Tesla Powerwall - is this the answer we have been waiting for?

quentingargan wrote: »

In its favour, the round trip efficiency quoted is higher than lead acid.

That depends on your discharge rate. But a firm yes in most cases. Volatile tech. and proprietary.

Don't believe the hype go with price per kWh. Used forklift cells will do you a better deal, penny to a pound.

I'm not taking Tesla seriously until they publish some proper data.

How many of those advance orders are from Solar City?

Just finished wiring my freecycled 12.5kWh Lead Acid, AGM set for float service.

I'll be rewiring this 48V later when I find more PV. In the meantime all my swanky chargers are 12V.

This is what a real data sheet looks like.

4 years old and those Voc readings are the holding voltage since decommissioning (12.79v is the lowest). :cool:

10 Kwh wouldn't be any use to me, I'd need 2 !

My daily average consumption before getting the Nissan Leaf was about 6.5 kwh and now it's 15.5 Kwh.

Based on that my yearly requirement will have one up to around 5,500 Kwh, but not quiet because of holidays and the likes but I Get a lot of free leccy from the fast chargers about 6 Kwh worth daily but roughly I would use about 25-30 Kwh daily without the free fast charging in total including the house.

It's hard to calculate the cost of this because I use the night meter and I have to charge the car sometimes during the day when I'm on Night shift but at full 19C/kwh it would cost me 1000 A year if all that leccy was at day rate, so night rate will knock a few hundred off that.

Say 800 A year for leccy and Car, that's not bad to run the house and drive to work, petrol alone would have set me back at least 2,000-2,500.

Even if it cost me the 1,000 A year it would take many years to pay back Tesla batteries and solar PV installation which in Ireland costs a lot , maybe the cost has dropped ?

Wind turbines are disgracefully expensive to get installed and uneconomical and likely always will be. You're talking about 15,000 For a 3kw turbine.

My partners parents in Germany have 14 kwp Solar on the roof and on a Sunny Summer day can generate 70-80 Kwh. But they get a good feed-in-tariff and all have 3 phase in Germany ! They have storage heating and whatever they export in Summer they buy back at night in winter.

If Ireland had a feed-in-tariff we could use the ESB network and we wouldn't need batteries, the Government don't give grants for installation either making the whole thing uneconomical in Ireland. We're unlikely to have a feed-in-tariff for many years.

The thing with going off grid and solar, you need a mega storage capacity to keep you going through winter. 10 Kwh isn;t going to cut it by a long shot, and in Ireland you'll have to greatly over size your solar array to compensate for the reduced direct sunlight and short day light hours, though in Summer we have long daylight hours with greater need for more storage.

Electric vehicles can be used for storage for the grid.

With the Tesla Power wall you can install a night meter, charge up at night and sell suing the day you won;t have to buy solar or wind turbine. But an Electric vehicle has much more practical uses.

I really wish we'd have a feed-in-tariff in Ireland and a smart grid and grants towards solar PV and wind turbines, we could generate a lot of jobs. it could help us save the Billions we throw away on foreign energy energy.

I'm a believer in using less energy and more insulation. Ev means I don't have to spend 2500 on petrol a year, that 1,900 Euro saving (after leccy costs) is a saving I can directly put towards repaying the car not including the maintenance !

rolion wrote: »

What if based on a proper PV panel system of let's say 3kw,we can use three storage systems:
-direct feed in to homes circuits except kitchen with cooker,wash machine,iron and maybe hoover.That implies learning and adapt the internal electrical circuits for the supply and load
-battery storage with a minimum capacity of let's say 300-400ah.With 6 x 2V at the Ah should be capable of powering the house while been able to charge quick enough and avoid deep discharges.
-heating a 1.5kw / 3kw heating element in a 300l hot water cylinder.Water can be used in heating of radiators and / or underfloor heating.With a cylinder "losing" thermal capacity in let's say 8 hours you can "jump" to next sunny day with overnight supply.If not,boosted a little with supply from battery as night time is less usage.

So,with a proper design online/offline/by-pass continous monitoring and automation it can be used to work efficient and to return the investment sooner.
But,I guess are others like me,the solar systems (solar tubes or PVs) are there to satisfy my "anger" at the sight of gas and electricity bills.My desired target is to get both at less than a hundred euro per issued bill.At the moment,before fully insulating the house internal and external came at average 450 per bill.

Good luck...

You'll want a pretty large array for winter, massive !

My OH Parents in Germany have a 14 kwp array on the roof and while up to 70-80 kwh can be generated a day in bright sunlight on a dark cloudy day in Summer it can generate as little as 1000 watts continuous,

So 1 Kw over what, 7 hrs in winter sunlight = 7 Kwh, that doesn't account for the brigher spells so you might generate 10 kwh.

Solar PV isn't there yet as far as storing the energy in batteries is concerned, Grid-tie systems are best, storing huge amounts of energy in batteries isn't possible to tie you over winter.

And the Electric grid in Ireland isn't nearly as good as Germany's, German homes all have 3 phase which naturally allows you the option of large PV arrays or wind to the grid, in Ireland the max allowed to the grid is about 5.5 Kw ! useless !

Most likely the same tech yes.

Who's going to pay for this ? We already pay huge subsidies to wind energy investors, and shamefully get nothing in return.

I got a better idea, if a lot more people convert to electric cars then these can be the energy storage devices these companies desire.

Most people don't drive within the range of even the current electric cars so why not use some of that energy at peak times ?

Sir Liamalot wrote: »

Will the grid pay you for the charge cycles taken from your "idle" battery. They have a finite lifespan.

That's the idea, but it will require massive upgrades to the electric grid.

In fact you could charge at night and use the cheap electricity during the day to power your house.

This is what the ESB are looking into. But it's a long way away but IMO a really good idea and it would save having to invest in huge storage systems.

The ESB are looking into 2nd hand ev batteries for storage but this will be many years before used batteries become available and the current gen leaf since late 2013 battery is lasting very well, should easily have a 10-15 year life to 70% possibly more. But it's lasting very well, my 2015 leaf with 18,300 Kms has still got 100% capacity!

Sir Liamalot wrote: »

I'm building such a system. Can't say it makes any financial sense tbh.

When I look at the round trip efficiency I'll be saving 50% price per kWh on import then losing 10% on the inverter, 15% on the battery charger and ~15% on battery charge inefficiency. All rated efficiencies not actual.

It'll be a year or two before I have real figures. I'm hanging 1.5kW PV to offset the losses.

Well this is where using EV batteries makes a lot of sense , people think they need 500 miles range but in reality they drive less than the max range of a Nissan Leaf daily so if you drive 40 miles a day max you'll have about 8-10 Kwh sitting in your leaf battery. Unfortunately I have an 84 mile daily commute so would have little energy to spare but it saves me a fortune over Petrol/Diesel/hybrid and I've driven 18,300 Kms since January and If that was all night rate would have cost me about 250 Euro's V 1,100 Euro's in Diesel @55 mpg and 1.18 per litre current rates. But I've charged a lot for free at the public charge points so it;s cost me a lot less.

So you could have a couple of options, you can charge at the cheap rate at night, go to work come home and do your cooking, washing and shower all with the spare Kwh left in your Leaf. Or you could export it. Yes it would mean more cycling of your battery however we're only slightly over 2 years away from 150-200+ mile affordable electric cars and these batteries will be cycled far, far less than a leaf battery so will have the ability to store and export large amounts of Kwh.

The Tesla Model S battery at now 90 Kwh is so big that even with a 30% loss in capacity should still see 180 miles range. It's a huge amount of energy most Irish people would use extremely rarely .

In Japan after the earthquake Nissan introduced such a system but I don't know whether you can export the energy to the grid or whether it's intelligent enough to not pull the energy from the grid and only from the Leaf. I don't know the cost of the system.

But if you already have an EV you already have a storage battery. I will see if I can find more details on the System Nissan sell for the Leaf in Japan.

recedite wrote: »

Is that accurate?

recedite wrote: »

Interesting, but I presume that is what is says on the dashboard display. Is that accurate? Lets say your battery was half knackered after a few years, and you fully charged it, would the display read "100%" for charge even though it wasn't the same capacity as a new battery?

There are two battery meters one ont he very right is for capacity and one for % the one for % is your actual charge in the battery the one on the right has 12 bars and each one lost is capacity lost. And you are correct, as the battery ages a full charge will always show 100% because that means 100% charge of what's available in the battery based on how worn , or not, it is.

Yes it's pretty accurate because I use a diagnostic tool connected to the OBD II port which is more accurate than the leaf display. The leaf will loose one capacity bar after around 12% has been lost. The Leaf Spy application will tell it to the exact %.

One U.K Taxi has reached over 102,000 miles and lost around 10% but the battery has been fast charge something ridiculously, 1,700 fast charges and about 5,500 Normal charges and I wonder if it wasn't fast charged so much would it have lost less than 10% ? but either way it's extremely good for a battery that's cycled so much.

Capacity varies due to usage sometimes it reports 95% and sometimes 100%. But there is very strong evidence from the U.S to the U.K now that the battery from late 2013 on has be altered for much better durability.

The battery in late 2015 for 2016 will have an extra 6 Kwh, not sure whether this is usable but my guess it will be.

quentingargan wrote: »

I have a PV array and an electric car, but I wouldn't dream of charging my car during the daytime. It is far better from an environmental point of view to export your solar PV to the grid (I get paid 9c for it) and buy back electricity at night to charge the car (I have a day/night meter so this is also very slightly cheaper).

Unfortunately the Feed-In-Tariff is being scrapped next year ? I think this is outrageous for people who have invested in Solar PV. So in your case and those in a similar situation I suppose the Powerwall would be good thing but what would it cost including installation ?

The EV would be the best thing because you already have it but you're probably not there during the day.

What Kwp have you installed ?

quentingargan wrote: »

One of the benefits of electric cars is that they can use up surplus electricity on the grid at night. Often a high percentage of power on the grid at night is coming from wind.

Yeah it would be great if a lot more people were interested in electric cars but most people don't see the savings because they dump up to 80 A week maybe more into the tank and forget it where if they got a bill every month it would shock them a lot more, a lot of people don't like bills because their spending is written down in front of them but when they throw up to 80 Euro's in cash away into the fuel tank it's forgotten about and people are quiet willing to do it which is even more insane.

So far this year 116,333 cars were sold and if they were all electric charging at let's say 6.6 Kw that's 767 MW of power by my calculations and this is a lot of extra power on the grid but can be done.

Our current demand is 4,500 MW and at midnight it was around 3,000 MW. So we would have the capacity if all our cars changed to EV if all of them sold so far were EV however it's not as simple as this because most Nissan Leaf's for instance are sold with the basic 3.3 Kw charger so if all electrics were sold with this 3.3 Kw charger you could charge twice the amount with the same capacity and not all cars will charge for a full 8 hours for a complete charge. And if they were all 6.6 Kw they would charge in half the time freeing up capacity. The benefits of that 6.6 Kw AC charger are tremendous , being able to charge twice as fast from a non fast charger just can't be underestimated.

If you were to change our entire transport to the grid then the amount of electricity required would be tremendous and why wind energy alone won't imo ever meed this demand. I think renewables will play a part but we need to think about Nuclear at this point, unless we get a large amount of turbines off shore I think we'd need turbines on every inch of the land.

We need to think about Solar PV because the last few weeks have seen little wind energy to the grid 5-10% with one or two days where this went to 35%. Solar will work in Ireland and afaik a lot cheaper than wind.

Check out this link, very interesting.

http://smartgriddashboard.eirgrid.com/#all