Most Efficient Method of Power Generation?

"A CHP system's efficiency depends on the technology used to generate the electricity and thermal energy, the system design, and how much of the thermal energy is used by the site. Therefore, every CHP system will have a different, site-specific efficiency once installed. However, the six most commonly installed CHP prime movers tend to offer fairly standard ranges of achievable efficiency as follows:

• Steam Turbine: 80 percent
• Diesel Engine: 70-80 percent
• Natural Gas Engine: 70-80 percent
• Gas Turbine: 70-75 percent
• Microturbine: 65-75 percent
• Fuel Cell: 65-80 percent

http://www.epa.gov/chp/basic/efficiency.html
Catalog of CHP technologies...
Calculating total system efficiency....

Note that this graph is from a pro nuke site. So, to balance it, consider the findings of the Ontario Clean Air Alliance (which actually show sources to back up their numbers).

Solar energy from PV has fallen dramatically in recent years, and is not likely as high as indicated in this graph... Search out "solar parity" or "grid parity" for ample info on the cost of solar.

Note also -these costs are all only direct costs, not indirect costs, which the fossil fuel and nuke industries love. Private profit at public expense (the public expense being health care, energy subsidies, clean up and decommissioning costs etc)

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It's kind of hard to say. It really depends on your definition of "efficient". Each of the methods listed are all plausible, but they have their own set of hurdles that need to be overcome in order to be implemented in an area.

The Energy & Environment Exchange has done quite a few blogs that look into various forms of alternative energy. You might want to consider perusing them, and maybe some of the older threads on CR4 for some more information

What form of efficiency? Cost per kilowatt? Over what period?

CHP infers a cogeneration plant, the only difference is that the plant is built near the fuel source; the fuel is some form of process by-product from a factory, walnut shells for example; and some of the waste heat is used to heat the factory that produced the fuel. These fuels are limited so this kind of cogen must be in a small niche. There are some that are built near a source of fuel that is too low grade for the normal plant.

The cogens caught on because the government wrote a requirement for the utilities to buy the electricity, into law; that is what made them efficient, money-wise, for the developer, only 2% need be produced as steam.

This is a propagandist or salesman's question. The individual setting the efficiency calculation criteria can easily make virtually any form of power generation seem to be the most efficient.

For instance:

The most efficient use of money in building any power generation facility will likely be the building of one of the fossil fuel forms of power production. However, this initial cost expenditure for the plant itself does not include the cost of the fuel to be burned, transporting this fuel to the plant, nor any enviromental impact from burning this fuel. In contrast solar power generation requires no future fuel usage. However, peak solar power generation is not controllable. This means that very often solar power must be stored in some fashion to allow for times of low to zero solar power production. Every storage and release of power loses power.

I could go on about the advantages and drawbacks of thermal, nuclear, animal, bio-fuel and other forms of power generation, but I believe I made my point.

Thanks for the answers,

Yes, from the point of cost as well as efficiency, its hard to compare. but my question here is just efficiency not the cost...

efficiency in sense of input vs output...

and solareagle,it is very informative and thanks :)

The criteria that you established, being focused on efficiency without cost, contains a contradiction that I find very difficult to reconcile. Using your criteria, though, I will venture that a window that is open, and used to illuminate the interior of a building, is 100 % efficient at transmitting all of the light energy that enters it's frame into the interior of the building.

If you are looking at electricity generation, efficiency calculations require you to look at yield, which involves the recognition of cost, generally derived from the price of plant construction, material, maintenance, fuel, and environmental remediation over lifetime production value. There are many other variables, and as an earlier poster noted, it's pretty easy to make the numbers say anything you want them to say. The impact of fuel acquisition and development, and long term cost (including remediation of environmental impact) for these systems is the most widely abused statistic

Finally, the environment surrounding the production has a great impact on efficiency. If the energy is consumed upon production, the usefulness of that production is much greater than any stored or transmitted energy, hence it could easily (and correctly) be portrayed as being more efficient. CHP has this attribute, and in the right environment, is an ideal solution, but requires both very low cost fuel and consistent local demand for heat and electricity. It's impact on water resources, air quality and waste stream may effectively lower the yield to levels far below the chart indicated level. Great question though, making me want to continue the conversation

Any system with maximum output with minimum input combined with CHP is a better choice.

Hydro electric is by far the most efficient!

Xanasax

Overall, some fairly decent comments. If the idea is output vs. input, yes- CHP is pretty good but nowhere close to big hydro.

The key relative to CHP is that the system MUST have a constant need for the thermal output of the system. Since nearly every industrial plant and food processing site meet that need, there are a LOT of easy applications. Several other sites can also use it if the thermal is used to make cooling when needed and heat when not.

However- PFR's comments regarding concern over "impact on water resources, air quality and waste stream" are totally incorrect. Compared to any other thermal power generation system, water usage is reduced because "waste heat" is not thrown away in a cooling tower but is used to replace "new thermal" input. The same issue is in place for air quality- especially if natural gas or other "good" fuel is used- the amount of CO2 and NOx released when CoGen systems operate is MUCH lower than if all of the "normal" systems function for the same results. Finally, compared to the fly ash and coal slag left after any coal-fired generating system operates, the virtual zero waste products of most CHP systems is a no-brainer.

By the way, the 75% efficiency in the earlier posting for CHP is not quite correct. Most current CHP systems operate at 65-70% efficiency. Last year, Kent State University got an award because THEIR CoGen plant was operating at 71%. On top of that- a totally new CHP design has been developed has been observed to operate at 97% annual efficiency- documented by the prototype site. Last summer, 105F entering air became 84F exhaust. When this system operates, its thermal efficiency is higher than virtually all steam plants (70% vs. 55-60%) so the electricity is FREE. It cuts CO2 by over 80%- 6900 metric tons per MW annually (300,000 trees) and NOx by 95% (13 metric tons a year per MW) while making over 5,000,000 liters of near-potable water annually per MW.

Hi energygod, I used to live in Norway, and it must be one of the only countries that gets all it's energy needs from hydro-electric, even small villages have their own small hydro schemes, and the price of electricity over there is less than half of what it is in the UK!

Xanasax

counter point

if you burn NG, coal or walnut shells as the base fuel in a CHP app, you are still creating significant CO 2, other pollutants, and most likely, a waste stream that has to be disposed of. You still have to source fuel, and that activity is frequently (even NG) very destructive and toxic to life. The by products of combustion are still there, in smaller quantities. It's not a question of whether CHP can be more effective and efficient in production than traditional plants; it is. The problems associated with gathering and combusting the fuel are the same, with the associated costs and lower, but very significant environmental impact. No one is debating that it can be a lower emission energy production cycle per unit of fuel consumed. But it is still easy (like you just did) to imply that it does not have significant environmental impact.

At no time did I state that the system has NO environmental impact. What I said is that the OVERALL environmental impact is substantially lower than would have occurred if "traditional" methods of producing electricity and creating thermal output were used.

The key benefit of CoGeneration is the ability to replace new-energy thermal input with the heat remaining after electricity has been generated. The second benefit is to generate electricity with a fuel source that produces less CO2 and NOx.

The system that I described just does each of those things BETTER than any other similar system out there. BUT- as you appropriately stated, it still produces SOME environmental releases.

That said- ANY OTHER electrical generating system that does not create SOME level of environmental release has NO way to directly generate thermal output. At best, you can turn SOME of the electricity produced into heat, but then you will need A LOT more generation capacity and mounting space- and a whole lot of batteries if you want to make thermal energy 24/7.

actually, you wrote,

However- PFR's comments regarding concern over "impact on water resources, air quality and waste stream" are totally incorrect.

Yes I did, and I stand by that statement because you noted that those items' impact could LOWER (emphasis added) the yields to levels far below the chart's indicated levels.

My statement was that there was each of those issues would typically be LOWER for CHP than for any other thermally-based generation system, which- if taken into effect would produce an INCREASE in relative efficiency from the chart (if the chart had been weighted based on overall environmental impact and not just generating effectiveness).

Neither chart posted was not a consideration of environmental value of power generation, only on cost of producing power or of the systems.

My earlier post also only took issue with your statement regarding "discharges" from CHP systems. I did not comment on your statement that CHP was only effective if cheap enough fuel was available. As I stated in my comments, CHP systems are available that operate THERMALLY at a lower cost than other (boiler) thermal systems that they usually replace- in full or in part- so the cost to the thermal input becomes irrelevant. They have a higher value whatever that cost of the fuel that is used on solely THERMAL basis, plus all of the electricity that is produced is FREE.

When applied, these systems cut environmental impact significantly (not TOTALLY) and they cut operating costs significantly as well with paybacks that are low enough (about 2 years) to make them a good economic investment as well as a good environmental investment.

Hi energygod, Hydro electric schemes have a big impact on their surrounding nature, first the water table nearby will rise significantly, also the nature round about the resaviour will change dramatically, so hydro electric also has an effect on nature!

Xanasax

You are totally correct, although- most of the time those impacts are generally positive because the higher water table means easier access to drinking water plus the increased vegetation usually occurs where there generally was almost none before.

Most large hydro plants required a dam and a huge lake filling up areas that were for the most part relatively barren or only sparse vegetation near a river in the valley of large, rocky mountainous areas. Those areas are now actively operated vacation spots with significant boating and fishing operations.

please tell me you are being sarcastic.

Hmmm. Knowing that PV solar panels are less than 20% efficient, why not try to capture the lost energy. Would it be possible to use the excess heat 'captured' by a PV solar panel to heat a house? In other words, run a water jacket behind the PV panels that will serve to cool them as well as capture usable heat...

...a sort of solar CHP?

That is a good thought, and likely possible. I am not deeply knowledgeable of the "inner workings" of PV systems to know if a WET back would have any negative impact on their operation but I am sure that SOMETHING could be done to make it work.

Sounds like a mission for someone's efforts. Maybe yours?

People have begun to combine PV and solar thermal. The result is that the PV efficiency can be boosted due to lower temperatures on the panel, plus hot water.

the only plausible reason to do that is to save space. Contrary to what you might think, the thermal portion actually increases the operating temperature of the PV cell, decreasing efficiency. It will work, but there is very little reason to do it. It is also putting a lot of parts and pieces in one complicated box box., where they are forced to compromise. The systems work much more effectively as components.

Think home stereo vs. boom box.

Porsche 911 versus Panamera

Grocery store vs convenience store.

African Savanna vs Zoo

PFR - do you have some data on this because I would be interested to see it...

the sun.

I started a separate thread on something new that justified it's own thread:

http://cr4.globalspec.com/thread/78817/Freeing-Energy-From-The-Grid-and-more

http://cr4.globalspec.com/thread/78817/Freeing-Energy-From-The-Grid-and-more