Storage Heaters - Would charging them from a Solar System make sense?

blankscreen

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Hi Guys, I'll likely go for solar installation next year, those who already have one say to use on your washing maching, dishwasher while you have daylight.

It occurs, our washing machine takes about an hour but is only on about every 3 days, dishwasher 30 minutes, so to use that excess available energy would fitting storage heaters to be recharged during daylight make sense?

never had them so no idea how long they would need to charge for, or consumption.

Alan
 
How would you control the power drawn by the heater to make sure it only used the excess generated power? I've had an online monitor reading my PV power generated and power consumed since July, and it is apparent that the generation is nowhere near constant, and at this time of year the generation levels drop dramatically meaning you would need several stages of heating in small amounts to be matched to your excess generation power to stand any chance of using it efficiently. For example, today my 4kW array only managed a peak maximum output of 300 watts, and generated less than 1kWh for the day. Therefore it would not be at all suited for heating as you could not heat your home with such a low power level.

Out of the 3100 kWH generated by our array to date this calendar year we have used about 2500 units, so only exported around 600 units, most of which was during our fortnight holiday in the summer when we had several days of continuous high PV output when the house as unoccupied.

At my location in the Scottish Borders it seems like the sun switches off in November and comes back on in February. For three months the PV output drops right off, meaning for this three month period we only generate what we normally otherwise generate in a single month, and this is at a time when you would most need heating. So using PV for heating is simply not going to work, you'd be far better liking to see if you could use the excess for hot water or some other electrical load that will be present year round as your greatest export periods will be spring through to autumn.
 
How would you control the power drawn by the heater to make sure it only used the excess generated power? I've had an online monitor reading my PV power generated and power consumed since July, and it is apparent that the generation is nowhere near constant, and at this time of year the generation levels drop dramatically meaning you would need several stages of heating in small amounts to be matched to your excess generation power to stand any chance of using it efficiently. For example, today my 4kW array only managed a peak maximum output of 300 watts, and generated less than 1kWh for the day. Therefore it would not be at all suited for heating as you could not heat your home with such a low power level.

Out of the 3100 kWH generated by our array to date this calendar year we have used about 2500 units, so only exported around 600 units, most of which was during our fortnight holiday in the summer when we had several days of continuous high PV output when the house as unoccupied.

At my location in the Scottish Borders it seems like the sun switches off in November and comes back on in February. For three months the PV output drops right off, meaning for this three month period we only generate what we normally otherwise generate in a single month, and this is at a time when you would most need heating. So using PV for heating is simply not going to work, you'd be far better liking to see if you could use the excess for hot water or some other electrical load that will be present year round as your greatest export periods will be spring through to autumn.

Thanks Niel,
I am a the typical mad scientist typ :).

We are in Essex (Area 12) clear of any obstructions, the idea was effectively the substitution of white meter control to feed Solar power into one or two 1kwt heaters on their own circuit. I needed some informed comment (acheiving control aside) to see if it was viable.

As i understand it in good daylight times i'd get near 4kw for between 4 - 6 hours, a washing machine when heating up draws aroud a 2Kw for 15 minutes. So it seemed an obviousplan when no heavy duty units were being used to charge uo storage heaters from the unused solar power.

The ida is in i infancy, bu to sense when the Solar Panels are more than likely active, there is no hard output or indication from the kit, i buy a small stand alone solar panel normally used to trickle charge a car or boat battery, this is used to roughly confirm enough solar energy is available. a timer is used to limit the storage charging period as example 10am to 2pm, running washing machines etc restricted to between 2 - 4 pm, it would need some fettling and refining but thats the broad principal.

Given we don't use the washing machine or dishwasher every day, it seem prudent to use that spare caoacity for heating, and so reducing the gas bill. and we would only use the storage heaters to take the chill off at night in the dinning room and conservatory.

I was assured using Goverment charts a 4k system in my area would produce an average of around 2.5 Kw to per hour in winter as it works on converting daylight not sunlight into energy, but your figures do not seem to support anywhere near these claims.

what do you think?

Alan
 
My annual forecast for PV output based on my location/orientation was 3000-3500 kWh per year, and I'm right in the middle of these two figures this year. The sun is just up here and is struggling through some cloud low to the horizon, and the panels are not yet above 100w output. Within the hour there should be direct sun on the panels as the sun rises higher and clears the cloud so I'll see what happens. During sunny days at this time last year I managed around 7.5kWh on the best days, but these were few and far between!

So you may get some useful heat on some days, but the amount of useful heating you achieve is never going to be great, and you still have the issue of what to do in the many months when you don't want/need the extra heat. Using appliances during this period is one way, but as you say it only uses a fraction of the available energy if you don't have a daily need to use them. I've got two boys who both play outdoor sports, so the washing machine is going at least twice a day, plus the dishwasher too. We also are an all-electric home with ground-source heat pump supplying our heating and hot water, so making use of the available power is never a problem, we simply have to manage when to use appliances through the day to stagger the load to utilise the available PV power.

Regarding storage heaters, I've only had experience of the standard Creda units from my first house nearly 20 years ago, and they did not make a great job of storing heat - the rooms they fed were always way too hot in the morning just after they finished charging, and by early evening they had little output left (just as you wanted the heat in returning from work). So in this case where your charging period would be much closer to when you wanted the heat it might work providing you can get enough energy to keep the heater operating for more than an hour or two each day. Otherwise you might be better to simply use a panel heater for direct heating to warm up the house directly when the PV energy is available, even if this is not quite at the time you would normally need the heat.
 
Just to add, now that the sun has cleared the cloud my output has risen to just over 2kW with the panels in full sun. I'll post again later when the sun has reached it's peak to see how much further this increases.
 
My annual forecast for PV output based on my location/orientation was 3000-3500 kWh per year, and I'm right in the middle of these two figures this year. The sun is just up here and is struggling through some cloud low to the horizon, and the panels are not yet above 100w output. Within the hour there should be direct sun on the panels as the sun rises higher and clears the cloud so I'll see what happens. During sunny days at this time last year I managed around 7.5kWh on the best days, but these were few and far between!

So you may get some useful heat on some days, but the amount of useful heating you achieve is never going to be great, and you still have the issue of what to do in the many months when you don't want/need the extra heat. Using appliances during this period is one way, but as you say it only uses a fraction of the available energy if you don't have a daily need to use them. I've got two boys who both play outdoor sports, so the washing machine is going at least twice a day, plus the dishwasher too. We also are an all-electric home with ground-source heat pump supplying our heating and hot water, so making use of the available power is never a problem, we simply have to manage when to use appliances through the day to stagger the load to utilise the available PV power.

Regarding storage heaters, I've only had experience of the standard Creda units from my first house nearly 20 years ago, and they did not make a great job of storing heat - the rooms they fed were always way too hot in the morning just after they finished charging, and by early evening they had little output left (just as you wanted the heat in returning from work). So in this case where your charging period would be much closer to when you wanted the heat it might work providing you can get enough energy to keep the heater operating for more than an hour or two each day. Otherwise you might be better to simply use a panel heater for direct heating to warm up the house directly when the PV energy is available, even if this is not quite at the time you would normally need the heat.

Many Thanks,
tbh i have a built in resstance to any early experience of storage heaters because they needed accurate weathercasts or they pump out during a heat wave lol! But i was also out of date about my views on Solar Panels.

I think later storage heaters have better heat retention as well as regulation design, a bit like recent hot water storage tank insulation that keeps heat for what i think are astonishing legnths of times - just as the home owners switch to combi boilers - timing is everything i guess :).

Alan
,
 
It would be good of any who knows to post how long a storage heater needs to reach a useful or full charge.

Alan
 
After a sunny day my PV generation has now dropped right down as the sun is almost perpendicular to my roof and starting to dip down low towards the horizon. With my orientation I've had 3.5 hours of useful PV generation above 2kW, right now the array is outputting less than 100w. So my total OV generation today will finish at around 7.5 kWh, in line with what I achieved last December on sunny days.

Hopefully that helps identify what you might expect from your own installation if you choose to go ahead. There is a massive difference between sunny days in Winter compared to heavily overcast days, where my maximum instantaneous output can sometimes be as low as 150w leading to a total generation for the day as little as 0.2kWh! Being Scotland we certainly get more grey days than sunny at this time of year!!
 
Thanks Neil for all your time, really appreciated :).

In our case, above 2 Kw for 3.5 hours - if we dedicated it as i think we could do for 3 or 4 out of 7 days would go a fair way to recharge 2 x 1 Kw heaters.

Not saying earth shattering but over the Autum to Spring period i doubt we would loose out.

Alan
 
Just one other thing to add, in the whole of November there were only three days where my output gave more than 5kWh for the day, and 10 days of output under 1kWh. Today will be another decent day once the frost has burnt off the panels, but this will be the first day in over a month where there have been two consecutive days of good clear weather up here in the Scottish Borders.

Don't let my figures put you off, but I am trying to give some real world feedback on the variability of PV output which only becomes really visible once you have real-time monitoring in place to record this information for later analysis.
 
Just one other thing to add, in the whole of November there were only three days where my output gave more than 5kWh for the day, and 10 days of output under 1kWh. Today will be another decent day once the frost has burnt off the panels, but this will be the first day in over a month where there have been two consecutive days of good clear weather up here in the Scottish Borders.

Don't let my figures put you off, but I am trying to give some real world feedback on the variability of PV output which only becomes really visible once you have real-time monitoring in place to record this information for later analysis.
Much appreciated again Neil,

Sales reps assured me of 4kw for 4 hours of daylight as being a minimum, even if covered with snow (which istill doubt), but there is no way i could independently varify this with pratical experience before buying, by which time it woukd be to late.

Powering Storage heaters tbh for me are not a big deal, i try to maximise what i can get out of any item i buy and it firms oart if the pro's and Cons of decissions.

We have gas heating via a condensing boiler, with all electric cooking. one bright rep suggested fitting a tank for hot water using the tube type panels to heat it in addition to the 4kw . He was doing so well until i pointed out the washing machine and dish washer were cold fill only, and we had removed our bath some years ago to make a utility room, as we both prefer showering via a power shower. which is instant while saves on water charges so the only use for solar hot water was at the kitchen and 2 hand sinks.

i sell equipment for a living, but still felt gloriously evil watching the obvious deflation spread across his face ;).

Alan
 
lol! i suggested illuminating them at night from 12 v flood leds using car batts that are charged durung the day,

caused yje longest scratched chin moment in history ;).
 
I'm not sure if there are many people still following this, but I thought I'd add some more results from some real systems. I upload my data to a monitoring site with many others from the UK and around the world. Over the last week or two is has been mostly cloudy over most of the UK, and I've been looking at the output from the 465 members across the UK who are regularly uploading their info. On many overcast days there are less than 10 sites that achieve over 2kWh of generation, and more than half of these of have 8kW-10kW arrays, so significantly larger than most residential arrays. Around another 35 managed somewhere between 1-2kWh, and all rest (over 400 sites) generated under 1kWh. The figures also provide the peak instantaneous output for each day, and none achieved higher than 1.8kW, even with 8kW of panels in this case

So this reinforces the point that in winter you cannot rely on any really useful output to run heating-type loads regardless of where you are in the UK. Any sales person telling you otherwise is at best uninformed, and at worst just outright lying to try and close a sale.
 
I'm still watching the thread if just out of curiosity, even after i came close, i'm personally not going to install a system in the forseable future prefering to keep my capitol in my wallet.

20 years time i'll be oaying through the nose fir enegy, but then i'll flog the house abd get me an electric scooter, a flat in Spains Costa Del Sol - and a hot Danish house keeper ;).

Alan
 
I'm not sure if there are many people still following this, but I thought I'd add some more results from some real systems. I upload my data to a monitoring site with many others from the UK and around the world. Over the last week or two is has been mostly cloudy over most of the UK, and I've been looking at the output from the 465 members across the UK who are regularly uploading their info. On many overcast days there are less than 10 sites that achieve over 2kWh of generation, and more than half of these of have 8kW-10kW arrays, so significantly larger than most residential arrays. Around another 35 managed somewhere between 1-2kWh, and all rest (over 400 sites) generated under 1kWh. The figures also provide the peak instantaneous output for each day, and none achieved higher than 1.8kW, even with 8kW of panels in this case

So this reinforces the point that in winter you cannot rely on any really useful output to run heating-type loads regardless of where you are in the UK. Any sales person telling you otherwise is at best uninformed, and at worst just outright lying to try and close a sale.

Hi Neil, Yep PV is not really best designed for supplying heat full stop, however there is one case where it works and thats if you pair a very large system with a small load. So say putting a 50kW or even bigger say upto 250kW onto a farm house. We've got a couple of sites where we are doing just this and the forecasts are that we will reduce the site loads by 80% or so. However you will need a 3 phase supply and a large transformer to go with systems of that size. One thing that will change over time is that systems will get larger and excess production will be dumped into batteries , this should become a reality in the next 2 to 3 years once the new Tesla Gigafactory battery plant comes online around 2017.
 
@blankscreen rather than trying to dump the power into the heaters which you will be able to do a bit if they are charging through the day you would be better placed to dump the power into the water tank as hot water (its a pretty good way to store power). The heat for water is required pretty much through all the year where as heat for warmth is pretty much only really required in months where solar isn't producing much.

A good way of doing this is to use a diverter such as PV Water Heating, Solar Hot Water Switch and Controller Supplier in Lincolnshire, UK | immerSUN this has a CT clamp on the incoming supply and watches for when export is occurring and switches on the immersion heater in your water tank. This can soak up a lot of excess generation as it can be paired to a 3kW heater which will pretty much use all the power in the centre of the day. This sort of device has a very short payback period as your utilising power that you would have been given away for free and saving power to heat the water at 14p/kWh on electric or about 5p/kWhth for gas.

I note from your other posts that wondered about payback times a 4kW system at ÂŁ6k which is a mid range price should deliver a return of about ÂŁ750/yr if you don't use the power or upto ÂŁ1050 if you do so payback is 6 to 8 years dependent on your location and use patterns. Thats a 12 to 17% return, better than money in the bank!
 
Panels that generate when covered in snow! Next he'll be telling you that they work at night too :)

It is possible to get a little bit of output if you've got a very clear day and a thin layer of snow but in general they're talking out the posterior!
 
A
lol! i suggested illuminating them at night from 12 v flood leds using car batts that are charged durung the day,

caused yje longest scratched chin moment in history ;).

Actually that will work! Have a friend thats done this but... 1kw of energy into the flood light then panel is 15% efficient so only 150w comes out the back end... its a good way to burn 850w of electric!
 
@blankscreen @neilball best advice for heat is pair solar PV system for electric and a biomass boiler for heat that way you can benefit from Renewable Heat Incentive (feed in tariff for heat) if your on LPG or Oil its a no brainer the payback is better than PV
 
i'm personally not going to install a system in the forseable future prefering to keep my capitol in my wallet.

The best return on your money is almost certainly more insulation. And that is also quite probably the greenest solution too. Its all very well everyone generating relatively small amounts of PV derived electricity when the demand is not particularly high. Its better all round if people take measures to reduce consumption when demand is at a peak.

Peak demand in France is usually in December, Friday evenings around 18.00, during a really cold snap. One which is normally associated with freezing air coming in from the east. So, no sunlight, no wind power. Which means that 110GW of electricity must be generated in order to keep the lights on. So there must be 110GW of generating capacity. A lot of this won't be used at any other time, or at best the power stations will be running at a less that 100% capacity which has an associated drop in efficiency. So the electricity must be more expensive to pay for the maintenance of the "stand-by" capacity and/or the less efficient running of the power stations normally.

So, the truly "green" route isn't PV solar electricity, but taking steps to reduce consumption (and insulation allows you to do this without drop in comfort levels). And saves you money. And there is no risk of Governments deciding to unilaterally change the rules over PV, because they cost too much, etc etc.

Just my opinion, rant over.
 
Dont disagree that insulation is a great route to lower costs/use but its really only the best approach when your building from new or your construction of your building allows it. If you speak to any of the guys running things like green deal (UK's programme designed to increase home energy efficiency) they will tell you that a great number of the UK building stock is hard to treat and so costs quite a lot to apply insulation to. e.g. single skin brick properties of the back to back type where its almost impossible to insulate them without major disruption or massive cost.

Another oft missed point is that doing things like applying External Wall Insulation to older hard to treat properties could have profound effects on the look and feel of the UK's cities as swathes of properties become cement rendered rather than brick. Of course you can apply brick facades to EWI but a lot of those properties are council owned and they simply don't have enough money to do that sort of finish.

Fully agree that solar / wind need backup capacity on the grid but the future is not one of emitting CO2 burning up millions of years of stored fossil fuels (for a number of reasons). The future will be a combination solar, wind, gas, nuclear, waste to energy and storage and most importantly demand reduction.

Cant say I'm a massive fan of nuclear but it will have an important part to play in providing the baseload contribution, solar and wind in conjunction with storage will then be able to top up during the day peaks with the peak demand being filled by peaking gas plants. Storage will help to flatten out the peakiness of renewables, the other main area I see is distributed CHP (combined heat and power - gas generators that supply heat from the cooling jacket) these work really well for things like care homes where hot water demand is high.

In short the market will be a lot more complex than it is now but will use technologies that suit the situation and be much more distributed, large central power plants are a thing of the past (other than nuclear / waste to energy).

Oh and on PV cost you are behind the times While You Were Getting Worked Up Over Oil Prices, This Just Happened to Solar - Bloomberg Solar has beaten gas and coal in recent power auctions in the US, whilst this is in high sun areas e.g. Nevada this was also against gas at some of the cheapest prices in the world, this will spread to the rest of the world as PV prices continue to decline. In Italy and Spain solar plants are being built right now that don't have any subsidies and sell power into the open market competing against traditional generation.

Traditional generation can only get more expensive as they are mature technologies, with increasing emissions regulation costs and increasing fuel costs they will become more expensive. Solar on the other hand is dropping in cost by 20% for every doubling of installed base, its decreased by 70% in the last 3 years alone. With no fuel cost solars costs are fixed at build stage so the levelled cost of power production is very predictable and increasingly more cost effective over the long term than traditional power.

Rant over ;-)
 
To hopefully answer the original question .... We had a solar pv system fitted plus ImmerSun unit to feed into a thermal store two years ago and have found it works well, the input is extremely variable and winter input is understandably low but in Spring and Autumn there were a lot of cold but sunny days, giving a good input and we have a cold living room so are just installing a solar fed night storage heater (the ImmerSun is capable of feeding two channels) to take off the chill during these periods. It is a 1.7kw with input and output controls and is being fitted with an isolator switch so that it can be turned off during heat waves. I will add my findings to this thread to hopefully help anyone else wishing to try it out. It is not a cheap option but we did find a large percentage was being output to the grid during both seasons and we were having to heat the room by conventional means, which I object to.
 
Storage heater is now fitted and working. Immersun putting in very small amount - today 1.5kw in total, into a 1.7kw heater. Surprisingly the heater is warm and definitely took the chill off the room, which was the hope.
I should just point out that I am not using it to heat the thermal store as I fitted a separate solar thermal panel which is heating the water fully.
So, it does work. Hope that helps
 
To hopefully answer the original question .... We had a solar pv system fitted plus ImmerSun unit to feed into a thermal store two years ago and have found it works well, the input is extremely variable and winter input is understandably low but in Spring and Autumn there were a lot of cold but sunny days, giving a good input and we have a cold living room so are just installing a solar fed night storage heater (the ImmerSun is capable of feeding two channels) to take off the chill during these periods. It is a 1.7kw with input and output controls and is being fitted with an isolator switch so that it can be turned off during heat waves. I will add my findings to this thread to hopefully help anyone else wishing to try it out. It is not a cheap option but we did find a large percentage was being output to the grid during both seasons and we were having to heat the room by conventional means, which I object to.
thanks for this, i was courious as if viable it is an independent means of heating a conservatory and so a direct saving, not really turning it into a sauna but simply to keep the worst of the chill off.

perhaps an idea for keen gardiners with a polly tunnel?
 

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