Climate science from climate scientists...
1 Jun 2011 by group
A new open thread…
Patrick 027 says
17 Jun 2011 at 10:55 PM
Re Michele – it might help if you specified what you think would happen if all the greenhouse effect of gases and clouds were removed from either Earth or Venus’s atmosphere while leaving atmospheric pressure, and the equation of state for the air (the R, cp, and cv in terms of mass) constant – (not just removing CO2, to avoid dealing with forcings vs feedbacks issues, and leave solar radiation properties as they are, to keep solar heating and it’s distribution constant – yes, this is an artificial set-up but it’s a set-up that isolates the greenhouse effect).
In other words, make the atmosphere completely transparent to radiation of wavelengths longer than about 4 microns and leave everything else (besides temperature, and of course allow associated density changes) constant. Remember energy out – energy in = energy loss.
Greg Simpson says
18 Jun 2011 at 12:02 AM
SecularAnimist, I didn’t see anything there about storage of the solar power. What do you do when the sun goes down?
18 Jun 2011 at 1:04 AM
Of course, the surface and all the atmosphere would have the same temperature that would equal the effective temperature of the planets, i.e. Venus 230K, Earth 255K.
Chris Dudley says
18 Jun 2011 at 7:07 AM
I’m not urging war. But, if we are going to use diplomacy it is important to understand what its backstop can accomplish. This is especially true because diplomatic failure means war with or without climate control being a war aim. Already we see ongoing war partly in response to climate change around the Sudan. We can expect resource wars of the most pointless and degrading sort if diplomatic failure merely results in finger pointing.
If diplomacy fails and nations begin to resort to efforts like carbon tariffs imposed unilaterally, tensions will heighten and war may breakout over those tensions. Once that happens and resolve hardens what war aims are realistic? I was observing that 350 ppm may be accomplished with war alone while 280 ppm may not be. This is owing to the absolute need for for technical sequestration intervention to get to 280 ppm which is not required for 350 ppm since the oceans can absorb the overshoot for that target if emissions end rapidly. It is a qualitative difference between the two targets even if technical sequestration intervention (including agricultural methods) would be needed for either in a slower diplomatically mediated solution.
18 Jun 2011 at 1:03 PM
Greg Simpson wrote: “I didn’t see anything there about storage of the solar power. What do you do when the sun goes down?”
What does who do when the sun goes down?
If you an end-user (e.g. household or business) installing solar photovoltaics today, then most commonly you are grid-connected, so you feed any excess solar-generated electricity into the grid during the day (and with net metering or feed-in-tariffs, you are paid for it by the utility), and you draw whatever electricity you need from the grid at night.
If you are the utility, then solar power is typically going to be part of your energy portfolio, so at night you will turn to other sources, e.g. wind, hydropower, biomass.
Options for storing excess solar energy generated during the day include thermal storage (e.g. with concentrating solar thermal power plants or residential solar water & space heating), batteries, flywheels, fuel cells, compressed air and pumped hydro. All of which are being developed for both centralized, utility-scale and distributed, residential/business scale.
By the way, I think one thing that is going to drive growth in energy storage for distributed, end-user applications in the USA is (ironically) the increasing unreliability of grid-supplied power, as our aging power grid is subjected to the onslaught of AGW-driven weather extremes.
In the nation’s capital region, for instance, where power is distributed mostly through wires strung between wooden sticks, it has now become “normal” to have several major power outages every year due to storms, that can leave hundreds of thousands of people without power for days at a time.
I don’t have any numbers handy, but I’ve heard that this sort of thing is stimulating growing demand for backup power, including both fossil-fueled generators and battery backup. If that market grows it could help lower costs and speed adoption of new distributed storage technologies (advanced batteries, flywheels, fuel cells) for residential & business use, making solar-with-storage more affordable.
18 Jun 2011 at 8:10 PM
Re 353 Michele – yes, the surface temperature would be Te, assuming perfect blackbody surfaces and setting aside the nonlinear relationship between temperature and blackbody flux (the spatial and temporal temperature variations will make the planet radiate a bit more for a given global annual average, but this is a small effect for the Earth’s temperature variations as they are, and to isolate the effect we’re trying to describe let’s set aside how temperature variability would change when removing the greenhouse effect).
But the atmosphere will only tend towards being isothermal within itself and with the surface if all solar heating is at (or below) the surface. Otherwise, direct solar heating of the atmosphere must (in equillibrium) be balanced by fluxes of heat downward to the surface where it can be emitted to space. With no greenhouse effect, the only transport mechanisms left are conduction/diffusion and convection. Thermally-direct onvection may occur associated with diurnal and seasonal cycles in solar heating, but – though I’m quite sure how this would work – I suspect it would tend to occur in a shallow layer as the descending branch must be cooled by conduction to the surface, or by forced downward mixing of heat (from kinetic energy supplied by the thermally direct motions, or tides, which in Earthly conditions don’t have much direct effect on the atmosphere). This type of convection wouldn’t generally sustain an adiabatic lapse rate as it involves cold air masses spreading out on larger horizontal scales underneath rising and spreading warm air masses, rather than localized updrafts and downdrafts or localized forced turbulent vertical mixing. Aside from horizontal temperature variations, there would be no thermal driving of convection in such an atmosphere.
But other than that, you have the basic idea right. So now I’m not sure what your concern was regarding CO2 not doing what it is supposed to do.
19 Jun 2011 at 1:34 AM
@SecularAnimist #355 – you gave a good response to a naive question.
In regard to If you are the utility, then solar power is typically going to be part of your energy portfolio, so at night you will turn to other sources, e.g. wind, hydropower, biomass., it might be worth noting that daytime demand is much higher than night time demand here and in most places I expect. That’s one reason for grid-connected solar pv being so useful even without separate storage, especially on hot sunny days when daytime demand surges from air conditioning.
Edward Greisch says
19 Jun 2011 at 2:09 AM
313 Septic Matthew: “I never use 1800 watts” Do you live in a tent? I don’t believe you ever use less than 1800 watts. Most Americans need more than 10 times that, not counting motor vehicle use, of course. One 15 amp circuit times 115 volts is 1725 watts. Most houses have many 15 amp circuits and several that are 50 amps or more. My house has 2 electric ovens wired for 60 amps each, a 3.5 ton air conditioner, an electric dryer, etc. A 500 amp breaker box is from the good old days. Where do you live?
So to get 60,000 watts, you need 33.3 of those things and that comes to $244,933.33 for daytime and bright sunlight. But I am only paying 7.5 cents per kilowatt hour. Why should I invest more than a quarter million dollars to get electricity at 11 cents per kilowatt hour?
19 Jun 2011 at 7:17 AM
#358 Edward Greisch:
60,000 Watts peak required… wow, our contract is for 6.6KW peak? You just exhibited something persistently disturbing in other parts of the world. Most of the house appliances in our place are in refrigerator terms A++. Garden is lit by LED [at 1.6 Watts a pop], the rest of the house is LED or Saving-Lamps, the heaviest take 15 watts/hour. Anything that is not needed to be on is not in standby mode, no it’s OFF, a requirement now for new items in the UK such as TVs. The amazing thing was that all ”standby” added up in our house to 40 watts/hour… that’s 1kw/day or 35 euro cents day, 120 Euro Annual. Does not bother anyone in the house to flip the group switch when done doing something and kill those little red lights.
PS The A++ fridge actually saves a bunch of food from perishing too before it’s eaten, particular veg+fruit and that is one more up on ”responsibility” towards planet and others walking the surface.
19 Jun 2011 at 8:05 AM
Edward Greisch: You use too much electricity. Cut it out.
Just because ‘some’ is good, that doesn’t necessarily imply that ‘more’ is better.
19 Jun 2011 at 9:35 AM
EG@358 – A 500 amp breaker box is from the “good old days”?? On which planet? In the past a 60 amp panel was the norm for residential, now 100 amp boxes are standard, with some goofy folks thinking they need a 200 amp to support their consumptive lifestyle, but even that big a panel is more often found in commercial buildings.
Better read Septic Matts figures again, an 1,800 watt PV system should supply about 86,000 kwh per year, you need to include a time factor in your thinking – his statement was incomplete: he doesn’t use as much electricity as an 1,800 watt PV system would supply, if you use 60KW continuously, as your figures imply, no wonder you think you need nukes!. In a commercial building that is both a food processing facility and my home, I don’t use half that in a year.
19 Jun 2011 at 10:00 AM
Where is electricity 7.5c a kWh? Hope it’s not coal-powered electricity. If it is, then no wonder the air is being filled with carbon.
60,000 watts peak? Good grief. That high usage will have to be criminalised for home use soon, surely.
Richard Simons says
19 Jun 2011 at 11:45 AM
Sou asks “Where is electricity 7.5c a kWh?”
In Manitoba, standard residential charges are $13.70/month (half that if under 200 amps) plus 6.62c/kWh, but go down to 2.69c/kWh for large industrial users (Canadian dollars, currently close to par with US). It is 98% hydro-power.
Septic Matthew says
19 Jun 2011 at 11:54 AM
358, Edward Greisch: I don’t believe you ever use less than 1800 watts.
My bill for Jun 2011 attests to a consumption of 231 kwh for 30 days. It’s possible that I use at least 1000 watts when baking, broiling, or microwaving, but the last is only for a few minutes per day, and the others a few times per month. Because I have large shade trees, and because I have cool, breezy and dry overnight air, I never use air conditioning, just the occasional ceiling fan. My usage is way below average for my neighbors: why my neighbors sacrifice so much of their income to the power company you’d have to ask them.
361, flxible: Better read Septic Matts figures again, an 1,800 watt PV system should supply about 86,000 kwh per year, you need to include a time factor in your thinking
Let me clarify: that’s 86,000 kwh over the 30 year life of the system. That’s an estimated lower bound: at least 30 years, at least 250 days per year, at least 80% of max rating.
352, Greg Simpson: What do you do when the sun goes down?
For at least a few years, new solar installations are going to be mostly for peak power, which is mostly in the day time on sunny days. This usage will reduce the load on existing power plants, and extend their lifetimes. There will be plenty of backup power from existing power plants for decades, most likely. It’s hard to see clearly past 5 years or a 30-fold expansion of solar power, but existing technologies for backing up solar power will be available at reduced cost eventually (and maybe new technologies will be invented.) Concentrated solar thermal power does continue to provide electricity at night.
Adam R. says
19 Jun 2011 at 1:33 PM
352, Greg Simpson: What do you do when the sun goes down?
The immortal straw man of the solar power detractors rises again.
Joshua Ellinger says
19 Jun 2011 at 1:55 PM
You should add a link for reporting articles that need attention/rebuttal. I’m always skeptical of physicists making climate claims…
Link to by Naked Capitalism…
19 Jun 2011 at 3:39 PM
365 Adam R.: What if you lived in Olean, N.Y. where the cloud layer is usually 11000 feet thick? They see the sun maybe 3 days per year. I live in Illinois now, near a nuclear power plant, but I grew up in Olean. [Ole-AAAn]
PS: There is very little wind down in the valleys where the people live. Wind turbines would have to be on mountain tops and the mountain tops are covered by forest. Mountain tops may be oil company land or park land.
David B. Benson says
19 Jun 2011 at 7:51 PM
Sou @362 — My 51% hydro power is less than that.
Edward Greisch @367 — Some valleys are in effect wind tunnels.
19 Jun 2011 at 8:00 PM
@367: Ah, Olean, NY: it ain’t as cloudy as you think. According to PVWatts v2 (http://mapserve3.nrel.gov/PVWatts_Viewer/index.html ), a fixed panel tilted at latitude degrees receives 4.08 kWH/m^2/yr in TSI there. For contrast, the same panel at latitude degrees in Tucson receives 6.13 kWH/m^2/yr.
19 Jun 2011 at 8:03 PM
Captcha: ditstion that.
19 Jun 2011 at 11:44 PM
One 15 amp circuit times 115 volts is 1725 watts.
EG extrapolates from a max capacity to actual usage, when of course electrical codes are designed such that maximum capacity (leading to a break trip) is never achieved unless one tries very, very hard to pathologically overload the circuit.
I’m sure that EG knows that a 15 amp circuit is seldom maxed out given modern electrical codes that call for an excess of both outlets and circuits.
But he’ll never admit it …
20 Jun 2011 at 5:01 AM
@ 356 Patrick
The added CO2 renders emitting the perfectly transparent atmosphere and catalyzes the making of the meanly adiabatic lapse rate.
Really, the CO2 molecules are heat engines which absorb thermal energy from the surrounding molecules, during the collisions with them, and transform it to EM energy. Hence, it has to be continuously fed with a heat flux given by the ground (assumed as the sole heat source). Given the magnitude of the actual fluxes (few tens of W/m²) the heat transfer can’t be solely by diffusion, the convection is needed too and so, the gradient will fluctuate meanly around the adiabatic lapse rate that represents the conditions for the uniform rising of the air particles.
The temperature of the rising air particles changes continuously according to δT/δz and, above all, their EM energy density varies according to T³δT/δz. Both the gradients are negative because the continuous growth of the geo-gravitational energy that phagocytizes them. The rising CO2 molecules never are in LTE, the thermal energy (needed to excite them) is used for other different purposes (the rising of the entire air particle), there can’t occur any radiative emission. In other words, the gases of the convecting troposphere can emit heat radiation only at least at its top, within an isothermal layer.
The altitude where the emitting layer starts is set by ”(see here)” a layers heated from above (generally the thermosphere and, for the sole Earth, the stratosphere too).
Notice: Earth without oxygen would be Venus-like.
Thus, the temperature profiles of the atmospheric gases are fully explained by the thermo kinetics and by fluid dynamics. The surface temperature is determined by the lapse rate and above all be the altitude where the rising air particles are stopped by the inverted slope due to an external radiative heating of a layer of the atmosphere.
The surface radiation around 15μm is fully thermalized close the ground and can be partially converted back and emitted to space only at the top of the first convective layer above the ground.
20 Jun 2011 at 11:58 AM
More cost-reduction projections for solar PV power:
These are just projections, but real prices are declining. Information that is a year old is really old.
20 Jun 2011 at 1:38 PM
Re 372 Michele –
The vast majority of the atmosphere, by mass and by optical thickness, is in, or at least in a good approximation to, LTE. LTE means that if you take a small enough volume to be considered isothermal but large enough for a statistically-sufficient population of molecules, etc, then the distribution of energy among particles and states, except for photons, fits some thermodynamic equilibrium for that temperature.
It is only photons that make the difference between that and complete thermodynamic equilibrium – the later being a case where, for any type of photon, in any direction, at a given location (and time), is being emitted toward a direction and absorbed from a direction at the same rate, a rate that is proportional to the Planck function times the density of emission cross section, which is equal to the density of absorption cross section (these two cross section values are proportional to emissivity and absorptivity over infinitesimal path lengths). Also, in complete thermodynamic equilibrium, the brightness temperature of the radiation must be the same in all directions, frequencies, and polarizations.
When non-photon matter is not in thermodynamic equilibrium with photons, if the interactions with photons are sufficiently infrequent relative to the interactions among non-photons, then the energy distribution among non-photons can be maintained near LTE even though photon interactions could perturb the system from LTE. This is the case in the vast majority of the atmosphere by mass and by optical thickness; hence, CO2 molecules – among others which can emit and absorb radiation at various frequencies (with spectra affected by line broadenning mechanisms!), are gaining energy from and losing energy to other molecules at a sufficient rate that even as the molecules in states that can emit photons lose energy to photons, and molecules in states that can absorb photons gain energy from those photons, with the later occuring at rates dependent on the incident photons, the population of molecules in either state for a given type of photon is held near what it would be at LTE, and so emissivity = absorptivity for a given path length, and the molecules emit and absorb photons, both occuring at a rate proportional to absorption or emission cross section (a measure of optical properties), and one at a rate dependent on the local temperature of the air (which is about the same as that of the molecules which are emitting and absorbing photons, because LTE is approximately sustained), and the other at a rate dependent on the brightness temperature of the incident radiation, which depends on temperature at other locations, those locations being determined by optical properties.
You can have radiative equilibrium where photons carry all the energy through the atmosphere even if the atmosphere absorbs some of them, even if the mean free path of photons (in a given direction, at a given frequency, and polarization if relevant, the mean free path is the distance which has optical thickness of 1; for the greenhouse effect we are actually concerned with the displacement between emission and absorption of a photon, which is the same as a free path only if there is no scattering (or reflection or refraction), but increases in optical thickness from scattering have the same qualitative effect) is significantly shorter than the thickness of the atmosphere – provided that the convective lapse rate is sufficiently large and the net flux needed for equilibrium is sufficiently small that the situation doesn’t become unstable to convection, and provided no other complexities (setting aside horizontal variations in solar heating, etc.).
In fact, I think this may be the case in the radiative zone within the Sun. Convection occurs above this zone, and the photosphere is the region that emits photons to space – the Sun is most like the version where emission to space occurs at/near the tropopause, but even in the sun, all layers have emission and absorption of photons, with some resulting diffusion of energy via radiation, in addition to convection (where occuring). On Earth the convecting layer is intermediate between very opaque and completely transparent over some frequency intervals (depending on humidity and cloud cover), and at these parts of the spectrum, a significant amount of radiation may be emitted from deep within the troposphere directly to space
(except for some absorption by the stratosphere, though the stratosphere (and everything above) is generally more transparent then the troposphere, except (at least for the upper troposphere (?)) maybe in the LW band of the ozone layer (?) when the troposphere is dry enough are – so typically when a sizable fraction of emission from the lower troposphere or surface can reach the stratosphere, a sizable fraction of that can reach space)
and to the surface (though this is less the case for ‘backradiation’ because the optical thickness of water vapor is, along with the vapor itself, concentrated in the lower troposphere nearer the surface – even aside from the effects of line broadenning and line strength variations).
A radiative equilibrium profile has a warmer surface and ‘superadiabatic lapse rate’ from the surface up to some height. Convection maintains a temperature profile that is cooler at the surface and warmer at some levels. This leads to net radiative cooling within a layer of the atmosphere, which balances the convergence of the the convective heat flux. Convection doesn’t necessarily continue unabated from the surface to the tropopause; on Earth (global annual average) the flux tapers off going upward, gradually to zero at the tropopause. It heats the whole troposphere, balancing net radiative cooling. (You could also have a situation where convection cools some layer of atmosphere and warms the layer of atmosphere above it, with the convective flux increasing with height before decreasing. You can also have a stable layer underneath a troposphere – if conditions allow it.)
20 Jun 2011 at 1:44 PM
but even in the sun, all layers have emission and absorption of photons, –
Actually that may be mainly scattering that occurs within the Sun (though I think (?) this may not be the same type of scattering that dominates Earth’s atmopshere’s effect on sunlight – this preserves photon energy; other types of scattering are sort of a combination of absorption/emission and scattering, which is more complex to describe) – but I think that’s a more complex situation in some ways that what happens in a planetary atmosphere.
20 Jun 2011 at 1:49 PM
… or maybe the convective zone in the Sun is more opaque (for a given distance) than the radiative zone. Gravity varies with depth, other stuff…
20 Jun 2011 at 2:15 PM
Sorry about the double post on Olean, NY. There is an error both posts. The quantities are in kWH/m^2/*day* as averaged over a year, and not “kWH/m^2/yr”. Big difference!
20 Jun 2011 at 2:57 PM
In the deep interior of the Sun, Thompson scattering is quite important, however, free-free opacity becomes dominant followed by bound-free and bound-bound opacity followed by H- opacity out into the photosphere. Some brief notes here: http://www.astro.princeton.edu/~gk/A403/opac.pdf
20 Jun 2011 at 3:21 PM
… also, even when the net LW flux goes to zero, as it tends to do when optical thickness gets larger and larger on smaller scales, this doesn’t mean emission and absorption stop – actually, the emission and absorption rates per unit volume increases.
20 Jun 2011 at 3:26 PM
Re 378 Chris Dudley – thanks; I previously knew of Compton scattering and Raman scattering as examples of scattering where net energy is transfered.
20 Jun 2011 at 3:55 PM
… without knowing the details of all types of scattering, it can be pointed out that when there is transfer of energy between photons and non-photons, photon energy is being absorbed and ’emitted’ even though the photons are not, and – at least if this is occuring spontaneously – the direction of net energy transfer for the populations of particles should be from higher to lower temperature – if the photons have higher brightness temperature than the non-photons then the non-photons will be heated by the interaction while the photons will be cooled, and the opposite will occur if the brightness temperature of the photons is lower than the temperature of the non-photons (at least if the non-photons are at LTE). (Also, when photons are scattered without losing or gaining energy, there is an overall tendency for photon intensity to become more isotropic – the directions with higher brightness temperature would lose more photons to directions with lower brightness temperature than they would gain from those directions.) Thus, the brightness temperature of the radiation is still shaped by the temperature of where it last interacted (with gains or losses in energy) with non-photons; as with complete emission and absorption of photons, the net radiant flux will tend to be from higher to lower temperatures, for temperature variations generally on the scale of the mean free path (except for the effect of scattering and reflection that preserve photon energy) or something related to that.
20 Jun 2011 at 4:34 PM
371 dhogaza: “But he’ll never admit it …”
We hope circuits are not maxed out. But we have circuit breakers, just in case. Average use is generally much less than rated use.
368 David B. Benson: “Some valleys are in effect wind tunnels.”
Not my valleys. But that would be nice sometimes.
370 Meow: http://mapserve3.nrel.gov/PVWatts_Viewer/index.html
gives you Bradford PA for Olean, NY. Bradford is on the south side of Mount Hermans. Olean is on the north side of Mount Hermans. When you cross Mount Hermans, the weather changes. It gets suddenly colder and cloudier on the north side of the mountain. Olean is too cloudy to give that solar cell output most of the time. I have driven over Mount Hermans many times, back in the 1960s. GW has had a great effect on Olean. In the old days, it snowed 450 inches per year. Now it snows only 96 inches per year, last time I checked. NREL did not actually measure over a whole year in Olean. A one day measurement has a very good chance of not being the average. The snow amount varies greatly over a 20 mile distance in that vicinity. I have not been back there since the 1970s.
“Domestic (US TMY2) or International Hourly Site Displays the latitude, longitude, state, region, location and/or country of the hourly station located closest to the point queried. Additional information such as a WBAN number or Station ID may be provided. This information is sent to PVWatts for use in the calculator.”
“Each grid cell displayed in the PVWatts Viewer is a 40km x 40km area of interpolated solar resource data assembled using the Climatological Solar Radiation (CSR) model. Grid cell resolution is driven by the input data base components used to run the model.”
20 Jun 2011 at 5:06 PM
Re Michele – more (perhaps a little nitpicky, now, I admit – then again, it may help clarify things) –
Really, the CO2 molecules are heat engines which absorb thermal energy from the surrounding molecules, during the collisions with them, and transform it to EM energy.
Heat engine: Heat Qh in at Th, heat Qc out at Tc; entropy transfer = heat/temperature; entropy can’t be destroyed in net (it can be removed from a system that isn’t closed or isn’t isolated – it may follow a flow of energy or matter, such as when an object loses heat); conserving entropy would have Qh/Th = Qc/Tc, hence (Qh-Qc)/Qh = (Th-Tc)/Th = 1 – Tc/Th, which is the fraction of Qh available to do work. Reverse and you have a heat pump (the kind that converts work to heat while pumping heat up a temperature gradient – as opposed to a pump that moves fluid around which carries stored heat, a different concept). So you are saying that the photon emitted from a molecule is work? Taken in isolation, anything could be said to do work. A single molecule bumping into another may be doing work on that molecule or getting work done by that molecule. When you have a lot of this going on without a paricular organized pattern (except for those patterns which emerge from the disorder, such as a Boltzmann or Fermi distribution, or the shape of the Planck function), then on the macroscopic scale it is not work. A bunch of molecules moving randomly can do work on each other, but on the large scale they don’t do work on another box of gas or fluid/etc. – unless they are at a different pressure (or different osmotic pressure, or …), in which case there is some level of organization so that the random processes on each side are not doing the same exact thing and one system may push another, … etc. Consider the photons. A single photon is a wave that may do work on something capable of interacting with it in that way. But a lot of photons together, distributed in direction (per steradian), frequency or energy (per hertz, or per Joule – as in measuring an interval of the spectrum), polarization (per – how do you measure that?), phase (per radian), and time (per second), don’t do macroscopic work (PS, as I understand it, the more spread out a given non-overlapped population of photons are in any of these dimensions, the lower it’s brightness temperature) … unless they are providing heat to a heat engine – or something thermodynamically analogous (solar/photovoltaic cell, chemical reaction, etc.). If you have a bunch of monochromatic photons in phase (of some polarization?), then maybe you can recieve them with an antenna and do work on electrons.
The temperature of the rising air particles changes continuously according to δT/δz and, above all, their EM energy density varies according to T³δT/δz. Both the gradients are negative because the continuous growth of the geo-gravitational energy that phagocytizes them.
Credit for using a biological term (I’ll assume it’s a correct term – phagocyte sounds right, not sure of the use as a verb) metaphorically, but it’s not like the gravitational potential energy is looking around for other forms of energy to ingest. Well, I suppose it is, in that the APE (available potential energy) in the form of potential density variations, under the force of gravity, will be ‘pulled’ by gravity into kinetic energy. But see, the gravitational potential energy is actually reduced by that process (the total APE may exist in some combination of internal energy and graviational potential energy, depending on whether the potential density variations are from temperature or latent heat variations or compositional variations; for an ideal gas in hydrostatic balance (in the beginning and end if not in the middle of the process), at least in certain circumstances, as I understand it, APE corresponds to enthalpy, which is partly internal energy and partly work, the work itself corresponding to the increase in gravitational potential energy of the overlying air when some parcel of air expands upon heating. It should be noted that only a fraction of internal energy and gravitational potential energy are in APE; setting aside barotropic pressure variations, when potential density surfaces are everywhere horizontal, APE is zero. Particular distributions of diabatic heating or cooling produce (or consume/destroy) APE, and adiabatic motions convert APE to kinetic energy (thermally direct) or vice versa (thermally indirect), and kinetic energy is dissipated (into heat) by viscous processes, and also, kinetic energy can be converted to APE while destroying (at least some(?) of the same) APE in turbulent mixing against stable stratification.
Anyway, radiation is not appreciably ‘eaten’ by gravity in Earthly circumstances; gravitational red shift (and lensing, for that matter) are not significant enough to be important in affecting climate.
20 Jun 2011 at 5:18 PM
Re 382 Edward Greisch says:
We hope circuits are not maxed out. But we have circuit breakers, just in case. Average use is generally much less than rated use.
But how often are all the circuit breakers in a house activated at once?
“Each grid cell displayed in the PVWatts Viewer is a 40km x 40km area of interpolated solar resource data assembled using the Climatological Solar Radiation (CSR) model. Grid cell resolution is driven by the input data base components used to run the model.”
So you could get power from your neighboring communities using grid-connected PV systems (depending on how transformers would handle a backward flow of energy?). Anyway – maybe this doesn’t do much for Olean if it’s cloud cover is too thick, but generally PV cells can use diffuse solar radiation as well as direct, and diffuse radiation is present even with overcast skies. Maybe you’re aware of that and were pointing to the small amount of total insolation at Olean, but I mention it because it’s a potential misconception that PV cells can only use direct sunlight – when it’s ‘sunny’ ((?)maybe some are only effective in direct sunlight because of fill-factor issues and resistance within the system or(?)…)
Pete Dunkelberg says
20 Jun 2011 at 6:09 PM
[edit – OT]
20 Jun 2011 at 9:02 PM
Re Michele – farther clarification –
First, regarding APE conversion to kinetic energy in hydrostatic conditions – this does result in a decrease in gravitational potential energy for the whole system – of course some parcels experience an increase, others however experience a decrease.
The temperature of the rising air particles changes continuously according to δT/δz … The rising CO2 molecules never are in LTE, the thermal energy (needed to excite them) is used for other different purposes (the rising of the entire air particle),…
Yes, the temperature adiabatically decreases as the air rises (and adiabatically increases when it sinks) but
1. the mechanism through which this occurs is the change in pressure as one moves vertically. The equation of state requires the gas either expands or cools as pressure decreases; the first law of thermodynamics determines which combination of cooling and expansion result.
Consider that warmer air rises not because heat drives it upward but because in hydrostatic balance, pressure decreases with height less through a less dense medium; temperature variations cause density variations which cause pressure variations that accelerate circulations where warmer air rises and cooler air sinks.
2. While air rises, the temperature changes, but it doesn’t go to zero and then come back to some nonzero value when the rising stops. As long as it is nonzero, emission can occur as optical properties allow. Molecular collisions also continue to occur during ascent (and descent).
20 Jun 2011 at 10:49 PM
“Progress” on the political front: I have been told that to get into the Democratic primary in the new US 17th district of Illinois, I need $1/4 Million. Or forget it. The new Illinois district maps are out and available at http://www.ilga.gov/CongressionalDistrictMaps/Statewide%20View.pdf
I still plan to try to get involved somehow. I expect to be very unpopular because GW is an unpopular issue. I have some of the names of candidates. They are wealthy.
21 Jun 2011 at 12:22 AM
384 Patrick 027: The point is that with a cloud layer 11000 feet thick, daylight is dim in Olean compared to most places, not just diffuse. Clouds don’t act like a single surface. They act like optical depth. Light is scattered back spaceward everywhere in the clouds. I don’t know how much is absorbed. Power from neighboring communities defeats your purpose of getting off the grid. New York state isn’t California. I prefer New York state. Your eyes last longer in N.Y.
Estimating I use 0.01% of my house’s rated electric power on average. 1 part in 10,000.
21 Jun 2011 at 11:16 AM
As far as I know, the specific energy of the moving air particle is E = CpT + u²/2 + gz + ρλ/ρ, where ρλ is the radiant energy density α(σ/c)T^4 and ρ the air density. The parameter α takes into account the contributing % of the total spectrum. More than the absolute value it is worth the change ΔE = CpΔT + Δ(u²/2) + Δ(gz) + Δ(α(σ/c)T^4/ρ) = CpΔT(1 + A + B + C) where we can be neglected if they are lesser than ε%. Assuming, e.g., ε=5%, Δ(x)=x (all the terms change starting from zero) and T = 300K, u = 100 m/s, z =10000 m, we have
A = 50/300000 = 1.67e-2 < 5e-2 : negligible
B = 1e5-3e5 = 33e-2 : NOT AT ALL NEGLIGIBLE
C = (α/ρ)1.97e-16*300^4/300000 = (α/ρ)5.3e-12: absolutely negligible
Thus generally ΔE = CpΔT + Δ(gz) with excellent approximation and ΔE = CpΔT if Δz is lesser than 1500 m.
Only if T = constant (as for liquids) we have ΔE = Δ(u²/2) + Δ(gz)
I prefer to think in terms of energy because it is function of state and so we never compute the works pδv and vδp along the traveled path.
21 Jun 2011 at 11:19 AM
… = CpΔT(1 + A + B + C) where A, B, C can be neglected if they are lesser than ε%.
Rod B says
21 Jun 2011 at 2:32 PM
flxible (361), I haven’t read all related posts and might be out of context, and I’m not sure if I’m challenging your basic point, but how does a 1800 watt PV system provide 86,000 kWhr per year?
21 Jun 2011 at 2:36 PM
ps, per 364, never mind!
21 Jun 2011 at 5:01 PM
Re 387 Edward Greisch – I generally welcome candidates who see the importance of the GW issue; you might want to have an explanation prepared regarding (one of?) your last morality comment at the Nobel Laureates thread.
Re 388 Edward Greisch – The point is that with a cloud layer 11000 feet thick, daylight is dim in Olean compared to most places, not just diffuse. Accepted.
Clouds don’t act like a single surface. They act like optical depth. Light is scattered back spaceward everywhere in the clouds. I don’t know how much is absorbed. Yes; and forward scattered. From an airplane looking down you can sometimes see some clouds, not in any shade, that look a bit gray compared to brighter thicker clouds. Those thin clouds would appear bright from below. Multiple forward can scatterings produce more backscattering in effect; for stratiform clouds, I think absorption is supposed to increase with the sun closer to overhead.
Power from neighboring communities defeats your purpose of getting off the grid. New York state isn’t California. I prefer New York state. Your eyes last longer in N.Y.
And there’s a reduced (though not nonexistant) earthquake risk! And there’s maple trees.
Maybe I missed something in the thread, but it’s not my purpose to get off the grid. The advantage to getting off the grid is that you’re immune from ‘their’ blackouts and brownouts; the disadvantage is you’re at greater risk of having your own, and/or you’d need batteries or backup power and/or a more severe lifestyle adjustment.
What I’ve heard is that there is, or was, some concern about grid-connected solar roofs when a power outage occurs, particular due to line damage, as electricity in the grid that needs repairs could be trouble. Presumably you could just have the inverter cut power when it no longer detects the AC signal of the grid power (?) – but that still forces the building to participate in the outage. Unless a device disconnects the power from the grid so that the building’s own sources can power the building. Maybe this can work in nested fashion – if power supply is cut-off to a community, the community could have a device that cut’s their own power off from the grid but sill distributes it within the community. When the power supply from the larger grid is detected again, it could switch back. Or maybe the power company would send out a seperate signal giving the all clear? But I don’t know how feasable or infeasable this type of thing would be.
21 Jun 2011 at 5:48 PM
Re 389 Michele
specific enthalpy h = cp*T
kinetic energy/mass = |u|^2/2
gravitational potential energy/mass = gz
radiation energy for photons in equilibrium at T (and n=1):
σ*T^4 / pi = full spectrum blackbody intensity (pi = 3.141…)
= photon energy per steradian per unit area per unit time
σ*T^4 / (pi*c) = photon energy per steradian per unit area per unit distance = photon energy per steradian per unit volume
Multiply by 4*pi steradians for isotropic radiation:
radiation energy density = 4*(σ/c)*T^4 ; divide by ρ to get radiation energy per unit mass.
Aside from spectral considerations (your α less than 1), why is this four times larger than your expression? Because I included the photons going downward as well as upward, and I accounted for the fact that each of those fluxes has photons going in all direction within each hemisphere. The photons travelling nearly horizontally are moving much more slowly that c in the vertical direction.
But why bother with this? Once photons are emitted, the energy can be considered to be seperate from the energy of the air. Photons can potentially travel long distances. Only when scattering optical thicknesses are very very very large on the scale of motion, or the ***index of refraction is very very very large (***in such a way that the group velocity is much reduced – because actually the refractive index only directly pertains to phase speed), and/or the motion of the fluid is extremely fast and parcels of fluid are very very large, does it make sense to think of radiation energy being carried along by convection. Alternatively, if you have phosphorescent material, then it can be that radiant energy is in effect being transported by fluid motion, although their is generally a photon energy change. Generally, LW radiation is often not locally in equilibrium with non-photons; it gets close when opacity is larger over nearly isothermal distances.
You can, at least in Earthlike conditions (or any familiar planetary atmosphere, at least), seperate the radiation energy density from the energy density of the other material. The later changes when radiant energy is absorbed or emitted; the flux of energy matters directly, you don’t need to consider the amount of energy stored in radiation; photons are so fast that relative to distances in familiar planetary atmospheres, it would make no real difference if they were absorbed (or they escaped) the moment they were emitted (or they entered), at any distance within the system.
10000 m * 9.81 m/s^2 = 98100 J/kg
1004 J/(kg*K) * 300 K = 301200 J/kg
(100 m/s)^2/2 = 5000 J/kg
4*(σ/c)*T^4 / (1 kg/m^3) (at 300 K)
4*459 W/m^2 / 3 E8 m/s = 6.12 E-6 J/m^3, divide by rounded typical air density, 6.12 E-6 J/kg
Yes, radiation density is negligible. But radiant fluxes are not.
Remember, when air rises or sinks adiabatically, the temperature doesn’t go to zero. It changes gradually over some range of nonzero values. So if it has optical thickness, it can emit as well as absorb photons.
PS maybe there’s confusion because diabatic heating is not adiabatic. Well, atmospheric circulation is not generally adiabatic, but adiabatic processes can be isolated. The process over time can be broken into time steps as in calculus. Air is moving and being diabatically heated or cooled: This is like moving a little adiabatically, possibly changing pressure by a tiny amount, then gaining or losing a tiny amount of heat at constant pressure (hence the more general use of cp as opposed to cv), and then moving again, etc. Integrate over time. This is how one could compute a moist adiabatic lapse rate, where latent heat is being converted to sensible heat or vice versa. But the air is also radiantly cooling or heating. So why should a troposphere even tend toward an adiabatic
Brian Dodge says
21 Jun 2011 at 7:09 PM
“Presumably you could just have the inverter cut power when it no longer detects the AC signal of the grid power (?)” Patrick 027 — 21 Jun 2011 @ 5:01 PM
It can be done simply – if you are supplying 10kw to the grid (~220v @45 A) and the external power supply goes down, all you need is a 50A circuit breaker, which will trip when the demand from the collapsing grid exceeds its trip point. This may cause problems if your local power source can’t drop its output back from the lost 10kw load and the voltage soars; this is a problem with utilities that have slow responding rotating generators, e.g. steam turbine driven Nuke/coal stations(see http://en.wikipedia.org/wiki/Northeast_Blackout_of_2003), and can be a problem with wind power. The electronic inverters that convert DC from solar PV to AC can be, and usually are, designed to rapidly adjust their outputs so that the voltage doesn’t soar. The High frequency synthesized pure sine wave inverters common now can adjust their voltage & power factor(phase of current to voltage) with subcycle response.
Systems are rapidly moving towards networking among inverters, PV power preconditioners, grid ties, and other equipment – this could lead to the utility continuing to accept power you are providing to supply some of their customers, for instance the local hospital, police, and emergency services, while shutting down less critical loads to accommodate outages. People have died during blackouts because a few thousand watts of power that traffic lights in a metro area require was lost along with the megawatts that would have run fridges, freezers, stove, and air conditioning.
Duke U. hospital has special outlets that are connected to automatic UPS’s which have automatic start diesel backup generators, and the power never goes away in an unscheduled outage. They are tested at full load every 6 months (a tractor trailer full of nichrome heaters and big fans – a 6.5MW hot air gun), and reserved for life support and biohazard containment equipment.
The local utility also has equipment and procedures that make the hospital the last place to lose power and the first to regain it when hurricanes, ice storms, etc damage the grid. How much money would we save, and how much better would life be if this kind of prioritization could be extended community wide?
Adding “smart grid” features that allow alternative energy sources will also make the grid MORE fault tolerant and reliable.
“Duke Energy Carolinas’ current demand response programs include load control curtailment programs, interruptible power service, standby generator control, and residential service controlled water heating. The load control curtailment programs include residential air conditioning direct load control with approximately 190,000 customers and residential water heating direct load control with approximately 35,000 customers. The interruptible programs include approximately 150 commercial and industrial customers with interruptible power service and 150 commercial and industrial customers with standby generator control. These interruptible programs reduce summer 2006 capacity needs by an expected 766 megawatts.”
How much can we save? – That’s worth 3/4 of a 15 billion dollar new 1 GW nuclear power plant, from just a fraction of Duke Energy’s 4 million customers. http://www.duke-energy.com/about-us/cliffside-qa.asp (My utility company)
21 Jun 2011 at 8:51 PM
Brian Dodge @395 — Your cost estimate for a new NPP is too high by more than a factor of two.
But then all of this (poorly informed) comment on electic power sources ought to be off-topic here on Real Climate. It certainly lowers the value of this site IMO.
21 Jun 2011 at 10:16 PM
Re Michele – it also should be noted that 100 m/s is not really typical of most of the atmosphere. I think the rms value is 17 m/s but I’m not sure – maybe that’s the average. The kinetic energy produced in smaller scale vertical motions like updrafts in thunderstorms tends to be dissipated more quickly; the kinetic energy built up in the atmosphere tends to be more in the larger-scale horizontal circulations, which includes jet streams.
21 Jun 2011 at 10:36 PM
Re Michele, continued …
…So why should a troposphere even tend toward an adiabatic lapse rate. Because as long as the lapse rate is superadiabatic, overturning will tend to occur. Net radiant heating at the surface (in the global annual average; at some times and places this isn’t the case) and net radiant cooling of the troposphere in general would, left on their own, not only make a layer of air unstable to moist localized convection but go so far as to make it unstable to dry localized convection.
With latent heating in updrafts, updrafts tend to follow moist adiabats. One can imagine a large area of slowly rising air that is being radiatively cooled so that the temperature falls faster with height; however, with such a higher lapse rate, the situation is unstable and more rapid overturning will tend to occur.
Moist convection involves clouds; the interiors of thick clouds would tend to have minimal net radiant heating or cooling but there can be enhancede radiant heating or cooling at the cloud edges.
Moist convection doesn’t have to occur when the atmosphere is unstable to it, but perturbations can kick it off, and once you have a sufficient updraft, it can power itself. And these perturbations occur. Precipitation removes some water so descent can evaporate clouds at higher levels than the original cloud bases of moist convection, and after that there is dry descent – without net radiant cooling, this would tend to follow a dry adiabat, which would result in descending columns or air warmer than the rising moist updrafts. Yes, you could lower the temperature sufficiently at great height (at the tropopause) such that descent would only warm the air up to the same temperature as is present underneath updrafts, but that’s not generally what happens. Anyway, not all of the air in updrafts reaches the tropopause.
There is also horizontal variation in net radiant heating and cooling – on the large scale this produces large-scale APE which is converted to kinetic energy by large-scale overturning (such as in baroclinic waves in particular) in which cooler air slides under warmer air – this process can reduce the lapse rate to below convective values (especially in frontal zones, although areas of low stability may be near fronts). At high latitudes, particularly in winter, and at night over land in some conditions, the air in the lower troposphere can be especially stable. But in the global annual average, radiant heating and cooling tend to destabilize the troposphere.
21 Jun 2011 at 10:48 PM
Some good news:
Federal Pollution Laws Drive Chicago-Area Coal Plant Out of Business
“An 85-year-old coal plant near Chicago is going out of business after new federal air quality rules ultimately made the facility too costly to be worth operating.”
396 David B. Benson: I’m getting bored with electric power talk too.
The good news above shows the value of Obama’s approach to GW. It is far too slow, but the Chamber of Commerce is still insisting on talking about growth. At least 2 farmers here in Illinois recognize that something is wrong with the climate. We have a very difficult idea to sell until the “Pearl Harbor” event happens. Until then, we have to keep talking to remember how. I went to a county board of supervisors meeting today. Just listening showed me how far most people are from climate action. I also heard the following: “The [billionaires] think they are going to escape to another habitable planet when NASA finds one.” As with electric power talk, we have to try to keep fantasy in check.
21 Jun 2011 at 10:50 PM
Re 395 Brian Dodge – thanks.