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Renewable energy sources more imagined than real

Renewable energy sources more imagined than real

We are often attracted to renewable sources as there seems an almost unlimited amount of potential energy available if only we can get our hands on it. We often we hear of proponents of renewable sources coming up with fantastic pools of resource at high efficiencies that we can access at no (apparent) cost. Take for example tidal energy. The amount of energy in tidal power generated by the gravitational energy of (mainly) the moon comes to a total of about 3.5 terawatt hours (1012) which seems at first sight a great deal of energy but is in fact only 20% of the global demand in total. Furthermore there are twenty places in the world where tidal flow exceeds the around 1.5 meters per sec at peak flow which would be sufficient to drive a turbine farm which means the actual accessible power is very small (and periodic) at around 200 gigawatt’s (109) of available energy – or around one thousandth of the available energy supply. So there is in principle a large amount of energy there but unfortunately we are unable to access it in any reasonable way.
I was drawn to these interesting facts in the New Scientist after a meeting where it was proposed to me that if we could all have Sterling engines installed in our homes and drive them with natural gas instead of the big power generators doing it for us we could enjoy 95% efficiencies in conversion as against the around 30% the best generators achieve. However this was a mistake and would breach the laws of thermo dynamics if it were true as a typical sterling engine has a thermal efficiency of between 20 to 30% which is nicely comparable to a car engine but not I am afraid in the 90% range. Given that most Sterling engines require exotic materials and tend to be quite expensive I doubt this is a starter in cost terms alone – although up to 150 or so KW that might be in the running for a home generator utilising waste head from the house say in summer (acting as a air conditioner).

As so often is the case spokespeople appear every so often extolling the virtues of a green half baked idea when the engineering aspects almost always rules out getting anywhere near such stratospheric benefits. We have only to look at wind power, many of the turbines operate as miserable efficiencies and blight the landscape for miles around. What is needed is a bit more evidence based evaluation and a little less hype and hope.

Roy

Planning a Green Christmas

Planning a Green Christmas

The song tells of a white Christmas, but that refers to the weather and the Christmasy atmosphere that snow can bring. Planning for a green Christmas is all about being environmentally active and aware while saving money as well. In times of economic uncertainty that must surely be a good thing. And of course, if the weather brings a little bit of white covering too, then that makes a green Christmas perfect!

Exchanging gifts is a common practice at Christmas, and this is an excellent place to start our green Christmas habits. The gift wrapping paper sold in stores is usually not recyclable. Most of it is immediately thrown away to end up in landfills. This makes gift wrapping with store-bought paper expensive and very unfriendly to the planet – not what we want for a green Christmas.

A much better alternative, and one that close relatives will appreciate, is to use your children’s artwork to wrap gifts. You could also use your children’s comic books, or the comic sections of newspapers as a bright and colorful alternative, thereby recycling old paper. You can explain to the recipient of the gift in a positive way why you are doing this and perhaps make them feel guilty for not having a green Christmas as well.

It has been calculated by the Sierra Club, America’s oldest and largest environmental organization, that if every family in the country gift wrapped just three gifts by recycling existing paper they already have, the paper saved would be enough to cover 45,000 football fields. Now, that’s a green Christmas and a whole lot of trees saved too!

If you plan to hang a wreath on your front door. consider making one yourself. It’s easy and very environmentally friendly – and you’ll save money too. Go into the forest, or even a nearby park, and find evergreen branches and dried twigs. These can be wrapped in a circular fashion with cranberries strung together to add a splash of bright color. You’ll surprise yourself at how good you are, it won’t cost you anything but a little time, and the materials are all fully biodegradable. Your green Christmas can’t get much better than that.

There are many more things you can do to make this a green Christmas. Consider making your own cards, for example. Use your children’s artwork again – it’s perfect for this and grandparent will love it. You can use LED lights on your tree (which should be a real one that can be planted out later) and you will save 90% on your green Christmas electricity bill. If you start thinking about it I’m sure you will come up with other great ideas for a green Christmas.