Wood, wind and sunny Govan
By Alastair Mclntosh
After years of angst-ridden hand-wringing, Alastair Mclntosh has radically cut his domestic carbon footprint by combining a wood stove, solar panels and an air-to-air heat pump. Here, Alastair describes how he did it – and for the technically-minded reader, the numbers in the text link to further information on his website.
In 2008, Birlinn published my book, Hell and High Water: Climate Change, Hope and the Human Condition. But my own domestic carbon footprint was frustrating. Now, thanks to technological advance and crashing prices, we are managing to reduce our emissions by well over half.
My love affair with renewables started in the 1970s, when I was volunteering in Papua New Guinea. A French priest, Fr Jean Besson, had been killed on his own airstrip before finishing a 20 kW village hydro system. With a crofting background from the Hebrides, I was given the young man’s dream commission of getting it going. I will never forget the day we opened up the sluice and let the river flow ten metres down into a huge Francis turbine. As the flywheel hummed up to speed, I threw the switch and to the sheer astonishment of us all, the village lights came on in utter silence – without the usual diesel-guzzling racket.
Our carbon footprint Since those halcyon days, I have had to make do with the hum of my bicycle dynamo. Verene and I moved to Glasgow’s Govan in 2004 to be with the GalGael Trust of which I am a founding director. Our single sop to renewables has been our low-emissions wood stove, fed from skip-diving and GalGael offcuts. Now that has changed, but first, let me establish our baseline domestic energy demand.
We live in a hard-to-insulate Victorian end-terrace house, both working from home and typically spot-heating three rooms plus the utility areas to around 20" C. Partial external wall insulation would be nice but I have not yet managed to find a reliably certified company that can affordably take on such a one-off job – they all say "we might be getting into that next year"! Averaged over the past four years, our consumption has been 4,036 kWh (or units) of electricity per annum and 17,942 kWh (or units) of gas (converted at 11.3 kWh per nr). The standard figures used for the carbon intensitivity of grid electricity in the UK is 0.525 kg/unit and that of natural gas, 0.184 kg/unit. On that basis, our annual carbon (COJ footprint is 5.4 tonnes, for which, all up, we pay £l,285/annum or £107/month.
The heat and light for a typical Scottish home of 2.18 occupants releases 5.8 tonnes of CO,/annum. How come we are just around the average when we work from home, often with meetings going on in the house, when the average is based on many people going out to work and perhaps not heating their homes during the day? It is the stove that cuts a tonne off the higher amount that our figures would otherwise show. Mind you, like all ecology it’s a niche solution. If everyone in Govan went skip-diving we’d be having skip wars!
Trie great cosmic woodpile So, bring on what I now call The Great Cosmic Woodpile in the Sky – this magazine, remember, was originally called The Tree Planter’s Guide to the Galaxyl The price of solar voltaic panels has crashed recently and so, in January 2013, we put in a decent-spec 4 kW system for just £5,000 fully installed. That sort of price – even if a bit higher in rural areas – democratises solar. You can tell your neighbours that it is no more than a second-hand car.
Our system, which is on a southsouthwest 35° tilted roof, should produce a little over 3,000 units/annum. From January to June it has over-performed by 14 per cent – but hold on, this has been a cold but sunny spring in Glasgow, with sunshine hours 20 per cent above average. Truth is, we are running 6 per cent below par, which is probably largely due to shading from our wood stove’s chimney!
Assuming we produce 3,000 units/year on average, then three-quarters of our previous electricity demand will simply fall off the roof. Our feedin-tariff (FIT) – both "generation" and "export" combined – is 17.69 pence/unit. That offers some £530 a year, index-linked and tax-free, for the next 20 years. In addition, the FIT system assumes that you use half of what you produce yourself and only export the balance to the grid. If we can in fact use that in sync with when we are producing it, we will save a further £196/annum on our electricity bills. All up, it nods towards an investment payback period of just seven years. The internal rate of return is at least three times better than current life assurance annuity rates.
But here’s the catch. Most frugal households cannot sustain using half of the solar power that a 4 kW system produces. Our home baseload is only about 200 watts. Even in fairly heavy cloud, the panels provide that and so when the sun comes out, and our output shoots to well over 3 kW, we are giving away freebies to the grid except when the kettle’s on. We buy electricity from the grid at 13.07 pence/unit but only receive a notional 4.5 pence/unit for selling 50 per cent of our production back to it. A good deal for our utility provider! Our previous carbon footprint for gas and electricity was 5.4 tonnes. Producing 3,000 units of clean green juice cuts that by 1.6 tonnes to 3.8 tonnes. I therefore had a question. Could we raise efficiency – on both costs and carbon – by using our solar production more fully without being wasteful?
Air-source heat pump I saw my first air-source heat pump (ASHP) at last year’s Mull Renewables Fair. They operate like a fridge or air conditioner running in reverse. Instead of using high-grade (flexible) electrical energy as a direct means of heating, they use it intelligently, to move ambient heat around. I reasoned that quite often Verene and I would have the central heating off, but each have a wee 500 watt heater to keep the chill at bay. That kilowatt equates to what our solar can produce even just in bright cloud, so could we use an ASHP instead, and heat the house effectively?
New Guinea had been kind to us. We’d had a slice of well-paid work from West Papua on the Indonesian side and so for once could afford an experiment. Costing just under £2,000, we installed a Worcester Bosch Greensource ASHP that typically runs at 1.2 kW and converts it to around 5 kW of heat. It is like a perpetual motion machine come true. A fishbox-sized unit sits in our garden making a gentle whooshing sound from its fan. An ASHP can be a ‘permitted’ planning development but you should check out your situation as you may need permission. It uses refrigerant gases, transfers atmospheric heat (even when it’s freezing) to an indoor blower above the front door that we call "Puffer". From there, it wafts up to our offices and wherever doors are open.
Puffer also ionises and filters the air, removing dust and spores, and in summer can dehumidify and cool. We will still need the mains gas in winter, but since the start of April have only used it to heat water and that’s with a mean temperature in Govan, according to Met Office figures, of only 7.0° C (more like the norm for March than April), just 7.5° in May and 14.0° in June. Our previous energy costs for April-June were £286. This year they were only £142, less the solar FIT repayments of £243, yielding a net profit of £101. Meanwhile, our carbon footprint fell by 81 per cent, after allowing for carbon credit on what we exported to the grid. If that’s not green magic, tell me what is!
The NUB of energy policy While the FIT has been a good policy to kick-start green energy, we live in an area of fuel poverty and don’t like being subsided by neighbours. I therefore have a policy proposal. When our panels were first installed, our olde-worlde meter with its rotating dial ran backwards and unwound when exporting. Scottish Hydro had to change it. But what a wonderful system, because this measured our net usage. I suggest: why not abolish the FIT system and legislate that energy providers must buy back at the same price as they sell?
I would call this the NUB – the Net Usage Basis. Our electricity provider would let the grid be optimally used as a battery or bank. We would wash their dirty energy clean, and do so mostly around lunchtime when wholesale spot prices are at a peak. On such a NUB I calculate that, even using discounted cash flows, we are now touching the holy grail of grid parity for domestic systems. For sure, it’s niche. It all depends on your roof. Yet niche by niche new ecosystems grow.
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