Using the immersion with your solar panels?

selfbuildache

Hi,
I posted another thread
http://www.boards.ie/vbulletin/showthread.php?t=2056096542
wondering about back boiler use with solars but didn't get many replies so I'm basically looking for more opinions by asking a different question -

If any of you supplement your solar panels with the immersion, do you have to use it much. i.e. would you notice its use on the electricity bills during the winter?
(We're hoping not to have to get a back boiler with a stove.)

quentingargan

Solar panels will only realistically provide your hot water during the summer. We have 80 tubes on a 300L cylinder and this keeps us going pretty much for 8 months of the year, but that is about the limit.

In the winter, normally your heating system will provide hot water at an economical cost, so there is synergy - the solar panels are providing what would otherwise be quite expensive hot water.

BUT. Your solar system will have a very well insulated cylinder, and some have two immersion slots, one at the bottom (for sterilisation reasons) and one in the centre which is for normal use. If you get a day/night meter and use the bottom one in winter, that would provide reasonably cheap hot water during the winter time...

galwaytt

I have a 1000L buffer, and no immersion's. Immersion's are a poor method of heating anything other than a 'flash' requirement imho.

I use solar + LPG.

quentingargan

galwaytt wrote: »

Immersion's are a poor method of heating anything other than a 'flash' requirement imho.

I use solar + LPG.

There are situations in which they work very well, provided they are only used off-peak. For example, many passive houses use a combination of solar and electricity to heat water because there is no other economical heat source.

As more wind is incorporated onto the grid, there will be need for more "demand side management" - electric cars, water heating, farmers freezing ice for bulk tanks etc., all help. Quite often the wholesale price for electricity at night falls to 2.5c. The wholesale price between 5.00pm and 7.00pm can peak at ten times that price. Smart metering will (hopefully) pass on some of this pricing to the consumer.

Times when solar panels aren't working often coincide with high wind speeds, and curtailment of wind farm output. An immersion coming on at 2.00am and running until 5.00am may become a more popular option in the future.

selfbuildache

Thanks for replies.
Quentin, we're going with a stove with back boiler as we too are not going to have central heating to help with the heating of the water and while I recognize what you're saying, I'm getting beaten down by the Irish (I'm told) mentality of getting as much use out of a stove as you can...

quentingargan

selfbuildache wrote: »

Thanks for replies.
Quentin, we're going with a stove with back boiler as we too are not going to have central heating to help with the heating of the water and while I recognize what you're saying, I'm getting beaten down by the Irish (I'm told) mentality of getting as much use out of a stove as you can...

Cheers. We get as much out of our stove as we can because we can't run an immersion on our wind turbine. But if it was a choice of getting a box of logs and lighting the fire for a few showers on a cloudy day, or hitting the immersion off peak, I'd probably get lazy. Immersion for 2 hours off peak is about 48c:)

championc

To hijack the thread somewhat but have you any idea as to which is cheaper between using electricity and an immersion, the return of a Central Heating Circuit or gas in a Combi Boiler ?

I have a Solar Tube system with 180L buffer and have a second coil (currently unused) in it, but like you confirm Quentin, you'll only get solar heat for about 8 months. The combi can heat the cold water but I just wonder if the immersion or CH Return methods would work out cheaper ?

quentingargan

championc wrote: »

To hijack the thread somewhat but have you any idea as to which is cheaper between using electricity and an immersion, the return of a Central Heating Circuit or gas in a Combi Boiler ?

I have a Solar Tube system with 180L buffer and have a second coil (currently unused) in it, but like you confirm Quentin, you'll only get solar heat for about 8 months. The combi can heat the cold water but I just wonder if the immersion or CH Return methods would work out cheaper ?

SEAI has fuel cost comparisons here but there are other factors such as boiler efficiency, and in relation to using an immersion overnight, the heat loss in the cylinder between 8.00am and the time the hot water is used.

My hunch is CH return when the heating is running. The inefficiency of the boiler is largely taken up in that you are heating the system already, but I don't think there is one answer to this... Q

selfbuildache

Quentin, I'm hijacking my own thread here but my longterm plan is also for a windturbine - why can you not run your immersion off it?? That was a big reason why I wasn't originally so set against the immersion - I thought I'd have my own electricity anyway!!

quentingargan

selfbuildache wrote: »

Quentin, I'm hijacking my own thread here but my longterm plan is also for a windturbine - why can you not run your immersion off it?? That was a big reason why I wasn't originally so set against the immersion - I thought I'd have my own electricity anyway!!

Our own house runs on a 2.5kw turbine and we use the surplus energy (when the batteries are full) to heat water. I've been designing another domestic wind turbine over the last 18 months or so, and when we set out initially, we had just this in mind - putting into the grid what was needed by the household, and using the rest to heat water. Another company brought out a gizmo which does just that for their solar PV systems. All that was at a time when, if you asked nicely, the ESB might allow you to "spill" your surplus to the grid - for free.

Then the Minister brought in a feed in tariff which amounted to 19c for every KwHr that was exported, and suddenly it made sense to export your surplus power. So why would you use your wind energy to produce heat worth about 8c per Kw Hr, when you can sell the same electricity for 19c?

The other argument was that running a turbine directly to an immersion heater cuts out all the cost of inverters and complex electronics. However, a grid tie inverter gradually ramps up the power taken from the turbine as the speed increases - the pull of the rotor is gradually increased so that it is almost free-wheeling at low speeds, and gradually the drag increases as the speed increases. This allows the blades to work more efficiently. So grid tie inverters not only provide power at a voltage and frequency matched to the grid - they also optimise the output of the turbine. If you just connect an immersion permanetly the turbine will never get started, so you need some sort of electronics whether you like it or not...

If you are seriously thinking of getting a wind turbine, then if you use this to heat your water at a time when it could be exporting to the grid, it will be the most expensive hot water possible - short of burning brandy!:eek:

selfbuildache

Wow. We're a long way off getting a wind turbine but it was always in the plans. But obviously I've a lot to learn between now and then...! Cheers!

galwaytt

...don't forget that, with Night Rate, if you DON'T have a big load to run, it's a waste of money.

More fees, to install.
Higher per bill rental/standing charges
Higher off peak unit cost for electricity used, as well.

For example, on the ESB website it says not to run appliances unattended, for safety reasons.

Then they extol the virtues of cheaper night rate energy.

Talk about Left Hand / Right Hand.......:rolleyes:

Me, I'd have removed the Night Rate except for one thing: they want €180 to REMOVE it !! :mad:

championc

I think Night Rate meters are really best suited for people with Electricity Storage Heating.

quentingargan

As an increasing percentage of our electricity comes from wind, demand side management is going to be almost enforced by pricing regimes. In the next few years, smart meters will have multiple tariffs, and we will all have to work around the range of prices available.

At present, daytime wholesale prices sometimes peak at 25c per kw hr between 5pm and 7pm, while night wholesale prices are just 2.5c. It makes sense to encourage people to move their consumption with smart meters, and low cost off-peak electricity will be the good news. Sorry for all those with electric cookers who want to put on the dinner at 5.00pm. That'll cost yer!

galwaytt

quentingargan wrote: »

As an increasing percentage of our electricity comes from wind, demand side management is going to be almost enforced by pricing regimes. In the next few years, smart meters will have multiple tariffs, and we will all have to work around the range of prices available.

Whilst that's no doubt true, if wind cannot meet our full demand (which it logically can't), then having everybody with a smartmeter 'electing' to use wind sourced power - and having that demand exceed wind power supply, means it's all for nought.

In other words, who's going to not 'tick' the cheaper unit box, on the meter ? If the whole country did it, it would be farcical. Mind you, then we could even the scales a bit, by putting a 'carbon tax' on air-sourced electricity for all those times it can't meet the 'selected' demand !!

gizmo555

galwaytt wrote: »

Whilst that's no doubt true, if wind cannot meet our full demand (which it logically can't), then having everybody with a smartmeter 'electing' to use wind sourced power - and having that demand exceed wind power supply, means it's all for nought.

In other words, who's going to not 'tick' the cheaper unit box, on the meter ? If the whole country did it, it would be farcical. Mind you, then we could even the scales a bit, by putting a 'carbon tax' on air-sourced electricity for all those times it can't meet the 'selected' demand !!

The point of using smart meters to differentially price units by time of day is not to increase the use of wind power, but to even out demand over the 24 hours of the day.

This can help to reduce the amount of polluting base-load generating capacity needed.

It's a double edged sword though - taken to its logical conclusion, it could mean vastly increased rates for peak periods like 5pm to 7pm. I can't find a link, but I do remember reading about a pilot program to install smart meters in homes somewhere in the US, with unit rates changing by the hour over the course of the day. At the end of the trial period, almost all the home owners opted to have the standard meter back as the smart meter tariff actually ended up costing them more.