Fiddler's Ferry and other power stations are shutting down

[Little John]

Yes, obviously only proportion of the shipping industry specifically related to Drax!

I'm not following the disagreement here. It doesn't matter how the carbon is counted, just that it's only counted once. Perfectly fine to tot up all the carbon associated with harvesting, processing, shipping wood to Drax and dividing that by the MWh output for a carbon intensity of generation. Alternatively, you can tot up the carbon and allocate it to the forestry industry, shipping industry etc.

What's not okay is to do both, ascribed a large carbon emission to the shipping industry, and then double count the same carbon on the MWh output.

Firstly, nobody has said it is okay to count it twice.

Secondly, when calculating the total carbon footprint of burning wood at Drax it is not "perfectly fine" as an alternative, as you have suggested, to allocate it to the industries that supply Drax as opposed to Drax itself. That is mis-counting. in terms of that calculation.

Sure enough, if your focus of investigation is the forestry industry and you have no investigative interest in the industries further along the supply chain, then for that analysis, the counting would validly come to a stop at that industry.

Indeed, if one really wanted to be belt and braces about such an analysis, one would need to include all of the carbon involved in transporting workers to and from work for all of the industries in the Drax supply chain. Or, at least a portion of their transportation costs as a function of the portion of their work that represented a part of Drax's supply chain.

In other words, in principle, all carbon consumed as part of the process of getting that wood to Drax should be included in any carbon count for that wood. Or, indeed, as part of any EROEI analysis for any end-product or service.

[kenneal - lagger]

I think that the answer to Drax is that we need to keep a carbon account with each industry accounting for its carbon costs and then have another measure, say carbon intensity, which gives a measure of the carbon used in each type of energy generation. Thus Drax would take account of the long supply lines while nuclear would take account of the concrete used in construction of the power station and the concrete and energy used in fuel processing and decommissioning and safe long term storage. Now that would be enlightening.

[Little John]

I would go further and say it is imperative. In it's absence, no valid comparison between products and services can be made.

[clv101]

Firstly, nobody has said it is okay to count it twice.

My reply was to woodburner's comment about the emissions associated with the wood being forgotten about. My point was that they aren't forgotten about just counted somewhere else.

Secondly, when calculating the total carbon footprint of burning wood at Drax it is not "perfectly fine" as an alternative, as you have suggested, to allocate it to the industries that supply Drax as opposed to Drax itself. That is mis-counting. in terms of that calculation.

Sure enough, if your focus of investigation is the forestry industry and you have no investigative interest in the industries further along the supply chain, then for that analysis, the counting would validly come to a stop at that industry.

Indeed, if one really wanted to be belt and braces about such an analysis, one would need to include all of the carbon involved in transporting workers to and from work for all of the industries in the Drax supply chain. Or, at least a portion of their transportation costs as a function of the portion of their work that represented a part of Drax's supply chain.

In other words, in principle, all carbon consumed as part of the process of getting that wood to Drax should be included in any carbon count for that wood. Or, indeed, as part of any EROEI analysis for any end-product or service.

There are many different ways to calculate CO2 emissions. It doesn't really matter where you draw the boundaries - as long as you draw then consistently. I understand why you think the carbon footprint of burning wood at Drax calculation should including the shipping, processing, forestry etc. However, if you do that for Drax's electrical output - how do you compare it to another powerstation, burning gas, or coal? Their published CO2 figures *do not* include all the upstream emissions. So you are left comparing apples with oranges.

If you do allocate all the upstream emissions to Drax's wood burning, then subsequently want to calculate the emissions from the Atlantic shipping industry you are left with the task of unpicking which ships have already had the emissions counted - or else you end up with two numbers, shipping emissions and electricity generation emissions, which contain elements of double counting. This is a big issue in the carbon emission world and hence why folk try and adopt common boundaries to make datasets comparable.

[Little John]

Two wrongs do not make a right. Did I really need to tell you that?

[vtsnowedin]

Well of course what is sauce for the goose is sauce for the gander. So when considering the question of which of two options produce the least amount of carbon emissions all up stream and operating emissions for both options need to be measured and accounted for.
I very much doubt that shipping wood chips in bunker fueled cargo vessels from North America to the UK to burn to replace coal in a electric power plant saves much carbon emissions unless the coal is being imported from Australia and shipped by a very dirty coal hauler.
You would have to add it all up to know, from the chain saw that cuts the trees down (or shear in modern harvesting operations) then the skidder, the chipper, the trucks that take it to port , the crane or conveyor that loads the ship, the ship, then the tugs in and out of harbor, then unloading in the UK and perhaps more trucks between port and plant, then the plant and it's machinery from stockpile to boiler then ash disposal and anything I have forgot.
My point is that we need to be doing these calculations and actually choosing the best option based on the facts not just feel good intuition.

[kenneal - lagger]

This is why I suggested that we need a separate measure, Carbon Density or some such, so that it is possible to compare the carbon burned in each form of electricity generation. This would be a separate measure from carbon accounting for the economy as a whole.

[BritDownUnder]

One other thing I would like to know is whether the wood chips are specifically harvested for this purpose of are they a byproduct (maybe even called a waste product) of another process such as thinning trees or the bits of logs that cannot be used for board wood. No doubt this would impact of what the carbon content can be accounted for. No doubt there are also a few creepy-crawlies in the Deep South who are feeling aggrieved that their waste wood that normally ends up on the forest floor is being shipped off to the UK for use as fuel.

[vtsnowedin]

One other thing I would like to know is whether the wood chips are specifically harvested for this purpose of are they a byproduct (maybe even called a waste product) of another process such as thinning trees or the bits of logs that cannot be used for board wood. No doubt this would impact of what the carbon content can be accounted for. No doubt there are also a few creepy-crawlies in the Deep South who are feeling aggrieved that their waste wood that normally ends up on the forest floor is being shipped off to the UK for use as fuel.

Here in New England the practice is to sort trees and parts of them to their highest use. Good saw and veneer logs go one way and smaller logs might go to wood yards for traditional fire wood with the tops and smaller trees fed through the chipper which in most cases now get made into pellets for wood burning stoves. There are a few power plants here that burn chips directly but they are having a hard time competing with Canadian hydro power and solar and wind that the companies have to buy by government mandate.
A neighbor had ten acres clear cut this winter and all three options were used. When the chipper was brought in they had a pile of tree length logs twenty feet high and a hundred yards long. It took days to chip it all.

[kenneal - lagger]

It should be made illegal to burn anything in a power station without using the waste heat. Using that waste heat would boost the efficiency of the process by at least 100% from about 35 to 70% at least.

[clv101]

It should be made illegal to burn anything in a power station without using the waste heat. Using that waste heat would boost the efficiency of the process by at least 100% from about 35 to 70% at least.

I'm somewhat surprised that the old thermal powerstaions from the 1950s, '60s, 70s etc. didn't make use of waste heat. I remember thinking as a child when I first found out what cooling towers were, what an incredible waste it was.

What are the industrial uses for low grade heat? Is there a good reason why they aren't co-located with power stations? I guess covered horticulture could benefit - even take some CO2 as well.

[vtsnowedin]

Using the "waste heat" has always been a consideration and used where the power plant was close enough to a customer to make it economical. Many buildings in New York city used to have steam supplied by Co Ed as a by product of their power stations that were in the city limits. Moving the plants and their pollution away from down town makes that less viable.

[kenneal - lagger]

Some did Chris. Battersea, for instance, heated a housing estate on the other side of the Thames for a number of years until it was decided to change heating supplier when the estate was modernised, I think it was. Slough Heat and Power supplied an industrial estate next door to it for quite a number of years, even when it was using chipped waste wood from local sources, until its closure a few years ago.

[adam2]

Utilising the waste heat from power stations is often proposed, but seldom viable in practice, and is becoming less viable.

A modern well designed steam power station produces a lot of waste heat, hundreds, possibly even thousands of megawatts.
This waste heat is however at a very low temperature, much too low for most heating applications.
It is just about possible to heat a home thus but it requires very large radiators which are hated by the potential occupants.
The huge volumes of barely warm water required large and expensive pipes and also considerable energy expended on pumping all this water.

There are limited industrial uses for low temperature heat, possibilities include heated swimming pools, the growing of crops under glass, low temperature evaporators for desalinating sea water, and the drying of grain.

The power station will still need cooling towers for summer operation.
The heating load will still need alternative heating equipment in case the power station breaks or is not needed when there is heating demand.
It is possible to alter the design of the power plant to reject heat at a higher and more useful temperature, but this carries a substantial energy cost and is only viable if there is a substantial and PAYING demand for the heat. It wont work if the heat is expected to be free.

And of course these days we are burning less fossil fuel, so a fuel burning plant may not run at times of ample wind energy.
Also new homes are meant to be more energy efficient and will hopefully only need a couple of KW for heating.

Diesel engines produce waste heat at much higher and potentially very useful temperatures, but tend to see very little use.

[BritDownUnder]

I would add to Adam's excellent post that there are many possibilities of using 'waste' heat. However we need to have a think about the thermodynamic theory first. The Carnot cycle (look it up) says that any process that converts heat into work will be only as efficient as given by a formula that considers the high temperature of the steam and the low temperature that the heat is rejected to - in this case your cooling tower or your industrial or domestic use of steam.

Moving onto steam turbine theory you need to change your working fluid from water to steam to get the energy out of it - called the Rankine cycle (again look it up) and then back again to water in your cooling tower or waste heat users.

Going on to steam turbines - basically you have two types - back pressure and condensing. With condensing you will use a cooling tower and lose all your waste heat. The steam goes into the turbine around 500 C and after doing work comes out of it at about 120 C is condensed back to water as soon as it passes out of the turbine and this happens at a low temperature and uses generates a lot of lukewarm water. The steam changing from gas to liquid phase also creates a vacuum that helps 'pull' the steam/water through the system.
With back pressure steam turbines you can use the low temperature 120 C steam for other uses once it goes out of the steam turbine but you will need extra pumps and equipment to help this. In my very limited experience it also makes operating the turbines much more complicated and a nightmare to commission. Also you will need to design one or the other systems before construction and it may be very difficult to change after construction.

Let's take some real world examples. The recently demolished High Marnham Power station where my father worked for many years was about 1000MWe (MegaWatts of electrical energy output) but probably produced about 3000MWt (Megawatts of thermal energy). I would bet that it used a condensing steam turbine since I remember from childhood that it had five large cooling towers. Hence about two thirds of the energy was lost making all those clouds and boiling water.
If it had been designed differently then it could have had a back pressure turbine and maybe generated 800MWe and had 2200MWt available for heating greenhouses and domestic hot water. However High Marnham is a small isolated village and there would have been little scope to sell all this waste heat.

I also worked at a gas turbine combined cycle project in China. This used a gas turbine to generate electricity using about 30% of the total available thermal energy. The thermal energy was extracted from the output of the gas turbine was fed through a boiler and about 15% of the total thermal energy was used in a steam turbine to generate more electricity. So far this power plant was 45% efficient. After the steam at 120 C temperature was used it was then sold to an industrial use. Then hot water at 90 C was used in a brewery. Then hot water at 40 C was used to heat the offices.

So if anyone is still reading - you can, and probably should, use the heat output from power stations for some useful thermal purpose. However this use would probably be confined to new, specifically designed power plants located in or very close to cities or suitable industrial users. They would probably be have to be designed a lot smaller than 1000MWe output and be specifically designed for the purpose.

A much better idea may be to store the excess energy from renewables - mainly wind in the UK - in the form of centrally located thermal stores that could then distribute the heat on a town or suburb scale.