Running a washing machine with solar panels

60camraman60

Hi All, I have just bought myself a new washing machine, (a blomberg although I don’t think the model makes a difference). We have solar panels on the roof and so I would obviously like to use the machine to its full potential. I knew with the old machine that I could use totally “Free” power if I was generating at least 600w for the 1hr 15min it took for the full cycle (40 deg. Wash). This new machine states things different. There are many programmes but the two I am interested in for comparison are. Cotton Eco at 40degrees which uses 0.63kWh and takes 3.5 hours and Fast Full Load at 30deg. which uses 0.4kWh and takes 25mins.
The question I suppose I am asking is taking into account the British weather where you may get bright sunshine for half an hour then it rains for the rest of the day would you be better using the fast load programme which gets in done quicker, just in case it starts raining, and how will that impact on whether I am using “Free” power for the whole cycle. Hope this makes sense.

chrisw

Your old machine was using 0.48kwh. Therefore if you had enough sun to run it before for 1hr 15 it should easily do the 25 minutes.

The rest is impossible to answer as it depends on the output of the solar panels over the 3.5 hour period.

60camraman60

Hi chrisw that's what I thought. The place I bought it from was extolling the virtues of it being really economical if I used mainly the cotton eco mode, but I didn't mention the solar panels which makes quite a bit of difference. There is the capability of overriding the temperature so it will do a fast load at 40 degree. It doesn't give me any readings for that but it will probably still be quite low. Thanks for the reply.

Living_proof

I have always been told that the kwh given for a wash was an average over the whole cycle and that the really high use is for heating the water and spinning.

Heedtheadvice

There you have it, the Living proof!

The main problem to using the 'free'power generated is matching the power being produced vs the power consumed at any particular time. On your small scale or on a more global scale it is the same issue i.e. matching supply and demand.

What the machine is quoting in 'eco' modes is the total energy used. (Measure in kWh) That may or may not match what your panels generate over a period. As you know that generation will vary depending upon solar conditions affecting the 'light' energy incident on the panels. It can be very high (in relative terms) during a sunny summer's day, very poor in a foggy winter day (and sod all at night!)
There will be many a day when you generate more energy than a wash will use.

HOWEVER the critical thing for you to run the machine for free is how much power at any moment you are generating vs the quantity of power being used by the machine. As Living proof posted that highest level of power will be during heating of the water quite often greater than 2kW for parts of the washing and finding cycles. This assumes that the machine is cold fill rather than hot fill. Most machines these days fill from the cold water feed only.

If you are not generating that 2kW+ from your panels at exactly the times that the machine needs that amount t of power then it must come from elsewhere. That is normally purchased from the grid -unless you have storage facilities (such as a battery backed system). That is one of the downsides of renewable generation where it does not exceed demand.

The good news is that there will be times when you generate sufficient (another assumption here that you have an efficient 4kW peak set of panels) energy to meet your instantaneous needs - mine reached over 2kW for an hour in bright sun the other day - so if that coincides with machine washing time, no problem; similarly even if you do not meet the heating cycle high peak demand that can be fairly short in duration and you may well be reducing bought in energy off the grid and also you get a FIT payment for your generation (I presume) irrespective of what your consumption is.

That storage problem is one that thousand of solar panel owners would like solved such as a cheap battery storage system. Currently still not really cost effective.

Best you probably can do is optimise your consumption by timing that consumption of power to match the timing of maximum (or at least sufficient) generation and reducing heating need by not using cold water and doing those cool washes you mention. A generation and consumption power monitor can help you do this.

So lots of ifs and buts there and a few assumptions too.....And that is without even considering your specific washing machine.

The relationship between power and energy is the power x time equal the energy, so consuming 0.75kW for two hours is 1.5kWh energy and that is what you pay for not the instantaneous power consumed. Short bursts of high power consumed are significant but only a small part of the story you have to consider for how long too. The above post on supply and demand applies to all demand such as kettles, toasters, microwaves, cookers, irons etc. and possibly most significantly water and space heaters and tumble driers that are high power for varying amounts of time.....And lower power consumers that may be switched on for long periods

60camraman60

Thanks Heed.
A very concise explanation. I don't think it will ever be possible to match generation and consumption. Even having a way of turning say a washing machine on and off based on energy generation obviously wont work, especially in the UK. Maybe it would in permanently sunny climates.
I agree with the storage. I am on the 2nd Highest FIT payments and would like to instal the storage batteries but at my age (57) I doubt that I will ever get my money back. The younger generation might, although their FIT payments are going down all the time. I think it will always be a case of pot luck especially at this time of year although in summer you may stand more of a chance especially if you can get the machine to wash in 25 minutes. You may just about stand a chance of getting that in the summer.

Norman_Castle

Living_proof wrote: »

I have always been told that the kwh given for a wash was an average over the whole cycle and that the really high use is for heating the water and spinning.

Water heating is about 2000 watts. When spinning its about 200-300 watts. Spin speed and longer spin times make very little difference to the electricity used.

lstar337

Norman_Castle wrote: »

Water heating is about 2000 watts. When spinning its about 200-300 watts. Spin speed and longer spin times make very little difference to the electricity used.

Yeah, just make sure it is good and bright out when you start the cycle. That way the panels will be at high output for the water heating part of the cycle. Everything else is going to be practically negligible on a modern machine.

Ours is A++ rated and it uses about 90% of its energy in the first 5 minutes of the cycle.

Living_proof

I have had my panels for almost three years and have a 4kw split half east, half west in theory giving me generation throughout the day. I work at home and can therefore choose to put on the washing machine when the forecast is good and if I plan it in advance I can then line-dry the clothes, maybe just finishing them off in the tumble drier. At this time of year it can be difficult to find a day which will be suitable to do both, but my electricity bills have consistently reduced since having the panels. Also an income in excess of £500 pa which covers my hairdressing bills! I will add a battery to the system when the costs have reduced.