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Page history last edited by wilbo666 7 years ago



Random page for thoughts regarding self sufficient / sustainable power.


Energy Generation

Some options for energy generation.



A number of methods exist for harnessing the power of solar,




Conventional method of generating electricity directly from the sun using 'solar panels'.


General efficiency of around 13 to 15% (1m² will generate ~150W).



Details regarding this option should be investigated.


Concentrated Photovoltaic

Mirrors etc used to focus more sunlight onto Photovoltaic (PV) cells.


Details regarding this increase to efficiency could be investigated.


Concentrated Solar Power

Light from the sun is concentrated (usually via mirrors or lenses) to heat a liquid (usually oil or a molten salt).  The heated liquid is usually used to boil water and drive a steam turbine or Sterling engine to generate electricity.


Sandia National Laboratories National Solar Thermal Test Facility produces as much as 25 kW of electricity, with a conversion efficiency of 31.25% from a single solar dish-Stirling engine system.


Details regarding this option should be investigated.



Limited to suitable location.




Temperature difference between Environment:


Difference Between Ground Temperature and Air

Options for this included via the thermoelectric effect (i.e. Peltiers) or Sterling engine.



Peltiers have poor efficiency (~10%)


Peltier costs from www.ebay.com.au as of 16/08/2012:

60W, $3.94

136.8W, $5.32

154W, $5.98


Details regarding this option should be investigated.


Sterling Engine

A Stirling engine is a heat difference engine.  Need to determine if this is a practical option.


Details regarding this option should be investigated.



Radioisotope Thermoelectric Generator (RTG)

The heat from radioactive decay of a radioactive material is used to generate heat which is converted to electrical energy via the Thermoelectric effect.


RTG systems have poor efficiencies (~3 to 7%) and the radioactive material required makes these poorly suited for individuals.








Solar Efficiency

At the top of the atmosphere there is approximately 13666 W/m² of energy available from the Sun.  This figure takes into account the whole solar radiation spectrum.

After travelling through the atmosphere however this figure is reduced to ~1000 W/m². (To be confirmed).


When using solar energy there are a number of factors that should be considered that can effect the energy produced, these include

  • Orientation to the sun


                    Image taken from: http://www.yourhome.gov.au/technical/fs67.html 

  • Temperature (PV cells produce less energy as their temperature increases) 



Efficiencies for solar cells are quoted at STC or PTC

  • STC = Solar irradiance of 1000 W/m², solar spectrum, airmass of 1.5, cell temperature of 25°C.
  • PTC = Solar irradiance of 1000 W/m², solar spectrum, airmass of 1.5, ambient temperature of 20°C, wind speed of 1m/sec (PTC stands for "PV USA Test Conditions").



Energy Storage



Initially thoughts are that batteries are expensive and have fixed service life (wear out) which I find undesirable.


However batteries may be an acceptable solution.


Details regarding this option should be investigated.



Compressed Air

Store excess electrical energy as compressed air by compressing air with an electric compressor. 

The potential energy of the compressed air could be released to power a turbine to generate electricity.


Details regarding this option should be investigated.




Generated via electrolysis of water to generate Hydrogen. 

Hydrogen could be converted to electricity via fuel cell/s, by being burnt to heat water to power a steam turbine or by driving an hydrogen engine to power a generator.



Details regarding this option should be investigated.




Potential energy could be stored as heat such as in oil or molten salt.


Details regarding this option could be investigated.



Pumped Water Storage

Water can be pumped to a height with excess electrical energy. 

The potential energy of the water could be released to power a generator (normally the pump being driven reverse).


Limited to a large extent by suitable location.



Things to Research

  • How is solar panel efficiency measured?
  • Batteries (Cost, capacity required, physical size & weight, lifetime, etc)
  • Compressed air as an energy storage method (energy density, efficiency, method to convert to electricity)
  • Hydrogen (production, storage, etc)
  • Ground temperature vs air temperature (real data, heat transfer to / from ground)
  • If Peltiers would be viable for electricity generation (real world power output)





A4_4 An RTG Powered Home.pdf


soil temp.pdf









http://www.phys.unsw.edu.au/~map/weather/barometer/soil_temperature_profile.html (Ground Temperature)








http://www.acrim.com/  (Total Solar Irradiance (TSI) Monitoring)








AS4509 Stand-alone Power Systems (Australian Standard)




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