without military backing for continuing R&D on thorium fuel cycles, we dropped that R&D a long time ago.

The two main nations actively pursuing thorium fuel cycles are India, and here in China. China is in a situation where it might not be able to make the transition it requires even with a pedal to the metal roll-out of all available mature no/low carbon energy sources, so its focused on R&D for a variety of potential new no/low carbon energy sources.

As far as whether the thorium fuel cycle will prove economically viable ... we of course do not know that.

After all, if the results of an R&D program were known in advance, it would not be necessary to have one ... we could go directly to commercialization. We know from the work on thorium fuel cycles in the 60's that it works in a technical sense of generating power. We know that it works best at temperatures higher than PWR work at, so its a natural complement for molten salt reactor technologies. We know that the fuel cycles breed U232 along with U233, requiring gamma radiation hardened remotely operated fuel reprocessing facilities.

On the other hand, we certainly have no designs for molten salt thorium fuel cycle reactors ready to submit for regulatory approvals, because the US only did the basic research, it dropped research into the technology before the development phase. There could well be a deal killer waiting for the R&D projects in China and India, which will emerge when they reach the pilot plant phase ... just as there could well be a deal killer waiting for any given renewable energy technology that emerges when it reaches the pilot plant phase (for instance, whether there is any way to mitigate bird kills in tower power CSP).

DCblogger's picture
Submitted by DCblogger on

After 3 mile island, chernobyl, and the disaster in Japan, I think nuclear power must be abandoned. the problem is that when this goes wrong the consequences are so disasterous they cannot be risked. and that puts aside the problem of what to do with the spent fuel rods.

BruceMcF's picture
Submitted by BruceMcF on

This is why I referred to being specific about nuclear fuel cycles above. Current Pressurized Light Water Reactors are nuclear bombs that are managed to prevent them from actually exploding.

It is possible to have nuclear reactors that are passively safe ... that are designed so that if everything fails, they shut down rather than melt down. Those were never high priorities with the US Military Industrial Complex, so we have not pursued them actively.

One approach for passive safety would be for the particular approach in which thorium flouride is mixed with the thermal molten salt, circulating through the U233 that acts as a neutron source that initiates the reactions. The U233 neutron source is sub-critical on its own ~ they are sub-critical on their own in any event, and without the molten sale could be air-cooled in place. And remove the molten salt with thorium mixed in from its neutron source and the reaction stops.

So in this proposed approach, there is an empty, chamber below circulating system for the molten salt. There is a plug made of a material with a melting point below the operating temperature of the molten salt. The plug is actively cooled while the plant is in operation. If the plant loses all power, then the plug is melted by the molten salt, and the molten salt drains into the shut down chamber, stopping the thorium / uranium breeding reaction.

The uranium-thorium thermal breeder fuel cycles produce far fewer plutonium and similar radioactive wastes to begin with. And as discussed here (pdf, page 26f in original), mixing plutonium with thorium in a PWR to dispose of plutonium is 40% more effective in getting rid of plutonium, while producing 20% fewer radioactive wastes.

Downstream is only part of the waste issue ... though it is often a focus, since it is a point of resistance to individual nuclear project proposals. The other side is upstream. Our current PWR are "once-through", which consume the particular uranium and/or plutonium isotopes that sustain the reaction, and so they must be refueled with fuel rods which contain a new supply of those isotopes on a regular basis. So-called "breeder" reactors have fuel cycles that generate the nuclear isotopes required to sustain their reaction, and so are much more efficient in their use of their fuel.

That means that the issues of radioactive and other toxic tailings from nuclear fuel production are on the order of 100x to 1,000x more severe with the nuclear technology we rely upon than with breeder technologies. There are both Uranium-Thorium and Plutonium-Uranium breeder fuel cycles for so called "fast breeder" reactors, but only the Uranium-Thorium fuel cycles are breeders for the less complex "thermal" reactors.

And, of course, Plutonium-Uranium breeder reactors are deliberately making more plutonium, when it would seem to make more sense to be getting rid of plutonium, which is both a long lived poison at low concentrations but also a substantial proliferation risk, since it can be chemically separated ... and since it is feasible to make a fission bomb from nuclear-reactor grade plutonium.

twonine's picture
Submitted by twonine on

Although one might wait 40 years for a particular tree, replacement volume is perpetual if managed well.
http://futuremetrics.info/wp-content/uploads/2015/02/Why_the_World_Resou...

Haven't been a fan of nuclear since reading the industry trying to refute Lovins' three or four decades ago. I can't see much has changed.
http://www.rmi.org/Knowledge-Center/Library/2009-07_NuclearSameOldStory

Improved exergy with CHP, district energy, heat pumps, industrial energy recovery, etc. has great potential.
http://www.annex49.info/background.html

BruceMcF's picture
Submitted by BruceMcF on

On the first point, yes, there is existing wastes from forestry that can be turned into biomass energy sources ... but just like biogas from waste feedstocks, that is not available in the volume required for biomass to entirely fill the role for dispatchable sustainable energy.

As far as energy efficiency ... note that the issue with integrating variable renewable energy is with their share of total energy supply ... efficiency may be critical in allowing us to make the transition, but that is rather due to the pace at which we can roll out renewable energy, rather than the total potential supply.

As far as the nuclear industry, they are quite often noxious. Exelon is an excellent example of a company that tries strenuously to undermine the roll-out of renewable energy due to the underlying conflict created by our energy pricing systems between the current technology nuclear power plants and expanded renewable energy. While that conflict goes away in the short run if there is an effective carbon price, they have clearly decided that fighting the renewable energy industry is easier than fighting the fossil fuel power industry.

And in turn, while we are better off keeping those nuclear power plants running during the first renewable energy transition while we build up our capacity to tap new renewable energy resources, if its done under terms that drives Exolon bankrupt and puts the plants in the custody of an organization that places a higher priority on sustainability, that's fine with me.

And this essay about the possible role of some nuclear technologies in the second renewable energy transition does not involve those current Pressurized Light Water Reactor (PRW) generators to be kept running through the second transition ... in the above scenario, they are, in effect, all replaced by a particular approach to an advanced nuclear reactor.

blues's picture
Submitted by blues on

The answer is: No!

There is no fission nuclear system that can be safe at any speed.

Not uranium, not plutonium, not thorium. They all produce tons of radionuclide materials that cannot be contained and will bring about a permanent extinction event. Think Mars.

Tokamak magnetic confinement systems will never work either. They produce fast neutrons, intense radioactivity, and virtually no energy.

Inertial confinement fusion might work. That involves fusion-igniting small pellets of light elements before they can escape by overcoming their own inertia. There are several ways of doing that.

The rest is all insanity. Unless extinction is considered an option.

BruceMcF's picture
Submitted by BruceMcF on

They all produce tons of radionuclide materials that cannot be contained and will bring about a permanent extinction event. Think Mars.

This sounds like a qualitative claim being thrown at a qualitative argument, which is kind of like bringing a knife to a gunfight. If producing tons of radionuclide material at the rate that a thorium-radium industry on this scale is going to produce a permanent extinction event resulting in the end of all life, why hasn't the production of many more tons of radionuclide material at the rate of once-through PWR already done so?

We are in the midst of one of the largest extinction events that we have detected, and (1) coal, petroleum and natural gas are far more effective as culprits than our nuclear industry while (2) unchecked, the consquences of our actions are going to wreck the capacity of industrial societies to continue inflicting this damage long before it threatens the existence of all life on earth.

blues's picture
Submitted by blues on

The reality is that any kind of fission technology involves vast amounts of messy toxic mining, messy toxic reactor “byproducts,” and problems with messy toxic waste. And inevitable “accidents” (and they are inevitable, so maybe not really so accidental).

Many years ago I moved to a very remote part of New England (the middle of a huge forest). My country neighbors informed me that (presumably in the 1950s) an accident involving a small plutonium criticality explosion had occurred just down the road. I started out to look for this place, but then changed my mind. I'm happy with that decision now. After combing the Internet for a day I found only one small mention of that event. And over the years I accumulated several similar narratives, which are typically known only to people who live near the places where these events occurred.

It's not just about Chernobyl, Three Mile Island, and Fukushima. Although certain people are well aware of it, very few know that one of the reactors at Israel's Dimona blew up some time ago. So it is evident that many disasters involving nuclear fission have been covered up.

Cancer is said to far more common than it was before the nuclear age. Some people even speculate that the entire Pacific Ocean has been virtually destroyed by Fukushima, and I can't completely refute that.

So how much more will it take before we abandon this awful menace?

So many things can go wrong that there seems to be no way to discuss them all. When people suggest “passively safe” fission I just do not believe it anymore. The technology is simply far too messy and toxic. And there presumably exist points of failure we have yet to learn about.

Universities have turned out a great number of nuclear power engineers, and these people naturally tend to become advocates for this technology. But that doesn't make us one bit safer.

I do think a lot more effort should be directed at the development of inertial fission, which could be reasonably safe. (And not just the technologies that depend on enormous lasers.)

BruceMcF's picture
Submitted by BruceMcF on

It's not just about Chernobyl, Three Mile Island, and Fukushima. Although certain people are well aware of it, very few know that one of the reactors at Israel's Dimona blew up some time ago. So it is evident that many disasters involving nuclear fission have been covered up.

This is why I noted the importance of being specific about the fuel cycle when talking about "nuclear". The purpose of the reactors at Dimona was to create plutonium for an atom bomb ... a breeder technology that produces far less transuranic nuclear waste and which recycled U233 would defeat the purpose.

Its not as if the US has seriously pursued nuclear fuel cycles and nuclear reactor technologies that are passively safe and produce less radioactive waste, because they were nuclear technological tracks that were less useful for weapons development.