Residential wind/solar installations?

[Nyden]

Thought I would pose a few questions here; in the hopes that a few of you may have experience in this area.

Does anyone here have any Wind turbines, or solar panels installed on their property? If so, how beneficial / practical are they? One would assume that they would pay themselves off eventually, but surely after that time they would be nearing their end anyway? Mechanical vaults?

Can they be used as a means of passive income? A home-based little wind-farm, selling back to the grid?


With ever-increasing costs, & no real sight of a sudden decrease in energy costs ... just seems to make sense for individuals to start looking for their own little alternative means.


Thank you in advance for any responses!

 

[metric]

i, personally have a wind mechanism fitted by natural means. all it requires to work efficiently is beer, or beans....

 

[treefrog]

Thought I would pose a few questions here; in the hopes that a few of you may have experience in this area.

Does anyone here have any Wind turbines, or solar panels installed on their property? If so, how beneficial / practical are they? One would assume that they would pay themselves off eventually, but surely after that time they would be nearing their end anyway? Mechanical vaults?

Can they be used as a means of passive income? A home-based little wind-farm, selling back to the grid?


With ever-increasing costs, & no real sight of a sudden decrease in energy costs ... just seems to make sense for individuals to start looking for their own little alternative means.


Thank you in advance for any responses!

excellent and interesting question nyden

think we can disregard wind as it requires poking a turbine up in the air and there would be stiff opposition to that in residential areas - bad enough out in the bush - they are a blight on the landscape for mine and often very low output at peak times

on the remainder of the green homes trinkets I am currently building a retirement residence on kangaroo island SA and have just spent a lot of time researching viable options - you may be aware that SA govt has decided to become a world leader in solar use and has legislated that solar input to the grid from your own home will get you garanteed credits of 44c/unit - sounds great and we all rush to by our photo-voltaic systems to make a quid and save the earth.
well a lot of energy has to be used to manufacture those cells so their likely benefit to a green earth is debatable (we are talking small scale here)
and cost ?? to you and me $$$wow!
with the fed govt rebate for a "owner lived in residence" of $8000 the best you will get (cost/benefit basis is a 1 unit (kwh) peak) system that costs $5000
ok we are all meant to say hey great! I will generate about an average 5kwh per day back into the grid and make some pocket money for my $5000 system
well think again as to get that sort of maximum output you need to have all your own consumption at zero for the whole time and even a 4 star frig (not many about they are fairly rare) will draw almost 1.6kwh/day: so how will we get our 44c/unit? - only if we have NOTHING electrical in the house during the day.
so we look at stepping up in size and ask how much for a 2kw pv system and the numbers are $24000 (less the max gov rebate of 8000) so its getting worse on a economic return prospect and I'll bet even a 2kwh hr system will struggle to register any input to the SA grid in a normal, enviro conscious home owner
so what did we decide? scrap the solar power - absolutely no contest as there will be ongoing maintenance and other costs as well as efficiency deterioration of the cells over time - dust, birds, and general shine loss which they do not want t tell u about
then turned to solar hot water and this is also of dubious benefit but with planning and building code requirements requiring 5star energy efficiency it is difficult to achieve that without adding some form of solar gadget so we decided to spend 6000 on solar hws
we then decided to put in a water recycling system - reuse the grey water and save the once mighty murry stuff
well having worked in the water treatment area I thought go man go - this is it - will sort these out and after 4 days of research/contact with the gear out there I decided on a victorian developed unit that produces class A recycled water (can actually be used domestically thro sprinklers if u choose and approved for re-use in the wc's and wash m/c) but by the time you get the required collector tank, treatment system, and holding tank completed that was $15000 and still had to sign a maintenance contract with the supplier for 3 monthly calibration/operational checks - so scrap the recycled water bit - this became an easier decission once you factor in that SA is the only state that will not allow any class of recycled water to be other than used with underground irrigation - so vic A class is SA B class
so in the save the water department we just decided on a few rainwater tanks 50000L actually for $10000 mostly for the bonus points toward the 5star caper
all in all, a major disappointment as was looking forward to heading toward "self sufficiency"
conclusion - the residential greening thing is almost total crapp
cannot form any other conclusion other than the govts must bight the bullet and go neuclear and generate sufficient power to have large desal plants that supply the water needed and generate clean power that will do this as well as provide clean power for general electrical use though the existing grid

 

[Tysonboss1]

The best, most cost effective way to capture solar energy is a Solar hot water system,

It's not as sexy as photovoltic cells, But a 1 hotwater cell will heat your hotwater tank in about 2.5hrs, it would take 5 Photovotic cells all day to generate enough energy to heat your tank.

As far as using solar to generate income,.... you would be better putting the mony in an ING account,

a solar photovolitic system takes 20years to pay for itself,

a conventional solar hotwater system takes about 2.5years,.... and you have to have a hotwater system anyway.

 

[Tysonboss1]

If you want to save money and uses alternative energies.

Convert your car to LPG, and convert your hotwater to solar.

these two things can reduce your energy bill by up to 40% and pay for themselves is about 2.5years.


Forget solar cells,

 

[treefrog]

If you want to save money and uses alternative energies.

Convert your car to LPG, and convert your hotwater to solar.

these two things can reduce your energy bill by up to 40% and pay for themselves is about 2.5years.


Forget solar cells,

agree those two things are up there for payback but you are not taking into account there total (ZBB) costs - much much nearer 6-8years payback for both - straight gas h/w systems are very cheap to buy/install and run and that is why there is little difference in BASIC credits when constructing or extending your home whether u put in solar hws ($6000) or gas hws (<$1000) - and basic cares not what your capital costs are

things that do give a much quicker payback are reconfiguring your windows to give better energy efficency (including pelmeted curtains) and replacing incandescent with energy efficient lamps - oh and a third , ceiling fans

http://www.yourhome.gov.au/technical/index.htm

 

[grizzly1]

For the technical stuff try this link, best one in my long search for sense on this topic

http://unisun.com.au/

One point I learnt from this site is the commonly available PV cells have a tendancy to decrease efficiency above a certain temperature, which is more commonly encountered in OZ than in countries where they are commonly rated. And another, transmission of the dribble of power coming from a domestic roof is laughably inefficient, think of the system we are familiar with high voltage transmission wires that snap crackle and pop to cover the distances from production to user with graduated stepdown to appliance, then think of your appliances, they get hot for they convert high voltage AC to low voltage DC yet we will create low voltage DC from PV's on our roofs. Grid feed is a fight against Physics, Edison and Tesla decided this one some time ago.
From what I learnt while considering "going green" I agree with all the posters re payback.
I'd love to have PV & wind turbines but I fear spending my money reducing consumption will be a better option, good luck

 

[Smurf1976]

Agreed with what others have said.

It's not economic for you to make cars, refine oil or manufacture paper in your backyard and it isn't economic to generate electrcity either.

It all comes down to scale no matter what the technology being used.

The 3,240,000,000 kW Loy Yang coal-fired plant (Vic) will economically blow away anything you do with a small boiler and truck load of coal at home.

So too the 480,000 kW Pelican Point gas-fired plant (SA) will leave you for dead financially if you try setting up your own gas turbines.

And no amount of messing about with the local creek will make you a serious rival to Snowy or Hydro Tas.

Same with solar and wind. Great big 3000 kW machines connected to the grid with centralised (ie more efficient) co-ordination of operation, maintenance etc easily beats a single 1kW turbine sitting on your roof.

And a 200,000 kW solar thermal tower is absolutely more economic than any number of panels.

44c per kWh I hear? That's about 7 times what one Australian company is actually achieving with wind and the estimates (unproven at this stage) for solar thermal and geothermal are similar.

I'd argue that if electricity generally cost 44c / kWh then demand would disappear almost immediately. Certainly in Tas I know for a fact that 50% of load would disappear forever within 48 hours if that price became permanent and 70% would be gone within 12 months. And those figures don't include any general move towards efficiency or the effects of a collapsed economy - they are simply for loads that aren't viable at that price. For Qld it would be very similar, less so in the other states but still a lot of demand would disappear almost immediately at that price.

Before anyone gets excited and sees that as the solution, I must point out that we're talking about outright economic depression here with a collapse of exports and not simply turning out a few lights. Even the 1930's didn't come anywhere near that in terms of energy saving.

Bottom line is electricity (and fuel in general) is only of limited use beyond a certain price. Beyond essentials, it's cheap power that is useful, not power per se.

If we're going to switch to solar, wind, nuclear, geothermal or whatever then large scale via the grid is the cheapest way of doing it. I must also point out that CO2 emissions from making all those panels are rather significant - an order of magnitude greater than large scale hydro, wind or geothermal and not much different to a modern gas-fired plant.

Solar hot water etc works though since it's simply collecting and transferring heat that can't otherwise be used. But in financial terms forget generating your own electricity unless there's a massive drop in not just price, but actual resource inputs needed to make the panels.

 

[Julia]

Nyden, this isn't exactly a response to your question but might be a bit of an indication as to the viability of solar.

I have solar heating for the swimming pool. Before installing it, I spoke to a number of people who had tried it and said "aw, it doesn't work". Further questions brought the response that they had installed on the roof collector material only about one third of the pool's surface area. Consequently the small amount of heated water made little difference to the pool temperature.

I installed 150% of the pool's surface area in collector tubing. On a sunny day this will raise the temperature of a 50,000 litre pool at least one degree per hour.

In contrast, the heat pump (hugely more expensive to install and to run) takes three hours to raise the pool temperature 1 degree.

So, what I'm suggesting re your solar panels is that perhaps you need to install a greater area than is usually suggested to give you an effective result.

 

[treefrog]

Agreed with what others have said.

44c per kWh I hear? That's about 7 times what one Australian company is actually achieving with wind and the estimates (unproven at this stage) for solar thermal and geothermal are similar.

I'd argue that if electricity generally cost 44c / kWh then demand would disappear almost immediately.

the 44c that they are about to pay is actual legislated - take from the grid at 22c, back to the grid at 44c

the point I was making is that it is a con because for the reasons stated (frig and other base load) it will be extremely unlikely that people will be able to pump their surplus back into the grid because they cannot use all grid power and pay the stipulated 22c and produce 2kw/hr peak on optimum day and get the legislated 44c - it just ain't gunna happen because you MUST use your own solar generated for your own purposes first. what it will do is reduce total SA electrical demand somewhat but at huge cost to the consumer for their capital outlay. if a private co tried to do it they would end up in gaol for fraud - same as lotto - govt does it so all OK

 

[Dukey]

I've been having a close look at this recently for my dads place in NQ. And although i understand most of the arguments pointed out below - I think the scheme still has some merit - probably from more individual &/or educational standpoints than from a national 'power grid' perspective.... I mean - obviously, even if we manged to get 1% of all houses on grid connected solar systems, thats barely a piss in the bucket of the whole grid, but for individuals it might be worthwhile....
that is provided you can give up the $$$ hard core investors 'comparative' view that if spending 15-20k now for a few %pa return (if that) from a solar system, can't possibly match the $$ return of XYZ shares ... so you'll just buy a few more XYZ shares every time!!

But if considered in terms of a subsidized capital investment / improvement on your house NOW which will see you have greatly reduced (or nil) power bills a few years down the track... then it's a bit more attractive

# A positive selling point for your house in a future 'green conscious' world.

# How about the forecasts of rising elec. prices into the future.... thats gonna make your installed and functioning Solar system even more valuable ...

If there was oil under your garden and you could spend a few $k now to put in a small rig and have cheap or free oil... in a future of rising oil prices... would you do it??

If the government said they'd pay 25-50% of the cost of the rig... would you do it? ( I think I might consider it!)

## Educational / awareness value.

The greatest (& cheapest) way to addess our 'electricity addiction' is to cut down our use, and solar systems - esp on schools and and public buildings can play an important role in educating the masses ... people are interested in it and I mean... It blows me away how many people have no idea how much juice their air-con's, pool filters and giant bloody plasma tv's chew!!! But if you have a solar elec. system on your house... you'll be watching that meter and turning things off, dragging your daughters out of the shower kicking and screaming!! (unless you have a nice fat Solar HWS !).

## I also expect that the technology will improve, such that when it comes time to replace the cells (and they are supposed to last 20-25 yrs - dunno how realistic that is... smurf??) - there will be much more efficient panels to slap on the roof... and probably cheaper.

## as far as transmission losses go - my understanding (& please correct me if I'm wrong) was that the greatest losses are in transporting elec. over large distances. ie - we have large losses in NthQld as most of our power coming from SEQld.
Losses from the roof panels to the grid through 1 transformer a few metres away might not be so bad . ???

anyway - some points to ponder

- great and wide-ranging discussions on ASF - as always

- Dukey

 

[Dukey]

the 44c that they are about to pay is actual legislated - take from the grid at 22c, back to the grid at 44c

the point I was making is that it is a con because for the reasons stated (frig and other base load) it will be extremely unlikely that people will be able to pump their surplus back into the grid because they cannot use all grid power and pay the stipulated 22c and produce 2kw/hr peak on optimum day and get the legislated 44c - it just ain't gunna happen because you MUST use your own solar generated for your own purposes first. what it will do is reduce total SA electrical demand somewhat but at huge cost to the consumer for their capital outlay. if a private co tried to do it they would end up in gaol for fraud - same as lotto - govt does it so all OK

The story I got - from looking at an Ergon energy contract - was that it works on 'net metering' as you suggested - so yes you are correct - you WILL NOT (according to Ergon at least) get payed 44c per kWh for ALL the elec. you produce - only the excess.

If your system is big enough to generate NET EXCESS elec - then they will pay the 44c per kWh on that... up to a limit of ... I think it was 10000 kWh/year (??) being the maximum amount they would buy. <<<EDIT not sure about his bit but there is a limit.>>>

So the incentive is to reduce your usage I guess. And the system will work better if you have a solar HWS as well and take advantage of those rebates too.
If you have a big family and high elec use: then you are in trouble.
But even including hot water - my folks for example average about 15kWh per day (yep - they are old school tough - they rarely use air-cons... in townsville).
A 1000W system will probably produce something like that up here... most days... sunny Townsville
A 2000 W system should **** it in, and they would be feeding excess back to the grid and being payed for it.

(once again - anyone feel free to correct me if any assumptions or figures are wrong).

I also heard that Canberra and maybe Vic were thinking about legislating 60c / kWh.

 

[treefrog]

But even including hot water - my folks for example average about 15kWh per day (yep - they are old school tough - they rarely use air-cons... in townsville).
A 1000W system will probably produce something like that up here... most days... sunny Townsville
A 2000 W system should **** it in, and they would be feeding excess back to the grid and being payed for it.

nope - not even in towneysville - 1kw system is peak output optimum conditions - 12hrs sun = about 7-9kw/day
even a 2kw (remember that's peak again) system will barely do it - I think u would need a magnifying glass to read the numbers of what u put back into the grid with a 2kw system if your consumption was 15kw/day ave

 

[Dukey]

nope - not even in towneysville - 1kw system is peak output optimum conditions - 12hrs sun = about 7-9kw/day
even a 2kw (remember that's peak again) system will barely do it - I think u would need a magnifying glass to read the numbers of what u put back into the grid with a 2kw system if your consumption was 15kw/day ave

You're right - I was looking at the wrong figures in my notes... back to the drawing board...

Maybe even less ....like 4-5kWh per day per 1000W system.

damn hell and blast...

certainly less economic - though I still feel some of the other benefits are worth considering....
at some point we might have to stop thinking only with our hip pockets and take a leap into the future...?

 

[Smurf1976]

the 44c that they are about to pay is actual legislated - take from the grid at 22c, back to the grid at 44c

the point I was making is that it is a con because for the reasons stated (frig and other base load) it will be extremely unlikely that people will be able to pump their surplus back into the grid because they cannot use all grid power and pay the stipulated 22c and produce 2kw/hr peak on optimum day and get the legislated 44c - it just ain't gunna happen because you MUST use your own solar generated for your own purposes first. what it will do is reduce total SA electrical demand somewhat but at huge cost to the consumer for their capital outlay. if a private co tried to do it they would end up in gaol for fraud - same as lotto - govt does it so all OK

My main point is simply that if we start putting significant amounts of energy into the grid at 44c / kWh then in short society ends up going broke. Clean and green maybe, but financially unworkable. The SA scheme only works if it doesn't become too popular and thus doesn't provide a real alternative to fossil fuels.

It doesn't scale up whereas centralised geothermal, hydro, solar thermal etc do scale up and, combined, are a lot closer to being a real alternative. 6 - 7 cents / kWh is still problematic economically, quite seriously so in fact, but it's a lot better than 44 cents / kWh.

Conventional black coal and gas-fired generation costs are in the order of 4c / kWh baseload by the way. Higher for low load factor (peak load) plant. Wind varies but take 6 - 7 for a good company with a good site, higher for dud companies and dud sites. Solar thermal and geothermal should, in theory at least, be similar. Nuclear is likely to be a bit higher than that for an Australian plant. Hydro varies a lot and is site specific - most of the significant Australian schemes were built simply because they were cheaper than coal.

The common factor in all of these alternatives is that they are capital intensive. It's easy to spend $1 billion on wind, hydro, solar etc and end up with what is at best a medium sized power station. Very cheap to run once it's built, but you'd better be cashed up to start with.

 

[Smurf1976]

certainly less economic - though I still feel some of the other benefits are worth considering....
at some point we might have to stop thinking only with our hip pockets and take a leap into the future...?

Society only has so much we can spend on power generation. I mean, it just doesn't work if we decide that we're all going to spend 90% of our income on power stations or energy efficiency.

So it makes sense to go for the biggest bang for our buck in terms of output, carbon reduction or whatever other criteria you choose.

Bottom line is this. Put $10,000 into solar on rooftops and it will save a small amount of CO2. Put that same $10,000 into geothermal, solar thermal, hydro, wind etc on a large scale and it will save an order of magnitude more CO2 than panels on the roof.

So if we want to save 5% and stop there then panels on the roof will do it. But the same money could save many times that if put into large scale centralised generation.

I'll use some figures for a large scale example. The Hydro's local operations (that is, Tasmania and excluding interstate and overseas) amount to an investment (replacement cost) of about $25,000 per head of population or over $55,000 per household. It costs little to keep going and there's no reason why most of it shouldn't still be in use 100 years from now (indeed one plant already is over 100 years old). It is financially viable and competitive with mainland and overseas coal-fired power.

If we had gone solar on house roofs instead of dams on rivers then that cost would be $150,000 per head of population or about $330,000 per household (which is more than the average house price in Tas). And we would have to replace the whole lot every 20 or so years. And those costs don't include some means of storage (batteries etc) that also requires frequent replacement. And as if that's not bad enough, solar panels are far higher CO2 emitting than hydro (or geothermal, solar thermal, wind) due to their embedded energy.

Now, I ask you this. Can you afford to be spending $16,500 each year replacing solar cells? Didn't think so. And that's without even mentioning the return on invested capital, which would be borrowed money in practice for most.

Don't forget that if it's going to be large enough to make a difference then everyone from your employer to the local supermarket will be factoring in a massive cost via reduced wages, higher prices etc. If you want an example of how this works, then consider what would happen if petrol, diesel etc went to $9.30 a litre, which is about the same cost as energy from rooftop solar panels. It wouldn't be pretty...

Panels on roofs work politically. But replacing trucks with trains, investing in large scale renewable generation, solar hot water and so on are far more effective at turning $ into CO2 reductions. You'd be better off giving your neighbour some insulation and a solar HWS than bothering with solar electricity yourself and it would save far more CO2.

A Quantum heat pump water heater will cost you about $1000 more than a conventional electric unit with the rebates that are available. Now there's something worth doing - pays for itself in a few years at most and saves rather a lot of CO2 as well. Even without the rebates it stacks up a lot better than generating your own power in a suburban area.

 

[Smurf1976]

## as far as transmission losses go - my understanding (& please correct me if I'm wrong) was that the greatest losses are in transporting elec. over large distances.

It varies a lot with location but take 10% loss from power station to your house as a rough figure unless you're either right next to the power station or in the middle of nowhere. The actual figure will vary with location, time of day (and time of year in some situations) etc. A small number of individual consumers in rural areas do have very high losses but for most it's not as big as commonly assumed.

Shifting load to off-peak times will reduce losses somewhat. It also improves generation efficiency and reduces running of the least efficient generation. It varies but at the extreme, peak load generation can be 100% higher CO2 emission than baseload. Typically it's not that bad but it's still less efficient than baseload.

 

[Dukey]

Society only has so much we can spend on power generation. I mean, it just doesn't work if we decide that we're all going to spend 90% of our income on power stations or energy efficiency.

So it makes sense to go for the biggest bang for our buck in terms of output, carbon reduction or whatever other criteria you choose.

Bottom line is this. Put $10,000 into solar on rooftops and it will save a small amount of CO2. Put that same $10,000 into geothermal, solar thermal, hydro, wind etc on a large scale and it will save an order of magnitude more CO2 than panels on the roof.

So if we want to save 5% and stop there then panels on the roof will do it. But the same money could save many times that if put into large scale centralised generation.

I'll use some figures for a large scale example. The Hydro's local operations (that is, Tasmania and excluding interstate and overseas) amount to an investment (replacement cost) of about $25,000 per head of population or over $55,000 per household. It costs little to keep going and there's no reason why most of it shouldn't still be in use 100 years from now (indeed one plant already is over 100 years old). It is financially viable and competitive with mainland and overseas coal-fired power.

If we had gone solar on house roofs instead of dams on rivers then that cost would be $150,000 per head of population or about $330,000 per household (which is more than the average house price in Tas). And we would have to replace the whole lot every 20 or so years. And those costs don't include some means of storage (batteries etc) that also requires frequent replacement. And as if that's not bad enough, solar panels are far higher CO2 emitting than hydro (or geothermal, solar thermal, wind) due to their embedded energy.

Now, I ask you this. Can you afford to be spending $16,500 each year replacing solar cells? Didn't think so. And that's without even mentioning the return on invested capital, which would be borrowed money in practice for most.

Don't forget that if it's going to be large enough to make a difference then everyone from your employer to the local supermarket will be factoring in a massive cost via reduced wages, higher prices etc. If you want an example of how this works, then consider what would happen if petrol, diesel etc went to $9.30 a litre, which is about the same cost as energy from rooftop solar panels. It wouldn't be pretty...

Panels on roofs work politically. But replacing trucks with trains, investing in large scale renewable generation, solar hot water and so on are far more effective at turning $ into CO2 reductions. You'd be better off giving your neighbour some insulation and a solar HWS than bothering with solar electricity yourself and it would save far more CO2.

A Quantum heat pump water heater will cost you about $1000 more than a conventional electric unit with the rebates that are available. Now there's something worth doing - pays for itself in a few years at most and saves rather a lot of CO2 as well. Even without the rebates it stacks up a lot better than generating your own power in a suburban area.

Smurf I think we are talking about two different things here. I wasn't advocating solar panels on every rooftop in an attempt to provide baseload power - it's not practical for all the reasons stated by yourself and others in previous posts. Hence my suggestion that 'rooftop solar' would only ever amount to a 'piss in the bucket' (a big bucket!).
...And as such - the impact of this government subsidy on energy prices will be negligible in my opinion ... particularly in comparison to the impact of other factors such as rising energy commodity prices.

What I see is a possible future benefit in governments supporting a range of technologies - including PV solar - which can complement each other, rather than putting all eggs in one or two baskets. With some support, new and improved solar cell technologies may well come to light... possibly changing the efficiencies and economics of solar power quite dramatically.

.... or is that absolutely impossible ? Maybe I have too much faith in my whitecoat mates! but 'Solarsystems' seem to be onto something... maybe...
http://www.solarsystems.com.au/the_technology.html
- though obviously not a rooftop system.

-Back to one of Nydens original questions (for anyone)...

- How long do the current generation of panels last... in the real world ? (I believe those made by sharp are guaranteed for 25 years ... is that realistic?)


and regarding Hot water systems:

- Which is most efficient between rooftop Solar HWS or Quantum heat pump system?

- Can we direct the cold air from the quantum heat pump to some kind of refrigeration or air-con use... is there enough 'chill' to be useful ?
-dukey

 

[treefrog]

My main point is simply that if we start putting significant amounts of energy into the grid at 44c / kWh then in short society ends up going broke. Clean and green maybe, but financially unworkable. The SA scheme only works if it doesn't become too popular and thus doesn't provide a real alternative to fossil fuels.

It doesn't scale up whereas centralised geothermal, hydro, solar thermal etc do scale up and, combined, are a lot closer to being a real alternative. 6 - 7 cents / kWh is still problematic economically, quite seriously so in fact, but it's a lot better than 44 cents / kWh.

totally agrees - in fact agrees 102% and that is the max that frogs agree with smurfs

 

[jonojpsg]

Wait a few years and they'll have developed a commercial solar PV cell that runs at at least twice the current efficiency. Existing solar PV only uses the red wavelength of light whereas they are developing cells that generate electricity from all the visible wavelengths which will obviously improve efficiency.