Solar Power, part 2

At the very end of last year, right before the subsidy rate dropped in January, I had solar panels installed: you may remember that I blogged about it at the time. I thought you might be interested to know how that’s working out for us.

Solar panels on our roof.
A power plant, right on top of our house. It’s very small – like, a “13” on Power Grid – but it’s ours.

Because I’m a data nerd, I decided to monitor our energy usage, production, and total cost in order to fully understand the economic impact of our tiny power station. I appreciate that many of you might not be able to appreciate how cool this kind of data is, but that’s because you don’t have as good an appreciation of how fun statistics can be… it is cool, damn it!

This chart, for example, shows our energy usage in KWh of each of gas and electricity for the last 8 months.
This stacked area chart, for example, shows our energy usage in KWh of each of gas and electricity for the last 8 months.

If you look at the chart above, for example (click for a bigger version), you’ll notice a few things:

  • We use a lot more KWh of gas than electricity (note that’s not units of gas: our gas meter measures in cubic feet, which means we have to multiply by around… 31.5936106… to get the KWh… yes, really – more information here), but electricity is correspondingly 3.2 times more expensive per KWh – I have a separate chart to measure our daily energy costs, and it is if anything even more exciting (can you imagine!) than this one.
  • Our gas usage grows dramatically in the winter – that’s what the big pink “lump” is. That’s sort-of what you’d expect on account of our gas central heating.
  • Our electricity usage has trended downwards since the beginning of the year, when the solar panels were installed. It’s hard to see with the gas scale throwing it off (but again, the “cost per day” chart makes it very clear). There’s also a bit near the end where the electricity usage seems to fall of the bottom of the chart… more on that in a moment.
Solar panels pay for themselves by (1) powering your appliances, thus meaning you buy less electricity from the grid, (2) selling electricity that is generated but not used back to the grid, and (3) through a subsidy scheme that rewards the generation of green electricity.
Solar panels (slowly) pay for themselves in three different ways. People often find it surprising that there aren’t only one or two.

What got me sold on the idea of installing solar panels, though, was their long-term investment potential. I had the money sitting around anyway, and by my calculations we’ll get a significantly better return-on-investment out of our little roof-mounted power station than I would out of a high-interest savings account or bond. And that’s because of the oft-forgotten “third way” in which solar panelling pays for itself. Allow me to explain:

  1. Powering appliances: the first and most-obvious way in which solar power makes economic sense is that it powers your appliances. Right now, we generate almost as much electricity as we use (although because we use significantly more power in the evenings, only about a third of what which we generate goes directly into making our plethora of computers hum away).
  2. Selling back to the grid (export tariff): as you’re probably aware, it’s possible for a household solar array to feed power back into the National Grid: so the daylight that we’re collecting at times when we don’t need the electricity is being sold back to our energy company (who in turn is selling it, most-likely, to our neighbours). Because they’re of an inclination to make a profit, though (and more-importantly, because we can’t commit to making electricity for them when they need it: only during the day, and dependent upon sunlight), they only buy units from us at about a third of the rate that they sell them to consumers. As a result, it’s worth our while trying to use the power we generate (e.g. to charge batteries and to run things that can be run “at any point” during the day like the dishwasher, etc.) rather than to sell it only to have to buy it back.
  3. From a government subsidy (feed-in tariff): here’s the pleasant surprise – as part of government efforts to increase the proportion of the country’s energy that is produced from renewable sources, they subsidise renewable microgeneration. So if you install a wind turbine in your garden or a solar array on your roof, you’ll get a kickback for each unit of electricity that you generate. And that’s true whether you use it to power appliances or sell it back to the grid – in the latter case, you’re basically being paid twice for it! The rate that you get paid as a subsidy gets locked-in for ~20 years after you build your array, but it’s gradually decreasing. We’re getting paid a little over 14.5p per unit of electricity generated, per day.
A graph showing the number of units per day we've generated, peaking during that  sunny spell in late April.
Late April was bright and sunny and we were able to generate up to 19 units per day (for contrast, we use around 12 units per day), but May has so-far been rainy and grey and we’ve made only about 13 units per day.

As the seasons have changed from Winter through Spring we’ve steadily seen our generation levels climbing. On a typical day, we now make more electricity than we use. We’re still having to buy power from the grid, of course, because we use more electricity in the evening than we’re able to generate when the sun is low in the sky: however, if (one day) technology like Tesla’s PowerWall becomes widely-available at reasonable prices, there’s no reason that a house like ours couldn’t be totally independent of the grid for 6-8 months of the year.

Two SSE engineers head back to their van.
These guys came and replaced our electricity meter, because it was… umm… running backwards.

So: what are we saving/making? Well, looking at the last week of April and the first week of May, and comparing them to the same period last year:

  1. Powering appliances: we’re saving about 60p per day on electricity costs (down to about £1.30 per day).
  2. Selling back to the grid: we’re earning about 50p per day in exports.
  3. From a government subsidy: we’re earning about £2.37 per day in subsidies.

As I’m sure you can see: this isn’t peanuts. When you include the subsidy then it’s possible to consider our energy as being functionally “free”, even after you compensate for the shorter days of the winter. Of course, there’s a significant up-front cost in installing solar panels! It’s hard to say exactly when, at this point, I expect them to have paid for themselves (from which point I’ll be able to use the expected life of the equipment to more-accurately predict the total return-on-investment): I’m planning to monitor the situation for at least a year, to cover the variance of the seasons, but I will of course report back when I have more data.

Electricity meter with red light showing.
Our new electricity meter, which replaced the old one – one of those with a “wheel”. The red light indicates that fraud has been detected. Yeah, about that…

I mentioned that the first graph wasn’t accurate? Yeah: so it turns out that our house’s original electricity meter was of an older design that would run backwards when electricity was being exported to the grid. Which was great to see, but not something that our electricity company approved of, on account of the fact that they were then paying us for the electricity we sold back to the grid, twice: for a couple of days of April sunshine, our electricity meter consistently ran backwards throughout the day. So they sent a couple of engineers out to replace it with a more-modern one, pictured above (which has a different problem: its “fraud light” comes on whenever we’re sending power back to the grid, but apparently that’s “to be expected”).

In any case, this quirk of our old meter has made some of my numbers from earlier this year more-optimistic than they might otherwise be, and while I’ve tried to compensate for this it’s hard to be certain that my estimates prior to its replacement are accurate. So it’s probably going to take me a little longer than I’d planned to have an accurate baseline of exactly how much money solar is making for us.

But making money, it certainly is.

Edinburgh 2012 – Day Three

On the third day of our Edinburgh Fringe Festival Holiday, Ruth, JTA and I… saw more Free Fringe comedy. Are you spotting a theme, here?

Matt R with Helen Arney of Domestic Science, explaining why he's drawn a silicon lattice onto an iced bun.
Matt R with Helen Arney of Domestic Science, explaining why he’s drawn a silicon lattice onto an iced bun.

First up was Domestic Science, with “real life – for now – partners” Helen Arney and Rob Wells. This pair brought science to life, opening by re-enacting an event from one of their first dates when they discovered that turmeric contains curcumin, a pH indicator, and demonstrating how this can be used (by first dying noodles with turmeric, and then dipping them into acidic and alkaline solutions to observe their colour change). Later, they’d go on to perform audience-participation demonstrations of gravitational wobbles (as a mechanism to detect extrasolar planets), AM radiowave reflection off the ionosphere, and more. They also used us as a live experiment, having us listen to jokes written by comedians of different genders (but recorded in both male and female voices) and rate them, in order to see if the gender can be determined by the listener. All in all, a really enjoyable first show for the day.

Helen Arney retweets my message "New day, new #EdFringe shows. Starting with @DomesticScience. Looks like there'll be a test at the end", adding "Congrats! You passed!"
Helen’s response to my tweet that there must be going to be a test, after finding a sheet of paper with numbers on it, on my seat (it later turned out to be for the engendered-joke study).

Ruth and I took our lunch in David Bann’s vegetarian restaurant, here in Edinburgh, which was delicious, although I probably should have stopped at two courses and not also had desert, as I then spent most of the afternoon waddling around like a fat penguin. I can particularly recommend the aubergine, chick pea and cashew koftas.

David Bann, Edinburgh.
David Bann, Edinburgh.

Next up, we went to see Yianni‘s new show, Numb and Number. We’d first seen Yianni in 2006 (we had him take a photo of us with Peter Buckley Hill), and he was even more brilliant now than he  was back then. In this new show, he talks about autism, numbers, and rainbows, in exactly the right order (any other order would be wrong, right?). Poor JTA was picked on and tricked into coming across as racist, but in the most hilarious possible way.

Matt R and JTA enjoy a quick after-dinner whisky, before it's time to go out for more comedy.
Matt R and JTA enjoy a quick after-dinner whisky, before it’s time to go out for more comedy.

You might remember that yesterday, Matt was invited on stage to separate currency for magicians Young & Strange? Well: coincidentally, Yianni asked Matt what was significant about the sum £88.88, and quick as a flash Matt responded that it was the sum of all of the denominations of currency (1p, 2p, 5p, 10p, 20p, 50p, £1, £2, £5, £10, £20, £50). He denies it, but I’m pretty sure that he wouldn’t have been able to pull off this trick if he hadn’t have been reminded of this just the previous day.

We retreated to the flat for a haggis dinner and a round of whisky before heading out again. My stomach was already bloated from my huge lunch, and I’m not sure that a large dinner really agreed with it: I almost required help to roll me up the street to the next show.

Phill Jupitus leaps around in front of JTA.
Phill Jupitus leaps around in front of JTA. Unfortunately, my camera wasn’t quick enough to catch him in the dim light of the Canon’s Gait basement, so you’ll probably have to take my word for it that it’s him.

We finished our day with Peter Buckley Hill And Some Comedians, still probably our go-to Free Fringe show. This evening, his line-up featured Phill Jupitus of Never Mind The Buzzcocks fame, who talked about the week that he met a Beatle and two Rolling Stones, leaving the audience laughing themselves to tears. Also in the line-up was Wil Hodgson, a heavily-tattooed former wrestler with a shaved head, who talked mostly about his hobbies of collecting My Little Pony toys. He won JTA over, I think, when he finished his set shouting “Fuck Laughing Horse!”

And then, at last, it was time for bed.

Cardless Cashpoints

My mobile banking app, showing me a special six digit code.
The mobile app presents you with a special six-digit code that is used to withdraw the cash.

RBS Group this week rolled out a service to all of its customers, allowing them to withdraw cash from an ATM without using their bank card. The service is based upon the same technologies that’s used to provide emergency access to cash by people who’ve had their cards stolen, but integrates directly into the mobile banking apps of the group’s constituent banks. I decided to give it a go.

The first step is to use the mobile app to request a withdrawal. There’s an icon for this, but it’s a bit of a mystery that it’s there unless you already know what you’re looking for. You can’t make a request from online banking without using the mobile app, which seems to be an oversight (in case you can’t think of a reason that you’d want to do this, read on: there’s one at the end). I opted to withdraw £50.

Next, it’s off to find a cash machine. I struck out, without my wallet, to try to find the nearest Royal Bank of Scotland, NatWest, or Tesco cashpoint. The mobile app features a GPS tool to help you find these, although it didn’t seem to think that my local Tesco cashpoint existed, walking me on to a branch of NatWest.

Cash machine: "Do you wish to carry out a Get Cash or Emergency Cash transaction? [No] [Yes]"
The readout of the cash machine demonstrates that the roots of the “Get Cash” system lie in the older “Emergency Cash” feature: the two are functionally the same thing.
As instructed by the app, I pressed the Enter key on the keypad of the cash machine. This bypasses the usual “Insert card” prompt and asks, “Do you wish to carry out a Get Cash or Emergency Cash transaction?” I pressed Yes.

Entering a 6-digit code from a mobile phone into a cash machine.
The number displayed upon the screen is entered into the cash machine.

The ATM asked for the PIN I’d been given by the mobile app: a 6-digit code. Each code is only valid for a window of 3 hours and can only be used once.

A cashpoint asking for the PIN a second time, and then asking for the amount of money to withdraw.
The cash machine asks for the PIN a second time, and then asks for the sum of money to be withdrawn.

I’m not sure why, but the ATM asks that the PIN is confirmed by being entered a second time. This doesn’t make a lot of sense to me – if it was mistyped, it’d surely fail anyway (unless I happened to guess another valid code, within its window), and I’d simply be able to try again. And if I were an attacker, trying to guess numbers, then there’s no difficulty in typing the same number twice.

It’s possible that this is an attempt at human-tarpitting, but that wouldn’t be the best way to do it. If the aim is to stop a hacker from attempting many codes in quick succession, simply imposing a delay would be far more effective (this is commonplace with cash machines anyway: ever notice that you can’t put a card in right after the last transaction has finished?). Strange.

Finally, the ATM asks what value of cash was agreed to be withdrawn. I haven’t tried putting in an incorrect value, but I assume that it would refuse to dispense any cash if the wrong number was entered – this is presumably a final check that you really are who you claim to be.

Cash machine: "Please take your cash and your receipt."
It feels strange taking money and a receipt from a cashpoint without first having to retrieve my card. I spent a few minutes after the experience with a feeling that I’d forgotten something.

It worked. I got my money. The mobile app quickly updated to reflect the change to my balance and invalidated the code: the system was a success.

The banks claim that this will be useful for times that you’ve not got your card with you. Personally, I don’t think I ever take my phone outdoors without also taking my wallet with me, so the chance of that it pretty slim. If my card were stolen, I’d be phoning the bank to cancel the card anyway, so it wouldn’t save me a call, either, if I needed emergency cash. But there are a couple of situations in which I’d consider using this neat little feature:

  • If I was suspicious of a possible card-skimming device on a cash machine, but I needed to withdraw money and there wasn’t an un-tampered ATM in the vicinity. It’d be nice to know that you can avoid having your card scanned by some kid with a skimmer just by using your phone to do the authentication rather than a valuable piece of plastic.
  • To send money to somebody else. Using this tool is cheaper than a money order and faster than a bank transfer: it’s an instantaneous way to get small sums of cash directly into the hands of a distant friend. “Sure, I’ll lend you £50: just go to a cash machine and type in this code.” I’m not sure whether or not this is a legitimate use of the service, but I can almost guarantee that it’ll be the most-popular. It’ll probably be reassuring to parents of teenagers, for example, who know that they can help their offspring get a taxi home when they’ve got themselves stranded somewhere.

What do you think? If you’re with RBS, NatWest or Tesco, have you tried this new mobile banking feature? Do you think there’s mileage in it as an idea, or is it a solution in need of a problem?

Thursday Afternoon

Good progress at work today, easily catching up on the things I didn’t get done yesterday on account of having been at the Royal Welsh Show.

AbNib is proving itself popular, but I’m still not happy with it: there are a load of really cool features I’d like to add, yet. But that’s a job for another day. I’ll be up in Lancashire this weekend for Andy‘s party and to visit my folks, so I can’t do it then, either.

Claire’s gotten herself temporarily sterilized with a fantastic hyperdermic full of progesterone and with the aid of the nice people at Aberystwyth Family Planning Clinic. Woo and indeed hoo. She’s (theoretically) a lot less likely to forget to have an injection every three months than she is to forget to take the pill: something she’s demonstrated herself to be very proficient at.

I’ve been excessivley stressed for the last 48 or so hours. I think it’s mostly a result of having no money and my paycheque still being a week away, and having to live off my credit card in the meantime (which I don’t like doing). Also that my crisp-wound in my mouth from the other day has developed into a spot which would probably heal faster and hurt less if I could stop playing with it, but I can’t. And that I’m not making nearly as much coding progress on Three Rings as I should be.

I have a strange urge to go for a long walk in the rain this evening. I hope it rains.

Late

Running late for work. Was supposed to get up and take laptop to Daton as part of an insurance scam, but I’m still at home after having woken up late. Still, Claire’ll be at work until about 1am today… in Newtown… so there’s no benefit to me coming home early. I’ll work late.

Updated Troma Night at long last – this web site chronicles the things I get up to on termtime Saturday nights.

Suppose I oughta go get this laptop sorted and put my paycheque into the bank, then get my lazy layabout arse to work.

Chasing The Paycheck

What with unavailable accountants and worse, I’ve not been able to get my paycheque until today – a week later than expected. I have £2.50, half a loaf of bread, a tin of beans, and a packet of super noodles to live on until my cheque is cashed. I don’t think that Sainsbury’s Recipe Finder quite understood me when I explained my situation, on account of it suggesting the following:

Cowboy Baked Beans
Prep and cook time: 30 mins to 1 hour
Serves: 6-8
Ingredients: 25g butter, 1 large onion, chopped finely, 1 clove garlic (optional), crushed, 2.5cm piece fresh root ginger, crushed, 1 each green and red pepper, cored, seeded, and chopped, 2 carrots, diced, 30ml vinegar, 60ml clear honey, 5ml Worcestershire sauce, 900g baked beans (hah! I only have a 450g can of baked beans anyway), 125g streaky bacon, sliced.

If you want the full recipe, go visit Sainsbury’s Recipe Finder.

In the end, Kit and I celebrated my paycheck by buying a heap of interesting looking ingredients from Somerfield, and made ourselves some cheesy garlic bread, a smokey-mince and pork tomato sauce with pasta-thingy, and some cheesecake. Then ate most of it. Fab.

It’s amazing what a little money will do for you. Last night we ate corned beef on toast.

Cool Thing Of The Day

Cool And Interesting Thing Of The Day To Do At The University Of Wales, Aberystwyth, #42:

Count your 20p piece collection (see “Cool Thing” #25). Realise you have exactly £6 (that’s 30) of them. Do your laundry

The ‘cool and interesting things’ were originally published to a location at which my “friends back home” could read them, during the first few months of my time at the University of Wales, Aberystwyth, which I started in September 1999. It proved to be particularly popular, and so now it is immortalised through the medium of my weblog.

Cool Thing Of The Day

Cool And Interesting Thing Of The Day To Do At The University Of Wales, Aberystwyth, #25:

Start a collection of 20p pieces, for use in the laundry. My wallet’s side pocket now contains 16 20p peices. Combined with a few pound coins, that’ll keep me laundered (ooh-err) for at least two weeks. =o)

The ‘cool and interesting things’ were originally published to a location at which my “friends back home” could read them, during the first few months of my time at the University of Wales, Aberystwyth, which I started in September 1999. It proved to be particularly popular, and so now it is immortalised through the medium of my weblog.

Cool Thing Of The Day

Cool And Interesting Thing Of The Day To Do At The University Of Wales, Aberystwyth, #23:

Leave a club, and, in a drunken stupor, decide that it’s a sound and logical idea to take £120 out ot a cash machine, because it’ll save you from having to do it later. Realise this tommorow morning, and replace the money. Decide that taking your card out when you’re going to get pissed isn’t such a smart idea, after all.

The ‘cool and interesting things’ were originally published to a location at which my “friends back home” could read them, during the first few months of my time at the University of Wales, Aberystwyth, which I started in September 1999. It proved to be particularly popular, and so now it is immortalised through the medium of my weblog.