Why we are not 'Green'

[Mike's note: Anne now has posting access to this blog, so, here she is with a perhaps somewhat controversial post to kick things off. I'll add a comment at the end.]

This is my first post on this site so I thought I'd start with why we are not Green.

Firstly, the reasons we have started doing this is because we can, not because it makes us have better Karma in the ecofriendly department. We have solar water heating because someone sold us a good story a few years ago and I bought into it hook, line and sinker (some other previous housemates will know that I do this on occasions with other purchases - timeshare, Vacuum cleaners, etc.)

We are NOT 'Green' with a capital 'G'.

• I like my washing machine, and tumble drier. I do not hang out the laundry in the garden, or over radiators, I tumble it. I have a hard and long job and I can't just take the washing down if it rains, and usually don't have time to hang it up either.
• I like baths. Mike and James prefer showers and I know that baths use lots more water, but I like relaxing in the bath and washing my cares away.
• I would like to say that I am at least green enough to never water the garden. (This is not because I think it wastes water, but because I hate gardening). Hosepipe bans will not worry us.
• I like my house warm. We have a digital display weather station and I have discovered I like my house to stay at around 20'C and I will put the radiators on for a 1 hour boost if it goes below this.
• I buy all my food from a supermarket, not from any local butchers, greengrocers etc. I could be bothered to do this if I had time, but I don't - (see time consuming job as above)
• I like television. We have the TV on for about 3 hours a night, which probably makes for a lot of energy use. I also like to see where I am going between rooms, although I have started making the family turn lights off when not in the rooms now.
• Mike has computers. They are everywhere and they seem to be on ALL the time.

Things we have done that we would have done anyway but they have made us more energy efficient.

• Solar water heating - we have had this for about 7 years now, and mostly it has stopped us just indiscriminately turning the hot water on when we want baths/showers. It has not saved us very much at all, as the gas bill is mostly to heat the radiators.
• We recently changed the boiler. We needed to move it because it was in the way of our new ensuite bathroom, and it was going to cost less to buy a new one than move and renovate the old one. Since we have done this our winter daily gas usage went down from 130 kWh/day in December 2010 to 90 kWh/day in December 2011. Now of course this may also be due to having a milder winter.
• We have bought a new fridge. It is a A+ rated fridge. Don't know what the old one was as it came with the house 10 years ago. I think the savings will be minimal and will probably not pay for the fridge anytime soon.
• We have bought a new oven. Our old oven grill died about 3 years ago and we have been making do with a George Foreman tabletop grill since. This was great but you can't make cheese on toast in it as the cheese sticks to the lid. The oven seemed to take over 30 minutes to get to temperature, so we finally decided to buy a new one. It now takes about 10 minutes to heat up, so this has got to be saving energy, right?
• The energy monitor. Mike has talked a lot about this, so I won't go into it now.
• It has taken me about 2 years to get Mike to downsize the number of computers in the house. Last April we finally moved all the servers into my office and removed one from use. I think that and shutting my computer off when not in use has saved us approximately 4 kWh per day.
• Photovoltaics - well this is what a goodly part of this blog is about so I won't go into any more details here.

Well I hope this is a useful start to the blog and I will add some actual numbers in another post.

[Mike: I think there's an important distinction to be drawn here between 'green' and 'Green'. We're doing our damnedest to do what we can to make the Mill House 'green' with a small 'g'. Fundamentally, we don't live a 'Green' with a big 'G' lifestyle, but what we're trying to explore here is how to become more energy efficient within the way we choose to live our lives: the power of a lot of small changes, increased awareness etc. If everyone did this much...]

Is my house suitable for Solar PV?

There are, as I'm sure you've noticed, a lot of folks advertising solar PV at the moment, despite all the fun with Her Majesty's Government, the courts and the feed-in tariff (of which more in a later post). Setting aside for that later post the question of 'can we afford it?', this post looks at the practicalities of solar PV.

The ideal roof for solar PV is big enough to hold a 4kW system (about 30 sq m), slopes at a bit over 30º, faces due south, and has no shade. However, if you can't manage that, you're probably still OK. Provided you have a roof, or more than one in fact, with not over much shade, that faces at least a little bit south, you will be able to generate a reasonable amount of electricity. Surprisingly, all other things being equal, a roof facing east or west potentially generates 86% of the power of a south-facing roof.

There are a number of handy online sites that you can plug a postcode and a rough idea of your roof configuration into, and in return it'll spit out an equally rough idea of how many kWh you can expect to generate in a year. They're generally much of a muchness, since they all tend to use the SAP 2009 based calculations, which in a nutshell multiply the output rating of the panels by a factor that takes into account an element for facing, for angle of roof and for shade. If you have half a brain and a pocket calculator or a spreadsheet you can do it yourself, pretty much!

Consensus is that the independent estimator at PVGIS is better (SAP 2009 is apparently a bit pessimistic), but suppliers are, as I understand it, required to give you estimates of ROI based on SAP 2009. Of course, it's all entirely weather dependent, on top of that. This past week we've had a 16+ kWh day on April 1st, and a miserably wet day on the 4th that generated a stupendously uninspiring 1.24 kWh.

Most suppliers will be reasonably straight with you, although when we got our quotes we did find that the SAP 2009 factor varied from 690 to 820 for the same roof! It's worth plugging everyone's quotes for the power output of the system and the predicted annual generation in kWh into a spreadsheet and comparing them, just to see who might be over-egging the pudding a bit.

To summarise, though, as long as you have a decent roof that isn't entirely shaded by trees or next door, and faces at least a bit south, it's worth asking for a quote. Most if not all companies don't charge for quotes, and as long as you don't let them pull the wool over your eyes as regards ROI, you'll be fine. Of which, more next time.

Solar PV - the basics

As I mentioned in the original post, as well as solar water heating we also have (as of last week) solar electricity, or solar PV as it's more commonly known.

I thought I'd start out with a brief description of how a solar PV system goes together. First, a diagram!

A generic domestic solar PV system

Ok, So...

The two main components of the system are the PV cells themselves, and the inverter.

PV is short for "photo-voltaic' from the Greek photos, light, and Alessandro Volta, who invented the first battery - basically PV cells turn light into DC electricity, and the more light, the higher the voltage they generate.

Now, DC is not much use for running household equipment, as that requires 240V AC. Enter the inverter, whose job, pretty simply, is to turn DC into AC. This is where things get a little less simple, since inverters have a minimum voltage at which they will 'kick in', so if it's not bright enough to generate that minimum voltage? No electricity. Once it does kick in, the higher the voltage off the PV cells, the more power (and thus the more units of electricity) the inverter kicks out.

In our configuration[*], the inverter feeds into a spare breaker on our fuse box, via a meter that measures the total units of electricity generated (very important, as this is how you get your Feed-In Tariff, of which more in a later article). If there's more being generated than the house is using, then (by the magic of electricity) the excess is fed back to the grid, otherwise the grid supplies the balance.

And that's pretty much it. Other than to note that, if you were dreaming of being able to go 'off-grid' when the power goes out? Most systems don't, and more awkwardly, they actually shut down when the power goes off. Annoying and somewhat paradoxical - the reason behind it is that in order not to cause disruption to the grid, it's essential that the inverter syncs up to the frequency of the grid supply, and it's a requirement that if the grid goes off, it shuts down until it comes back.

Next in this series of posts, I'll look at how to calculate what kind of power you can get from a PV system.

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[*] In some systems, the inverter is connected up in the meter cabinet instead of to the fuse box: this makes little or no difference to how things work.

E.On's Energy Fit monitor

We've been E.On customers for a while now, and in around 2010 they sent all their customers what they called their "Energy Fit" Starter Pack. In a nutshell, it's a clamp sensor, plus a small wireless transmitter for it to plug into, a base unit with a big LCD, a USB cable, and some documentation and a CD.

I was not at all surprised to discover the CD was Windows-only, and had a gentle go at E.On for that. Reading around a bit, I discovered a couple of useful things:

• the Windows software basically read the data off the meter and fed it to Google PowerMeter
• the device was actually a rebadged CurrentCost EnviR

A bit more Googling around revealed the CurrentCost page with the specs on how to talk to it, and a few assorted folks' sample code to do so, and the fact that the USB cable was simply a USB-to-serial adaptor. Brilliant.

Not that much coding later, I had a Perl script on our Linux server (which I'm not going to share just yet, for reasons I'll explain in a later post) that both displayed the instantaneous value of the clamp sensor on a web page, and uploaded the data to Google PowerMeter. Which was fab, right up to the point where Google decided that, and I quote:

 "...our efforts have not scaled as quickly as we would like, so we are retiring the service." 

Colour me unimpressed. Especially when earlier in the same press release they said, quote:

"Studies show that having simple access to such information helps consumers reduce their energy use by up to 15%; of course, even broader access to this information could help reduce energy use worldwide."

Lovely. Nice one, Google. Way to help out there. Nice to see the studies back up my views on monitoring, though.

The script's still running and saving the data, and I'm currently feeding it into Splunk, which is a sysadmin tool I've used at work, and comes with a free version which'll handle the volume of data we generate. While it's an über-geeky solution, I wouldn't recommend it since Splunk does require a pile of customisation to generate wife-friendly dashboards, and there's still the overhead of running the background script to feed it. 

But - it has taught me a fair bit about what it's capable of, and a lot more about what else was out there. If you can get your hands on one, be it the E.On branded one or a CurrentCost, they're pretty easy to set up and get info out of, and you will learn a lot about your power usage habits.

Why monitor?

It may seem an obvious question, I know. And I'd be the first to admit that having devices I can interrogate remotely appeals to my inner geek, as does making stuff that isn't supposed to talk to anything but a closed-source, badly-written Windows app or a proprietary web service bend to my will. I'll freely confess that I'm a gadget freak, and that generating our own hot water and electricity is just cool.

But this isn't just about being geeky: it's about knowing what's happening in your system. For example, since having the solar water heating, I'd bet that we've saved nearly as much through being aware of what hot water we have and how long it takes to heat, as we have by generating it ourselves.

Equally, since I got the clamp sensor installed and talking to the computer, all of us at the Mill House have been very aware of saving energy - if you know that (for example) your house with most of its 'always on' stuff (fridge, freezer, server, etc) ticks over at 380W, then if you see a reading of 700W you'll start to investigate what's causing it. At some point I will let Anne post a breakdown of last year's energy savings here, but for now I'd just note that our electricity usage dropped by around 30% over 2011, just through knowing what we were using. (And, I should add before Anne does, through finally shutting down two Linux servers with very old power supplies. Old power supplies become very energy inefficient (several hundred Watts worth), which is why our house server is now a 60W miniITX box from the good folks at LinITX.com along with a similarly rated HP Media Server as a fileserver.)

But of course, that's just the first step. Sure, you can install your solar PV and sit back and watch the Feed-In Tariff money roll in on sunny days. But shouldn't you be using all that green electricity? As an example, our dryer is now on a timer (and once I get it set up, it'll be on a computer controlled switch, in fact) that only lets it run at times when the PV is likely to be generating most if not all of the power. (And sure, yes, we could hang it out in the garden. But both of us work, so being in to remove it when it rains isn't so easy...!)

Given the tightness of everyone's budgets generally, let alone the current move towards being at the very least energy efficient, and ideally as green as possible, I personally think it's vital to know both where your energy is coming from, and what's using it, long before the bill turns up. And setting things up to do so doesn't cost that much.

Clamp sensors

Currently, our electricity supplier is E.On (though we're looking at Ecotricity) and, back in 2010, they sent us a free energy meter together with a clamp sensor. More on the meter later, but for now I'll briefly discuss the clamp sensor, and what it does and doesn't do.

In a nutshell, what you do is clip it round the incoming feed to your electricity meter (or, in fact, any current-carrying cable), and it has a go at measuring the power consumption through the cable. What the meter connected to it then does is work out the current in your cable based on what's induced in the clamp loop, and then make a bunch of assumptions to calculate the power. Specifically, unless you have a smarter than average device at the other end, it assumes it's seeing 240V (in the UK), and then

power P = voltage V * current I * a fudge factor.

This falls short of ideal in a number of ways:

• your mains voltage can fluctuate a bit
• the actual current induced in the clamp can be affected by precisely how you place the clamp
• it takes no account of the kind of devices connected to your electricity

This latter can be quite noticeable. I won't go into details, but if a device has inductance or capacitance as well as resistance, then the equation isn't just P = V * I, and it depends on the nature of the particular device. Things with heating coils and big motors tend to be particular culprits, and most of us have one or more of those in the house!

There's also another problem which rears its head when you install solar PV cells - when your inverter kicks out more power than your house uses, the rest gets fed back to the grid. Because of the way it works, the clamp sensor can't measure which way the current flows, so it can't tell if you're using or generating power. 

So why use a clamp sensor? Well:

• it works on any current-carrying cable
• if you have an old-style electricity meter, it's your only choice
• if you have solar PV, unless you have a smart meter that your PC can talk to, it's your only way of measuring how much electricity you send back to the grid (in conjunction with another sensor)

The latter is why we're hanging on to ours. More on our monitoring system in later posts.

Solar water cost and ROI

Our panels (a pair of evacuated tube panels) set us back of the order of £9000 in (if I remember correctly) 2004. With hindsight, I think we did this too early - the price of a similar system has now dropped considerably (more like £2500-5000, apparently). We're probably saving £50-80 a year, so the ROI time is... a while yet.

On which topic, it's worth noting that our suppliers went out of business, and were taken to court indirectly over their rather inflated ROI claims, and we did get £4000 back as a result. We're currently using the local Peterborough Boiler Services to maintain our system (not that it needs much!), and are pretty happy with them.

It's also worth noting that there are two government incentive payments for solar hot water, one of which is available now, one to come. The one available now is the Renewable Heat Premium Payment, which is (or pretty much was since the deadline is March 31st) a scheme which pays £300 for any solar water heating install since Aug 1st 2011. The future one is the Renewable Heat Incentive - basically, if you've installed since 15th July 2009 (bother!), you will be eligible for some form of payment similar to the solar PV Feed-In Tariff.

As I said, with hindsight, we should probably have left it a couple of years: I'll get some stats upon a subsequent post for the last few years' gas bills, so you can see how much we've saved. Either that or I'll give Anne posting rights on this blog, and she can!