Saturday, April 04, 2009

Recycle

One of the things missing in the debate about coal is that the energy used is less than half of the energy produced. In the case of electrical generation, the electrical energy produced is only a third. Thomas Casten and Philip Schewe write in the American Scientist that up to three wedges may be available (ok, that is the outer limit) with current technology by paying attention to rejected heat. They write that

The power industry is peculiar. What other business throws away two-thirds of its input? In what other industrial field has energy efficiency been flat since the Eisenhower administration? Indeed, in terms of total energy usage, Thomas Edison‘s early power plants in the late 1800s converted more of the input energy to useful work than any of today’s electric-only power plants. How can that be? Surely modern electrical generators are better than those used a century ago. Yes, they are, but that isn’t the economic point.

Edison used the castoff heat from his generators to warm nearby homes and factories. Consolidated Edison, the descendant company of the one he founded, still delivers heat to thousands of Manhattan buildings via the largest commercial steam system in the world. But few modern fossil- fueled power plants bother to use their heat. They instead vent it into the air. Why throw this valuable thermal energy away? Why burn money? The reasons for this lie in the evolution of the power business, but basically it comes down to one logistical factor: As the years went by, larger plants required more real estate and were built farther from the customer. After all, who wants a sooty coal plant next door? Electricity easily travels many miles, so power plants could be built hundreds of miles away, where they could tap the energy of a river, or where local coal was especially cheap.

Today, emissions from modern coal burning plants are much lower, and can be made lower still. Indeed, instead of beating on China not to build coal burning plants, everyone should be beating on China to build modern coal burning plants and close down the old soot belching ones, eliminating a large portion of the black carbon problem. Using waste heat in South (e.g. India/Pakistan) and Southeast Asia for cooking could make another contribution. Even using the waste heat to process the dung used today for cooking would be a relative winner.

Casten and Schewe think there is a minimum of one wedge and the possibility of two or three to be gotten from using waste heat. The magnitude of what can be gotten is that waste heat use in Denmark accounts for about 50% of the energy used, in the US, 8%. The US uses a lot more energy.

Its not only large power plants that can use waste heat. There are small units that produce heat and electricity to power and warm a house. It's not just coal, natural gas in pipelines runs at much higher pressures than used in homes. The expansion could be used to power turbines. Many industrial process produce heat which can be used to produce electricity or for heating, and increasingly they are purchasing heat from power plants. Dow Chemical was an early adopter of these strategies.

Optimizing energy recycling requires planning and a favorable regulatory environment. It is worth doing. (The paper is behind a paywall, but available to all Sigma Xi members, e.g. the smart bunnies=:>)

Comments?

21 comments:

Anonymous said...

Naturgal gas expansion has been around for quite some time. (This is a .tif file of a 1992 newspaper cutting, hope you are able to view it.) However, even though I'm also for the every little bit helps approach, I don't think it's a large amount of power. This example is 4MW, and although Amsterdam Utility Company doesn't seem to exist anymore, then at a guess they would probably have provided gas for up to half a million people.

Natural gas is used much more in a industrial setting than domestically. Not sure if Norway is a good example, but energy sector vs. domestic use is about 18:1. So, could a more appropriate question be, are expansion turbines being used in industrial settings, where we are talking about far more energy that could be saved, possibly at increased efficiency? For, electricity generation from natural gas, the answer is a definate yes. After all, their prime business is producing as much electric power as possible from available fuel.

Seems to me that NG expansion for domestic use is a very small niche market and so is a very slim wedge. That's not to say it's not being considered seriously. Although, you need an unconventional gas distribution company to think about producing electricity. They need more incentive, like a carbon tax.

That 4MW turbine was also combined with a 2.7MW cogeneration plant to provide heat for the cooling gas as it expands. This would seem to indicate that it becomes feasible in a cogeneration settings, which might be more appropriate for Europe than the USA.

It's probably also an issue that people don't tend to use a constant amount of NG domestically throughout the day.

On another issue: I didn't really understand why the authors made a difference between say classic heat recovery and the wedges after 1980; combined cycles, combined heat and power and industrial waste heat recovery. On this level they are surely the same.

Also, when I look at this graph then I think: OK beat on Chine to make modern coal-fired power plants, but the US and Europe should be phasing out the old-style plants too, replacing them with new technology. Not because of the emissions (not talking CO2 here) which are much less in the US due to legislation, but because the plants are old technology and just not as efficient as new plants could be. For example, I've heard many times that Europe could easily reached it's Kyoto targets by replacing all old coal-fired plants with new ones. Of course this can't happen overnight - power plant are built for 40 years plus. There is a lot of CapEx involved.

A possible bigger problem in China is that there has been a tendency to turn off cleaning technologies that are already installed to increase power production.

Anonymous said...

Comment above is from Bocco.

Barton Paul Levenson said...

I would like to see no new coal plants at all built. Carbon dioxide.

Arthur said...

I have a lot of doubts about heat recovery being a significant efficiency boost for several reasons. Almost all of the low efficiency of steam power plants now comes from the Carnot limit defined by the ratio between the high- and low- temperature ranges of the system. Heat recovery proposed to generate extra useful work out of the low-temperature end of the process, the "output" steam, say. But you could just as easily get extra useful work by shooting for a lower output temperature in the first place.

Yes, there is a demand for low-temperature heat which is often supplied very inefficiently by burning fossil fuels. But given the inability to store or transport low-temperature heat over long times or distances, the mismatch between electric generation demand and heating demand almost always makes heat recovery of this sort not a useful exercise.

Better to spend money on improving residential insulation so less low-temperature heat is needed, and on improved efficiency or renewables to replace electric generation.

Anonymous said...

Interesting article related to this

http://www.energymanagertraining.com/PowerPlantComponent/Output1.1/21.pdf

Anonymous said...

Better to spend money on improving residential insulation so less low-temperature heat is needed,"

To say nothing of improving "end use efficiency" (of devices that USE the electricity) -- since there is a multiplier effect involved in transmission and other electrical delivery losses.

Focus on (largely centralized) power generation really misses the point. If we had a less decentralized power grid with all that entails, the system would not only be more efficient, but it would be more robust.

reducing carbon emissions is really going to take a revamping of our entire energy infrastructure, not a simple "fine tuning" the current system.

daunting? yes.

Impossible? No.

Anonymous said...

Anonymous 5:47 AM

A new combined cycle gas turbine power plant will get you 58% efficiency methane to electricity, with the prospect of getting up to 60% in the near future. If built close enough to some low end heat sinks (high density housing estates, a few industrial applications, etc..) then maybe the overall efficiency goes up.

So let's decentralize, and take a really efficient nominal 5kW generator running on natural gas (see table 1, page 11). Depending on the outside temperature (not considering 42°C) we can get between 35.1-42.4% electrical efficiency, and an electricity vs. heat production between 0.92-1.49. The overall efficiency comes out at a whopping 68.2-74.2%. Wow. But is it practical? No way. Now electricity and heat are no longer decoupled as in a most houses. What about the times you need electricity but no heat and vice versa. The last is also true for large scale CHP, but at that scale there are more options. The power draw in my house is rarely above 2kW. On my central heating boiler I can read: nominal 26.7 kW, although I don't know if this refers to input or output or some more esoteric description. In any case that's nowhere near a 1:1 electricity:heat ratio.

According to this wikipedia entry, losses from transmission average around 7.3% for US and UK. Which brings our combined cyle down to 53.7%. Still better than the system at home.

Say in Utopiaville that we have heat-electricity generation that perfectly matches our needs with a 70% efficiency. Let's follow the link given above at 5:40 AM. In 2004, across Europe, this value was already 47.8% (page 3, 1st paragraph). If Utopiaville was in Sweden then the battle for you decentrailized story is already lost (page 2, fig 1b) at 80%+ (although it's decreasing). Hmmm.. could there be a link between cold climates, using CHP and improved insulation?

Now how in both scenarios, how are we going to reduce CO2 output by 80% by 2050. (Let's ignore Fig 2, page 2, date 2030, which predicts CHP efficiency across Europe at that time of 65%+, mainly because I don't believe it will happen). Decentralized capture, even though in Utopiaville you would have to capture less - forget it. I suppose you want the cost of electricity to be cheaper too?

Bocco.

Anonymous said...

Arthur,

I think you are right that you should spend money where the biggest improvements can be made. Obama's weatherization sounds like an extremely small good start; petty Alaska wont be cashing in on that. Although I can't imagine that someone who lived in Alaska would have a house that wasn't already pretty much well-insulated? Or are there parts of Alaksa with similar climates to Los Angeles?

BPL,

I would also prefer no coal, but it isn't going to happen. What might happen is that we persuade everyone that if they use coal, they also have to use capture technologies as well, such that the additional effect on the atmosphere is minimized. What would we do when Nepal says "yes very nice, but we're going to use coal anyway," and to the sea "bring it on!"

All of this doesn't mean I don't think renewables have a place, but it is never going to be the whole solution until all the carbon that can be burnt is burnt!

Bocco.

EliRabett said...

On the way to an 80% reduction you have to pass 10, 20, etc. Efficiency and use of waste heat are relatively low lying fruit. Using the waste heat and more efficient plants to eliminate the brown cloud looks to Eli like a good thing, sort of like 1066.

sidd said...

what about painting roofs while/mandating use of light colored roofs ?

sidd

EliRabett said...

Raise the price of carbon, and willy nilly the roofs turn white (pretty much all of them around here), which is why Eli prefers a carbon tax to cap and trade.

Anonymous said...

Bocco:
"I suppose you want the cost of electricity to be cheaper too?"

Do you actually think that comment makes you look intelligent?

Anonymous said...

Bocco,

You might have included this link:

http://www.adn.com/akhouse/story/747625.html

of April 4th that more accurately reflects current reality, but it doesn’t snark as well.

To deviate from The Bunny’s subject, but closer to the theme, I’d be interested in any thoughts on something. Though Herr Hare’s topic is waste heat, I’ve been intrigued by this use of a bit less energetic atoms then our rabett focused on.

http://www.technologyreview.com/Energy/17524/page1/

http://www.ase.org/uploaded_files/dinner_nominations/Andromeda/Chena%20Hot%20Springs%20Resort%20-%20Andromeda.pdf

This seems to be a possible answer for the problems put forth when alternatives to coal combustion are voiced. I’m particularly impressed by the use of “off the shelf” technology, modularity, and the hugely increased area of the planet where it could be economically utilized, if there are no deal breaking obstacles. If nothing else, lower temperature hot rock would likely reduce the number of petro geologists signing various harrumphings.

WhiteBeard

miggs said...

I love this post, but I'm biased: I'm associated with Recycled Energy Development, the company that Tom Casten chairs. Regarding Arthur's comment, the fact is that the worst plant that Casten (and his son Sean, who's the company's president) have ever done is about 70% efficient -- so about twice as efficient as the electric grid. In really exceptional cases they get up to 90% efficiency. Usually we're talking about 80%.

And then for waste heat recovery, which can be done at manufacturing facilities without installing a new CHP plant, it's pure gain: no incremental greenhouse gas emissions, costs drop, no downside.

Anonymous said...

Anonymous:
"Do you actually think that comment makes you look intelligent?"

Is that the best you can do? What about making the case that being super efficient doesn't necessarily mean that prices go up? Above we learned that Sweden is already pretty well integrated in its heat and electricity sector. Look here, second table; the price of electricity in Sweden was only €5.93 per 100kWh excl. sales tax for industrial users of the 2GWh/yr type. Compare this to the UK price of €8.22. Even though this is apples and oranges, if you'd said this, then you would have given me food for thought.

Bocco.

Anonymous said...

White beard:

Thanks for the update. I googled for "Palin Obama Alaska Weatherization", no wonder I didn't find your story, which doesn't have the efficiency angle I was looking for. I didn't think the first story was paticularly snarky, and the 2nd later story makes me think - Oh, it was political grandstanding. Still the context is now much clearer.

As to using an organic rankine cycle then this would seem to be a good idea. Especially in remote locations, and especially if that 5 US cent/kWh is achievable. However, there must be an angle here between remoteless and what people are prepared to pay. This is rather incendiary, but this accident at a biomass plant in Sittard, NL, became much more spectacular because of the use of an organic rankine cycle. Fortunately, geothermal plants don't need combustion sources.

Eli,

You are absolutely right, if we don't touch low lying fruit, what's the point of being able to climb in the canopy? I don't mean to be dismissive of some of these great ideas. Efficiency everywhere must be part of the strategy. I do think that there is a lot of fruit rotting on the ground (sheet number 6).

Miggs:

Great stuff, it a shame that RED has so many requirements for particpation (see RED's business strategy). Still, nice that there are companies out there that can explain to industry how they can use energy more efficiently. No doubt, as carbon becomes more expensive to us, more of these companies will appear, because companies in any business will require reduced footprint. If fuel represents only 5% of your end price then not much chance that you are thinking about saving energy. There are probably bigger fish to fry in your process.

Arthur said...

miggs, those efficiency claims are pretty bogus - yes I know even DOE puts out numbers like that, but they're essentially meaningless because they ignore the difference in *quality* between electric energy and heat energy.

By the same accounting rules, I can attach a solar panel to my roof, run a geothermal heat pump, and get something like 400% or 500% energy efficiency out of it to heat my house. So 70% or 80% when you're talking about low-quality energy like heat (at least relatively low-temperature heat) is actually on the low end.

I know berating the low efficiency of steam electric generators is a favorite bugaboo, but it's close to pointless because that efficiency is limited by the laws of thermodynamics. The only way to actually make generators more efficient is to either go to higher temperatures (as some advanced nuclear ideas do) or to avoid the steam part and use the exhaust gas stream directly (as some gas generators do).

Look at the graph Eli posted - does it occur to anyone that perhaps the *reason* electric generating efficiency improved from 1900 to 1960 was related to the reduction in "recovered energy" use? Make the plant work as efficiently as possible at the one thing it is supposed to do, and then if you can do something else useful with it, fine. But don't sacrifice the efficiency of an electric generator for the dubious efficiency accounting in that graph and related claims.

Anonymous said...

Here's another possibility for the stalling out of efficiency improvements in the range still theoretically possible. Most power is generated by companies which are government regulated monopolies. They usually operate with a fixed (maximum) profit margin, which effectively becomes a guaranteed minimum profit. It doesn't matter that engineers may be continuously cooking up interesting techie improvements - the risk/reward ratio is already at zero! I imagine that power company administrators instead have been trying to divine and react to unpredictable energy legislation. It's smarter to implement mandated innovations than to drown in an ocean of paperwork implementing unproven , un-mandated ones.

dpBosch

Anonymous said...

I am german and I can promise you that Georg Hoffmann has nothing to say to the Gerlich @ Tscheuschner paper. He doesn't talk to Mr Kramm at all and is insulting everybody who doesn't believe in realclimatism.

Who are you to criticise Mr Kramm?

What is this joke all about? If there were a scientific debate, why is Mr Hoffmann so silent?

hapa said...

what works works, what doesn't doesn't. 2030 will end up the target for the rich world. to me, in that scenario, the role of high efficiency fossil-burning will be for irreplaceable process heat; backup and peaker power; and difficult space heat. things like sink loss and air travel will really squeeze the industries where mitigation is possible.

if stubborn applications can be rigged to cut emissions deep before more permanent answers can be found, that's helpful. if we can use supply-side conservation to shut down xx% of whatever coal-fired plants are left after our first big installs of demand-side conservation and no-carbon supply, that's great. but me, big idiot, personally, i don't think either of those are large or permanent wedges.

Anonymous said...

I think the electric power industry is in for some big changes in the coming years. The article is right in that while technological advances have happened, there haven't been any huge changes. That being said, we need to make sure that energy we use is the best one from an energy-return-on-energy-invested point of view: I was reading a study that said that while some forms of energy work well for this, others really don't. Shouldn't we be paying more attention to what is efficient over the long run too?

The study I mentioned is posted here:
http://inderscience.metapress.com/app/home/contribution.asp?referrer=parent&backto=issue,6,6;journal,2,6;linkingpublicationresults,1:119992,1

With another similar conference paper here:
http://me.queensu.ca/people/pearce/publications/documents/asp3.pdf


-DrClaw