Carbon Feet -emissions by microgeneration and other renewables

Iain Fraser posted a response to my post of 10^th March asking me to cite my sources for my figures. It is a perfectly reasonable request but as I was away from my office it was hard for me to do that. Mr Fraser may think that I have a bee in my bonnet about biomass but I would disagree. I always try to provide accurate information.

The purpose of my weblog is to help generate ideas about the environment and writing a post each day helps me formulate my own ideas.  If biomass was a silver bullet to slay the beast of climate change I would be delighted. It is not, and has various disadvantages, the most important one being, in my present state of thinking, the problems biomass burning will cause to human health. 

I got my figures (apart for those for Genersys solar thermal) from the Parliamentary Office of Science and technology. You can see their sources at the following address: http://www.parliament.uk/documents/upload/postpn268.pdf  

Some of their figures came from studies which were carried out for it by the University of Northumberland. The Parliamentary Office of Science and Technology were only at that stage concerned with electricity generation – we have always had an electricity policy in this country rather than a heat policy – and there were no figures for solar heat. 

I have compared the figures on the basis of a kilowatt hour of energy, without restricting matters to electricity. I do not think that this is an unfair comparison because with the Genersys solar thermal we are, as you will see from the methodology, only measuring useful heat, whereas not all electricity generated is useful and some of it gets lost on the transmission process. 

We contacted the University to ask for the methodology that they applied but that request was never answered. That meant that we had to carry out our own thermal solar study using Genersys collectors because every collector must have a different carbon cost, although I imagine that they will all be broadly in line with ours. 

It is important to reduce the carbon footprint for each product to as small as possible even if they like Genersys solar panels do save huge quantities of carbon over their lifetime.  The precise carbon footprint varies according to the source of the raw materials and the processing plants that turn the raw materials into finished material appropriate for manufacturing into solar panels.

Some aluminium processing plants use energy produced by coal or oil; others use hydro electricity or nuclear power. The same applies to glass and copper.  Each source leaves a different carbon footprint so in our figures we have used average carbon emissions over the whole of each industry:- 

Aluminium: We use aluminium for the panel trays and for the profiles which make up the frames. The aluminium we use for each panel and frame uses we calculate 442.6 kWh of energy. 

Copper: We use copper for the meandering heat pipe and for the sensor pockets. We calculate the copper we use needs 108.4 kWh of energy to produce it. 

Glass: We use special glass and this makes up most of the weight of each panel. It uses around 100.9 kWh of energy. Insulation: This uses around 19.4 kWh for each panel. 

Selective Coating: our own specifically made selective coating needs around 45kWh of energy to make it. Additional material: we calculate that additional material uses 6.8KWh of energy 

Manufacturing: We try to keep the manufacturing process as efficient as possible and by not using welding and employing our folding technology we have managed to keep manufacturing energy costs to around 45 kWh per panel. 

Overall the energy usage per panel is 723.3 kWh which translates into 137 kilograms of carbon dioxide per panel using normal energy mix assumptions.  In the UK most homes employ two panel systems which generally mean each system “costs” 374 kilograms of carbon dioxide for the panels and frames and for such things as transport, the peripherals (pumps station, controller pressure vessel and piping) probably add another 200 to 250 kilograms of carbon dioxide.

This means that a UK default two panel system has left on average a carbon footprint of 600 kilograms of carbon dioxide. An average two panel systems in the UK where the system displaces gas burnt by a condensing boiler as the fossil fuel a Genersys solar system saves about 500 kilograms of carbon dioxide each year, so the solar system “pays” for itself in less than 15 months.  

If the system displaces oil as the fossil fuel it will save around 800 kilograms of carbon dioxide each year and will “pay for itself in nine months.

If the Genersys solar system displaces electricity it will displace around 1300 kilograms of carbon dioxide in a year “paying” for itself in about five months. 

Over a thirty five year lifetime depending on the fossil fuel displaced (and the kind of water heating system being used) two panel Genersys solar systems in the UK will provide net carbon dioxide savings as follows:- 

• Natural Gas   16,900 kilograms
• Oil                   27,400 kilograms
• Electricity       44,900 kilograms

 All this translates (if we have done our mathematics correctly) to less than 10 grams per kilowatt hour. The Parliamentary Office for Science and Technology rightly says that no source of electricity generation is carbon free and I would expand their statement – no source of energy is carbon free.

It is clear that the term “Zero Carbon Home” is a scientific nonsense. Low Carbon Home would reflect the reality but calling a home zero carbon might well get you in trouble with misrepresentation and consumer legislation.  

I said at the start of this post that it is important to be accurate with information. If we are not we will only fool ourselves, not the laws of physics or nature, which will inexorably come to their own conclusions regardless of what we claim.