# Forum Home Renovation Solar Electrical Systems  Storing excess power query? Theoretical ??

## Moondog55

So we are getting lots of estimates and quotes to finalise finance for the last work on the house, all are [ except for Red Energy] within the same ball park and we are wondering now about the most cost effective way to heat the house in winter. Summer cooling is OK as the most power would be produced on those hot sunny days where the panels would be productive and the panel shading replicates the current use of roof-top shade sails.
The winter is when our power usages spikes as the reverse cycle system isn't as warm as Cecile likes for comfort and all.
I have been thinking about the old fashioned heatbank storage units that were used in bygone days of cheap off-peak power and wondering if something similar might be a good way of storing excess production rather than returning it to the grid at a low cost.
I am about to start searching for heat storage options. I know of a lot of ways to do it but they are all on the larger size and involve hot water from wetback fireboxes

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## commodorenut

I know you're not on a slab, but for thermal energy, you could get creative with hydronic panels, black tubing on the roof, and insulated tanks.
A mate of mine is off-grid, and they have a network of pipes through the slab (they built the house to suit the location). 
Once primed, it doesn't take much to pump the water up from the tanks (in the garage area under the house) to the roof & back, and a 2nd pump circulates the water through the slab.  
Their plan was to supplement the solar heat with a wetback combustion stove, but after 3 winters they still haven't had to use it.  
The water does cool off over the course of an evening - but it's very slow, as the slab holds a lot of the heat too - but it's noticeable when you get up in the morning that the slab is cooler. 
Perhaps you could do a similar thing with an insulated 44-gallon drum (or several), a couple of small water pumps, and some hydronic panels or even liquid to air radiators with fans in the required rooms in house? 
The best part about it is that by turning off the roof circulation pump, it doesn't add heat in summer.

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## chrisp

> I have been thinking about the old fashioned heatbank storage units that were used in bygone days of cheap off-peak power and wondering if something similar might be a good way of storing excess production rather than returning it to the grid at a low cost.

  It’s an interesting idea so I thought that I’d do some ‘back of an envelope calculations to get so*me* idea of practicality. 
Assuming you used a 200lt drum (thank you to FalconNut for that idea!), and we assume a 50 degree temperature elevation, 200lt of water could store: 
200 kg x 4186 J/kg/degree C x 50 degrees C = 41.86 MJ = 11.6 kWh 
Using https://www.lgenergy.com.au/calculat...elong-vic/3220 , for Geelong in winter, a 1 kW PV system will produce 45 kWh in the month of Jun and 52 kWh in July, which averages about 48 kWh per month. 
If you installed a 5 kW PV system, it’ll produce five time that figure - or about 240 kWh per month, or about 8 kWh per day. 
Therefore, the 200 lt drum could store all your PV production in winter! 
You’d have to somehow set it up so that it heats the water at the same rate that the PV system produces energy (so that you aren’t importing and negating the benefits). 
A thought - if you also use a heat pump hot water system, you could improve the performance by a factor of (about) four - and heat about 3 drums of hot water!

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## Bros

> If you installed a 5 kW PV system, it’ll produce five time that figure - or about 240 kWh per month, or about 8 kWh per day.

   Are those numbers correct? My 3 kw system can generate 25 Kwh on a good day Melbourne cant be all that bad.

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## chrisp

> Are those numbers correct? My 3 kw system can generate 25 Kwh on a good day Melbourne cant be all that bad.

  Have a look at the link provided (https://www.lgenergy.com.au/calculat...elong-vic/3220). I took the worst two months for the calculations!  :Smilie:

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## phild01

> Are those numbers correct? My 3 kw system can generate 25 Kwh on a good day Melbourne cant be all that bad.

  June-July!?

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## phild01

> Have a look at the link provided (https://www.lgenergy.com.au/calculat...elong-vic/3220).

  Just checked this for my area and the results are very close with what I am getting.  Mine faces north-west with very little overshadowing.

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## Moondog55

I know of a building in Harrietville that has/had a tank filled with 2 tonnes of Glaubers salts as the heat storage, but it ran a heat exchange tube set-up. 
I'm glad my idea isn't considered farfetched

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## Bros

> June-July!?

   February

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## phild01

That's a bit more than I got from a 4.9kW system.  Had some bad cloud cover during Feb.  In fact we seem to get a lot of bad cloud cover where I am, couple of days of super hot days are followed by many days of cloud cover.

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## Uncle Bob

I saw somewhere that someone has inverted a compressed air storage battery. Google that, it seems it could be a serious replacement for lead acid cells.

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## Bros

Now I can see why I have never visited Melbourne in Jun-Jul. 
I didn't think it was that bad.

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## commodorenut

> I'm glad my idea isn't considered farfetched

   I think you're ahead of the pack, and ideas like this will become much more mainstream as energy prices continue to rise, and grids become even more overloaded with new developments and the continual decline of proper base-load generation.

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## Marc

So we invented a centralised energy production maximising it's efficiency and distribution only to allow this near perfect system to be sabotaged by a group of pretend environmentalist with socialist political agendas that spew hate and lies to advance their plan to push us back two centuries back to horse and cart. 
That compressor system is interesting if you think that there is value in living in isolation and dedicating most of your time to basic task that civilization had long ago made automatic and ready for a price.
How pathetic!
The picture at the top says it all. The idealisation of a dude that can not afford a haircut, dressed in a home made gown, reduced to spear his food for subsistence. Marvelous! Will most likely die at age 30 from smallpox or TB. All natural of course ... oh how good!  https://www.lowtechmagazine.com/2018...y-storage.html

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## Moondog55

Compressed air storage is great in huge quantities for regeneration of electrical power but that would involve extra steps that are not needed when what you want is heat.
You do prattle on Marc, the 1950s grid system that we have in place hasn't been updated [ as far as I am aware] since those idiots in government sold the business to pay the rent decades ago and has been falling apart ever since and it is holding back zero cost sum power. What we need is more solar/wind/wave generation and power holding close to where it is generated and more local distribution networks. What we have is a dinosaur that only works well when maintained and sharing huge infrastucture generation. It is old technology, 19th century technology and we can do much better: more efficient and more importantly cleaner, much cleaner
Although as a short term solution we could adapt some of these old coal fired monstrosities to get rid of most of our plastic waste that at the moment isn't being recycled.
So if Cecile and I need extra winter heat why not store it as heat.
It's getting the heat to where it is needed that is the problem, herself likes warm feet but I don't think there is enough thermal mass in the floor to justify another underfloor system.

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## John2b

> A thought - if you also use a heat pump hot water system, you could improve the performance by a factor of (about) four - and heat about 3 drums of hot water!

   Or use evacuated tube thermal collectors, which are about 3-4 times more efficient than PV to achieve the same result at lower cost without the complexity, noise and reliability issues of PV powered heat pump water heating.

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## Moondog55

The problem I see with the bulk heat storage is getting the heat from where it is stored to where it is needed.
I could see  us using a 350 watt under floor element [ the same size as the bathroom] under tiles over compressed cement sheet for example. But the heat doesn't last long once the power stops flowing though and we would probably need to add another couple of stumps and a bearer to take the extra weight.
I am still waiting on replies from the manufacturers of electric heat storage units to get back to me

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## Bros

You could migrate north for winter like thousands of other Victorian's do.

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## Moondog55

> You could migrate north for winter like thousands of other Victorian's do.

  No snow in Qld and it's a long way to drive to go skiing.
The heating comfort is for Cecile, I just put on a jumper, but it is a real medical issue and needs to be addressed as cost effectively as possible

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## Bros

> The heating comfort is for Cecile,

   I thought you would have toughened her up by now with all your reno's. 
About 10 yrs ago I was talking to some caravanners from Melbourne in a CP in Karumba and they told me it is cheaper to migrate north for the winter than pay the heating costs in Melbourne.

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## Moondog55

Well that's bit difficult as it's far too far to commute to work each day. 
Fuel from Geelong to FNQ at $1:75 a litre and 16kpl? 3000k divided by 16 multiplied by fuel cost? $300 sounds about right; so spending $600- to avoid $600- in heating costs

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## Bros

> Well that's bit difficult as it's far too far to commute to work each day.

   Time to retire.

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## Moondog55

To the snow fields? I'd be going on my own, besides we both hate Queensland

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## Bros

> besides we both hate Queensland

  I wish you could spread that around so the caravan parks and free camps are left to us as there are thousands who differ. 
I only like Melbourne when it is fine and warm to hot.

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## Moondog55

Just had a wild left field idea.
Remove the under floor insulation and put down 100mm coolroom panels or foam on the ground, put the electrical heating coil over that and then a full cover of water, in bottles, or bladders and box the whole thing in as tightly as possible, the deformation temperature for PET is 70C but if the thermostat was set to 65C that would be a lot of heat stored and good way of keeping a thousand or so bottles from landfill

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## Cecile

> Just had a wild left field idea.
> Remove the under floor insulation and put down 100mm coolroom panels or foam on the ground, put the electrical heating coil over that and then a full cover of water, in bottles, or bladders and box the whole thing in as tightly as possible, the deformation temperature for PET is 70C but if the thermostat was set to 65C that would be a lot of heat stored and good way of keeping a thousand or so bottles from landfill

   :Shock:  UHHHHHH

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## Marc

> You do prattle on Marc, the 1950s grid system that we have in place hasn't been updated [ as far as I am aware] since those idiots in government sold the business to pay the rent decades ago and has been falling apart ever since and it is holding back zero cost sum power.   *This nonsense is precisely what allows the watermelons to advance their destructive talk. Before accusing others of empty talk, look at your own nonsense. What has poles and wires to do with production of energy? Answer nothing. Actually, a lot if you want to produce energy via wind in remote areas and need to bring it back thousands of miles, not much if you have a centralised coal fired production near where the people live.*  
> What we need is more solar/wind/wave generation and power holding close to where it is generated and more local distribution networks. What we have is a dinosaur that only works well when maintained and sharing huge infrastucture generation. It is old technology, 19th century technology and we can do much better: more efficient and more importantly cleaner, much cleaner.  *More nonsense, what you need in the Socialist Republic of Victoria is a conservative government that demolishes all those idiotic wind turbines and builds a few modern coal fired power plants that are reliable and work 24 hours for cheap. Define "dirty" please. i consider the building of wind turbines polluting to the extreme if you consider all the areas of production. Coal fired produces CO2. That is not "dirty" that is a natural gas essential for life. The minuscule proportion of anthropogenic CO2 makes no difference to temperatures and never will. It is a red herring to redistribute funds and shift power.* 
> Although as a short term solution we could adapt some of these old coal fired monstrosities to get rid of most of our plastic waste that at the moment isn't being recycled.
> So if Cecile and I need extra winter heat why not store it as heat.
> It's getting the heat to where it is needed that is the problem, herself likes warm feet but I don't think there is enough thermal mass in the floor to justify another underfloor system.  *That is so typical to mix the "we need clean energy production" alluding to CO2 being pollution when it is not, and plastic pollution or any other real pollution. I suggest you stick to what you know and stop advancing watermelons agenda. Their agenda is not and never was what you believe to be good and proper. Your efforts are worthy of a better cause.*

    ...

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## Moondog55

You must have shares in coal power Marc. The future is in decentralised power generation and storage not in an old and dirty technology but I am happy for you to believe in what you believe in so long as you stop belittling those who have an opposing point of view and shares in the future.

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## Marc

Decentralised power generation like large wind farms right? Or perhaps you advocate for wind generators in parks and nursing homes?  
The future is what we make it. The left is aware that an impoverished and divided nation is easier to led down the left side of the garden path ... than a prosperous one.  
If you need an example of your future just look around your socialist republic and tell me you wish that onto all of us.  
If you had replaced the ageing coal fired with new more efficient one, your power bill would be peenuts and you wouldn't need to build a silly contraption to make bills less of a shock. 
Power should be plentiful and dirt cheap and such can not be achieved with the current technology in so called renewables. And I say so called because there is nothing renewable in the component of windmills for example and their rare earth magnets and a myriad of other not-for-a-moment renewables. 
Are they going to bury the old windmills in your backyard when they become obsolete in 20 years?  
The whole concept is nonsensical and emotional speech like "the future" and "decentralisation" and "dirty" and "our kids" is just that, nonsense appealing to emotions.  
There is only one reality
a) CO2 in the MINUSCULE amount we contribute to the atmosphere is completely irrelevant to temperatures.
b) Alternative ways to create energy are way more expensive, inefficient and not dependable for domestic use. They are a waste of space for industry. Your tooted battery would feed an aluminium smelter for an hour.  
It is easy to fall in the trap of "being progressive" yet the real facts are there for whoever wants to see it, rather than spreading misinformation willingly or in ignorance. 
The green wave is nothing but a disguised communist agenda nostalgic of their totalitarian power of the past. That is not the future. That is the real dinosaur in the room! 
The future is not with those who want to send countries backwards to a pastoral existence. The future is not with a mob that declares that "The worst that can happen to human kind is that we find a cheap source of energy" 
There is malice, hate and misinformation in all political confessions, there is not one good and the other evil. True, yet there is such thing as the less of two evils and also the creation of false causes to advance an agenda that is only interested in totalitarian power. 
CO2 is a natural essential gas that in the current proportions in the atmosphere is of no consequence to climate or our way of life. To keep on banging on otherwise shows either ignorance or an alternative agenda. .  
But like you said ... you can believe in whatever you want, santa claus, the yeti, or the lizard men. The problem starts when you begin advocating their cause, then you must listen to the replies your nonsense attracts. Nothing personal just stop repeating untruth and advancing other peoples agenda. You will not benefit from their cause.

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## Moondog55

I think you are confused there Marc, I'm not running an Aluminium smelter in my back yard, I never said I was and I don't intend to.
Neither am I a Communist.

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## John2b

> Summer cooling is OK as the most power would be produced on those hot sunny days where the panels would be productive and the panel shading replicates the current use of roof-top shade sails.
> The winter is when our power usages spikes as the reverse cycle system isn't as warm as Cecile likes for comfort and all.

   Interestingly on cloudy days in winter when you really need the power it doesn't much matter which way the PV panels face as on cloudy days the solar insolation is diffuse. Using PV panels for shading the roof from late afternoon sun will still produce useful electricity on cloudy winter days. I've been buying 10 year old Sharp panels for about $40 each (25 cents per watt) from people upgrading to bigger systems and the panels still meet new specification for output - so much for panels only lasting a few years! The roof under the shade of the PV panels measures 20 degrees cooler than the roof in full sun on hot days.

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