So now I have a solar PV system how do I make the most of it???
Comments
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One or two thoughts.
The electricity is produced in a bell curve, the size of the bell getting bigger until it peaks mid-summerish. ATM its quite small (low angle of sun and low length of day). The amount of leccy being produced at the peak of the day may be 3x as much in strong, summer sunshine as it is now, and the system may well produce 8x as much then. So using your leccy productively in the summer will be harder than it is now
When days are really dull in winter generation will probably be accounted for largely by base load (central heating pump, fridge, freezer etc, sensors, displays)
Many appliances dont use leccy evenly (dishwasher, washing machine, breadmaker, electric oven, microwave on low settings) or use high kW: eg kettle say 3kW, showers 8-10 kW.
Constant (ish) appliances seem to be: lighting, tv, computers, monitors, set top box, electric hobs, toaster, tumble dryer, hoover, microwave on full (which uses about 1.5x rated output) Not sure about slow cookers, iron.
As you can see it'll be a juggling act to keep varying use in line with varying production. I find it helps to keep a monitor in the kitchen/utility (where most usage is started) and (keeping in mind Cardews valid point about running appliances efficiently) try to manually balance usage against (over-baseload) generation. The more time you have to play the better you'll get but some tips:- Switch usage times about e.g. Cook evening meal during day
- Save winter washing/drying/ironing for good generation days
- Hoover when the sun shines
- Get to know quirks of your machines e.g. my dishwasher has two periods of heating on eco setting, so stagger this with heating period of washing machine.
- Avoid combining heating times unless you have surplus generation
- At certain times you may find in winter that you still cant use generation. Thats when a fan heater/radiator can be switched on at say 750W or 1.25kW setting to add to the house's heat sink.
- This one I havent yet tried but using a heat pump is likely to ensure you use all generation in winter, early spring/late autumn
- FWIW I was given an old dehydrator and that might be a good part use of surplus summer leccy, when we'll be really struggling to use what we generate, especially as we grow our own fruit.
Excellent post. Just to add, its really good to have an energy monitor to get a feel for what sort of leccy appliances are using and when. I had a monitor for some time before I had the panels so I had a really good feel for what uses the most electric.
Note that if you use an energy monitor once you have panels fitted it will only be measuring your net import or export - this will not be the same as what you are using in the house.
E.g An energy monitor would only read 100w if you were consuming 800w in the house and your panels are producing 700w (import of 100w). It would also read 100w if you panels are producing 900w and you are using 800w (export of 100w)0 -
Ah yes, thanks for that Jon. I see some additional maths coming up as I want a fairly accurate range of readings for my appliance usage0
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Jon_Tiffany wrote: »For some of us this is as much about doing our bit for the environment and UK energy security as it is about the money.
The more we can use at home the less we import from the grid that we have to pay for, so maximising the money saving aspect.
Environmentally, there are many benefits. It makes people much more energy aware, it helps move peak demand to be more evenly spread, there are no 10% transmission losses. In terms of the CO2 payback time estimates range from 2 years to 4 years at the most pessamistic.
We have gone from a net exporter of energy to a net importer. We even now get gas from as far as Qatar.
Have you seen the price of oil lately?
You are still generating the 'off grid energy' whether you are using its yourself or someone else on the grid is making use of the couple of watts you are exporting.
The point you make about gas is a good one, however solar energy will make zero contribution to the need to heat our homes during the winter months.That gum you like is coming back in style.0 -
You are still generating the 'off grid energy' whether you are using its yourself or someone else on the grid is making use of the couple of watts you are exporting.
The point you make about gas is a good one, however solar energy will make zero contribution to the need to heat our homes during the winter months.
Yes, good point. Any excess that is exported will be used by the surrounding properties.
Solar will make some, albeit small contribution in the winter months. I've seen some surprisingly high output on days in December, but of course the days are short and gloomy so the overall output for december is only a fraction of what you get in summer.0 -
Ah yes, thanks for that Jon. I see some additional maths coming up as I want a fairly accurate range of readings for my appliance usage
You might want to look at a plug in meter if you want accurate readings for each appliance. They had some in ALDI's the other week on the specials, under a tenner from memory.
The problem with the energy monitors is that they can not tell the difference between import and export which makes things a little tricky.0 -
Why does it matter when or indeed if you use any of the energy produced by a solar PV array, as you are well paid by the FIT for all the power you generate?
I agree with Jon Tiffany's earlier answer but would not deny, from a financial viewpoint, it makes sense to use your own (free) electricity rather than paying to import from the grid at 10p per kWh. But anything not used, and in a year in my case that will be probably 1500 kWh, will be used by my neighbours with virtually nil transmission loss.
To minimise fossil fuel use for heating I'm considering installing a bivalent heat pump which will use surplus self-generated leccy in part, even in winter months, though I grant it will be very little at times. Any such use will multiply benefit by c2.5x, so I wouldnt be surprised if the pv was responsible for generating maybe 1500 kWh of heat via the heat pump over winter, spring and autumn. A minor part of the heat load, but worthwhile.0 -
Jon_Tiffany wrote: »
Note that if you use an energy monitor once you have panels fitted it will only be measuring your net import or export - this will not be the same as what you are using in the house.
Spot on, unless the panels aren't generating.
If in doubt I quickly switch on/off an oven ring at low setting to check which way the current is flowing.
The other issue with monitors is that they are susceptible to "noise" and give false readings at low levels.0 -
To minimise fossil fuel use for heating I'm considering installing a bivalent heat pump which will use surplus self-generated leccy in part, even in winter months, though I grant it will be very little at times. Any such use will multiply benefit by c2.5x, so I wouldnt be surprised if the pv was responsible for generating maybe 1500 kWh of heat via the heat pump over winter, spring and autumn. A minor part of the heat load, but worthwhile.
I've been looking at heat pumps as well. I think they would work exceptionally well in autumn and spring when outside temps are mild, pv output is good and only low level background heating is needed. However, for the winter months it would be mostly leccy from the grid that would power it.
Currently I dont think it would make financial sense to invest in a heat pump unless you need to replace a heating system anyway or if you dont have access to mains gas.
My feeling is that the price gap between electric and gas will shrink in the coming years as we depend ever more on imports.0 -
Does anyone know if there is a device that can sense when you are exporting and send that electricity to a hot water heater? We would really like to use the surplus to help towards heating our water, DH is good at diy and is already talking about fitting a 500w imersion, but we want a system that will automatically control it for us.
Does such a thing exist? I've searched but not been able to find anything.0 -
Does anyone know if there is a device that can sense when you are exporting and send that electricity to a hot water heater? We would really like to use the surplus to help towards heating our water, DH is good at diy and is already talking about fitting a 500w imersion, but we want a system that will automatically control it for us.
Does such a thing exist? I've searched but not been able to find anything.
Asked several times and someone stated that there is such a system but that it costs several thousands of pounds.0
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