A very short guide to home renewable energy


Are you thinking of installing some kind of renewable energy for your home? If so, I offer this guide. 

These are the main ways of generating energy from renewable sources. All of them have their pluses and minuses. None of these forms of energy supply 100% of the energy that you need at all times, and they do need back up. All forms suffer from some kind of intermittency. That should not stop you considering one of these which will give you clean energy some of the time. Continue reading

Passing the hat round for the Co-Op

Unfortunately in their search for the Holy Grail politicians have in turn adopted various environmentally produced energy technologies. The first to be adopted and then discarded were photovoltaic cells.

It is hard to explain photovoltaics in layman’s terms and can be quite hard to understand so if you don’t want to read the technical stuff, skip the next two paragraphs.

PV started with Becquerel in 1839 and then Willoughby Smith, Hertz, Max Planck and even Einstein found that light shining on a metal can create energy proportional to the frequency of the light. When the light strikes the metal, the energy from the photons is transferred to electrons in the metal. If that energy is greater than what is required to overcome the forces which keep the electron in the metal, the energy will be released. The result is that light with a high enough frequency can knock electrons out of a metal surface.

The displaced electrons are freed to move about, forming a “conduction band”, and a hole is left behind where the freed electrons used to be. They are “harnessed” by the use of semiconductors with different electrical characteristics so that an electric field is generated. This field causes positive and negative charges to move in opposite directions, thus creating electric current. I hope that I have explained this reasonably accurately and if I have not no doubt someone out there will let me know.

Anyway when you understand that you use light to generate electricity you will understand how attractive this must seem to politicians looking for the Holy Grail; they thought they had found it, with these photovoltaic cells, which have been confusing called solar panels but now are know as “PV”.

PV superficially sounds much more impressive than using light to generate heat (which is what real solar panels do), because electricity is often associated in people’s mind with energy and they tend to ignore heat. That is a shame because you can live without electricity – it will be hard but people have done it for tens of thousands of years, but people have lived with heat and in most places would die in winter without heat.  

In Manchester, Europe’s largest vertical photovoltaic project was installed at the Co-operative Insurance Society Tower. This project was subsided by the state (that is you and me, folks) to the tune of just over £1 million, although what business the government has in subsiding a commercial organisation like the Co-op (turnover £9.4 billion) is entirely beyond me. Interestingly enough the amount given by the taxpayer to the Co-Op was virtually the maximum that is permitted to be given for a project of this nature under the European Community’s State Aid rules.

PV re-cladding was predicted to result in a rated power output of between 250 and 350 kWp and was expected to meet only 10% of the building electricity requirements by generating it is hoped 180MWh electricity per year. I have not been able to find out any data yet as to whether the project met its expectations. 

Governments all over the world provided subsidies for PV because the environmental cost of electricity generated is very high, although if you look at the carbon cost in making the PV and spread that over the life time of the PV it is much more carbon productive than first thought. They hope to attract investment in building PV cell manufacturing plants to create jobs (although when they do they frequently have to subsidise the establishment of a factory).

Governments have listened to multi national companies that have invested in PV technology. Mr Blair took advice from Lord Browne who ran BP, one of the most carbon producing businesses on earth. BP invested in PV, and claimed a “green” sustainable image as a result. Mr Blair bought the sales pitch and set up a very generous PV grants system.

The Co-op was not the only company or person that was able to access these large grants. At one time PV attracted a grant of 50% of the cost, which meant that if you were building your own house, provided you could access the grant, and you wanted to have a PV roof, the taxpayer would pay half of the cost up to £15,000.  This struck me as wrong; someone with the cash to build their own home should not get half a PV roof paid for by the state.

This has now been changed; the PV grants are still very generous compared with other technologies – around £2,500 – but the drop in grants has affected the PV market, causing it to decline. Of course the smaller businesses that sell and install PV are worse affected; somehow the multi-nationals will survive a down turn in a business that does not even represent 1% of their portfolio.

The problem with efficient photovoltaics is that they use broad spectrum light whereas they would operate more efficiently at only at specific narrow part of the light spectrum. Anything outside this narrow part of the spectrum cannot be converted to electricity. Also their efficiency drops as they become older, and in very hot weather. At freezing point silicon has a maximum theoretical efficiency of 24%; at room temperature this drops to 12%. The laws of physics mean that photovoltaic cells decrease in efficiency as the temperature of the cell increases. 

The best and most efficient use of PV is when it eliminates the need for batteries in many calculators. Many places have now installed photovoltaic cells to operate parking meters and some street lighting, but this really makes no sense environmentally.

Photovoltaics really become effective in “off-grid” situations. In places where the cost of bringing power lines or building generating plants is expensive, the PV offers a good solution which is both environmentally friendly and cost effective. It makes no sense to me to install PV in Manchester at public expense. If the Co-op wants to make an environmental statement for reasons of good corporate governance then I applaud them, but let them do that with their own money.

In the real world £1 million would provide free solar water heating systems for three hundred poor people and that would save more energy and more carbon dioxide emissions and save the poor some money.