Storing solar AC energy
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tim_n
Dec 10, 2015, 6:48:35 AM12/10/15
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I've recently had a 3.99kw system fitted to my house with microinverters. This means traditional battery storage (ie connecting up a storage system the solar panel system side of the inverter) isn't practical.
Therefore, I *think* that with my emonPi monitoring system, I could potentially install a system that allows me to charge a large lithium-ion battery through an inverter with the excess and use it when needed.
The added advantage of such a smart system would be to store energy at peak times - I have Economy 7, therefore I could buy electricity at 6p a unit at night and dump it into storage and utilise it during the day. Fair enough I'll lose some in inefficiency through the inverter but could potentially save 6p.
The advantages of this mean that even during the long winter nights, my system should continue to save a fair bit of cash.
Assuming that a suitably large lithium ion battery can be found and the emonPi can do the job...
There's plenty of battery storage solutions around, but none that are AC related as far as I can see. If you know of any, feel free to point me in the right direction.
Therefore, I *think* that with my emonPi monitoring system, I could potentially install a system that allows me to charge a large lithium-ion battery through an inverter with the excess and use it when needed.
The added advantage of such a smart system would be to store energy at peak times - I have Economy 7, therefore I could buy electricity at 6p a unit at night and dump it into storage and utilise it during the day. Fair enough I'll lose some in inefficiency through the inverter but could potentially save 6p.
The advantages of this mean that even during the long winter nights, my system should continue to save a fair bit of cash.
Assuming that a suitably large lithium ion battery can be found and the emonPi can do the job...
There's plenty of battery storage solutions around, but none that are AC related as far as I can see. If you know of any, feel free to point me in the right direction.
Ken Boak
Dec 10, 2015, 6:55:24 AM12/10/15
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Tim,
Good idea.
We are working on something similar at Open Energy Monitor - an "Open Source Inverter" which is to allow electric bike Li Po batteries to be charged from small (250Wp) solar panels.
The e-bike batteries are only about £70 (720Wh) when bought in China. They are a standard module with standard connectors and with a bit of ingenuity - a modular "bank" can be designed with 3D printed parts.
Have just sent the first inverter power pcb off for production.
Ken
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Nick Johnson
Dec 10, 2015, 6:57:23 AM12/10/15
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Taking DC power from a solar panel, putting it through an inverter to turn it into AC, then through another converter to turn it back into DC, then through _another_ inverter to turn it back into AC when you need it, seems needlessly inefficient.
I don't know much about household solar, but it seems like it'd be a much better idea to change the DC solar side of your setup.
Ian Macdonald
Dec 10, 2015, 7:01:03 AM12/10/15
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Ken Boak
Dec 10, 2015, 7:07:03 AM12/10/15
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Nick,
Accepted dc to ac conversion (and back) will only be about 80% efficient - if done properly - and there is a lot of merit to do everything in low voltage dc.
Being able to "timeshift" electrical power is fundamental to balancing the grid - to allow greater use of renewables. If we had 10 million electric cars in the UK - the electricity supply industry would be a completely different ball-game - with individuals buying and selling power to the grid at times that suited them - all stored in EV batteries.
The "open inverter" project is to explore the direct use of dc for running or charging small appliances. With solar grants virtually dried up - no-one is going to buy a big fixed system, instead they may choose to invest in asmall 250W panel - that they can take with them, should they move.
The power stage of the inverter can also be used to boost dc voltages up for battery charging, or reduce them to provide a stable 5V, 12V 24V etc supply - for powering consumer goods, laptops etc.
Ken
Ken
Toby Catlin
Dec 10, 2015, 7:08:32 AM12/10/15
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Photonic induction did something like this for power backup. He uses lead acid batteries and charges them over night on economy 7
t
tim_n
Dec 10, 2015, 7:21:43 AM12/10/15
to London Hackspace, to...@korfball.com
Thanks Toby, that's exactly the sort of thing I'm interested in
Ian Macdonald
Dec 10, 2015, 7:22:01 AM12/10/15
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@Ken,
Yep, the timeshift is the main advantage and allows the smoothing of
demand across the grid, if every home or at least sub station could
store enough electricity for 5-10 minute surges at peak times(kettle
at half-time being the classic) then the need for Short Term Operating
Reserve is reduced. Though the conversion is inefficient at face
value the reduction in the need for STOR which is a much higher cost
per kWh should reduce generating cost, which *could* then be passed on
to consumers.
Some hope, but there you go.
Cheers
Ian
Yep, the timeshift is the main advantage and allows the smoothing of
demand across the grid, if every home or at least sub station could
store enough electricity for 5-10 minute surges at peak times(kettle
at half-time being the classic) then the need for Short Term Operating
Reserve is reduced. Though the conversion is inefficient at face
value the reduction in the need for STOR which is a much higher cost
per kWh should reduce generating cost, which *could* then be passed on
to consumers.
Some hope, but there you go.
Cheers
Ian
tim_n
Dec 10, 2015, 7:36:54 AM12/10/15
to London Hackspace
Cheers Ken,
I'm very happy with my emonPi from Open Energy Monitor. Didn't realise you (as in OEM) had a presence here.
I'd be interested in the PCB and how easy it'd be to get an E7 storage system up and running. I'll confess, I'm less interested in a powered bike at present but am thinking battery storage to power a car - I looked at getting an e-bike, but the costs were such (and the stealability) put me off. I have an old 2nd hand motorbike which is fairly efficient instead.
I'm very happy with my emonPi from Open Energy Monitor. Didn't realise you (as in OEM) had a presence here.
I'd be interested in the PCB and how easy it'd be to get an E7 storage system up and running. I'll confess, I'm less interested in a powered bike at present but am thinking battery storage to power a car - I looked at getting an e-bike, but the costs were such (and the stealability) put me off. I have an old 2nd hand motorbike which is fairly efficient instead.
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