Solar panels, is it possible to reduce bills to £0 with them?

Cardew

Not sure if things have changed recently, but storage and charging of lead acid batteries were covered under Health and Safety regulations.

With adequate ventilation mandatory, I suspect that it would be a hanging offence to store and charge batteries in a house.

Energetic_2

grahamc2003 wrote: »

Would you mind posting a link to this storage system?

Storing 5 days worth of energy certainly won't be cheap and is generally viewed as non-viable at all for the average person. While solar generation at this time of the year is unlikely to be zero, it's likely to be very low - last week I generated 2kwh. At the same time, heating would be well above average heating needs, so swings and roundabouts there.

The op, I think, is saying he uses 6kWh per day, which is incredibly low if it includes electric heating, but anyhow, lets run with those numbers.

Let's assume a low cost low tech system, and just consider the battery costs with rough estimates. To get 30kWh (5 days, assuming full charge and full depletion - in itself problematic) he'd need to generate 60kWh assuming about 75% charging efficiency, to store 45kWh, and have available 30kWh (assuming about 75% discharging efficiency).

So about 45 average sized car batteries would be required, roughly, to store 45kWh (1kWh per battery). Reasonable quality batteries would be £100 give or take, so £4,500 for the batteries. There are other problems and other costs of course.

Would be interesting to see how the system you are describing compares with the low tech ball park costs.

http://powerrouter.com/

Exactly, going off grid is largely pointless if you have a grid connection due to storage costs. The Powerrouter gives you the ability to store some energy but will switch back to the grid once the batteries reach the preset discharge rate. So you only need to size the battery for one evenings worth of use X2 for a 50% discharge. There is no need to size in 5X days of autonomy as the grid is there to cover it which reduces the battery size/cost. It's a halfway house...

Energetic_2

Cardew wrote: »

Not sure if things have changed recently, but storage and charging of lead acid batteries were covered under Health and Safety regulations.

With adequate ventilation mandatory, I suspect that it would be a hanging offence to store and charge batteries in a house.

http://www.alternativeenergystore.co.uk/victron-220ah-12v-deep-cycle-gel-battery.htm

This is the battery our supplier supplies (this is not my supplier). The trade price is significantly less so ignore that.

As to charging, i think a ventilated store/garage would be the best option, the enquiries we've had so far have not gotten as far as planning battery stores unfortunately but our suppliers are very knowledgeable and woukd assist with this should we get a genuine enquiry.

e

spgsc531

Energetic wrote: »

SMA do a battery UPS, Sunny Backup, it is essentially an automatic system rather than a 'lifestyle choice'. They also do the sunny island which is a synthetic grid and isolator to keep the inverter going on an outage without sending anything down the line.

Power one do off grid and island systems also, there are probably more but it's been a while since I looked into it in any detail.

E

SMA rings a chord. I'm sure I read somewhere they are soon to release to market a grid connected inverter with battery backup, that would charge during the day to provide power at night. I may have the company wrong, but I definitely read about it coming soon.

rogerblack

Energetic wrote: »

http://www.alternativeenergystore.co.uk/victron-220ah-12v-deep-cycle-gel-battery.htm

This is the battery our supplier supplies (this is not my supplier). The trade price is significantly less so ignore that.

As to charging, i think a ventilated store/garage would be the best option, the enquiries we've had so far have not gotten as far as planning battery stores unfortunately but our suppliers are very knowledgeable and woukd assist with this should we get a genuine enquiry.

e

The above battery will store about 2kWh.
A total of 600kWh at 100% and 50% discharge before it likely needs replaced.
This is about 80 quids 'worth'.
Even if you have free infinite solar panels, you end up considerably more expensive than grid.
You will also need about 1000kWh of power to charge these, as the battery and charger are inefficient.
You would really need a battery bank capable of at least lasting 3 days or so at normal load, to be close to 'off grid'.
And then you will either need to connect to the grid if it's been dull for a few days, or a generator.
You will need at the minimum a battery pack that can be charged at a high enough power to absorb all the solar panel output.
This means for a 4kW array, 20kWh of batteries.

Energetic_2

rogerblack wrote: »

The above battery will store about 2kWh.
A total of 600kWh at 100% and 50% discharge before it likely needs replaced.
This is about 80 quids 'worth'.
Even if you have free infinite solar panels, you end up considerably more expensive than grid.
You will also need about 1000kWh of power to charge these, as the battery and charger are inefficient.
You would really need a battery bank capable of at least lasting 3 days or so at normal load, to be close to 'off grid'.
And then you will either need to connect to the grid if it's been dull for a few days, or a generator.
You will need at the minimum a battery pack that can be charged at a high enough power to absorb all the solar panel output.
This means for a 4kW array, 20kWh of batteries.

My Point entirely, this unit is constantly grid connected and automatically switches the grid back in once discharge rate is reached. There is no 'need' for autonomy so you can size the battery bank however you like, to budget constraints or to autonomy, there is nothing stopping you sizing it for weeks autonomy but it is not a need. Once the batteries are fully charged it will export to the grid so there is no loss of output or feed in tariff. Download the data sheet and have a look at it if you want to analyse it.

As to the cost i've already said it's not really financially motivated, some people just want to have a bit more independance and are prepared to pay a bit extra for it (so i'm told) without going to the extreme expense of purely off-grid.

Martyn1981

Energetic wrote: »

My Point entirely, this unit is constantly grid connected and automatically switches the grid back in once discharge rate is reached. There is no 'need' for autonomy so you can size the battery bank however you like, to budget constraints or to autonomy, there is nothing stopping you sizing it for weeks autonomy but it is not a need. Once the batteries are fully charged it will export to the grid so there is no loss of output or feed in tariff.

Hiya E, there's a couple of products here:

http://www.earthtechling.com/2012/02/japan-combines-solar-storage-to-beat-blackouts/2/

http://www.renewablesolutionsuk.com/home/grid-buddy-3

as described by you, to work with a grid connection. Half way house, best of both worlds.

Some time back Zeup made a 'gentle joke' about using a Prius battery, so I did some reading up, then read a lot of the discussions on hybrid forums.

Very surprised to read that the second Gen batteries are incredibly reliable. I'd assumed (silly me!) that these batts being constantly charged and discharged quite quickly would suffer more failures.

Again, not an off-grid solution, but an interesting approach to domestic PV where export is so high, but export income is so much lower.

One to watch!

Mart.

grahamc2003

rogerblack wrote: »

The above battery will store about 2kWh.
A total of 600kWh at 100% and 50% discharge before it likely needs replaced.
This is about 80 quids 'worth'.
Even if you have free infinite solar panels, you end up considerably more expensive than grid.
You will also need about 1000kWh of power to charge these, as the battery and charger are inefficient.
You would really need a battery bank capable of at least lasting 3 days or so at normal load, to be close to 'off grid'.
And then you will either need to connect to the grid if it's been dull for a few days, or a generator.
You will need at the minimum a battery pack that can be charged at a high enough power to absorb all the solar panel output.
This means for a 4kW array, 20kWh of batteries.

Yeah, it's very unlikely that storing energy at home from solar to be used at night will, in the forseeable future, be cost effective - seems we have agreement all round on that.

But there is a case which I posted on some time back for a system similar to that used in the Prius. The high voltage batteries in the Prius are very low capacity (1.3kWh), but are capable of very high charge and discharge rates. The low capacity (which incidentally only the mid 40% is ever used, a state of charge between 40% and 60%, giving an effective storage capacity of about 0.5kWh) is used over and over again - with the system charging and discharging depending on many factors in real time - i.e. it can, and does, switch from charge to discharge to charge in seconds. So the 0.5kWh of capacity is used and reused constantly, and not simply fully charged, then fully discharged later in the day, which is analogous to how many think a solar energy store would work.

The realtime storage of energy for a solar system, likely to mimic the Prius operation for most effectiveness, due to the high cost of storage capacity. The battery would be used as a short term store, when, for example, generation is say 2.5kW, and a washing machine is turned on. The control system would enable short term uses of stored energy to meet deficits during a washing machine cycle, where the load could and would vary from 0 to say 3.5kW asynchoronously over a 90 minute wash cycle. Storing solar during the minutes when the washing machine load is 0W, or 150W, and releasing energy to meet the times when the load is 3kW or 3.5kW. Even in a single wash cycle, assuming a half decent control system, you can see the batteries will be charged and depleted (within their allowable range) probably several times during the cycle.

I doubt even this optimisation of control would frequently make such a system cost effective - depends on many factors. It saves money when the household load is flipping each side of the current solar generation.

Forever_Forest

Energetic wrote: »

There are some devices on the market such as the Nedap Powerrouter that have the capability for modular battery packs to be added to the system. Rather than exporting during the day the batteries will charge giving you the use of them at night, upon reaching their optimum discharge level you will switch back to the grid.

These will get you pretty close to no electricity bills with your levels of consumption without the need for riduculous auxillary battery banks to cover 5 days of autonomy, best of both worlds.

They are a bit more expensive than a normal inverter and will also allow you to use your generated power during a grid outage unlike any other invterter.

PM me if you want.

Is this the product where you can add extra solar panels to it if you want?

Thanks

Fruit_and_Nut_Case

Forever_Forest wrote: »

Is this the product where you can add extra solar panels to it if you want?

Thanks

Energetic hasn't been around since May so I don't know whether you'll get an answer.