Tuesday 24 April 2012

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...]

Friday 6 April 2012

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 30ยบ, 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.