Solar panels and battery storage

[GadgetMan]

There is a tariff that changes per hour, and give you 24 hours notice of what it will be. Apparently there are times when it pays you to take electricity. I think it works best if you have batteries and/or a car as presumably its expensive at peak Tea Time.

By the way, here is the deal on the “Miele”
If you have a hot water connection, choose the SolarSave programme (see “Installation” chapter, “Water in- let” section). The wash water will not be heated up during this programme
Quite simple, but effective. So you are only paying for the sloshing around of the water.

Washing machines used to have Hot water input, so perhaps we will go back to that sometime.

[Alley_Cat]

@GadgetMan

So if it were “smart”, how might that work? I suppose it could pause itself when you are taking power from the grid, but then you would need an override otherwise it might take say a day to wash, with most time re-heating the water. No doubt far more cleverer people can solve this than I.

These things may be available/feasible but unless a machine could monitor and adapt to the relative %age of power from solar vs grid there might need to be some separate smart device (or the machine itself) communicating with the internet to identify current weather conditions and likely conditions in subsequent few hours.

Assuming heating water is the main peak usage, I’d imagine far more ‘eco programmes’ in the future running at lower temps.

The problem with eco programmes is they seem to take ages and probably don’t work as well (dishwasher anyway). With school age kids we seem to have the WM on 2-3x daily, admittedly often on short programmes just to refresh slightly dirty clothes. I often run small loads to clean sports clothing, 20-30 mins max at low temps as it’s often just to freshen them up. Syntehtics dry well outdoors, but I really prefer drying cottons in a machine as they come out far softer - should probably dry on line then tumble dry with a damp tea towel or similar to soften the fibres.

[Alley_Cat]

Yes, I can still remember washing machines with hot water inputs - I think the logic with cold feeds only was that the ‘hot’ pipe was often quite long and full of cold water which didn’t really help, but in this day and age I’d be surprised if incoming cold ‘hot’ couldn’t be diverted to a cold reservoir (or drain) until it reached a useful temp - you’d use more water but less energy.

[Alley_Cat]

@Ardbeg10y

It’s all peanuts compared to heat the house in wintertime though.

That’s the big one really.

We are currently reliant on multifuel solid fuel burners and electric heating (long story), but I’m actually not sure if we had gas heating it would be all that much cheaper - the novelty of topping up stoves every 1-2 hours does wear off however.

[GadgetMan]

Good point, there is always that 30 seconds wait until the water gets hot. I tend to put that water in a jug and use it on plants - but not with this weeks rain.

I suppose to use your free hot water, you would have to run the hot tap first in the kitchen for a bit to get the benefit. Typically my water is 55-60 degrees in the tank, so I suppose some up front cold water wouldn’t be an issue on clothes, but might be too cool for a dish washer.

[Alley_Cat]

Yes, I think it would just be logical for a modern device to monitor incoming ‘hot water’ temp and either divert to a ‘cold reservoir’ to mix with ‘too hot’ or for rinse, but I can’t see it wouldn’t be feasible not to use hot once it reached appropriate temp - again I’m sure there could be algorithms to ensure the ‘mix’ produced the desired temp.

[ChrisSU]

I reckon a fair amount of the energy used by a washing machine to heat water goes into maintaining the required temperature over the duration of the wash cycle. Given that the claimed energy efficiency of a modern machine will only be achieved if you are using the lowest temerature settings of 30 or 40 degrees, there can’t be much advantage in pulling 60 degree water through a pipe (which will be as far as some of it will ever get). Cold water fill makes much more sense to me.

[GadgetMan]

Yes it does seem that the heating of water is the Devil. In my case, my water is heated free for most of the year, so if I pull in 60 degree water into a 30 degree wash, then it should never need to reheat. I guess there is a danger that you wouldn’t want it that hot for some fabrics, but if it’s the Miele method, you would be purposely setting the “SolarSave” option to do that. If your hot water isn’t free, then a low temperature wash makes sense.

There may be something “smart” you would do here also. Presumably a 30 degree wash has to slosh around a lot longer than a 60 degree wash, so the “smart” feature might adjust that according to the temperature.

I’m thinking you have both Hot and Cold inlets, then:

• SolarSave settings: uses whatever temperature your hot is
• All other settings: fill with hot, then switch to cold if the temperature goes beyond the wash setting, then the only heating you are doing is topping up

[linesrg]

@CautiousLip

I’ll have a go at answering your question as I have reasonable experience of Solar PV, Solar hot water, a GSHP, a battery, diverter and EV complete with charger.

You need to look at everything your planning to do e.g. you mention changing your gas boiler and getting an EV and treat the whole thing holistically rather than piece meal.

Almost everybody worth listening to should start by telling you your first port of call is to look towards the insulation levels of your property. It’s a bit like Location, Location, Location in the property world, in this case it is insulation, insulation, insulation.

You don’t say how old your property is or whether you’ve pointed a thermal imaging camera at it in winter to see where heat is escaping be it through poorly insulated parts or as a result of unwanted air movement.

Solar PV - brilliant in summer and utterly useless in winter. My 12kW array produced 46kWh in the whole month of December…

Solar hot water - don’t bother

Solar diverter e.g. eddi or similar - definitely worthwhile. Combine with the likes of a Meixergy hot water tank system.

Battery - OK so the Tesla Powerwall 2 is well known and represents ‘reasonable’ value for money BUT is not very user friendly. I would recommend you look at other systems such as can use piggy bankable Pylontech battery systems.

Inverters - yes they can be noisy but then you wouldn’t have it your living room would you??? Depending on your roof orientation you mighty want to look at such as Solaredge c/w individual optimisers on each panel if spread across more then one roof.

How much solar PV? This depends on whether you want to do your bit for the planet and also on what your local DNO will allow. If you only have a single phase supply then, on paper you are limited to exporting 16A per phase however most DNO’s will allow you to exceed this provided there is some form of limitation device in play.

In my case the DNO allows me to export a maximum of 7.4kW or circa 30A.

Depending on how much battery you want to install you can charge these using solar or cheap rate electricity and then export it at peak times. Octopus’s Agile account allows this but isn’t perfect. More tariff’s will start to appear in time as well as more geared to EV owners.

Heat pump - most people are going to end up with air source jobs unless they have sufficient ground in which to lay ground loops. You presumably have a wet heating system currently presumably using radiators? Your heat pump is, ideally, going to be putting water out at 40°C with a 30°C return so the standard radiator is only outputting 20% of its rated output so you will need to upgrade radiators accordingly.

Such as Stelrad do triple panel jobs which are a direct replacement fit as the extra panel is just fitted to the non wall side so the wall fixings and pipe connections are in the same place.

Hot water - do not rely on the heat pump alone for this. Yes they can do it but off you are a family of four and its winter you simply can’t heat the house and the hot water at the same time. You need something like the Mixergy hot water tank system and integrate it with the heat pumps it is already able to work with.

That’s probably enough for now???

Feel free to message me if you need any more advice/ thoughts.

Regards

Richard

[GadgetMan]

Very helpful reply, I’ll take a look at some of those tips, thanks. A quick look at the battery back system suggests a 2.4KWh system for under £1k - seems too good to be true, but I probably missing something and will have a read again when I am more awake.

@linesrg

My 12kW array produced 46kWh in the whole month of December

This was interesting, as I looked up my 5kW array, and last Dec it produced 67.8KWh, and 90.2 in 2019. My Diverter gave me Hot Water most of Winter surprisingly. I’m based in the NWest, so I’m guessing you are further North with really bad winters?

[linesrg]

Yes - deepest Aberdeenshire. The bulk of the panels are on a portal frame roof with only a 15° incline so the snow sticks around a while…

My main point was that you don’t get a great deal out in comparison with summer.

The overall efficiency of the underlying property is also a significant factor of course.

Regards

Richard

[Pete_the_painter]

A word of warning, we installed 27 panels a few months ago with the hope of reducing our eye watering quarterly power bill. We were shocked to get our latest bill that was more than for the same period last year. We now have asked for a detailed account as while we are in lockdown there are only 2 of us and I’ve always worked from home, for us not much has changed.

One of the biggest surprises was the lousy figure of a return to the supply of $46.00 and that since going solar our rate per kw has increased.

[GadgetMan]

@Pete_the_painter

We installed 27 panels a few months ago, our power bill was cut in half for the first billing period and we’re expecting it be be reduced further

Has something changed from your above previous post? Are your bills being based on estimates rather than actual usage possibly?

[Alley_Cat]

So poorer in winter, what kind of figures do you get in the summer spring/summer months?

[Pete_the_painter]

It seemed our first bill was a just a part bill this was the first full billing period since they (supplier) switched us over to their “solar” plan.

[GadgetMan]

Here is last years and this years. It pretty much matches what the installer calculated.

[Pete_the_painter]

We had an interesting call from our power supplier today they’re reduced our bill by about 40%. It seems someone hadn’t switched our plan/conditions over to allow for solar.

[Alley_Cat]

@GadgetMan

The answer is that is varies from what I have read. Yes the Inverter is noisy by design, and some say it effects SQ, some not. I have 3 year old Solar Panels, but do not get any loss of SQ that I can hear. Saying that, I find there is already a lot of noise pollution during the day anyway, so that may be why I can’t hear it. Typically I tend to listen intently at night, so Panels are off.

You will probably find that in dark wet days that you are hardly generating any electricity, so you will be drawing current from the grid most of the day. Your batteries may not cover more than a days usage, so this is when you start to get wise about getting the most when it is sunny. Use weather maps to determine washing days. Mow lawn and use Immersion for hot water when Sun is out. Watch the clouds and possibly delay putting the kettle on for a few minutes. Don’t put toaster and kettle on at the same time, etc

Here are my figures if it helps (I don’t have batteries though)
4.8 KW panels generate 4,600KWh pa (18 panels)
My annual usage went down from 2,900KWh to 1,800KWh
My gas usage also went down by >25% (If over generating I divert to Immersion and electric fire)

What area do those panels take up on a roof?

Even if feed in is poor getting 4,600 kWh of electricity might knock a 1/4-1/3 off my electric usage.

[GadgetMan]

The Roof Peaks stopped me getting more. I might have squeezed more on, but it does look balanced, and does everything I need. Thankfully there are no trees in the way to block light. Here is todays generation, which was a mostly sunny day.