Thursday, 14 November 2013

Two Years In: How Green Technology Works

Today we've been in this house for exactly two years so I'm finally getting round to a new post with a performance review of the house to date. I think the fact that I've not posted up till now indicates how much things have settled down, as establishing how the house works is no longer an issue.....
............................. THIS IS A GOOD THING!


I don't know if it's too early in the season to speculate but the house doesn't seem as chilly as a year ago and we're only needing to add a little extra heat at the moment. Why that is we're not entirely sure - my OH wonders whether the house structure has needed this long to warm up and I'm wondering if it's because I have sussed how to get the incoming air to switch from one external pipe or the other (more of this below). Either way we are more comfortable in the house - except when I do cleaning when the combination of trekking up and down all the stairs and the heat blasted out by the hoover adds considerably to heat gain!

Last winter we were advised to warm the house using the top-up heating attached to the MVHR pipe system. This certainly heats the air going round the house but we found that the structure of the house with its stairwell-chimney effect and consequent air movement meant that all the heated air rose to the top floor resulting in what we technically call the Goldilocks effect over the three floors. This winter we are going to try out a more topical system and heat the rooms we're working in, secure in the knowledge that the top floor will warm up anyway. 

With that in mind I have purchased at enormous expense one of these heaters. It's made by Dyson and costs about five times the cost of a normal plug-in radiator but its claims are big. Given the weird air movement in our sitting room I've splashed out with some of the FIT money on this to see if it works better than last year's efforts in the room. Last night I plugged it in for the first time and although I had to turn the TV volume up by one notch I only needed the heater on for literally ten minutes before the room temperature rose by 1 degree so that was quite impressive.

It's early days though, so watch this space and see if the Dyson claims are true and it's worth buying - unless they unexpectedly offer me vast sums of money(!) it will be an honest response.

The frosts started here last week so we've run the MVHR's top-up heating for a couple of hours first thing in the morning to take the chill off but other than that the only heating we've needed to get things comfortable have been the ten minute blast of heat into the sitting room and running a 1kw heater in the office. That's been enough to have the rooms at 21 degrees so we don't yet need to take the glib advice of millionaires and wear lots of jumpers.

One thing that does make a difference to the heat in the house is the number of people and electrical equipment that's running. Three people and three computers warm the house considerably more than two. I suppose this is obvious but I'm not sure you notice that in a 'normal' house. Even turning the TV on warms a room up after a while and dispenses with the need for extra heat so you're regularly thinking 'should I turn that off and save energy' or  'should I turn that on and save heating'. I suppose I could measure the pros and cons of both options, but I'm not that weird. One amusing thing is the impact of school parties coming to see the technology as 15 teenagers generate a massive amount of heat and warm the office nicely, I'm always reminded of those suits in Dune.

Solar Technology

We have two sorts of solar tech on our roof. The recognisable photovoltaic panels to generate our electricity and vacuum tubes to heat our hot water. We have always been able to measure the amount of energy the panels generate as we have to pass the readings to Good Energy but we've only been able to measure the effectiveness of the tubes for the past 15 months when the new hot water cylinder was installed.

As of today we've generated 2941 kWh for the hot water which is slightly under Ofgem's calculated average electricity consumption for a year. That's a pretty impressive figure for something that takes up a relatively small proportion of the roof.

It appears from our calculations that the vacuum tubes produce more energy per cm of roof compared to the PV panels but there is a caveat that whilst all the energy from the PV goes onto the grid, not all of the heat produced by the tubes is used for the hot water in the summer because above a certain temperature the excess heat is dumped outside. Apparently we should we using this by having a jacuzzi - yeah, right. I'm not sure, therefore, whether we wouldn't have been better off having extra PV panels on the roof rather than the tubes but I'd need to calculate that and I haven't got round to it yet. 

Either way we generated about 89% of our energy usage in the last twelve months and that included a winter when the sun hardly shone and the snow stayed for weeks.

There is a lot of talk dismissing solar technology at the moment as part of the anti-green agenda but, you know what, it works and if it can work in this neck of the woods where the sunny days are such a rare thing that locals write songs praising their glory then it can certainly work in areas that get more sun than this. Even in the grey West Midlands a quick calculation of the financial return on the investment in the solar tech on the roof suggests that it will have paid for itself within about seven years so think what you'd make with a roof in Suffolk or the Isle of Purbeck. This, of course, assumes that the solar industry continues to get government support to get going .....

The Ground Pipe Diverter

I talked a bit about this last time: on either side of the garden we have these air inlets for the house.


The one on the north side of the house, just a few centimetres from the wall, draws air into the house through a short underground pipe, so the incoming air is at the same temperature as the air outside.

The other inlet is in the far corner of the garden and draws the air into the house via over 80 metres of pipe so the air is heated or cooled to the temperature of the soil.
Inside the house the two incoming pipes join and I can use the control panel in the hallway to set the parameters for the 'ground pipe diverter'. This opens or closes a flap where the pipes meet and determines whether I have air coming into the MVHR at the same temperature as outside or pre-cooled/pre-warmed by the ground. In winter this means the air needs to be heated by the heat exchanger from a starting point of 8-12 degrees rather than much lower temperatures, thereby using less energy to get the air in the house up to our preferred temperature - clever eh?

And Finally... The Rant

Insidiously, the high cost of energy in this country appears to now be the fault of subsidies for the poor and the green movement rather than the profit-driven energy companies. I don't know if living in an eco house therefore makes us the new enemies within but I do know that if every house in the country had access to the sort of technology this one does then the country's energy bill and energy load on the planet would be considerably less. Of course less energy use means less profits for the energy industry so never mind the impact of climate change on places like the Philippines last week or the potential for the UK to develop cheaper green technology and get a more balanced economy. cui bono - or 'follow the money' as our US friends say.

I can't end with a negative: cheer yourselves up with the knowledge that it's not all doom and gloom by reading about some more enlightened housing developments in Oldham that featured in The Guardian a couple of weeks ago. We'll get there eventually!

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