Lever Long “Give me a lever long enough and a fulcrum on which to place it, and I shall move the world” Archimedes   Surviving the Twenty-first Century   Add this page to my Favorites

 

 

This domain name could be yours, contact (You must include the words “From Web” in the subject, to pass our spam-filters): 

 

Mankind may well have had its golden years, and the future one of climate change, fuel and food shortages.

 

Current world population (estimated): . 

 

This web site is intended to share ideas about things we can all do to survive the Twenty-first Century.

 

Click here for solar panel ideas      Click here for wind turbine ideas

 

Share your ideas with others: have your credited ideas published free on this web site, contact (You must include the words “From Web” in the subject, to pass our spam-filters)

 

Have a look at “The Story of Stuff” web site – it’ll have you thinking a little more about what we do and where we are going: http://www.storyofstuff.com/

 

For information about the Transition Town initiative go to http://www.transitiontowns.org/

 

 

 

Solar Panels come in two main types: Photovoltaic (solar energy collected as an electric current, usually stored in a battery) and Solar-thermal (solar energy collected as heat, usually stored in water).

 

Solar-Thermal: All-to-often manufactures of solar panels will quote the peak output for their panels and shy clear of stating the average output. Under the most favourable conditions each square metre of panel will collect nearly 1000 watts of power when the panel is directly pointing towards the sun in a completely clear sky. This peak value of power should not be confused with the average energy that each square metre of panel can generate: in the UK the average power (24-hours, 7-days, 365-days per year average) from the sun is only around 100 Watts per square metre of panel, this is equal to 2.4kWh of energy per day. During the summer months the daily average is higher than the winter months: around 4.5kWh per day in June compared with 0.5kWh per day in January, but over the year the overall average is around 2.4kWh per day for each square metre of solar panel in the UK. But don’t be too depressed, because 2.4kWh per day is equal to nearly £0.30 (2008 prices) worth of electricity equivalent energy per day, every day. And a two square metre solar panel will produce nearly £0.60 worth of electricity equivalent energy per day – that’s over £200 per year, and therefore worth looking seriously at.  You can check your own geographical location for its average isolation (how much sun power there is per square metre) by going to this NASA web site.

 

When calculating the savings that can be made by installing a solar panel, remember that electricity is around twice the price of gas or oil: at 2008 prices 1kWh of electricity costs approximately £0.12, whilst 1kWh of gas costs around £0.06. The effect of this difference is to double the payback time of installing a solar panel: each square metre of solar panel will collect around £100 worth of equivalent electric energy, but only around £50 worth of gas equivalent energy.

 

Beware of the cost of installing solar panels: if a two square metre panel costs, say, £2000 (and that is a low-end price for 2008) to install then it will take between 10 and 20-years to recover the costs! With this in mind I set about a home-build solar panel with material costs of around £400. However if building your own is not your thing, and you decide to opt for a commercial solar-thermal system, then remember the minimum payback time (at 2008 prices) is calculated by multiplying the area of the panel in square metres by 100, and dividing the result into the total price of the solar panel. For example if a 2.5 square metre solar panel is on offer at £3450 fitted, then the minimum payback time will be: 100 times 2.5 = 250, and this is divided into the price; £3450 divided by 250 = 13.8-years minimum time to payback your investment (and if you use gas or oil, it could take as long as 28-years!).

 

 

Inexpensive Solar Panel For the handyman (or woman) to make

 

 

Photovoltaic: When comparing the cost of installing a solar-thermal panel with that of a photovoltaic panel, it is immediately apparent that the technology of photovoltaic solar power harvesting has still a long way to go. Semiconductor development is ongoing, and great strides have been made in improving the conversion efficiency and simplifying production to bring down the cost of utilising photovoltaic technology.

 

A good solar-cell (the basic semiconductor unit that photovoltaic systems use) will convert more than 30% of the sunlight that falls upon it and cost around £1 per square centimetre (very expensive, and mainly used to power spacecraft); but even much cheaper solar-cells giving efficiency of around 10% and costing around £0.07 per square centimetre is never going to be as cost effective as solar-thermal. A quick calculation would show that one square metre of 10% efficient photovoltaic solar panel would cost around £700 but would only ever be able to harvest 10% of the solar energy falling on it: that’s a mere 10 watts; it would take over 60-years to recover the cost!

 

The BIG advantage of photovoltaic is that it does produce electricity directly from the sun, unlike solar-thermal that is dependant upon an external electricity supply. A good combination would be a small photovoltaic and a much larger solar-thermal: the photovoltaic could be used to power the water pump that drives the solar-thermal panel. However, much beyond this conjugation photovoltaic has still a very long way to go before it is even remotely viable for use in a domestic solar panel.

 

 

 

Wind Turbines come in a variety of sizes and designs. And if you think I was harsh discussing the cost of solar panels, then for wind power I’m going to be absolutely damming!

 

Unlike solar, calculating the power that can be harvested from the wind is far from easy. Whereas the collecting capacity of a solar panel is simply proportional to its area (double the area doubles the power), wind is a much more involved calculation. If you compare two wind turbines one of which has twice the blade radius of the other, then for the same wind speed the larger turbine will produce 4-times the power of the smaller turbine: there is a square-law relationship that applies to wind turbines of differing blade size. And as for wind speed: for any particular turbine if you double the wind speed you get 8-times the power: there is a cube-law relationship that applies to a wind turbine exposed to various wind speeds.

 

A cheap end wind turbine, one that you have to install yourself, will have something like a 1 metre diameter turbine and cost around £500 (2008 prices). The output power of the turbine will be around 100 watts at a wind speed of 19 to 24 mile per hour (force-5 on the Beaufort Scale – about the level where small trees will sway in the wind). And, as with calculating the average insolation for solar panels, it is the average wind speed that should be taken into account when working-out the payback time for investing in a wind turbine. The annual average wind speed for a “windy” part of the UK is only around 16 mph, and from the cube-law relationship you can calculate that the average power from the turbine will be only around 41 watts. This power equates to around 0.98kWh of energy per day; less than £0.12 of electricity equivalent per day at 2008 prices. Therefore the payback time for just the material cost of the turbine (installation will cost possibly more than the turbine!) will be around 12-years at electricity prices, or 24-years at gas equivalent prices – and that’s just for the turbine, you can probably double (or even treble) the payback time if you include the cost for installing the turbine!

 

It makes absolutely no sense to install a small wind turbine: it only ever becomes a cost effective green-energy source when the turbines are on an industrial scale; the square-law relationship favours big wind turbines.