[peppercorn]

Interesting. Are you thinking of creating ammonia for use as a fuel/energy storage medium, or as a useful product to make when there is excess electrical energy available, and then finding some other source of energy when there is a deficit?

The second. The ammonia produced would be "a useful product to make when there is excess electrical energy available".  There's plenty of it needed for making fertilizers for a start, and the hydrogen needed to industrially produce NH3 comes predominately from natural gas; itself a (fossil!) fuel.   And, in addition, on the occasions when a heavily renewable reliant grid falls short, the option to use natural gas can still be there; whilst the CO2 from said gas is being effectively offset from another sector - ie. agriculture.

I know of a company that pays industrial electro-refineries to up- and down-shift their electricity demand as the grid energy balance fluctuates--they never sell any electricity back to the grid, but because the operation is so energy intensive, and would otherwise be going 24/7, a reduction is consumption is equivalent to increasing the available energy for the grid.

I imagine this company could be an aluminium smelter, for example.
Though clearly it's a little more tricky to turn a large smelter on or off, I suggest that it might be possible to throttle them to a point.
I expect this type of very large demand-side planning would get less practical with a grid heavily reliant on renewables, because of the loss of predictability involved.   However, if we have a future situation where thousands of electric vehicles are plugged in to charge/discharge as needed across the grid then some of the stability (and therefore, predictability) could return.

[alancalverd]

I am unclear, following your logic, how you get a nameplate rating would be 50kW in your example. It could conceivably be 100kW, based on the size of the generator installed.

Indeed it could, but it is up to the manufacturer to specify the plated output, and if he wants to claim a very high capacity factor, all he has to do is declare a very low power rating. Business, not physics. And the business is not making electricity (you get a subsidy for making it when it's needed, and for not making it when it's not needed), but selling windmills and getting subsidies.

And I would question why such a turbine would use a 50% larger generator anyway. Any increasing in size and weight of electrical machinery in a nacelle, a couple of hundred metres in air must also scale up everything else up as well (tower rigidity etc); there will an additional increase in maintenance costs and, off-shore, this is obviously a serious overhead - thus, a generator, say, 10-15% larger than the blade's continuous rating seems somewhat more realistic.

It all depends on the probable peak gust output of the blade before it stalls or shuts down in a gale. Shutdown is not instantaneous so you need a generator that can absorb gusts. Just how big you make it depends on your assessment of gust risk and the cost of repairs.

There's nothing unusual about derating. There is a class of light sport aircraft that is restricted to 80 horsepower, which is fine for cruising but a bit marginal for takeoff, so the manufacturers fit a 120 or 150 HP engine and a throttle detent labelled "takeoff only": this simplifes both licensing and cooling, and the rating plate just says "80 HP continuous".

At one extreme, racing car engines are deemed overweight and undertuned if they survive more than one race (now one weekend, under Formula 1 rules). 500 HP per liter is about right for F1, and 1000 HP/liter would be a target for a dragster. At the other extreme, aero engines using exactly the same physics and chemistry rarely generate more than 50 HP/liter because reliability is essential.  Probably the most extreme examples of derating are in spacecraft and undersea cable repeaters, where maintenance is either impossible or prohibitively expensive, so many systems use "old" technology (components that have been in commercial use for at least 5 years) derated by an order of magnitude.

[nicephotog]

If I read your figures correctly, a 230 kg 2volt deep cycle unit will give you 3000 Ah. That is 6 kWh, so you need 24 of these to supply 20% of one person's energy needs  for 5 days. Add in the controller and connectors, and we are talking about 40 tonnes of battery pack per household. Most believable price today is about $500 per cell, so $50k or so per household for the batteries alone. And then there's the small problem of dealing with 4 tonnes of scrap lead and a few gallons of sulfuric acid every year.

NO not 40 tons(you don't just go throw them away), 2 to 4 tonnes "deep cycle" lead acid (GEL type only half the number "approx" e.g. system voltage(not inverter output power supply) 48v , 96v , 110v , 120v , 240v , 380v , 520v e.t.c. ...), that will last ten years or more (in Britain the climate is much milder and only medium temperature lead acid chemistry accumulators (10 years at 20 deg. Celsius float life-cycle) are needed).
http://windsolarhybridaustralia.x10.mx/#battoff
e.g. 80 of 80ah "deep cycle accumulators" = 1.88 tonne (1880 Kg)

What's more , as i said it will last 10 years at least set up properly(calculated and appliances better acquired for the system).

If I read your figures correctly, a 230 kg 2volt deep cycle unit will give you 3000 Ah

You need to do some research to understand the battery market for that is available, 2v (two volt) 3000ah or 1500ah or 500ah e.t.c. .....
**2v lead acid "acumulators" are really for 12v and 24v storage systems (output whatever you require by obtaining the correct inverters)
**BECAUSE 12v does not allow more than 4 in parallel and not much wiser in 24v!!!!
12v deep cycle 250ah is the most common largest..."made in abundance on offer in the market"...(there are one or two slightly larger).

[Bored chemist]

Can it be done economically? Not with existing technology,

I have news for you. We already do it (though not with the methods you suggested)
Perhaps we  need to hollow out a few more Welsh mountains.
http://en.wikipedia.org/wiki/Dinorwig_Power_Station
Or, if you prefer
http://en.wikipedia.org/wiki/List_of_pumped-storage_hydroelectric_power_stations

[chiralSPO]

I know that we use pumped hydro and compressed air to store energy now, but it is a tiny percentage of the energy consumed, and requires enormous reservoirs. They are some of the most energy efficient methods employed these days, but in terms of space and water required, there must be something better (pumping 10000 m³ of water to a height of 100 m won't even store 3 MWh). Additionally, most of the geographic formations that allow for this are already employed in this way.

We can start hollowing out more mountains or displacing people from river valleys so they can be dammed up, or we can invest in technologies that can store and dispense hundreds of megawatt hours from a building the size of a high school gymnasium...

[teragram]

I'm no mathematician, so please correct me, but:

10,000 cubic meters of water = 10,000,000 Kgs. According to mgh,

(10,000,000kgs x 100mtrs x 9,81) / 3600,000 =2725 MWh.

Still not a huge amount though, but useful.
Re all the comments on batteries, there are I think some grid scale storage installations in progress, but let's not forget those already operating using vanadium redox flow batteries.
Also re: storage, rather than pursue the madness of carbon capture and storage, why not use underground spaces (old coal mine, oil wells, etc.) as air pressure reservoirs (instead of more pumped hydro).
Not great efficiency I understand because of heat losses, but there are projects in Europe and America I think to recover the heat lost in pressurising air to improve the efficiency of the process.
One huge advantage of compressed air energy storage (CAES) compared to carbon capture and storage is that leaks will be harmless.

[alancalverd]

Nicephotog:

http://www.windsolarhybridaustralia.x10.mx

is indeed instructive. It says that 2.3 tonnes of batterries will supply 400 AH at 240V, and I have no argument with that. That amounts to 96 kWh. Now each person in the UK consumes 5 kW, so to supply 4 people for 5 days you need 2400 kWh, i.e. nearly 60 tonnes of batteries.

The problem is that people (well, politicians) talk about domestic electricity consumption, but that is only a tiny part of our energy use. If you wrap up warm and stay indoors, you can manage with 100W for cooking and watching television (but not at the same time), but someone else will have to grow and transport your food, pump your water and waste, and indeed light the TV studio and power the transmitter. And make your next car, television, house.... 

Pumped water storage is a lot of fun. It's very expensive both in land and capital to install, which is why there are only two significant installations in the UK. Dinorwig is the larger one. Its capacity is about 10,000 kWh, so it can supply all the UK's energy needs for about 0.12 seconds, then takes about 6 hours to recharge. Not quite the Hoover Dam, which generates 2,000,000 kW continuously, by flooding an area the size of Middlesex to a depth of 600 feet, and feeding the lake from a catchment area twice the size of the UK.  We'd need 150 Hoover Dams to supply the UK's energy needs, but where would we live, and where would we get the water from?

[nicephotog]

alancalverd:   ... It says that 2.3 tonnes of batterries will supply 400 AH at 240V, and I have no argument with that. That amounts to 96 kWh. Now each person in the UK consumes 5 kW,*** so to supply 4 people for 5 days you need 2400 kWh, i.e. nearly 60 tonnes of batteries.

The problem is that people (well, politicians) talk about domestic electricity consumption, but that is only a tiny part of our energy use....

*** If ever true , nobody has ever bought a RAPS anywhere in the world "ever" and is not feasible to have built such to market even *as chinese PRC business!
*..actually,...well them perhaps!?!?...

First for those that it rushes past about VOLTAGE and AMPERAGE and WATTAGE relationship:
AND how it works from solar wind and particularly A.K.A. 2.3 TONNE OF BATTERIES (..."of batterries will supply 400 AH at 240V"...)
4.1 amps at 240v (for 1 hour continuous) = 1 Kwh
8.2 amps at 120v (for 1 hour continuous) = 1Kwh
80(actually 83) amps at 12v (for 1 hour continuous) = 1 Kwh
40 amps at 24v (for 1 hour continuous) = 1Kwh
20 amps at 48v (for 1 hour continuous) = 1Kwh
...  e.tc. ..

There-fore an 80ah "accumulator(international English trade/cargo language)" in its entire stores as good as 1Kwh of charge If discharged to 100% DOD(depth of discharge) which destroys a deep cycle battery instantly!

80 x accumulators(n) is more about "trade deal cost" the more you buy the less it costs but for domestic it is simply a must to stay above the MOQ , and, 80 x (1 Kwh battery) but is divided by "6" to gain approximate 15% DOD capacity total allowed discharge p/day to allow the battery bank to last ten or more years.
These last two points are extremely serious for the TEN YEAR PLUS ECONOMICS: "Lead acid batteries(DEEP CYCLE)" quality life-cycle is usually(see the models data-sheet specifications) 1200 discharges to 30% DOD (down to 70% full) (OR only 150 to 200 discharges known as "deep cycling"), it also involves temperature, usually at or below 20 degrees Celsius,
and, one final coupling point to this, 30% DOD and above is the "float charging" range of an accumulator type battery, this means that to properly operate the chemistry, it can have a constant uninterrupted charge applied to it, below the 30% DOD level, the charger must stop for periods or the battery will get damaged(known as deep cycling)!
(NOTE: there is a lot to be careful of in making a RAPS, the reason for so many accumulators is because a single or even a small quantity of batteries cannot discharge massive currents, to distribute it requires parallel strings/rows in series to the specified system charge/store voltage A deep cycle 12v battery should not discharge more than 0.5Kwh half a Kwh per battery(and should be 48v system or higher voltage or it will simply be being *adverb* "deep cycled") or it will seriously risk damage!!!)

alancalverd:   1.  i.e. nearly 60 tonnes of batteries. , 2. ..., then takes about 6 hours to recharge

The batteries in a RAPS is not all that is simply in use, the direct take-off from either PV Panels or Wind Turbine(alike P.T.O. from a tractor) is also obtainable during current draw to the output inverter. The general rule for solar is it operates around 80% of its "rating total" of its array at best for reasons of temperature and sun angle.

More again, Australia has gone through a phase of grid tie renewables acquirement-installation (mainly only solar) in domestic electricity that is part of a national tax/tariff rebate scheme, it does/did include businesses whether commercial or industrial.
A domestic house in Australia (could be any number of people) all tends to be 25Kwh p/day to 35Kwh p/day.
This lesser sum is also the standard 2 bedroom flat unit(25Kwh p/day).
All-Electric house or flat.
# 1. Electric cooking is the bulk of electricity use 80%
# 2. Running Hot Water is often touted as the biggest but their larger domestic elements are only 2.8Kw draw and 5Kwh per boil at the biggest (time/density)
# 3. Everything else generally is done under 2.5 Kw to 1.5Kw draw except the electric kettle for a cuppa which is 2.5Kw draw at largest usually 1.5 to 2.x Kw
(to reach the 2.5 Kw draw level requires something like a tradesman with a power tool or a tradesman with a hair dryer)
(other odd points are a 500w washing machine really draws at 5Kw because of continually laboring the electric motor by "surge draw")

Nyngan NSW Austrlia 2014 - Solar power plant:
http://www.agl.com.au/about-agl/how-we-source-energy/renewable-energy/nyngan-solar-plant

List of Wind Farms in NSW Australia:
http://en.wikipedia.org/wiki/List_of_wind_farms_in_New_South_Wales

It is understandable the UK has some trouble here with large scale power generation because of size of area required , particularly for renewables methods. Maybe grow mushrooms under a solar farm?.

However, Wind appears a good solution and it appears the coastal shallows gain the edge on that problem.
So the question is not what type of renewable, but more how do you engineer economic and manageable bases in those shallows. Your looking at the wrong end of the structure , the problem you mention(what medium to draw power from) is already solved.

As for wind in a non - sunny country, 10Kw wind turbine RAPS with 1.5Kw Solar(because it's a small outlay and sun occurs enough) would suffice any medium to large domestic household.
The annoying problem is the 1.5Kw piece , like i explained before a device called a "solar controller or solar charger" holds the input float voltage steady putting in whatever amperage so with 5Kw(rated) of panels around 4.5Kw constant in good weather is available to use or allow to charge as pressure/draw occurs (automatically) after leaving the controller.
As that is, Why a 10Kw domestic turbine, because at low revs there should be around 1 -2Kw becomes available direct(bypasses accumulator bank) from the controller when it gets moving in gentle breezes.


If you are serious about wind turbines, then you need to understand the factor of obstructions and turbulence in gas not being dissimilar to that of viscosity in liquids. Again, the closer to the ground a turbine is the glue-ier the air is by pressure and hence more force loaded into more compressed gas. So it is a must to lift them at least 12m to 15 meters above the ground whether they are a 600w or a 20Kw wind turbine, but this again is because meteorology already has data proving that per 2m height gained "air speed meters per second" of wind greatly increases and is reasonably relative to height/temperature/air pressure and significant to wind turbine performance not merely the point of viscosity , turbulence and obstructions.

Percentile Layers and PBL
http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-12-00385.1

alancalverd: We'd need 150 Hoover Dams to supply the UK's energy needs, but where would we live, and where would we get the water from?

How about pre-loading wind power by wind power?
You simply make a huge bank of wind turbines BUT, they don't generate electricity specifically, they pump sea water(or compress air with the tanks exposed in the sun and a moveable shade board to make compression easier and release better - and sprays and gutters for before compression) up 50 - 100 meters into a giant blocked off valley entrance with a sealed rock and cement skin coating to prevent leaching.
Then let it go continuous as hydro electric back into the ocean.
In outback Australia we had a main river (Murrumbidgee) running past a few miles away and when i learned there were small domestic hydro units on the market 0.5,3,5,10Kw i thought of that one once because i had to fix the ball-cock on a water trough.

[alancalverd]

Just do the maths instead of shouting.

The two important numbers are population density and total power requirement per capita. Multiply these together and if the answer is greater than the renewable power input per unit available collecting area, it can't be done. It is possibly feasible in Australia because there is a negligible population scattered around a vast area of desert, but it won't work in the UK - we hardly have enough land to feed ourselves, let alone collect energy from it.   

My Aussie family have a domestic solar water heater which works pretty well but it won't run the car. 

Friends in the USA have a garage full of batteries driven by a windmill, and a forest for heating and cooking, but they still go to bed two hours after sunset because the (low consumption) lights won't work for more than a week in winter. 

[nicephotog]

First however, i'd deal with the problem of government corruptions subversive media , derogation and demeaning against wind power capabilities, along with the generous personal support of having its own electric wind power to be two faced.

That was priceless!

Good afternoon.

[alancalverd]

Corruption, certainly. Taxpayers are forced to support wind farms which only damage the stability of the grid, so some politician's brother in law must be making money out of the scam.

[nicephotog]

so some politician's brother in law must be making money out of the scam.

So, people need to have the information to, decide , outlet to acquire and construct for themselves an off-grid power system individually.
Economically it is safer and more secure (deep cycle batteries are reasonably reliable).

If someone lives 80m or more away from others they can use as small as a 5Kw (3-wind 2-solar) off-grid power system for a normal domestic house with 4 people by changing the appliances and lifestyle, and use better rostering(1 job after another not simultaneous) and they can achieve more electricity usage in 10 years at less cost than the grid.

Three quarters of personal acquisition is against fossil fuel use being the corruption because its' use is by monopolisation.

............(re edited)
The billions of dollars taken from either industrial or domestic by government for power generation is unaccountable truthfully, but also a rip off because there is no true regulation except how much can be squeezed out of every-ones pay cheque.
It is extremely advisable to have as few loop-holes in lump sum dipping as possible. Allowing expansion(of operational costs by point of it adding a profit margin to be cost effective) or monopolisation encourages and preserves corruption and prevents accountability.

[teragram]

Pumped water storage is a lot of fun. It's very expensive both in land and capital to install, which is why there are only two significant installations in the UK. Dinorwig is the larger one. Its capacity is about 10,000 kWh,[/b] so it can supply all the UK's energy needs for about 0.12 seconds, then takes about 6 hours to recharge. 

I understand that Dinorwig has six 300MW generators, or 1800MW total, rating 1650MW. Correct me please, but if it's capacity is only 10MWh, does this not mean that it can only run for

                          10MWh / 1650MW = 0.006hours, or about 21 seconds?

And yet the published information indicates that the station can operate for “up to six hours”. We must of course be careful of that old phrase “up to”, I haven’t yet found out what power output can be sustained for that period of time. 
The UK pumped storage stations (Dinorwig, Ffestiniog, Ben Cruachan, and others) were primarily intended to assist the (then) planned  fleet of nuclear stations. These have difficulty matching their output to sudden load variations, so the storage systems would have been extremely successful in helping them to cope. Fortunately it was realised that nuclear power was far to expensive, so the installation of them was abandoned. Sadly, they once again rear their heads, but judging by the tone of this discussion so far, I will not mention taxpayer subsidy, and deals with foreign energy and finance interests. 

[alancalverd]

Apologies for screwing up the decimal points earlier! Dinorwig capacity is published as about 6.5 GWh (1.3 GW for 5 hours). UK energy consumption is about 300 GW, so it could run the country for 78 seconds.

[teragram]

Thanks Alan for clarifying that.

[nicephotog]

You say the problem is space for wind turbines, looking at some of the newer small turbines that have a large number of blades and mounted on a
pole inside a short tube(to that effect) and coupling what was learned in the turbo-prop passenger aircraft industry
you could always see it as get your "blade area"(sail) from a much smaller diameter by more blades which again has less stress on the structure during torque,
BUT mount these in racks of them(sets) on a base alike a skyscrapers internal super structure with a turntable on top.
Or sort out the weight and friction for using the blades to run a ring of 6 generators(look a little like the old early 20th century aircraft rotary engines)
 not one on the spindle (as before a bit of modification to spindle and tower structure and sail power).

As all that is, there is what i said of "wind grid tied" for domestic(which happens to be considered a gigantic parasite because of economic returns
- only money is made from industry usage)
￡185 p/turbine($350AUD) , Three of these makes 1.8Kw max but performs by 24 hour at the per year level of a 3Kw solar (it's done by trickle not the rating - using rating is a bad mistake many people make , the turbine mentioned is possibly the only one can do it!!!)!!!
So this would be great for UK and Europe.....(the solar(mentioned in the document PDF) is optional but more for Australia because of air con.)
http://windsolarhybridaustralia.x10.mx/3x-mini-wind-turbine-grid-tied.pdf
In Australia, this is why the government(that owns the electricity system) didn't mind making a "RET" bill ( or a carbon emissions tax

) to fulfill green legislation nationally and internationally
because, solar, is quite worthless!; to most domestic connections on the grid and too huge for industry physically, with domestic they will cook and shower in the morning(95% of all domestic use drawn!!!) and night 3/4 of the year and personally get nothing from their panels, and again, mostly the people are not there at home during the day and the government owned supplier-broker companies regulate the "FIT deal-contract" (Feed In Tariff p/Kwh) payback from excess electricity produced from the grid tie panels e.g. 2 cents p/Kwh.

In Australia, the electricity charges(called "tariff") is four sections peak=2 periods, a few hours, of morning and night each (cooking and showers) and the most expensive, while everyone is asleep "off peak", the cheapest, and "shoulder period" is everything else and the tariff nearer peak but between peak and off peak value.
They allow all the solar panel dumping on the earth in this country, but as soon as they hear "domestic wind system" or "off grid" they scream blue murder foreign loss of capital.

So...
How can we harness wind and wave power? , It's probably illegal and we not simply have a gun in our possession but an illegal firearms type!!!!!

[alancalverd]

The problem isn't the size of windmills, though there is a practical limit to hiow big you can make them, but the energy density of wind. Wind speed squared, multiplied by air density, comes out as watts per square meter, so if you want more watts, you need more square meters of wind, not just sail area. You then design the sail to optimise the power extraction from th area you have got, and it turns out that multiple baldes work well for high windspeeds and small areas, but two or three blades are best for low speeds and large areas - it's the difference between a jet engine and a helicopter!.

[nicephotog]

The problem isn't the size of windmills, though there is a practical limit to hiow big you can make them, but the energy density of wind. Wind speed squared, multiplied by air density, comes out as watts per square meter, so if you want more watts, you need more square meters of wind, not just sail area. You then design the sail to optimise the power extraction from th area you have got, and it turns out that multiple baldes work well for high windspeeds and small areas, but two or three blades are best for low speeds and large areas - it's the difference between a jet engine and a helicopter!.

Interesting you mention helicopters.

But that then never solves the problem of compaction (of 4 to 6 x generators on one pole head)
( e.g. the picture of the wind farm here with 1 generator size-(n) output per pole... (think of six times the output from this...)
http://cdn.phys.org/newman/gfx/news/hires/2014/sealsforagea.jpg ) could be better calculated to carry four generators a head, and perhaps the friction-inertia problem can be simply reduced to a slower start-up or better auto transmission gearing (quite aware there is a limit somewhere).
My guess is the problem is the leading blade sweep interfering sonic-ally with the next blades' sweep, of which the Doppler points to density and blade shape displacement plays a role in the inefficient frequencies, a problem solved by Soviet engineers on an attack helicopter called  Kamov Hokum for its counter rotating blade set, one set sitting above the other set.
http://upload.wikimedia.org/wikipedia/commons/0/0c/Russian_Air_Force_Kamov_Ka-50.jpg
http://en.wikipedia.org/wiki/Kamov_Ka-50
http://en.wikipedia.org/wiki/Coaxial_rotors

I don't see the space on a pole being utilised well enough, they should have their physical carrying(mounting) capacity and weathering stresses modified for max, extraction by carrying many more generators on the one set of blades. The compaction would be far more productive and economic finally.

[alancalverd]

But that then never solves the problem of compaction (of 4 to 6 x generators on one pole head)
( e.g. the picture of the wind farm here with 1 generator size-(n) output per pole... (think of six times the output from this...)

You can't extract more power than the wind puts in. If your generator isn't matched  to the sail, just use a bigger generator.

Contrarotating propellors or chopper blades are very useful at low speeds as they generate no net torque, which makes slow flying and/or hovering a lot easier, but the efficiency of such a system is limited to a very narrow speed range. The Fairey Gannet was an extremely useful naval aircraft which could loiter at 20,000 ft  for several hours, travelling not much faster than the ships below it, thanks to a unique double turboprop engine.

[nicephotog]

You can't extract more power than the wind puts in. If your generator isn't matched  to the sail, just use a bigger generator.

Well aware about the sail torque AND, as i said, it's a matter of matching sail power to INERTIA and some of it FRICTION of the bearings of , the latter can be almost friction-less so it leaves inertia that can simply be reduced to a longer start-up time with an extra set of generators.
The real difficulty, is loading all of that onto a structure safely.
This is about compaction of much more into one site to operate successfully, so e.g. that previous marine wind farm picture would only be a quarter or less of its view for the same output.
I was reading the main point they have trouble is mounting the spindle for the blades because of the stresses on either the hub roots of the sails or the structure housing holding all of the blades and hub.