Deep Mine Shaft Required
- Thread starter Mark
- Start date
SamT
Moderator
No not really - the total amount of potential energy is dictated by 2 things, the mass of the weight, the length of the drop.
Then you have to take away all the losses due to friction, efficiency of generators etc. Adding more gearing/pulleys just increases the proportion of losses due to friction, and doesn't increase the amount of energy you can harvest.
The principle is the same as that used by Dinorwig pumped hydro scheme (and other such pumped storage schemes).
Dinorwig was traditionally used for 'peak lopping' i.e. it kicked in at 7pm or when ever it was that coronation street finished and everyone stuck the kettle on. It used to be the exact point of peak demand on the grid to the extent that they used to have a telly in the control room so they could see the exact point at which the credits rolled on the program so they could push the button.
I suspect the peak demand profile on the grid is changing as peoples viewing habits have changed radically over the last decade with 'on demand' viewing. Perhaps far less predictable, but then perhaps far less 'peaks and troughs'
Then you have to take away all the losses due to friction, efficiency of generators etc. Adding more gearing/pulleys just increases the proportion of losses due to friction, and doesn't increase the amount of energy you can harvest.
The principle is the same as that used by Dinorwig pumped hydro scheme (and other such pumped storage schemes).
Dinorwig was traditionally used for 'peak lopping' i.e. it kicked in at 7pm or when ever it was that coronation street finished and everyone stuck the kettle on. It used to be the exact point of peak demand on the grid to the extent that they used to have a telly in the control room so they could see the exact point at which the credits rolled on the program so they could push the button.
I suspect the peak demand profile on the grid is changing as peoples viewing habits have changed radically over the last decade with 'on demand' viewing. Perhaps far less predictable, but then perhaps far less 'peaks and troughs'
Boy Engineer
Active member
Judging by some of the barrel-scraping stuff on the box recently, I imagine it?s more a question of reducing supply as folk reach for the off button. I?m not sure if it is an ageing thing, but there do seem to be a lot of morons unable to put up shelves/do their own garden/avoid cheating on a partner/cook the most basic dish etc. Ironic that at a time when they have more information in the palm of their hand than ever before, the big screen seems to celebrate incompetence and ignorance.
Anyway, must go now as nurse says it?s tablet time.
cavemanmike
Well-known member
Moron shags moron =super moron 
Back to the topic:
By my reckoning (anyone ? feel free to check/query it), if you drop a mass of 2000 tonnes down a hole 250 m deep you generate 5 billion joules; if you lowered it down gently over the course of one day, it would generate 57,870 joules/sec, AKA watts. Apparently, the average house in the UK uses on average 429 watts (averaged over the course of one day), so the hole/weight contraption could power ~135 houses (if it was pulled up and let down once a day).
Is that a reasonable, viable output for the effort involved?
By my reckoning (anyone ? feel free to check/query it), if you drop a mass of 2000 tonnes down a hole 250 m deep you generate 5 billion joules; if you lowered it down gently over the course of one day, it would generate 57,870 joules/sec, AKA watts. Apparently, the average house in the UK uses on average 429 watts (averaged over the course of one day), so the hole/weight contraption could power ~135 houses (if it was pulled up and let down once a day).
Is that a reasonable, viable output for the effort involved?
SamT
Moderator
Careful with your units and figures there Fulk.
a household cannot 'use' 429 watts, in the same way a car does not consume 40 miles/per gallon. They are rates of use, and the total consumption depends on how long that rate is maintained.
I get your gist though.
The point is not to improve generating capacity. The biggest problem we have on the grid at the moment is one of energy storage. The old days of a few nuclear and coal fired power stations (not easy to turn up and down) meeting the base demand, with a few gas powered stations, (easier to modulate) to deal with fluctuations and about 4 pumped storage hydro installations to hit those short lived peaks are now behind us.
We need to find ways of storing the energy when we have excess, and releasing it when we need it, either in times of peak demand, or at times of low wind/solar resource. This is just one option being explored, its relatively low tech, low impact, low maintenance and whilst its never going to be a Dinorwig, if enough smaller locations can be found, it might well provide part of the solution.
Another idea is that once everyone is driving electric cars, at any given moment, you'd have certain percentage of them connected to the grid charging thus creating a huge grid connected battery. 'Smart' metering/chargers could mean that if your car is fully charged, but sat there overnight say (or outside the office during the day), you might be able to 'lend' some electricity back to the grid.
a household cannot 'use' 429 watts, in the same way a car does not consume 40 miles/per gallon. They are rates of use, and the total consumption depends on how long that rate is maintained.
I get your gist though.
The point is not to improve generating capacity. The biggest problem we have on the grid at the moment is one of energy storage. The old days of a few nuclear and coal fired power stations (not easy to turn up and down) meeting the base demand, with a few gas powered stations, (easier to modulate) to deal with fluctuations and about 4 pumped storage hydro installations to hit those short lived peaks are now behind us.
We need to find ways of storing the energy when we have excess, and releasing it when we need it, either in times of peak demand, or at times of low wind/solar resource. This is just one option being explored, its relatively low tech, low impact, low maintenance and whilst its never going to be a Dinorwig, if enough smaller locations can be found, it might well provide part of the solution.
Another idea is that once everyone is driving electric cars, at any given moment, you'd have certain percentage of them connected to the grid charging thus creating a huge grid connected battery. 'Smart' metering/chargers could mean that if your car is fully charged, but sat there overnight say (or outside the office during the day), you might be able to 'lend' some electricity back to the grid.
SamT
Moderator
kWh is a much better unit to use when talking energy use. Joules are all a bit old fashioned and cumbersome and kWh are the unit used by utility companies.
2000kg x 250m x 9.81 (gravity) x 0.7 (efficiency) = 3,433,500 kJ = 953.75 kWh.
Average house use is very hard to establish, but lets say 10kWh a day. = ~95 houses (but that is to supply all their energy for one whole day).
(think I've got my units right :-\)
As I say, the system is not really designed to work in that way, and it bugs me when the media always revert to saying - can power 500 homes etc. (though granted, it does give a very rough idea of magnitudes and orders of scale).
Boy Engineer
Active member
You are. They are talking about a 2000 tonne mass, not 2t. You?ve used 2000kg.
Chocolate fireguard
Active member
You kids don't know you're born!SamT said:
Joules are all a bit old fashioned and cumbersome
Think yourself lucky you never had to use the erg, young man.
Or the slug rod squared/fortnight squared for that matter.
