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Solar in the morning
It's about 8:30am with light cloud. We're generating 350W at the moment, which is more than we're using. It was already running around 200W when Richard got up at 7am.
Last night, we hit the point where we were using all we generated around 5:30 (apart from cooking tea which is obviously a higher load) and power generation went to zero around 6pm.
I imagine the real test of the system will be on days with heavy cloud. And days are much shorter in winter, of course.
We had 13 panels installed, which is the maximum the roof can take. The economics are very clear on this. If you're going to have panels at all, you should have as many as you can take. There's a large fixed cost for things like erecting scaffolding and installing the inverter - to spread the fixed costs over as many panels as possible makes clear sense. It would not be easy to add more panels at a later date as you'd have to put scaffolding up again.
The interesting question is how much of our electricity usage can be shifted into the daytime. Washing and vacuuming are obvious ones, but I'm wondering about cooking - which is the really heavy drain on any electricity system (apart from kettles and electric showers).
We don't have an electric shower, but if we did, I'd be showering in the daytime from now on.
I see some possibilities with regard to cooking. It may be possible to cook things like potatoes earlier in the day and reduce the amount that needs to be cooked in the evening. (though anyone can save a lot on cooking this kind of thing by using towels on the hay box principle. Bring your spuds/stew/whatever to the boil and simmer for a few minutes, then turn off the ring, cover the pan/casserole with some thick, fluffy towels and come back when you want to eat it and it will be cooked though, still warm, and never burnt)
Last night, we hit the point where we were using all we generated around 5:30 (apart from cooking tea which is obviously a higher load) and power generation went to zero around 6pm.
I imagine the real test of the system will be on days with heavy cloud. And days are much shorter in winter, of course.
We had 13 panels installed, which is the maximum the roof can take. The economics are very clear on this. If you're going to have panels at all, you should have as many as you can take. There's a large fixed cost for things like erecting scaffolding and installing the inverter - to spread the fixed costs over as many panels as possible makes clear sense. It would not be easy to add more panels at a later date as you'd have to put scaffolding up again.
The interesting question is how much of our electricity usage can be shifted into the daytime. Washing and vacuuming are obvious ones, but I'm wondering about cooking - which is the really heavy drain on any electricity system (apart from kettles and electric showers).
We don't have an electric shower, but if we did, I'd be showering in the daytime from now on.
I see some possibilities with regard to cooking. It may be possible to cook things like potatoes earlier in the day and reduce the amount that needs to be cooked in the evening. (though anyone can save a lot on cooking this kind of thing by using towels on the hay box principle. Bring your spuds/stew/whatever to the boil and simmer for a few minutes, then turn off the ring, cover the pan/casserole with some thick, fluffy towels and come back when you want to eat it and it will be cooked though, still warm, and never burnt)
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Also, changing your usage patterns to daytime instead of nighttime usage, will certainly help. Something like a slow-cooker might be an idea - put food in the cooker in the morning, it doesn't use a lot of power, then eat when you get in in the evening.
A better solar power system could have a large bank of batteries, so the power you generate is stored, rather than put onto the grid. Then you'd have some for night time as well. I know I'd be tempted to install some form of low voltage lighting system and get a couple of old car batteries and make a slow charger for them.
I doubt you'll generate enough to power more than one electric ring, they use a lot, and electric showers use as much power as 3-5 kettles (6,000 to 10,000 Watts).
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I haven't come across a good system for battery charging. The thing is that you've got to be careful that the sun doesn't suddenly vanish, leaving you charging the battery from the mains. If someone invents a gadget that can use the surplus to either charge a battery or heat water, then I'll jump on it (if it's a sensible price)
electic showers are an invention of the devil as far as I'm concerned. Way too expensive for anyone to use if they're actually aware of the cost.
Towel cookery probably works even better than a slow cooker. Insulation achieves wonders. Though I might look into a slow cooker.
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Would preparing food earlier in large batches and microwaving for a few minutes when you need it work?- I admit I have no idea what power a small microwave uses though
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Microwaves are quite high, though use less energy overall for the same amount of food.
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I'd not really considered solar power as viable in this cloudy country of ours but your experiences may well change my mind.
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I'd wait for a cloudy day before seeing how viable the system is. I'm expecting a dramatic drop in generation then.
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Get on the roof with torches.
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As for your batteries, if you were to take that approach, the solution would need to basically have the batteries float charging, so that during the day it's the batteries pick up the slack when the PV is generating less than your consumption, and charging when the PV is generating more. It'd have to cut off when the batteries hit a certain charge state and switch to utility power at that point, but when that is working properly, and with the right changes in your power consumption profile that should work quite well.
A battery solution would also allow usage of other, less efficient power generation sources - think something like a micro paddlewheel at the bottom of your rhone pipes - small, cheap to build/install and generates a little power when it's raining, feeding back to the batteries and contributing to your total renewable generation stock.
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The other problem is finding suitable batteries. I've not seen anything that really fits the bill. It has to be safe, not take up too much space, and be easy to use/maintain (and not cost a small fortune). Most of the ones I've seen are really only a solution for people living off-grid.
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You'd need a diode in line with the panels feed to the invertor (which you probably have anyway) - you then just hook up the batteries on the side of the wires from the panels - this way when there is sufficient current from the PV the batteries will get charged, when the PV stops generating the batteries will discharge into the invertor and at a certain point (which would need fairly basic battery protector circuitry - caravans have this) the battery will stop discharging and the setup you have now will just let the utility power take over.
No risk of the utility power being used to charge the batteries, and they'll leech off any surplus power the PV's generating at any given point in time, until they're fully charged. They will also smooth off the supply from the panels to a large extent meaning that you'll get pretty much your peak power output for a lot of the day as the batteries discharge when the panels aren't getting much light - of course only if there's something requiring the power.
A diode is just a one-way valve for electricity - it will only allow current to flow in one direction, so all that can happen in this circumstance is power going to the invertor.
Batteries are a definite issue - you don't want to use Lead Acid or Gelly Cells indoor as they emit hydrogen when charging which can lead to some interesting effects.
NiMH batteries are *relatively* inexpensive, and available fairly easily and can take a decent charge - they're what most commercial UPS's use these days. Depending on what you want them to do (say constant drain of 200W for 10 hours - 2kWh or so. A 2.2kWh NiMH commercial battery pack can be had that weighs 35kg and is 65x17.5x14cm - that's not that big really. What's that? 2 foot x 8" x 6"? The 3.5kWh pack from the same supplier is the same dimensions, but a yard tall (95cm by their spec)
Can't say as to the cost of them I'm afraid.
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Definitely -- particularly if your heating/hot water is currently on a combi boiler. Solar hot water can act as effectively a pre-heater for the boiler, and the plumbing required is straightforward. And (if they stick with what they're trailed) the govt are introducing a subsidy scheme (http://www.decc.gov.uk/en/content/cms/news/rhi_wms/rhi_wms.aspx) for solar hot water schemes come the summer.
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